Transport and Fate of Atrazine in Midwestern Riparian Buffer Strips (original) (raw)
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Australian Journal of Soil Research, 2005
The degradation rate of atrazine in floodplain soils under natural grasslands and cropped fields in the Liverpool Plains, NSW, was studied under laboratory incubation and in glasshouse bioassays, and related to soil properties including microbial community analysis by t-RFLP. The experiments were part of a broader study aiming to manage pesticides in the environment using vegetative filters (biofilters). The soils differed in their atrazine treatment history. Degradation rate (half-life) in cropped soil was more rapid (≈2 to 7 days) than in 2 grassland soils (≈8 to ≈22 days). Bioassays in the glasshouse using oats and soybeans supported this finding. The t-RFLP analysis disclosed the presence of 2 consortia of bacterial species that are reported in the literature to degrade atrazine. These were: (i) Rhodococcus sp, Pseudomonas aeruginosa, and Clavibacter michiganense and (ii) Acinetobacter sp., Pseudomonas sp., and Streptomyces sp. Their dynamics during incubation suggested that they might have been responsible for the more rapid atrazine degradation in the cropped soil. The enhanced atrazine degradation in cropped soil was also associated with lower concentrations of soil organic C and percentage of light fraction carbon compared with grassland soils, suggesting that atrazine provided an additional source of N and C to organisms that can quickly degrade the herbicide. The finding of relatively short atrazine half-life has implications for the effectiveness of the herbicide, as well as for the loads of pesticide potentially entering the environment. The results suggest there is little risk of atrazine accumulating in biofilters and causing damage.
Effects of soil type and tillage practice on atrazine transport through intact soil cores
Geoderma, 2006
Agricultural systems of Argentina have increased herbicides inputs, mostly associated with adoption of no tillage (NT). Several studies have revealed presence of pesticides in groundwater. Therefore, research on the behaviour of herbicides in soils is driven by the need to manage and prevent possible contamination of groundwater. Soil organic carbon (OC) is the main soil component responsible of sorption, and consequently the main tool to reduce the leaching. However, in dynamic systems transport of organic chemicals depends on soil structural and hydraulic properties. Sorption controls the physical and biological availability of chemicals. Physical, heterogeneous flow domain, and chemical, kinetic reactions and molecular diffusion into aggregates, which are nonequilibrium processes that affect solute transport. The main objective of this paper was to evaluate the effects of soil texture and tillage system on atrazine transport through intact soil columns. The study focused on the identification of processes; and determination of parameters that control atrazine transport in the upper layer of soils. Balcarce (BAL, silty clay loam, fine, thermic, illitic, Typic Argiudoll)), Tres Arroyos (TAR, clay loam, fine, thermic, illitic, Typic Argiudoll) and Coronel Dorrego (DOR, loam, fine, thermic, mixed illitic-montmorillonitic, Typic Argiudoll) soils from the southeast of Buenos Aires Province (Argentina) were selected. The soils represent a wide range of OC content (BAL 35.5, TAR 28.8 and DOR 17.3 g kg − 1 ). At each site NT and conventional tillage (CT) systems were sampled. Four replicates of intact soils cores (15 × 8 cm) were removed from each combination of soil × tillage (BAL-NT, BAL-CT, TAR-NT, TAR-CT, DOR-NT, DOR-CT). Displacement studies were done using atrazine as the reactive solute and bromide as the nonreactive solute. Equilibrium and nonequilibrium transport models (CXTFIT 2.1) were employed to describe the breakthrough curves (BTCs). The software tool SMART was used to simulate atrazine transport under steady-state flow conditions. Atrazine BTCs were skewed to the right; exhibiting an asymmetric shape and tailing that implied nonequilibrium conditions during transport. Since physical nonequilibrium was assumed to be nearly negligible, the observed nonequilibrium was interpreted as a sorption-related process. The two-site nonequilibrium model showed an acceptable fit with the observed data (72 b R 2 b 86). Recovery percentages of atrazine in effluents were: BAL-CT 54.51%; BAL-NT 45.10%; TAR-CT 44.28%; TAR-NT 29.70%; DOR-CT 18.60%; DOR-NT 48.95%. The intraparticle diffusion model provided by SMART showed the best fit. In conclusion, intrinsic soil properties were more relevant for atrazine transport than those associated with tillage practices. However, no tillage produced early detection of atrazine in effluents, and favoured atrazine leaching in coarser soils with the lowest OC contents. However, the maximum loss of atrazine in the percolate took place in the soils with the highest OC level; with no effects of tillage practices. These soils had fine texture, and were well structured and aggregated. Intraparticle and intraorganic matter diffusion appear to be responsible for nonequilibrium sorption. Delayed sorption in aggregated soils leads to high concentration of atrazine available for leaching.
