Introduction

At the CML a pilot study has been conducted on the possibilities of presenting the surface water concentrations of pesticides in the Netherlands graphically in the form of an atlas. Up to the present this has hardly been done with pesticide data. Such an atlas could be used for different purposes. It gives information about where a pesticide is being measured, observed and eventually poses a problem. This may be related to pesticide - and land use. Finally, one can judge the quality of the current monitoring system. This study was conducted under commission of the RIZA (Institute for Inland Water Management and Waste Water Treatment).

As an example, six pesticides

For the pilot study, measurements from the CIW (Commission of Integral Water management) of 1997 and 1998 were used. As an example maps were made for six pesticides:

• Atrazin
• Carbendazim
• Iprodion
• Metribuzin
• Propoxur
• Vinchlozolin

Carbendazim, iprodion and vinchlozolin are fungicides, atrazin and metribuzin herbicides and propoxur an insecticide.
In presenting the data, the Netherlands were divided in 5x5 km2 squares.

Types of maps

In each square, from which data were available, the pesticide concentration was presented relative to a certain standard. In the Netherlands there are three standards for pesticides in surface-water.

• the standard for drinking-water (0.1 microgram per liter), which resulted in chemical maps;
• the maximum allowable risk level (MTR) (this standard varies per pesticide), which resulted in eco-toxicological maps;
• the standard set by the Board on the Admission of Pesticides (CTGB) (this standard varies per pesticide).

Also, it was tried to make a connection with pesticide- and land use in the Netherlands.

Map example

As an example a map of atrazin is shown, where the concentrations are presented in relation to the standard for drinking-water. Beside has been represented a map with the companies with silage maize (source: de Landbouwtelling 1997, CBS). Atrazin is almost exclusively being used for the cultivation of maize.

According to the map, the largest exceedings of the standard for drinking-water are observed in the east of the Netherlands (Province Gelderland) and in the south (Province of Limburg). These are areas where a lot of maize is being cultivated. The low number of measurements in the province of Noord-Brabant and the east of the province of Overijssel are remarkable, as also here a lot of maize is being cultivated. In contrast, a lot of measurements are conducted in the provinces of Groningen, Friesland, Noord- and Zuid-Holland where there is relatively little cultivation of maize.

Conclusions

From the results of the pilot study it is concluded that it is feasible to show per separate pesticide the surface water concentrations in a spatial fashion. One gets a good spatial picture per pesticide and with most pesticides a connection is possible with pesticide- and land use. Furthermore, gaps are made apparent in the monitoring system.

The study resulted in relevant new insights. Exceedings of standards were observed in areas and times of the year where one, on basis of data on land- and pesticide use, does not expect them.