Determination of selected fate and aquatic toxicity characteristics of acrylic acid and a series of acrylic esters

Acrylic acid, methyl acrylate, ethyl acrylate, and butyl acrylate are commercially important and widely used materials. This paper reports the results of a series of fate and aquatic toxicity studies. The mobility in soil of acrylic acid and its esters ranged from 'medium' to 'very high'. Calculated bioconcentration factors ranged from 1 to 37, suggesting a low bioconcentration potential. Acrylic acid and methyl acrylate showed limited biodegradability in the five day biochemical oxygen demand (BOD5) test, while ethyl acrylate and butyl acrylate were degraded easily (77% and 56%, respectively). Using the OECD method 301D 28-d closed bottle test, degradability for acrylic acid was 81% at 28 days, while the acrylic esters ranged from 57% to 60%. Acrylic acid degraded rapidly to carbon dioxide in soil (t1/2 < 1 day). Toxicity tests were conducted using freshwater and marine fish, invertebrates, and algae. Acrylic acid effect concentrations for fish and invertebrates ranged from 27 to 236 mg/l. Effect concentrations (LC50 or EC50) for fish and invertebrates using methyl acrylate, ethyl acrylate, and butyl acrylate ranged from 1.1 to 8.2 mg/l. The chronic MATC for acrylic acid with Daphnia magna was 27 mg/l based on length and young produced per adult reproduction day and for ethyl acrylate was 0.29 mg/l based on both the reproductive and growth endpoints. Overall these studies show that acrylic acid and the acrylic esters studied can rapidly biodegrade, have a low potential for persistence or bioaccumulation in the environment, and have low to moderate toxicity.     

Biodegradation of petroleum hydrocarbon vapors: laboratory studies on rates and kinetics in unsaturated alluvial sand

Predictions of natural attenuation of volatile organic compounds (VOCs) in the unsaturated zone rely critically on information about microbial biodegradation kinetics. This study aims at determining kinetic rate laws for the aerobic biodegradation of a mixture of 12 volatile petroleum hydrocarbons and methyl tert-butyl ether (MTBE) in unsaturated alluvial sand. Laboratory column and batch experiments were performed at room temperature under aerobic conditions, and a reactive transport model for VOC vapors in soil gas coupled to Monod-type degradation kinetics was used for data interpretation. In the column experiment, an acclimatization of 23 days took place before steady-state diffusive vapor transport through the horizontal column was achieved. Monod kinetic parameters Ks and vmax could be derived from the concentration profiles of toluene, m-xylene, n-octane, and n-hexane, because substrate saturation was approached with these compounds under the experimental conditions. The removal of cyclic alkanes, isooctane, and 1,2,4-trimethylbenzene followed first-order kinetics over the whole concentration range applied. MTBE, n-pentane, and chlorofluorocarbons (CFCs) were not visibly degraded. Batch experiments suggested first-order disappearance rate laws for all VOCs except n-octane, which decreased following zero-order kinetics in live batch experiments. For many compounds including MTBE, disappearance rates in abiotic batch experiments were as high as in live batches indicating sorption. It was concluded that the column approach is preferable for determining biodegradation rate parameters to be used in risk assessment models.     

Testing the ecotoxicology of vegetable versus mineral based lubricating oils: 1. Degradation rates using tropical marine microbes

Vegetable-derived lubricants (VDL) might be more biodegradable than mineral-derived lubricants (MDL) due to the absence of high molecular weight aromatics, but this remains largely untested in tropical conditions. In this laboratory study, the degradation rates of 2-stroke, 4-stroke and hydraulic VDLs were compared with their MDL counterparts in the presence of mangrove and coral reef microbial communities. While MDLs were comprised largely of unresolved saturated and some aromatic hydrocarbons, their VDL counterparts contained, potentially more degradable, fatty acid methyl esters. Degradation of some VDL was observed by day 7, with the 2-stroke VDL markedly consumed by mangrove microorganisms and the hydraulic VDL degraded by both microorganism communities after this short period. All of the VDL groups were significantly more degraded than the comparable MDLs mineral oil lubricants over 14 days in the presence of either mangrove or coral reef microbial communities. In general the mangrove-sourced microorganisms more efficiently degraded the lubricants than reef-sourced microorganisms.     

