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Johansson, M. & Svensson, T. (2019). Individual Reflection Paper: Supporting Student's Learning in the Critical Phase of Self-directed Learning in PBL. Journal of Problem Based Learning in Higher Education
Open this publication in new window or tab >>Individual Reflection Paper: Supporting Student's Learning in the Critical Phase of Self-directed Learning in PBL
2019 (English)In: Journal of Problem Based Learning in Higher Education, ISSN 2246-0918, E-ISSN 0974-276XArticle in journal (Refereed) Epub ahead of print
Abstract [en]

Supporting and assessment of students’ preparation and learning process in problem-based learning (PBL) tutorials has long been a challenge. We present a modified PBL model focussing on the specific critical phase in the PBL process, the self-directed learning phase in between tutorial meetings. The modified seven step PBL model including an Individual reflection paper (IRP) is presented as well as students’ perspectives on the implementation of IRP and information literacy, knowledge gathering, and PBL tutorial work. The assessment of PBL work is complex, and the ways in which IRPs support the tutor’s role as an examiner is beyond the scope of the current study. However, it seems that the students experienced assessment of the IRPs as part of their as a positive driving force in their learning process.

Place, publisher, year, edition, pages
Aalborg Universitetsforlag, 2019
Keywords
Individual reflection paper, IRP, Problem based learning, PBL, Self-directed learning, Assessment, Critical thinking, Reflection, Individuellt basgruppsunderlag, IBU, Problem-baserat lärande, Självstyrt lärande, Bedömning, Kristiskt tänkande, Reflektion
National Category
Educational Sciences Didactics Learning Pedagogy Environmental Sciences
Identifiers
urn:nbn:se:liu:diva-153848 (URN)10.5278/ojs.jpblhe.v0i0.2418 (DOI)
Available from: 2019-01-14 Created: 2019-01-14 Last updated: 2019-03-07Bibliographically approved
Svensson, T. (2019). Measurements and fluxes of volatile chlorinated organic compounds (VOCl) from natural terrestrial sources: Measurement techniques and spatio-temporal variability of flux estimates. Stockholm: Swedish Nuclar Fuel and Waste Management CO
Open this publication in new window or tab >>Measurements and fluxes of volatile chlorinated organic compounds (VOCl) from natural terrestrial sources: Measurement techniques and spatio-temporal variability of flux estimates
2019 (English)Report (Other academic)
Abstract [en]

Volatile organic compounds (VOCs) and especially chlorinated VOCs (VOCls) are regarded as en viron mental risk substances in water bodies due to their toxic characteristics. Even in the atmo­sphere they highly impact atmospheric chemistry, e.g. degrading the ozone layer. Several studies have convincingly identified a number of natural VOCl sources thereby challenging the view of VOCls as only produced by humans. Yet, fundamental knowledge is still missing concerning the emission, distribution and the natural abundance of VOCls, especially regarding the high spatial and temporal variability of emissions from terrestrial sources. In the nuclear industry, Cl­36 is a dose­dominating radionuclide in some waste, and this adds to the need to better understand the processes, transport and fate of chlorine in the bio sphere. In this report 38 studies on VOCl flux measurement estimates were reviewed to summarize the current knowledge on spatio­temporal variations of different VOCls and various measurement tech niques.

Chloromethane is the most studied VOCl compound and chloroform, the second most studied. A few other studies have estimated fluxes of additional VOCls such as tetrachloromethane (CCl4), methyl chloroform (CH3CCl3), tetrachloroethane (C2H2Cl4), freons (CFCs), chloroethane (C2H5Cl), bromodichloromethane (CHBrCl2). Studies were conducted in climates and terrestrial ecosystems ranging from arctic tundra to tropical rainforest but most studies focus on the temperate climate region. Wetlands and coastal systems dominate the studied ecosystems. Flux chambers are the most common method for investigation of the soil­atmosphere exchange of VOCls, but a few studies used soil gas profiles and one the Relaxed Eddy Accumulation (REA) technique. Methodological uncer­tainties are mainly related to sample contamination, few replicates, chamber design, and chamber deployment (the time of measurement) effects on the soil­atmosphere exchange itself. Despite the many challenges in measuring VOCls and estimating the fluxes, a substantial part of the chlorine in terrestrial ecosystems, and especially from wetlands and coastal areas, is emitted to the atmosphere as VOCls. In inland forested ecosystems, the release of Cl to the atmosphere could be as much as 0.1 g m–2, which is 40 % of the wet deposition and there are studies that suggest that freshwater wetlands are much larger source of chlorine in the atmosphere than previously understood.

