Toxicity of copper/dimethomorph combination for Lemna minor and depuration of the fungicides by aquatic plant.

Runoff-water of Champagne vineyards is often collected in decantation ponds where pesticides may be eliminated before the water is transferred to rivers. In order to accelerate this process, Lemna minor was tested for its phytoremediation capacity. In the ponds several pesticides coexist. Therefore, the cross-influence of copper and dimethomorph, two pesticides frequently used on grape to control fungal diseases, was studied on toxicity and their removal by L. minor. The toxicity of copper and dimethomorph alone and in combination, was assessed by growth inhibition of L. minor cultures after 96 h and 168 h. Copper had a severe impact on growth (maximum inhibition: 90% at 1000 microg/L) while dimethomorph (as pure ingredient DMM(P) or formulated as Forum DMM(F)) did not (inhibition < 45% at 1000 microg/L) after 168 h of treatment. When both chemicals were combined, a synergistic effect was detected after 96 h of exposure to copper and DMM(F). However, this interaction tended towards additivity after 168 h. Additivity was also observed when DMM(P) replaced DMM(F) in the mixture of copper and dimethomorph at 96h00 and 168h00. The removal of copper depended on DMM(F) concentration. For example, with 250 microg/L of dimethomorph as Forum, removal of copper increased from 36 to 41%. Depuration of DMM(F) by L. minor varied between 10 and 40% after 96 h. This depuration decreased in the presence of copper possibly due to the metal toxicity.

Effect of cadmium toxicity on survival and phototactic behaviour of Daphnia magna.

Change in the phototactic behaviour of a positively Daphnia magna clone C1 34 was used as indicator of toxic stress. The phototactic behaviour was quantified using an experimental set-up which was described in a previous study. In flow-through experiments, animals exposed to 0.03 mg l(-1) Cd++ exhibited a significant effect of cadmium on the phototactic behaviour within a period of 1 h, either with starved or fed animals by approximately 2x10(5) Scenedesmus acutus cell.ml(-1). The results suggest also that cadmium can be adsorbed for 3- h exposure and became desorbed after 4.5 h period. Continuous flow-through protocol was described for measuring survival of strain of D. magna, using juveniles that have been exposed to 1 mg l(-1) Cd++ for: 0.25; 0.5; 1; 2; 4 and 6 h. In these experiments a significant reduction in survival was demonstrated and the effect was shown to be significant within the first 30 min of the test. It was also found that the inhibition rate I(n) of survival can be estimated by a logarithmic expression as a function of time: I(n) (%) = 26.348 Ln 54.352 x t.