Deisopropylatrazine Research Articles

ATRAZINE AND CARBOFURAN TRANSPORT THROUGH THE VADOSE ZONE IN THE CLAIBORNE AQUIFER RECHARGE AREA<

A 1-ha field plot with a sandy surface soil, located near Plains, Georgia, was studied for three years (from1993 to 1995) to evaluate pesticide transport in the vadose zone. Vadose zone soil samples were collected 23 times: priorto the initial 1993 pesticide application, each year at approximately 1, 3, 7, 14, 28, and 44 days after pesticideapplication, each fall after harvest, and in the spring of 1995 prior to planting. The samples were analyzed for atrazine,carbofuran, deethylatrazine (DEA), and deisopropylatrazine (DIA). Atrazine and carbofuran in the active root zone(< 100 cm) degraded rapidly. Overall, the higher concentration levels of atrazine, DEA, DIA, and carbofuran werelimited to the top 25 cm of the profile and to the period from 1 to 30 days after application. On the average, by 30 daysafter application 83% of the atrazine and 96% of the carbofuran had degraded. By 44 days after application, virtually allof the pesticides in the top 250 cm of the soil had degraded. Atrazine was found to be more persistent than wascarbofuran with a half life approximately twice that for carbofuran. A two-stage model with a variable dissipation ratefor the period up to 44 days after pesticide application and a second dissipation rate for periods greater than that wasfound to fit the data better than a single stage model. For the first 44 days after application, the first-order decay ratewith a half life of 12 days was found to fit the field data for atrazine within the soil profile. A first-order decay rate with ahalf life of approximately 6 days fit the observed carbofuran data best. The dissipation rate decreased rapidly after thefirst 44 days. When a two-stage dissipation process was assumed, the dissipation rate coefficient decreased from 0.059 to0.006 (days 1 ) for atrazine, while for carbofuran it decreased from 0.110 to 0.018 (days 1 ). Observed levels of theatrazine metabolites DIA and DEA were highest in the top 1 cm of the soil. There appeared to be some movement orcreation of the metabolites at lower depths in the profile later in the growing season, but not at large concentrations.

Hydroxyatrazine in soils and sediments.

Hydroxyatrazine (HA) is the major metabolite of atrazine in most surface soils. Knowledge of HA sorption to soils, and its pattern of stream water contamination suggest that it is persistent in the environment. Soils with different atrazine use histories were collected from four sites, and sediments were collected from an agricultural watershed. Samples were exhaustively extracted with a mixed-mode extractant, and HA was quantitated using high performance liquid chromatography with UV detection. Atrazine, deethylatrazine (DEA), and deisopropylatrazine (DIA) were also measured in all samples. Concentrations of HA were considerably greater than concentrations of atrazine, DEA, and DIA in all soils and sediments studied. Soil concentrations of HA ranged from 14 to 640 μg/kg with a median concentration of 84 μg/kg. Sediment concentrations of HA ranged from 11 to 96 μg/kg, with a median concentration of 14 μg/kg. Correlations of HA and atrazine concentrations to soil properties indicated that HA levels in soils were controlled by sorption of atrazine. Because atrazine hydrolysis is known to be enhanced by sorption and pH extremes, soils with high organic matter (OM) and clay content and low pH will result in greater atrazine sorption and subsequent hydrolysis. Significant correlation of HA concentrations to OM, pH, and cation exchange capacity of sediments indicated that mixed-mode sorption (i.e., binding by cation exchange and hydrophobic interactions) was the mechanism controlling HA levels in sediment. The presence of HA in soils and stream sediments at the levels observed support existing hypotheses regarding its transport in surface runoff. These results also indicated that persistence of HA in terrestrial and aquatic ecosystems is an additional risk factor associated with atrazine usage.