Abstract [no]

Flyktiga organiska föreningar (VOC) och i synnerhet klorerade VOCs (VOCls) betraktas som miljö­farliga ämnen i vattenmiljöer på grund av sina toxiska egenskaper, men även i atmosfären eftersom de har en stor inverkan på atmosfärskemin, t ex genom att påverka ozonskiktet. Ett antal studier har hittat flera naturliga källor för VOCl och därmed förändrat synen på VOCls som endast producerade av människor. Trots det så saknas kunskaperna fortfarande om utsläpp de naturliga flödena av VOCls, särskilt när det gäller variation i tid och rum från terrestra miljöer. I kärnkraftsindustrin är Cl­36 en dosdominerande radionuklid för en del avfallströmmar. Därför behövs en bättre förståelse för omsättningen av klor i ytnära ekosystem.

Klormetan är den mest studerade av VOCl och den näst mest studerade är kloroform. Några andra studier har uppskattat flöde av andra VOCl som tetraklormetan (CCl4), metylkloroform (CH3CCl3), tetrakloretan (C2H2Cl4), freoner (CFC), kloretan (C2H5Cl), bromodiklormetan (CHBrCl2). Studier genomfördes i klimat och markbaserade ekosystem som sträcker sig från arktisk tundra till tropisk regnskog, men de flesta studier fokuserar på tempererat klimatområde. Våtmarker och kustsystem är de studerande dominerande ekosystemen. Kammare är den vanligaste metoden för att uppskatta flöden av av VOCls, men det finns också några studier med koncentrationsgradienter i markprofiler, och en form av mikrometeorologimetodik. De metodologiska osäkerheterna som diskuteras kretsar i första hand kring kontamination, få replikat, design av fältmätningar och fältmätningarnas påverkan på markprocesser och därmed indirekt på flödena. Trots de många utmaningarna för att mäta VOCls och uppskatta flödena är det klart att flödet av klor till atmosfären är ett viktigt flöde i klors biogeo­kemiska cykel i terrestra ekosystem. Skogsekosystem kan avge så mycket som 0.1 g m–2, vilket är 40 % av våtdepositionen av klorid och det finns studier som tyder på att våtmarker är en långt mycket större källa till klor i atmosfären än man tidigare trott.

Place, publisher, year, edition, pages
Stockholm: Swedish Nuclar Fuel and Waste Management CO, 2019. p. 52
Series
Technical report, ISSN 1404-0344 ; TR-18-09
Keywords
VOCl, volatile, chlorine, emission, flux, soil, wetland
National Category
Environmental Sciences Soil Science Food Science Forest Science Ecology
Identifiers
urn:nbn:se:liu:diva-156693 (URN)
Funder
Swedish Nuclear Fuel and Waste Management Company, SKB
Available from: 2019-05-09 Created: 2019-05-09 Last updated: 2019-05-09Bibliographically approved
Montelius, M., Svensson, T., Lourino-Cabana, B., Thiry, Y. & Bastviken, D. (2016). Chlorination and dechlorination rates in a forest soil: A combined modelling and experimental approach. Science of the Total Environment, 554-555, 203-210
Open this publication in new window or tab >>Chlorination and dechlorination rates in a forest soil: A combined modelling and experimental approach
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2016 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 554-555, p. 203-210Article in journal (Refereed) Published
Abstract [en]

