Pollution at and below sites used for mixing and loading of pesticides

Sites used for mixing and loading of pesticides in sprayers and for washing tractors and sprayers may be point sources of pesticides. Pollution may be caused by accidental spills during filling, disposal of excess spray solution, rinsing of sprayer and tractor or from leaking nozzles on the sprayer. Ground water sampled 2-4 m below sites used for mixing and loading has been analysed for 23 or 46 different pesticides and metabolites in two Danish counties (Storstrøm and Bornholm). Further, the surface pollution at sites used for mixing, loading and rinsing was determined by elution with water of soil sampled in the top 10 cm. In all ground water samples pesticide pollution was determined to be above the European drinking water level (0.1 μg L ^-1). The highest concentrations and most pesticides were found below loading and mixing sites at machine pools, where the highest concentrations were the phenoxyacid herbicides dichlorprop (750 μg L ^-1) and 2,4-D (800 μg L ^-1). The herbicides bentazone, mecoprop and dinoseb were also found in relatively high concentrations (5-60 μg L ^-1). The surface soil sampled at the top 0-10 cm at sites used for loading and washing sprayers at six farms was eluted with water. These analyses also showed that many different pesticides and relatively high concentrations could be leached out from the soil. Twenty-four different pesticides and metabolites were found, and though most concentrations were below 10 μg L ^-1 about 10% of the water samples contained more than 50 μg L ^-1. The results demonstrate that sites used for mixing, loading and washing can be seriously contaminated with pesticides even in ground water 2-4 m below the sites. This implies that ground water, nearby wells and well borings are at risk of pollution and indicates the need for better farm practice.