Journal of Environmental Quality, 2008
Soil bacteria have developed novel metabolic abilities resulting in enhanced atrazine degradation. Consequently, there is a need to evaluate the eff ects of enhanced degradation on parameters used to model atrazine fate and transport. Th e objectives of this study were (i) to screen Colorado (CO) and Mississippi (MS) atrazine-adapted and non-adapted soil for genes that code for enzymes able to rapidly catabolize atrazine and (ii) to compare atrazine persistence, Q 10 , β, and metabolite profi les between adapted and non-adapted soils. Th e atzABC and/or trzN genes were detected only in adapted soil. Atrazine's average half-life in adapted soil was 10-fold lower than that of the non-adapted soil and 18-fold lower than the USEPA estimate of 3 to 4 mo. Q 10 was greater in adapted soil. No diff erence in β was observed between soils. Th e accumulation and persistence of mono-Ndealkylated metabolites was lower in adapted soil; conversely, under suboptimal moisture levels in CO adapted soil, hydroxyatrazine concentrations exceeded 30% of the parent compounds' initial mass. Results indicate that (i) enhanced atrazine degradation and atzABC and/or trzN genes are likely widespread across the Western and Southern corn-growing regions of the USA; (ii) persistence of atrazine and its mono-N-dealkylated metabolites is signifi cantly reduced in adapted soil; (iii) hydroxyatrazine can be a major degradation product in adapted soil; and (iv) fate, transport, and risk assessment models that assume historic atrazine degradation pathways and persistence estimates will likely overpredict the compounds' transport potential in adapted soil.
Fate of atrazine in a soil under different agronomic management practices
Journal of Environmental Science and Health, Part B, 2014
Agricultural management affects the movement of atrazine in soil and leaching to groundwater. The objective of this study was to determine atrazine adsorption in a soil after 20 years of atrazine application under agronomic management practices differing in tillage practice (conventional and zero tillage), residue management (with and without residue retention) and crop rotation (wheatmaize rotation and maize monoculture). Atrazine sorption was determined using batch and column experiments. In the batch experiment, the highest distribution coefficient K d (1.1 L kg ¡1 ) at 0-10 cm soil depth was observed under zero tillage, crop rotation and residue retention (conservation agriculture). The key factor in adsorption was soil organic matter content and type. This was confirmed in the column experiment, in which the highest K d values were observed in treatments with residue retention, under either zero or conventional tillage (0.81 and 0.68 L kg ¡1 , respectively). Under zero tillage, the fact that there was no soil movement helped to increase the K d . The increased soil organic matter content with conservation agriculture may be more important than preferential flow due to higher pore connectivity in the same system. The soil's capacity to adsorb 2-hydroxyatrazine (HA), an important atrazine metabolite, was more important than its capacity to adsorb atrazine, and was similar under all four management practices (K d ranged from 30 to 40 L kg ¡1 ). The HA adsorption was attributed to the type and amount of clay in the soil, which is unaffected by agronomic management. Soils under conservation agriculture had higher atrazine retention potential than soils under conventional tillage, the system that predominates in the study area.
