Impacts of woodchip biochar additions on greenhouse gas production and sorption/degradation of two herbicides in a Minnesota soil

A potential abatement to increasing levels of carbon dioxide (CO(2)) in the atmosphere is the use of pyrolysis to convert vegetative biomass into a more stable form of carbon (biochar) that could then be applied to the soil. However, the impacts of pyrolysis biochar on the soil system need to be assessed before initiating large scale biochar applications to agricultural fields. We compared CO(2) respiration, nitrous oxide (N(2)O) production, methane (CH(4)) oxidation and herbicide retention and transformation through laboratory incubations at field capacity in a Minnesota soil (Waukegan silt loam) with and without added biochar. CO(2) originating from the biochar needs to be subtracted from the soil-biochar combination in order to elucidate the impact of biochar on soil respiration. After this correction, biochar amendments reduced CO(2) production for all amendment levels tested (2, 5, 10, 20, 40 and 60% w/w; corresponding to 24-720 tha(-1) field application rates). In addition, biochar additions suppressed N(2)O production at all levels. However, these reductions were only significant at biochar amendment levels >20% w/w. Biochar additions also significantly suppressed ambient CH(4) oxidation at all levels compared to unamended soil. The addition of biochar (5% w/w) to soil increased the sorption of atrazine and acetochlor compared to non-amended soils, resulting in decreased dissipation rates of these herbicides. The recalcitrance of the biochar suggests that it could be a viable carbon sequestration strategy, and might provide substantial net greenhouse gas benefits if the reductions in N(2)O production are lasting.

Anaerobic transformation of 2,4,6-trinitrotoluene (TNT)

A sulfate-reducing bacterium using trinitrotoluene (TNT) as the sole nitrogen source was isolated with pyruvate and sulfate as the energy sources. The organism was able to reduce TNT to triaminotoluene (TAT) in growing cultures and cell suspensions and to further transform TAT to still unknown products. Pyruvate, H2, or carbon monoxide served as the electron donors for the reduction of TNT. The limiting step in TNT conversion to TAT was the reduction of 2,4-diamino-6-nitrotoluene (2,4-DANT) to triaminotoluene. The reduction proceeded via 2,4-diamino-6-hydroxylaminotoluene (DAHAT) as an intermediate. The intermediary formation of DAHAT was only observed in the presence of carbon monoxide or hydroxylamine, respectively. The reduction of DAHAT to triaminotoluene was inhibited by both CO and NH2OH. The inhibitors as well as DANT and DAHAT significantly inhibited sulfide formation from sulfite. The data were taken as evidence for the involvement of dissimilatory sulfite reductase in the reduction of DANT and/or DAHAT to triaminotoluene. Hydrogenase purified from Clostridium pasteurianum and carbon monoxide dehydrogenase partially purified from Clostridium thermoaceticum also catalyzed the reduction of DANT in the presence of methyl viologen or ferredoxin, however, as the main reduction product DAHAT rather than triaminotoluene was formed. The findings could explain the function of CO as an electron donor for the DANT reduction (to DAHAT) and the concomitant inhibitory effect of CO on triaminotoluene formation (from DAHAT) by the inhibition of sulfite reductase.(ABSTRACT TRUNCATED AT 250 WORDS)

