Toxic Effects Of Dichloromethane And Dichloroethane To Chlorella Pyrenoidesa

Regarding Chlorella pyrenoidosa as testing organism, the acute toxic and biochemical effects of two kinds of common VOCs such as dichloromethane and 1,2-dichloroethane to Chlorella pyrenoidosa was assessed.After isolation, purification and synchronous culture, and correlation analysis between cells and absorbance, OD680 is used to calculate cells. And then, 96h-EC50 of dichloromethane and 1,2-dichloroethane to Chlorella pyrenoidosa are fixed. The experimental results showed that dichloromethane and 1,2-dichloroethane could inhibit the growth of the algae obviously. With the increasing of the concentration of the organic toxicant, the cell density decreased correlation between toxicant concentration and time. The 96h-EC50 of dichloromethane to Chlorella pyrenoidosa was 550.1 mg/L; the 96h-EC50 of 1,2-dichloroethane to Chlorella pyrenoidosa was 276.0 mg/L, the toxicity of 1,2-dichloroethane is a little stronger than that of dichloromethane. The joint toxicity of two organic toxicants was showed as antagonism by different analytical methods.Basing on analyzing of cells of algae, the content of chlorophyll a, the activities of superoxide dismutase(SOD) and catalase(CAT), the content of malondialdehyde(MDA) in the algae had been tested, and results showed that it was significantly affected under the organic toxicant exposure. The activities SOD and CAT was increased at first and then decreased remarkably with the increasing concentration of the organic toxicant, showed as "Bell Shaped Curve". The content of malondialdehyde(MDA) flared up and the lipid peroxidant aggregated with the increasing of the concentration of the organic toxicant. The results suggested that primary mechanism of the two organic toxicant on Chlorella pyrenoidosa cells may be related to the oxidation damage of lipid and other biological large molecules caused by dichloromethane and 1,2-dichloroethane.In addition, by observation of microstructure of Chlorella pyrenoidosa, structures of membrane, pyrenoid, chloroplast and nucleus were damaged by the stress of toxicants. The shape of the nuclear protein became irregular greatly. Starch sheath was separated from nuclear protein obviously. Lamellar structure of chloroplast was damaged. There are much cytoplasm outside the cell. There are many electron dense granules. They most likely are peroxisomes.The results of this study will provide a theoretical basis for pollution control and treatment, and make sense to environmental monitoring by algae, ecological risk assessment and environmental protection.