Analysis of atrazine, terbutylazine and their N-dealkylated chloro and hydroxy metabolites by solid-phase extraction and gas chromatography–mass spectrometry and capillary electrophoresis–ultraviolet detection

Solid-phase extraction (SPE) with the styrene–divinylbenzene adsorbent LiChrolut EN was investigated for the extraction of the s-triazine herbicides atrazine and terbutylazine, their polar N-dealkylated degradation products deethylatrazine (DEA), deisopropylatrazine (DIA) and deethylterbutylazine (DET) and for the hydrophilic hydroxytriazine degradation products (HTDPs) hydroxyatrazine (HA), hydroxyterbutylazine (HT), deethylhydroxyatrazine (DEHA), deisopropylhydroxyatrazine (DIHA) and deethyldeisopropylhydroxyatrazine (ameline). The optimum pH value for the extraction of the HTDPs from fortified tap water at 2 μg/l is 3.0. Recovery values with 200 mg LiChrolut EN are >80% for HA, HT, DEHA and 30% for DIHA from 200 ml spiked tap and river water. Atrazine, terbutylazine, DEA, DIA and DET are quantitatively extracted by LiChrolut EN. The chlorotriazines are analyzed by GC–MS and the HTDPs by capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC) with an acetate buffer at pH 4.6 or a sodium borate–sodium dodecyl sulfate buffer at pH 9.3. The combined method of SPE enrichment and CE analysis allows the determination of HTDPs in the low μg/l range.

In vitro biotransformation of atrazine by rat liver microsomal cytochrome P450 enzymes

We studied atrazine (ATZ) metabolism in male and female rat liver microsomes in vitro, and the major metabolite was deisopropylatrazine (DeiPr-ATZ) with deethylatrazine (DeEt-ATZ) and 1-hydroxyisopropylatrazine (iPrOH-ATZ) as minor metabolites in both sexes. The enzyme kinetics of ATZ biotransformation were examined by means of Eadie–Hofstee analyses. Although no remarkable sex difference of Michaelis–Menten values for each pathway was observed, Cl ints ( V max/ K m) for DeiPr-ATZ, DeEt-ATZ and iPrOH-ATZ were slightly higher in female than in male rats. The formation of DeiPr-ATZ, DeEt-ATZ and iPrOH-ATZ from ATZ was substantially inhibited by SKF-525A, metyrapone, diallyl sulfide, 7-ethoxycoumarin, benzphetamine, nicotine, testosterone and lauric acid in both sexes. Cimetidine effectively inhibited the formation of all metabolites in male rats. On the other hand, the inhibition rates of the formation of DeiPr-ATZ and iPrOH-ATZ by cimetidine in female rats were lower than those in male rats, and DeEt-ATZ was hardly affected by the chemicals. In contrast with the results for cimetidine, the inhibition of ATZ biotransformation by bufuralol was more effective in female than in male rats. Anti-rat CYP2B1 and CYP2E1 antibodies effectively inhibited DeiPr-ATZ, DeEt-ATZ and iPrOH-ATZ formations in both sexes. Anti-rat CYP2C11 antibody also inhibited the three metabolites in both sexes, with the inhibition rates higher in male than in female rats, similar to cimetidine. In the case of anti-rat CYP2D1 antibody, the inhibitory effect on ATZ biotransformation in male rats was less than that in female rats. On the other hand, anti-rat CYP1A2, CYP3A2 and CYP4A1 antibodies did not affect the ATZ biotransformation in either sex. There was no significant correlation between the formation rate of ATZ metabolites and P450 isoform levels in either sex. These results may mean that CYP2B2, CYP2C11, CYP2D1 (only iPrOH-ATZ formation) and CYP2E1 in male rats, and CYP2B2, CYP2D1 and CYP2E1 in female rats are involved ATZ metabolism in liver, and that the substrate specificity of P450 isoforms for ATZ is broad.

Atrazine, alachlor, and total inorganic nitrogen concentrations of winter wind‐eroded sediment samples1

The objective of this study was to determine if atrazine (2‐chloro‐4‐ethylamino‐6‐isopropyl‐1,3,5‐triazine), alachlor [2‐chloro‐N‐(2,6‐diethylphenyl‐N‐(methoxymethyl)acetamide], or inorganic nitrogen was present on wind‐eroded sediments collected from road ditch areas in mid to late winter. Sediment samples that had been deposited in ditches on top of snow were collected during the winters of 1994, 1995, and 1996 at randomly selected sites in eastern South Dakota and western Minnesota. Atrazine, atrazine metabolites [deethylatrazine (DEA)(6‐chloro‐N‐l‐methylethyl‐l,3,5‐triazine‐2,4‐diamine], and deisopropylatrazine (DIA) (6‐chloro‐N‐ethyl‐l,3,5‐triazine‐2,4‐diamine), and alachlor were determined by gas chromatography. Total inorganic N (NO3 ‐ + NH4 +) concentration was determined with a nitrogen analyzer. In all years, atrazine was detected in at least 72% of the samples, with a mean concentration of 8.9 ug kg‐1 and, while DEA was detected in at least 18% of the samples. Alachlor was detected in at least 27% of the soil samples for all three years with mean sediment concentration of >5 ug kg‐1. Inorganic N concentration of all samples averaged 33 mg kg‐1. These data suggest that deposition of wind‐eroded sediment contributes to nonpoint source contamination of nontarget areas by agrichemicals.

