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Environmental risk assessment (ERA) methodologies for consumer product chemicals are well established in most developed regions including the United States, Canada, and the European Union. However, such methodologies are not yet fully developed for emerging economies, such as China. The objective of the present study was to develop an ERA framework involving an exposure methodology using conditions specific to China (i.e., physical setting, infrastructure, and consumers' habits and practice). Incorporated in this newly developed ERA framework for assessing consumer product chemicals were China's current regulatory screening and prioritization schemes as part of a tiered risk assessment approach. The framework started with tier 0, which utilized the existing Chinese regulatory qualitative method; tiers 1 and 2 were quantitative, and used deterministic and probabilistic methods that accounted for per capita residential water usage, wastewater treatment capability, and wastewater/in-stream dilution factors. Due to major differences in wastewater treatment infrastructure and water usage between urban versus rural regions in China, 2 scenarios were identified for quantitatively assessing environmental exposure: 1) urban with wastewater treatment, and 2) rural without wastewater treatment (i.e., direct discharge of wastewater). Our study presents the methodology of the framework with its technical rationale and the companion model Chera, and also provides an overview of the current status of ERA research in China. Environ Toxicol Chem 2019;38:250-261. © 2018 SETAC.

Alcohol sulfates (AS), alcohol ethoxysulfates (AES), linear alkyl benzenesulfonates (LAS) and methyl ester sulfonates (MES) are anionic surfactants that are widely used in household detergents and consumer products resulting in over 1 million tons being disposed of down the drain annually in the US. A monitoring campaign was conducted which collected grab effluent samples from 44 wastewater treatment plants (WWTPs) across the US to generate statistical distributions of effluent concentrations for anionic surfactants. The mean concentrations for AS, AES, LAS and MES were 5.03 ± 4.5, 1.95 ± 0.7, 15.3 ± 19, and 0.35 ± 0.13 μg/L respectively. Since each of these surfactants consist of multiple homologues that differ in their toxicity, the concentration of each homologue measured in an effluent sample was converted into a toxic unit (TU) by normalizing to the predicted no effect concentration (PNEC) derived from high tier effects data (mesocosm studies). The statistical distributions of the combined TUs in the effluents were used in combination with distributions of dilution factors for WWTP mixing zones to conduct a US-wide probabilistic risk assessment for the aquatic environment for each of the surfactants. The 90th percentile level of TUs for AS, AES, LAS and MES in mixing zones were 1.89 × 10− 2, 2.73 × 10− 3, 2.72 × 10− 2, and 3.65 × 10− 5 under 7Q10 (lowest river flow occurring over a 7 day period every 10 years) low flow conditions. Because these surfactants have the same toxicological mode of action, the TUs were summed and the aquatic safety for anionic surfactants as a whole was assessed. At the 90th percentile level under the conservative 7Q10 low flow conditions the forecasted TUs were 4.21 × 10− 2 which indicates that there is a significant margin of safety for the class of anionic surfactants in US aquatic environments.

The ultimate disposition of chemicals discarded down the drain can be substantially impacted by their fate in the sewer, but to date limited data have been published on the biodegradability of chemicals in sewer systems. The recently established OECD 314 guideline (Simulation tests to assess the biodegradability of chemicals discharged in wastewater, 2008) contains a simulation method (314A) for evaluating the biodegradation of chemicals in sewage under simulated sewer conditions. This research used the OECD 314A method to evaluate the rates and pathways of primary and ultimate biodegradation of a suite of 14C-labeled homologues representing four classes of high volume surfactants including nonionic alkyl ethoxylates (AE), and anionic alkyl ethoxysulfates (AES), alkyl sulfate (AS) and linear alkyl benzene sulfonate (LAS). All the tested homologues exhibited >97 % loss of parent, formation of metabolites, and some level (16–94 %) of CO2 production after being incubated 96–100 h in raw domestic wastewater. Comparison of C12E3, C14E3, and C16E3 showed that the first order biodegradation rate was affected by alkyl chain length with rates ranging from 6.8 h−1 for C12E3 to 0.49 h−1 for C16E3. Conversely, comparison of C14E1, C14E3, and C14E9 showed that the number of ethoxy units did not impact the biodegradation rate. AES and AS degraded quickly with first order kinetic rates of 1.9–3.7 and 41 h−1 respectively. LAS did not exhibit first order decay kinetics and primary degradation was slow. Biodegradation pathways were also determined. This work shows that biodegradation in the sewer has a substantial impact on levels of surfactants and surfactant metabolites that ultimately reach wastewater treatment plants.

The development of specific regulatory persistence criteria and a growing need to conduct risk assessments in sediment have increased the need to better understand fate in this compartment. A simplified test approach was developed to assess the fate of chemicals in aerobic sediments and used to evaluate the biodegradation of (14) C-labeled representative analogs of alcohol sulfate, alcohol ethoxylate, alcohol ethoxy sulfate, linear alkylbenzene sulfonate, and tetradecanol in 2 different sediments. The method provides kinetic data on primary and ultimate biodegradation in sediments as well as information on biodegradation pathways and metabolites. All test materials exhibited extensive biodegradation in both sediments; disappearance of parent exhibited biphasic kinetics, described by a 2-compartment model, and mineralization was coupled to parent disappearance with little accumulation of metabolites. The first-compartment decay rates ranged from 10.8 d(-1) to 17.1 d(-1) for tetradecanol, 2.54 d(-1) to 24.8 d(-1) for alcohol sulfate, 0.17 d(-1) to 0.75 d(-1) for alcohol ethoxylate, 0.41 d(-1) to 0.71 d(-1) for alcohol ethoxy sulfate, and 0.26 d(-1) to 1.25 d(-1) for linear alkylbenzene sulfonate. These rates corresponded to half-lives ranging from 0.041 d to 4.08 d. This method's simplicity and focus on only sediment-associated processes offer potential benefits over the current Organisation for Economic Co-operation and Development 308 aerobic sediment-water test. Environ Toxicol Chem 2016;35:2199-2208. © 2016 SETAC.

l-Glutamate-N,N-diacetate (L-GLDA) was recently introduced in the United States (U.S.) market as a phosphate replacement in automatic dishwashing detergents (ADW). Prior to introduction, L-GLDA exhibited poor biodegradation in OECD 301B Ready Biodegradation Tests inoculated with sludge from U.S. wastewater treatment plants (WWTPs). However, OECD 303A Activated Sludge WWTP Simulation studies showed that with a lag period to allow for growth (40-50 days) and a solids retention time (SRT) that allows establishment of L-GLDA degraders (15 days), significant biodegradation (80% dissolved organic carbon removal) would occur. Corresponding to the ADW market launch, a study was undertaken to monitor changes in the ready biodegradability of L-GLDA using activated sludge samples from various U.S. WWTPs. Initially all sludge inocula showed limited biodegradation ability, but as market introduction progressed, both the rate and extent of degradation increased significantly. Within 22 months, L-GLDA was ready biodegradable using inocula from 12 WWTPs. In an OECD 303A study repeated 18 months post launch, significant and sustained carbon removal (94%) was observed after a 29-day acclimation period. This study systematically documented field adaptation of a new consumer product chemical across a large geographic region and confirmed the ability of laboratory simulation studies to predict field adaptation.