Microbial transformation of nitroaromatic compounds in sewage effluent

The transformation of mono- and dinitroaromatic compounds was measured in sewage effluent maintained under aerobic or anaerobic conditions. Most of the nitrobenzene, 3- and 4-nitrobenzoic acids, and 3- and 4-nitrotoluenes and much of the 1,2- and 1,3-dinitrobenzenes disappeared both in the presence and absence of oxygen. Under anaerobiosis, 2,6-dinitrotoluene and 3,5-dinitrobenzoic acid disappeared slowly, but no loss was evident in 28 days in aerated sewage. Aromatic amines did not accumulate during the aerobic decomposition of the mononitro compounds. They did appear in nonsterile, but not in sterile, sewage incubated aerobically with the dinitro compounds and anaerobically with all the chemicals. Analysis by gas chromatography and combined gas chromatography-mass spectrometry showed that aniline was formed from nitrobenzene, toluidine was formed from 3- and 4-nitrotoluenes, and aminobenzoic acid was formed from 3- and 4-nitrobenzoic acids under anaerobiosis, and that nitroaniline was formed from 1,2- and 1,3-dinitrobenzenes, aminonitrotoluene resulted from 2,6-dinitrotoluene, and aminonitrobenzoic acid was a product of 3,5-dinitrobenzoic acid under both conditions. The isomeric forms of the metabolites were not established. Aniline, 4-toluidine, and 4-aminobenzoic acid added to sewage disappeared from aerated nonsterile, but not from sterile, sewage or sewage in the absence of oxygen. 2-Nitroaniline, 2-amino-3-nitrotoluene, and 2-amino-5-nitrobenzoic acid added to sewage persisted for at least 60 days in aerobic or anaerobic conditions. Gas chromatographic and gas chromatographic-mass spectrometric analyses demonstrated that acetanilide and 2-methylquinoline were formed from aniline, 4-methylformanilide and 4-methylacetanilide were formed from 4-toluidine, 2-methylbenzimidazole was a product of 2-nitroaniline, and unidentified benzimidazoles were formed from 2-amino-3-nitrotoluene in the absence of oxygen, and that 2-nitroacetanilide and 2-methyl-6-nitroacetanilide were formed from 2-nitroaniline and 2-amino-3-nitrotoluene, respectively, in the presence or absence of oxygen. It is suggested that the transformations of widely used nitroaromatic compounds should be further studied because of the persistence and possible toxicity of products of their metabolism.

Cloning of novel laccase isozyme genes from Trametes sp. AH28-2 and analyses of their differential expression

Three novel laccase isozyme genes, lacA, lacB, and lacC, have been identified from basidiomycete Trametes sp. AH28-2. These genes display a high similarity with other basidiomycete laccases at the amino acid level. An inferred TATA box and several putative CAAT, MRE, XRE, and CreA consensus sequences were identified in the lacA, lacB, and lacC promoter regions. Different from the TATA boxes of lacA and lacB at about -100, the TATA box of lacC is located at -172. For all the isozymes, copper ion is essential for laccase synthesis in Trametes sp. AH28-2. More interestingly, different aromatic compounds can selectively induce the production of distinct laccase isozymes, with o-toluidine inducing the expression of laccase A (LacA) while 3,5-dihydroxytoluene mainly stimulating the production of laccase B (LacB). Quantitative reverse transcriptase-polymerase chain reaction showed that the accumulation of laccase messenger RNA transcripts is accompanied by the increase of corresponding enzyme activity in cultures. The glucose-repression effect on laccase expression in Trametes sp. AH28-2 was also observed. Furthermore, lower Cu2+ concentration (lower than 0.5 mM) can induce LacA and a novel laccase (LacC), and the latter will disappear when Cu2+ concentration is increased up to 1-2 mM. Upon induction by 3,5-dihydroxytoluene, the ratio of LacA to LacB decreased in the later phase of induction.

Human exposure to mutagenic/carcinogenic heterocyclic amines and comutagenic beta-carbolines

Various kinds of mutagenic and carcinogenic heterocyclic amines (HCAs) are produced by heating protein-rich foods, such as meat and fish. To evaluate the risk of these HCAs in terms of human cancer development, exposure levels must be measured. We therefore analyzed their amounts in various kinds of cooked foods and in urine samples of healthy volunteers living in Tokyo. Based on the obtained quantitative data, daily exposure levels to 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were calculated to be 0.3-3.9 and 0.005-0.3 microgram per person, respectively. Moreover, human DNA samples were analyzed with the 32P-postlabeling method, and colon, rectum and kidney tissues were found to contain an adduct spot corresponding to the standard 5'-pdG-C8-MeIQx by TLC and HPLC, at levels of 14, 18 and 1.8 per 10(10) nucleotides, respectively. The beta-carboline compound, norharman, is produced by heating L-tryptophan, and is known to be present in cooked foods and in cigarette smoke at higher levels than mutagenic and carcinogenic HCAs. While norharman is not itself mutagenic to Salmonella, it does become mutagenic to S. typhimurium TA98 with S9 mix in the presence of non-mutagenic aromatic amines like aniline and o-toluidine. When we examined whether DNA adducts are formed in the DNA of S. typhimurium TA98 by treatment with norharman and aromatic amines using 32P-postlabeling analysis, DNA adduct formation by norharman with aromatic amines was found to be related to the appearance of mutagenicity by norharman with aromatic amines.

