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  • 1.
    Baker, A.
    et al.
    University of Stellenbosch, South Africa .
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Blaauw, M.
    Queens University of Belfast, North Ireland .
    Roychoudhury, A.N.
    University of Stellenbosch, South Africa .
    Geochemical records of palaeoenvironmental controls on peat forming processes in the Mfabeni peatland, Kwazulu Natal, South Africa since the Late Pleistocene2014Inngår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 395, s. 95-106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Mfabeni peatland is the only known sub-tropical coastal fen that transcends the Last Glacial Maximum (LGM). This ca. 10 m thick peat sequence provides a continuous sedimentation record spanning from the late Pleistocene to present (basal age c. 47 kcal yr BP). We investigated the paleaeoenvironmental controls on peat formation and organic matter source input at the Mfabeni fen by: 1) exploring geochemical records (mass accumulation rate, total organic carbon, carbon accumulation rate, delta C-13, delta N-15 and C/N ratio) to delineate primary production, organic matter source input, preservation and diagenetic processes, and 2) employ these geochemical signatures to reconstruct the palaeoenvironmental conditions and prevailing climate that drove carbon accumulation in the peatland. We established that the Mfabeni peat sediments have undergone minimal diagenetic alteration. The peat sequence was divided into 5 linear sedimentation rate (LSR) stages indicating distinct changes in climate and hydrological conditions: ISR stage 1 (c. 47 to c. 32.2 kcal yr BP): predominantly cool and wet climate with C4 plant assemblages, interrupted by two short warming events. LSR stage 2 (c. 32.2 to c. 27.6 kcal yr BP): dry and windy climate followed by a brief warm and wet period with increased C4 sedge swamp vegetation. LSR stage 3 (c. 27.6 to c. 20.3 kcal yr BP): initial cool and wet period with prevailing C4 sedge plant assemblage until c. 23 kcal yr BP; then an abrupt change to dry and cool glacial conditions and steady increases in C3 grasses. LSR stage 4 (c. 203 to c. 10.4 kcal yr BP): continuation of cool and dry conditions and strong 0 grassland signature until c. 15 kcal yr BP, after which precipitation increases. LSR stage 5 (c. 10.4 kcal yr BP to present): characterised by extreme fluctuations between pervasive wet and warm to cool interglacial conditions with intermittent abrupt millennial-scale cooling/drying events and oscillations between C3 and C4 plant assemblages. In this study we reconstructed a high-resolution record of local hydrology, bulk plant assemblage and inferred climate since the Late Pleistocene, which suggest an anti-phase link between Southern African and the Northern Hemisphere, most notably during Heinrich (5 to 2) and Younger Dryas events.

  • 2.
    Baker, Andrea
    et al.
    Department of Earth Sciences, Stellenbosch University, Stellenbosch, South Africa.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Roychoudhury, Alakendra N
    Department of Earth Sciences, Stellenbosch University, Stellenbosch, South Africa.
    Biomarker records of palaeoenvironmental variations in subtropical Southern Africa since the late Pleistocene: Evidences from a coastal peatland2016Inngår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 451, nr 1, s. 1-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Southern Africa's unique global position has given rise to a dynamic climate influenced by large sea surface temperature gradients and seasonal fluctuations in the Inter Tropical Convergence Zone. Due to the semi-arid climate of the region, terrestrial palaeorecords are rare and our understanding of the long-term sensitivity of Southern African terrestrial ecosystems to climatic drivers is ambiguous. A 810 cm continuous peat core was extracted from the Mfabeni peatland with a 14C basal age of c. 47 thousand years calibrated before present (kcal yr BP), positioning it as one of the oldest known sub-tropical coastal peatlands in Southern Africa. This peat core provides an opportunity to investigate palaeoenvironmental changes in subtropical Southern Africa since the late Pleistocene. Biomarker (n-alkane, n-alkanoic acid and n-alkanol) analysis, in conjunction with previously published bulk geochemical data, was employed to reconstruct organic matter (OM) sources, rates of OM remineralisation and peatland hydrology. Our results showed that the principal OM source into the peatland was emergent and terrestrial plants with exception of shallow lake conditions when submerged macrophytes dominated (c. 44.5–42.6, 29.7, 26.1–23.1, 16.7–7.1 and 2.2 kcal yr BP). n-Alkane proxies suggest that local plant assemblages were predominantly influenced by peatland hydrology. By incorporating temperature sensitive n-alkanoic acid and n-alkanol proxies, it was possible to disentangle the local temperature and precipitation changes. We report large variations in precipitation intensities, but subdued temperature fluctuations during the late Pleistocene. The Holocene period was characterised by overall elevated temperatures and precipitation compared to the preceding glacial period, interspersed with a millennial scale cooling event. A close link between the Mfabeni archive and adjacent Indian Ocean marine core records was observed, suggesting the regional ocean surface temperatures to be the dominant climate driver in this region since the late Pleistocene.

  • 3.
    Baskar, Sushmitha
    et al.
    1Department of Environmental Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar, Haryana, India.
    Baskar, Ramanathan
    1Department of Environmental Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar, Haryana, India.
    Routh, Joyanto
    Department of Earth Sciences, IISER-Kolkata, Mohanpur, India / Department of Natural Sciences and Technology, MTM, Örebro University, Örebro, Sweden.
    Biogenic evidences of moonmilk deposition in the Mawmluh cave, Meghalaya, India2011Inngår i: Geomicrobiology Journal, ISSN 0149-0451, E-ISSN 1521-0529, Vol. 28, nr 3, s. 252-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Moonmilk, a microcrystalline secondary cave deposit, actively forms on the floor of Krem Mawmluh - a limestone cave in Meghalaya, Northeastern India. Due to the abundance of micrite and calcified microbial filaments, we hypothesize that these deposits form as a result of ongoing microbial interactions. Consistent with this idea, we report electron microscopic and microbiological evidences for the biological origin of moonmilk in Krem Mawmluh. Scanning electron microscopy indicated abundant calcified microbial filaments, needle calcite, fibre calcites (micro-fibre and nano-fibre calcite crystals), biofilm and microbial filaments in the moonmilk. The total viable culturable microbes showed high population densities for microbes in the moonmilk and moonmilk pool waters. In vitro culture experiments, confirmed the capability of many of the isolated strains to precipitate calcite and some of the identified isolates belonged to the Bacillus sp. and Actinomycetes. These results clearly support the biogenic nature of the deposits.

  • 4.
    Baskar, Sushmitha
    et al.
    Indira Gandhi National Open University, India.
    Baskar, Ramanathan
    Guru Jambheshawar University of Science and Technology, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Speleothems from Sahastradhara Caves in Siwalik Himalaya, India: Possible Biogenic Inputs2014Inngår i: Geomicrobiology Journal, ISSN 0149-0451, E-ISSN 1521-0529, Vol. 31, nr 8, s. 664-681Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stalactites and moonmilk from Sahastradhara caves in Siwalik Himalayas were studied to understand the role of microbes in their genesis. Fourier spectroscopy in the moonmilk indicates a complex milieu of organic compounds that is unusual for inorganic formations. Stable C and O isotopes show trends in the moonmilk and stalactite, which suggest biogenic input; the geochemical inference is consistent with evidence from microscopy and laboratory-based microbial cultures. Light microscopy of moonmilk samples show the presence of a number of microbial forms similar to Cyanobacteria, and scanning electron microscope (SEM) images show microbial structures similar to Spirulina. The total number of microbial cells using SYBR Gold is 6.5 x 10(5) cells, g sed(-1) in moonmilk and 3.2 x 10(5) cells, g sed(-1) in stalactites. FISH indicates approximately 3.5 x 10(5) cells, g sed(-1) in moonmilk and 2 x 10(5) cells, g sed(-1) in stalactites. SEM images of the moonmilk indicate a large network of microbial filaments along with minerals, which are identified as calcite based on their x-ray diffraction pattern. In vitro laboratory cultures with pure monogenic strains isolated from the moonmilk and stalactites raise pH in the medium, which facilitate calcite precipitation. The mineral precipitating isolates were identified as: Bacillus pumilis, B. cereus, B. anthracis, B. lentus, B. sphaericus, B. circulans and Actinomycetes. The Sahastradhara moonmilk and statactites are colonized by a diverse microbial community and the isolated bacterial strains induce biomineralization on different nutrient media, supporting their biogenic origin.

  • 5.
    Bhattacharya, Aparajita
    et al.
    Department of Geology and Geochemistry, Stockholm University, 10691 Stockholm, Sweden.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, 10691 Stockholm, Sweden.
    Jacks, Gunnar
    Department of Land and Water Resources Engineering, KTH, 10044 Stockholm, Sweden.
    Bhattacharya, Prosun
    Department of Land and Water Resources Engineering, KTH, 10044 Stockholm, Sweden.
    Morth, Magnus
    Department of Geology and Geochemistry, Stockholm University, 10691 Stockholm, Sweden.
    Environmental assessment of abandoned mine tailings in Adak, Vasterbotten district (northern Sweden)2006Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 21, nr 10, s. 1760-1780Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sulfide-rich mine tailings in Adak that are exposed to weathering cause acid mine drainage characterized by low PH (2-4) and high SO4 (UP to 800 mg L-1). Surface water, sediment and soil samples collected in this study contain higher concentrations of As, Cu, Fe and Zn, compared to the target and/or intervention limits set by international regulatory agencies. In particular, high As concentrations in water (up to 2900 mu g L- 1) and sediment (up to 900 mg kg(-1)) are of concern. There is large variability in trace element concentrations, implying that both physical (grain size) and chemical factors (pH, secondary phases as sulfides, Al-oxides or clay minerals) play an important role in their distribution. The low PH keeps the trace elements dissolved, and they are transported farther downstream. Trace element partition coefficients are low (log K-d = 0.3-4.3), and saturation indices calculated with PHREEQC are < 0 for common oxide and sulfidic minerals. The sediment and soil samples indicate an enhanced pollution index (up to 17), and high enrichment factors for trace elements (As up to 38,300; Zn up to 800). Finally, leaves collected from different plant types indicate bioaccumulation of several elements (As, Al, Cu, Fe and Zn). However, some of the plants growing in this area (e.g., Salix, Equisetum) are generally resistant to metal toxicity, and hence, liming and phytoremediation could be considered as potential on-site remediation methods.

