Pollution Characteristics Analysis And Ecological Risk Assessment Of Trihalomethanes In The Typical Estuaries Of Bohai Bay

Trihalomethanes?THMs?are a major class of chlorinated disinfection by-products?DBPs?,including four regulated trihalomethanes?THM₄?and six iodotrihalomethanes?I-THMs?.THM₄includetrichloromethane?TCM?,bromodichloromethane?BDCM?,dibromochloromethane?DBCM?and tribromomethane?TBM?.I-THMsincludedichloroiodomethane?DCIM?,bromochloroiodomethane?BCIM?,dibromoiodomethane?DBIM?,chlorodiiodomethane?CDIM?,Bromodiiodomethane?BDIM?and triiodomethane?TIM?.Due to their potentially carcinogenic,teratogenic 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 aquatic ecosystems has not been taken into account.The surface water in the typical estuaries of Bohai Bay?Beitang estuary and Haihe River estuary?was taken as the object of this study.The concentrations of THMs in water samples were determined,and the composition profiles and the spatial and temporal distribution patterns of the THMs were analysed.The ecological risks of THMs were evaluated using the methods of species sensitivity distribution?SSD?model,probabilistic risk assessment?PRA?and assessment factor?AF?,respectively.The results showed that the concentrations of TCM,TBM,BDCM and DBCM were 0.62⁶.66?2.77±1.76?,0.35¹.25?0.53±0.23?and 0.16¹.41?0.43±0.35?and0.13¹.28?0.31±0.31??g/L,respectively.DCIM was not detected,and the concentrations of BCIM,DBIM,CDIM,BDIM and TIM were ND⁰.42?0.13±0.14?,ND⁰.68?0.08±0.15?,ND⁰.77?0.07±0.17?,ND⁰.34?0.07±0.08?and ND⁰.36?0.05±0.08??g/L,respectively.The total concentration of THMs was 1.58⁹.99?4.44±2.25??g/L.The mean concentrations of THM₄ showed an upward trend,and the mean concentrations of I-THMs first increased and then decreased during the sampling date.From the end of the river to the sea,the mean concentrations of TCM and I-THMs showed a trend of decrease,and the mean concentrations of BDCM,DBCM and TBM first increased and then decreased.Due to the shortage of THMs toxicity data,this study only evaluated the ecological risks of TCM,TBM,BDCM,DBCM and TIM.The methods of SSD model,PRA and AF were used to assess the ecological risks of these five pollutants.The results showed that the ecological risks of them in the studied area were very low,but futher investigation and risk mitigation measures for THMs were necessary.