Gene expression and microscopic analysis of Arabidopsis exposed to chloroacetanilide herbicides and explosive compounds. A phytoremediation approach

Understanding the function of detoxifying enzymes in plants toward xenobiotics is of major importance for phytoremediation applications. In this work, Arabidopsis (Arabidopsis thaliana; ecotype Columbia) seedlings were exposed to 0.6 mm acetochlor (AOC), 2 mm metolachlor (MOC), 0.6 mm 2,4,6-trinitrotoluene (TNT), and 0.3 mm hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). In vivo glutathione (GSH) conjugation reactions of AOC, MOC, RDX, and TNT were studied in root cells using a multiphoton microscope. In situ labeling with monochlorobimane, used as a competitive compound for conjugation reactions with GSH, confirmed that AOC and MOC are conjugated in Arabidopsis cells. Reverse transcription-PCR established the expression profile of glutathione S-transferases (GSTs) and nitroreductases enzymes. Genes selected for this study were AtGSTF2, AtGSTU1, AtGSTU24, and two isoforms of 12-oxophytodienoate reductase (OPR1 and OPR2). The five transcripts tested were induced by all treatments, but RDX resulted in low induction. The mRNA level of AtGSTU24 showed substantial increase for all chemicals (23-fold induction for AOC, 18-fold for MOC, 5-fold for RDX, and 40-fold for TNT). It appears that GSTs are also involved in the conjugation reactions with metabolites of TNT, and to a lesser extent with RDX. Results indicate that OPR2 is involved in plant metabolism of TNT (11-fold induction), and in oxidative stress when exposed to AOC (7-fold), MOC (9-fold), and RDX (2-fold). This study comprises gene expression analysis of Arabidopsis exposed to RDX and AOC, which are considered significant environmental contaminants, and demonstrates the importance of microscopy methods for phytoremediation investigations.

Plasmid-encoded genes specifying aniline oxidation from Acinetobacter sp. strain YAA

Acinetobacter sp. strain YAA is able to use aniline and o-toluidine as the sole carbon and energy source. This strain has several different plasmids and acridine orange curing suggested that aniline utilization in strain YAA was plasmid-encoded. The gene cluster involved in aniline oxidation was cloned in Escherichia coli JM109 from the total plasmid DNA of strain YAA. A recombinant E. coli containing an 18.5 kb insert fragment showed yellow colouration on aniline-containing plates, indicating the formation of 2-hydroxymuconic semialdehyde from aniline. In addition, subcloning of a 9.0 kb SalI fragment from the insert in E. coli resulted in the accumulation of catechol. Southern hybridization studies indicated that the aniline oxygenase gene (atdA) was present on one of the plasmids, pYA1. These results suggest that in strain YAA aniline is degraded via catechol through a pathway involving meta-cleavage of the benzene-ring by plasmid-encoded genes including atdA.

Biotransformation of 2,4,6-trinitrotoluene (TNT) by a Methanococcus sp. (strain B) isolated from a lake sediment

A mesophilic, irregular coccoid methanogen, which shows close resemblance to Methanococcus sp., was isolated from a sediment sample of St. Joseph Lake located in the University of Notre Dame campus. Formate or hydrogen plus carbon dioxide served as substrate for methanogenesis in a mineral salt medium. This organism was studied for its ability to metabolize 2,4,6-trinitrotoluene (TNT). The result showed that this isolate could transform 100 ppm of TNT within 40-60 days of incubation at 30 degrees C. The main intermediate produced was 2,4-diamino-6-nitrotoluene. The TNT transformation rates were higher in cells grown in hydrogen plus carbon dioxide than in cells grown in formate. The isolate did not use acetate and methanol as sole source of carbon and energy. The organism had an optimal pH range of 6.8-7.2. The optimal growth conditions for this isolate are described.

2,4,6-Trinitrotoluene (TNT) transformation by clostridia isolated from a munition-fed bioreactor: comparison with non-adapted bacteria

Several bacterial strains were examined for their ability to degrade the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). The strains examined included various clostridial strains isolated from a 4-year-old munition enrichment, related clostridial strains obtained from a culture collection, two enteric bacteria, and three lactobacilli. All Clostridium species tested were able to reduce TNT rapidly in a complex medium. In cell suspension experiments, these strains were also able to reduce 2,4-diamino-6-nitrotoluene (DANT) to 2,4,6-triaminotoluene (TAT) and to produce a compound that is not yet identified; thus, they could not be distinguished from one another with regard to the pathway of transformation. The enteric strains and the lactobacilli were able to perform the initial reduction of TNT, but none was capable of reducing DANT in cell suspensions.

