Soil Parameters Related with the Sorption of 2,4-D and Atrazine

Abstract

In order to explain the retention of 2,4-D and atrazine in fourteen soils from Madrid (central Spain) a series of soil physical and chemical characteristics has been analyzed. Simple and multiple regression models coincided in pointing out that soil abiotic characteristics (physical, mineralogical and cation exchange) comparatively had smaller influence in herbicide sorption than the organic matter. The multiple regression models for 2,4-D suggest that its retention in soil is significantly related with parameters such are the accumulation of particulate organic matter or the proportion of aromatic structures in the humic acids, indicating prevalence of π–π bonding interactions favored by the presence in soil of either humic acids with high maturity degree or altered lignins. In the case of atrazine, the sorption did not depend to large extent of the humus maturity (e.g., with a high optical density or a low C/N ratio of the humic acids), but of the total amount of organic matter and of a series of humic acid parameters suggesting low molecular weight (E465/E665) that would favor diffusion mechanisms required for the retention of this herbicide.