  • 6.
    Bhattacharya, P.
    et al.
    ivision of Land and Water Resources, Kungliga Tekniska Högskolan, SE-100 44 Stockholm, SwedenSE.
    Jacks, G.
    ivision of Land and Water Resources, Kungliga Tekniska Högskolan, SE-100 44 Stockholm, SwedenSE.
    Ahmed, K. M.
    ivision of Land and Water Resources, Kungliga Tekniska Högskolan, SE-100 44 Stockholm, SwedenSE.
    Routh, Joyanto
    Biogeochemistry Section, Department of Geology and Geochemistry, Stockholm University, SE-106 91 Stockholm, SwedenSE.
    Khan, A. A.
    Department of Geology, University of Dhaka, Dhaka 1000, Bangladesh.
    Arsenic in Groundwater of the Bengal Delta Plain Aquifers in Bangladesh2002Inngår i: Bulletin of Environmental Contamination and Toxicology, ISSN 0007-4861, E-ISSN 1432-0800, Vol. 69, nr 4, s. 538-545Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Not Available

  • 7.
    Bragee, Petra
    et al.
    Lund University, Sweden .
    Choudhary, Preetam
    EBC, Sweden .
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Boyle, John F.
    University of Liverpool, England .
    Hammarlund, Dan
    Lund University, Sweden .
    Lake ecosystem responses to catchment disturbance and airborne pollution: an 800-year perspective in southern Sweden2013Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 50, nr 4, s. 545-560Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sediment sequences spanning the last 800 years from two small lakes in the south Swedish uplands were explored for assessment of effects of changing human population, local land-use practices and airborne pollution on lake-ecosystem functioning and resilience. Variations in nutrient cycling and deposition of lithogenic elements were studied, using a multi-proxy stratigraphic approach. Carbon and nitrogen elemental and isotopic analyses were applied in combination with records of hydrocarbons (n-alkanes) to investigate the sources and depositional conditions of sediment organic matter. Changes in fluvial and airborne delivery of inorganic matter were based on X-ray fluorescence measurements. The results reveal that population growth and related increases in land-use pressure had a major impact on catchment erosion and input of terrestrial organic matter to the lakes from the 1500s to the end of the 1800s. Evidence also exists of a brief period of catchment disturbance at ca. 1200-1300, followed by recovery, likely connected to the Black Death pandemic. At ca. 1900 synchronous shifts in most of the proxy records suggest a marked change in external forcing common to the two lakes related to a major decrease in population density and the introduction of modern forestry following the industrial revolution. Interestingly, the two sediment records exhibit generally coherent trends in C/N ratio, organic C content and delta C-13, both before and after 1900, indicating broadly similar sensitivities of the lake ecosystems to human impact. In contrast, deviating trends in total N content, delta N-15 and lithogenic element concentrations (K, Ti, Rb and Zr) reflect site-specific responses to local disturbances during the last century due to different nutrient conditions and catchment properties. Our companion sediment records highlight the importance of understanding long-term human impact on watersheds and demonstrate how regional versus local forcing of lake ecosystems, as well as site-specific responses related to catchment characteristics can be reconstructed.

  • 8.
    Choudhary, Preetam
    et al.
    Department of Earth Sciences, Indian Institute of Technology, Roorkee 247 667, India.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Distribution of polycyclic aromatic hydrocarbons in Kumaun Himalayan Lakes, northwest India2010Inngår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 41, nr 9, s. 891-894Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sources and historical deposition of polycyclic aromatic hydrocarbons (PAHs) were investigated in dated sediment cores from Lakes Nainital and Bhimtal in the Kumaun Himalaya The data show that PAH deposition has increased in recent years and is associated with an increase in anthropogenic activity. The lake sediments dominantly contain low molecular weight (LMW) PAHs. derived mainly from petrogenic sources Concentrations of individual and total PAHs were categorized on the basis of sediment quality criteria. According to this, the pollutants pose a potential threat to aquatic life.

  • 9.
    Choudhary, Preetam
    et al.
    Uppsala University, Sweden.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Chakrapani, Govind J.
    Indian Institute Technology, India.
    A 100-year record of changes in organic matter characteristics and productivity in Lake Bhimtal in the Kumaon Himalaya, NW India2013Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 49, nr 2, s. 129-143Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sediment variables total organic carbon (TOC), total nitrogen (TN), total sulfur (TS), as well as their accumulation rates and atomic ratios (C/N and C/S), were studied along with stable isotopes (δ13C, δ15N, and δ34S), and specific biomarkers (n-alkanes and pigments) in a 35-cm-long sediment core from Lake Bhimtal, NW India. The average sedimentation rate is 3.6 mm year−1, and the core represents a provisional record of ~100 years of sedimentation history. Bulk elemental records and their ratios indicate that sediment organic matter (OM) is derived primarily from algae. In-lake productivity increased sharply over the last two decades, consistent with paleoproductivity reconstructions from other lakes in the area. An up-core decrease in δ13C values, despite other evidence for an increase in lake productivity, implies that multiple biogeochemical processes (e.g. external input of sewage or uptake of isotopically depleted CO2 as a result of fossil fuel burning) influence the C isotope record in the lake. The δ15N values (−0.2 to −3.9 ‰) reflect the presence of N-fixing cyanobacteria, and an increase in lake productivity. The δ34S profile shows enrichment of up to 5.6 ‰, and suggests that sulfate reduction occurred in these anoxic sediments. Increases in total n-alkane concentrations and their specific ratios, such as the Carbon Preference Index (CPI) and Terrestrial Aquatic Ratio (TAR), imply in-lake algal production. Likewise, pigments indicate an up-core increase in total concentration and dominance of cyanobacteria over other phytoplankton. Geochemical trends indicate a recent increase in the lake’s trophic state as a result of human-induced changes in the catchment. The study highlights the vulnerability of mountain lakes in the Himalayan region to both natural and anthropogenic processes, and the difficulties associated with reversing trophic state and ecological changes.

  • 10.
    Choudhary, Preetam
    et al.
    Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee 247667, India.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, 10691 Stockholm, Sweden.
    Chakrapani, Govind J.
    Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee 247667, India.
    An environmental record of changes in sedimentary organic matter from Lake Sattal in Kumaun Himalayas, India2009Inngår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 407, nr 8, s. 2783-2795Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sattal a small mountainous lake in the Kumaun Himalayas has been impacted by various cultural activities in recent years. We explored the effects of human-induced changes in this lake by using various geochemical proxies. Shifts in TOC and N flux, C/N ratio, stable isotopes (delta C-13 and delta N-15), n-alkane, and pigment concentrations in sediments indicate a steady increase in primary productivity over the last few decades. The trophic status of the lake has changed from mesotrophic to eutrophic condition. The C/N, CPI, and TAR based ratios in sediments indicate accumulation of algal matter derived primarily from in situ production, with limited input of terrestrial organic matter from the watershed. The low (between 0.1 and 1 parts per thousand) delta N-15 values imply N-2-fixation by cyanobacteria, and the decrease in delta C-13 values up-core represent the effect of sewage input and land based runoff, or possible contribution from microbial biomass. The pigments change from non-N-2 fixing cyanobacterial species to the N-2-fixing community, and are consistent with the proxy-based productivity shifts inferred in the lake. The deeper sediments are affected by post-diagenetic changes causing an increase in delta C-13 (and possibly delta N-15) due to mineralization of organic C and N. 

  • 11.
    Choudhary, Preetam
    et al.
    Department of Earth Sciences, Indian Institute of Technology, Roorkee, India.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Chakrapani, Govind J.
    Department of Earth Sciences, Indian Institute of Technology, Roorkee, India.
    Organic geochemical record of increased productivity in Lake Naukuchiyatal, Kumaun Himalayas, India2010Inngår i: Environmental Earth Sciences, ISSN 1866-6280, E-ISSN 1866-6299, Vol. 60, nr 4, s. 837-843Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Organic geochemical proxies have been studied in a 45-cm-long core retrieved from Lake Naukuchiyatal in Kumaun Himalayas, India. Increase in TOC, N, hydrocarbons and pigments concentration from bottom to surface sediments of the core indicates increase in the lake productivity. Stable isotopes (δ13C and δ 15 N), biomarkers (TAR, CPI and n-ΣC15,17,19) and C/N atomic (between 9 and 12) suggest dominance of algal derived organic matter in these sediments. Decrease in organic δ13C values (between −27 and −31‰) in surface sediments indicate influence of sewage and land runoff in shifting organic δ13C values, whereas low (between −0.23 and 2.2‰) δ15N values together with high pigment concentrations (zeaxanthin and echinenone) represent dominance of cyanobacteria in the lake.

  • 12.
    Choudhary, Preetam
    et al.
    Department of Earth Sciences, Indian Institute of Technology, Roorkee, India.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Chakrapani, Govind J.
    Department of Earth Sciences, Indian Institute of Technology, Roorkee, India.
    Kumar, Bhishm
    National Institute of Hydrology, Roorkee, India.
    Biogeochemical records of paleoenvironmental changes in Nainital Lake, Kumaun Himalayas, India2009Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 42, nr 4, s. 571-586Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rapid urbanization and increased tourism around Nainital Lake in the Kumaun Himalayan region in north India has raised concerns about sediment and water pollution. Lead-210 dated sediment cores from the lake represent similar to 95 years of accumulation and yield a mean sedimentation rate of similar to 4.7 mm year(-1). Total organic carbon (TOC), percent N and S and their atomic C/N and C/S ratios, stable isotopes (delta C-13, delta N-15, and delta S-34), and specific biomarkers (n-alkanes and pigments) were measured in the core. Organic matter is primarily derived from in-lake algal production and TOC flux varies from 1.0 to 3.5 g m(-2) year(-1). Sediments are anoxic (Eh -328 to -187 mV) and have low (0.10-0.30 g m(-2) year(-1)) N, but high (0.37-1.0 g m(-2) year(-1)) S flux. Shifts in delta C-13, delta N-15, and delta S-34 suggest in-lake microbial processes dominated by denitrification and sulfate reduction. The sediments are dominated by short-chain hydrocarbons with low Carbon Preference Index values. The pigments indicate a gradual shift to cyanobacterial domination of the phytoplankton community in recent years. Despite an increase in external input of nutrients, the trophic state of the lake has remained largely unchanged, and the perceived human-induced impacts are limited.

