Pesticide extraction from soil into runoff under a rainfall simulator

Context Runoff estimation is an important aspect of pesticide environmental behaviour and the major loss pathway to environment. Aims To improve understanding runoff. Methods Data from three rainfall simulator studies was used. Twelve pesticides were studied ranged tightly sorbed (DDE, soil sorption coefficient (KD) ~15 000 L kg−1) weakly (dimethoate, KD < 30). Key results Event runoff concentrations closely related (0–25 mm depth). The ratio concentration (the extraction ratio, ERO), similar for with a wide range across soils: (μg L−1) = 28 × (mg kg−1). ERO decreased time after spraying, presumably due lower in top few soil. Conclusions This model provides improved or estimates than previous models. Similar values between sites probably hydrology (high intensity, surface sealing, moist subsoils) erosion, because same masses water are involved mixing. Reduction by leaching not influential, infiltration small too high. Implications Conditions apply during summer storms on most cotton grain land clay soils northern lands eastern Australia. should be applicable under these conditions.