The risks of 1,4-dioxane (dioxane) concentrations in wastewater treatment plant (WWTP) effluents, receiving primarily domestic wastewater, to downstream drinking water intakes was estimated using distributions of measured dioxane concentrations in effluents from 40 WWTPs and surface water dilution factors of 1323 drinking water intakes across the United States. Effluent samples were spiked with a d8-1,4-dioxane internal standard in the field immediately after sample collection. Dioxane was extracted with ENVI-CARB-Plus solid phase columns and analyzed by GC/MS/MS, with a limit of quantification of 0.30 μg/L. Measured dioxane concentrations in domestic wastewater effluents ranged from

OTNE [1-(1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethyl-2-naphthyl)ethan-1-one; trade name Iso E Super] is a fragrance ingredient commonly used in consumer products which are disposed down the drain. This research measured effluent and sludge concentrations of OTNE at 44 US wastewater treatment plants (WWTP). The mean effluent and sludge concentrations were 0.69 ± 0.65 μg/L and 20.6 ± 33.8 mg/kg dw respectively. Distribution of OTNE effluent concentrations and dilution factors were used to predict surface water and sediment concentrations and distributions of OTNE sludge concentrations and loading rates were used to predict terrestrial concentrations. The 90th percentile concentration of OTNE in US WWTP mixing zones was predicted to be 0.04 and 0.85 μg/L under mean and 7Q10 low flow (lowest river flow occurring over a 7 day period every 10 years) conditions respectively. The 90th percentile sediment concentrations under mean and 7Q10 low flow conditions were predicted to be 0.081 and 1.6 mg/kg dw respectively. Based on current US sludge application practices, the 90th percentile OTNE terrestrial concentration was 1.38 mg/kg dw. The probability of OTNE concentrations being below the predicted no effect concentration (PNEC) for the aquatic and sediment compartments was greater than 99%. For the terrestrial compartment, the probability of OTNE concentrations being lower than the PNEC was 97% for current US sludge application practices. Based on the results of this study, OTNE concentrations in US WWTP effluent and sludge do not pose an ecological risk to aquatic, sediment and terrestrial organisms.

Environmental exposure and associated ecological risk related to down-the-drain chemicals discharged by municipal wastewater treatment plants (WWTPs) are strongly influenced by in-stream dilution of receiving waters which varies by geography, flow conditions and upstream wastewater inputs. The iSTREEM® model (American Cleaning Institute, Washington D.C.) was utilized to determine probabilistic distributions for no decay and decay-based dilution factors in mean annual and low (7Q10) flow conditions. The dilution factors derived in this study are "combined" dilution factors which account for both hydrologic dilution and cumulative upstream effluent contributions that will differ depending on the rate of in-stream decay due to biodegradation, volatilization, sorption, etc. for the chemical being evaluated. The median dilution factors estimated in this study (based on various in-stream decay rates from zero decay to a 1h half-life) for WWTP mixing zones dominated by domestic wastewater flow ranged from 132 to 609 at mean flow and 5 to 25 at low flow, while median dilution factors at drinking water intakes (mean flow) ranged from 146 to 2×10(7) depending on the in-stream decay rate. WWTPs within the iSTREEM® model were used to generate a distribution of per capita wastewater generated in the U.S. The dilution factor and per capita wastewater generation distributions developed by this work can be used to conduct probabilistic exposure assessments for down-the-drain chemicals in influent wastewater, wastewater treatment plant mixing zones and at drinking water intakes in the conterminous U.S. In addition, evaluation of types and abundance of U.S. wastewater treatment processes provided insight into treatment trends and the flow volume treated by each type of process. Moreover, removal efficiencies of chemicals can differ by treatment type. Hence, the availability of distributions for per capita wastewater production, treatment type, and dilution factors at a national level provides a series of practical and powerful tools for building probabilistic exposure models.

Triclosan (TCS; 5-chloro-2-[2,4-dichloro-phenoxy]-phenol) is a widely used antimicrobial agent. To understand its fate during sewage treatment, the biodegradation and removal of TCS were determined in activated sludge. In addition, the effects of TCS on treatment processes were assessed. Fate was determined by examining the biodegradation and removal of TCS radiolabeled with 14C in the 2,4-dichlorphenoxy ring in laboratory batch mineralization experiments and bench-top continuous activated-sludge (CAS) systems. In batch experiments with unacclimated sludge, TCS was mineralized to 14CO2, but the total yield varied as a function of test concentration. Systems that were redosed with TCS exhibited more extensive and faster mineralization, indicating that adaptation was a critical factor determining the rate and extent of biodegradation. In a CAS study in which the influent level of TCS was incrementally increased from 40 microg/L to 2,000 microg/L, removal of the parent compound exceeded 98.5% and removal of total radioactivity (parent and metabolites) exceeded 85%. Between 1.5 and 4.5% of TCS in the influent was sorbed to the wasted solids, whereas >94% underwent primary biodegradation and 81 to 92% was mineralized to CO2 or incorporated in biomass. Increasing levels of TCS in the influent had no major adverse effects on any wastewater treatment process, including chemical oxygen demand, biological oxygen demand, and ammonia removal. In a subsequent experiment, a CAS system, acclimated to TCS at 35 microg/L, received two separate 4-h shock loads of 750 microg/L TCS. Neither removal of TCS nor treatment processes exhibited major adverse effects. An additional CAS study was conducted to examine the removal of a low level (10 microg/L) of TCS. Removal of parent equaled 94.7%, and biodegradation remained the dominant removal mechanism. A subsequent series of CAS experiments examined removal at four influent concentrations (7.5, 11, 20, and 50 microg/L) of TCS and demonstrated that removal of parent ranged from 98.2 to 99.3% and was independent of concentration. Although TCS removal across all experiments appeared unrelated to influent concentration, removal was significantly correlated (r2 = 0.87) with chemical oxygen demand removal, indicating that TCS removal was related to overall treatment efficiency of specific CAS units. In conclusion, the experiments show that TCS is extensively biodegraded and removed in activated-sludge systems and is unlikely to upset sewage treatment processes at levels expected in household and manufacturing wastewaters.

More than 2,100 chemically defined organic chemicals are listed in the Research Institute of Fragrance Materials/Flavor and Extract Manufacturers' Association (RIFM/FEMA) Database that are used as ingredients of fragrances for consumer products. An approach was developed for prioritizing these fragrance materials for aquatic risk assessment by first estimating the predicted environmental concentration (PEC) of these fragrance materials in the aquatic environment based upon their physicochemical properties and annual volume of use. Subsequently, an effect level was predicted with a general quantitative structure-activity relationship (QSAR) for aquatic toxicity, and a predicted no-effect concentration (PNEC) was calculated from this effect level by using an assessment factor (AF) that accounts for uncertainty in the toxicity QSAR prediction. A conservative AF of 10(6) was applied to the endpoint predicted by the QSAR to provide an adequate margin of safety in the calculation of the PNEC. The PEC was compared to the PNEC to characterize the risk to freshwater aquatic organisms (e.g., Daphnia magna and Pimephales promelas). If the ratio of PEC to PNEC was below one, the material was considered to have negligible environmental risk and to be acceptable for the aquatic environment at current use levels. If this ratio exceeded one, the PNEC was refined by using more specific QSAR models (Ecological Structure-Activity Relationships [ECOSAR]). If the ratio continued to exceed one, the material became a candidate for further aquatic risk assessment procedures, which involve iterative steps to refine the PEC, the PNEC, or both by using measured ecotoxicological endpoints. Prioritization for this latter process can be based upon the magnitudes of the estimated PEC:PNEC ratios. When using the first tier of this approach, only 568 of 2,141 fragrance materials (26.5%) in the RIFM/FEMA Database had PEC:PNEC ratios greater than one. This percentage decreased to only 164 materials (7.7%) when PNECs were derived with ECOSAR. Comparison of predicted PECs and PNECs with those based upon measured data confirmed the conservatism and low risk for type I errors associated with the framework. These combined exercises demonstrated the ability of this highly precautionary risk-based screening approach to quickly prioritize a large number of materials without benefit of experimental ecotoxicological or fate data.

