Assessment of the genotoxicity of Cu and Zn in raw and anaerobically digested slurry with the Vicia faba micronucleus test

Genotoxicity of Cu and Zn was assessed by use of the micronucleus (MN) test on Vicia faba roots. Plants were exposed to various leachates of raw and anaerobically digested pig slurry, with maximum total concentrations of 200 μM Cu and 600 μM Zn. The results indicated stabilisation of the organic matter during anaerobic digestion of the slurry and bioconversion of some phytotoxic organic compounds (e.g. phenols or p-cresol), but did not show a relationship between Cu and Zn concentrations and MN frequency. Exposure of Vicia plants to binary inorganic solutions of Cu and Zn (CuSO4/ZnSO4, 1:3) showed a significant micronucleus induction at concentrations of 40 μM Cu and 120 μM Zn and higher. When MN frequency was plotted against dissolved Cu (<0.45 μm), applied as slurry or as CuSO4, a single curve was obtained. At concentrations lower than 10 μM, modulation of the genotoxic effect of Cu was found. At concentrations up to 150 μM, MN induction increased significantly, while phytotoxic symptoms appeared at higher concentrations.