Abstract Much of the total pool of chlorine (Cl) in soil consists of naturally produced organic chlorine (Clorg). The chlorination of bulk organic matter at substantial rates has been experimentally confirmed in various soil types. The subsequent fates of Clorg are important for ecosystem Cl cycling and residence times. As most previous research into dechlorination in soils has examined either single substances or specific groups of compounds, we lack information about overall bulk dechlorination rates. Here we assessed bulk organic matter chlorination and dechlorination rates in coniferous forest soil based on a radiotracer experiment conducted under various environmental conditions (additional water, labile organic matter, and ammonium nitrate). Experiment results were used to develop a model to estimate specific chlorination (i.e., fraction of Cl− transformed to Clorg per time unit) and specific dechlorination (i.e., fraction of Clorg transformed to Cl− per time unit) rates. The results indicate that chlorination and dechlorination occurred simultaneously under all tested environmental conditions. Specific chlorination rates ranged from 0.0005 to 0.01 d− 1 and were hampered by nitrogen fertilization but were otherwise similar among the treatments. Specific dechlorination rates were 0.01–0.03 d− 1 and were similar among all treatments. This study finds that soil Clorg levels result from a dynamic equilibrium between the chlorination and rapid dechlorination of some Clorg compounds, while another Clorg pool is dechlorinated more slowly. Altogether, this study demonstrates a highly active Cl cycling in soils.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Chlorine cycling, Chloride, Organic chlorine, Radioactive chlorine-36, Modelling
National Category
Soil Science Environmental Sciences related to Agriculture and Land-use Agricultural and Veterinary sciences Ecology Forest Science
Identifiers
urn:nbn:se:liu:diva-125912 (URN)10.1016/j.scitotenv.2016.02.208 (DOI)000373274700022 ()26950634 (PubMedID)
Note

Funding agencies:  EDF, France; National Radioactive Waste Management Agency (Andra), France; Linkoping University, Sweden

Available from: 2016-03-08 Created: 2016-03-08 Last updated: 2018-10-05Bibliographically approved
Svensson, T. & Johansson, M. (2016). Miljövetenskaplig undervisning i högre utbildning. In: Thomas Hansson (Ed.), Pedagogik för högskolelärare: (pp. 262-288). Möklinta: Gidlunds förlag
Open this publication in new window or tab >>Miljövetenskaplig undervisning i högre utbildning
2016 (Swedish)In: Pedagogik för högskolelärare / [ed] Thomas Hansson, Möklinta: Gidlunds förlag, 2016, p. 262-288Chapter in book (Other academic)
Abstract [sv]

Det finns didaktiska utmaningar och möjligheter relaterade till ett tvärdisciplinärtämnesområde som det miljövetenskapliga. En central fråga är hur miljövetenskapligutbildning kan utformas för att ge studenterna förutsättningaratt handskas med komplexa, idag möjligen okända, miljöfrågor i en kommandeyrkesverksamhet. I en svensk definition av didaktik är frågeorden Vad, Huroch Varför är centrala, vad bör en miljövetenskaplig utbildning innehålla,hur ska undervisningen genomföras och varför organiseras den som den gör?Det miljövetenskapliga ämnets framväxt har skapat läraktiviteter såsom: case,rollspel, debatt, och projekt. Alla har olika syfte vad gäller bearbetning av innehålloch färdighetsträning. Verklighetsanknuten undervisning är ett viktigt målinom det miljövetenskapliga utbildningsområdet och genom en genomtänktdesign kan studenterna få stöd för lärande inför de arbetsuppgifter de kommeratt möta i teori och i praktik.

Place, publisher, year, edition, pages
Möklinta: Gidlunds förlag, 2016
Keywords
miljövetenskap, tvärvetenskap, pedagogik, didaktik, case, projekt
National Category
Pedagogy Didactics Learning Environmental Sciences Social Sciences Interdisciplinary
Identifiers
urn:nbn:se:liu:diva-124188 (URN)978-91-7844-937-8 (ISBN)
Available from: 2016-01-21 Created: 2016-01-21 Last updated: 2018-01-10Bibliographically approved
Montelius, M., Thiry, Y., Marang, L., Ranger, J., Cornelis, J.-T., Svensson, T. & Bastviken, D. (2015). Experimental Evidence of Large Changes in Terrestrial Chlorine Cycling Following Altered Tree Species Composition. Environmental Science and Technology, 49(8), 4921-4928
Open this publication in new window or tab >>Experimental Evidence of Large Changes in Terrestrial Chlorine Cycling Following Altered Tree Species Composition
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2015 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 8, p. 4921-4928Article in journal (Refereed) Published
Abstract [en]

