Pollution Characteristics And Ecological Risk Assessment Of Diuron In The Coastal Waters Of The Yangtze Estuary

Persistent organic compounds(POCs)have long attracted human attention due to their strong environmental toxicity,long half-life in water and complex structure.As a new type of antifouling agent for ships,Diuron has been applied in ship shipping to a certain extent,and is also used as a traditional herbicide in fruit forests and rice cultivation.With the overall planning of China’s land and sea,the integrated development of shipping and river(river)transportation,the rapid development of shipbuilding and maintenance industry,and the increase of ship shipping volume,the production and consumption of marine antifouling paint will also increase significantly,especially the Shanghai Port,which is located at the mouth of the Yangtze River,has various large docks and ports,The risk of the active substances in the antifouling agent of ships,including Diuron,entering the water body is also increasing.This paper takes the marine antifouling agent Diuron in the waters near the Yangtze River Estuary as the research object,based on the content of Diuron in the waters,discusses the spatial distribution characteristics of Diuron in the waters near the Yangtze River Estuary,uses correlation analysis and cluster analysis to explore the source characteristics of Diuron,and In order to further understand the toxic effects of Diuron,an indoor toxicity experiment was conducted on the dominant species of Skeletonema costatum in the Yangtze River Estuary to explore the growth and development of algae under different concentrations,as well as the changes in chlorophyll fluorescence parameters over time.Correlation analysis was used to analyze the impact of Diuron on various parameters.Finally,the risk quotient method was used to explore the pollution level and potential risk status of Diuron on the water environment in the study area,to provide scientific theoretical basis for environmental protection and management in the nearshore waters of the Yangtze River Estuary.The main research conclusions of this article are summarized as follows:(1)Diuron mass concentration was detected in 24 water samples from 3different regions.The detection range of Diuron mass concentration at 10 stations along the Yangtze River Estuary in Shanghai is 182.43～439.38 ng/L;The detection range of Diuron mass concentration at 9 stations in Hengsha Island(inland)waters is83.48～369.25 ng/L;The detection range of Diuron mass concentration at 5 stations in the sea area near the Chinese sturgeon reserve is 1.97～2.85 ng/L.It can be found that the spatial distribution of Diuron in the coastal area is mainly related to the release of ship antifouling paint in the port of ship docking and shipping,while the distribution of Diuron in Hengsha Island(inland)is mainly related to local agricultural activities,and the source of Diuron in the Chinese sturgeon reserve and nearby areas is mainly related to marine hydrodynamic diffusion.(2)In the study of the effects of different concentration gradients and different treatment time on the growth and development of Skeletonema costatum,the growth of Skeletonema costatum was significantly inhibited by Diuron.With the increase of the concentration and treatment time of Diuron,it showed a certain dose-effect relationship.With the increase of the concentration of Diuron,the inhibition effect continued to increase,and the inhibition effect of high concentration(≥0.8mg/L)of Diuron on Skeletonema costatum was more obvious,At the same time,temperature also has certain influence on the growth of algae,Under the same concentration of Diuron,the results showed that the increase of temperature would lead to the stronger toxic effect of Diuron.The order of the toxic effect was 25℃>20℃>22 ℃,which was related to the effect of temperature on the toxicity of Diuron.(2)The study on the effect of different concentration gradients of dichloromethane on the chlorophyll fluorescence parameters of Skeletonema costatum showed that after 96 hours of treatment with diuron,the inhibition rates of maximum photon yield by 1.0 mg/L diuron at different temperatures were 48.0%,55.4%,and100%,respectively.In the analysis of PSII photosynthetic activity parameters of Skeletonema costatum,it was found that as the concentration of diuron increased,the maximum photon yield,maximum relative electron transfer rate,and light energy utilization efficiency parameter values of chlorophyll fluorescence parameters decreased,and the decrease amplitude gradually increased.However,the correlation between the change trend of semi saturated light intensity and dose was not significant.Through correlation analysis of different fluorescence parameters,the maximum photon yield There is a positive correlation between the maximum relative electron transfer rate and the efficiency of light energy utilization,with the greatest impact of dipyridamole on the maximum photon yield,which is related to the mechanism of dipyridamole action.(4)The ecological risk assessment of the Yangtze River Estuary coastal waters using the risk quotient method shows that the Shanghai Yangtze River Estuary coastal waters belong to potential medium risk areas;The farmland cultivation area of Hengsha Island(inland)belongs to a potential medium risk area;The waters near the Chinese sturgeon conservation area are potentially low-risk areas.Although the concentration level of Diuron in the Yangtze River estuary has not reached the level of biological exposure,its concentration level is higher than that of ports or docks in other regions.In order to prevent its continuous accumulation of ecological threats to the marine environment,it is necessary to formulate corresponding laws and regulations to regulate its application in ship pollution prevention and agriculture.