Simultaneous effects of two fungicides (copper and dimethomorph) on their phytoremediation using Lemna minor

Effects of two fungicides, copper and dimethomorph ((E,Z)4-[3-(4-chlorophenyl)-3-(3-4dimethoxyphenyl) acryloyl] morpholine) on Lemna minor growth and phytoremediation were evaluated. The toxicity of copper and dimethomorph alone and in combination, was assessed by growth inhibition of L. minor cultures after 96 and 168 h. Copper had a severe impact on growth (max. inhibition: 90 % at 1,000 μg L(-1)) while dimethomorph (as pure ingredient or formulated as Forum) did not (inhibition <45 % at 1,000 μg L(-1)) after 168 h of treatment. When both chemicals were combined, synergism was observed after 96 h of exposure to copper and Forum. However, this interaction was a simple additivity after 168 h. Additivity was also observed when the pure active ingredient (dimethomorph) replaced Forum in the mixture of copper and dimethomorph at 96 and 168 h. L. minor showed an excellent performance in removing copper from the medium since after 96 h, 36, 60, and 76 % removal were reached for 10, 20, and 30 μg L(-1) of Cu respectively. Copper accumulated in the plants. The removal of copper increased with Forum concentration. After 96 h copper (10 μg L(-1) initial concentration) elimination increased from 36.39 ± 5.86-60.70 ± 6.06 % when Forum concentration increased from 0 to 500 μg L(-1). Accumulation of copper in plants was also increased by Forum but not by the active ingredient alone. Depuration of Forum by L. minor varied between 10 and 40 % after 96 h and it was generally more efficient than that of the pure ingredient. This depuration decreased in the presence of copper possibly due to the metal toxicity.