Organochlorine molecules (Cl-org) are surprisingly abundant in soils and frequently exceed chloride (Cl-) levels. Despite the widespread abundance of Cl-org and the common ability of microorganisms to produce Cl-org, we lack fundamental knowledge about how overall chlorine cycling is regulated in forested ecosystems. Here we present data from a long-term reforestation experiment where native forest was cleared and replaced with five different tree species. Our results show that the abundance and residence times of Cl- and Cl-org after 30 years were highly dependent on which tree species were planted on the nearby plots. Average Cl- and Cl-org content in soil humus were higher, at experimental plots with coniferous trees than in those with deciduous trees. Plots with Norway spruce had the highest net accumulation of Cl- and Cl-org over the experiment period, and showed a 10 and 4 times higher Cl- and Cl-org storage (kg ha(-1)) in the biomass, respectively, and 7 and 9 times higher storage of Cl- and Cl-org in the soil humus layer, compared to plots with oak. The results can explain why local soil chlorine levels are frequently independent of atmospheric deposition, and provide opportunities for improved modeling of chlorine distribution and cycling in terrestrial ecosystems.

Place, publisher, year, edition, pages
American Chemical Society, 2015
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:liu:diva-118871 (URN)10.1021/acs.est.5b00137 (DOI)000353610300017 ()25811074 (PubMedID)
Note

Funding Agencies|EDF, France; French national radioactive waste management agency (Andra), France; Linkoping University, Sweden; "Fonds National de la Recherche Scientifique" (FNRS) of Belgium

Available from: 2015-06-05 Created: 2015-06-04 Last updated: 2018-10-05
Bastviken, D., Svensson, T., Sandén, P. & Kylin, H. (2013). Chlorine cycling and fates of 36Cl in terrestrial environments. Stockholm: Swedish Nuclear Fuel and Waste Management Co
Open this publication in new window or tab >>Chlorine cycling and fates of 36Cl in terrestrial environments
2013 (English)Report (Other academic)
Abstract [en]

Chlorine-36 (36Cl), a radioisotope of chlorine (Cl) with a half-life of 301,000 years, is present in some types of nuclear waste and is disposed in repositories for radioactive waste. As the release of 36Cl from such repositories to the near surface environment has to be taken into account it is of interest to predict possible fates of 36Cl under various conditions as a part of the safety assessments of repositories for radioactive waste. This report aims to summarize the state of the art knowledge on Cl cycling in terrestrial environments. The view on Cl cycling in terrestrial environments is changing due to recent research and it is clear that the chloride ion (Cl) is more reactive than previously believed. We group the major findings in three categories below according to the amount of data in support of the findings.

From the result presented in this report it is evident that:

  • There is an ubiquitous and extensive natural chlorination of organic matter in terrestrial ecosystems.
  • The abundance of naturally formed chlorinated organic compounds (Clorg) frequently exceeds the abundance of Cl, particularly in soils. Thereby Clorg in many cases dominates the total Cl pool.
  • This has important implications for Cl transport. When reaching surface soils Cl will not be a suitable tracer of water and will instead enter other Cl pools (Clorg and biomass) that prolong residence times in the system.
  • Cl dominates import and export from terrestrial ecosystems while Clorg and biomass Cl can dominate the standing stock Cl within terrestrial ecosystems.
  • Both Cl and Clorg pools have to be considered separately in future monitoring programs addressing Cl cycling.

Further, there are also indications (in need of confirmation by additional studies) that:

  • There is a rapid and large uptake of Cl by organisms and an accumulation in green plant parts. A surprisingly large proportion of total catchment Cl (up to 60%) can be found in the terrestrial biomass.
  • Emissions of total volatile organohalogens could be a significant export pathway of Cl from the systems.
  • Some of the Clorg may be very persistent and resist degradation better than average organic matter. This may lead to selective preservation of some Clorg (with associated low bioavailability).
  • There is a production of Clorg in tissues of e.g. plants and animals and Cl can accumulate as
  • chlorinated fatty acids in organisms.

Most other nevertheless important aspects are largely unknown due to lack of data. Key unknowns include:

  • The development over time of major Cl pools and fluxes. As long as such data is lacking we cannot assess net changes over time.
  • How the precesses behind chlorination, dechlorination and transport patterns in terrestrial systems are regulated and affected by environmental factors.
  • The ecological roles of the chlorine cycling in general.
  • The ecological role of the microbial chlorination in particular.
  • The chlorine cycling in aquatic environments – including Cl and Clorg pools in sediment and water, are largely missing.