Aqueous degradation of atrazine and some of its main by-products with ozone/hydrogen peroxide

This laboratory study was designed to investigate the removal of atrazine (ATZ) and its first main by-products, deethylatrazine (DEA) and deisopropylatrazine (DIA) by O 3 /H 2 O 2 . At least 76% of the oxidation rate of atrazine is due to free radical reactions. At neutral pH and 20°C, an initial hydrogen peroxide concentration of 10 -3 M is optimum to reach a maximum oxidation rate of these compounds. Experimental results of oxidation in the presence of high hydrogen peroxide concentrations allow the mass transfer coefficient of ozonation to be determined. This coefficient, reactor flow analysis and kinetic data obtained have been applied to mol balance equations of atrazine, deisopropylatrazine, deethylatrazine, ozone (both in the gas and water) and hydrogen peroxide to obtain their corresponding concentrations at different conditions.

Comparison of the leaching properties of alachlor, metolachlor, triazines and some of their metabolites in an experimental field

Alachlor, metolachlor, atrazine, cyanazine, simazine and terbuthylazine were applied to plots containing a drainage system in order to determine the concentrations of parent compounds and their metabolites in soil and in leachate samples. The results indicated that all these herbicides disappeared substancially in the soil surface layer following first order kinetics. In the surface soil, the disappearance times of 50% of the concentration (DT50s) for terbuthylazine, atrazine, metolachlor, cyanazine, simazine and alachlor were 44, 35, 34, 28, 28 and 20 days, respectively. All pesticides leached to a depth of about 90 cm in the soil. After application at agricultural doses, leachate concentrations of herbicides ranged from 24 μg/l for metolachlor to 128 μg/l for cyanazine. The recoveries of the initial amount of compounds added ranged from 0.03% for metolachlor to 0.3% for simazine and its metabolite, deisopropylatrazine (DIA). Of particular interest was the high rate of formation of DIA from simazine and of desethylterbuthlazine (DET) from terbuthylazine. In the leachate, DIA occurred at concentrations much higher than simazine.

Contribution of Hydroxylated Atrazine Degradation Products to the Total Atrazine Load in Midwestern Streams

The contribution of hydroxylated atrazine degradation products (HADPs) to the total atrazine load (i.e., atrazine plus stable metabolites) in streams needs to be determined in order to fully assess the impact of atrazine contamination on stream ecosystems and human health. The objectives of this study were (1) to determine the contribution of HADPs to the total atrazine load in streams of nine midwestern states and (2) to discuss the mechanisms controlling the concentrations of HADPs in streams. Stream samples were collected from 95 streams in northern Missouri at preplant and postplant of 1994 and 1995, and an additional 46 streams were sampled in eight midwestern states at postplant of 1995. Samples were analyzed for atrazine, deethylatrazine (DEA), deisopropylatrazine (DIA), and three HADPs. Overall, HADP prevalence (i.e., frequency of detection) ranged from 87 to 100% for hydroxyatrazine (HA), 0 to 58% for deethylhydroxyatrazine (DEHA), and 0% for deisopropylhydroxyatrazine (DIHA) with method detectio...

Atrazine mineralisation in New Zealand topsoils and subsoils: influence of edaphic factors and numbers of atrazine-degrading microbes

The mineralisation of 14C-ring-labelled atrazine to 14CO2 was measured in 3 contrasting New Zealand soils under controlled conditions of temperature and moisture. The numbers of atrazine-degrading organisms were measured by a most probable number technique. Decomposition rates were slow, with a maximum of 41% of atrazine being mineralised over 263 days. Mineralisation was generally very low in subsoils and was much reduced by low moisture content. However, one subsoil from 60–90 cm depth had unusually high numbers of atrazine-degrading microbes and showed mineralisation greater than or equivalent to the surface soil. Mineralisation was approximately doubled by a 10°C rise in temperature over the range 16–28°C. In general, the rate of atrazine mineralisation over 7–96 days could be predicted from the number of atrazine-degrading microbes and the cation exchange capacity of the soil (R2 = 0·86). A large amount (54–77%) of 14C remained in the soil as non-extractable residues after 263 days, but only trace amounts of the added atrazine or the decomposition products de-ethyl atrazine and de-isopropyl atrazine were detected by extraction in organic solvent.

