Atrazine mineralization potential of alluvial-aquifer sediments under aerobic conditions

McMahon, Peter B.; Chapelle, Francis H.; Jagucki, Martha L.

doi:10.1021/es00032a010

Cited by 60 publications

(39 citation statements)

References 9 publications

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“…In another study involving the mineralization of CLA in sediment samples, the rate constants were estimated to be in the range of <4.5x10 -s to 5.4x10 -4 d -1 (McMahon et al, 1992). However, the P,~a~ values of CLA mineralization in these experiments were less than 1.5% of the added CLA.…”

Section: Discussionmentioning

confidence: 79%

“…Samples showing degradative activity had halflives exceeding 170 d. Slow biodegradation rates were considered to be primarily due to a low density of atrazine-degrading microorganisms in over 80 samples examined (Radosevich et al, 1993). In a similar study with subsurface samples from the same site, McMahon et al (1992) reported laboratory-measured mineralization rate constants in the range of <4.5x10 -5 to 5.4x10 -4 d -1 for [2Jac-ethyl]-atrazine. They concluded that dealkylation of atrazine was significant with respect to the temporal scale of ground water movement at the site.…”

Section: Introductionmentioning

confidence: 86%

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Biodegradation of atrazine in surface soils and subsurface sediments collected from an agricultural research farm

1996

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The purpose of the present study was to assess atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) mineralization by indigenous microbial communities and to investigate constraints associated with atrazine biodegradation in environmental samples collected from surface soil and subsurface zones at an agricultural site in Ohio. Atrazine mineralization in soil and sediment samples was monitored as 14CO2 evolution in biometers which were amended with 14C-labeled atrazine. Variables of interest were the position of the label ([U-14C-ring]-atrazine and [2-14C-ethyl]-atrazine), incubation temperature (25 degrees C and 10 degrees C), inoculation with a previously characterized atrazine-mineralizing bacterial isolate (M91-3), and the effect of sterilization prior to inoculation. In uninoculated biometers, mineralization rate constants declined with increasing sample depth. First-order mineralization rate constants were somewhat lower for [2-14C-ethyl]-atrazine when compared to those of [U-14C-ring]-atrazine. Moreover, the total amount of 14CO2 released was less with [2-14C-ethyl]-atrazine. Mineralization at 10 degrees C was slow and linear. In inoculated biometers, less 14CO2 was released in [2-14C-ethyl]-atrazine experiments as compared with [U-14C-ring]-atrazine probably as a result of assimilatory incorporation of 14C into biomass. The mineralization rate constants (k) and overall extents of mineralization (Pmax) were higher in biometers that were not sterilized prior to inoculation, suggesting that the native microbial populations in the sediments were contributing to the overall release of 14CO2 from [U-14C-ring]-atrazine and [2-14C-ethyl]-atrazine. A positive correlation between k and aqueous phase atrazine concentrations (Ceq) in the biometers was observed at 25 degrees C, suggesting that sorption of atrazine influenced mineralization rates. The sorption effect on atrazine mineralization was greatly diminished at 10 degrees C. It was concluded that sorption can limit biodegradation rates of weakly-sorbing solutes at high solid-to-solution ratios and at ambient surface temperatures if an active degrading population is present. Under vadose zone and subsurface aquifer conditions, however, low temperatures and the lack of degrading organisms are likely to be primary factors limiting the biodegradation of atrazine.

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Section: Discussionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 86%

Biodegradation of atrazine in surface soils and subsurface sediments collected from an agricultural research farm

1996

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“…Atrazine was detected (g0.05 µg/L) in 22.4%, and atrazine or its two metabolites were detected in 26.4% of the 303 wells sampled. The more even distribution between atrazine and its metabolites than determined for alachlor is related to the slow degradation rates for atrazine, particularly under hypoxic conditions (39,(43)(44)(45)(46), which allows more of the parent compound to be transported to near-surface aquifers.…”

Section: Resultsmentioning

confidence: 99%

Occurrence of Selected Pesticides and Their Metabolites in Near-Surface Aquifers of the Midwestern United States

Kolpin

Thurman

Goolsby

1995

Environ. Sci. Technol.

