Adsorption, mobility and degradation of diphenamid in chinese soils

The present study was conducted to determine adsorption, mobility, and degradation characteristics of diphenamid in five Chinese soils and their relationships. The adsorption of diphenamid in soils tested could accurately be described by a Freundlich equation. Based on the mobility factor (Rf), diphenamid was seen to be slightly or moderately mobile in soils studied. Regression of Kf and Rf against selected soil properties indicated that Organic Matter (OM) was the most influential factor governing adsorption and mobility of diphenamid (r2 > 0.92) followed by clay (r2 > 0.61). There was a significant correlation (p < 0.01) between Kf and Rf of diphenamid. Diphenamid degradation data were fitted the first-order reaction equations, yielding half-lives (T1/2) ranging from 187.3 to 247.5 days in unsterilized soils but prolonging to 577.5–630.0 days in sterilized soils. The prolonged T1/2 by sterilization showed that microbial degradation was the dominant pathway for diphenamid degradation in soils. Degradation of diphenamid in soils appeared to be influenced by soil OM (r2 > 0.97) and clay content (r2 > 0.85). The T1/2 of diphenamid was significantly related to both Kf and Rf (p < 0.05), indicating that either Kf or Rf might be used as a model for predicting degradation of diphenamid in soils involved.