Toxicity Evaluation And Risk Assessment Of Surface Sediment By Bioassay In Liaohe River Protected Areas,China

In this study,chironomid larvae,representative benthic invertebrate,were selected as the test organisms.The toxicity of contaminants in surface sediments collected from the Liaohe River Protected Area was evaluated by TIE method combined with chemical analysis to preliminarily clarify the toxic pollutants.For further assessment toxicological causation,acute and chronic toxicity characterizations of the identified characteristic pollutants Cd and ammonia nitrogen were carried out.The concentration,source and ecological risk assessment of PCBs and PCDD / Fs,which induce the activity of aryl hydrocarbon receptor agonists in the sediments of Liaohe River Protected Area,were studied to evaluate their risk status to water environment.The main findings are as follows:(1)The results of sediment TIE confirmed that ammonia nitrogen and heavy metal Cd were the main toxic pollutants that caused the biological toxicity of surface sediments in the Liaohe River Protected Area.(2)The results showed that the concentration of ammonia nitrogen and Cd had a significant positive correlation with the acute death rate of chironomid larvae.Chronic toxicity tests showed that with the increase of ammonia nitrogen concentration,the eclosion of chironomid larvae had different degrees of delay and the eclosion rate also dropped significantly.With the adding of the level of Cd,the eclosion of chironomid larvae was delayed,the avoidance rate of chironomid larvae on pollutants and larval mouthparts deformity rate increased significantly.(3)It was discovered that the concentrations of PCDD/Fs in the sediments of the Liaohe River Protected Areas were at medium level,while the WTO-TEQs were at relatively high level compared with other regions.The congener patterns of PCDD/Fs in Liaohe which showed OCDF,was the dominant congener followed by 2,3,7,8-HpCDF.Source analysis showed that PCDD/Fs in sediments were mainly from gasoline or diesel vehicle emissions and solid waste incineration.(4)By studying the risk of PCBs in sediments,it was found that PCBs concentrations in sediments of the Liaohe River Protected Areas were at medium level and TEQs concentrations were at a low level.PCBs came mainly from electronic waste and commercial products such as paint additives.