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At least 55 records · Page 3Linked to original sources
USGS2007

Accumulation of dechlorination daughter products: A valid metric of chloroethene biodegradation

In situ reductive dechlorination of perchloroethene (PCE) and trichloroethene (TCE) generates characteristic chlorinated (cis-dichloroethene [cis-DCE] and vinyl chloride [VC]) and nonchlorinated (ethene and ethane) products. The accumulation of these daughter products is commonly used as a metric for ongoing biodegradation at field sites. However, this interpretation assumes that reductive dechlorination is the only chloroethene degradation process of any significance in situ and that the characteristic daughter products of chloroethene reductive dechlorination persist in the environment. Laboratory microcosms, prepared with aquifer and surface-water sediments from hydrologically diverse sites throughout the United States and amended with [1,2- 14 C] TCE, [1,2- 14 C] DCE, [1,2- 14 C] DCA, or [1,2- 14 C] VC, demonstrated widely variable patterns of intermediate and final product accumulation. In predominantly methanogenic sediment treatments, accumulation of 14 C-DCE, 14 C-VC, 14 C-ethene, and 14 C-ethane predominated. Treatments characterized by significant Fe(III) and/or Mn(IV) reduction, on the other hand, demonstrated substantial, and in some cases exclusive, accumulation of 14 CO 2 and 14 CH 4 . These results suggest that relying on the accumulation of cis-DCE, VC, ethene, and ethane may substantially underestimate overall chloroethene biodegradation at many sites.

Remediation Journal↗
USGS2008

Effect of rhizosphere on soil microbial community and in-situ pyrene biodegradation

To access the influence of a vegetation on soil microorganisms toward organic pollutant biogegration, this study examined the rhizospheric effects of four plant species (sudan grass, white clover, alfalfa, and fescue) on the soil microbial community and in-situ pyrene (PYR) biodegradation. The results indicated that the spiked PYR levels in soils decreased substantially compared to the control soil without planting. With equal planted densities, the efficiencies of PYR degradation in rhizosphere with sudan grass, white clover, alfalfa and fescue were 34.0%, 28.4%, 27.7%, and 9.9%, respectively. However, on the basis of equal root biomass the efficiencies were in order of white clover >> alfalfa > sudan > fescue. The increased PYR biodegradation was attributed to the enhanced bacterial population and activity induced by plant roots in the rhizosphere. Soil microbial species and biomasses were elucidated in terms of microbial phospholipid ester-linked fatty acid (PLFA) biomarkers. The principal component analysis (PCA) revealed significant changes in PLFA pattern in planted and non-planted soils spiked with PYR. Total PLFAs in planted soils were all higher than those in non-planted soils. PLFA assemblages indicated that bacteria were the primary PYR degrading microorganisms, and that Gram-positive bacteria exhibited higher tolerance to PYR than Gram-negative bacteria did. ?? 2008 Higher Education Press and Springer-Verlag GmbH.

Frontiers of Environmental Science and Engineering↗
USGS2013

Application of stable isotope ratio analysis for biodegradation monitoring in groundwater

Stable isotope ratio analysis is increasingly being applied as a tool to detect, understand, and quantify biodegradation of organic and inorganic contaminants in groundwater. An important feature of this approach is that it allows degradative losses of contaminants to be distinguished from those caused by non-destructive processes such as dilution, dispersion, and sorption. Recent advances in analytical techniques, and new approaches for interpreting stable isotope data, have expanded the utility of this method while also exposing complications and ambiguities that must be considered in data interpretations. Isotopic analyses of multiple elements in a compound, and multiple compounds in the environment, are being used to distinguish biodegradative pathways by their characteristic isotope effects. Numerical models of contaminant transport, degradation pathways, and isotopic composition are improving quantitative estimates of in situ contaminant degradation rates under realistic environmental conditions.

