A review of herbicide leaching studies in Sweden:: Field, lysimeter, and laboratory measurements

To characterize the mobility of pesticides in soil, results obtained in short-term laboratory tests are commonly used, along with data on degradation rates and physico/chemical properties of pesticides. However, the environmental conditions in such tests are quite different from natural field conditions in which biological, chemical, and physical processes occur in a complex soil structure, mostly under nonequilibrium conditions. Outdoor lysimeter experiments conducted under non-steady state flow conditions, are good alternatives to laboratory tests, which have demonstrated that they can simulate field situations quite well with respect to pesticide leaching. In this paper, results from a number of Swedish leaching studies with selected pesticides, carried out in monolith lysimeters, are described. Attention has been focused on comparing these leaching estimates with what one could expect in terms of mobility based on the inherent properties of the pesticides. Also, the impact of soil properties on pesticide leaching is discussed, as well as the importance of correctly evaluating the significance of measured concentrations and loads of pesticides obtained in lysimeter experiments in terms of actual field situations.