| Chongming Island is the third largest island in China and the largest alluvial island in the world.Chongming Island is not only an important agricultural product base in Shanghai,but also an important aquatic product production base in the Yangtze River Delta.The positioning of its international ecological island puts forward higher requirements for the island's ecological environment protection.Polycyclic aromatic hydrocarbons(PAHs),as a kind of persistent organic pollutants widely existing in the environment,are widely detected in the atmosphere,water,sediment and aquatic products due to their semi volatility and bioaccumulation.Therefore,in-depth study on the distribution characteristics,ecological risks and health risks of PAHs in the aquaculture pond of Chongming Island is of great significance for the development of aquaculture,the health of residents and the protection of ecological environment in Chongming Island.This paper takes Chongming Island as the research area,and 16 kinds of PAHs that are preferentially controlled by the United States Environmental Protection Agency(USEPA)as the research object.GC / MS method was used to determine the exposure concentration of water,surface sediment and PAHs in the aquaculture pond of grass carp in Chongming Island from July 2018 to January 2019.Statistical and GIS methods were used to analyze the pollution level,temporal and spatial distribution characteristics and composition characteristics.The main component analysis method and characteristic molecular ratio method were used to analyze the source of PAHs,and the corresponding environmental treatment was proposed Countermeasures.On this basis,based on the potential exposure scenarios of PAHs,the carcinogenic risk and non carcinogenic health risk of PAHs to different populations in Shanghai under different exposure routes were analyzed.The ecological risks of PAHs in water and sediment were characterized by BAP toxicity equivalent method,quotient value method,sediment quality standard method and sediment quality standard method.This paper analyzes the PAHs monomer with great potential hazards in risk assessment,and puts forward corresponding countermeasures to deal with potential risks.The main conclusions are as follows:(1)The concentration range of ? PAHs in the pond water of Chongming Island is ND(the concentration is lower than the detection limit,not detected)~ 0.42 ?g·L-1,the average content is 0.041 ?g·L-1;the concentration range of ? PAHs in the sediment is ND ~ 1654.09 ?g·kg-1,the average content is 95.13 ? g·kg-1;the concentration range of PAHs in the muscle of cultured grass carp is ND ~ 221 ?g·kg-1,the average content is 7.37 ?g·kg-1.Its spatial distribution is characterized by "low in the middle,high around,and higher in the West than in the East".Compared with other areas,the content of ?PAHs in the aquaculture pond of grass carp in Chongming Island is in the low to middle level.(2)The main source of PAHs in the study area is the mixture of petroleum and various combustion sources.Among them,the main sources of PAHs in water body in summer are coking emission,grass burning,and motor vehicle emission;in autumn,grass burning is the main source,motor vehicle emission is the second;in winter,biomass combustion is the main source.The main source of PAHs in surface sediments is the mixture of petroleum and various combustion sources,and the proportion of petroleum sources increases gradually in summer,autumn and winter.(3)On the whole,the potential ecological risk caused by PAHs in the aquaculture pond of grass carp in Chongming Island is low.The total risk of PAHs in the water body is very low,and only in some coastal ponds there will be a low level of potential ecological risk.In summer and autumn,the potential ecological risk of PAHs is relatively high.The potential ecological risk of PAHs in the sediment is low,but there is a certain ecological risk in the pond in the west of the island in summer.From the perspective of spatial distribution,there is a relatively high probability of potential risk in the coastal pond of Chongming Island,and the risk of the pond in the west of the island is higher than that in the East.In terms of seasonal variation,the risk in summer is the highest,reaching the medium potential risk level,followed by autumn,and the lowest in winter.(4)The carcinogenic risk of PAHs exposed to the pond water of Chongming Island by adults and children in Shanghai is within the maximum acceptable level of cancer risk,and children are slightly higher than adults.The exposure risk of adults mainly comes from exposure,while that of children mainly comes from the way of drinking by mistake.The maximum allowable daily intake of carcinogenic risk of cultured grass carp in Chongming Island is 1471.78 ~ 1501.53 g·d-1.Eating grass carp in Chongming Island will not produce carcinogenic health risks.(5)During the prevention and control of PAHs in the study area,we should pay more attention to the seven PAHs monomers,DBA,Ace,Phe,Ba A,Chr,Flu and Pyr,whose high exposure concentration is the main factor causing potential risks.From the point of view of controlling pollution sources,we should pay attention to the coordinated treatment of water environment around Chongming Island,the management and structure optimization of factory emissions in the surrounding areas,and the energy consumption structure of residents in Chongming Island should also be properly adjusted.The fishery practitioners in Chongming should pay attention to the risk prevention and control of PAHs in coastal ponds,especially in summer and autumn.It is suggested that the aquaculture households should desilting the ponds after the completion of the breeding cycle to prevent the accumulation of PAHs in the surface sediments. |
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