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| Book/Report | FZJ-2018-02652 |
1986
Kernforschungsanlage Jülich, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/18284
Report No.: Juel-2055
Abstract: Studies with 14c-labelled pesicides have been predominantly conducted under laboratory conditions usinq microecosystems or standardized set-ups. The data thus obtained are generally limited to the evaluation of individual processes. In the Jülich Nuclear Research Centre, however, during the last 15 years the fate of about 30 different 14C-labelled pesticides has been studied in lysimeter set-ups under outdoor conditions. In order to validate data on residue situation and pesticide translocation in soil obtained in these lysimeter studies, in comparison to field experiments with GoltixR and TribunilR applied at rates of 5 and 10 or 2 and 4 kg/ha, respectively, [3-14C]metamitron and [carbonyl-14C]methabenzthiazuron have been spra ed in a preemergence treatment onto sugar beets and at the 3-4 leaf stage onto winter wheat growing in lysimeters. In addition 2 types of lysimeter were also compared: 1 m$^{2}$4surfce area with 40-50 cm of packed to soil (Ap-horizon) and 0.5 m$^{2}$ surface area with 80 or 110 cm undisturbed soil profile of a degraded loess soil ("Parabraunerde") representing one of the mos fertile soils in Germany, predominantly in agricultural use. All the requirements of soil cultivation, fertilization and additional plant protection treatments were conducted in full agreement with the field experiment. The soil temperatures, recorded continuously in 10 and 30 cm soil depth, aid not show any si nificant difference and the moisture regime only partly deviate during the vegetation of the sugar beets. In addition the behaviour of the 2 14C-labelled pesticides was also tested in standardized plant containers for pot experiments system Kick-Brauckmann containing 8 kg soil under outdoor conditions and various small scale laboratory experiments including the test systems which are proposed from the Federal Biological Institute to test degradation and leaching of pesticides in soil. 50 days,after the Goltix application, about 4% of the applied active ingredient could be extracted and determined by gas-chromatography as metamitron or its major metabolite desamino-metamitron in the field soil, whereas about 8% was found in the lysimeter soil. At later stages no metamitron residues could be detected. However, 14(c-determination showed that about 50% of the applied radioactivity remained in the soil at the sugar beet harvest, 160 days after spraying. Half of it beeing concentrated in the upper 5 cm of the soil wile less than 1% was translocated below a depth of 20 cm. In the case of Methabenzthiazuron the residues determined in the field soil amounted to about 40% as com_pared to 33% found in the lysimeter soil at the wheat harvest, r33 days after spraying. The radioactivity in the lysimeter soil represented a total of about 60% of the applied carbonyl-14C. About 53% was concentra- ted in the upper 5 cm soil layer and only 3 and 2% were found in the 5-10 and 10-20 cm soil layer, respectively. In both lysimeterexperiments the leachate contained generally less than 0.1% of the applied radioactivity but neither metamitron nor methabenzthiazuron nor structurally related metabolites could be identified. The major findings of this comprehensive study illustrate that the residue situation, as well as the rates or pesticide and/or metabolite translocation in the soil, were not significantly different in the two lysimeter systems thus demonstrating that this type of lysimeter studies can simulate the real field situation. All other test systems only partly succeeded in simulating degradation and leaching behaviour of the two active ingredients. From field conditions differing moisture regimes, temperatures and plant/soil relations led to pesticide residues which were up to 6 times higher or lower as detected under natural conditions.
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