The effect of particle size on the bioavailability of estrogenic chemicals from sediments.

The effects of particle size on the bioavailability of estrogenic chemicals in the sediments from the Yeongsan River and its tributaries in South Korea were evaluated for 2006 and 2007. Samples for chemical analysis and bioassays were collected from 6 sampling sites during both dry and rainy seasons. The pore water of the sediment samples was extracted, and estrogenic chemicals were eluted using a liquid-liquid extraction (LLE) method. Concentrations of 4-nonylphenol (NP), 4-tert-octylphenol (OP), bisphenol A (BPA), estrone (E1), 17beta-estradiol (E2), 17 alpha-ethynylestradiol (EE2) and genistein (Gen) were analyzed by gas chromatography-mass spectrometry (GC-MS). To evaluate bioavailability, hepatic vitellogenin (Vtg) concentrations of male Japanese medaka were measured after exposure to the sediment or its fractions for 7d. NP, BPA and E2 were detected in all the sediment sample extracts from the Yeongsan River and its tributaries. The concentrations of NP in the sedimentary samples ranged from 60 to 400 ngg(-1) on a dry weight basis. Similarly, OP and E2 were detected in nearly all the sediment extracts, with concentrations of 13 and 26 ngg(-1), respectively. According to the bioassay test results, all the sediment samples significantly induced Vtg in male fish after 7d of exposure. Fractionation of sediments into different size-classes (i.e., particle size >1 microm, particle size <1 microm) eliminated bioavailable estrogenic activity, but fine particles of less than 1microm in size increased the absorption of E2 from E2-amended sediment particle fractions. Consequently, the study suggested that the presence of particles and its interaction in the water environment might change the bioavailability of estrogenic chemicals.

Effect of dissolved organic matter on the growth of algae, Pseudokirchneriella subcapitata, in Korean lakes: the importance of complexation reactions.

The objective of this study was to investigate the effect of dissolved organic ligands, such as EDTA, humic acids, hydrophobic and hydrophilic fractions of dissolved organic matter (DOM), on the growth of Pseudokirchneriella subcapitata in cultured media and natural lake waters. The growth of algae was gradually increased on the addition of dissolved organic ligands, but markedly declined at high concentrations, due to reduced bioavailable iron concentrations (e.g., Fe3+ and Fe'--inorganic ferric iron). The results demonstrated that the high growth rates of P. subcapitata were correlated with the hydrophobic, but not hydrophilic, DOM from five lakes, spiked under the nutrients-controlled conditions. This was attributed to the role of DOM in controlling the bioavailable iron due to complexation of Fe(III) with -COOH and -OH functional groups on the hydrophobic DOM. Therefore, the hydrophobic DOM, as chelating agent, is a biologically important component in the lake waters, which affects the algal growth by interacting with bioavailable iron in the lake water and can change the results of bioassay experiments.

Comparative whole effluent toxicity assessment of wastewater treatment plant effluents using Daphnia magna.

An approach to compare the toxicities employing the whole effluent toxicity (WET) test, using Daphnia magna and chemical analysis with GC/MS and ICP/MS, was conducted to the nine South Korean wastewater treatment plants (WWTPs). From the chemical analysis and bioassay experiments, heavy metals (i.e., Cu and Zn) were found to be the major compounds causing toxic effects toward D. magna. In the whole effluent toxicity (WET) tests using D. magna, toxicities were observed in 34% of the effluent samples. However, the biological toxic unit (TU) value showed a non-toxic response (i.e., 0 TU) in many samples despite the response indicated by the chemical TU values. This may be due to the species sensitivity, environmental parameters, mixture effects, and limitation of the chemical analyses.

Ecological health assessments based on whole effluent toxicity tests and the index of biological integrity in temperate streams influenced by wastewater treatment plant effluents.

Whole effluent toxicity (WET) tests and ecosystem health assessments, based on test guidelines of U.S. Environmental Protection Agency (U.S. EPA) and index of biological integrity (IBI), were conducted on various streams located in Youngsan River watershed, Korea. The WET tests showed that about 33 and 82% of wastewater treatment plants (WWTPs) exhibited significant toxicity to Daphnia magna and Selenastrum capricornutum, respectively. Small WWTPs with low discharge volumes contributed less than 1% to the total stream toxicity. Fish community compositions and trophic guild analysis showed that the diversity index was greater in the control than in impacted streams, and the proportion of omnivore species was less in the control. Also, ecosystem health assessments, based on the IBI, showed distinct differences between the control and impacted sites of WWTPs. Model values of the IBI, based on 12 stream data sets, averaged 28, which is judged as a fair to poor condition according to the U.S. EPA criteria. The mean IBI in the control sites was 42, indicating good stream condition, whereas the impacted sites was scored 21, indicating poor condition. Overall, WET tests and ecosystem health assessments suggested the WWTP effluents had evident toxic effects on the biota, and impacted the species compositions and trophic guilds, resulting in degradation of the stream ecosystem health.

Whole effluent toxicity (WET) tests on wastewater treatment plants with Daphnia magna and Selenastrum capricornutum.

Whole effluent toxicity (WET) tests, with Daphnia magna and Selenastrum capricornutum, were introduced to evaluate the biological toxicities of effluents from the wastewater treatment plants (WWTPs) in Korea. In WET tests of WWTPs effluents, 33.3% (33/99) for D. magna and 92.6% (75/81) for S. capricornutum revealed greater than 1 toxic unit (TU), even though all the treatment plants investigated were operating in compliance with the regulations, as assessed using conventional monitoring methods (i.e., BOD and total concentration of N or P, etc). There were only minor differences in toxicities according to the types of influents (municipal and agro-industrial) in all treatment plants. However, the effluents treated by an activated sludge treatment process were found to exhibit significantly lower toxicity than those treated by rotating biological contactor (RBC) and extended aeration processes. The seasonal variations in the toxicity were lower in the summer compared to winter, which may have been due to the rainfall received to the sewage intake system during the former period. The impact of WET on river water was also investigated based on the discharge volume. At sites A and B, the total impact of toxicity to stream and river waters was observed to be 70.9% and 90.4% for D. magna and S. capricornutum, respectively. The other four small treatment plants (sites F, G, H and I), with relative discharging volumes between 0.001 and 0.002, contribute less than 1% to the total toxicity.

Estimating the combined toxicity by two-step prediction model on the complicated chemical mixtures from wastewater treatment plant effluents.

The toxicities of chemical mixtures containing 10 compounds, detected in wastewater treatment plant (WWTP) effluents, were investigated using Daphnia magna in a two-step prediction (TSP) model. The 10 chemicals determined by gas chromatography/ mass spectrometry in WWTP effluents included three groups: Three acetylcholinesterase inhibitors, six narcosis inhibitors, and one seedling root inhibitor. In the first step, a concentration addition (CA) model was used to predict the mixture toxicities for the three component groups with similar modes of action; in the second step, an independent action (IA) model was used for the newly developed concentration-response curves from the three CA predictions. The CA predictions did not show a statistically significant difference from the observed results with respect to the three groups of chemicals, whereas the IA model did not conform to the experimental results. Therefore, the concentration-response curves obtained from the mixture toxicity tests in each group was considered as a single curve and applied in the next step of the mixture toxicity prediction. However, the observed toxicity of the 10-chemical mixture showed large differences from the results of the IA and CA model predictions, whereas the TSP model predicted the toxicity well and with statistical significance (p = 0.0501, n = 17). This suggests that the TSP model would provide a valid prediction for a randomly selected chemical mixture having various modes of action if the concentration-response function for an individual component is obtained.