Toxic effects of heavy metals on the freshwater benthic organisms in sediments and research on quality guidelines in Poyang Lake, China

Abstract

Sediment Quality Guidelines (SQGs) are the standard for protecting organisms from chemical hazards. Species Sensitivity Distribution (SSD), a typical derivation method of the SQGs, has been widely used for organic pollutants, whereas there are few studies applied on metals. This study investigated the toxic effects of Cu, Cd, Zn, and Pb to Limnodrilus hoffmeisteri and Chironomus larvas, obtained the SQGs by the SSD method, and evaluated the ecological risks of Poyang Lake, China. The test endpoints of L. hoffmeisteri (mortality and autotomy rates) and C. larvas (mortality and growth inhibition rates) after 21- and 14-day exposure of Cu, Cd, Zn, and Pb in the sediments of Poyang Lake were conducted, respectively. The SSD method was used for the curve optimal fitting and the SQG calculation based on the biotoxicity data of the local species in Poyang Lake. The ecological risk of Poyang Lake was assessed by calculating the potential ecological risk index (RI). The toxicity quotient Q was used for the SQGs verification of Cu, Cd, Zn, and Pb. According to the results of toxicity tests, C. larvas are more sensitive to the stress effects of heavy metals compared to L. hoffmeisteri. The Criteria Continuous Concentration (CCC) of Cu, Cd, Zn, and Pb were 34.9, 0.5, 58.2, and 35.0 mg kg−1, respectively. The Criteria Maximum Concentration (CMC) of Cu, Cd, Zn, and Pb were 56.35, 2.0, 151.3, and 175.0 mg kg−1, respectively. We selected C. larvas as experimental organisms to verify the SQGs and the results conformed to the meaning of guidelines. The RI values for heavy metals in all sampled sediments (P1 to P10) showed low potential ecological risks (RI 120) of P2, P6, and P10 are mainly attributed to Cd. In general, the CCC and CMC of Cu, Cd, Zn, and Pb conformed to the meaning of guidelines. The ecological risk index method showed that Poyang Lake was slightly polluted by Cu, Zn, and Pb, while heavily polluted by Cd. The results of the SQGs of heavy metals and ecological risk assessment can provide theoretical support for monitoring heavy metal pollution and biodiversity protection in Poyang Lake.