The Toxicity And Bio-concentration Of Three Pesticides To Benthic Animals Molluscs

After application of pesticides to fermland, especially paddy fields, pesticides migrate to water bodies with water and soil through leakage of field water, artificial drainage and surface runoffs after rains, thus causing pollutions to water bodies. The pollution can endanger the survival of aquatic organisms, in severe cases can cause death to aquatic organisms by acute toxicosis. The survivals from pesticide pollutions can absorb and accumulate pesticides in body and harm human health through the food chain. Control of using pesticides in fermland is of much significance to prevent pesticide pollutions to aquatic organisms.Acute toxicity of three pesticides (chlorpyrifos, butachlor and triadimefon) to benthic animals molluscs was studied, and also sensitivities of river snails and clams in different sizes to pesticides were measured. Results showed that the96h-LCso of chlorpyrifos to Bellamya aeruginosa and Cipangopaludina cathayensis were4.316mg/L and6.314mg/L, the168h-LC50of chlorpyrifos to Corbicula fluminea, Anodonta woodiana, Lanceolaria gladiola were5.578mg/L.6.518mg/L and8.897mg/L, respectively; the96h-LC50of butachlor to Bellamya aeruginosa and Cipangopaludina cathayensis were3.616mg/L and4.312mg/L. the168h-LCso of chlorpyrifos to Corbicula fluminea, Anodonta woodiana, Lanceolaria gladiola were3.651mg/L,7.288mg/L and13.218mg/L, respectively; the96h-LC50of triad imefon to Bellamya aeruginosa and Cipangopaludina cathayensis were15.223mg/L and16.885mg/L, the168h-LC50of chlorpyrifos to Corbicula fluminea, Anodonta woodiana, Lanceolaria gladiola were18.266mg/L,24.897mg/L and38.252mg/L, respectively. In general, the toxicities of chlorpyrifos and butachlor to the five subjects were roughly at the same level, and the toxicity of triadimefon is lower by comparison. The populations of different sizes to the same pesticide are different in Sensitivitiy. Sensitivities of river snails in different sizes to the same pesticide are in the order of young snail> small snail> moderate snail> big snail, which indicates the smaller the snail, the more sensitive it is. There is no significant difference of sensitivity of river clams in different sizes to butachlor; Sensitivities of river clams in different sizes to chlorpyrifos and triadimefon are in the order of small clam> moderate clam> big clam.Because acute toxicity test is usually conducted in homogeneous aqueous phase, while the natural aquatic environment is water-sediment system, in which pesticides will absorb and accumulate in the sediment. It is more complicated than the homogeneous aqueous phase. In this paper, acute toxicity of the three pesticides to Bellamya aeruginosa and Corbicula fluminea was tested in water-sediment system, and the differences between the results of acute toxicity test in water-sediment system and the results of the traditional method were compared. Results showed that after pesticide was put into the water sediment system, its concentration in water declined rapidly, which means the pesticides in water transferred to the sediment obviously. In the experiment with Bellamya aeruginosa, the concentration of chlorpyrifos, butachlor and triadimefon in water at96h fell by85.1%,52.5%and26.2%, respectively, while the concentration of the three pesticides in sediment rose to106.5%,102.5%and106.5%of that in water at0h, respectively. In the experiment with Corbicula fluminea, the concentration of chlorpyrifos, butachlor and triadimefon in water at168h fell by99.1%,65.5%and21.1%, respectively, while the concentration of the three pesticides in sediment rose to100.2%,94.3%and87.3%of that in water at0h, respectively. Compared with the results of sensitivity test in different sizes, the toxicity of the three pesticides to Bellamya aeruginosa was reduced in water-sediment system, and the toxicity of chlorpyrifos, butachlor to Corbicula fluminea was increased, while that of triadimefon to Corbicula fluminea remained unchanged.In this paper the bio-concentration of the three pesticides in Bellamya aeruginosa was studied. Results showed the concentration of the three pesticides in Bellamya aeruginosa increased with the increase of experimental time and trial concentration, finally it became balanced. The higher the concentration, the slower it came to balance. In general, the concentration in visceral mass is significantly higher than that in foot. As for the three pesticides, the enrichment ability of Bellamya aeruginosa to chlorpyrifos is higher than to butachlor and triadimefon, with the BCF maximum of 858.9. The enrichment ability of Bellamya aeruginosa to butachlor and triadimefon was almost the same, with the BCF maximum of17.8and19.4. respectively.