Intergrading Water Quality Parameters, Benthic Fauna and Acute Toxicity Test for Risk Assessment on an Urban-Rural River

Climate change, river pollution and loss of biodiversity are increasing and becoming global environmental concerns. The Yellow River is China's mother river, providing water for about 114 million residents in towns and cities along its route. Yet in 2012, the Yellow River received 4.474 x 10(9) tons of sewage containing a large number of exogenous pollutants, posing a huge ecological and public health threat. Water quality safety is not only a matter of ecosystem health but also of human survival and social development. Therefore, the effects of pollutants on water quality safety should be carefully studied, which is important to ensure the sustainability of the Yellow River and the surrounding cities and towns. In this study, water and sediment samples from the Jishan River of the Juancheng, a typical city in the lower reaches of the Yellow River, were collected and evaluated by integrating the traditional physicochemical water indicators, benthic Index of Biological Integrity (B-IBI) and zebrafish embryotoxicity test. The results showed that water dissolved oxygen, pH, total nitrogen and total phosphorus were strongly correlated with zebrafish embryonic teratogenicity, lethality, abundance index and Shannon Winner index. A total of 21 benthic species were collected, including mollusks, arthropods and annelids, with the upper reaches having the largest biomass and B-IBI values indicating the urban reaches have better biological integrity than rural reaches. The teratogenic rate of zebrafish embryos in raw water was greatest in rural rivers and was significantly different from the negative control (p < 0.05). When exposed to 100 mg/mL sediment samples, embryo hatching rates were inversely correlated with teratogenic rates, with lethal rates reaching over 96% in all rural reaches. The results showed that the water quality safety at the rural farms in the Yellow River transfer-type towns is poor, and they especially recommended that the river near the farms in rural areas should be monitored with emphasis.