Degradation of benzene, toluene, ethylbenzene, m-, p- and o-xylenes (BTEX) and microbial community shifts in soil slurries contaminated with ethanol-gasoline blends (E-blends), containing 10, 50 or 90% (v/v) ethanol (E10, E50 and E90) were studied in soil slurries previously uncontaminated, contaminated by E-blends or ethanol. BTEX originating from E50 degraded fastest whereas from E10 slowest. Among the individual compounds, ethylbenzene degraded fastest (max 30% d(-1)), and o-xylene slowest (min 1% d(-1)) during aerobic conditions in previously not contaminated soils. Previous contamination by E-blends increased BTEX degradation significantly (3-19 times) compared with previously uncontaminated soils, whereas previous contamination with ethanol did not show significant difference in BTEX degradation. At least one type of the E-blends during aerobic conditions had a positive effect on total PLFAs (phospholipid fatty acids) and specific PLFAs, i.e. 10Me18:0, 16:1w6 and cy17:0, but had a negative effect on cy19:0 and 18:2w6,9c. The effects on total PLFAs, as well as the individual PLFAs, were particularly strong after repeated contamination. The single most affected PLFA was 16:1w6, which increased 23 times during E10 treatment in soil slurries previously contaminated by E-blends. Altogether, the various E-blends had significantly different effects on BTEX degradation and also on individual PLFAs under aerobic conditions.

Observed sorption and chromatographic behaviour served as a starting point for the examination of four ether derivatives of the flame retardant tetrabromobisphenol A (TBBPA): dihydroxyethyl (DHEE), dimethyl (DMe), diallyl (DAE) and dibromopropyl (DBPE). To date, there is little or no information about these compounds in the scientific literature. The targets in the present study had calculated log K-ow values of 6.0-10. A broad range of different types of solvents were used in order to elucidate the mechanisms of sorption onto silica (glass) and two solid phase extraction cartridges based on polystyrene divinylbenzene polymers, hydroxylated (Isolute ENV+) and vinylpyrrolidone (Oasis HLB) containing units. Also, three chromatographic columns (C18, C8 and dual C18-based, i.e. a polar ligand together with C18 on a silica surface) were evaluated. The following were observed: desorption of the targets from silica surface by 1-propanol showed the best results and the yields were further improved by silylation of the surface. Regardless of the experimental test conditions applied, the lowest recovery was seen for the DMe derivative, followed by TBBPA itself, which had calculated log K-ow values in between the other targets. A washing solution containing up to 70% methanol could be used without elution of the targets from the solid phase extraction cartridge. The dihydroxethyl ether derivative of TBBPA is most probably not affected by environmental relevant pH due to a likely high pK(a) (ca 15). Also, this study shows that the polar character of the dual-phase column was not as pronounced as asserted by the manufacturer.

Plastics debris in the marine environment, including resin pellets, fragments and microscopic plastic fragments, contain organic contaminants, including polychlorinated biphenyls ( PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane, hexachlorinated hexanes), polybrominated diphenylethers, alkylphenols and bisphenol A, at concentrations from sub ng g(-1) to mg g(-1). Some of these compounds are added during plastics manufacture, while others adsorb from the surrounding seawater. Concentrations of hydrophobic contaminants adsorbed on plastics showed distinct spatial variations reflecting global pollution patterns. Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride. Both a mathematical model using equilibrium partitioning and experimental data have demonstrated the transfer of contaminants from plastic to organisms. A feeding experiment indicated that PCBs could transfer from contaminated plastics to streaked shearwater chicks. Plasticizers, other plastics additives and constitutional monomers also present potential threats in terrestrial environments because they can leach from waste disposal sites into groundwater and/or surface waters. Leaching and degradation of plasticizers and polymers are complex phenomena dependent on environmental conditions in the landfill and the chemical properties of each additive. Bisphenol A concentrations in leachates from municipal waste disposal sites in tropical Asia ranged from sub mu g l(-1) to mg l(-1) and were correlated with the level of economic development.