Given the limited present information available, and particularly the lack of data with a temporal dimension and the lack of process understanding, predictive models are challenging. We also summarize currently available methods to study Cl in the environment.

Abstract [sv]

Klor-36 (36Cl), en radioisotop med en halveringstid på 301 000 år, förekommer i vissa typer av radioaktivt avfall. För att kunna förutse vad som händer om 36Cl når markytan är det viktigt att veta hur klor kan omvandlas och transporteras i olika ekosystem. Denna rapport syftar till att sammanfatta kunskapsläget om klor i naturmiljöer med fokus på landmiljöer.

Synen på klor i naturen är under omfattande förändring till följd av de senaste decenniernas forskning. Det står nu helt klart att klorid (Cl) som tidigare betraktats som icke-reaktiv och totalt dominerande, istället är i hög grad reaktiv och inte alltid utgör den dominerande klorformen.

Utifrån de studier som presenteras i rapporten är det tydligt att:

  • Det sker en omfattande naturlig klorering av organiskt material i många miljöer och inte minst i ytliga marklager.
  • Mängden organiskt bunden klor (Clorg) är i många miljöer betydligt högre än mängden Cl. Därmed dominerar Clorg ofta det totala klorförrådet i exempelvis mark.
  • Detta har stor inverkan på transporten av klor eftersom Clorg till stor del finns i partikulärt organiskt material medan Cl är mycket vattenlösligt. Cl som når ytliga marklager är t ex inte lämpligt som spårämne för markvattenflöden såsom tidigare antagits. Cl kommer till stor del att bindas in till Clorg -förrådet och därmed förlänga uppehållstiden i ekosystemen.
  • Cl dominerar både importen och exporten från terrestra ekosystem medan Clorg kan dominera stationära klorförråd i systemen.
  • Framtida mätningar med syfte att klargöra kloromsättning och klorflöden behöver beakta Cl och Clorg separat.

Därtill finns ett antal troligen viktiga indikationer som skulle behöva bekräftas av ytterligare studier. Dessa inkluderar att:

  • Det sker ett snabbt och omfattande upptag av Cl av organismer och klor tycks ackumuleras i grön växtbiomassa. En stor andel av den totala klormängden i avrinningsområden (upp till 60% i en studie) har påträffats i den terrester biomassa.
  • Avgång av flyktiga klorerade kolväten kan vara en stor okänd exportväg för klor från ekosystem.
  • En del Clorg verkar vara betydligt mer motståndskraftigt mot nedbrytning än det genomsnittliga organiska materialet. Detta kan leda till att Clorg bevaras selektivt i mark och därmed också mindre tillgängligt för mikroorganismer.
  • Det sker en klorering av organiskt material i levande biomassa och klor kan ansamlas som klorerade fettsyror i organismer.

Övriga aspekter på klor i naturen är till stora delar okända. Centrala okända aspekter inkluderar:

  • Hur klor-förråden utvecklas över tid. Detta är centralt för att förstå förändringar över tid och reglering i förråden.
  • Reglering av klorerings-, deklorerings- och transportprocesser, samt hur dessa påverkas av olika miljövariabler och miljöförhållanden.
  • Den ekologiska förklaringen till varför så många organismer utför klorering av organiskt material.
  • Omsättning av klor i akvatiska system. Här saknas separata data gällande Cl– och Clorg både i sediment och i vattenfasen.

 

Rapporten fokuserar framför allt på terrestra aspekter av klorcykeln och innehåller också information om vanliga metoder för mätning av olika klorföreningar.