The location and activity of esterase enzymes in activated sludge from three municipal wastewater treatment plants were characterized using model substrates and denaturing and non-denaturing polyacrylamide gel electrophoresis (PAGE) of particulate, freeze-thaw (primarily periplasmic enzymes and those associated with outer cell surfaces) and extracellular fractions of activated sludge bacteria. Particulate and freeze-thaw fractions had a similar spectrum of substrate specificity and contained significant levels of protein and esterase activity against model substrates, C2-C18 monoesters of p-nitrophenol and C2-C8 diesters of fluorescein. Esterase activity was highest with substrates that had short alkyl chains (C4) and decreased as the chain lengths increased beyond C8. Extracellular fractions contained very low levels of protein (0.1 mg/l) and showed no esterase activity against any of the model substrates tested. Multiple bands were observed upon analysis of particulate and freeze-thaw fractions by non-denaturing PAGE in combination with activity staining using various alpha-naphthol ester substrates (C2-C8). Our results indicate that esterase enzymes in activated sludge are fairly diverse from a structural standpoint but exhibit a high level of functional redundancy, with different enzymes catalyzing the same reactions in different sludges. Extracellular esterase activity was totally absent for the substrates we tested and the esterase activity that we observed was closely linked to a particulate floc or cellular material.

The white rot fungus Phanerochaete chrysosporium, which generally mineralizes substituted aromatics to CO2, transformed linear alkylbenzene sulfonate (LAS) surfactants mainly at their alkyl side chain. Degradation of LAS was evidenced by a zone of clearing on LAS-containing agar plates and colorimetric analysis of liquid cultures. Disappearance of LAS was virtually complete within 10 days in low nitrogen (2.4 mM N), high nitrogen (24 mM N) and malt extract (ME) liquid media. After 5 days of incubation in ME medium, transformation of LAS was complete at concentrations≤4 mg l-1, but decreased at higher concentrations. The LAS degradation was not dependent on lignin peroxidases (LiPs) and manganese-dependent peroxidases (MnPs). Mineralization of14C-ring-LAS to 14CO2 by P. chrysosporium was

We use a nonsteady-state model to evaluate the effects of community adaptation and sorption kinetics on the fate of linear alkylbenzene sulfonate (LAS) in batch experiments conducted with activated sludge that was continuously fed different concentrations of LAS. We observed a sharp decrease in the biodegradation rate between 30 and 60 minutes and the presence of an LAS residual at the end of the batch experiments. The modeling analysis indicates that these phenomena were caused by relatively slow inter-phase mass transport of LAS. The modeling analyses also showed that the amount of LAS-degrading biomass increased when the continuous activated sludge was fed a higher LAS concentration. Although community adaptation to LAS involved accumulation of more LAS degraders, the increase was not proportional to the feed concentration of LAS, which supports the concept that LAS degraders also utilized portions of the general biochemical oxygen demand (BOD) fed to the continuous activated sludge systems.

The polycyclic musks, AHTN and HHCB are fragrance ingredients widely used in consumer products. A monitoring campaign was conducted and collected grab effluent and sludge samples at 40 wastewater treatment plants (WWTP) across the United States to understand their occurrence and statistical distribution in these matrices. AHTN concentration in effluent ranged from

An in-depth biodegradation test program was executed on the hexadentate ligand Ethylene Diamine Di Succinate (EDDS). The EDDS structure contains two chiral carbon atoms, and has three stereoisomers ([R,R], [R,S]/[S,R], [S,S]). Our research has focused on the isomer mixture (i.e. 25%[S,S]; 25%[R,R]; 50%[S,R]/[R,S], as produced from the reaction of ethylene diamine with maleic anhydride) and on the single [S,S]- and [R,R]-isomers. Biodegradation screening of the 14C-labelled EDDS isomer mixture in a Batch Activated Sludge (BAS) test with various inocula revealed incomplete mineralization, up to ca. 65% after 28 days. N-(2-aminoethyl) aspartic acid (AEAA), probably the d-isomer, was identified as the major portion of the 14C-material remaining in solution. Further testing revealed that the [S,S]-isomer is rapidly and completely mineralized in all test systems. By contrast, [R,R]-EDDS remained undegraded in a Sturm (OECD 301B) test, but was very slowly biotransformed into the recalcitrant metabolite AEAA in a BAS test. The [S,R]/[R,S] form undergoes biotransformation to AEAA in both high and low biomass systems. In a sewage treatment simulation test (OECD 303) the steady state DOC removal of mixture-EDDS in a CAS test was limited to 25-35%, even after extensive pre-acclimation, while the [S,S]-isomer achieved nearly complete removal (96%). This study illustrates the importance stereospecificity may have on the biodegradation and metabolite formation of a chemical. A biodegradation scheme for the different EDDS stereoisomers is proposed.

An approach has been devised for determining the kinetics of primary and ultimate biodegradation of chemicals under realistic conditions in activated sludge. A radiolabeled test chemical is dosed at an environmentally relevant concentration into biotic and abiotic activated sludge. Periodi cally, samples are removed, acidified, and analyzed by LSC to determine 14CO2 evolution. In addition, samples are flash-frozen, lyophilized, and extracted to recover the parent and metabolites, which are analyzed by Rad-TLC. The extracted residue is then sequentially extracted with cold TCA, ethanol/ether, hot TCA, and 10 N NaOH and combusted to determine incorporation into constituents of biomass. Loss of parent, 14CO2 evolution, and incorporation into biomass are fitted to a variety of decay or production functions using nonlinear regression to identify the best models and estimate rates. Linear alkylbenzene sulfonate (14C-ring C12LAS) was tested as model compounds in two sludges. Within 8 h, 41−44% was evolved as 14C...

The objective of this research was to derive empirical extrapolation factors by concurrently measuring mineralization rates of nine diverse chemicals in a Ready CO 2 test (modified Sturm) and realistic 14 C tests using activated sludge, river water, and sludge-amended soil while holding other variables constant. All nine chemicals were mineralized in the Ready test and each of the compartments, but no significant statistical relationships existed between biodegradation rates in the various tests. Mineralization rates in the Ready test were on average 8.1, 2.5, and 1.2 times lower than the rates in realistic activated sludge, river water, and soil tests, but variability in the scaling factors spanned up to 1.5 orders of magnitude. The scaling factors for extrapolating from ready CO 2 data ranged from 1.7 to 19 for activated sludge, from 0.1 to 5.6 for river water, and from 0.3 to 2.8 for soil. Correlation analysis revealed that the scaling factors from the CO 2 test to activated sludge and river water were related to the quantitative structure-activity relationship based solubility and log K ow estimates for the test chemicals.