Microextraction procedures combined with large volume injection in capillary gas chromatography for the determination of pesticide residues in environmental aqueous samples

Liquid–liquid microextraction and solid-phase extraction procedures combined with large volume on-column injection (100–150 μl) in capillary gas chromatography with nitrogen phosphorus detector have been applied to the determination of six triazine herbicides (atrazine, simazine, terbutylazine, terbumeton, metribuzin and terbutryn) and two transformation products (deethyl and deisopropyl atrazine) in water samples. A simple and fast off-line liquid–liquid microextraction procedure (5 ml water/1 ml methyl tert butyl ether) was applied to surface water samples spiked at 0.5 μg l −1 level with good recoveries (> 90%) and repeatability (better than 9%) giving detection limits < 0.1 μg l −1. The application of a solid-phase extraction procedure (10–50 ml of water samples passed through 200 mg C 18 cartridges) allowed the quantitative recovery of all pesticides studied with coefficients of variation lower than 11%. Limits of detection for 50 ml sample volume ranged from 10 to 40 ng l −1. Surface water samples have been analyzed using C 18 SPE (10 ml of water sample) combined with large volume injection (150 μl) and the results compared with those obtained with conventional LLE (500 ml of water sample extracted with 2 × 50 ml dichloromethane), showing good match between them.

Optimizing recoveries of two chlorotriazine herbicide metabolites and 11 pesticides from aqueous samples using solid-phase extraction and gas chromatography–mass spectrometry

A method was developed for solid-phase extraction of two chlorotriazine herbicide metabolites, deethylatrazine (DEA) and deisopropylatrazine (DIA), from aqueous samples. Two C 18 phases in cartridge format were compared and recoveries were found to be highly sensitive to sorbent amount, sample volume and presence of parent compounds. Recoveries were significantly improved using a partially non-endcapped C 18 phase compared to the normal C 18 phase, particularly for DIA, apparently due to polar interactions. Combinations of sample volume and sorbent amount were tested using deionized water to determine an optimal combination of 200 ml and 1.0 g, respectively. Recoveries from a variety of river, stream, runoff and ground waters averaged 105–116% and 109–117% at concentrations of 0.5–1.0 ng/ml for DIA and DEA, respectively, with minimum detection limits of 0.05 ng/ml. Other pesticides tested also have acceptable recoveries using this method.

Comparative Fates of Atrazine and Deethylatrazine in Sterile and Nonsterile Soils

AbstractAssessment of biotic and abiotic mechanisms of atrazine (ATR) and deethylatrazine (DEA) breakdown is necessary to identify major degradation pathways and understand soil conditions necessary for these mechanisms to occur. Our purpose was to compare fates of ATR and DEA in laboratory radiotracer studies to elucidate the effects of soil moisture status and soil depth on degradation and persistence. Atrazine and DEA were more persistent in subsurface soil than in surface soil. After 120‐d incubation, bound residues were significantly greater in surface soils than in subsurface soils. In 14C‐DEA‐treated soil, biological activity contributed to decreased persistence of DEA in saturated surface soil in contrast with unsaturated surface soil after 60 d. Biological activity also contributed to decreased persistence of ATR in saturated subsurface soil in contrast with unsaturated subsurface soil after 120 d, and the decreased persistence corresponded to significantly greater amounts of DEA, deisopropylatrazine (DIA), and polar degradation products compared with other treatments. The percentage of applied 14C‐ATR that degraded to DEA and DIA increased approximately threefold during the 60‐ to 120‐d incubation in nonsterile saturated subsurface soil. Greater quantities of polar degradation products were formed in 14C‐DEA‐treated nonsterile compared with sterile soils. Half‐lives (from first‐order degradation rate constants) of ATR and DEA were significantly longer in subsurface soil compared with surface soils. Biotic mechanisms contributed to the half‐lives of ATR (in surface and subsurface soil) and DEA (in subsurface soil) being significantly shorter under saturated soil moisture conditions compared with unsaturated soil moisture conditions.