Degradation of acetochlor by consortium of two bacterial strains and cloning of a novel amidase gene involved in acetochlor-degrading pathway

Two bacterial strains Sphingobium quisquiliarum DC-2 and Sphingobium baderi DE-13 were isolated from activated sludge. Acetochlor was transformed by S. quisquiliarum DC-2 to a transitory intermediate 2-chloro-N-(2-methyl-6-ethylphenyl)acetamide (CMEPA), which was further transformed to 2-methyl-6-ethylaniline (MEA), and MEA could not be degraded by strain DC-2. S. baderi DE-13, incapable of degrading acetochlor, showed capability of degrading MEA to an intermediate 2-methyl-6-ethylaminophenol (MEAOH). MEAOH was further transformed to 2-methyl-6-ethylbenzoquinoneimine (MEBQI), which was mineralized by strain DE-13. A gene, cmeH, encoding an amidase that catalyzed the amide bond cleavage of CMEPA was cloned from strain DC-2. CmeH was expressed in Escherichia coli BL21 and homogenously purified using Ni-nitrilotriacetic acid affinity. CmeH efficiently hydrolyzed CMEPA and other important herbicide, such as propanil, fenoxaprop-p-ethyl and clodinafop-propargyl.

Bioconversion of 2,4-diamino-6-nitrotoluene to a novel metabolite under anoxic and aerobic conditions

Under nitrate-reducing, nongrowth conditions, a Pseudomonas fluorescens species reduced 2,4,6-trinitrotoluene to aminodinitrotoluenes, which were then further reduced to diaminonitrotoluenes. 2,4-Diamino-6-nitrotoluene (2,4-DANT) was further transformed to a novel metabolite, 4-N-acetylamino-2-amino-6-nitrotoluene (4-N-AcANT), while 2,6-diamino-4-nitrotoluene (2,6-DANT) was persistent. Efforts to further degrade 2,4-DANT and 2,6-DANT under aerobic, nitrogen-limited conditions were unsuccessful; 2,6-DANT remained persistent, and 2,4-DANT was again transformed to the 4-N-AcANT compound.

Biodegrading Two Pesticide Residues in Paddy Plants and the Environment by a Genetically Engineered Approach

Accumulating pesticide (and herbicide) residues in soils have become a serious environmental problem. This study focused on identifying the removal of two widely used pesticides, isoproturon (IPU) and acetochlor (ACT), by a genetically developed paddy (or rice) plant overexpressing an uncharacterized glycosyltransferase (IRGT1). IRGT1 conferred plant resistance to isoproturon-acetochlor, which was manifested by attenuated cellular injury and alleviated toxicity of rice under isoproturon-acetochlor stress. A short-term study showed that IRGT1-transformed lines removed 33.3-48.3% of isoproturon and 39.8-53.5% of acetochlor from the growth medium, with only 59.5-72.1 and 58.9-70.4% of the isoproturon and acetochlor remaining in the plants compared with the levels in untransformed rice. This phenotype was confirmed by IRGT1-expression in yeast ( Pichia pastoris) which grew better and contained less isoproturon-acetochlor than the control cells. A long-term study showed that isoproturon-acetochlor concentrations at all developmental stages were significantly lower in the transformed rice, which contain only 59.3-69.2% (isoproturon) and 51.7-57.4% (acetochlor) of the levels in wild type. In contrast, UPLC-Q-TOF-MS/MS analysis revealed that more isoproturon-acetochlor metabolites were detected in the transformed rice. Sixteen metabolites of isoproturon and 19 metabolites of acetochlor were characterized in rice for Phase I reactions, and 9 isoproturon and 13 acetochlor conjugates were characterized for Phase II reactions in rice; of these, 7 isoproturon and 6 acetochlor metabolites and conjugates were reported in plants for the first time.

