Formation and Transport of the Sulfonic Acid Metabolites of Alachlor and Metolachlor in Soil

• Published in: Environmental science & technology Vol. 35; no. 12; pp. 2455 - 2460
• Main Authors: Aga, D. S, Thurman, E. M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.06.2001
• Subjects: Acetamides - analysis; Acetamides - metabolism; Acids; Agronomy. Soil science and plant productions; alachlor; Alkanesulfonates - chemistry; Applied sciences; Biological and medical sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental impact; Environmental Monitoring; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Herbicides; Herbicides - analysis; Herbicides - metabolism; Kinetics; Metabolites; metolachlor; Pollution; Pollution, environment geology; Soil and sediments pollution; Soil and water pollution; Soil Pollutants - analysis; Soil Pollutants - metabolism; Soil science; Soils; sulfonic acid; Biodegradation; Pollutant behavior; Metabolite; Pesticides; Partition coefficient; Runoff water; Soil pollution; Sulfonic acid; Herbicide; Transport process; Dechlorination; Silt loam soil; Organic amide; Phase partition; Degradation product
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es991264s

Alachlor and metolachlor are dechlorinated and transformed into their corresponding ethane sulfonic acid (ESA) metabolites in soil. In a field-disappearance study, it was shown that alachlor ESA was formed at a faster rate and at concentrations 2−4 times higher than metolachlor ESA, conforming with the observed longer disappearance half-life of metolachlor (15.5 d) in the field as compared to alachlor (8 d). Runoff data also showed higher concentrations of alachlor ESA as compared to metolachlor ESA, even though they were applied at the same levels. Data from soil cores showed transport of the ESA compounds in soil to as far down as 75−90 cm below the surface, at concentrations ranging from less than 0.5 μg/L to about 50 μg/L. In contrast, no parent herbicide was detected at these depths. This observation correlates with the higher log K oc values for alachlor (3.33) and metolachlor (3.01) relative to their corresponding ESA metabolites, alachlor ESA (2.26), and metolachlor ESA (2.29).