Pesticide concentrations in air and precipitation in the Netherlands

Atmospheric deposition may be an important source of persistent organic compounds (POP) and pesticides for the Dutch coastal and inland waters. Current estimates of the atmospheric input have been made using atmospheric dispersion models. The uncertainty is however large. A project was defined with the aim to assess the input on the basis of measurements. For a period of two years (1999-2001) a monitoring network was operated. At eighteen stations, located across the whole country, air and precipitation samples were taken on a weekly and monthly basis. In these samples the concentrations of pesticides, PCB's and PAH's were determined. Up to 50 different pesticides were observed in precipitation and air. The concentration of 17 of these in precipitation exceeded the maximum permissible level for surface water and 22 exceeded the standard for drinking water of 100 ng l(-1). The input from the atmosphere to Dutch inland waters appeared to be as large as the input of pesticides by other sources such as spray drift. Model calculations were also carried out to identify the sources of these compounds. The occurrence of atrazine could be related to emissions outside the Netherlands.