Sorbed atrazine shifts into non-desorbable sites of soil organic matter during aging

• Published in: Water research (Oxford) 2004-11, Vol.38 (18), p.3881-3892
• Main Authors: Park, Jeong-Hun, Feng, Yucheng, Yong Cho, Sung, Voice, Thomas C., Boyd, Stephen A.
• Format: Article
• Language: English
• Subjects: Adsorption; Aluminum Silicates; Applied sciences; Atrazine; Atrazine - analysis; Atrazine - chemistry; Biological and physicochemical properties of pollutants. Interaction in the soil; Clay; Desorption; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Insecticides - analysis; Insecticides - chemistry; Kinetics; Models, Theoretical; Pollution; Pollution, environment geology; Soil; Soil and sediments pollution; Soil Pollutants - analysis; Sorption; Temperature; Time Factors
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2004.06.026

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 2days to 8months. Atrazine sorption isotherms were nearly linear (r2>0.97) and sorption coefficients were strongly correlated to soil organic carbon content. Sorption distribution coefficients (Kd) 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 (feq) decreased and the non-desorbable site fraction (fnd) increased as a function of aging time in all soils. For K-montmorillonite, fnd≈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.