Toxicity Changes of Heavily Polluted River Sediments on Daphnia magna Before and After Dredging.

Most of the pollutants discharged into the water will deposit at the bottom of the river and may cause biological toxicity. Daphnia magna-elutriate toxicity bioassay was usually applied to evaluate sediment toxicity. However, the loss of hydrophobic pollutants during the elutriating will lead to the underestimation of sediment toxicity. The purpose of this study is to apply the optimized immobilized sediments to D. magna test, so it can be directly exposed to the sediments and get accurate sediment toxicity results. The optimized immobilized sediment was prepared by mixing 1 g sediment with 7.5 mL 3% (w/v) alginate and hardened in a 4% (w/v) CaCl2 solution. Based on D. magna acute toxicity test, the median lethal concentration values (LC50) of the spiked Cu and diuron measured by using immobilized sediment were both lower than that of using the elutriate, in which the difference of Cu-LC50 reached a significant level. The toxicity changes of sediment in the polluted rivers before and after dredging were then be evaluated by using the immobilized sediment. The toxicity of the sediments at four sites decreased from acute-toxic (pro-dredging) to slight-acute-toxic and nontoxic (post-dredging).

Assessment of Biological Toxicity and Ecological Safety for Urban Black-Odor River Remediation.

The judgment and assessment of remediation effect on urban black-odor river still depend on the physical-chemical parameters and lack in ecological safety effects. A set of combined biological toxicity tests were applied to evaluate the ecological effects of one urban black-odor river before and after the remediation. The special growth rate of Chlorella vulgaris and mortality rate of Daphnia magna were used to assess acute toxicity. The Salmonella Typhimurium/Reverse Mutation Assay was applied to test the mutagenicity. The tests by C. vulgaris growth showed that there was no inhibition before and after remediation by overlying water, in contrast promoted the growth of C. vulgaris. The tests by D. magna showed slight toxicity on site 3# before remediation and nontoxic after remediation. The mutagenicity of organic extracts from overlying water at all sampling sites were positive before remediation, but were eliminated after remediation except from 3 of 4 sites on TA98 strain. The addition of the liver microsomal S9 induced the positive mutagenicity on site 4# compared to S9 absence. The results clarified the applicable and the importance of the biological toxicity tests on assessing the remediation effect and potential ecological risk of urban black-odor river.

Development and application of a novel whole sediment toxicity test using immobilized sediment and Chlorella vulgaris.

The sediments of water bodies are not only pollutants sink but also sources of pollution. The assessment for the whole-sediment toxicity is still challenging research. Although the application of immobilized algal bead could overcome the practical difficulties in sediment toxicity assay, the weak growth and reduced sensitivity of algae inside the bead restricted its application. In this study, a sediment toxicity test was developed using immobilized sediment and Chlorella vulgaris. The immobilized sediment was prepared by mixing 2 g freeze-dried sediment and 15-mL 3% (w/v) alginate and hardened in a 4% (w/v) CaCl2 solution. Based on a C. vulgaris growth inhibition test and using the immobilized sediment, the median effective concentration value (EC50) of the spiked Cu and diuron was 506.23 and 2.37 mg/kg respectively, lower than that of using immobilized algae (719.62 and 3.12 mg/kg respectively). The Cu and diuron concentrations in the corresponding overlying water from the spiked immobilized and free sediment showed that sediment pollutants' diffusion capacity was not decreased after immobilization. By using the immobilized sediment in algae toxicity bioassay, the changes in the sediment toxicity of a polluted river before and after dredging was evaluated. The C. vulgaris growth inhibition in sediment A decreased from 81.94% to 8.43%; sediment B remained unchanged; sediment C stimulated the growth of C. vulgaris before dredging (-15.56%), but inhibited the algae growth after dredging (26.88%), and sediment D decreased growth inhibition from 32.66% to -12.60%.

Evaluation by the Ames Assay of the Mutagenicity of UV Filters Using Benzophenone and Benzophenone-1.

Ultraviolet absorbing chemicals (UV filters) are widely used in personal care products for protecting human skin and hair from damage by UV radiation. Although these substances are released into the environment during production and consumption processes, little is known about their genotoxicity effects. Our previous studies have shown that benzophenone-type UV filters exhibited acute toxicity on three species of aquatic organisms. Mutagenesis by benzophenone (BP) and benzophenone-1(BP-1) was tested in the present study by the Salmonella typhimurium/reverse mutation assay (Ames assay). All the positive reverse mutations occurred in the absence of the S9 liver extract system for both chemicals. From BP, positive mutation effects on the TA102 strain at doses of 0.05 µg/plate and 0.5 µg/plate were detected. From BP-1, positive mutation effects on the TA97 strain at doses of 0.05 µg/plate and 0.5 µg/plate, and on the TA100 strain at a dose of 0.5 µg/plate, were detected. A mixture of BP and BP-1 exhibited mutagenicity on the TA97 and TA100 strains. For the TA97 strain, the positive mutation results were detected at 10% and 50% of the mixture. For the TA100 strain, the results were detected when the mixture was at 5% and 10%. In the mixture at 5%, the concentrations of BP and BP-1 were 3.5 µg/plate and 14 µg/plate, respectively. In the 10% mixture, the doses of BP and BP-1 were 7 µg/plate and 28 µg/plate, respectively. In the 50% mixture, the doses of BP and BP-1 were 35 µg/plate and 140 µg/plate, respectively. The mixture test results suggested that there was antagonism in mutagenicity between BP and BP-1.

Acute Toxicity and Ecological Risk Assessment of Benzophenone-3 (BP-3) and Benzophenone-4 (BP-4) in Ultraviolet (UV)-Filters.

Ultraviolet (UV)-absorbing chemicals (UV filters) are used in personal care products for the protection of human skin and hair from damage by UV radiation. Although these substances are released into the environment in the production and consumption processes, little is known about their ecotoxicology effects. The acute toxicity and potential ecological risk of UV filters benzophenone-3 (BP-3) and benzophenone-4 (BP-4) on Chlorella vulgaris, Daphnia magna, and Brachydanio rerio were analyzed in the present study. The EC50 values (96 h) of BP-3 and BP-4 on C. vulgaris were 2.98 and 201.00 mg/L, respectively. The 48 h-LC50 of BP-3 and BP-4 on D. magna were 1.09 and 47.47 mg/L, respectively. The 96 h-LC50 of BP-3 and BP-4 on B. rerio were 3.89 and 633.00 mg/L, respectively. The toxicity of a mixture of BP-3 and BP-4 on C. vulgaris, D. magna, and B. rerio all showed antagonistic effects. The induced predicted no-effect concentrations of BP-3 and BP-4 by the assessment factor method were 1.80 × 10-3 and 0.47 mg/L, respectively, by assessment factor (AF) method, which were both lower than the concentrations detected in the environment at present, verifying that BP-3 and BP-4 remain low-risk chemicals to the aquatic ecosystem.