Current Opinion in Biotechnology↗
USGS2021

Hydrocarbons to carboxyl-rich alicyclic molecules: A continuum model to describe biodegradation of petroleum-derived dissolved organic matter in contaminated groundwater plumes

Relationships between dissolved organic matter (DOM) reactivity and chemical composition in a groundwater plume containing petroleum-derived DOM (DOM HC ) were examined by quantitative and qualitative measurements to determine the source and chemical composition of the compounds that persist downgradient. Samples were collected from a transect down the core of the plume in the direction of groundwater flow. An exponential decrease in dissolved organic carbon concentration resulting from biodegradation along the transect correlated with a continuous shift in fluorescent DOM HC from shorter to longer wavelengths. Moreover, ultrahigh resolution mass spectrometry showed a shift from low molecular weight (MW) aliphatic, reduced compounds to high MW, unsaturated (alicyclic/aromatic), high oxygen compounds that are consistent with carboxyl-rich alicyclic molecules. The degree of condensed aromaticity increased downgradient, indicating that compounds with larger, conjugated aromatic core structures were less susceptible to biodegradation. Nuclear magnetic resonance spectroscopy showed a decrease in alkyl (particularly methyl) and an increase in aromatic/olefinic structural motifs. Collectively, data obtained from the combination of these complementary analytical techniques indicated that changes in the DOM HC composition of a groundwater plume are gradual, as relatively low molecular weight (MW), reduced, aliphatic compounds from the oil source were selectively degraded and high MW, alicyclic/aromatic, oxidized compounds persisted.

Minnesota↗
USGS1998

Biodegradation of crude oil into nonvolatile organic acids in a contaminated aquifer near Bemidji, Minnesota

As the result of a pipeline burst, a body of light aliphatic crude oil floats atop the groundwater in a shallow sand and gravel aquifer in a remote area outside Bemidji, Minnesota. Biodegradation has resulted in the formation of a plume of DOC downgradient from the oil body. Groundwater has also been contaminated in an area known as the spray zone, from vertical infiltration of DOC resulting from biodegradation of crude oil in the overlying unsaturated zone. The majority of DOC in the contaminated groundwater is in the form of nonvolatile organic acids (NVOA's) which represent the partial oxidation products of the crude oil constituents. The NVOA's have been classified into three fractions according to their isolation on XAD resins: hydrophobic neutrals (HPO-N), hydrophobic acids (HPO-A) and hydrophilic acids (HPI-A). These fractions of NVOA's were isolated from a well downgradient from the oil body (well 530; DOC=21 mg C/l), from a well in the spray zone (well 603; DOC=15 mg C/l) and from an uncontaminated well upgradient of the oil body where the naturally occurring DOC is 2.9 mg C/l (well 310). The three sets of NVOA's were characterized by elemental analyses, molecular weight determinations, 14 C ages and liquid phase 1 H and 13 C NMR. The crude oil and the saturate, aromatic, resin and asphaltene fractions of the crude oil were similarly analyzed by elemental analysis and NMR. The NVOA's from the contaminated wells were clearly distinguishable from the naturally occurring groundwater DOC. Based upon molecular weights, sulfur contents, aromaticities and the presence of methyl groups bonded to aromatic rings, the characterization data suggests that the NVOA's originate from the C 18 or greater alkylaromatic, naphthenoaromatic and sulfur-containing constituents of the crude oil, including possibly the resins and asphaltenes.

Minnesota↗
USGS2001

Methyl tert-butyl ether biodegradation by indigenous aquifer microorganisms under natural and artificial oxic conditions

Microbial communities indigenous to a shallow groundwater system near Beaufort, SC, degraded milligram per liter concentrations of methyl tert -butyl ether (MTBE) under natural and artificial oxic conditions. Significant MTBE biodegradation was observed where anoxic, MTBE-contaminated groundwater discharged to a concrete-lined ditch. In the anoxic groundwater adjacent to the ditch, concentrations of MTBE were >1 mg/L. Where groundwater discharge occurs, dissolved oxygen (DO) concentrations beneath the ditch exceeded 1.0 mg/L to a depth of 1.5 m, and MTBE concentrations decreased to <1 μg/L prior to discharge. MTBE mass flux calculations indicate that 96% of MTBE mass loss occurs in the relatively small oxic zone prior to discharge. Samples of a natural microbial biofilm present in the oxic zone beneath the ditch completely degraded [U- 14 C]MTBE to [ 14 C]CO 2 in laboratory liquid culture studies, with no accumulation of intermediate compounds. Upgradient of the ditch in the anoxic, MTBE- and BTEX-contaminated aquifer, addition of a soluble oxygen release compound resulted in oxic conditions and rapid MTBE biodegradation by indigenous microorganisms. In an observation well located closest to the oxygen addition area, DO concentrations increased from 0.4 to 12 mg/L in <60 days and MTBE concentrations decreased from 20 to 3 mg/L. In the same time period at a downgradient observation well, DO increased from <0.2 to 2 mg/L and MTBE concentrations decreased from 30 to <5 mg/L. These results indicate that microorganisms indigenous to the groundwater system at this site can degrade milligram per liter concentrations of MTBE under natural and artificial oxic conditions.