Peroxygenation mechanism for chloroperoxidase-catalyzed N-oxidation of arylamines

The metabolism of three arylamine substrates by H2O2 in the presence of each of the peroxidative enzymes chloroperoxidase (CPX) and pea seed peroxygenase (PSM) was conducted with normal H2O2 and with 18O-labeled H2O2. The resulting C-nitroso aromatic metabolites were examined by GC-MS methods to determine the extent of 18O incorporation. The arylamine substrates were p-toluidine, 4-chloroaniline, and 3,4-dichloroaniline. For both enzymes, all three arylamines were found to give quantitative incorporation of 18O into their nitroso metabolites when [18O]H2O2 was the oxidant substrate. The introduction of the oxygen atom into 4-chloronitrosobenzene was found to occur during the first step of this process, since it was found that when (4-chlorophenyl)hydroxylamine was employed as the substrate, no significant incorporation of 18O occurred. These observations prove that CPX and PSM cause N-oxidation of primary arylamines via an oxygen transfer from the compound I activated forms of their heme functional groups. Therefore, these peroxidases are correctly called peroxygenases when acting in such a manner. A discussion of the reaction mechanisms for peroxidases and their relation to cytochrome P-450 oxidations is presented.

Herbicides and herbicide degradates in shallow groundwater and the Cedar River near a municipal well field, Cedar Rapids, Iowa

Water samples were collected near a Cedar Rapids, Iowa municipal well field from June 1998 to August 1998 and analyzed for selected triazine and acetanilide herbicides and degradates. The purpose of the study was to evaluate the occurrence of herbicides and herbicide degradates in the well field during a period following springtime application of herbicides to upstream cropland. The well field is in an alluvial aquifer adjacent to the Cedar River. Parent herbicide concentrations generally were greatest in June, and decreased in July and August. Atrazine was most frequently detected and occurred at the greatest concentrations; acetochlor, cyanazine and metolachlor also were detected, but at lesser concentrations than atrazine. Triazine degradate concentrations were relatively small (< 0.50 microg/l) and generally decreased from June to August. Although the rate of groundwater movement is relatively fast (approx. 1 m per day) in the alluvial aquifer near the Cedar River, deethylatrazine (DEA) to atrazine ratios in groundwater samples collected near the Cedar River indicate that atrazine and DEA probably are gradually transported into the alluvial aquifer from the Cedar River. Deisopropylatrazine (DIA) to DEA ratios in water samples indicate most DIA in the Cedar River and alluvial aquifer is produced by atrazine degradation, although some could be from cyanazine degradation. Acetanilide degradates were detected more frequently and at greater concentrations than their corresponding parent herbicides. Ethanesulfonic-acid (ESA) degradates comprised at least 80% of the total acetanilide-degradate concentrations in samples collected from the Cedar River and alluvial aquifer in June, July and August; oxanilic acid degradates comprised less than 20% of the total concentrations. ESA-degradate concentrations generally were smallest in June and greater in July and August. Acetanilide degradate concentrations in groundwater adjacent to the Cedar River indicate acetanilide degradates are transported into the alluvial aquifer in a manner similar to that indicated for atrazine and DEA.

Two-dimensional fluorometry coupled with artificial neural networks: a novel method for on-line monitoring of complex biological processes

The use of two-dimensional scanning fluorometry as an on-line, noninvasive, in situ bioreactor monitoring technique is extended to complex bioprocesses using mixed cultures, with particular attention to biofilm systems. Using the example of spectra subtraction, it is demonstrated that established methods for fluorescence data analysis have a limited capability of utilizing overall fluorometric information. Artificial neural networks (ANNs) are introduced as a novel nonlinear and nonmechanistic technique for interpreting the highly complex fluorescence maps. It is shown that ANNs are able to infer process performance parameters in a pattern recognition approach, based on the entire fluorescence "fingerprint" of the biological system. The studies were carried out using an extractive membrane bioreactor (EMB) for the degradation of chlorinated organic compounds, operating with mixed cultures. Model pollutants em- ployed were 1,2-dichloroethane, 3-chloro-4-methylaniline, and p-toluidine.

