Distribution Of Trihalomethanes In The Haihe River Estuary And Ecological Risk Assessment

Trihalomethanes(THMs),as a class of predominant chlorinated DBPs,contain 4 congeners including chloroform(TCM),bromodichloromethane(BDCM),dibromochloromethane(DBCM),and bromoform(TBM).Due to their potentially carcinogenic and mutagenic properties,numerous researchers have focused on human exposure to THMs and related health risks.However,as a toxic organism,the potential impact of THMs on ecosystem has not been taken into account.The surface water of Haihe River estuary was taken as the object of this study.The concentrations of THMs were determined by liquid-liquid extraction method.The spatial and temporal distribution patterns of THMs were analysed.The ecological risks of THMs were quantitatively evaluated based on species sensitivity distributions(SSD)model and fugacity-based foodweb model,respectively.The main results are as follows:The concentrations of TCM,TBM,BDCM and DBCM were 0.81~7.49 μg/L,0.22~1.46 μg/L,0.058~0.48 μg/L and 0.013~0.79 μg/L,respectively.The total concentration of THMs varied from 1.12 to 8.20 μg/L with a mean concentration of 3.49 μg/L.The concentration of THMs in summer was higher than that in spring,which might be related to temperature,pH and some other factors.According to the spatial distribution,the average concentration of THMs at Dagu Drainage River was the highest.A decreasing trend was occurred for the concentrations of TCM from the estuary to the adjacent sea.However,the levels of TBM and DBCM in adjacent sea were higher than that in estuary.BDCM showed a stable concentration level.The risk quotient ranges of TCM and TBM based on SSD model were 0.00021~0.0023 and 0.00013~0.00085,respectively.The combined ecological risk value of THMs was 0.00038~0.0026,which was far less than 0.1.The ecological risk of THMs in freshwater was generally higher than that of seawater.A combination of fugacity model and foodweb model was constructed in this study.The residue levels of TCM in tissue of thirteen function groups were estimated.The ecological risk of TCM for pelagic fish functional groups was assessed based on internal toxicity data and the result was 00080~0.0073.The risk value based on internal exposure assessment was higher than that based on external exposure assessment by approximately 3 folds.Compared with other contaminants in water and surface sediment from rivers and coastal areas,the ecological risk level of THMs in surface water could be ranked as low.Futher investigation and risk mitigation measures for THMs were needed in this area.