Zinc bioavailability to aquatic organisms varies greatly under different pH values. In the present study, five native species in China and four common international test species were selected to investigate the influence of changing pH on acute zinc toxicity. The results showed that the higher trophic levels exhibited increasing sensitivity to zinc as pH decreased. However, when the pH value was between 8 and 11, the acute toxicity of zinc was relatively constant. In addition, by using a species-sensitivity distribution (SSD) method, the short-term hazardous concentrations of zinc at different pH values (based on the 5th percentiles of the pH-specific SSDs) were determined to be 17.26 µg/L (pH 4), 48.31 µg/L (pH 5), 80.34 µg/L (pH 6) and 230.6 µg/L (pH 7), respectively. The present study provides useful information for deriving water quality criteria and assessing the risks of metals in the near future. Electronic supplementary material The online version of this article (10.1007/s00128-018-2441-2) contains supplementary material, which is available to authorized users.

Acute toxicity of aromatic amines and phenols and their mixtures to bacteria in natural waters was determined and the median inhibition concentration IC(50) values for single compounds and IC(50mix) values for binary and multiple mixtures were obtained. Based on the quantitative structure-activity relationship model for single chemical toxicity, a two-descriptor model accounting for n-octanol/water partition coefficient (log P(mix)) and the energy of the lowest unoccupied molecular orbital (E(LUMOmix)) was developed for the toxicity of a mixture: log(1/IC(50mix) = 0.326 log P(mix) - 0.660E(LUMOmix) + 3.323 (n = 32, R(2) = 0.834). This model can be used successfully to predict the toxicity of a mixture, whether binary mixtures or multiple mixtures of three or four chemicals are used as predictors.

In conventional reservoir operations, energy and economic benefits are typically optimized, and ecosystem values are only addressed as constraints. To reduce the negative influence of reservoir operation on the downstream ecological environment, ecological targets should be incorporated into reservoir operations. The concept of environmental flow was developed to define the quantity, quality and timing of water flows that are required to sustain freshwater and estuarine ecosystems. Based on the salinity requirements of the indicator species and the relationship between salinity and the freshwater inflows, environmental flows for the Yangtze Estuary were determined. Subsequently, an ecological reservoir operation model was established that incorporated the ecological target for the protection of the Qingcaosha water source; the Non-dominated Sorting Genetic Algorithm II was applied to the model. Three typical periods of wet, normal and dry years were selected, and the operation results were analysed for the downstream Datong cross-section and the environmental flows. The results showed that joint scheduling should be performed for the reservoirs upstream of the Yangtze Estuary. In June of wet and normal years, the current run-off of the Datong should be reduced by 13.5% and 5%, respectively. In July and September of wet years, current run-off should be reduced by 30.6% and 25.5%, respectively, as these reductions will not negatively affect the drinking-water sources. The results of this study should provide guidance in decision-making to improve the operation of the Three Gorges Reservoir.

In the present study, multibiomarker effects of the river water of three representative sections in Nanjing section of the Yangtze River were investigated in goldfish (Carassius auratus). The organic toxicants were extracted from the water samples using solid phase extraction. Acetylcholinesterase (AChE), glutathione-S-transferase (GST), 7-ethoxyresorufin-O-deethylase (EROD), glutathione peroxidase (GPx) and Na+/K+-ATPase activities were determined after exposure of the extracted components. The fractions of water samples from three sections (Daqiao, Sanchahe and Jiangxinzhou) altered these enzymatic activities. With the change of the extracts polarity, the levels of AChE, GST, EROD, Na+/K+-ATPase activities were different. The responses of enzymatic activities were mostly significant for those exposures of intermediate polar components (50-80% methanol extracts) and weakly polar components (ether and ether/hexane extracts). It has been shown that toxicants were mainly concentrated in these fractions in the Yangtze River (Nanjing section). With regard to response for different sections, EROD and GST activities seem to be more sensitive biomarkers. Integrated biomarker response index (IBR) were calculated and used to evaluate an integrated impact of pollutants from different sampling sections. The order of negative biological effects of the three sections was Jiangxinzhou>Sanchahe>Daqiao. The wild fish living in Nanjing section of the Yangtze River were at potential ecological risk.