Quantifying interactions between compound properties and macropore flow effects on pesticide leaching

The dual-porosity MACRO model was used to examine interactions between compound properties and macropore flow effects on pesticide leaching. The model simulated leaching of 60 hypothetical compounds with differing degradation and sorption characteristics, based on a pre-calibrated scenario from southwestern Sweden. Under worst case conditions, macropore flow increases leaching in the structured clay soil by more than four orders of magnitude for moderately to strongly sorbed chemicals with relatively short half-lives. Leaching of some very mobile compounds was reduced by macropore flow. The impact of pesticide properties on leaching is substantially reduced for chemicals leaching in the 0.0001-10% range of the applied dose.