  • 13.
    Collins, Matthew D.
    et al.
    School of Food Biosciences, University of Reading, Whiteknights, Reading RG6 6AP, UK.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden .
    Saraswathy, Ambujom
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden .
    Lawson, Paul A.
    School of Food Biosciences, University of Reading, Whiteknights, Reading RG6 6AP, UK.
    Schumann, Peter
    DSMZ – Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany.
    Welinder-Olsson, Christina
    Culture Collection, Department of Clinical Bacteriology, University of Göteborg, Göteborg, Sweden.
    Falsen, Enevold
    Culture Collection, Department of Clinical Bacteriology, University of Göteborg, Göteborg, Sweden.
    Arsenicicoccus bolidensis gen. nov., sp. nov., a novel actinomycete isolated from contaminated lake sediment2004Inngår i: International Journal of Systematic and Evolutionary Microbiology, ISSN 1466-5026, E-ISSN 1466-5034, Vol. 54, nr 2, s. 605-608Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An unknown Gram-positive, catalase-positive, facultatively anaerobic, non-spore-forming, coccus-shaped bacterium originating from sediment was characterized using phenotypic, molecular chemical and molecular phylogenetic methods. Chemical studies revealed the presence of a cell-wall murein based on ll-diaminopimelic acid (type ll-Dpm-glycine1), a complex mixture of saturated, monounsaturated and iso- and anteiso-methyl-branched, non-hydroxylated, long-chain cellular fatty acids and tetrahydrogenated menaquinones with eight isoprene units [MK-8(H4)] as the major respiratory lipoquinone. This combination of characteristics somewhat resembled members of the suborder Micrococcineae, but did not correspond to any currently described species. Comparative 16S rRNA gene sequencing confirmed that the unidentified coccus-shaped organism is a member of the Actinobacteria and represents a hitherto-unknown subline related to, albeit different from, a number of taxa including Intrasporangium, Janibacter, Terrabacter, Terracoccus and Ornithinicoccus. Based on phenotypic and phylogenetic considerations, it is proposed that the unknown bacterium originating from lake sediment be classified as a new genus and species, Arsenicicoccus bolidensis gen. nov., sp. nov. (type strain CCUG 47306T=DSM 15745T).

  • 14.
    Das, Supriyo K.
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Roychoudhury, Alakendra N.
    Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa.
    Klump, J. Val
    Department of Biological Sciences and Department of Geosciences, Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, USA.
    Elemental (C, N, H and P) and stable isotope (del15 N and del13C) signatures in sediments from Zeekoevlei, South Africa: a record of human intervention in the lake2007Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 39, nr 3, s. 349-360Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We used elemental carbon, nitrogen, phosphorus and hydrogen ratios (C/N, N/P and H/C) with total organic carbon (TOC) and total phosphorus (TP) as well as stable carbon and nitrogen isotopes (δ13C and δ15N) to investigate the source and depositional conditions of organic matter in sediments from Zeekoevlei, the largest freshwater lake in South Africa. Typical C/N (10–12), H/C ratios (≥1.7) and δ13Corganic values (−22 to −19‰) together with the increase in TOC concentration indicate elevated primary productivity in lower middle (18–22 cm) and top (0–8 cm) sections of the sediment cores. Seepage of nutrients from a nearby waste water treatment plant, rapid urbanization and heavily fertilized farming in the catchments are responsible for the increased productivity. Consistent with this, measured δ15Norganic values (∼11‰) indicate increased raw sewage input towards the top-section of the core. Although cyanobacterial blooms are evident from the low δ15N values (∼3‰) in mid-section of the core, they did not outnumber the phytoplankton population. Low N/P ratio (∼0) and high TP (100–2,200 mg l−1) support cyanobacterial growth under N limited condition, and insignificant input of macrophytes towards the organic matter pool. Dredging in 1983, caused sub-aerial exposure of the suspended and surface sediments, and affected organic matter preservation in the upper mid-section (12–14 cm) of the core.

  • 15.
    Das, Supriyo Kumar
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Roychoudhury, Alakendra N.
    Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa.
    Biomarker evidence of macrophyte and plankton community changes in Zeekoevlei, a shallow lake in South Africa2009Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 41, nr 3, s. 507-521Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Zeekoevlei is the largest freshwater lake in South Africa and has a century-long history of anthropogenic impact that caused hyper-eutrophic conditions. We used biomarkers (alkanes and pigments), stable isotopes (delta C-13 and delta N-15), rates of primary palaeoproduction and total inorganic carbon (TIC) accumulation rates in the lake sediments to investigate changes in plankton and macrophyte communities in response to anthropogenic activities in this shallow lake. Specific alkanes (I C-15 pound,C-17,C-19, pristane, phytane and n-C-29/n-C-17 ratio) and pigment (chlorophyll a, beta,beta-carotene, echinenone, fucoxanthin and zeaxanthin) concentrations in lake waters indicated the present-day hyper-eutrophic condition and seasonal fluctuations of cyanobacteria, zooplankton and diatom populations. Eutrophic conditions were initiated in the lake with the start of recreational activities and construction of a sewage treatment plant in the early 1920s. The lake transformed from a eutrophic to a hyper-eutrophic waterbody following damming, pondweed eradication and accelerated catchment-derived nutrient input. The change in lake trophic state was recorded by a sharp decline in the terrestrial to aquatic ratio (TAR) of specific n-alkanes, low carbon preference index (CPI) and increased delta C-13 values in the sediment core. In addition, the aquatic macrophyte n-alkane proxy (P-aq) values (similar to 1) indicated a slow takeover by floating macrophytes after the eradication of submerged pondweeds in 1951. Elevated n-alkane (I C-15 pound,C-17,C-19), total alkane and pigment (chlorophyll a, beta,beta-carotene, zeaxanthin and zeaxanthin to beta,beta-carotene ratio) concentrations, low delta N-15 values and low TIC accumulation rates in the upper middle section of the core indicated the beginning of intense cyanobacterial blooms after the dredging in 1983. Although the cyanobacterial population has decreased in recent years, hyper-eutrophic conditions are reflected by low CPI < 0.04 and TAR < 1 values at the top of the sediment core.

  • 16.
    Das, Supriyo Kumar
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm 10691, Sweden.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm 10691, Sweden.
    Roychoudhury, Alakendra N.
    Department of Geological Sciences, University of Cape Town, Rondebosch 7700, South Africa.
    Sources and historic changes in polycyclic aromatic hydrocarbon input in a shallow lake, Zeekoevlei, South Africa2008Inngår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 39, nr 8, s. 1109-1112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigated the source, seasonality and historical changes in polycyclic aromatic hydrocarbons (PAHs) in Zeekoevlei, a shallow freshwater lake in South Africa. PAH input follows historical changes in land use pattern and recreational activities in Zeekoevlei since the early 1990s. Because anthropogenic activity in the catchment is low, this has resulted in an overall low PAH concentration in the water column and sediments. PAHs of mainly petrogenic origin dominate.

  • 17.
    Das, Supriyo Kumar
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Roychoudhury, Alakendra N.
    Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa.
    Klump, J. Val
    Department of Biological Sciences and Department of Geosciences, Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, USA.
    Elemental (C, N, H and P) and stable isotope (delta N-15 and delta C-13) signatures in sediments from Zeekoevlei, South Africa: a record of human intervention in the lake2008Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 39, nr 3, s. 349-360Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We used elemental carbon, nitrogen, phosphorus and hydrogen ratios (C/N, N/P and H/C) with total organic carbon (TOC) and total phosphorus (TP) as well as stable carbon and nitrogen isotopes (delta C-13 and delta N-15) to investigate the source and depositional conditions of organic matter in sediments from Zeekoevlei, the largest freshwater lake in South Africa. Typical C/N (10-12), H/C ratios (>= 1.7) and delta C-13(organic) values (-22 to -19 parts per thousand) together with the increase in TOC concentration indicate elevated primary productivity in lower middle (18-22 cm) and top (0-8 cm) sections of the sediment cores. Seepage of nutrients from a nearby waste water treatment plant, rapid urbanization and heavily fertilized farming in the catchments are responsible for the increased productivity. Consistent with this, measured delta(15) N-organic values (similar to 11) indicate increased raw sewage input towards the top-section of the core. Although cyanobacterial blooms are evident from the low delta N-15 values (similar to 3 parts per thousand) in mid-section of the core, they did not outnumber the phytoplankton population. Low N/P ratio (similar to 0) and high TP (100-2,200 mg l(-1)) support cyanobacterial growth under N limited condition, and insignificant input of macrophytes towards the organic matter pool. Dredging in 1983, caused sub-aerial exposure of the suspended and surface sediments, and affected organic matter preservation in the upper mid-section (12-14 cm) of the core.

  • 18.
    Das, Supriyo Kumar
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Roychoudhury, Alakendra N.
    Department of Geological Sciences, University of Cape Town, Rondebosch 7700, South Africa.
    Klump, J. Val
    Department of Biological Sciences and Department of Geosciences, Great Lakes WATER Institute, University of Wisconsin-Milwaukee, 600 East Greenfield Avenue, Milwaukee, WI 53204, USA.
    Major and trace element geochemistry in Zeekoevlei, South Africa: A lacustrine record of present and past processes2008Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 23, nr 8, s. 2496-2511Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study reports a multi-parameter geochemcial investigation in water and sediments of a shallow hyper-eutrophic urban freshwater coastal lake, Zeekoevlei, in South Africa. Zeekoevlei receives it greater fraction of dissolved major and trace elements from natural Sources (e.g., chemical weathering and sea salt). Fertilizers, agricultural wastes, raw sewage effluents and road runoff in contrast, constitute the predominant anthropogenic sources, which supply As, Cd, Cu, Pb and Zn in this lake. The overall low dissolved metal load results from negligible industrial Pollution, high pH and elevated metal Uptake by phytoplankton. However, the surface sediments are highly polluted with Pb, Cd and Zn. Wind-induced sediment resuspension results in increased particulate and dissolved element concentrations in bottom waters. Low C/N ratio (10) indicates primarily an algal Source for the sedimentary organic matter. Variation in sedimentary organic C content with depth indicates a change in primary productivity in response to historical events (e.g., seepage from wastewater treatment plant, dredging and urbanization). Primary productivity controls the enrichment of most of the metals ill sediments, and elevated productivity with higher accumulation of planktonic debris (and siltation) results in increased element concentration in surface and deeper sediments. Aluminium, Fe and/or Mn oxy-hydroxides, clay minerals and calcareous sediments also play an important role in adsorbing metals in Zeekoevlei Sediments. 

  • 19.
    Das, Supriyo Kumar
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Routh, Joyanto
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Roychoudhury, Alakendra N.
    Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa.
    Val Klump, J.
    Department of Biological Sciences and Department of Geosciences, Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, USA.
    Ranjan, Rajesh Kumar
    School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.
    Phosphorus dynamics in shallow eutrophic lakes: an example from Zeekoevlei, South Africa2009Inngår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 619, s. 55-66Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Zeekoevlei is the largest freshwater lake in South Africa and has been suffering from hyper-eutrophic conditions since last few decades. We have used total P (TP), dissolved phosphate (PO4 (3-)), organic P (OP), calcium (Ca) and iron (Fe) bound P fractions to investigate the relevant physical, chemical and biological processes responsible for sedimentation and retention of P and to study phosphorus (P) dynamics in this shallow lake. In addition, redox proxies (V/Cr and Th/U ratios) are used to study the prevailing redox conditions in sediments. Adsorption by CaCO3 and planktonic assimilation of P are found to control P sedimentation in Zeekoevlei. Low concentration of the labile OP fraction in surface sediments restricts the release of P by bacterial remineralisation. Low molar Ca/P and Fe/P ratios indicate low P retention capacity of sediments, and P is most likely released by desorption from wind-induced resuspended sediments and mixing of pore water with the overlying water column.