Biodegradation of potential diesel oxygenate additives: dibutyl maleate (DBM), and tripropylene glycol methyl ether (TGME)

The addition of oxygen-bearing compounds to diesel fuel considerably reduces particulate emissions. TGME and DBM have been identified as possible diesel additives based on their physicochemical characteristics and performance in engine tests. Although these compounds will reduce particulate emissions, their potential environmental impacts are unknown. As a means of characterizing their persistence in environmental media such as soil and groundwater, we conducted a series of biodegradation tests of DBM and TGME. Benzene and methyl tertiary butyl ether (MTBE) were also tested as reference compounds. Primary degradation of DBM fully occurred within 3 days, while TGME presented a lag phase of approximately 8 days and was not completely degraded by day 28. Benzene primary degradation occurred completely by day 3 and MTBE did not degrade at all. The total mineralized fractions of DBM and TGME achieved constant values as a function of time of approximately 65% and approximately 40%, respectively. Transport predictions show that, released to the environment, DBM and TGME would concentrate mostly in soils and waters with minimal impact to air. From an environmental standpoint, these results combined with the transport predictions indicate that DBM is a better choice than TGME as a diesel additive.     

Fate of isoxaben in a containerized plant rhizosphere system

Commercial production of ornamental plants is an important industry in the United States and involves a complex technology that includes the use of herbicides. Isoxaben[N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide] is a pre-emergence herbicide used for controlling weeds in many areas including containerized ornamental plants. Degradation was studied in potting mix (80% bark, 20% sand) with three different regimes (sterile, bulk and rhizosphere). The rhizosphere regime contained Switch Grass (Panicum virgatum), and plants were allowed to grow for 14 days before adding isoxaben (10 microg/g potting mix). Isoxaben was degraded to 0.5 microg/g in 60 days giving a half-life of 7 days. Two degradation products were detected: 3-nitrophthalic acid in the rhizosphere and bulk regimes and 4-methoxyphenol in the sterile regime. Microbial population shifts were determined by fatty acid methyl ester profile analysis and were influenced by the introduction of a plant (rhizosphere regime) and by isoxaben addition.     

Aerobic biodegradation of vinyl chloride and cis-1,2-dichloroethylene in aquifer sediments

Laboratory batch experiments have been performed with sediment and groundwater obtained from two sites in Denmark to study the aerobic biodegradation of vinyl chloride (VC) and cis-1,2-dichloroethylene (c-1,2-DCE) to assess the natural aerobic biodegradation potential at two sites. The experiments revealed that VC was degraded to below the detection limit within 204 and 57 days at the two sites. c-1,2-DCE was also degraded in the experiments but not completely. At the two sites 50% and 35% was removed by the end of the experimental period of 204 and 274 days. The removal of c-1,2-DCE seems to occur concomitantly with VC indicating that the biodegradation of c-1,2-DCE may depend on the biodegradation of VC. However, in both cases natural groundwater was mixed with sediment and consequently there may be other compounds (e.g. ammonium, natural organic compound etc.) that serves as primary substrates for the co-metabolic biodegradation of c-1,2-DCE. At one of the sites methane was supplied to try to enhance the biodegradation of VC and c-1,2-DCE. That was successful since the time for complete biodegradation of VC decreased from 204 days in the absence of methane to 84 days in the presence of methane. For c-1,2-DCE the amount that was biodegraded after 204 days increased from 50% to 90% as a result of the addition of methane. It seems like a potential for natural biodegradation exists at least for VC at these two sites and also to some degree for c-1,2-DCE.     

Development of an environmentally benign process for the production of fatty acid methyl esters

The production of fatty acid methyl esters (FAME) is an important intermediate step in oleochemistry. The oleochemical production route starts with the renewable raw materials fat and oil and ends at fatty alcohols and different special products. Fatty acid methyl esters can be formed at mild reaction temperatures by transesterification of natural triglycerides (fats and oils). This contribution will show the development of a continuous process which is considering the main principles of production integrated environmental protection. The main advantages of this process are low energy consumption and minimal waste production. The process alternatives are shown and a scope on future problems which have to be solved to reach a real additional improvement of the fatty acid methyl esters production is given.     

