Atrazine and metribuzin sorption in soils of the Argentinean humid pampas

DANIEL, P. E, BEDMAR, F., COSTA, J. L. AND APARICIO V. C

ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY

Año: 2002 vol. 21 p. 2567 - 2572

0730-7268

Laboratory studies were conducted to determine the influence of surface and subsurface properties of three representative soils of the humid pampas of Argentina on atrazine and metribuzin sorption. Atrazine and metribuzin sorption isotherms were constructed for each soil at four depths. Sorption affinity of herbicides was approximated by the Freundlich constant (Kf), distribution coefficient (Kd), and the normalized Kd based on organic carbon content (Koc). Multiple regression of the sorption constants against selected soil properties indicated that organic carbon content (OC) and silt were related positively and negatively, respectively, to atrazine Kf coefficient (r2 5 0.93), while Kd coefficient of atrazine was related positively to organic carbon content and negatively to both silt and cation exchange capacity (CEC) (r2 5 0.96). For metribuzin, only organic matter content was related positively to Kf coefficient (r2 5 0.51). Lower Kf values for atrazine were obtained for all soils with increasing depth, indicating lesser sorption at greater depths. Metribuzin sorption was quite similar across all depths. Sorption constant Kf of atrazine ranged from 2.06 to 7.82, while metribuzin Kf values ranged from 1.8 to 3.52 and were lower than atrazine for all soils and depths, indicating a greater leaching potential across the soil profile.Kf), distribution coefficient (Kd), and the normalized Kd based on organic carbon content (Koc). Multiple regression of the sorption constants against selected soil properties indicated that organic carbon content (OC) and silt were related positively and negatively, respectively, to atrazine Kf coefficient (r2 5 0.93), while Kd coefficient of atrazine was related positively to organic carbon content and negatively to both silt and cation exchange capacity (CEC) (r2 5 0.96). For metribuzin, only organic matter content was related positively to Kf coefficient (r2 5 0.51). Lower Kf values for atrazine were obtained for all soils with increasing depth, indicating lesser sorption at greater depths. Metribuzin sorption was quite similar across all depths. Sorption constant Kf of atrazine ranged from 2.06 to 7.82, while metribuzin Kf values ranged from 1.8 to 3.52 and were lower than atrazine for all soils and depths, indicating a greater leaching potential across the soil profile.