  • 20.
    Ghosh, Devanita
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten. Integrative Taxonomy and Microbial Ecology Research Group, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India.
    Bhadury, Punyasloke
    Integrative Taxonomy and Microbial Ecology Research Group, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Coping with arsenic stress: Adaptations of arsenite-oxidizing bacterial membrane lipids to increasing arsenic levels2018Inngår i: Open Microbiology Journal, ISSN 1874-2858, E-ISSN 1874-2858, Vol. 7, nr 5, artikkel-id e00594Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract Elevated levels of arsenic (As) in aquifers of South East Asia have caused diverse health problems affecting millions of people who drink As-rich groundwater and consume various contaminated agriculture products. The biogeochemical cycling and mobilization/immobilization of As from its mineral-bound phase is controlled by pH, oxic/anoxic conditions, and different microbial processes. The increased As flux generated from ongoing biogeochemical processes in the subsurface in turn affects the in situ microbial communities. This study analyzes how the indigenous arsenite-oxidizing bacteria combat As stress by various biophysical alterations and self-adaptation mechanisms. Fifteen arsenite-oxidizing bacterial strains were isolated and identified using a polyphasic approach. The bacterial strains isolated from these aquifers belong predominantly to arsenite-oxidizing bacterial groups. Of these, the membrane-bound phospholipid fatty acids (PLFA) were characterized in seven selected bacterial isolates grown at different concentrations of As(III) in the medium. One of the significant findings of this study is how the increase in external stress can induce alteration of membrane PLFAs. The change in fatty acid saturation and alteration of their steric conformation suggests alteration of membrane fluidity due to change in As-related stress. However, different bacterial groups can have different degrees of alteration that can affect sustainability in As-rich aquifers of the Bengal Delta Plain.

  • 21.
    Ghosh, Devanita
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten. Ind Institute Science Educ and Research Kolkata, India.
    Bhadury, Punyasloke
    Ind Institute Science Educ and Research Kolkata, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Diversity of arsenite oxidizing bacterial communities in arsenic-rich deltaic aquifers in West Bengal, India2014Inngår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 5, nr 602, s. 1-14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High arsenic (As) concentration in groundwater has affected human health, particularly in South-East Asia putting millions of people at risk. Biogeochemical cycling of As carried out by different bacterial groups are suggested to control the As fluxes in aquifers. A functional diversity approach in link with As precipitation was adopted to study bacterial community structures and their variation within the As contaminated Bengal Delta Plain (BDP) aquifers of India. Groundwater samples collected from two shallow aquifers in Karimpur II (West Bengal, India), during years 2010 and 2011, were investigated to trace the effects immediately after monsoon period (precipitation) on community structure and diversity of bacterial assemblages with a focus on arsenite oxidizing bacterial phyla for two successive years. The study focused on amplification, clone library generation and sequencing of the arsenite oxidase large sub-unit gene aioA and 16S rRNA marker, with respect to changes in elemental concentrations. New set of primers were designed to amplify the aioA gene as a phylogenetic marker to study taxonomically diverse arsenite oxidizing bacterial groups in these aquifers. The overall narrow distribution of bacterial communities based on aioA and 16S rRNA sequences observed was due to poor nutrient status and anoxic conditions in these As contaminated aquifers. Proteobacteria was the dominant phylum detected, within which Acidoyorax, Hydrogenophaga, Albidiferax, Bosea, and Polymorphum were the major arsenite oxidizing bacterial genera based on the number of clones sequenced. The structure of bacterial assemblages including those of arsenite oxidizing bacteria seems to have been affected by increase in major elemental concentrations (e.g., As, Fe, S, and Si) within two sampling sessions, which was supported by statistical analyses. One of the significant findings of this study is detection of novel lineages of 16S rRNA-like bacterial sequences indicating presence of indigenous bacterial communities BDP wells that can play important role in biogeochemical cycling of elements including As.

  • 22.
    Ghosh, Devanita
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten. Laboratory of Integrative Taxonomy and Molecular Ecology, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Bhadury, Punyasloke
    Laboratory of Integrative Taxonomy and Molecular Ecology, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India.
    Characterization and microbial utilization of dissolved lipid organic fraction in arsenic impacted aquifers (India)2015Inngår i: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 527, s. 221-233Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The coupled role of organic matter (OM) and microbial activity is widely acknowledged in arsenic (As) biogeochemical cycling in sedimentary environments. However, little is known about OM characteristics particularly the dissolved fraction in the Bengal Delta Plain aquifers – one of the worst As impacted regions in the world. Ongoing investigations in As-rich aquifers in Nadia district (West Bengal, India) indicate presence of arsenite As(III) oxidizing bacterial communities in the Grey Sand Aquifers (GSA), but absent in Brown Sand Aquifers (BSA). In this study, we investigate the key differences in dissolved organic carbon (DOC) characteristics and its relationship with differences in elemental concentrations, distribution of biomarkers, and utilization of DOC by in situ microbial communities in BSA and GSA. We demonstrate a new approach using ENVI™ C-18 DSK discs to pre-concentrate DOC from large volumes of water, and further extract the OM and separate it into different lipid fractions using the solid phase extraction technique. The aquifers show marked heterogeneity in terms of their DOC characteristics and elemental profiles irrespective of their grey or brown color. DOC indicates variable inputs of terrestrial derived OM sources, and OM derived from decomposition and/or microbial cellular components. DOC in the aquifers consist of predominantly n-alkanoic acids (∌80%) followed by n-alkanes and n-alcohols. The GSAs indicate high iron (Fe) and manganese (Mn) concentrations, and presence of mature petroleum derived hydrocarbons in DOC. BSA has comparatively lower concentrations of Fe and Mn, and shows absence of mature hydrocarbons in DOC. Experiments in presence of indigenous bacteria from groundwater with DOC lipid extracts as the sole carbon source indicate higher growth in the GSA samples implying preferential use of DOC. The potential availability of DOC in these aquifers can influence the community composition of indigenous heterotrophic microbial flora, which in turn can affect elemental cycles including that of As.

  • 23.
    Ghosh, Devanita
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten. Integrative Taxonomy and Microbial Ecology Research Group, Department of Biological Sciences, Indian Institute of Science Education and Research-Kolkata, Mohanpur, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Bhadury, Punyasloke
    Integrative Taxonomy and Microbial Ecology Research Group, Department of Biological Sciences, Indian Institute of Science Education and Research-Kolkata, Mohanpur, India.
    Sub-surface Biogeochemical Characteristics and Its Effect on Arsenic Cycling in the Holocene Gray Sand Aquifers of the Lower Bengal Basin2017Inngår i: Frontiers in Environmental Science, ISSN 2296-665X, Vol. 5, artikkel-id 82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High arsenic (As) content in the fertile delta plains of West Bengal has been widely reported since the 1990s. The shallow grey sand aquifers (GSA) deposited during the Holocene, are more commonly used as potable water sources, but they have high As levels. The release of As into groundwater is influenced by indigenous microbial communities metabolizing different organic carbon sources present in the GSA sediments. After pre-screening the groundwater for assessing their microbial phylogenetic diversity, two50-m deep boreholes were drilled in the GSAs, and 19 sediment samples were recovered from each core. In each of these samples, grain-size distribution, sequential extraction, and quantification of trace metals and total extractable lipids were analyzed. The aquifer sediments consisted of medium to fine micaceous sand with clay lenses in between them; a thick clay layer occurred on top of both boreholes. Arsenic concentration in these sediments varied from 1.80 to 41.0 mg/kg and was mostly associated with the oxide and silicate-rich crystalline minerals. Arsenic showed a significant correlation with Fe in all fractions, suggesting the presence of Fe-(oxy)-hydroxides bound As minerals. The diagnostic lipid biomarkers showed presence of compounds derived from higher plants (epicuticular waxes) and microbial inputs. The biomarkers were abundant in clay and silt-rich layers. The samples indicated preferential preservation of n-alkanes over other functional compounds (e.g. alcohols and fatty acids), that are more reactive, and hence subject to further degradation. Sediments recovered from the borehole indicated the presence of Eustigmatophytes and vascular plant waxes that are mostly surface-derived. The sedimentary lipids also indicated the presence of complex petroleum-derived hydrocarbons. These compounds provide organic substrates, and support the preferential survival of specific microbial communities in these sediments.

  • 24.
    Ghosh, Devanita
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten. Indian Institute Science Educ and Research Kolkata, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Dario, Mårten
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Bhadury, Punyasloke
    Indian Institute Science Educ and Research Kolkata, India.
    Elemental and biomarker characteristics in a Pleistocene aquifer vulnerable to arsenic contamination in the Bengal Delta Plain, India2015Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 61, s. 87-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An elevated level of arsenic (As) in the Indo-Gangetic delta plain aquifers has been reported since the 1990s. Organic matter (OM) present in groundwater and aquifer sediments supports the microbial communities in these aquifers. During installation of a drinking water well, 26 sediment intervals of 6 m each were retrieved up till 156 m from a Pleistocene brown sand aquifer (BSA). Grain size distribution, sequential extraction of metals and total extractable lipids were analyzed in each sample. These parameters were statistically correlated in order to establish relationship between the physical vs. inorganic and organic characteristics, and how these properties affected the distribution of As in BSAs. The aquifer sediments consisted of medium to coarse sand except the surface sediments and those at the bottom of the well, which had high clay and slit content. Arsenic (As) concentration in sediments ranged from 2 to 21 mg/kg and indicated a strong correlation with grain size. Arsenic was mostly associated with crystalline oxides and silicate-rich minerals. Arsenic showed significant correlation with Fe in all fractions, and suggests presence of pyrite bound As-bearing minerals in these sediments. The diagnostic sedimentary lipid biomarkers indicated presence of compounds derived from vascular plants and microbial cell wall. This inference was supported by various diagnostic lipid ratios. The biomarkers were abundant in surface and deeper layers, which had high clay and silt content. The BSA sediments indicated preferential preservation of n-alkanes over other functional compounds, which were more reactive and subject to degradation. The thick clay layer at 132-156 m contained visible plant fragments, and OM in this layer indicated preferential preservation of organic carbon most likely due to the absence of specific microbial communities that degraded these compounds and mobilized As. Statistical analyses indicated the influence of selective inorganic and organic components (As, Fe and fatty acids) controlling the co-distribution of various inorganic and organic components in the aquifer.