Metabolism of o-[methyl-14C]toluidine in the F344 rat

1. Following a single dose (400 mg/kg s.c.) of o-[methyl-14C]toluidine to male F344 rats, 56% of the 14C was recovered in the 24 h urine, 2.3% in the faeces and 1% as exhaled 14CO2. After 48 h, 83.9% of the 14C appeared in the urine, 3.3% in the faeces and 1.4% was exhaled. 2. Ether-extractable urinary metabolites were separated by h.p.l.c. and identified as: o-toluidine (5.1% dose); azoxytoluene (0.2%); o-nitrosotoluene (less than or equal to 0.1%); N-acetyl-o-toluidine (0.2%); N-acetyl-o-aminobenzyl alcohol (0.3%); 4-amino-m-cresol (0.6%); N-acetyl-4-amino-m-cresol (0.3%); anthranilic acid (0.3%) and N-acetylanthranilic acid (0.3%). 3. Acid-conjugated urinary metabolites (51% of dose), separated by paper electrophoresis and by Sephadex LH-20 chromatography, were identified as sulphates of 4-amino-m-cresol (27.8% dose), N-acetyl-4-amino-m-cresol (8.5%), and 2-amino-m-cresol (2.1%), and glucuronides of 4-amino-m-cresol (2.6%), N-acetyl-4-amino-m-cresol (2.8%) and N-acetyl-o-aminobenzyl alcohol. Evidence for a double acid conjugate of 4-amino-m-cresol was also found. 4. These results show that N-acetylation and hydroxylation at the 4 position of o-toluidine are major metabolic pathways in the rat. Minor pathways include hydroxylation at the 6 position, oxidation of the methyl group and oxidation of the amino group. Sulphate conjugates predominate over glucuronides by a ratio of 6:1.

Upward translocation of acetochlor and atrazine in wheat plants depends on their distribution in roots

Residual acetochlor and atrazine in soils, resulting from their extensive application to maize plants, may affect product safety of the ultimate wheat crop. To determine the potential uptake and accumulation of acetochlor and atrazine by wheat plants, the uptake mechanism, translocation, and subcellular distribution of these two herbicides were studied through hydroponic experiments (10 mg L^-1). The results indicated that acetochlor can be taken up through the apoplastic pathway and can accumulate in wheat roots with little upward translocation. However, atrazine could be taken up by roots through the symplastic pathway and subsequently transported to the stems and leaves. Little upward translocation of acetochlor in wheat plants was due to its preferential distribution into root organelles with higher lipid contents. Conversely, the low bioconcentration of atrazine in root organelles and cell walls after uptake led to its easy upward translocation. Uptake of acetochlor and atrazine by wheat roots and the distribution of atrazine to the stems and leaves were predicted well by using the partition-limited model. The obtained results indicated that residual atrazine in soil may be taken up by wheat roots and acropetally translocated, thereby posing a threat to product safety of wheat.

Degradation of 2-methylaniline and chlorinated isomers of 2-methylaniline by Rhodococcus rhodochrous strain CTM

Rhodococcus rhodochrous strain CTM co-metabolized 2-methylaniline and some of its chlorinated isomers in the presence of ethanol as additional carbon source. Degradation of 2-methylaniline proceeded via 3-methylcatechol, which was metabolized mainly by meta-cleavage. In the case of 3-chloro-2-methylaniline, however, only a small proportion (about 10%) was subjected to meta-cleavage; the chlorinated meta-cleavage product was accumulated in the culture fluid as a dead-end metabolite. In contrast, 4-chloro-2-methylaniline was degraded via ortho-cleavage exclusively. Enzyme assays showed the presence of catechol 1,2-dioxygenase and catechol 2,3-dioxygenase as inducible enzymes in strain CTM. Extended cultivation of strain CTM with 2-methylaniline and 3-chloro-2-methylaniline yielded mutants, including R. rhodochrous strain CTM2, that had lost catechol 2,3-dioxygenase activity; these mutants degraded the aromatic amines exclusively via the ortho-cleavage pathway. DNA hybridization experiments using a gene probe revealed the loss of the catechol 2,3-dioxygenase gene from strain CTM2.

Isolation and Characterization of a Pseudomonas Oleovorans Degrading the Chloroacetamide Herbicide Acetochlor

To date, no pure bacterial cultures that could degrade acetochlor have been described. In this study, one strain of microorganism capable of degrading acetochlor, designated as LCa2, was isolated from acetochlor-contaminated soil. The strain LCa2 is Pseudomonas oleovorans according to the criteria of Bergey's manual of determinative bacteriology and sequence analysis of the partial 16S rRNA gene. Optimum growth temperature and pH were 35 degrees C and 8.0, respectively. The strain could degrade 98.03% of acetochlor treated at a concentration of 7.6 mg l(-1) after 7 days of incubation and could tolerate 200 mg l(-1) of acetochlor. When the acetochlor concentration became higher, the degradation cycle became longer. The acetochlor biodegradation products were identified by GC-MS based on mass spectral data and fragmentation patterns. The main plausible degradative pathways involved dechlorination, hydroxylation, N-dealkylation, C-dealkylation and dehydrogenation.