236

162

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The occurrence and distribution of selected pesticides and their metabolites were investigated through the collection of 837 water-quality samples from 303 wells across the Midwest. Results of this study showed that five of the six most frequently detected compounds were pesticide metabolites. Thus, it was common for a metabolite to be found more frequently in groundwater than its parent compound. The metabolite alachlor ethanesulfonic acid (alachlor-ESA; 2-[(2,6-diethylphenyl)(methoxymethyl)amino]-2-oxoethanesulfonic acid) was detected almost 10 times as frequently and at much higher concentrations than its parent compound alachlor (2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetamide). The median detectable atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) concentration was almost half that of atrazine residue (atrazine plus the two atrazine metabolites analyzed). Cyanazine amide [2-chloro-4-(1-carbamoyl-1-methylethylamino)-6-ethylamino-s-triazine] was detected almost twice as frequently as cyanazine (2-chloro-4-ethylamino-6-methylpropionitrileamino-s-triazine). Results show that information on pesticide metabolites is necessary to understand the environmental fate of pesticides. Consequently, if pesticide metabolites are not quantified, the effects of chemical use on groundwater quality would be substantially underestimated. Thus, continued research is needed to identify major degradation pathways for all pesticides and to develop analytical methods to determine their concentrations in water and other environmental media.

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“…No dealkylation of atrazine was observed in 70 days in laboratory studies conducted by inoculating cement-grade sand with aquifer microbes at 13 or 28°C (Wehtje et al, 1983). McMahon et al (1992) observed no mineralization of the triazine ring in 23 days, with some dealkylation to DIA [2-amino-4-chloro-6-(ethylamino)-1,3,5-triazine] in systems containing shallow aquifer sediments; deeper sediments exhibited less dealkylation. Vanderheyden et al (1997) observed rapid degradation of atrazine in sediment samples collected from the saturated zone, and the metabolites were unidentified; mineralization of [ 14 C]atrazine began after a lag phase of ∼25 days and ∼25% of the applied [ 14 C]atrazine was mineralized in 75 days.…”

Section: Introductionmentioning

confidence: 96%

“…Mineralization of the triazine ring is generally slower and less extensive than dealkylation (McMahon et al, 1992;Schnoor, 1992, 1994). Mirgain et al (1993) isolated a bacterium that could degrade atrazine and also identified an apparent synergistic relationship between two bacteria that could degrade atrazine together.…”

Section: Introductionmentioning

confidence: 99%

Atrazine, Deethylatrazine, and Deisopropylatrazine Persistence Measured in Groundwater in Situ under Low-Oxygen Conditions

Papiernik

Spalding

1998

J. Agric. Food Chem.

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The degradation of atrazine [2-chloro-4-(ethylamino)-6-isopropylamino-1,3,5-triazine], deethylatrazine [DEA; 2-amino-4-chloro-6-(isopropylamino)-1,3,5-triazine], and deisopropylatrazine [DIA; 2-amino-4-chloro-6-(ethylamino)-1,3,5-triazine] was assessed under limited oxygen conditions using in situ microcosms. Denitrification was induced in a shallow sand and gravel aquifer to measure the potential for degradation of atrazine, DEA, and DIA under low-O 2 conditions. The dissolved oxygen content decreased from 7-8 mg/L to e1 mg/L within 4 days and remained j3 mg/L for the remainder of the 45-day experiment. Atrazine, DEA, and DIA concentrations (normalized to the bromide concentration at each sampling time to account for dilution) did not show a significant decrease with time, indicating that these compounds are relatively stable under the low-O 2 conditions induced in the aquifer. Although removal of one alkyl group has been proposed as the rate-limiting step in atrazine degradation, no transformation of either monodealkylated metabolite (DEA or DIA) was observed in this study.

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Atrazine mineralization potential of alluvial-aquifer sediments under aerobic conditions

Cited by 60 publications

References 9 publications

Biodegradation of atrazine in surface soils and subsurface sediments collected from an agricultural research farm

Biodegradation of atrazine in surface soils and subsurface sediments collected from an agricultural research farm

Occurrence of Selected Pesticides and Their Metabolites in Near-Surface Aquifers of the Midwestern United States

Atrazine, Deethylatrazine, and Deisopropylatrazine Persistence Measured in Groundwater in Situ under Low-Oxygen Conditions

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