  • 25.
    Gurjazkaite, Karolina
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Djamali, Morteza
    Univ Avignon, France.
    Vaezi, Alireza
    Univ Tehran, Iran.
    Poher, Yoann
    Univ Avignon, France.
    Beni, Abdolmajid Naderi
    Iranian Natl Inst Oceanog and Atmospher Sci, Iran.
    Tavakoli, Vahid
    Univ Tehran, Iran.
    Kylin, Henrik
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Vegetation history and human-environment interactions through the late Holocene in Konar Sandal, SE Iran2018Inngår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 194, s. 143-155Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Jiroft valley, situated on banks of the Halil Rud developed as an important agricultural and trading center during the Early Bronze Age. Known for its famous steatite sculptures and clay pottery, the first settlement in Konar Sandal collapsed around 3rd millennium BCE. A second shorter, but major phase of occupation in the settlement occurred towards the end of 2nd millennium BCE. A 250-cm long peat sequence near the archaeological complex at Konar Sandal was investigated to reconstruct the human environment history using palynological, sedimentological and geochemical data. With a basal age of 4 ka, the core traces the hydroclimatic changes and human activities that started just after large scale abandonment of Konar Sandal and extends from the late Bronze Age to the Mongol invasion. The results show that Jiroft had an arid dry climate dominated by the Saharo-Sindian open pseudo-savanna vegetation. However, due to human clearance and intensified agro-sylvo-pastoral activities, and climatic factors, the land-cover shifted from open xeric scrublands to a more open degraded landscape. The principal human occupation was cereal cultivation and herding. However, it is likely that during the more arid periods, communities retreated and abandoned agriculture, facilitating successional processes. Such droughts occurred around 4.0-3.8 ka and 3.4-2.8 ka and are related to the Siberian Anticyclonic system. Declining Artemisia and shrubs indicate milder climates ca. 3.8-3.4 ka and 2.8-0.6 ka. The latter period that started with the rule of the Persian empires (550-650 BCE), and continued through the Islamic era, coincides with intensive human activities, and the highest degradation of vegetation. (C) 2018 Elsevier Ltd. All rights reserved.

  • 26.
    Hugelius, Gustaf
    et al.
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Routh, Joyanto
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Crill, Patrick
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Kuhry, Peter
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Characterization of Soil Organic Matter in Permafrost Terrain – landscape scale analyses from the European Russian Arctic2010Konferansepaper (Annet vitenskapelig)
    Abstract [en]

     1 INTRODUCTION

    Soils of high latitude terrestrial ecosystems are considered key components in the global carbon cycle and hold large stores of Soil Organic Carbon (SOC). The absolute and relative sizes of labile and recalcitrant SOC pools in periglacial terrain are mostly unknown (Kuhry et al. in prep.). Such data has important policy relevance because of its impact on climate change.

    We sampled soils representative of all major land cover and soil types in discontinuous permafrost terrain, European Russian Arctic. We analyzed the bulk soil characteristics including the soil humic fraction to assess the recalcitrance in organic matter quality in down-depth soil profiles.

    2 METHODS

    A comprehensive stratified random soil sampling program was carried out in the Seida area during late summer 2008. From these, we selected nine sites considered representative for the landscape. Active layer and permafrost free upland soils were sampled from dug soil pits with fixed volume corers. Peat plateaus were sampled near thermally eroding edges. Permafrost soils were cored using steel pipes hammered into the frozen peat. Permafrost free fens were sampled using fixed volume Russian corers.

    Radiocarbon dating was used to determine the SOC ages. The soils were analyzed for dry bulk density, elemental content, and stable isotope composition of organic C and N (δ13C, and δ15N). Further, humic acids were extracted, and the degree of humification of SOM assessed based on A600/C and ∆ log K (Ikeya and Watanabe, 2003).

    3 RESULTS

    Figure 1 shows soil organic matter (SOM) characteristics in a peat sequence from one of the nine described sites, a raised bog peat plateau.

    The peatland first developed as a permafrost-free fen during the Holocene Hypsithermal. Permafrost only aggraded in the late Holocene. Anoxic conditions in the fen and permafrost in peat plateau stages reduced decomposition rates and the degree of humification (A600/C) is relatively constant throughout the peat deposit.

    Botanical origin is a key factor in determining SOM quality, which is clearly reflected in the elemental ratio (C/N) and isotopic composition of C and N. There are sharp shifts in humification, C/N and isotopic composition at the peat/clay interface.

    REFERENCES

    Ikeya, K. and Watanabe, A., 2003, Direct expression of an index for the degree of humification of humic acids using organic carbon concentration. Soil Science and Plant Nutrition, 49: 47-53.

    Kuhry, P., Dorrepaal, E., Hugelius G., Schuur, E.A.G. and Tarnocai C., Potential remobilization of permafrost carbon under future global warming. Permafrost and Periglacial Processes, Submitted.

  • 27.
    Hugelius, Gustaf
    et al.
    Stockholm University, Sweden.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Kuhry, Peter
    Stockholm University, Sweden.
    Crill, Patrick
    Stockholm University, Sweden.
    Mapping the degree of decomposition and thaw remobilization potential of soil organic matter in discontinuous permafrost terrain2012Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, nr G2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    [1] Soil organic matter (SOM) stored in permafrost terrain is a key component in the global carbon cycle, but its composition and lability are largely unknown. We characterize and assess the degree of decomposition of SOM at nine sites representing major land-cover and soil types (including peat deposits) in an area of discontinuous permafrost in the European Russian Arctic. We analyze the elemental and stable isotopic composition of bulk SOM, and the degree of humification and elemental composition of humic acids (HA). The degree of decomposition is low in the O-horizons of mineral soils and peat deposits. In the permafrost free non-peatland soils there is enrichment of13C and 15N, and decrease in bulk C/N ratios indicating more decomposed material with depth. Spectral characterization of HA indicates low humification in O-horizons and peat deposits, but increase in humification in the deeper soil horizons of non-peatland soils, and in mineral horizons underlying peat deposits. GIS based maps indicate that less decomposed OM characteristic of the O-horizon and permafrost peat deposits constitute the bulk of landscape SOM (>70% of landscape soil C). We conclude, however, that permafrost has not been the key environmental factor controlling the current degree of decomposition of SOM in this landscape due to relatively recent permafrost aggradation. In this century, active layer deepening will mainly affect SOM with a relatively high degree of decomposition in deeper mineral soil horizons. Additionally, thawing permafrost in peat plateaus may cause rapid remobilization of less decomposed SOM through thermokarst expansion.

  • 28.
    Kumar Das, Supriyo
    et al.
    Linnaeus University, Sweden.
    Bendle, James
    University of Glasgow, Scotland.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Evaluating branched tetraether lipid-based palaeotemperature proxies in an urban, hyper-eutrophic polluted lake in South Africa2012Inngår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 53, s. 45-51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We evaluate the application of the branched glycerol dialkyl glycerol tetraether (br GDGT) based palaeotemperature and palaeoenvironmental proxy to a hyper-eutrophic, polluted and shallow oxic lake. Lake Zeekoevlei is the largest freshwater lake in South Africa, located close to Cape Town. We use published lake-based and soil-based calibration equations, and compare the reconstructed mean annual air temperature (MAT) with regional (South African) and local (Cape Town) instrumental temperature records. The distribution of br GDGTs in the lake sediments is influenced by air temperature. The lake-based calibration equation, which uses the methylation index of branched tetraethers/cyclisation ratio of branched tetraethers (MBT/CBT), formulated for African lakes (Tierney et al., 2010), fits well with the instrumental temperature records. Moreover, the CBT-derived pH likely reflects historic socioeconomic changes in catchment. Our results suggest that a polluted/hyper-eutrophic status and shallow water urban setting do not preclude application of the MBT/CBT-MAT proxy. However, further research is necessary to understand the behaviour of br GDGT–producing bacteria in polluted and highly productive lakes.

  • 29.
    Kumar Das, Supriyo
    et al.
    Presidency University, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Roychoudhury, Alakendra N.
    University of Stellenbosch, South Africa.
    Biogeochemistry of shallow lake sediments: a case study from Verlorenvlei, South Africa2015Inngår i: Current Science, ISSN 0011-3891, Vol. 109, nr 8, s. 1486-1491Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studying the biogeochemistry of shallow lake sediments, especially the source of sedimentary organic matter (OM), is challenging because of the low preservation of OM in shallow lake sediments. Here we report the source of sedimentary OM in a shallow freshwater lake, Verlorenvlei, in South Africa using a number of biogeochemical proxies. Elemental carbon and nitrogen ratio (C/N), and stable C and N isotopes (delta C-13 and delta N-15) indicate algal source of the sedimentary OM. Total organic and inorganic C, different phosphorus fractions, delta C-13 and delta N-15 values indicate repetitive presence of non-N-fixing cyanobacteria under moderate N-limited conditions. Cyanobacterial population in Verlorenvlei is likely influenced by the availability of dissolved inorganic C. Cyanobacterial proliferation in the lake has ceased with accelerated N input as recorded at the top of the core.

  • 30.
    Kumar Ranjan, Rajesh
    et al.
    Jawaharlal Nehru University.
    Routh, Joyanto
    IISER-Kolkata, Mohanpur, India.
    L Ramanathan, AL.
    Jawaharlal Nehru University.
    Val Klump, J. Val
    University of Wisconsin.
    Elemental and stable isotope records of organic matter input and its fate in the Pichavaram mangrove–estuarine sediments (Tamil Nadu, India)2011Inngår i: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 126, nr 1-4, s. 163-172Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to evaluate the sources and fate of organic matter (OM) in the Pichavaram mangrove–estuarine ecosystem, Corg, Ntot, C/Natm, and stable isotopes (δ13Corg and δ15Norg) of five 210Pb dated sediment cores were investigated. Core A was collected from the Vellar Estuary, cores B, C, and D from mangrove forests, and core E was from the Coleroon Estuary. In mangrove sediments, Corg, Ntot, and C/Natm concentration varied from 1.2 ± 0.52%, 0.08 ± 0.03%, and 16.6 ± 4.1%, respectively. In the estuaries, Corg, Ntot, and C/Natm varied from 0.37 ± 0.19%, 0.03 ± 0.01%, and 12.3 ± 2.9%, respectively. In mangrove forests the δ13Corg and δ15Norg values varied from − 24.3 ± 1.8‰ and 4.2 ± 0.86‰, whereas in estuaries these values were − 23.2 ± 1.6‰ and 5.1 ± 1.3‰, respectively. The variation represents variable inputs of marine and terrestrial OM in these area, OM degradation, replacement of native vegetation due to increasing salinity, and early diagenetic changes. Some of these changes could be attributed to anthropogenic activities that have been happening in the Pichavaram complex over the last few decades. OM once deposited in the sediments is rapidly decomposed or remineralized in both mangrove and estuarine sites. The rate of Corg burial is more in mangrove forests than estuaries. Early diagenetic changes are modeled in the cores based on C/N stoichiometry. This was most applicable in mangrove sediments (core C) where ~ 56% C was remineralized representing a first order diagenetic model.