Measuring the biodegradability of nonylphenol ether carboxylates, octylphenol ether carboxylates, and nonylphenol

We examined the biodegradability of several metabolites of C8- and C9-alkylphenol ethoxylates, including nonylphenoxyacetic acid (NPEC1), nonylphenoxyethoxyacetic acid (NPEC2), octylphenoxyacetic acid (OPEC1), octylphenoxyethoxyacetic acid (OPEC2), and nonylphenol (NP). Using OECD method 301B (modified Sturm method), OPEC1 and OPEC2 are readily biodegradable: both compounds exceeded 60% of theoretical CO2 formation (ThCO2) by day 28, and required less than 10 days to go from 10% to 60% ThCO2. Also using method 301B, NPEC1 and NPEC2 exceeded 60% ThCO2 at day 28, but did not meet the 10 day window. Using OECD method 301F, the manometric respirometry method that measures oxygen consumption, approximately 62% of NP was biodegraded in 28 days, but required more than 10 days to go from 10% to 60% biodegradation. While the validity of the "10-day window" is currently being debated within OECD, the data show that the common metabolites of C8- and C9-APEs are rapidly degraded in the test systems used, which strongly suggests that they would not accumulate or persist in the environment.     

Polymers and surfactants on the basis of renewable resources

A new strategy for the preparation of different polymers and special surfactants was developed. First, unsaturated fatty acid methyl esters obtained from plant oils were converted to terminally unsaturated esters and alpha-olefins by metathesis with ethylene using heterogeneous rhenium or homogeneous ruthenium catalysts. These esters were directly copolymerized with ethylene by an insertion-type palladium-catalyzed polymerization to functionalized polyolefins. Polyesters were synthesized by metathetical dimerization of omega-unsaturated esters and subsequent polycondensation of the produced internally unsaturated dicarboxylic esters or by acidic transesterification with petrochemical diols and additional acyclic diene metathesis polymerization. Omega-epoxy fatty acid methyl esters, achieved by a new method of chemo-enzymatic epoxidation, were converted into polyethers with comb-structure catalyzed by aluminoxanes on the one hand and into sugar surfactants by nucleophilic ring-opening with amino carbohydrates on the other hand.     

Designing green plasticizers: influence of molecular geometry on biodegradation and plasticization properties

The plasticizer di (2-ethylhexyl) phthalate (DEHP) and its metabolites are considered ubiquitous contaminants, which have a range of implications on the environment and human health. This work considered several alternative compounds with structural features similar to DEHP. This added to the understanding of why DEHP is so poorly biodegraded once it enters the environment. These alternative compounds were based on 2-ethylhexyl diesters of maleic acid (cis-isomer), fumaric acid (trans-isomer) and succinic acid (saturated analogue). The rates of biodegradation by the common soil bacterium Rhodococcus rhodocrous were shown to be dependent on the structure of the central unit derived from the diacid used to make the ester. The diacid components of DEHP and the maleate both had a cis orientation and they were the two that were slow to biodegrade. Plasticizing properties were also compared and, because the ester of the saturated succinic acid was degraded quickly and also had good plasticizing properties, it was concluded that the succinic esters of straight chain alcohols would make the best green plasticizers. The maleate ester had excellent plasticizing properties but this is mitigated by a significant resistance to biodegradation.     

Biological degradation of triclocarban and triclosan in a soil under aerobic and anaerobic conditions and comparison with environmental fate modelling

Triclocarban and triclosan are two antimicrobial agents widely used in many personal care products. Their biodegradation behaviour in soil was investigated by laboratory degradation experiments and environmental fate modelling. Quantitative structure-activity relationship (QSAR) analyses showed that triclocarban and triclosan had a tendency to partition into soil or sediment in the environment. Fate modelling suggests that either triclocarban or triclosan "does not degrade fast" with its primary biodegradation half-life of "weeks" and ultimate biodegradation half-life of "months". Laboratory experiments showed that triclocarban and triclosan were degraded in the aerobic soil with half-life of 108 days and 18 days, respectively. No negative effect of these two antimicrobial agents on soil microbial activity was observed in the aerobic soil samples during the experiments. But these two compounds persisted in the anaerobic soil within 70 days of the experimental period.     