Degradation of acetochlor by four microbial communities

Four microbial communities capable of degrading acetochlor, designated A, D, E, and J, were obtained from acetochlor-contaminated soil and sludge. Acetochlor at an initial concentration of 55mg/L was completely degraded by the four mixed cultures after 4 days. At 80 mg/L acetochlor, more than 99% degradation was observed with D, 84% with A and E, and 88% with J after 9 days. There are primary eight strains of bacteria in community A, three in community D, E, and J, respectively. No single isolate was able to degrade acetochlor efficiently. The acetochlor biodegradation products were identified by gas chromatography-mass spectrometry. The probable degradative pathways of acetochlor involved dechlorination, hydroxylation, deethoxymethylation, cyclization, carboxylation, and decarboxylation. Propachlor, alachlor, and metolachlor, which are also the main components of the chloroacetanilide herbicide, could be degraded by the four mixed cultures to some degree. Given the high degradation rates observed here, the four mixed cultures obtained may be useful in the degradation processes of acetochlor.

Determination of chloroacetanilide herbicide metabolites in water using high-performance liquid chromatography-diode array detection and high-performance liquid chromatography/mass spectrometry

Analytical methods using high-performance liquid chromatography-diode array detection (HPLC-DAD) and high-performance liquid chromatography/mass spectrometry (HPLC/MS) were developed for the analysis of the following chloroacetanilide herbicide metabolites in water: alachlor ethanesulfonic acid (ESA); alachlor oxanilic acid; acetochlor ESA; acetochlor oxanilic acid; metolachlor ESA; and metolachlor oxanilic acid. Good precision and accuracy were demonstrated for both the HPLC-DAD and HPLC/MS methods in reagent water, surface water, and ground water. The average HPLC-DAD recoveries of the chloroacetanilide herbicide metabolites from water samples spiked at 0.25, 0.5 and 2.0 microg/l ranged from 84 to 112%, with relative standard deviations of 18% or less. The average HPLC/MS recoveries of the metabolites from water samples spiked at 0.05, 0.2 and 2.0 microg/l ranged from 81 to 118%, with relative standard deviations of 20% or less. The limit of quantitation (LOQ) for all metabolites using the HPLC-DAD method was 0.20 microg/l, whereas the LOQ using the HPLC/MS method was at 0.05 microg/l. These metabolite-determination methods are valuable for acquiring information about water quality and the fate and transport of the parent chloroacetanilide herbicides in water.

Quantification of six herbicide metabolites in human urine

We developed a sensitive, selective and precise method for measuring herbicide metabolites in human urine. Our method uses automated liquid delivery of internal standards and acetate buffer and a mixed polarity polymeric phase solid phase extraction of a 2 mL urine sample. The concentrated eluate is analyzed using high-performance liquid chromatography-tandem mass spectrometry. Isotope dilution calibration is used for quantification of all analytes. The limits of detection of our method range from 0.036 to 0.075 ng/mL. The within- and between-day variation in pooled quality control samples range from 2.5 to 9.0% and from 3.2 to 16%, respectively, for all analytes at concentrations ranging from 0.6 to 12 ng/mL. Precision was similar with samples fortified with 0.1 and 0.25 ng/mL that were analyzed in each run. We validated our selective method against a less selective method used previously in our laboratory by analyzing human specimens using both methods. The methods produced results that were in agreement, with no significant bias observed.

