Transport and dating of pesticide residues from a 40 year old point source

Many of the recent findings of pesticides in surface- and groundwater might derive from different point sources, e.g. leaching from sites used for fil ling and rinsing of sprayers, leaching from municipal landfills and small w aste disposal sites, where pesticide remnants have been disposed of. The pu rpose of the project was to identify a pesticide point source and to determ ine the leaching and transport paths of the pesticide residues. To elucidate the dispersion of pesticides from a point source, a machine po ol site used for filling and washing of sprayers during the period 1950 to 1981 was selected. High concentrations of dichlorprop, mecoprop, diuron, be ntazone, chloridazon, atrazine and hydroxyatrazine were found close to the site. The location is situated on a plain area with marine sandy sediments of 3 t o 3 meters thickness. Below this clayey and sandy quaternary sediments are present. The groundwater seems to be relatively old dated by CFC-analysis, indicating relatively little infiltration of water and thus limited transpo rt in the upper layers of groundwater near the point source. The distributi on of pesticides from the point source tends to be divided into two main di rections one towards north and a second towards south. The most significant transport seems to be related to mecoprop and dichlorprop, which were foun d both south and north of the source. The perspectives of this investigation seem to confirm that point sources m ay be a problem to,groundwater use for drinking water extraction. In Denmar k there is at present about 750 machine poets and 45 000 farmers have spray ers.