Laboratory evidence of MTBE biodegradation in Borden aquifer material

Mainly due to intrinsic biodegradation, monitored natural attenuation can be an effective and inexpensive remediation strategy at petroleum release sites. However, gasoline additives such as methyl tert-butyl ether (MTBE) can jeopardize this strategy because these compounds often degrade, if at all, at a slower rate than the collectively benzene, toluene, ethylbenzene and the xylene (BTEX) compounds. Investigation of whether a compound degrades under certain conditions, and at what rate, is therefore important to the assessment of the intrinsic remediation potential of aquifers. A natural gradient experiment with dissolved MTBE-containing gasoline in the shallow, aerobic sand aquifer at Canadian Forces Base (CFB) Borden (Ontario, Canada) from 1988 to 1996 suggested that biodegradation was the main cause of attenuation for MTBE within the aquifer. This laboratory study demonstrates biologically catalyzed MTBE degradation in Borden aquifer-like environments, and so supports the idea that attenuation due to biodegradation may have occurred in the natural gradient experiment. In an experiment with batch microcosms of aquifer material, three of the microcosms ultimately degraded MTBE to below detection, although this required more than 189 days (or >300 days in one case). Failure to detect the daughter product tert-butyl alcohol (TBA) in the field and the batch experiments could be because TBA was more readily degradable than MTBE under Borden conditions.     

Identification of single cultured micro-organisms based on their whole-community fatty acid profiles, using an extended extraction procedure.

Fatty acid profiles obtained from single cultured organisms have been used to estimate which taxonomic groups are actually represented. The lipid extraction was modified to liberate fatty acids with ester-linkages, as well as those with non-ester-linkages and classify them in different chemically relevant groups. The discriminatory power of fatty acids, in different chemically relevant fractions and subfractions varied considerably. Saturated fatty acids were least able to predict actual group membership (ca. 75%), while nonester-linked hydroxy fatty acids, which largely go undetected by the simple extraction procedure, gave the highest predictability values (ca. 94%). The discriminatory power of the method used was enhanced by increasing the number of well-defined fatty acid methyl esters. The estimation capacity of the results was improved, when the fatty acids, which were presumed to be common and widespread, were excluded from the whole-community fatty acid profiles prior to multivariate analysis.     

Ageing processes and soil microbial community effects on the biodegradation of soil C-2,4-D nonextractable residues

The biodegradation of nonextractable residues (NER) of pesticides in soil is still poorly understood. The aim of this study was to evaluate the influence of NER ageing and fresh soil addition on the microbial communities responsible for their mineralisation. Soil containing either 15 or 90-day-old NER of ¹³C-2,4-D (NER15 and NER90, respectively) was incubated for 90 days with or without fresh soil. The addition of fresh soil had no effect on the mineralisation of NER90 or of SOM, but increased the extent and rate of NER15 mineralisation. The analyses of ¹³C-enriched FAME (fatty acids methyl esters) profiles showed that the fresh soil amendment only influenced the amount and structure of microbial populations responsible for the biodegradation of NER15. By coupling biological and chemical analyses, we gained some insight into the nature and the biodegradability of pesticide NER.     

Biostimulation and bioaugmentation enhances aerobic biodegradation of dichloroethenes

The accumulation of dichloroethenes (DCEs) as dominant products of microbial reductive dechlorination activity in soil and water represent a significant obstacle to the application of bioremediation as a remedial option for chloroethenes in many contaminated systems. In this study, the effects of biostimulation and/or bioaugmentation on the biodegradation of cis- and trans-DCE in soil and water samples collected from contaminated sites in South Africa were evaluated in order to determine the possible bioremediation option for these compounds in the contaminated sites. Results from this study indicate that cis- and trans-DCE were readily degraded to varying degrees by natural microbial populations in all the soil and water samples tested, with up to 44% of cis-DCE and 41% of trans-DCE degraded in the untreated soil and water samples in two weeks. The degradation rate constants ranged significantly (P<0.05) between 0.0938 and 0.560 wk(-1) and 0.182 and 0.401 wk(-1), for cis- and trans-DCE, respectively, for the various treatments employed. A combination of biostimulation and bioaugmentation significantly increased the biodegradation of both compounds within two weeks; 14% for cis-DCE and 18% for trans-DCE degradation, above those observed in untreated soil and water samples. These findings support the use of a combination of biostimulation and bioaugmentation for the efficient biodegradation of these compounds in contaminated soil and water. In addition, the results clearly demonstrate that while naturally occurring microorganisms are capable of aerobic biodegradation of cis- and trans-DCE, biotransformation may be affected by several factors, including isomer structure, soil type, and the amount of nutrients available in the water and soil.     