A landfill typically progresses through a series of microbial degradation phases, in which hydrolysis, production and consumption of fermentation products, such as fatty acids, and methane formation play important roles. For ultimate degradation of the waste, stable methanogenic conditions have to be attained, and maintained for sufficient time. Using experimental data from 100-L landfill simulation reactors containing municipal solid waste from a residential area, a distributed model, which accounts for vertical water flow, was developed. As a first step, the waste was divided into two fractions: readily degradable and recalcitrant waste. Secondly, the general hydrolysis of the recalcitrant waste was accounted for by including a specific, well-defined chemical substance in the model that generally occurs in Municipal Solid Waste (MSW) and is hydrolysed before its further degradation to methane. For this purpose we chose diethyl phthalate and its hydrolysis product monoethyl phthalate, for which leachate data are available from the reactors. The model indicated that inhibition of the hydrolytic and methanogenic processes occurred during the acidogenic phase and that it could be overcome either by improving the chemical environment or by the complete oxidation of the inhibiting, i.e. the easily degraded, fraction of the waste. The generality of the model was confirmed by the patterns of the phthalate di- and monoester transformations obtained. The validity of the model was further confirmed using experimental data from parallel reactors, which were subjected to either leachate exchange with an already methanogenic reactor or to initial aeration to force the reactor into stable methanogenic conditions. © Springer 2006.

Experimental data from a study using a landfill simulation reactor were used to develop and calibrate a one-dimensional distributed model of co-digestion of municipal solid waste and three phthalic acid diesters with different water solubilities. The three diesters were diethyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate. Two types of municipal solid wastes were assumed, easily degradable and recalcitrant. The model considered inhibition of hydrolysis of the recalcitrant fraction and phthalic acid esters, and also methanogenesis at acidic pH. The results indicated that the prolonged steady-state concentrations of the diesters in the leachates could be explained by equilibrium between physicochemical desorption and sorption processes for the three diesters. When methanogenic conditions were induced in the acidogenic landfill simulation reactor, inhibition of both hydrolysis of recalcitrant MSW and of phthalic acid esters ceased.

Phthalates such as dimethyl phthalate, dimethyl terephthalate (DMT), diethyl phthalate (DEP), di(2-ethylhexyl) phthalate and mono(2-ethylhexyl) phthalate (MEHP) are degraded to varying degrees under anaerobic conditions in waste treatment systems. Here we kinetically analyse the enzymatic hydrolyses involved and the subsequent stoichiometric reactions. The resulting model indicates that the degradation of the alcohols released and the transformation of the phthalic acid (PA) result in biphasic kinetics for the methane formation during transformation of DMT, DEP and MEHP. The ester hydrolysis and the PA transformation to methane appear to be the two rate-limiting steps. The PA-fermenting bacteria, which have biomass-specific growth rates between 0.04 and 0.085 day⁻¹, grow more slowly than the other bacteria involved. Anaerobic microorganisms that remove intermediate products during phthalic acid ester conversion appear to be important for the efficiency of the ultimate phthalate degradation and to be inhibited by elevated hydrogen partial pressures. The model was based on (and the simulations corresponded well with) data obtained from experimental waste treatment systems.

Experimental data from a study using landfill simulation reactor were used to develop and calibrate a one-dimensional distributed model of co-digestion of municipal solid waste and three phthalic acid diesters with different water solubilities to their corresponding monoesters. The three diesters were diethyl phthalate (DEP), dibutyl phthalate (DBP), and di-2-ethylhexyl phthalate (DEHP). Two types of municipal solid wastes were assumed, easily degradable and recalcitrant. The model considered inhibition of hydrolysis of the recalcitrant fraction and phthalic acid esters, and also methanogenesis at acidic pH. The results indicated that the prolonged steady-state concentrations of the diesters in the leachates could be explained by equilibrium between physicochemical desorption and sorption processes giving desorption/sorption ratios of 0.26, 0.003, and 9∙10-5 for DEP, DBP, and DEHP, respectively. When methanogenic conditions were induced in the acidogenic landfill simulation reactor, both the inhibition of hydrolysis of recalcitrant MSW and biodegradation of phthalic acid esters ceased