Tetradecenyl succinic acid (TSA) is the major component of a detergent builder (C12-C14 alkenyl succinic acid), which is inherently biodegradable. 14C-TSA was dosed as a component of sewage sludge into a soil with a history of sludge amendment at final added concentrations of 1.5 and 30 mg (kg soil)-1. In addition, it was dosed to the soil in an aqueous solution to a final added concentration of 30 mg (kg soil)-1. Dose and form were found to have a pronouced effect on the mineralization kinetics. When dosed in a realistic form and concentration (i.e. 1.5 mg (kg soil)-1 as a component of sludge), TSA was mineralized at its highest rate and to its greatest extent, and the mineralization half-life was 2.4 days. When dosed at 30 mg (kg soil)-1 as a component of sludge, mineralization began immediately, and the half-life was 23 days. In contrast, when dosed at this concentration in aqueous solution, the onset of mineralization was preceded by a 13 day lag period and the mineralization half-life was 69 days. Primary biodegradation and mineralization rates of TSA were very similar. Approximately, half the radioactivity was evolved as 14CO2, while the remaining radioactivity became non-extractable, having presumably been incorporated into biomass or natural soil organic matter (humics). This study demonstrated that TSA is effectively removed from sludge-amended soils as a result of biodegradation. Furthermore, it showed the effect that dose form and concentration have on the biodegradation kinetics and the importance of dosing a chemical not only at a relevant concentration but also in the environmental form in which it enters the soil environment.

Physical effects on the microbial colonization and decomposition of plant litter in an oligotrophic lake were studied in Toolik Lake, Alaska. Colonization, measured by adenosine triphosphate (ATP) analysis, and decomposition, measured by weight loss, were correlated with depth of incubation, light, and temperature. The effects of turbulence, light, and temperature were studied in microcosm experiments. A 10°C increase (above ambient) in temperature caused a doubling in the amount of microbial colonization and a 50% increase in decomposition. Light intensity had no quantitative effect on either colonization or decomposition. Turbulence experiments conducted in Toolik Lake showed significant differences in decomposition between natural turbulence and no turbulence. Elevated temperature (20°C, which was 10°C above ambient), high turbulence, and total darkness changed the composition of the litter microbiota, causing a shift from a bacterially dominated microbiota to one dominated by large filamentous forms, as revealed by scanning electron microscopy. This study shows the importance of these physical factors in determining the rate at which plant litter is colonized and degraded in aquatic environments.

This study investigated the interactions between organic chemicals and components of the soil matrix and their effects on subsequent microbial mineralization kinetics. Five 14 C-labeled chemicals (anionic, cationic, and nonionic surfactants) were aseptically sorbed to montmorillonite, kaolinite, illite, sand, humic acids, and fulvic acids. Small amounts of these sorbed chemicals were dosed to an acidic, sludge-amended agricultural soil (Rossmoyne) to a final added chemical concentration of 50 ng g -1 . Controls received the same final added concentration of the chemicals in water. The ratio of sorbed chemical to soil was kept low to minimize changes to the soil mineralogy, chemistry, and microbiology. Microbial mineralization of the chemicals to 14 CO 2 was measured over a period of 60 to 70 d, and the data were fitted to first-order and 3/2-order mineralization models. Association with the soil constituents inhibited the mineralization of the chemicals in the following rank (from least to greatest effect) : controls sand < kaolinite < illite < montmorillonite humic acids < fulvic acids. These experiments demonstrated that interactions with some soil constituents (kaolinite, illite, and sand) had little effect on the microbial metabolism of these chemicals, while montmorillonite, humic acids, and especially fulvic acids significantly decreased the bioavailability of the chemicals to the microbial community. The first group of soil constituents had little influence on the mineralization kinetic parameters, whereas the latter significantly reduced at least one of the parameter estimates. The parent soil, possibly via interactions with its mineral surfaces, also had effects on the degradation of the chemicals, since soil microbial biomass and physiological activity were not correlated with any of the mineralization kinetic parameter estimates. These experiments demonstrate that the environmental form ofa chemical has a significant influence on its eventual microbial metabolism and is an important parameter to consider when investigating the fate of chemicals in soil environments.

A test system is described for assessing the mineralization of 14C-radiolabeled compounds to carbon dioxide (CO2) and methane (CH4) under anaerobic conditions. Environmentally realistic concentrations of test chemicals were incubated with anaerobic digester sludge in sealed vessels at 35 °C. The headspace of these vessels was continuously purged with nitrogen, which was passed through a series of potassium hydroxide (KOH) scrubbers to trap 14CO2. This effluent gas was mixed with oxygen and passed through a combustion tube containing cupric oxide at 800 °C to convert 14CH4 to 14CO2, which was subsequently trapped in a second series of KOH traps. Trapping efficiency was 97.1 ± 5% for 14CO2 and 108 ± 13% for 14CH4. The system was used to evaluate the mineralization of several organic chemicals including glucose, palmitic acid, hexadecanol, and two surfactants, alkyl ethoxylate sulfate (AES) and alkyl sulfate (AS), in anaerobic digester sludge. Total yields of 14CH4 and 14CO2 from these compounds exceeded 80%...

This paper introduces the environmental safety database for a new fabric softening cationic surfactant, the di-(tallow fatty acid) ester of di-2-hydroxyethyl dimethyl ammonium chloride, DEEDMAC > D i e thyl E ster D imethyl A mmonium C hloride). The physiochemical properties of DEEDMAC are similar to those for ditallow dimethyl ammonium chloride (DTDMAC), the major cationic surfactant used in fabric softener formulations world-wide for over thirty years. Importantly, however, DEEDMAC differs structurally from DTDMAC by the inclusion of two weak ester linkages between the ethyl and tallow chains. These ester linkages allow DEEDMAC to be rapidly and completely biodegraded in standard laboratory screening tests and a range of environmental compartments. including raw sewage, activated sludge, anaerobic digestor sludge, sludge amended soil, and river waters. Removal of DEEDMAC during sewage treatment is greater than 99%, as determined by computer model predictions and confirmed by laboratory simulation testing (OECD Continuous Activated Sludge confirmatory test). Using estimated tonnages, per capita waste water flows, incidences of sewage treatment for individual countries, measured removal rates, and validated computer models, maximum river water and soil concentrations of DEEDMAC have been estimated for representative usage scenarios. Based upon these maximum predicted environmental concentrations, acute and chronic toxicity testing offish, invertebrates and algae, predicted aquatic safety factors range from 272 to > 1000. Predicted steady state terrestrial safety factors are > 1000, based on EC50 values to earthworms and plants >50 mg/kg. The environmental safety database developed for DEEDMAC indicates that this cationic surfactant is rapidly and completely biodegraded, will be highly removed during sewage treatment. has an ecotoxicity profile similar to broadly used anionic and nonionic surfactants, and is environmentally safe at intended maximum usage volumes.

Olestra is a non-caloric fat substitute under review by the Food and Drug Administration. It consists of a mixture of octa-, hepta- and hexaesters of sucrose formed with long chain fatty acids. Previous studies showed olestra is not hydrolyzed by mammalian lipases and is not absorbed. The objective of this study was to evaluate the potential for colonic microflora to metabolize olestra after continued exposure. Neat and emulsified14C-[fatty acid] olestra was incubated for 72 h in both minimal and organically-enriched anaerobic media inoculated with feces from seven subjects who had consumed olestra (9 g per day) over a 3–4 week period.14C-sucrose and14C-glucose served as positive controls. Production of14CO2,14CH4,14C-volatile fatty acids (VFAs) and14C-long chain fatty acids (LCFAs) was determined. In addition, the ester distribution and fatty acid composition of olestra were examined before and after incubation. Significant quantities of14CO2 and14C-VFAs were generated from the14C-sugars, indicating that the microflora were active under the incubation conditions. Furthermore, free oleic acid was extensively hydroxylated and hydrogenated. In contrast, no degradation products (gas, VFAs, LCFAs) or changes in the olestra resulting from bacterial activity were detected. These results indicate that under anaerobic conditions the colonic microflora of the humans, consuming olestra, did not metabolize olestra.