Reactive transport modeling of processes controlling the distribution and natural attenuation of phenolic compounds in a deep sandstone aquifer

Reactive solute transport modeling was utilized to evaluate the potential for natural attenuation of a contaminant plume containing phenolic compounds at a chemical producer in the West Midlands, UK. The reactive transport simulations consider microbially mediated biodegradation of the phenolic compounds (phenols, cresols, and xylenols) by multiple electron acceptors. Inorganic reactions including hydrolysis, aqueous complexation, dissolution of primary minerals, formation of secondary mineral phases, and ion exchange are considered. One-dimensional (1D) and three-dimensional (3D) simulations were conducted. Mass balance calculations indicate that biodegradation in the saturated zone has degraded approximately 1-5% of the organic contaminant plume over a time period of 47 years. Simulations indicate that denitrification is the most significant degradation process, accounting for approximately 50% of the organic contaminant removal, followed by sulfate reduction and fermentation reactions, each contributing 15-20%. Aerobic respiration accounts for less than 10% of the observed contaminant removal in the saturated zone. Although concentrations of Fe(III) and Mn(IV) mineral phases are high in the aquifer sediment, reductive dissolution is limited, producing only 5% of the observed mass loss. Mass balance calculations suggest that no more than 20-25% of the observed total inorganic carbon (TIC) was generated from biodegradation reactions in the saturated zone. Simulations indicate that aerobic biodegradation in the unsaturated zone, before the contaminant entered the aquifer, may have produced the majority of the TIC observed in the plume. Because long-term degradation is limited to processes within the saturated zone, use of observed TIC concentrations to predict the future natural attenuation may overestimate contaminant degradation by a factor of 4-5.     

Microbial degradation of 17β -estradiol and 17α -ethinylestradiol followed by a validated HPLC-DAD method

This work aimed at studying the biodegradation of two estrogens, 17α -estradiol (E2) and 17β -ethinylestradiol (EE2), and their potential metabolism to estrone (E1) by microbial consortia. The biodegradation studies were followed by High Performance Liquid Chromatography–Diode Array Detector (HPLC–DAD) using a specifically developed and validated method. Biodegradation studies of the estrogens (E2 and EE2) were carried out with activated sludge (consortium A, CA) obtained from a Wastewater Treatment Plant (WWTP) and with a microbial consortium able to degrade recalcitrant compounds, namely fluorobenzene (consortium B, CB). E2 was more extensively degraded than EE2 by CA whereas CB was only able to degrade E2. The addition of acetate as a supplementary carbon source led to a faster biodegradation of E2 and EE2. E1 was detected as a metabolite only during the degradation of E2. The 16S rRNA gene sequence analyses of strains recovered from the degrading cultures revealed the presence of the genera Pseudomonas, Chryseobacterium and Alcaligenes. The genera Pseudomonas and Chryseobacterium were retrieved from cultures supplied with E2 and EE2, while the genus Alcaligenes was found in the presence of E2, suggesting that they might be involved in the degradation of these compounds.     