Environmental Science & Technology↗
USGS2001

Effect of redox conditions on MTBE biodegradation in surface water Sediments

Microbial degradation of methyl tert-butyl ether (MTBE) was observed in surface water-sediment microcosms under anaerobic conditions. The efficiency and products of anaerobic MTBE biodegradation were dependent on the predominant terminal electron-accepting conditions. In the presence of substantial methanogenic activity, MTBE biodegradation was nominal and involved reduction of MTBE to the toxic product, tert-butyl alcohol (TBA). In the absence of significant methanogenic activity, accumulation of [14C]TBA generally decreased, and mineralization of [U-14C]MTBE to 14CO2 generally increased as the oxidative potential of the predominant terminal electron acceptor increased in the order of SO4, Fe(III), Mn(IV) < NO3 < O2. Microbial mineralization of MTBE to CO2 under Mn(IV)or SO4-reducing conditions has not been reported previously. The results of this study indicate that microorganisms inhabiting the sediments of streams and lakes can degrade MTBE effectively under a range of anaerobic terminal electron-accepting conditions. Thus, anaerobic bed sediment microbial processes may provide a significant environmental sink for MTBE in surface water systems throughout the United States.

Environmental Science & Technology↗
USGS2002

TBA biodegradation in surface-water sediments under aerobic and anaerobic conditions

The potential for [U-14C] TBA biodegradation was examined in laboratory microcosms under a range of terminal electron accepting conditions. TBA mineralization to CO2 was substantial in surface-water sediments under oxic, denitrifying, or Mn(IV)-reducing conditions and statistically significant but low under SO4-reducing conditions. Thus, anaerobic TBA biodegradation may be a significant natural attenuation mechanism for TBA in the environment, and stimulation of in situ TBA bioremediation by addition of suitable terminal electron acceptors may be feasible. No degradation of [U-14C] TBA was observed under methanogenic or Fe(III)-reducing conditions.

Environmental Science & Technology↗
USGS1999

Role for acetotrophic methanogens in methanogenic biodegradation of vinyl chloride

Under methanogenic conditions, stream-bed sediment microorganisms rapidly degraded [1,2-14C]vinyl chloride to 14CH4 and 14CO2. Amendment with 2-bromoethanesulfonic acid eliminated 14CH4 production and decreased 14CO2 recovery by an equal molar amount. Results obtained with [14C]ethene, [14C]acetate, or 14CO2 as substrates indicated that acetotrophic methanogens were responsible for the production of 14CH4 during biodegradation of [1,2-14C]VC.Under methanogenic conditions, stream-bed sediment microorganisms rapidly degraded [1,2-14C]vinyl chloride to 14CH4 and 14CO2. Amendment with 2-bromoethanesulfonic acid eliminated 14CH4 production and decreased 14CO2 recovery by an equal molar amount. Results obtained with [14C]-ethene, [14C]acetate, or 14CO2 as substrates indicated that acetotrophic methanogens were responsible for the production of 14CH4, during biodegradation of [1,2-14C]VC.

Environmental Science & Technology↗
USGS2010

Use of a reactive gas transport model to determine rates of hydrocarbon biodegradation in unsaturated porous media

A mathematical model is presented that simulates the transport and reaction of any number of gaseous phase constituents (e.g. CO 2 , O 2 , N 2 , and hydrocarbons) in unsaturated porous media. The model was developed as part of a method to determine rates of hydrocarbon biodegradation associated with natural cleansing at petroleum product spill sites. The one-dimensional model can be applied to analyze data from column experiments or from field sites where gas transport in the unsaturated zone is approximately vertical. A coupled, non-Fickian constitutive relation between fluxes and concentration gradients, together with the capability of incorporating heterogeneity with respect to model parameters, results in model applicability over a wide range of experimental and field conditions. When applied in a calibration mode, the model allows for the determination of constituent production/consumption rates as a function of the spatial coordinate. Alternatively, the model can be applied in a predictive mode to obtain the distribution of constituent concentrations and fluxes on the basis of assumed values of model parameters and a biodegradation hypothesis. Data requirements for the model are illustrated by analyzing data from a column experiment designed to determine the aerobic degradation rate of toluene in sediments collected from a gasoline spill site in Galloway Township, New Jersey.