The mineralization of 14C-labeled linear alkylbenzene sulfonate (LAS), stearyltrimethylammonium chloride (STAC) and linear alcohol ethoxylate (LAE) was examined in the anaerobic sediments of a laundromat wastewater pond and a pristine control pond. The microbial communities in sediments of the wastewater pond had been exposed to high levels of surfactants for over 25 years. Mineralization was determined by measuring the evolution of 14CO2 and 14CH4 from the 14C-test substances. [14C]Glucose and [14C]benzoic acid served as positive controls. LAS and STAC were not mineralized in sediments from either pond: LAE, glucose and benzoic acid were mineralized in both ponds. LAE mineralization was most rapid in sediment from the margin of the wastewater pond, while glucose and benzoic acid mineralization was most rapid in the control pond. With sediment from the center of the wastewater pond, mineralization of LAE, glucose and benzoic acid was preceded by a substantial lag. An experiment with specific metabolic inhibitors suggested that both methanogenic and sulfate reducing bacteria may play a role in LAE mineralization. In summary, this work demonstrates that LAE degrades anaerobically in sediments and indicates that extended acclimation does not relieve the need for molecular oxygen in LAS and STAC mineralization.

Linear alkylbenzene sulfonate (LAS) is a widely used anionic surfactant. Although approximately 1 million metric tons of LAS are produced annually, relatively little is known about the bacteria or the genetic factors that control LAS degradation in the environment. The objectives of this research were to: i) compare bacterial populations in wastewater and pristine pond systems; ii) determine the frequency of plasmids in bacteria from these sites; and iii) compare the frequency of DNA sequences coding for aromatic catabolism in isolates from these two sites. Plate counts indicated that exposure to wastewater resulted in higher levels of both heterotrophic bacteria and bacteria capable of growing on LAS containing medium (LAS/YEPG). In addition to higher numbers, a higher proportion of heterotrophs from the wastewater system were capable of growth on LAS/YEPG medium. Thus, the high levels of LAS in the wastewater system apparently selected fro organisms that were able to tolerate and/or degrade, it. Mineralization of14C-ring labelled LAS in any habitat related to the presence of organisms that grew on LAS/YEPG. Although may of these isolates could carry out primary degradation, no isolate, could mineralize14C-ring LAS in pure culture. A higher incidence of plasmids was found in bacteria from the wastewater pond and among bacteria that grew on LAS containing medium. However, the presence of plasmid, DNA did not necessarily confer the ability to degrade LAS nor was the ability to degrade LAS dependent on the presence of a plasmid. The incidence of selected genotypes for aromatic catabolism was similar among isolates on LAS/YEPG at both sites, suggesting that LAS ring degradation may be present in other populations or encoded by alternative sequences. In conclusion, LAS mineralization is mediated by a consortium and the evidence that initial attack of LAS is plasmid mediated is inconclusive.

A systematic expert-driven process is presented for evaluating analogs for read across in SAR (structure activity relationship) toxicological assessments. The approach involves categorizing potential analogs based upon their degree of structural, reactivity, metabolic and physicochemical similarity to the chemical with missing toxicological data (target chemical). It extends beyond structural similarity, and includes differentiation based upon chemical reactivity and addresses the potential that an analog and target could show toxicologically significant metabolic convergence or divergence. In addition, it identifies differences in physicochemical properties, which could affect bioavailability and consequently biological responses observed in vitro or in vivo. The approach provides a stepwise decision tree for categorizing the suitability of analogs, which qualitatively characterizes the strength of the evidence supporting the hypothesis of similarity and level of uncertainty associated with their use for read across. The result is a comprehensive framework to apply chemical, biochemical and toxicological principles in a systematic manner to identify and evaluate factors that can introduce uncertainty into SAR assessments, while maximizing the appropriate use of all available data.

8 páginas, 5 figuras, 2 tablas., An innovative biodegradation test system was developed in order to fill the current gap for cost effective and environmentally relevant tools to assess marine biodegradability. Glass beads were colonized by a biofilm in an open flow-through system of seawater with continuous pre-exposure to Linear Alkylbenzene Sulfonate (LAS) (20 μg/L). Thereafter, such colonized beads were added as inoculum in different test systems. [14C]-LAS (5–100 μg/L) was added and primary and ultimate biodegradation were assessed. The bacterial density collected on the beads (109 bact./mL beads) was ca. 3 orders of magnitude higher than the typical seawater content. The LAS mineralization lag phase duration decreased from 55 to < 1 days and the mineralization extent increased from 53 to 90% as the colonized beads volume increased from 10 to 275 mL. This is the first demonstration of marine bacteria's ability to mineralize LAS. On the opposite, less than 13% LAS was mineralized in seawater only. The colonized beads possibly enhanced the probability to encounter the full degraders' consortium in a low volume of seawater (100 mL)., This research was supported by the European Commission through the FP6 program (Early Stage Training Marie Curie Fellowship) and was performed in the framework of the RISICO project (MEST-CT-2004-505182). We also acknowledge the financial support of ERASM and ECOSOL.

The vertical distribution of microbial biomass, activity, community structure and the mineralization of xenobiotic chemicals was examined in two soil profiles in northern Wisconsin. One profile was impacted by infiltrating wastewater from a laundromat, while the other served as a control. An unconfined aquifer was present 14 meters below the surface at both sites. Biomass and community structure were determined by acridine orange direct counts and measuring concentrations of phospholipid-derived fatty acids (PLFA). Microbial activity was estimated by measuring fluorescein diacetate (FDA) hydrolysis, thymidine incorporation into DNA, and mixed amino acid (MAA) mineralization. Mineralization kinetics of linear alkylbenzene sulfonate (LAS) and linear alcohol ethoxylate (LAE) were determined at each depth. Except for MAA mineralization rates, measures of microbial biomass and activity exhibited similar patterns with depth. PLFA concentration and rates of FDA hydrolysis and thymidine incorporation decreased 10-100 fold below 3 m and then exhibited little variation with depth. Fungal fatty acid markers were found at all depths and represented from 1 to 15% of the total PLFAs. The relative proportion of tuberculostearic acid (TBS), an actinomycete marker, declined with depth and was not detected in the saturated zone. The profile impacted by wastewater exhibited higher levels of PLFA but a lower proportion of TBS than the control profile. This profile also exhibited faster rates of FDA hydrolysis and amino acid mineralization at most depths. LAS was mineralized in the upper 2 m of the vadose zone and in the saturated zone of both profiles. Little or no LAS biodegradation occurred at depths between 2 and 14 m. LAE was mineralized at all depths in both profiles, and the mineralization rate exhibited a similar pattern with depth as biomass and activity measurements. In general, biomass and biodegradative activities were much lower in groundwater than in soil samples obtained from the same depth.

