Effects of phenanthrene on the mortality, growth, and anti-oxidant system of earthworms (Eisenia fetida) under laboratory conditions.

To assess the toxic effects of phenanthrene on earthworms, we exposed Eisenia fetida to artificial soils supplemented with different concentrations (0.5, 2.5, 12.5, mgkg(-1) soil) of phenanthrene. The residual phenanthrene in the soil, the bioaccumulation of phenanthrene in earthworms, and the subsequent effects of phenanthrene on growth, anti-oxidant enzyme activities, and lipid peroxidation (LPO) were determined. The degradation rate of low concentrations of phenanthrene was faster than it was for higher concentrations, and the degradation half-life was 7.3d (0.5 mgkg(-1)). Bioaccumulation of phenanthrene in the earthworms decreased the phenanthrene concentration in soils, and phenanthrene content in the earthworms significantly increased with increasing initial soil concentrations. Phenanthrene had a significant effect on E. fetida growth, and the 14-d LC(50) was calculated as 40.67 mgkg(-1). Statistical analysis of the growth inhibition rate showed that the concentration and duration of exposure had significant effects on growth inhibition (p<0.001). Superoxide dismutase (SOD) activity increased at the beginning (2 and 7d) and decreased in the end (14 and 28 d). Catalase (CAT) activity in all treatments was inhibited from 1 to 14 d of exposure. However, no significant perturbations in malondialdehyde (MDA) content were noted between control and phenanthrene-treated earthworms except after 2d of exposure. These results revealed that bioaccumulation of phenanthrene in E. fetida caused concentration-dependent, sub-lethal toxicity. Growth and superoxide dismutase activity can be regarded as sensitive parameters for evaluating the toxicity of phenanthrene to earthworms.

[Toxic effects of dichloromethane and dichloroethane to Chlorella pyrenoidosa].

The acute toxic and biochemical effects of dichloromethane and 1,2-dichloroethane to Chlorella pyrenoidosa were assessed. The experimental results showed that dichloromethane and 1, 2-dichloroethane had some inhibition to growth of the algae. With increasing concentration of the organic toxicant, the cell density decreased. The 96 h-EC50 of dichloromethane to Chlorella pyrenoidosa was 550.1 mg/L; the 96 h-EC50 of 1,2-dichloroethane to Chlorella pyrenoidosa was 276.0 mg/L, toxicity of 1,2-dichloroethane is a little stronger than that of dichloromethane; the joint toxicity of two organic toxicants was showed as antagonism. Content of chlorophyll a, activities of superoxide dismutase (SOD), catalase (CAT) and content of malondialdehyde (MDA) in algae had been significantly affected under the organic toxicant exposure. The activities of SOD and CAT were 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 lipid peroxidant aggregated with the increasing concentration of the organic toxicant. The results suggested that the primary mechanism of two organic toxicants on Chlorella pyrenoidosa cells may be related to oxidation damage of lipid and other biological large molecules caused by dichloromethane and 1,2-dichloroethane.