CRITERIA FOR EVALUATING THE IMPACT OF PESTICIDES ON GROUNDWATER QUALITY

A lot of data and information are available regarding the presence of pesticides in ground-waters or their tendency to contaminate them. Despite this, for a very large number of pesticides these data and information are almost completely lacking. Many theoretical methods have been proposed to predict the leaching potential of pesticides. Persistence (expressed by DT50) and mobility (expressed by K(oc)) are key parameters that seem to be particularly representative of the overall leaching potential of nonionic compounds and they are widely used in these methods. Nevertheless, these parameters may vary greatly causing sharp differences in ranking the leaching potential of pesticides. Indeed, when the GUS Index is calculated using the available published values of K(oc) and DT50 in combinations representing the minimum, medium and maximum leaching potential of herbicides, very different results can be obtained. Many of these compounds can be classified as contaminants or non contaminants, depending on the type of combination used.