The microbial mineralization of [U-14C-ring] linear alkylbenzene sulfonate (LAS) and [U-14C-ethoxylate] linear alcohol ethoxylate (LAE) was examined in 11 soils. These soils differed in their physical-chemical properties and were obtained from geographically distinct locations. With one exception, they had no previous exposure to synthetic surfactants. Soil samples were amended with trace levels (50 ng/g soil) of each 14C surfactant, and evolution of 14CO2 was measured over time. When appropriate, the data were fitted to a first-order production equation, and first order rate constants and asymptotic yields of 14CO2 were estimated using nonlinear regression. Both surfactants were mineralized without a lag period in every soil tested. Yields ranged from 16 to 71% and 30 to 69% for LAS and LAE respectively. First-order rate constants ranged from 0.14 to 0.63 for LAS and 0.07 to 0.62 for LAE. Mean half-life (across all soils) was 2 d for both surfactants. Community microbial activity, measured as the rate of acetate incorporation into lipids, did not correlate with either the rate or extent of surfactant mineralization. Subjecting these soils to cycles of wetting and drying in the laboratory prior to testing in most cases resulted in more rapid and extensive mineralization. These results indicate that microbial communities in soils have an indigenous ability to degrade low concentrations of LAS and LAE. This ability appears to be ubiquitous since it is present in a wide array of soil types from various locations. In addition, laboratory experiments involving wetting and drying of soils indicated that both the rate and extent of mineralization may be affected by climatological events.

Pure homologues of [1- 14 C] C 12 , C 14 , and C 16 alcohols and the linear alcohol ethoxylates, AE [1- 14 C alkyl] C 13 E 9 and C 16 E 9 were tested in a batch-activated sludge die-away system to assess their biodegradation kinetics and to predict levels of free alcohol derived from AE biodegradation in treated effluent. First-order rates for primary biodegradation were similar for all alcohols (86–113 h −1 ) and were used to predict removal under typical treatment conditions. Predicted removals of fatty alcohols ranged from 99.76% to 99.85%, consistent with published field data. During the biodegradation of the AE homologues, lower than expected levels of fatty alcohol based upon the assumption that biodegradation occurs through central fission were observed. Rather than fatty alcohols, the major metabolites were polar materials resulting from omega oxidation of the alkyl chain prior to or concurrent with central cleavage. The amounts of free fatty alcohols that were formed from AEs in influent and escape into effluent were negligible due both to their rapid degradation and to the finding that formation of free alcohol through central cleavage is only a minor degradation pathway in activated sludge.

Batch activated-sludge die-away studies were conducted with various pure homologs to determine the effect of ethoxylate number and alkyl chain length on the kinetics of primary and ultimate biodegradation of linear alcohol ethoxylates. The 14 C-(ethoxylate) homologs C 14 E 1 , C 14 E 3 , C 14 E 6 , and C 14 E 9 were used to investigate the effect of ethoxylate number, and 14 C-(ethoxylate) homologs C 12 E 6 , C 14 E 6 , and C 16 E 6 were used to examine the effect of chain length. Activated sludge was dosed with a trace concentration (0.2 μM) of each homolog, and the disappearance of parent, formation of metabolites, production of 14 CO 2 , and uptake into solids were monitored with time. Ethoxylate number had little effect on the first-order decay rates for primary biodegradation, which ranged from 61 to 78 h -1 . However, alkyl chain length had a larger effect, with the C 16 chain-length homolog exhibiting a slower rate of parent decay (18 h -1 ) compared to its corresponding C 12 and C 14 homologs (61-69 h -1 ). Ethoxylate number affected the mechanism of biodegradation, with fission of the central ether bond to yield the corresponding fatty alcohol and (poly)ethylene glycol group increasing in dominance with increasing ethoxylate number. Based upon the measured rates of primary biodegradation, removal of parent during activated-sludge treatment was predicted to range between 99.7 and 99.8% for all homologs except C 16 E 6 , which had a predicted removal of 98.9%. Based upon the measured rates of ultimate biodegradation, removal of ethoxylate-containing metabolites was predicted to exceed 83% for all homologs. These predictions corresponded closely with previously published removal measurements in laboratory continuous activated-sludge systems and actual treatment plants.

Triclosan (TCS; 5-chloro-2-[2,4-dichloro-phenoxy]-phenol) is a widely used antimicrobial agent. To understand its fate during sewage treatment, the biodegradation and removal of TCS were determined in activated sludge. In addition, the effects of TCS on treatment processes were assessed. Fate was determined by examining the biodegradation and removal of TCS radiolabeled with 14C in the 2,4-dichlorphenoxy ring in laboratory batch mineralization experiments and bench-top continuous activated-sludge (CAS) systems. In batch experiments with unacclimated sludge, TCS was mineralized to 14CO2, but the total yield varied as a function of test concentration. Systems that were redosed with TCS exhibited more extensive and faster mineralization, indicating that adaptation was a critical factor determining the rate and extent of biodegradation. In a CAS study in which the influent level of TCS was incrementally increased from 40 microg/L to 2,000 microg/L, removal of the parent compound exceeded 98.5% and removal of total radioactivity (parent and metabolites) exceeded 85%. Between 1.5 and 4.5% of TCS in the influent was sorbed to the wasted solids, whereas94% underwent primary biodegradation and 81 to 92% was mineralized to CO2 or incorporated in biomass. Increasing levels of TCS in the influent had no major adverse effects on any wastewater treatment process, including chemical oxygen demand, biological oxygen demand, and ammonia removal. In a subsequent experiment, a CAS system, acclimated to TCS at 35 microg/L, received two separate 4-h shock loads of 750 microg/L TCS. Neither removal of TCS nor treatment processes exhibited major adverse effects. An additional CAS study was conducted to examine the removal of a low level (10 microg/L) of TCS. Removal of parent equaled 94.7%, and biodegradation remained the dominant removal mechanism. A subsequent series of CAS experiments examined removal at four influent concentrations (7.5, 11, 20, and 50 microg/L) of TCS and demonstrated that removal of parent ranged from 98.2 to 99.3% and was independent of concentration. Although TCS removal across all experiments appeared unrelated to influent concentration, removal was significantly correlated (r2 = 0.87) with chemical oxygen demand removal, indicating that TCS removal was related to overall treatment efficiency of specific CAS units. In conclusion, the experiments show that TCS is extensively biodegraded and removed in activated-sludge systems and is unlikely to upset sewage treatment processes at levels expected in household and manufacturing wastewaters.

More than 2,100 chemically defined organic chemicals are listed in the Research Institute of Fragrance Materials/Flavor and Extract Manufacturers' Association (RIFM/FEMA) Database that are used as ingredients of fragrances for consumer products. An approach was developed for prioritizing these fragrance materials for aquatic risk assessment by first estimating the predicted environmental concentration (PEC) of these fragrance materials in the aquatic environment based upon their physicochemical properties and annual volume of use. Subsequently, an effect level was predicted with a general quantitative structure-activity relationship (QSAR) for aquatic toxicity, and a predicted no-effect concentration (PNEC) was calculated from this effect level by using an assessment factor (AF) that accounts for uncertainty in the toxicity QSAR prediction. A conservative AF of 10(6) was applied to the endpoint predicted by the QSAR to provide an adequate margin of safety in the calculation of the PNEC. The PEC was compared to the PNEC to characterize the risk to freshwater aquatic organisms (e.g., Daphnia magna and Pimephales promelas). If the ratio of PEC to PNEC was below one, the material was considered to have negligible environmental risk and to be acceptable for the aquatic environment at current use levels. If this ratio exceeded one, the PNEC was refined by using more specific QSAR models (Ecological Structure-Activity Relationships [ECOSAR]). If the ratio continued to exceed one, the material became a candidate for further aquatic risk assessment procedures, which involve iterative steps to refine the PEC, the PNEC, or both by using measured ecotoxicological endpoints. Prioritization for this latter process can be based upon the magnitudes of the estimated PEC:PNEC ratios. When using the first tier of this approach, only 568 of 2,141 fragrance materials (26.5%) in the RIFM/FEMA Database had PEC:PNEC ratios greater than one. This percentage decreased to only 164 materials (7.7%) when PNECs were derived with ECOSAR. Comparison of predicted PECs and PNECs with those based upon measured data confirmed the conservatism and low risk for type I errors associated with the framework. These combined exercises demonstrated the ability of this highly precautionary risk-based screening approach to quickly prioritize a large number of materials without benefit of experimental ecotoxicological or fate data.

