title: Anionic polyacrylamide effects on soil sorption and desorption of metolachlor, atrazine, 2,4-D, and picloram.
abstract: Polyacrylamide (PAM) treatment of irrigation water is a growing conservation technology in irrigated agriculture in recent years. There is a concern regarding the environmental impact of PAM after its application. The effects of anionic PAM on the sorption characteristics of four widely used herbicides (metolachlor, atrazine, 2,4-D, and picloram) on two natural soils were assessed in batch equilibrium experiments. Results showed that PAM treatment kinetically reduced the sorption rate of all herbicides, possibly due to the slower diffusion of herbicide molecules into interior sorption sites of soil particles that were covered and/or cemented together by PAM. The equilibrium sorption and desorption amounts of nonionic herbicides (metolachlor and atrazine) were essentially unaffected by anionic PAM, even under a high PAM application rate, while the sorption amounts of anionic herbicides (2,4-D and picloram) were slightly decreased and their desorption amounts increased little. The impact mechanisms of PAM were related to the molecular characteristics of PAM and herbicides. The negative effects of PAM on the sorption of anionic herbicides are possibly caused by the enhancement of electrostatic repulsion by presorbed anionic PAM and competition for sorption sites. However, steric hindrance of the large PAM molecule weakens its influence on herbicide sorption on interior sorption sites of soil particles, which probably leads to the small interference on herbicide sorption, even under high application rates.
authors.affiliation: Department of Environ Sci, Univ of California, Riverside 92521, USA.
authors.forename: Jianhang
authors.initials: J
authors.lastname: Lu
authors.forename: Laosheng
authors.initials: L
authors.lastname: Wu
authors.forename: John
authors.initials: J
authors.lastname: Letey
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Farmer
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry*; D000081:Acetamides / Q000737:chemistry*; D000180:Acrylic Resins / Q000737:chemistry*; D000838:Anions; D001280:Atrazine / Q000737:chemistry*; D004563:Electrochemistry; D005427:Flocculation; D006540:Herbicides / Q000737:chemistry*; D010846:Picloram / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis*; D000099166:Polyacrylamides
chemical_list: D015084:2,4-Dichlorophenoxyacetic Acid; D000081:Acetamides; D000180:Acrylic Resins; D000838:Anions; D001280:Atrazine; D006540:Herbicides; D010846:Picloram; D012989:Soil Pollutants; D000099166:Polyacrylamides; C051786:metolachlor