  • 31.
    Kumar Ranjan, Rajesh
    et al.
    Central University of Bihar, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Val Klump, J.
    University of Wisconsin, WI 53204 USA.
    Ramanathan, A. L.
    Jawaharlal Nehru University, India.
    Sediment biomarker profiles trace organic matter input in the Pichavaram mangrove complex, southeastern India2015Inngår i: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 171, s. 44-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nature and distribution of lipid biomarkers (n-alkanes, n-alkanols, sterols and triterpenols) were investigated in five dated sediment cores from the Pichavaram mangrove-estuarine complex in order to: 1) identify the organic matter (OM) sources and its preservation and 2) trace recent changes associated with coastal processes and anthropogenic activities. The mangrove sediment extracts have higher biomarker concentration (22.6 +/- 13.3 mu g/g dry weight) than the estuarine extracts (6.42 +/- 4.92 mu g/g dry weight). Triterpenols are dominant biomarkers in both estuarine and mangrove sediments, and constitute greater than50% of the total lipid extracts. The presence of n-alkanols (n-C-26,C-28,C-30) and abundance of phytosterols (stigmasterol and beta-sitosterol) and triterpenols (taraxerol, beta-amyrin, germanicol, and lupeol) indicate that mangrove vegetation is the primary source of sedimentary OM. The high abundance and unimodal distribution of the long-chain n-alkanes (mainly n-C-25,C-27,C-29), and high values of Terrestrial Aquatic Ratio (TAR 2.4 to 41) and Carbon Preference Index (CPI greater than 8) indicate dominance (and better preservation) of higher plant derived immature OM in mangrove sediments. In contrast the weak dominance of high molecular weight n-alkanes, low CPI (0.75 to 0.90) and TAR (1.9 to 5.7) values, and the presence of high C-27 and C-28 sterols indicate that phytoplankton/algal derived OM is more pronounced in estuarine sediments. Diagenetic changes in sedimentary OM indicate that some of the lipid fractions are reactive, and as a result, they degrade more rapidly than bulk OM. These compounds follow first order decay kinetics, and concur with the downcore diagenetic changes in coastal areas. Resistance to degradation among the different lipid classes show the trend: n-alkane greater than sterol greater than triterpenol greater than n-alkanol. Finally, the study indicates that less freshwater discharge from the Coleroon River is causing a gradual change in mangrove vegetation. There is less input of OM derived from mangrove vegetation into recent sediments. Biomarker trends also indicate that less salt tolerant Rhizophora spp. are gradually replaced by more salt tolerant vegetation consisting of Sueda spp. and Aviccenia spp.

  • 32.
    Kumar Ranjan, Rajesh
    et al.
    Central University of Bihar, India.
    Singh, Gurmeet
    Jawaharlal Nehru University, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Ramanathan, Al
    Jawaharlal Nehru University, India.
    Trace metal fractionation in the Pichavaram mangrove–estuarine sediments in southeast India after the tsunami of 20042013Inngår i: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 185, nr 10, s. 8197-8213Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The geochemistry of coastal sediments of southern India was altered after the tsunami in 2004. A five-step sequential extraction procedure was applied to assess the effects of tsunami on mobility and redistribution of selected elements (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn). Ten surface sediments and three cores were analyzed for different metal fractions (exchangeable, carbonate, reduced, oxidized, and residual). Total metal concentrations increased in mangrove sediments after the tsunami, but their spatial distribution did not show significant variation (except Mn). The sediments were mixed by the tsunami, and there was lack of variation in metal concentrations in different fractions with depth (except Pb and Mn). High concentrations of Pb and Zn occurred in the oxide fractions, whereas Cu, Cr, Cd, and Ni were high in the organic and sulfide-rich fractions. Metals in the residual fraction (lattice bound) had the highest concentration suggesting their non-availability and limited biological uptake in the system. Most of the metals (except Mn) do not constitute a risk based on the different geochemical indices.

  • 33.
    Odhiambo, Moses
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Does Black Carbon Contribute to Eutrophication in Large Lakes?2016Inngår i: Current Pollution Reports, ISSN 2198-6592, Vol. 2, nr 4, s. 236-238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Eutrophication is a major ecological crisis in water bodies. This is mainly driven by anthropogenic activities in the catchment that incorporate various nutrients. Input of nutrients can also be driven by atmospheric deposition, which has a large footprint that goes beyond local point source(s). In particular, black carbon (BC) can be a carrier of various nutrients and increase primary productivity in lakes. We need to monitor the input of BC in large water bodies to fully understand its role in driving primary productivity and change in trophic status.

  • 34.
    Randsalu-Wendrup, Linda
    et al.
    Lund University, Sweden .
    Conley, Daniel J.
    Lund University, Sweden .
    Carstensen, Jacob
    Aarhus University, Denmark .
    Hansson, Lars-Anders
    Lund University, Sweden .
    Bronmark, Christer
    Lund University, Sweden .
    Fritz, Sherilyn C.
    University of Nebraska, NE 68588 USA .
    Choudhary, Preetam
    Uppsala University, Sweden .
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Hammarlund, Dan
    Lund University, Sweden .
    Combining limnology and palaeolimnology to investigate recent regime shifts in a shallow, eutrophic lake2014Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 51, nr 3, s. 437-448Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, we demonstrate that an integrated approach, combining palaeolimnological records and limnological monitoring data, can increase our understanding of changing ecological patterns and processes in shallow lakes. We focused on recent regime shifts in shallow Lake Krankesjon, southern Sweden, including the collapse of the clear-water state in 1975 and its subsequent recovery in the late 1980s. We used diatom, hydrocarbon and biogenic silica sediment records, in concert with limnological data sets on nutrient concentrations, water clarity, chlorophyll-a and water depth, to investigate the shifts. The shift from clear to turbid conditions was abrupt and occurred over 1 to 2 years, whereas recovery of the clear-water state was more gradual, taking 4-5 years. In 1978, shortly after the first regime shift in water clarity, the diatom community underwent a significant shift. It became less diverse, with decreased abundance of epiphytic and planktonic taxa. Despite rising phosphorus concentrations and lower abundance of submerged macrophytes, Lake Krankesjon has remained in the clear-water state over the past 20 years, although this state seems to be increasingly unstable and susceptible to collapse. The complex reactions of the entire lake ecosystem to major changes in lake-water clarity, as shown by the palaeolimnological variables investigated in this study, emphasize the importance of careful lake and catchment management if a stable, clear-water state is desired.

  • 35.
    Ranjan, Rajesh Kumar
    et al.
    Biogeochemistry Laboratory, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.
    Routh, Joyanto
    Department of Earth Sciences, IISER-Kolkata, Mohanpur, India.
    Ramanathan, A. L.
    Biogeochemistry Laboratory, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.
    Bulk organic matter characteristics in the Pichavaram mangrove: estuarine complex, south-eastern India2010Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 25, nr 8, s. 1176-1186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Pichavaram mangrove ecosystem is located between the Vellar and Coleroon Estuaries in south-eastern India. To document the spatial-depth-based variabilities in organic matter (OM) input and cycling, five sediment cores were collected. A comparative study was carried out of grain-size composition, pore water salinity, dissolved organic C (DOC), loss-on-ignition (LOI), elemental ratios (C/N and H/C), pigments (Chl a, Chl b, and total carotenoids), and humification indices. Sand is the major fraction in these cores ranging from 60% to 99% followed by silt and clay; cores from the estuarine margin have high sand content. In mangrove forests, pore-water DOC concentrations are high (32 +/- 14 mg L(-1)), whereas salinity levels are low (50 +/- 5.5 parts per thousand). Likewise, LOI, organic C and N, and pigment concentrations are high in mangroves. OM is mainly derived from upstream terrestrial matter and/or mangrove litter, and marine OM. The humification indices do not vary significantly with depth because of rapid OM turnover. The bulk parameters indicate that the Vellar and Coleroon Estuaries are more affected by anthropogenic processes than mangrove forests. Finally, greater variability and sometimes lack of specific trends in bulk parameters implies that the 2004 tsunami caused extensive mixing in sediments. (C) 2010 Elsevier Ltd. All rights reserved.

  • 36.
    Ranjan, Rajesh Kumar
    et al.
    Central University of Bihar, India.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Ramanathan, A. L.
    Jawaharlal Nehru University, India.
    Klump, J. Val
    School of Freshwater Sciences, University of Wisconsin - Milwaukee, USA.
    Polycyclic aromatic hydrocarbons fingerprints in the Pichavaram mangrove-estuarine sediments, southeastern India2012Inngår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 53, s. 88-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sources and historical deposition of 16 polycyclic aromatic hydrocarbons (PAHs) were investigated in dated sediment cores from the Pichavaram mangrove–estuarine complex. The ΣPAH flux in mangrove and estuarine sediments was 0.064 ± 0.031 μg/cm2/yr and 0.043 ± 0.020 μg/cm2/yr, respectively. The PAH flux in sediments increased up-core, coinciding with rapid urbanization since the 1970s. The flux showed a decrease in recent years (since 1990), coinciding with less riverine discharge, and perhaps more effective implementation of environmental regulations. The sediments were dominated by low molecular weight PAHs, suggesting anthropogenic input. Ratios of specific PAH isomer pairs suggested a greater input of petrogenic vs. pyrogenic derived PAHs. Notably, the deposition of high molecular weight PAHs increase in mangrove surface sediments was due to lignite and firewood combustion. Because of their overall low concentration in sediments it is unlikely these PAHs pose an immediate ecological hazard.

  • 37.
    Routh, Joyanto
    Department of Earth Sciences, University of Roorkee, Roorkee 247667, India.
    Metamorphism and Structural Interpretation of the Zanskar Shear Zone, PJW Himalaya, India1993Inngår i: Journal of the Geological Society of India, ISSN 0016-7622, E-ISSN 0974-6889, Vol. 41, nr 3, s. 187-198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herren in 1987, reported normal faults resulted in the telescoping of metamorphic isograds within a 200 meter zone between Sumche Topko to Mulung Topko in the Zanskar Shear Zone NW Himalaya. However petrographic study-of sections obtained from Mulung Topko and surrounding areas (pensila-padarn section) indicate that the rocks belong to the kyanite-sillimanite-starurolite grade only. Extension crenulation cleavage and other shear criteria show an initial NESW movement after which a layer parallel extension occurred and the shear zone developed. Minieralogical assemblage and mapping indicate that the isograds run paralleI to each other before they possibly truncate against the shear zone along the Pensila-Padam section. A probable model has been proposed to explain the features

  • 38.
    Routh, Joyanto
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Bhattacharya, Aparajita
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Saraswathy, Ambujom
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Jacks, Gunnar
    Department of Land and Water Resources Engineering, KTH, Stockholm, Sweden.
    Bhattacharya, Prosun
    Department of Land and Water Resources Engineering, KTH, Stockholm, Sweden.
    Arsenic remobilization from sediments contaminated with mine tailings near the Adak mine in Vasterbotten district (northern Sweden)2007Inngår i: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 92, nr 1, s. 43-54Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Weathering of mine tailings have resulted in high As concentrations in water (up to 2900 mu g 1(-1)) and sediment (up to 900 mg kg(-1)) samples around the Adak mine. Notably, As occurs as As(III) species (15-85%) in the oxic surface and ground water samples, which is not common. Time-series based sediment incubations were set up in the laboratory with contaminated sediments to study the microbial processes involved in transformation and remobilization of As across the sediment-water interface. The microcosm experiments indicate that microorganisms are capable of surviving in As-rich sediments and reduce As(V) to As(III). A decrease in total As concentration in sediments is coupled to an increase in As(Ill) concentration in the aqueous media. In contrast, the controls (treated with HgCl, and formaldehyde) did not show growth, and As(V) concentrations increased steadily in the sediments and aqueous medium. The results imply that active metabolism is necessary for As(V) reduction. These microorganisms possess reduction mechanisms that are not necessarily coupled to respiration, but most likely impart resistance to As toxicity.