Fate of Atrazine in Sandy Soil Cropped with Sorghum
Journal of Environment Quality, 2001
ronmental circumstances (e.g., soil type, rainfall, irrigation, and application rate) can best be estimated by A field study was conducted to determine the fate of atrazine simultaneously considering all important processes and (6-chloro-N 2-ethyl-N 4-isopropyl-1,3,5-triazine-2,4-diamine) within the integrating them through a modeling approach (Waroot zone (0 to 90 cm) of a sandy soil cropped with sorghum [Sorghum bicolor (L.) Moench] in Gainesville, Florida. Atrazine was uniformly genet and Hutson, 1986; Wagenet and Rao, 1985; Gaber applied at a rate of 1.12 kg a.i. ha Ϫ1 to a sorghum crop under moderate et al., 1995). irrigation, optimum irrigation, and no irrigation (rainfed), 2 d after Reports of increases in levels of pesticides and other crop emergence. Bromide as a tracer for water movement was applied toxic organic pollutants in ground water have prompted to the soil as NaBr at a rate of 45 kg Br Ϫ ha Ϫ1 , 3 d before atrazine a number of laboratory and field experiments to underapplication. Soil water content, atrazine, and Br Ϫ concentrations were stand the processes and environmental factors that infludetermined as a function of time using soil samples taken from the ence pesticide behavior in soils (Cohen et al., 1984; Pye root zone. Atrazine sorption coefficients and degradation rates were et al., 1983; Rao et al., 1983). In a National Pesticide determined by depth for the entire root zone in the laboratory. Atra-Survey (NPS), atrazine was one of the most commonzine was strongly adsorbed within the upper 30 cm of soil and most ly detected pesticides in ground water throughout of the atrazine recovered from the soil during the growing season the United States (USEPA, 1990a; Wollenhaupt and was in that depth. The estimated half-life for atrazine was 32 d in topsoil to 83 d in subsoil. Atrazine concentration within the root zone Springman, 1990). The federal allowable maximum condecreased from 0.44 kg a.i. ha Ϫ1 2 days after application (DAA) to tamination level (MCL) for atrazine in U.S. drinking 0.1 kg a.i. ha Ϫ1 26 DAA. Negligible amounts of atrazine (≈5 g kg Ϫ1) water is 3 g L Ϫ1 (USEPA, 1976). were detected below the 60-cm soil depth by 64 DAA. Most of the Sorption and transformation are major processes afdecrease in atrazine concentration in the root zone over time was fecting the mass of solute available in solution for advecattributed to degradation. In contrast, all applied bromide had leached tive-dispersive transport through a soil profile. Many past the 60-cm soil depth during the same time interval. pesticides are nonpolar, and their adsorption on soils is predominantly due to the organic carbon (OC) content (Nkedi-Kizza et al., 1983), whereas pesticide degrada
Prediction of Atrazine Fate in Riparian Buffer Strips Soils Using the Root Zone Water Quality Model
Journal of Water and Environment Technology, 2005
The Root Zone Water Quality Model (RZWQM) was used to simulate the movement of atrazine after entry into switchgrass (Panicum virgatum L.) Riparian Buffer Strips (RBS). A multi-species RBS located along Bear Creek, Iowa, was used as the basis for model inputs and simulation. Atrazine entered the RBS at rates representing atrazine loss in runoff of 1, 3, and 5% of a 1.5-kg ha-1 application to an adjacent cornfield. Water equivalent to runoff depths of 0.125, 0.25 and 0.5-cm from the adjacent cornfield was added to the natural rainfall to allow the model to simulate surface water entering the RBS. RBS retained about 79-94% of atrazine in runoff from the adjacent cornfield. The RZWQM predicted very low atrazine concentrations in seepage (< 3-µg L-1). Atrazine loss in runoff leaving the RBS was most sensitive to macropore size and plant residue, but less sensitive to soil organic matter content. At macropore sizes larger than 0.01-cm there was no atrazine in runoff leaving the RBS. Plant residue mass was directly proportional to atrazine loss in runoff, but organic matter content was inversely proportional to atrazine loss in runoff. The RZWQM needed more improvement in pesticide leaching transport, and pesticide loss in runoff components.