Adsorption and Desorption of Atrazine, Deethylatrazine, Deisopropylatrazine, Hydroxyatrazine, and Metolachlor in Two Soils from Virginia

The objective of this study is to characterize the adsorption-desorption properties of atrazine, deethylatrazine (DEA), deisopropylatrazine (DIA), hydroxyatrazine (HA), and metolachlor in the Emporia (fine loamy, siliceous, thermic Typic Hapludult) and Cullen (clayey, mixed, thermic Typic Hapludult) soils. Adsorption and desorption isotherms were determined using the batch equilibrium procedure. Four solution concentrations (2.5, 7.5, 13.2, and 26.4 µmol L−1) were prepared of each chemical and four 24-h desorption periods at each concentration followed immediately after the adsorption process. Organic carbon distribution coefficients (Koc ranged from 140 to 234 for atrazine, 80 to 110 for DEA, 128 to 130 for DIA, 493 to 609 for HA, and 162 to 190 for metolachlor. For desorption, all chemicals exhibited hysteresis. Hysteresis was quantified: ω = [1/nads ÷ 1/ndes − 1] × 100. Soil type affected the degree of atrazine, DEA, and metolachlor hysteresis (ω), and initial concentration had a significant effect on ω only in the Cullen soil. The amount of chemical desorbed, expressed as the percentage of the amount adsorbed, was about 60% for DEA, 43% for atrazine, 40% for metolachlor, 37% for DIA, and 31 and 17% for HA on the Emporia and Cullen soils, respectively. Soil type and initial concentration had no significant effect on the percentage of chemical desorbed except for HA. The sorption properties for atrazine and metolachlor in these soils are similar. The tendency of HA to leach will be low in these soils compared with atrazine, while the tendency of DEA to leach will be high.

Effect of Various Materials in Multilevel Samplers on Monitoring Commonly Occurring Agrichemicals in Ground Water

AbstractStudies have shown that materials, such us polytetra‐fluoroethylene (PTFE), rigid polyvinyl chloride (rigid PVC). flexible polyvinyl chloride (flexible PVC), stainless steel (SS). low‐density polyethylene (LDPE), and high‐density polyethylene (HDPE), have the potential to influence certain analyte concentrations in ground water samples. The effects of HDPE, LDPE, PTFE, rigid PVC, and SS on aqueous concentrations of nitrate‐N, atrazine, deethylatrazine (DEA), and deisopropylatrazine (DIA) were evaluated in a field study A laboratory study was conducted to evaluate sorption of atrazine DEA, DIA, cyanazine, alachlor, metolachlor, and butachlor to PTFE, HDPE, and SS materials. Butachlor is rarely use in the United States, but was included because of its expected high sorptivity. No significant differences between HDPE, LDPE, PTFE, rigid PVC, and SS were determined for any of the analytes tested in the field study. In the laboratory study, sorption of DIA to PTFE and SS was significant at 2.6 × 10−5 and 4.1 × 10−5μg/m2 respectively. Sorption of DIAA to HDPE was not significantly &gt; 0 sorption of all other compounds to HDPE, PTFE, and SS were also not significantly &gt;0. Results of the two studies indicate that for these analytes (relatively polar or ionized compounds), representative ground water samples are not dependent on the materials used for multilevel sampler construction. When considering these compounds, it appears that the least expensive materials (HDPE, rigid PVC, and LDPE) are good choices for the construction of ground water monitoring wells.

Adsorption and Desorption of Atrazine, Deethylatrazine, Deisopropylatrazine, and Hydroxyatrazine on Levy Wetland Soil

The adsorption and desorption of atrazine, and its three metabolites, deethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA), on Levy wetland soil were measured using the batch equilibration technique. Solution concentrations for each chemical were 1.3, 3.8, 6.6, and 13.2 μmol L-1. Four 24-h period desorptions for each concentration were conducted immediately after adsorption. The adsorption of all the chemicals conformed to linear isotherms. Adsorption coefficients decreased in the order HA (109.7) > atrazine (38.6) > DIA (26.3) > DEA (22.1). The organic carbon partition coefficients (Koc) for HA, atrazine, DIA, and DEA were 1500, 440, 290, and 240 L kg-1, respectively. Percent of chemical desorbed was about 29% for DEA, 24% for atrazine, 23% for DIA, and 16% for HA. The slopes of all desorption isotherms were less than their respective adsorption slopes, indicating hysteresis. Atrazine and its metabolites were relatively more strongly adsorbed and the binding was less reversible in t...