Transformations of TNT and related aminotoluenes in groundwater aquifer slurries under different electron-accepting conditions

The transport and fate of pollutants is often governed by both their tendency to sorb as well as their susceptibility to biodegradation. We have evaluated these parameters for 2,4,6-trinitrotoluene (TNT) and several biodegradation products. Slurries of aquifer sediment and groundwater depleted TNT at rates of 27, 7.7 and 5.9 microM day-1 under methanogenic, sulfate-reducing and nitrate-reducing conditions, respectively. Abiotic losses of TNT were determined in autoclaved controls. Abiotic TNT loss and subsequent transformation of the products was also observed. These transformations were especially important during the first step in the reduction of TNT. Subsequent abiotic reactions could account for all of the transformations observed in bottles which were initially nitrate-reducing. Other controls removed TNT reduction products at much slower rates than slurries containing live organisms. 2-Amino-4,6-dinitrotoluene was produced in all slurries but disappeared in methanogenic and in sulfate-reducing slurries within several weeks. This compound was converted to 2,4-diamino-6-nitrotoluene in all slurries with subsequent removal of the latter from methanogenic and sulfate-reducing slurries, while it persisted in autoclaved controls and in the nitrate-reducing slurries. Aquifer slurries incubated with either 2,4- or 2,6-diaminotoluene showed losses of these compounds relative to autoclaved controls under nitrate-reducing conditions but not under sulfate-reducing or methanogenic conditions. These latter compounds are important as reduced intermediates in the biodegradation of dinitrotoluenes and as industrial chemicals. In experiments to examine sorption, exposure to landfill sediment resulted in losses of approximately 15% of diaminotoluene isomers and 25% of aminodinitrotoluene isomers from initial solution concentrations within 24 h. Isotherms confirmed that the diaminotoluenes were least strongly sorbed and the amino-dinitrotoluenes most strongly sorbed to this sediment, while TNT sorption capacity was intermediate. In our studies, 2,4,6-triaminotoluene sorption capacity was indeterminate due to its chemical instability. Coupled with biodegradation information, isotherms help describe the likelihood of contaminant removal, persistence, and movement at impacted sites.

Physical map of the aromatic amine and m-toluate catabolic plasmid pTDN1 in Pseudomonas putida: location of a unique meta-cleavage pathway

A restriction endonuclease map was derived for the aromatic amine and m-toluate catabolic plasmid pTDN1 present in Pseudomonas putida UCC22, a derivative of P. putida mt-2. The plasmid is 79 +/- 1 kbp in size and can be divided into a restriction-site-deficient region of 51 +/- 1 kbp and a restriction-site-profuse region of 28 kbp which begins and ends with directly repeating sequences of at least 2 kbp in length. A mutant plasmid isolated after growth of the host on benzoate had lost the restriction-profuse region by a straightforward recombinational loss retaining one copy of the direct repeat. Analysis of clones, deletion and Tn5 insertion mutants strongly suggested that the meta-cleavage pathway of pTDN1 was situated in the region readily deleted. The catechol 2,3-dioxygenase (C23O) gene of pTDN1 showed no hybridization or restriction homology to previously described C23O genes of TOL plasmids pWW0 and pWW15. In addition, there was little homology between intact pTDN1, pWW0 and pWW15, suggesting the presence of a unique meta-cleavage pathway. We also demonstrated that pTDN1 did not originate from P. putida mt-2 chromosome.

Formation of DNA adducts by the co-mutagen norharman with aromatic amines

Norharman, widely distributed in our environment, is alone not mutagenic to Salmonella typhimurium TA98 and TA100 either with or without S9 mix, but becomes mutagenic to S.typhimurium TA98 with S9 mix when non-mutagenic aromatic amines like aniline or o- or m-toluidine are added. Thus norharman has been called a 'co-mutagen'. In the present study we examined whether or not DNA adducts are formed in DNA of S.typhimurium TA98 by treatment with norharman and aromatic amines using 32P-post-labeling analysis under modified adduct intensification conditions. When a sample of norharman (8 mg) and aniline (4 mg) was incubated with 4 ml of overnight culture of S.typhimurium TA98 in the presence of 20 ml S9 mix for 6 h at 37 degrees C, three adduct spots were detected at a total relative adduct labeling (RAL) of 10.8 +/- 2.27/10(8) nucleotides. Under the same conditions, a mixture of norharman (8 mg) and o-toluidine (4 mg) yielded three adduct spots at a RAL of 3.74 +/- 1.71/10(8) nucleotides. With a combination of norharman and m-toluidine, a single adduct spot was seen at a RAL of 0.04 +/- 0.01/10(8) nucleotides. In contrast, norharman with p-toluidine did not produce adduct spots. Furthermore, neither norharman nor the aromatic amines themselves gave any evidence of adducts. Thus DNA adduct formation by norharman with aromatic amines correlates with the co-mutagenic action of norharman in S.typhimurium TA98.