Fate of Atrazine and Atrazine Degradates in Soils of Iowa
ACS Symposium Series, 1996
Several studies have been conducted to investigate the fate of atrazine (ATR, 2-chloro-4[ethylamino]-6[isopropylamino]-s-triazine) and major degradation products of ATR in soils of Iowa by using laboratory radiotracer studies, field lysimeters, and a field-scale approach. Complete metabolism studies of uniformly ring-labeled 14 C-chemicals revealed some major trends. Persistence of ATR, deethylatrazine (DEA, 2-chloro-4[amino]-6[isopropylamino]-s-triazine), and deisopropylatrazine (DIA, 2-chloro-4[ethylamino]-6[amino]-s-triazine) was greater in subsurface soils than in surface soils. In surface soil of Ames, DEA and didealkylatrazine (DDA, 2-chloro-4,6-[diamino]-s-triazine) were predominant degradates of ATR after 60 d, and hydroxyatrazine (HYA, 2-hydroxy-4[ethylamino]-6[isopropylamino]-s-triazine) was the predominant degradate of ATR after 180 d. The persistence of ATR, DEA, and DIA was significantly reduced under saturated soil moisture conditions than in soils held at a moisture near field capacity. Relative mobilities of ATR and degradates in five Iowa soils (surface and subsurface), determined by soil thin-layer chromatography, indicate that DEA is more mobile than ATR. The relative mobilities of DIA, DDA, and ATR were similar. Also, laboratory studies with undisturbed soil columns are supportive of greater mobility of DEA than ATR. In a field-scale study investigating the mobility of ATR and its degradates, it was indicated that ATR degradation products by themselves, or in combination with the parent compound can exceed the maximum contaminant level (MCL) of 3 μg/L currently set for ATR alone. In ATR-applied field plots, DEA and DIA were detected along with ATR in tile drain water samples, with concentrations of DEA exceeding DIA. In Extrazine®-(a herbicide mixture of 67% cyanazine [CYA; 2-chloro-4ethylamino-6-(1-cyano-1 methylethylamino)-s-triazine] and 21% ATR)applied field lysimeters, the concentrations of DIA exceeded those of DEA.
Journal of Agricultural and Food Chemistry, 2010
To assess the potential occurrence of accelerated herbicide degradation in soils, the mineralization and persistence of 14 C-labeled and non-labeled atrazine was evaluated over three months in two soils from Belgium (BS: atrazine treated 1973-2008; BC: non-treated) and two soils from Germany (CK: atrazine treated 1986-1989; CM: non-treated). Prior to the experiment, accelerated solvent extraction of bulk field soils revealed atrazine (8.3 and 15.2 µg kg −1 in BS and CK soil), and a number of metabolites directly after field sampling, even in BC and CM soils without previous atrazine treatment, by means of LC-MS/MS analyses. For atrazine degradation studies, all soils were incubated under different moisture conditions (50% maximum soil water holding capacity-WHC max-/slurried conditions). At the end of the incubation, the 14 C-atrazine mineralization was high in BS soil (81% and 83%), and also unexpectedly high in BC soil (40% and 81%), at 50% WHC max and slurried conditions, respectively. In CK soil, the 14 C-atrazine mineralization was higher (10% and 6%) than in CM soil (4.7% and 2.7%), but was not stimulated by slurried conditions. The results revealed that atrazine application history dramatically influences its degradation and mineralization. For the incubation period, the amount of extractable atrazine, composed of residues from freshly applied atrazine and residues from former field applications, remained significantly greater (statistical significance = 99.5% and 99.95%) for BS and CK soils, respectively, than the amount of extractable atrazine in the bulk field soils. This suggests that i) mostly freshly applied atrazine is accessible for a complex microbial community, ii) the applied atrazine is not completely mineralized and remains extractable even in adapted soils, and iii) the microbial atrazine-mineralizing capacity strongly depends on atrazine application history and appears to be conserved on long time scales after the last application.