Toxicology Of The Four Pollutants On Daphnia Magna

In this paper, Daphnia magna was a test organism, and a series of toxicity test were established. This thesis aims to evaluate acute, chronic and joint toxicity of monocrotophos, bifenthrin, SDBS, metolachlor and S-metolachlor to Daphnia magna, and also provides the evaluation standard for environmental organisms. The results obtained are as follows:1. The culture condition and test methods suit to our laboratory were established by repetitious test: D. magna were cultured in OECD M4 culture medium, and fed daily with the alga Senedusmus obliquus. Test animals were offspring more than three generations. The sensitivity of daphnids was accorded with the ISO standard.2. Monocrotophos 24h-EC50 and 48h-LC50 values for D. magna in the experimental conditions were 0.161 (0.157-0.161) mg/L and 0.394 (0.236-0.640) mg/L respectively. It was high toxicant on the basis of classification standard of toxicity. The data from chronic test indicated that LOEC is 10ug/L, and NOEC is 5ug/L. The chronic test is far more sensitive than acute test. It was independent joint action between monocrotophos and SDBS.3. Bifenthrin 24h-EC50, 48h-LC50 and 96h-LC50 values for D. magna in the experimental conditions were 3.24 (2.85-3.68) ug/L, 12.40 (11.87-12.95) ug/L and 1.40 (0.94-2.07) (ig/L respectively. It was high toxicant on the basis of classification standard of toxicity. LOEC of bifentrhrin is 0.02ug/L, and NOEC is 0.004ug/L. The order of sensitivity of all parameters was as follows: number of young per female>length>days to first brood=number of broods per female=intrinsic rate of natural increase (r)>longevity. It was independent joint action between bifenthrin and SDBS, and the same as bifenthrin and monocrotophos. In the recovery test, reproduction such as number of young per female as well as length were still reduced in F1 (1st) generation daphnids from parentals (F0) exposed to the bifenthrin. However F1 (3rd) individuals from parentals exposed to pesticide concentrations were able to restore reproduction when a recovery period of 21 days was allowed, but the length ofF1 (3rd) from parentals exposed to the 0.5 and 0.75ug/L bifenthrin concentration was still significantly effected (P<0.05).4. The 24h-LC50 of rac-metolachlor and S-metolachlor were 69.4 (64.2, 75.1) mg/L and 51.2 (48.2, 54.5) mg/L, respectively. It was low toxicant on the basis of classification standard of toxicity. The results showed that the LOEC of rac-metolachlor was 0.01 mg/L, and NOEC was 0.001 mg/L; LOEC and NOEC of S-metolachlor were 0.5 mg/L and 0.1 mg/L respectively. Parameters such as length, longevity and number of broods per female were significantly (P<0.05) affected at metolachlor concentrations higher than 0.5 mg/L, but these parameters were not significantly affected until at S-metolachlor concentrations above 5mg/L except that the length parameter was effected at the same concentrations of metolachlor. Number of young per female was significantly reduced at metolachlor concentrations above 0.001 mg/L, and this parameter was significantly reduced at S-metolachlor concentrations above 0.1 mg/L. Through the significance analysis, it can be concluded that metolachlor was significantly (P<0.05) more toxic to D.magna than S-metolachlor from the longevity, number of broods per female, number of young per female and length test.