Fate of 14C-Atrazine in a Silt Loam Soil

Abstract Formation of 14C-atruzine degradation products and their distribution in the top 90 cm of a silt loam soil was determined during 16 months in the field. After 16 months. 68% of the applied 14C was still present in the soil. By 12 months after treatment (MAT). 14C leached to 70–80 cm. Atrazine accounted for 24% of the applied 14C remaining 16 MAT, and was the predominant 14C-compound below 10 cm through 16 MAT. Hydroxyatrazine (HA) was the major degradation product in the top 10 cm of soil comprising 13% of 14C present I MAT and increasing to 24% by 12 MAT. Predominant degradation products at depths greater than 10 cm were HA and deethylatrazine (DEA). Deisopropylatrazine (DIA) accounted for less than 6% of the radioactivity recovered at any soil depth. Deethyldeisopropylatrazine (DEDIA) was detected in soil extracts 2 MAT indicating further degradation of DIA and DEA. The proportion of DEA and DIA increased while the proportion of HA decreased at increasing soil depths indicating that DEA and DIA...

A Natural Gradient Transport Study of Selected Herbicides

AbstractThe behavior of trace quantities of commonly detected herbicides and herbicide degradates was investigated in a shallow sand and gravel aquifer. In 1991, a solute pulse containing approximately 15 mg L−1 bromide, 3 μg L−1 atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), 2 μg L−1 alachlor (2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl)‐acetanilide), 10 μg L−1 cyanazine (2‐[[4‐chloro‐6‐(ethylamino)‐S‐triazin‐2‐yl]amino]‐2‐methylpropionitrile), and 10 μg L−1 metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide) was injected into a shallow aquifer near Fremont, NE. The plume was monitored for 2 mo following injection using an array of multilevel samplers. A second injection in 1992 included approximately 10 mg L−1 bromide, 1 μg L−1 butachlor (2‐chloro‐2′,6′‐diethyl‐N‐(butoxy methyl) acetanilide), and 3 μg L−1 atrazine, 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). This plume was monitored for 3 mo. Retardation factors (Rs) were determined for each herbicide by comparing concentration profiles to those of the conservative tracer; Rs were calculated as the ratio of first central moments. Results indicated only slight retention of all injected compounds. Retardation factors for atrazine, DEA, DIA, cyanazine, alachlor, and metolachlor were less than 1.3, with butachlor being slightly more retained (R = 1.65). Persistence of the injected compounds was estimated by the decrease with time in area under the breakthrough curves. Atrazine, DEA, DIA, cyanazine, and metolachlor showed no detectable loss. Losses of alachlor and butachlor were approximately 40 and 70%, respectively, in a 2‐mo period.

Formation and Movement of14C-Atrazine Degradation Products in a Clay Loam Soil in the Field

Formation of14C-atrazine degradation products and their distribution in the top 90 cm of soil was determined over 16 mo in a Webster clay loam in the field. After 16 mo, 64% of the applied14C could still be accounted for in the 90-cm soil profile. At 1 mo after treatment (MAT),14C moved to the 70- to 80-cm depth. Rapid movement of radioactivity could be attributed in part to preferential movement through vertical macropores. Atrazine accounted for 32% of the14C applied 16 MAT and was the predominant14C-compound in soil below 10 cm through 12 MAT. Hydroxyatrazine (HA) was the major degradation product in the top 10 cm of soil accounting for 9% of the14C present 1 MAT and increasing to 24% within 6 MAT. Deethylatrazine (BEA) was the predominant degradation product at depths greater than 10 cm, accounting for 26% of the14C in the 10- to 20-cm depth 16 MAT. Deisopropylatrazine (DIA) accounted for less than 10% of the14C recovered at any soil depth. Deethyldeisopropylatrazine (DEDIA) and an unidentified product were detected in soil extracts 1 MAT indicating further degradation past primary metabolites. The proportion of DEA and DIA increased while the proportion of HA decreased as soil depth increased indicating that DEA and DIA are more mobile in soil than HA. The large amount of radioactivity remaining in the soil 16 MAT suggests that a large pool of atrazine and its degradation products are present in the soil for a long period of time, having the potential to move deeper in the soil and ultimately contaminate ground water.