An important first step in pollution prevention is accurately assessing the biodegradation and fate of a chemical prior to its manufacture and widespread use. With the exception of pesticides and agricultural chemicals, which are deliberately introduced into the environment, most chemicals enter the environment as a secondary result of their manufacture, transport and disposal. In the case of consumer product chemicals, the major routes of entry into the environment result from their disposal by the household down the drain or in the solid waste. In the United States, most domestic wastewater is treated prior to release to natural waters. Approximately 75% of total wastewater flow is treated in publicly owned sewage treatment works, while the remaining 25% receives some type of on-site treatment. The most common form of on-site treatment involves a septic tank and tile field.

The biodegradability of a substance depends on the structure and physical form of the substance, the time that has been available for acclimation, and the environmental conditions. Importantly, these later factors can be just as important as structure in determining the outcome of a biodegradation test. The development of appropriate QSARs for biodegradation and the ultimate value of the final QSAR depends on understanding these factors. This paper will describe what is known about the effect of test conditions on the results of biodegradation tests. The ability of these tests to reflect real environmental conditions will also be examined. Finally, we will discuss what we believe, in the light of this information, should be the goal of biodegradation QSARs and how these QSARs can be most appropriately used in fate assessments.

The fate of detergent surfactants in the sewer can be studied both in laboratory tests and in field experiments. The laboratory studies can be used to determine the rate of disappearance of a test molecule as a function of residence time and estimate its half-life in a given habitat. In addition, important information can be obtained on the mechanism of degradation. Field studies can determine the actual environmental concentrations of surfactants in raw sewage which can then be compared with the expected concentration based on consumption volumes. The difference between the measured and predicted concentration provides an estimate for the disappearance of the test chemical during its travel in the sewer and confirms the results of the laboratory tests. This paper focuses on the fate of a number of important representative anionic, nonionic and cationic surfactants, in the sewer. The results of laboratory die-away studies showed that, in general, the half-life for disappearance in the sewer was in the order of hours for Fatty Alcohol Ethoxylate (AE), Fatty Alcohol Ethoxy Sulphate (AES) and Di-Ethyl-Ester Di-methyl-Ammonium Chloride (DEEDMAC). These laboratory findings for AES were confirmed by monitoring actual raw sewage reaching municipal sewage treatment plants. In addition, a field study demonstrated that the concentration of glucose amides (GA) is considerably reduced during its travel in the sewer. These complementary laboratory and field studies provide key information for the safety assessment of surfactants. They demonstrate that the concentration of surfactants can be significantly reduced in the sewer resulting in a rapid reduction of the environmental loading, which is particularly important in environmental situations where inadequate or no sewage treatment exists.

This research addressed the effect of mineral and organic soil constituents on the fate of organic compounds in soils. Specifically, it sought to determine how the associations between organic chemicals and different soil constituents affect their subsequent biodegradation in soil. Four 14 C-labeled surfactants were aseptically adsorbed to montmorillonite, kaolinite, illite, sand, and humic acids. These complexes were mixed with a woodlot soil, and 14 CO 2 production was measured over time. The mineralization data were fitted to various production models by nonlinear regression, and a mixed (3/2)-order model was found to most accurately describe the mineralization patterns. Different mineralization patterns were observed as a function of the chemical and soil constituents. Surfactants that had been preadsorbed to sand or kaolinite usually showed similar mineralization kinetics to the control treatments, in which the surfactants were added to the soil as an aqueous solution. Surfactants that had been bound to illite or montmorillonite were typically degraded to lesser extents than the other forms, while surfactant-humic acid complexes were degraded more slowly than the other forms. The desorption coefficients ( K d ) of the soil constituent-bound surfactants were negatively correlated with the initial rates of degradation ( k 1 ) and estimates of 14 CO 2 yield ( P o ) as well as actual total yields of 14 CO 2 . However, there was no relationship between K d and second-stage zero-order rates of mineralization ( k o ). Microbial community characteristics (biomass and activity) were not correlated with any of the mineralization kinetic parameters. Overall, this study showed that environmental form had a profound effect on the ultimate fate of biodegradable chemicals in soil. This form is defined by the physicochemical characteristics of the chemical, the composition and mineralogy of the soil, and the mode of entry of the chemical into the soil environment.

The conference organizers assigned the authors of this paper the task of preparing a critical review and summary of the Conference, that not only included major themes discussed by the participants but in addition identified important points that were not covered. During the conference, each author took responsibility for covering a different session; however, since many themes came up in multiple sessions, this paper has been organized according to theme and not session.

In Antarctica there exists a cryptoendolithic microbiota which survives extremely low temperatures. Fatty acid analysis of the membrane phospholipids of this microbial community showed a predominance of polyunsaturated fatty acids. Artificial membranes made from the purified community phospholipids remained fluid to below −20°C and had unusual hydration properties.

In wetlands and canopied bodies of water, plant detritus is an important source of carbon and energy. Detrital materials possess a large surface area for sorption of dissolved organics and are colonized by a large and diverse microbiota. To examine the biodegradation of surfactants by these microorganisms, submerged oak leaves were obtained from a laundromat wastewater pond, its overflow, and a pristine control pond. Leaves were cut into disks and incubated in sterile water amended with 50 μg of 14 C-labeled linear alkylbenzene sulfonate (LAS), linear alcohol ethoxylate, stearyltrimethyl ammonium chloride, distearyldimethyl ammonium chloride, benzoic acid, or mixed amino acids per liter. Sorption of the test compounds to the detritus and evolution of 14 CO 2 were followed with time. All of the compounds sorbed to the detritus to various degrees, with LAS and stearyltrimethyl ammonium chloride the most sorptive and benzoic acid the least. All compounds were mineralized without a lag. With leaves from the laundromat wastewater pond, half-lives were 12.6 days for LAS, 8.4 days for linear alcohol ethoxylate, 14.2 days for stearyltrimethyl ammonium chloride, 1.0 days for benzoic acid, and 2.7 days for mixed amino acids. Mineralization of LAS and linear alcohol ethoxylate by control pond leaves was slower and exhibited an S-shaped rather than a typical first-order pattern. This study shows that detritus represents a significant site of surfactant removal in detritus-rich systems.

Estuarine soft-bottom sediments in microcosms and the field were compared with regard to microbial community structure. Community structure was determined by analyzing the fatty acids derived from the microbial lipids in the sediments. Fatty acid profiles were compared using a multivariate statistical approach. Experiments were performed using sediments from St. George Sound and Apalachicola Bay, Florida. The community structure of St. George Sound sediments was apparently controlled by epibenthic predators. In Apalachicola Bay, the dominant influences were physical factors related to the flow of the Apalachicola River. In the St. George Sound experiment, microbial communities in the microcosms differed from those in the field after only 2 weeks, and the degree of this difference increased substantially as time progressed. In the Apalachicola Bay experiment, although microbial communities in the microcosms were detectably different from those in the field, the degree of this difference was not large nor did it increase with time. This differential behavior of sediment communities from different sites may be related to the different ecological factors regulating community composition at these sites.

