Sorption and Movement of Alachlor in Soil Modified by Carbon‐Rich Wastes

Abstract

Abstract Laboratory studies were conducted to determine the effects of waste‐activated carbon (WAC), digested municipal sewage sludge (DMS), and animal manure (AM) on the sorption and leaching of alachlor [2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl)acetanilide] in a Plainfield sandy soil (Typic Udipsamment). A total of 7500 mL of simulated rain water was applied to soil columns under three flow regimes with or without the waste amendments. The WAC most effectively reduced the mobility of alachlor, DMS was superior to AM. Amounts of alachlor recovered in the leachates, which ranged from <0.1% (2.1 t C ha −1 of WAC amended soil) to 74% (unamended soil) of that applied, depended upon the C loading rate of the wastes and upon the source of C‐containing species. The dissipation of alachlor from soil was greater when soil was amended with DMS and AM than when amended with WAC. Sorption of alachlor, which was determined by batch equilibration, was generally inversely related to its leaching in the amended soil, this observation suggested that sorption by soil organic matter controlled the mobility of alachlor. Application of C‐rich wastes to sandy coarse‐textured soils may be useful for reducing pesticide leaching to groundwater.