Place, publisher, year, edition, pages
Stockholm: Swedish Nuclear Fuel and Waste Management Co, 2013. p. 46
Series
Technical Report, ISSN 1404-0344 ; TR-13-26
Keywords
biogeochemistry, chlorine, natural organochlorines, radioactive waste, nuclear energy, biogeokemi, klor, naturliga klororganiska föreningar, radioaktivt avfall, kärnenergi
National Category
Environmental Sciences Geochemistry Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:liu:diva-106653 (URN)
Available from: 2014-05-17 Created: 2014-05-17 Last updated: 2018-10-05Bibliographically approved
Svensson, T., Högbom, L., Johansson, K. & Ring, E. (2013). Effects of previous nitrogen addition on chlorine in forest soil, soil solution and biomass. Biogeochemistry, 116(1-3), 3-13
Open this publication in new window or tab >>Effects of previous nitrogen addition on chlorine in forest soil, soil solution and biomass
2013 (English)In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 116, no 1-3, p. 3-13Article in journal (Refereed) Published
Abstract [en]

There is increasing evidence that forests and forest soil contribute to the signature of chlorine composition in water bodies. However, little is known about the potential effects of land management activities on chlorine biogeochemistry. This study examines the effects of previous nitrogen addition on chlorine chemistry in a Pinus sylvestris L. forest located in south-central Sweden (60°00′N, 13°43′E). Repeated addition of nitrogen to study plots over a 20-year period resulted in total additions of 0, 450 and 900 kg N ha−1. Soil samples were collected before harvesting, and soil solution and biomass were sampled following final felling. Contrary to previous findings, we found no clear evidence that previous addition of nitrogen had hampered the formation of organic chlorine in the organic soil layer. We suggest that the effects of nitrogen addition on chlorination processes are not seen in the surface soil, but are instead manifested in the migration of organic matter in the mineral soil. Soil organic matter from the E-horizon had a lower chlorination degree in the nitrogen-amended plots than in the control plots. In addition, we observed lower Cl levels in the seedling needles following high nitrogen fertilization (900 N) than in 450 N or control. These results add on the importance of studying chlorine dynamics with focus on what chlorinated soil organic matter can be resistant to degradation compared to average soil organic matter and what can be leached as a result of harvesting and available for vegetation.

Keywords
Chlorine, Chloride, Soil, Soil solution, Nitrogen, Forest
National Category
Natural Sciences Soil Science
Identifiers
urn:nbn:se:liu:diva-102636 (URN)10.1007/s10533-013-9888-3 (DOI)000328197800002 ()
Funder
Swedish Research Council Formas
Available from: 2013-12-17 Created: 2013-12-17 Last updated: 2017-12-06Bibliographically approved
Pickering, L., Black, A., Gilbert, C., Jeronimo, M., Nesic, Z., Pilz, J., . . . Öberg, G. (2013). Portable Chamber System for Measuring Chloroform Fluxes from Terrestrial Environments – Methodological Challenges. Environmental Science and Technology, 47(24), 14298-14305
Open this publication in new window or tab >>Portable Chamber System for Measuring Chloroform Fluxes from Terrestrial Environments – Methodological Challenges
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2013 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, no 24, p. 14298-14305Article in journal (Refereed) Published
Abstract [en]

This study describes a system designed to measure chloroform flux from terrestrial systems, providing a reliable first assessment of the spatial variability of flux over an area. The study takes into account that the variability of ambient air concentrations is unknown. It includes quality assurance procedures, sensitivity assessments, and testing of materials used to ensure that the flux equation used to extrapolate from concentrations to fluxes is sound and that the system does not act as a sink or a source of chloroform. The results show that many materials and components commonly used in sampling systems designed for CO2, CH4, and N2O emit chloroform and other volatile chlorinated compounds (VOCls) and are thus unsuitable in systems designed for studies of such compounds. To handle the above-mentioned challenges, we designed a system with a non-steady-state chamber and a closed-loop air-circulation unit returning scrubbed air to the chamber. Based on empirical observations, the concentration increase during a deployment was assumed to be linear. Four samples were collected consecutively and a line was fitted to the measured concentrations. The slope of the fitted line and the y-axis intercept were input variables in the equation used to transform concentration change data to flux estimates. The soundness of the flux equation and the underlying assumptions were tested and found to be reliable by comparing modeled and measured concentrations. Fluxes of chloroform in a forest clear-cut on the east coast of Vancouver Island, BC, during the year were found to vary from −130 to 620 ng m–2 h–1. The study shows that the method can reliably detect differences of approximately 50 ng m–2 h–1 in chloroform fluxes. The statistical power of the method is still comparatively strong down to differences of 35 ng m–2 h–1, but for smaller differences, the results should be interpreted with caution.

