Alachlor Dissipation in Shallow Cropland Soil

Weed, D. A. J.; Kanwar, Rameshwar S.; Cambardella, Cynthia A.

doi:10.2134/jeq1998.00472425002700040007x

Cited by 16 publications

(12 citation statements)

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“…The predicted half-lives for the soils are in the upper range of estimated values from field experiments on surface soils (Aga and Thurman, 2001;Weed et al, 1998.). The alachlor may have been more persistent in these soils because they were saturated.…”

Section: Kinetics Of Alachlor Degradationmentioning

confidence: 76%

Persistence of Atrazine and Alachlor in Ground Water Aquifers and Soil

Schwab

Splichal

Banks

2006

Water Air Soil Pollut

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Degradation of atrazine and alachlor in saturated aquifer materials and soil was studied in the laboratory. A static aquifer was represented by a set of stagnant flasks and a well-mixed aquifer was simulated by recirculating columns. Water was tested at selected time intervals over six months and analyzed for herbicides and metabolites. Under all conditions, atrazine was more persistent than alachlor. Increased temperature had little effect on atrazine dissipation but did increase alachlor degradation rates, especially in the sterilized treatments. The addition of carbon and nitrogen prolonged the initial period before the onset of degradation in some of the columns. Enhanced mass transfer of the herbicides, nutrients, and oxygen in the recirculating columns dramatically increased dissipation of atrazine and alachlor. The degradation rates of atrazine and alachlor were 2 to 5 times faster in the recirculating columns than in the stagnant flasks. Atrazine was more persistent in the aquifer materials than in the soils, while alachlor dissipation was similar in the soils and recirculating aquifer columns, but was slower in the stagnant flasks. The prolonged persistence of atrazine under static, aquifer conditions (t 1/2 = 206 to 710 days) indicates that natural mechanisms are not sufficient to alleviate the risk of atrazine buildup over time; however, in a well mixed aquifer, atrazine degradation rates should be higher (t 1/2 = 66 to 106 days) and the threat of atrazine accumulation is diminished. Alachlor persistence at low concentrations (<10 μg L −1 ) in aquifers should not pose a long-term threat to ground water supplies.

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Section: Kinetics Of Alachlor Degradationmentioning

confidence: 76%

Persistence of Atrazine and Alachlor in Ground Water Aquifers and Soil

Schwab

Splichal

Banks

2006

Water Air Soil Pollut

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“…Alachlor and bentazone degradation usually fit a first‐order model (Weed et al, 1998; Thorstensen and Lode, 2001):

\begin{matrix} C = C_{0} exp true(- kt true) \end{matrix}

where C is the soil concentration of parent molecule at time t (d), C 0 is the concentration at time 0, and k is the rate constant (d −1 ).…”

Section: Resultsmentioning

confidence: 99%

Alachlor and Bentazone Losses from Subsurface Drainage of Two Soils

Dousset

Babut²,

Andreux

et al. 2004

J of Env Quality

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Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) is frequently detected at high concentrations in ground water. Bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] plus alachlor (2-chloro-2',6'-diethyl-N-methoxymethylacetanilide) is a potential herbicide combination used as a substitute for atrazine. Thus, the objective of this study was to assess the environmental risk of this blend. Drainage water contamination by bentazone and alachlor was assessed in silty clay (Vertic Eutrochrept) and silt loam (Aquic Hapludalf) soils under the same management and climatic conditions. Drainage volumes and concentrations of alachlor and bentazone were monitored after application. Herbicides first arrived at the drains after less than 1 cm of net drainage. This is consistent with preferential flow and suggests that about 3% of the pore volume was active in rapid transport. During the monitoring periods, bentazone losses were higher (0.11-2.40% of the applied amount) than alachlor losses (0.00-0.28%) in the drains of the silty clay and silt loam. The rank order of herbicide mass losses corresponded with the rank order of herbicide adsorption coefficients. More herbicide residues were detected in drainage from the silty clay, probably due to preferential flow and more intensive drainage in this soil than the silt loam. Surprisingly, herbicide losses were higher in the drains of both soils in the drier of the two study years. This could be explained by the time intervals between the treatments and first drainage events, which were longer in the wetter year. Results suggest that the drainage phases occurred by preferential flow in the spring-summer period, with correspondingly fast leaching of herbicides, and by matrix flow during the fall-winter period, with slower herbicide migration.

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“…The pore volume of the soil used was 57.5 mL. The percentage of herbicide eluted after the CF application was 39.4% (Figure 2b), which was less than what would be expected in a sandy soil with a low content of clay and organic matter, because alachlor adsorption is strongly correlated with both soil properties (13)(14)(15). Similar results were obtained by Johnson and Pepperman (19), who found that the herbicide amount leached from commercial and technical alachlor was approximately 33% in sandy soil columns.…”

Section: Alachlor Encapsulation In Ethylcellulose Microspheresmentioning

confidence: 89%

Ethylcellulose Formulations for Controlled Release of the Herbicide Alachlor in a Sandy Soil

Sopeña

Cabrera

Maqueda

et al. 2007

J. Agric. Food Chem.

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The development of controlled-release formulations of alachlor to diminish its leaching in sandy soils, avoiding groundwater contamination and maintaining its efficacy, was studied. For this purpose, ethylcellulose (EC) microencapsulated formulations (MEFs) of alachlor were prepared under different conditions and applied to soil columns to study their mobility. The results show that in all cases the release into water of alachlor from MEFs was retarded when compared with commercial formulation. Total leaching losses in soil columns were reduced to 59% from 98%. The mobility of alachlor from EC microspheres into soil columns has been greatly diminished in comparison with its current commercial formulation (CF), above all with increasing EC/herbicide ratios. Distribution of alachlor applied as MEFs at different depths in the soil was higher in the soil surface (66.3-81.3% of herbicide applied at the first 12 cm). In contrast, the residues from CF along the complete soil column were only 20.4%. From the results of bioassays, MEFs showed a higher efficacy than CF at 30 days after the treatment. The use of ME formulations could provide an advantage in minimizing the risk of groundwater contamination by alachlor and reducing the application rates, as a result of maintaining the desired concentration of the herbicide in the top soil layer, obtaining longer periods of weed control.

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Alachlor Dissipation in Shallow Cropland Soil

Cited by 16 publications

References 0 publications

Persistence of Atrazine and Alachlor in Ground Water Aquifers and Soil

Persistence of Atrazine and Alachlor in Ground Water Aquifers and Soil

Alachlor and Bentazone Losses from Subsurface Drainage of Two Soils

Ethylcellulose Formulations for Controlled Release of the Herbicide Alachlor in a Sandy Soil

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