Influence of carbon and nitrogen application on the mineralization of atrazine and its metabolites in soil

AbstractIt has been proposed that levels of carbon and nitrogen in soil affect the rate at which triazine herbicides degrade. The present study was designed to investigate the effects of varying the levels of initial soil carbon and nitrogen as well as the effects of a later carbon addition on the mineralization of atrazine and its metabolites in soil. Atrazine degradation in soils amended with carbon as mannitol, and with nitrogen as urea, at levels of 10, 30, 50, or 80 mg kg−1 mannitol, urea, or mannitol and urea was similar to degradation in unamended soils. Only 39% of applied atrazine was mineralized after 326 days regardless of the initial carbon or nitrogen treatment. In contrast, a second mannitol amendment of 1 g kg−1 soil at day 140 increased [14C]carbon dioxide evolution by an additional 17% as a result of enhancing the mineralization rate of the atrazine metabolites. This conclusion is supported by our finding that periodic extraction of the soil with methanol followed by quantification on HPLC showed complete dissipation of the parent atrazine in 120 days. The metabolites hydroxyatrazine (HA), deisopropylatrazine (DIA), deethylatrazine (DEA), and diaminochlorotriazine (DACT) began to appear in the methanol extract 10 days following atrazine application. The greatest concentrations of HA, DEA, DIA. and DACT in the methanol extracts were 19, 12.4, 10.1, and 6.7% of applied atrazine, respectively. These concentrations were observed at day 95 except for DEA where the concentration continued to increase until day 142. A second soil extraction with hydrochloric acid (1m) + methanol (20 + 80 by volume) recovered additional HA, deethylhydroxyatrazine (DEHA), deisopropylhydroxyatrazine (DIHA), and DACT. When the extraction data were combined, 31.9, 12.4, 10.1. 10.2, 12.0 and 7.8% of applied atrazine was recovered as HA, DEA, DIA, DEHA. DIHA, and DACT, respectively. Combustion of the extracted soil showed 20% of the applied atrazine remained as soil‐bound residues after 326 days.

Determination of atrazine, deethylatrazine and deisopropylatrazine in water and sediment by isotope dilution gas chromatography—mass spectrometry

Methods for the trace analyses of atrazine, deethylatrazine (DEA), and deisopropylatrazine (DIA) in water and sediment have been developed by using stable-isotope dilution with gas chromatography-mass spectrometry detection. Water samples are spiked with known amounts of 13C 3-atrazine, 13C 3-DEA and 13C 3-DIA and submitted to solid-phase extraction with C 18 bonded silica. Pesticides are eluted from the solid phase with ethyl acetate. Sediment samples are spiked and equilibrated with a known amount of each labeled standard before supercritical fluid extraction (SFE) using a 4% (v/v) methanol-CO 2 mobile phase at 43°C and 10 MPa with off-line collection in methanol. A gas chromatograph coupled with a quadrupole mass spectrometer operated in the selected ion monitoring (SIM) mode was used to analyze the concentrated sample extracts. When compared to conventional liquid—liquid extraction methods, these methods decrease extraction time, labor, and solvent volume required. Quantification of the triazines by using isotope dilution compensates for differences in physical recovery for atrazine and its metabolites, especially when large ( > 100 ml) water volumes are extracted. Method detection limits for atrazine, DEA and DIA are 0.02, 0.02 and 0.10 μ g 1 −1, respectively, in water. In sediment, the method detection limits are 0.10, 0.20 and 0.50 ng g −1 for atrazine, DEA and DIA, respectively. More than 4000 water and 800 sediment samples have been analyzed by these methods for more than two years. The average accuracy (bias) for atrazine-fortified water samples is +6.4% ( n = 200) and the precision from duplicate analyses is ±6.0%. Precision of the SFE method for atrazine is ±11% at the 2 ng g −1 level whereas accuracy is −3.2% ( n = 8) for recovery of 13C 3-atrazine standard at the 5 ng g −1 level.