Abstract
The persistence and movement of methabenzthiazuron, metazachlor, trifluralin, iprodione, fenitrothion, fenvalerate and furathiocarb was studied in one growing season in cultivated clay, finesand and organic soils in southern Finland. Trifluralin was studied for two growing seasons. Methabenzthiazuron was the most mobile pesticide and metazachlor was almost as much mobile. They leached at least 15 cm in a month. Fenitrothion and fenvalerate were the most immobile. Trifluralin was the most and fenitrothion the least persistent. The concentrations of iprodione and fenvalerate in the top soils increased towards the autumn, presumably due to leaching of pesticides from plants. The residues of trifluralin measured in the surface layer of the mineral soils at the end of the growing season might have been harfmul to plants sensitive to trifluralin. The residues of trifluralin in the peat soil surface 1.5 years after the treatment were still high. Also methabenzthiazuron, iprodine and fenvalerate residues may in all probability have been detected in the following spring. If the half-life of a pesticide is over 80 - 100 days, it is likely that residues of it may be found in the spring following the application in cultivated Finnish soils.
Highlights
The evaluation of the fate of pesticides in Finnish environmental conditions using results obtained in foreign research work is difficult
For example Walker (1987 a) has calculated that if the half-life of a pesticide is 30 days in a laboratory study in 20 °C, its half-life estimated with a computer simulation model for the climatic conditions ofnorthern Europe would be 1 - 2 month in summer and 4-6 months in winter
He states that in practice pesticides have been less persistent in field conditions than estimates for their persistence based on laboratory results
Summary
The evaluation of the fate of pesticides in Finnish environmental conditions using results obtained in foreign research work is difficult. For example Walker (1987 a) has calculated that if the half-life of a pesticide is 30 days in a laboratory study in 20 °C, its half-life estimated with a computer simulation model for the climatic conditions ofnorthern Europe would be 1 - 2 month in summer and 4-6 months in winter. He states that in practice pesticides have been less persistent in field conditions than estimates for their persistence based on laboratory results. On the other hand, when the temperature was raised by ten degrees, the degradation rate increased by 3.7 - 4 fold
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