Role of the chemistry of soil organic matter on the sorption of diuron

Abstract

The influence of organic matter chemistry on the sorption of diuron to soils collected from a small (2 ha) field was investigated. Organic carbon-normalized sorption coefficients (KOC), determined by batch sorption, varied between 405 and 598 Lkg- amongst 10 A11 horizons, and between 547 and 975 Lkg- amongst 10 matching A12 horizons. In all cases KOC was greater for the A12 horizon than the corresponding A11 horizon by 27-81. Organic matter chemistry of the A11 and A12 horizons was determined using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. KOC was positively correlated with aryl C (r 0.61, significance level 0.001) and negatively correlated with O-alkyl C (r 0.88, significance level 0.001) as a single factor and as a combination of both we also propose A index (r 0.65, significance level 0.001). Little change in soil mineralogy across a very small field led to diminished organic matter and clay mineral interactions, allowing the effect of organic matter chemistry on KOC to be clearly seen. © 2008 WIT Press.