  • 39.
    Routh, Joyanto
    et al.
    Stockholms universitet, Institutionen för geologi och geokemi.
    Choudhary, Preetam
    Department of Earth Sciences, Indian Institute of Technology, Roorkee, India.
    Meyers, Philip A.
    Department of Geological Sciences, University of Michigan, Ann Arbor, USA.
    Kumar, Bhishm
    National Institute of Hydrology, Roorkee, India.
    A sediment record of recent nutrient loading and trophic state change in Lake Norrviken, Sweden2009Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 42, nr 3, s. 325-341Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Human-induced perturbations in the Lake Norrviken catchment, Sweden, over the last 100+ years have left distinctive geochemical imprints in the sediments. Disposal of sewage, industrial, and agricultural run-off into the lake since the end of the nineteenth century changed the trophic status from eutrophic to hyper-eutrophic. The primary organic matter (OM) source in the lake is in situ algal material. Total organic carbon (TOC) concentrations increased near the mid-section of a short sediment core collected from the deepest part of the lake, reflecting elevated epilimnetic productivity and consequent hypolimnetic anoxia. Accompanying shifts to lighter stable organic C and total N isotopic compositions suggest that cyanobacterial productivity increased during this period. The distribution of pigments in the core indicates a shift in the phytoplankton community to a cyanobacteria-dominated system. Moreover, pigments confirm that N-2-fixing versus non-N-2-fixing phytoplankton varied depending upon the external inputs of N and P. Conditions in the lake improved after sewage input was diverted and the lake is currently mesotrophic.

  • 40.
    Routh, Joyanto
    et al.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA.
    Grossman, Ethan L.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA.
    Murphy, Ellyn M.
    Environmental and Energy Sciences Division, Battelle Pacific Northwest Laboratory, Richland, WA 99352, USA.
    Benner, Ronald
    Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.
    Characterization and Origin of Dissolved Organic Carbon in Yegua Ground Water in Brazos County, Texas2005Inngår i: Groundwater, E-ISSN 1745-6584, Vol. 39, nr 5, s. 760-767Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract Dissolved organic carbon (DOC) concentrations in five shallow (< 20 m) and three deeper wells (27 to 30 m) in the Eocene Yegua Formation (Brazos County in east-central Texas) ranged from 92 to 500 ᅵm. Characterization of high, intermediate, and low molecular weight DOC fractions (HMW > 3000 amu, IMW 1000 to 3000 amu, and LMW 500 to 1000 amu) and combined neutral sugar analyses provide information on organic matter sources in the Yegua aquifers. Combined neutral sugars ranged in concentration from 0.6 to 2.7 ᅵmol/L and comprised 0.8% to 6.7% of DOC in ground water. Glucose was the most abundant neutral sugar, followed by xylose and galactose, arabinose, mannose, rhamnose, and fucose. These combined neutral sugars were more diagenetically altered in shallow, oxic ground water as indicated by high mole % fucose + rhamnose and low neutral sugar yield. The precursors for neutral sugars are most probably angiosperm leaves, which show a similar distribution pattern of neutral sugars. Ground water DOC was depleted in 13C relative to soil-zone organic matter (OM) (-16ᅵ to -19ᅵ). The d13C values of bulk DOC and HMW DOC ranged from -24ᅵ to ᅵ32ᅵ, whereas LMW and IMW DOC ranged from -32ᅵ to -34ᅵ and ᅵ16ᅵ to ᅵ28ᅵ, respectively. This variability in d13C values is probably related to microbial processes and selective preservation of OM. Carbon isotope analyses in bulk and different molecular weight DOC fractions imply a predominantly C3 OM source and a low contribution of soil-zone OM to DOC.

  • 41.
    Routh, Joyanto
    et al.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX, 77843, USA.
    Grossman, Ethan L.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX, 77843, USA.
    Ulrich, Glenn A.
    Institute for Energy and the Environment, Department of Botany and Microbiology, 770 Van Vleet Oval, University of Oklahoma, Norman, OK, 73019-0245, USA.
    Suflita, Joseph M.
    Institute for Energy and the Environment, Department of Botany and Microbiology, 770 Van Vleet Oval, University of Oklahoma, Norman, OK, 73019-0245, USA.
    Volatile organic acids and microbial processes in the Yegua formation, east-central Texas2001Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 16, nr 2, s. 183-195Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Geochemical and microbiological evidence indicates that viable microorganisms produce and consume volatile organic acids (VOA) in the Yegua formation. Acetic and propionic acid concentrations in mudstones range from 200 to 1270 and 20 to 38 nmol·gdw−1 respectively, whereas concentrations in sands are 50–200 and less than 20 nmol·gdw−1. VOA concentrations in sediments and in laboratory incubations suggest net production of VOAs by microorganisms in mudstones, and net consumption of VOAs by SO4 reducing bacteria (SRB) in sands. Notably, SRB activity is mostly confined to aquifer sands. Vertical diffusion and advection were modeled to estimate acetic acid transport from aquitard to aquifer. Assuming that SRB completely respire the acetic acid transported into the aquifer (3.2 μmol·l−1·m·a−1), the CO2 production rate in the aquifer sands is 5.3 μmol·l−1·a−1. This slow mineralization rate of in situ organic matter is within the range for deep aquifers, and probably accounts for the long-term survival of microorganisms in oligotrophic environments. Finally, the microbial communities in Yegua sediments appear to exhibit a loose commensalism, with microorganisms in aquitards providing VOAs for respiratory processes (i.e., SO4 reduction) in aquifers.

  • 42.
    Routh, Joyanto
    et al.
    Department of Earth Sciences, IISER-Kolkata, Mohanpur, India.
    Hjelmquist, Per
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Distribution of arsenic and its mobility in shallow aquifer sediments from Ambikanagar, West Bengal, India2011Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 26, nr 4, s. 505-515Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sediments from a core retrieved during installation of a shallow drinking water well in Ambikanagar (West Bengal, India) were analyzed for various physical and chemical parameters. The geochemical analyses included: (1) a 4-step sequential extraction scheme to determine the distribution of As between different fractions, (2) As speciation (As(3+) vs. As(5+)), and (3) C, N and S isotopes. The sediments have a low percentage of organic C and N (0.10-0.56% and 0.01-0.05%, respectively). Arsenic concentration is between 2 and 7 mg kg(-1), and it is mainly associated with the residual fraction, less susceptible to chemical weathering. The proportion of As(3+) in these sediments is high and ranges from 24% to 74%. Arsenic in the second fraction (reducible) correlates well with Mn, and in the residual fraction As correlates well with several transition elements. The stable isotope results indicate microbial oxidation of organic matter involving SO(4) reduction. Oxidation of primary sulfide minerals and release of As from reduction of Fe(oxy)hydroxides do not seem important mechanisms in As mobilization. Instead, the dominance of As(3+) and presence of As(5+) reducing microorganisms in this shallow aquifer imply As remobilization involving microbial processes that needs further investigations.

  • 43.
    Routh, Joyanto
    et al.
    Department of Earth Sciences, IISER-Kolkata, Mohanpur 741 252, India.
    Hjelmquist, Per
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Distribution of arsenic and its mobility in shallow aquifer sediments from Ambikanagar, West Bengal, India2011Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 26, nr 4, s. 505-515Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sediments from a core retrieved during installation of a shallow drinking water well in Ambikanagar (West Bengal, India) were analyzed for various physical and chemical parameters. The geochemical analyses included: (1) a 4-step sequential extraction scheme to determine the distribution of As between different fractions, (2) As speciation (As(3+) vs. As(5+)), and (3) C, N and S isotopes. The sediments have a low percentage of organic C and N (0.10-0.56% and 0.01-0.05%, respectively). Arsenic concentration is between 2 and 7 mg kg(-1), and it is mainly associated with the residual fraction, less susceptible to chemical weathering. The proportion of As(3+) in these sediments is high and ranges from 24% to 74%. Arsenic in the second fraction (reducible) correlates well with Mn, and in the residual fraction As correlates well with several transition elements. The stable isotope results indicate microbial oxidation of organic matter involving SO(4) reduction. Oxidation of primary sulfide minerals and release of As from reduction of Fe(oxy)hydroxides do not seem important mechanisms in As mobilization. Instead, the dominance of As(3+) and presence of As(5+) reducing microorganisms in this shallow aquifer imply As remobilization involving microbial processes that needs further investigations.

  • 44.
    Routh, Joyanto
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Hugelius, Gustaf
    Stockholm University, Sweden .
    Kuhry, Peter
    Stockholm University, Sweden .
    Filley, Timothy
    Purdue University, IN 47907 USA .
    Kaislahti Tillman, Paivi
    Stockholm University, Sweden .
    Becher, Marina
    Stockholm University, Sweden Umeå University, Sweden .
    Crill, Patrick
    Stockholm University, Sweden .
    Multi-proxy study of soil organic matter dynamics in permafrost peat deposits reveal vulnerability to climate change in the European Russian Arctic2014Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 368, s. 104-117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Soil organic carbon (SOC) in permafrost terrain is vulnerable to climate change. Perennially frozen peat deposits store large amounts of SOC, but we know little about its chemical composition and lability. We used plant macrofossil and biomarker analyses to reconstruct the Holocene paleovegetation and paleoenvironmental changes in two peat plateau profiles from the European Russian Arctic. Peat plateaus are the main stores of permafrost soil C in the region, but during most of the Holocene peats developed as permafrost-free rich fens with woody vegetation, sedges and mosses. Around 2200 cal BP, permafrost aggraded at the site resulting in frost heave and a drastic reduction in peat accumulation under the drier uplifted surface conditions. The permafrost dynamics (aggradation, frost-heave and thaw) ushered changes in plant assemblages and carbon accumulation, and consequently in the biomarker trends too. Detailed biomarker analyses indicate abundant neutral lipids, which follow the general pattern: n-alkanols greater than sterols greater than= n-alkanes greater than= triterpenols. The lignin monomers are not as abundant as the lipids and increase with depth. The selected aliphatic and phenolic compounds are source specific, and they have different degrees of lability, which is useful for tracing the impact of permafrost dynamics (peat accumulation and/or decay associated with thawing). However, common interpretation of biomarker patterns, and perceived hydrological and climate changes, must be applied carefully in permafrost regions. The increased proportion (selective preservation) of n-alkanes and lignin is a robust indicator of cumulative decomposition trajectories, which is mirrored by functional compounds (e. g. n-alkanol, triterpenol, and sterol concentrations) showing opposite trends. The distribution of these compounds follows first order decay kinetics, and concurs with the down core diagenetic changes. In particular, some of the biomarker ratios (e. g. stanol/sterol and higher plant alkane index) seem promising for tracing SOC decomposition despite changes in botanical imprint, and sites spanning across different soil types and locations. Carbon accumulation rate calculated at these sites varies from 18.1 to 31.1 gC m(-2) yr(-1), and its evident selective preservation, molecular complexity of organic compounds, and freezing conditions enhance the long-term stability of SOC. Further, our results suggest that permafrost dynamics strongly impact the more undecomposed SOC that could be rapidly remobilized through ongoing thermokarst expansion.