Water Resources Research↗
USGS1994

Stimulated anoxic biodegradation of aromatic hydrocarbons using Fe(III) ligands

Contamination of ground waters with water-soluble aromatic hydrocarbons, common components of petroleum pollution, often produces anoxic conditions under which microbial degradation of the aromatics is slow. Oxygen is often added to contaminated ground water to stimulate biodegradation, but this can be technically difficult and expensive. Insoluble Fe(III) oxides, which are generally abundant in shallow aquifers, are alternative potential oxidants, but are difficult for microorganisms to access. Here we report that adding organic ligands that bind to Fe(III) dramatically increases its bioavailability, and that in the presence of these ligands, rates of degradation of aromatic hydrocarbons in anoxic aquifer sediments are comparable to those in oxic sediments. We find that even benzene, which is notoriously refractory in the absence of oxygen, can be rapidly degraded. Our results suggest that increasing the bioavailability of Fe(III) by adding suitable ligands provides a potential alternative to oxygen addition for the bioremediation of petroleum-contaminated aquifers.Contamination of ground waters with water-soluble aromatic hydrocarbons, common components of petroleum pollution, often produces anoxic conditions under which microbial degradation of the aromatics is slow. Oxygen is often added to contaminated ground water to stimulate biodegradation, but this can be technically difficult and expensive. Insoluble Fe(III) oxides, which are generally abundant in shallow aquifers, are alternative potential oxidants, but are difficult for microorganisms to access. Here we report that adding organic ligands that bind to Fe(III) dramatically increases its bioavailability, and that in the presence of these ligands, rates of degradation of aromatic hydrocarbons in anoxic aquifer sediments are comparable to those in oxic sediments. We find that even benzene, which is notoriously refractory in the absence of oxygen, can be rapidly degraded. Our results suggest that increasing the bioavailability of Fe(III) by adding suitable ligands provides a potential alternative to oxygen addition for the bioremediation of petroleum-contamined aquifers.

Nature↗
USGS2014

Effect of light on biodegradation of Estrone, 17β-estradiol, and 17α-ethinylestradiol in stream sediment

Biodegradation of [A-ring 14 C] Estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) to 14 CO 2 was investigated under light and dark conditions in microcosms containing epilithon or sediment collected from Boulder Creek, Colorado. Mineralization of the estrogen A-ring was observed in all sediment treatments, but not epilithon treatments. No difference in net mineralization between light and dark treatments was observed for 14 C-E2. Net mineralization of 14 C-E1 and 14 C-EE2 was enhanced in light treatments. Extents of 14 CO 2 accumulation and rates of mineralization were significantly greater for E2 than E1 under dark conditions, but were comparable under light conditions. These results indicate substantial differences in the uptake and metabolism of E1 and E2 in the environment and suggest biorecalcitrance of E1 relative to E2 in light-limited environments. The extent of 14 CO 2 accumulation and rate of mineralization for EE2 in dark treatments were less than half of that observed for E2 and generally lower than for E1, consistent with previous reports of EE2 biorecalcitrance. However, 14 CO 2 accumulation and rates of mineralization were comparable for EE2, E2, and E1 under light conditions. These results indicate photoactivation and/or phototransformation/photodegradation processes can substantially enhance heterotrophic biodegradation of estrogens in sunlit environments and may play an important role in estrogen transport and attenuation.