Genotoxic potential of diesel exhaust particles from the combustion of first- and second-generation biodiesel fuels—the FuelHealth project

Epidemiological data indicate that exposure to diesel exhaust particles (DEPs) from traffic emissions is associated with higher risk of morbidity and mortality related to cardiovascular and pulmonary diseases, accelerated progression of atherosclerotic plaques, and possible lung cancer. While the impact of DEPs from combustion of fossil diesel fuel on human health has been extensively studied, current knowledge of DEPs from combustion of biofuels provides limited and inconsistent information about its mutagenicity and genotoxicity, as well as possible adverse health risks. The objective of the present work was to compare the genotoxicity of DEPs from combustion of two first-generation fuels, 7% fatty acid methyl esters (FAME) (B7) and 20% FAME (B20), and a second-generation 20% FAME/hydrotreated vegetable oil (SHB: synthetic hydrocarbon biofuel) fuel. Our results revealed that particulate engine emissions from each type of biodiesel fuel induced genotoxic effects in BEAS-2B and A549 cells, manifested as the increased levels of single-strand breaks, the increased frequencies of micronuclei, or the deregulated expression of genes involved in DNA damage signaling pathways. We also found that none of the tested DEPs showed the induction of oxidative DNA damage and the gamma-H2AX-detectable double-strand breaks. The most pronounced differences concerning the tested particles were observed for the induction of single-strand breaks, with the greatest genotoxicity being associated with the B7-derived DEPs. The differences in other effects between DEPs from the different biodiesel blend percentage and biodiesel feedstock were also observed, but the magnitude of these variations was limited.     

Biodegradation of phthalate esters during the mesophilic anaerobic digestion of sludge

Phthalic acid esters (PAE) are commonly found in the sludge generated in the wastewater treatment plants. Anaerobic digestion followed by land application is a common treatment and disposal practice of sludge. To date, many studies exist on the anaerobic biodegradation rates of PAE, especially of the easily biodegradable ones, whereas the higher molecular weight PAE have reported to be non-biodegradable under methanogenic conditions. Furthermore, there is no information on the effect of the PAE on the performance of the anaerobic digesters treating sludge. In this study, the anaerobic biodegradation of di-n-butyl phthalate (DBP), di-ethyl phthalate (DEP) and di-ethylhexyl phthalate (DEHP) was investigated and their relative rates of anaerobic degradation were calculated. Also, the biological removal of PAE during the anaerobic digestion of sludge in bench-scale digesters was investigated using DBP and DEHP as model compounds of one biodegradable and one recalcitrant PAE respectively. The degradation of all the PAE tested in this study (DEP, DBP and DEHP) is adequately described by first-order kinetics. Batch and continuous experiments showed that DEP and DBP present in sludge are rapidly degraded under mesophilic anaerobic conditions (a first-order kinetic constant of 8.04 x 10(-2) and 13.69 x 10(-2)-4.35 day(-1) respectively) while DEHP is degraded at a rate between one to two orders of magnitude lower (0.35 x 10(-2)-3.59 x 10(-2) day(-1)). It is of high significance that experiments with anaerobic sludge of different origin (US and Europe) showed that degradation of DEHP occurs under methanogenic conditions. Accumulation of high levels of DEHP (more than 60 mg/l) in the anaerobic digester has a negative effect on DBP and DEHP removal rates as well as on the biogas production.     

Sorption and biodegradation of vapor-phase organic compounds with wastewater sludge and food waste compost

To test the possible use of composted food waste and wastewater sludge as biofilters to treat gas-phase volatile organic compounds (VOCs), batch experiments were conducted with an isolated strain that could degrade aromatic compounds under aerobic conditions. A benzene and trichloroethylene (TCE) mixture was used as the gas-phase pollutant in experiments with composted food waste, sludge, and soil. Under aerobic conditions, benzene was degraded as a primary substrate and TCE was degraded cometabolically, with water contents varying from 6 to 60% (volume of water added/volume of solid). Optimal water content for VOC removal was 12% for the soil, 36% for the composted food waste, and 48% for the sludge. The extent of VOC sorption and biodegradation at the optimal water content was different for each material. With the same initial VOC concentration, more VOCs were removed by sorption onto the composted food waste and the sludge, while less VOCs were biodegraded in comparison with the results using soil. The reason the biodegradation in the soil was greater may be partly attributed to the fact that, due to less sorption, the aqueous-phase concentration of VOCs, which microorganisms could utilize as a carbon source or cometabolize, was higher. We also speculate that the distribution of microorganisms in each medium affects the rate of biodegradation. A large number of microorganisms were attached to the composted food waste and sludge. Mass transfer of VOCs and oxygen to these microorganisms, which appear to have been heterogeneously distributed in clusters, may have been limited, resulting in hindered biodegradation.