  • 45.
    Routh, Joyanto
    et al.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA.
    Ikramuddin, Mohammed
    Department of Geology, Eastern Washington University, Cheney, WA 99004, USA.
    Trace-element geochemistry of Onion Creek near Van Stone lead-zinc mine (Washington, USA) — Chemical analysis and geochemical modeling1996Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 133, nr 1, s. 211-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Van Stone lead-zinc mine in Washington is a possible contamination source of Columbia River water. Breaching of an old tailings pond, seepage of contaminated water, and surficial transport of mine tailings have increased trace-element (TE) concentrations in the Onion Creek water and sediments. Chemical analyses of water and sediment samples indicate high TE levels near the breached tailings pond. TE contamination indices for sediments indicate high values of Pb, Zn, and other TE’s which decrease downstream. High Kd values (> 104) for several TE’s (e.g., Al, Cd, Fe, Mn, Pb, V, and Zn) suggest their enrichment in the solid phase. TE concentrations in Onion Creek water and sediment sharply attenuate downstream due to: (1) enhanced carbonate dissolution, thereby increasing pH and immobilizing TE’s; (2) sorption to oxides; and (3) change in lithology from carbonate to granite. Speciation model MINTEQA2 was used to study the effect on TE dispersion due to dissolution-precipitation reactions and adsorption to ferrihydrite. In addition to the field and chemical data, the model also supports the hypothesis that Onion Creek sediments are the major sink for TE’s at VSM. Model runs indicate precipitation of Al, Ba, Ca, Fe, Mg, and Mn minerals from oversaturation, whereas TE’s with low concentrations (Cr, Cu, Ni, Se) or geochemically more mobile (As, Mo, Sb) remain dissolved in water. Near the tailings ponds, high pH and abundance of sorption sites in sediments contribute to the complete adsorption of Pb and Zn species. Because ambient conditions result in the sorption of most Pb and Zn ions, Onion Creek water quality meets EPA regulatory standards. These species will persist in Onion Creek sediments as sorbed or insoluble complexes, and without drastic pH changes (< 4.0) they will remain immobilized. However, continued TE enrichment in sediments will prove hazardous to filter feeding and aquatic organisms.

  • 46.
    Routh, Joyanto
    et al.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA.
    McDonald, Thomas J.
    Department of Civil Engineering, Texas A&M University, College Station, TX 77843, USA.
    Grossman, Ethan L.
    Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA.
    Sedimentary organic matter sources and depositional environment in the Yegua formation (Brazos County, Texas)1999Inngår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 30, nr 11, s. 1437-1453Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The complex depositional environment of the Eocene Yegua formation (Brazos County, Texas) can be better understood by integrating organic matter (OM) geochemistry with stratigraphy. Yegua sediments represent parasequences separated by exposure surfaces. Organic petrography and geochemistry (biomarkers, C/N ratios, and carbon isotopes) indicate the presence of both terrestrial and marine OM in transgressive sediments. In contrast, regressive sediments contain only terrestrial OM. These differences relate to contrasting OM sources and depositional styles on the shelf. OM in the sediments is immature and the potential for generating hydrocarbons is poor. The study suggests that organic geochemical data can help in distinguishing transgressive and regressive environments in sedimentary formations.

  • 47.
    Routh, Joyanto
    et al.
    Department of Geology and Geochemistry, Stockholm University, S 10691 Stockholm, Sweden.
    Meyers, Philip A.
    Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063, USA.
    Gustafsson, Örjan
    Department of Geology and Geochemistry, Stockholm University, S 10691 Stockholm, Sweden.
    Baskaran, Mark
    Department of Geology, Wayne State University, Detroit, Michigan 48202, USA.
    Hallberg, Rolf
    Department of Geology and Geochemistry, Stockholm University, S 10691 Stockholm, Sweden.
    Schï¿œldstrï¿œm, Anna
    Department of Geology and Geochemistry, Stockholm University, S 10691 Stockholm, Sweden.
    Sedimentary geochemical record of humanï¿œinduced environmental changes in the Lake Brunnsviken watershed, Sweden2004Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Limnology and Oceanography, Vol. 49, nr 5, s. 1560-1569Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Environmental changes in Lake Brunnsviken, its watershed, and the greater Stockholm region since the middle of the nineteenth century have left interpretable geochemical imprints in the bottom sediments. These human-induced perturbations within the lakeï¿œs watershed included agriculture, urbanization, sewage and industrial disposal, and water column aeration. Smaller d15Ntotal values, high organic carbon mass accumulation rates, low C:N ratios, and larger d13Corg values identify periods of increased nutrient delivery and elevated primary productivity in the lake. C: S ratios that change from high to low trace the transition from an oxic hypolimnion to an anoxic one during the periods of high productivity. Accumulations of redox-sensitive trace elements increase during the anoxic period and are further magnified during a time of industrial waste discharge into the lake. A recent decrease in black carbon concentrations in sediments reflects the conversion from wood and coal to cleaner forms of energy.

  • 48.
    Routh, Joyanto
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Meyers,, Philip
    Department of Geological Sciences, University of Michigan, Ann Arbor, USA.
    Hjorth, Tomas
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Baskaran, Mark
    Department of Geology, Wayne State University, Detroit, USA.
    Hallberg, Rolf
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Sedimentary geochemical record of recent environmental changes around Lake Middle Marviken, Sweden2007Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 37, nr 4, s. 529-545Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Geochemical properties of sediments deposited in Lake Middle Marviken over the last 185 years record the impacts of a succession of environmental changes that have occurred in the watershed. Clear-cutting of forests for wood and charcoal and extensive water harnessing to support the local iron mills from 1897 to 1957 is recorded by low C/N ratios, high black carbon, and low TOC and Ntotal accumulation rates. Larger δ13C and δ15N values in sediments deposited during this period imply higher productivity. Fluctuations in Ntotal and Ptotal accumulation rates show that the lake chemistry has varied between P or N-depleted systems that affected the δ15N values. Organic matter in the sediments is predominantly immature terrestrial material. Furthermore, hydrocarbon CPI, TAR, and Paq values conform with the observed geochemical trends, variations in organic matter sources, and changes in the watershed. Accumulation rates of Cd, Pb, Zn, and S remained mostly unchanged throughout the period of mining, but an increase from 1957 to 1980 is most likely associated with air-borne industrial and fossil fuel emissions from regional urbanization. In situ microbial processes, such as iron and manganese reduction, also appear to be important in carbon cycling and in affecting the sediment and water chemistry of this lake.

  • 49.
    Routh, Joyanto
    et al.
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Saraswathy, Ambujom
    Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Collins, Matthew D.
    School of Food Biosciences, University of Reading, Reading, Berkshire, UK.
    Arsenicicoccus bolidensis a novel arsenic reducing actinomycete in contaminated sediments near the Adak mine (northern Sweden): Impact on water chemistry2007Inngår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 379, nr 2-3, s. 216-225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Weathering of mine tailings in Adak results in high As concentrations in surface and ground water, sediments, and soil. In spite of the oxic conditions, As-rich surface and ground water samples indicate As(III) species predominantly (up to 83%). Several microorganisms were isolated from the enrichment cultures that were involved in As cycling. Amongst them was Arsenicicoccus bolidensis — a novel gram-positive, facultatively anaerobic, coccus-shaped actinomycete, which actively reduced As(V) to As(III) in aqueous media. A. bolidensis reduced 0.06–0.20 mM day− 1 As(V). As(V) reduction displays a direct correlation between the initial As(V) concentration, growth rate, and biomass yield.

  • 50.
    Shilla, Dativa J.
    et al.
    Department of Chemistry, Dar es Salaam University College of Education, Dar es Salaam, Tanzania.
    Routh, Joyanto
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Distribution, Behavior, and Sources of Polycyclic Aromatic Hydrocarbon in the Water Column, Sediments and Biota of the Rufiji Estuary, Tanzania2018Inngår i: Frontiers in Earth Science, ISSN 2296-6463, Vol. 6, s. 1-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To establish the environmental status of Rufiji coastal waters in Tanzania, it is necessary to document the different contaminants as major entry points into the lower estuarine areas. Because there is no data on polycyclic aromatic hydrocarbon (PAH) contamination in this estuarine delta, the current study measured the concentrations of 19 PAHs in suspended particulate matter (SPM), surface sediments and marine organisms that are part of a telescoping food chain (gastropod Terebralia sp., clams Crassostrea cucullata, crabs Uca sp., panaeid shrimps Panaeus monodon, teleost Hilsa kelee, Trichiurus lepturus, and Arius thalassinus). Total PAH concentrations in SPM were low to moderate (18.7–223 ng/g) and varied between the sites; phenanthrene and chrysene were the dominant PAHs (2.40–47.2 and 4.20–28.1 ng/g, respectively). Significant variation between the sites indicates the influence of fuel spills and contribution from terrestrial sources resulting from different land use practices, such as agriculture, fishing, and harvesting firewood, charcoal, and mangroves poles. PAH concentrations in surface sediments were higher (127–376 ng/g) than SPM samples, and high molecular weight PAHs were the dominant fraction. Animal tissues indicated low PAH levels (9.20–158 ng/g). Only low molecular weight PAHs were dominant in the muscle tissues of pelagic and filter feeders (C. cucullata, P. monodon, and H. kelee). Bioaccumulation factor (BAF) ranged between 0.20 and 69.5 and it suggests 1) PAH accumulation in the marine organisms has so far been limited, and 2) distribution of PAHs in the Rufiji estuary poses limited risks.

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