Colorado↗
USGS1994

Spatial variability in biodegradation rates as evidenced by methane production from an aquifer

Accurate predictions of carbon and energy cycling rates in the environment depend on sampling frequencies and on the spatial variability associated with biological activities. We examined the variability associated with anaerobic biodegradation rates at two sites in an alluvial sand aquifer polluted by municipal landfill leachate. In situ rates of methane production were measured for almost a year, using anaerobic wells installed at two sites. Methane production ranged from 0 to 560 μmol · m -2 · day -1 at one site (A), while a range of 0 to 120,000 μmol · m -2 · day -1 was measured at site B. The mean and standard deviations associated with methane production at site A were 17 and 57 μmol · m -2 · day -1 , respectively. The comparable summary statistics for site B were 2,000 and 9,900 μmol · m -2 · day -1 . The coefficients of variation at sites A and B were 340 and 490%, respectively. Despite these differences, the two sites had similar seasonal trends, with the maximal rate of methane production occurring in summer. However, the relative variability associated with the seasonal rates changed very little. Our results suggest that (i) two spatially distinct sites exist in the aquifer, (ii) methanogenesis is a highly variable process, (iii) the coefficient of variation varied little with the rate of methane production, and (iv) in situ anaerobic biodegradation rates are lognormally distributed.

Applied and Environmental Microbiology↗
USGS2001

Biodegradation of MTBE by indigenous aquifer microorganisms under artificial oxic conditions

The hypothesis that artificial oxic conditions will lead to MTBE biodegradation by indigenous microorganisms in anoxic, gasoline-contaminated aquifers was examined by adding oxygen in the form of a metal peroxide slurry to an anoxic part of gasoline-contaminated aquifer in South Carolina. Field observations of relatively rapid aerobic MTBE biodegradation following oxygen addition suggest that the indigenous bacteria have become acclimated not only to mg/L concentrations of MTBE in the gasoline plume, but also to periodic delivery of oxygen by recharge events. Significant natural attenuation of MTBE could occur if the oxygen limitations naturally associated with gasoline releases can be removed, either under natural conditions where discharging anoxic groundwater comes into contact with oxygen, or artificial conditions where oxygen can be added to aquifers containing mg/L concentrations of MTBE. This final solution might be an effective strategy for intercepting characteristically long MTBE plumes, particularly at sites not characterized by groundwater discharge to land surface. This is an abstract of a paper presented at the 222nd ACS National Meting (Chicago, IL 8/26-30/2001).

ACS Division of Environmental Chemistry, Preprints↗
USGS1997

Cometabolic biodegradation of trichloroethylene in microcosms

Laboratory microcosms were used to determine the concentrations of oxygen (O 2 ) and methane (CH 4 ) that optimize trichloroethylene (TCE) biodegradation in sediment and ground-water samples from a TCE-contaminated aquifer at Picatinny Arsenal, Morris County, New Jersey. The mechanism for degradation is the cometabolic activity of methanotrophic bacteria. The laboratory data will be used to support a field study designed to demonstrate the effectiveness of combining air sparging with cometabolic degradation of TCE for the purpose of aquifer remediation. Microcosms were constructed in autoclaved 250-mL (milliliter) amber glass bottles with valves for repeated headspace sampling. Equal volumes (25 mL) of sediment and ground water, collected from a depth of 40 feet, were added. TCE was added to attain initial aqueous concentrations equal to the field level of 1,400 mu g/L (micrograms per liter). Nine microcosms were constructed with initial headspace O 2 concentrations of 5%, 10%, or 14% and CH 4 concentrations of 0.5%, 3%, or 5%, with nitrogen making up the balance. Sterile controls, controls without CH 4 , and controls without sediment were also constructed. A 4-mL gas sample was removed periodically and TCE, O 2 , CH 4 , and carbon dioxide (CO 2 ) concentrations were measured by using gas chromatography. As biodegradation proceeded, the decrease in O 2 , CH 4 , and TCE concentrations and the production of CO 2 were monitored. An initial acclimation period of at least 100 days was observed in those microcosms in which significant microbial activity occurred, as determined from decreases in O 2 and CH 4 concentrations and an increase in CO 2 content. Degradation of TCE occurred with O 2 concentrations of 2.7 to 8.7% and CH 4 concentrations of 0.5 to 3.5%. Microcosms that initially contained 10% O 2 and 3% CH 4 showed the greatest microbial activity and the greatest amount of TCE degradation. The greatest rates of TCE degradation occurred when O 2 and CH 4 headspace concentrations reached levels of 7.7 to 8.7% and 1.7 to 2.7%, respectively, which correspond to aqueous concentrations of 2.9 to 3.5 mg/L and 0.4 to 0.6 mg/L, respectively. Over these ranges, TCE degradation rates ranged from 15 to 20 mu g of TCE per kilogram of sediment per day. Analysis of the control microcosms indicated that these TCE degradation rates are much greater than those attributable to experimental variation. The results indicate that the microbial community of the sediment is capable of TCE degradation and that significant rates of degradation can be achieved with obtainable O 2 and CH 4 concentrations.

