Clopyralid dissipation in the soil contaminated with heavy metals

The aim of the studies was to determine the influence of copper and zinc contamination on clopyralid dissipation in soil. The experiment was carried out in laboratory conditions (plant growth chamber). Clopyralid was applied to three different soils [similar textures, pH, organic carbon content and contrasting copper and zinc content: soil natural contaminated with Cu and Zn (S1), soil with natural low Cu and Zn concentration (S2) and soil S21 prepared in the laboratory (S2 soil additionally contaminated with Cu and Zn salts in the amounts equivalent to contamination level of S1 soil)]. Soil samples were taken for analyses for 1 hour (initial concentration) and 2, 4, 8, 16, 32, 64 and 96 days after treatment. Clopyralid residue was analysed using GC/ECD (gas chromatography with electron capture detector). Good linearity was found between logarithmic concentration of clopyralid residues and time. The differences in Cu and Zn content influenced the clopyralid decay in soil. The values of DT50 obtained in the experiment ranged from 21 to 27 days. A high concentration of Cu and Zn in soil slowed down clopyralid degradation (the DT50 value was higher – 25–27 days).