title: Sorbed atrazine shifts into non-desorbable sites of soil organic matter during aging.
abstract: Soil-chemical contact time (aging) is an important determinant of the sorption and desorption characteristics of the organic contaminants and pesticides in the environment. The effects of aging on mechanism-specific sorption and desorption of atrazine were studied in soil and clay slurries. Sorption isotherm and desorption kinetic experiments were performed, and soil-water distribution coefficients and desorption rate parameters were evaluated using linear and non-linear sorption equations and a three-site desorption model, respectively. Aging time for sorption of atrazine in sterilized soil and clay slurries ranged from 2 days to 8 months. Atrazine sorption isotherms were nearly linear (r(2)>0.97) and sorption coefficients were strongly correlated to soil organic carbon content. Sorption distribution coefficients (K(d)) increased with increase in age in all five soils studied, but not for K-montmorillonite. Sorption non-linearity did not increase with increase in age except for the Houghton muck soil. Desorption profiles were well described by the three-site desorption model. The equilibrium site fraction (f(eq)) decreased and the non-desorbable site fraction (f(nd)) increased as a function of aging time in all soils. For K-montmorillonite, f(nd) approximately 0 regardless of aging, showing that aging phenomena are sorbent/mechanism specific. In all soils, it was found that when normalized to soil organic matter content, the concentration of atrazine in desorbable sites was relatively constant, whereas that in non-desorbable site increased. This, and the lack of aging effects on desorption from montmorillonite, suggests that sorption into non-desorbable sites of soil organic matter is primary source of increased atrazine sorption in soils during aging.
authors.affiliation: Department of Environmental Engineering, Chonnam National University, Kwang-Ju 500-757, South Korea.
authors.forename: Jeong-Hun
authors.initials: JH
authors.lastname: Park
authors.forename: Yucheng
authors.initials: Y
authors.lastname: Feng
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Cho
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Voice
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Boyd
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates; D001280:Atrazine / Q000032:analysis* / Q000737:chemistry; D000077215:Clay; D007306:Insecticides / Q000032:analysis* / Q000737:chemistry; D007700:Kinetics; D008962:Models, Theoretical; D012989:Soil Pollutants / Q000032:analysis*; D013696:Temperature; D013997:Time Factors
chemical_list: D000538:Aluminum Silicates; D007306:Insecticides; D012989:Soil Pollutants; D001280:Atrazine; D000077215:Clay