Keywords
chloroform, soil-atmosphere, flux, VOCl, chamber, spatial
National Category
Soil Science Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:liu:diva-102640 (URN)10.1021/es403062c (DOI)000328796900048 ()
Funder
Formas, 2009-217
Available from: 2013-12-17 Created: 2013-12-17 Last updated: 2017-12-06
Svensson, T., Lovett, G. & Likens, G. E. (2012). Is chloride a conservative ion in forest ecosystems?. Biogeochemistry, 107(1-3), 125-134
Open this publication in new window or tab >>Is chloride a conservative ion in forest ecosystems?
2012 (English)In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 107, no 1-3, p. 125-134Article in journal (Refereed) Published
Abstract [en]

Chloride (Cl-) has often been assumed to be relatively unreactive in forest ecosystems, and is frequently used as a conservative tracer to calculate fluxes of water and other ions. Recently, however, several studies have detailed cycling of Cl- in vegetation and soils. In this study Cl- budgets are compiled from 32 catchment studies to determine the extent to which Cl- is conserved in the passage through forest ecosystems. Chloride budgets from these sites vary from net retention (input/output) to net release (output/input). In the overall data set, including those sites with very high inputs of seasalt Cl-, there was a strong correspondence between inputs and outputs. However, sites with low Cl- deposition (<6 kg ha-1 year-1) consistently showed net release of Cl-, suggesting an internal source or a declining internal pool. The results indicate that Cl- may be a conservative ion in sites with high Cl- deposition, but in sites with low deposition Cl- may not be conservative. We discuss the possible causes of the Cl- imbalance and reasons why Cl- may not be conservative in ecosystem functions.

Place, publisher, year, edition, pages
Springer, 2012
Keywords
Catchment, Chloride, Chlorine, Mass balance, Soil, Tracer, Watershed
National Category
Environmental Sciences
Identifiers
urn:nbn:se:liu:diva-71914 (URN)10.1007/s10533-010-9538-y (DOI)000298226700009 ()
Note

funding agencies|Swedish Foundation for International Cooperation in Research and Education (STINT)||US National Science Foundation| DEB-0342198 DEB-0423259 |Hubbard Brook LTER program||Andrew W. Mellon Foundation||

Available from: 2011-11-09 Created: 2011-11-09 Last updated: 2017-12-08
Gustavsson, M., Karlsson, S., Oeberg, G., Sandén, P., Svensson, T., Valinia, S., . . . Bastviken, D. (2012). Organic Matter Chlorination Rates in Different Boreal Soils: The Role of Soil Organic Matter Content. Environmental Science and Technology, 46(3), 1504-1510
Open this publication in new window or tab >>Organic Matter Chlorination Rates in Different Boreal Soils: The Role of Soil Organic Matter Content
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2012 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, no 3, p. 1504-1510Article in journal (Refereed) Published
Abstract [en]

Transformation of chloride (Cl-) to organic chlorine (Cl-org) occurs naturally in soil but it is poorly understood how and why transformation rates vary among environments. There are still few measurements of chlorination rates in soils, even though formation of Cl-org has been known for two decades. In the present study, we compare organic matter (OM) chlorination rates, measured by Cl-36 tracer experiments, in soils from eleven different locations (coniferous forest soils, pasture soils and agricultural soils) and discuss how various environmental factors effect chlorination. Chlorination rates were highest in the forest soils and strong correlations were seen with environmental variables such as soil OM content and Cl- concentration. Data presented support the hypothesis that OM levels give the framework for the soil chlorine cycling and that chlorination in more organic soils over time leads to a larger Cl-org pool and in turn to a high internal supply of Cl- upon dechlorination. This provides unexpected indications that pore water Cl- levels may be controlled by supply from dechlorination processes and can explain why soil Cl- locally can be more closely related to soil OM content and the amount organically bound chlorine than to Cl- deposition.

Place, publisher, year, edition, pages
American Chemical Society, 2012
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-75467 (URN)10.1021/es203191r (DOI)000299864400030 ()
Note

Funding Agencies|Swedish Research Council (VR)|2006-5387|

Available from: 2012-03-02 Created: 2012-03-02 Last updated: 2018-10-05
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6471-143X

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