The mineralization of linear alkylbenzene sulfonate (LAS), linear alcohol ethoxylate (LAE), benzylamine, and monoalkyl and dialkyl quaternary ammonium compounds was determined as a function of depth in sediment profiles from beneath a laundromat waste-water pond and pristine control pond. In addition, bacterial number, microbial activity, and concentrations of LAS and quaternary ammonium compounds were measured. Surfactant concentration decreased dramatically with increasing depth in the laundromat profile. Bacterial number and activity decreased with depth in both profiles; however, biomass and activity were higher in the laundromat profile. Mineralization was measured by amending samples with 14C-labeled substrates and following the evolution of 14CO2 with time. LAS was mineralized without a lag period at all depths in the laundromat profile; its half-life ranged from 3.2 to 16.5 days. In the control pond, it was mineralized more slowly (half-life 5.2 to 1540 days) and only after a lag period of 2 to 40 days. LAE was also mineralized with shorter lags and more rapidly in the laundromat than in the control profile; half-lives ranged between 2.8 to 8.6 days in the former and 3.5 to 137 days in the latter. Although monoalkyl and dialkyl quaternary ammonium compounds were not mineralized in the control profile, slow but significant mineralization of these compounds occurred in the laundromat profile. Benzylamine was rapidly degraded without a lag in both profiles. Field concentration data and the results of mineralization studies indicated that biodegradation combined with the effects of adsorption is a practical mechanism of surfactant removal in subsurface environments. In addition, adaptation resulting from exposure of microbial communities to surfactants is an important factor governing the fate of surfactants in the subsurface.

The use of semicontinuous culture system for determining the role of the human intestinal microflora int he biotransformation of xenobiotics is discussed. This model system, which stimulates the lumen of the large intestine, has been used to investigate human intestinal microflora metabolism of compounds representative of three different classes of chemicals; a benzidine-based azo dye, Direct Black 38, a nitropolycyclic aromatic hydrocarbon, 1-nitropyrene and a substituted pyrimidine, 5-fluorocytosine. Metabolites of each of the test compounds were identified, and the kinetics of production and biological activity of the metabolites determined. Metabolic adaptation was observed with 1-nitropyrene and 5-fluorocytosine incubations. This microbial culture system could be quite useful, especially in concert with other in vitro models and animal studies, for determining the pharmacological and toxicological role of the human intestinal microflora in the transformation of xenobiotics. Particular emphasis on the application of this method for toxicological studies in elucidating the role of the intestinal microflora in the etiology of cancer is described.

Microbial colonization and its relation to the decomposition of sedge (Carex) leaf litter were studied in the littoral area of Toolik Lake, Alaska. Colonization was assessed using scanning electron microscopy and by measuring the concentration of ATP associated with the litter. Litter lost approximately 20% of its dry weight and 60% of its phosphorus by leaching during the first 4 days of exposure to lake water. Microbial activity was responsible for any additional decomposition. Microorganisms were first observed on the litter surface on the 3rd day of incubation in the lake, when isolated bacterialike forms and microbial filament were present, but ATP was not yet detected. This initial appearance of microbes was followed by a dramatic rise in ATP concentration and a rapid proliferation of microbial forms, especially large filaments. Associated with this rapid colonization was a steep decline in nitrogen content, a twofold increase in protein content, and the appearance of microbially mediated weight loss of the litter. By day 13, microbial colonization declined by 50% and remained stabilized at this lower level for the duration of the study. This decline coincided with the demise of the large filamentous forms, a decrease in the protein content of the litter, and slower but continued decrease in the nitrogen content of the litter. As time progressed, the microbial community became increasingly characterized first by the presence of bacterialike forms enmeshed in slime and later by large numbers of penna*** diatoms. These findings show that decomposition is dependent on the development and succession of the microbial community on the litter.

Several variations in the scintillation mixture and the filter paper arrangements for double-vial radiorespirometry were compared. Improved efficiencies (44%) and shorter response times were found by adding wetting agents and methanolic NaOH to the scintillation mixture in the filter paper. The scintillation chemicals used did not contain dioxane and were found to be nontoxic to the test microbiota in this system. Covering the inner reaction vial with aluminum foil minimized the reduction in counting efficiency when testing colored or dense environmental samples. Mineralization rates were determined with 14 C-labeled glucose, acetate, and glutamate and [ 14 C]cellulose- and [ 14 C]lignin-labeled lignocellulose for composting cow manure, forest soil, and arctic lake sediment microbiota. This improved method can be used in a variety of procedures involving the measurement of microbial mineralizations of organic compounds. Since no liquid scintillation cocktail is used for counting, the radioactive wastes are aqueous or can be incinerated, making disposal easy.

The decomposition and microbial colonization of Carex leaf litter were examined in an arctic lake in Alaska during the summer of 1978. Dried leaf segments in screen bags were placed at various locations and depths for 13 and 26 days. Weight loss varied from 24.15 to 33.56% and from 27.69 to 65.01% after 13 and 26 days, respectively. Abiotic controls lost approximately 19.5% with no subsequent change. Weight loss significantly correlated with microbial colonization as measured by alkaline phosphatase activity ( r = 0.780), cellulase activity ( r = 0.613), heterotrophic CO 2 fixation ( r = 0.835), and acetate incorporation into microbial lipids ( r = 0.618). Alkaline phosphatase activity correlated with cellulase activity ( r = 0.889), and heterotrophic CO 2 fixation correlated with acetate incorporation into lipids ( r = 0.712). Weight loss after 26 days inversely correlated with the logarithm of the depth of incubation regardless of whether incubation occurred on the sediment surface or in the water column. These findings suggest that a rapid initial period of microbial colonization is driven by nutrients derived from the litter and that the rate of these processes is controlled by a factor(s) inversely related to the logarithm of depth, such as light intensity, primary production, or turbulence.

The mineralization of benzoic acid, phenol, and benzylamine was determined as a function of depth in two 20-m sandy soil profiles, one of which was adjacent to a leach field receiving wastewater from a laundromat. Soil samples were collected aseptically, adjusted to 20–25% water content and amended with a trace level (50 ng/g soil) of the 14C-ring-labeled compounds. Evolution of CO2 was followed with time. First-order rate constants and the extents of mineralization were estimated from the resulting data by nonlinear regression. All three compounds were mineralized in every sample examined without a lag period. In general, phenol was mineralized more rapidly than benzoic acid, which was more rapidly mineralized than benzylamine. Benzylamine had the highest sorption coefficient; phenol had the lowest. Average half-life was 0.56 days for phenol, 0.84 days for benzoic acid, and 1.31 days for benzylamine. Mineralization rates did not correlate with bacterial number, fluorescein diacetate hydrolysis rate, or any soil characteristic. The ultimate percentage of all three compounds mineralized was lowest in the upper 3 m of both soil profiles. The total amounts of phenol and benzoic acid mineralized negatively correlated with cation-exchange capacity and silt content. Statistical analysis (2-level nested ANOVA) revealed that only the rate of phenol mineralization varied significantly as a function of soil profile, but rates for all three compounds varied significantly as a function of depth within a profile.