Evaluating pesticide fate and transport: I. The use of lysimeter, field, and groundwater monitoring studies

Monolith lysimeters are not required for pesticide registration nor are the y used routinely for evaluating the fate and transport of pesticides in the United States. Lysimeters may serve as a valuable link in the interpretati on of laboratory and field environmental fate data for pesticides. However, several factors need to be considered in this interpretation, including 1) spatial variability of soil and site properties; 2) soil hydrology; and 3) tracking of the pesticide. Lysimeter design can cause unpredictable experi mental artifacts in soil hydrology which may not represent actual field con ditions. Natural water flow pathways in the soil may be disrupted through b arrier effects of the lysimeter wall and disruption of the hydraulic gradie nt at the lower boundary of the lysimeter. Analysis of in-situ soil morphol ogical and physicochemical properties provides important information for in terpretation of lysimeter data. The link between field and lysimeter data c an be evaluated using spatial variability information of soil properties an d mass balance analysis. Spatial variability data can aid in designing the lysimeter at a scale appropriate to better represent natural field conditio ns.