Pesticider i punktkilder

English Summary

The report describes recent findings of pesticides in surface- and groundwater, and points out, that the pollution might come from different sources. Thus leaching from sites used for filling and rinsing of sprayers, leaching from municipal landfills and small waste disposal sites, where pesticide remnants have been disposed of as well as general spraying with pesticides may be sources of ground water pollution. The purpose of the project is to elucidate the previous ways of disposal of pesticides and to identify a pesticide point source and determine spreading from this point source.

Previous ways of disposal of pesticides was elucidated by a questionnaire to 5 groups of farmers and 2 groups of fruit-growers, after their participation in a talk about fate of pesticides in the environment. 276 questionnaires were distributed and 185 were filled in.

Most important pesticide remnants came from "small residues in cans, cleaning in pesticide stocks, residues after change in ownership of real estate and changed crop growth". Disposal of pesticides has previously been done by both burying, deposition in marl pits and on waste disposal sites. Most of the participants had only disposed of empty cans and bags, but about 25% had disposed of 1 to 10 kg of pesticides. Some would still be able to find the disposal sites. A questionnaire to 26 agricultural advisors supported the information above. Thus the questionnaire supported that there is a need to acknowledge disposal of pesticide residues, and that previously this disposal of pesticides have been done by burying or by delivery at waste dump sites, though the data is not sufficient to give statistical safe description of the problem. It is estimated, that in Denmark about 750 machine pools and 45 000 farmers had sprayers in 1998.

To elucidate the spreading of pesticides from a point source, a site used for filling and washing of sprayers at a machine pool operating from 1950 to 1981 was used. The pesticide point source below the filling site is situated on a plain area with marine sediments and 3 to 4 meters below surface sediments from the Quaternary period. Direction of water flow is NW in deep groundwater layers but direction of ground water flow is more complicated near the soil surface. The near surface ground water seems to be relatively old dated by CFC-analysis, showing relatively little transport of young water and thus showing limited transport in the upper layers of ground water near the point source.

High concentrations of dichloroprop, mecoprop, diuron, bentazon, chloridazone, atrazine and hydroxyatrazine were found in the point source. The distribution of pesticides from the source tends to go both towards north and south, up to 60 meters from the source, towards the two creeks that drain the area. Largest transport was found for mecoprop and dichloroprop. Also chloridazone and bentazone, which seems to come from the point source were found in wells south of the point source. Phenoxyherbicides were also found in a sampling well about 145 meters south of the source, which may come from the point source.