Phthalic acid diesters are present in a variety of different products and may leach from these products, as they are not chemically bound the resin matrix. The alcohol moieties of the diesters comprise of one or several carbon atoms and thereby the diesters cover a broad range of different physico-chemical behaviours, e.g. solubility. Also, the different products into which they are originally added differ from each other, e.g. from liquid fragrances to rigid polyvinyl chloride (PVC) plastics. The diesters may be degraded to their corresponding monoester and further to phthalic acid. This topic presents an up to date summary of how concentrations of both diesters and monoesters of phthalic acid, as well as phthalic acid itself, vary in leachates from landfill simulation reactors and young full-scale landfill cells, both developing from acidogenic to methanogenic conditions. It also discuss the concentrations of phthalates observed in groundwater samples down-stream an unlined landfill with respect to the results observed from acute toxicity tests with different aquatic species. The release and degradation of the diesters in landfills are dependent on the properties of both the diesters and the resin matrix. In landfills, the most water-soluble diesters are leached from waste to a higher extent than the less water-soluble, but they are only degraded/transformed to their corresponding monoesters and further to phthalic acid by methanogenic bacteria. Therefore, concentrations of these diesters decrease in leachates as the landfill develop methanogenic conditions. The concentrations of total organic carbon in leachates from landfill simulation reactors follow the pattern of the diesters, showing that a general degradation of organic material takes place during establishment of methanogenic conditions. Modelling confirms and explains the transformation processes studied in landfill simulation reactors. A landfill with no or unsatisfactory liner may contaminate the under-laying aquifer as the leachate penetrates the soil. Phthalates have shown to be potential groundwater contaminants, but also that they may be degraded within the leachate plume down-stream an unlined landfill.

In order to investigate phthalates in landfill leachates, four landfill simulation reactors, filled with municipal solid waste from a housing area, were studied. Plasticised polyvinyl chloride (PVC) was added to two of the reactors. Two reactors, one with and one without the additional PVC, were aerated for 3 months to achieve methanogenic conditions. The other two became acidogenic a few days after filling and closing. After approximately 3 years, the acidogenic waste became methanogenic. The leachates were analysed for phthalic acid diesters and their degradation products, phthalic acid monoesters and o-phthalic acid. The occurrence of monobenzyl phthalate (MbenzP) and mono(2-ethylhexyl) phthalate (MEHP) showed that the diesters, butylbenzyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP), released from the PVC products had been transformed, and that they were not completely sorbed to particles or to the waste material. Monoesters were observed once methanogenic conditions were established. The monoesters and phthalic acid were present in concentrations several orders of magnitude higher than the diesters themselves. Our results show that it is important to include monoesters in studies of the fate of diesters. To date, monoesters have been neglected in investigations of organic pollutants in landfill leachates.

Leachates from 17 different landfills in Europe were analysed with respect to phthalates, i.e. phthalic acid diesters (PAEs) and their degradation products phthalic acid monoesters (PMEs) and ortho-phthalic acid (PA). Diesters are ubiquitous and the human possible exposure and potential to human health and environment has put them in focus. The aim of this study was to elucidate whether monoesters and phthalic acid could be traced in landfill leachates and in what concentrations they may be found. The results showed that phthalates were present in the majority of the leachates investigated. The monoesters appeared from 1 to 20 μg/L and phthalic acid 2–880 μg/L (one divergent value of 19 mg phthalic acid/L). Their parental diesters were observed from 1 to 460 μg/L. These observed occurrences of degradation products, of all diesters studied, support that they are degraded under the landfill conditions covered by this study. Thus, we have presented strong evidences to conclude that microorganisms in landfills degrade diesters released from formulations in a variety of products, including polyvinyl chloride (PVC) species.