New Jersey↗
USGS2017

Widespread occurrence and potential for biodegradation of bioactive contaminants in Congaree National Park, USA

Organic contaminants with designed molecular bioactivity, such as pesticides and pharmaceuticals, originate from human and agricultural sources, occur frequently in surface waters, and threaten the structure and function of aquatic and terrestrial ecosystems. Congaree National Park in South Carolina (USA) is a vulnerable park unit due to its location downstream of multiple urban and agricultural contaminant sources and its hydrologic setting, being composed almost entirely of floodplain and aquatic environments. Seventy-two water and sediment samples were collected from 16 sites in Congaree National Park during 2013 to 2015, and analyzed for 199 and 81 targeted organic contaminants, respectively. More than half of these water and sediment analytes were not detected or potentially had natural sources. Pharmaceutical contaminants were detected (49 total) frequently in water throughout Congaree National Park, with higher detection frequencies and concentrations at Congaree and Wateree River sites, downstream from major urban areas. Forty-seven organic wastewater indicator chemicals were detected in water, and 36 were detected in sediment, of which approximately half are distinctly anthropogenic. Endogenous sterols and hormones, which may originate from humans or wildlife, were detected in water and sediment samples throughout Congaree National Park, but synthetic hormones were detected only once, suggesting a comparatively low risk of adverse impacts. Assessment of the biodegradation potentials of 8 14 C-radiolabeled model contaminants indicated poor potentials for some contaminants, particularly under anaerobic sediments conditions.

South Carolina↗
USGS1994

Anaerobic biodegradation of halogenated and nonhalogenated N-, s-, and o-heterocyclic compounds in aquifer slurries

The fate of several halogenated and nonhalogenated heterocyclic compounds in anoxic aquifer slurries was investigated Substrate depletion and methane formation were monitored in serum bottle incubations by HPLC and GC, respectively Pyridine, pyrimidine, thiophene, and furan were not mineralized following an 11-month incubation, but the corresponding carboxylated or oxygenated compounds were That is, >74% of the theoretically expected amount of methane was recovered from nicotinic acid, uracil, or 2-furoic acid Chlorinated derivatives, like 2 chloro- or 6-chloronicotinic acid, as well as 4 chloro- and 5-chlorouracil resisted mineralization However, 5-bromouracil was reductively dehalogenated to stoichiometric amounts of uracil, whereas 2-chloropyrimidine was metabolized to a more polar unidentified compound that resisted further anaerobic biodegradation Microorganisms acclimated to 5-bromouracil were unable to transform 4 chloro or 5 chlorouracil These findings illustrate how the structure of heterocyclic contaminants influences their susceptibility to anaerobic decay

Environmental Toxicology and Chemistry↗
USGS1983

Sterane distribution of solid bitumen pyrolyzates. Changes with biodegradation of crude oil in the Ouachita Mountains, Oklahoma

Solid bitumens (grahamite and impsonite) of southeastern Oklahoma have been shown to originate from near-surface alteration of crude oil ( Curiale , 1981; Curiale and Harrison , 1981). Pyrolysis of these solids has been employed to compare the sterane distribution of geographically proximate oils to that of the bitumens. The ratio of rearranged to regular steranes is higher in the pyrolyzates than in the oils, a finding consistent with a bitumen origin due to biodegradation of oil. The remaining presence of steranes, particularly regular steranes, in the bitumens suggests that sterane occlusion may have occurred prior to or during the alteration process, thus removing tetracyclic compounds from the influence of microbial attack. These data suggest that pyrolysis- GC MS "> GCMS offers a viable approach to correlation problems involving solid bitumens.

Geochimica et Cosmochimica Acta↗