The Occurrence,Distribution And Fate Of Cyclic Volatile Methylsiloxanes In The Environment Matrices From Dongting Lake

Cyclic volatile methylsiloxanes(cVMS)is a new organic pollutant with environmental risk.Because of its high thermal stability,low surface tension and other special physical and chemical properties,it is widely used in the fields of industrial production,daily life,architecture and medical treatment.With the continuous emission of cVMS into the environment,the risk of environment and human exposure is increasing,and its sustainability,toxicity and bioaccumulation in the environment have been paid more and more attention in recent years.In recent years,China’s rapid economic growth and population growth has become the largest producer and user of siloxane in the world.As the second largest freshwater lake in China,Dongting Lake is an important fishery breeding base,which is bound to be polluted by a certain degree of cVMS.However,there are few reports about the pollution status,source and risk assessment of cVMS in Dongting Lake.The main part of this study was to select the main part of Dongting Lake: the East Dongting Lake as the research area,explored the occurrence,source,spatial change of the cVMS in Dongting Lake water,sediment and soil,and the seasonal changes with the period of abundant water and dry water.In this study,liquid and solid liquid extraction,such as liquid and solid liquid extraction,are respectively optimized to deal with the liquid and solid samples,respectively,in order to solve the problem that the cVMS is relatively low in the environmental medium,and the liquid and solid samples are treated respectively.The high efficiency extraction of the low concentration cVMS in the sample is realized.The extracted cVMS was detected.Through sampling and analysis of Dongting Lake,the results show that the total cVMS concentration in the Dongting Lake region is 64.89-489.07 ng/L,and the total cVMS concentration in the sediment is 26.63-996.95 ng/g dry weight,and the total cVMS concentration in the soil is < LOD-163 ng/g dry weight.The total cVMS content in the samples is positively correlated with total organic carbon(TOC)in the samples.The cVMS content in the downstream samples is higher than that in the upstream samples.The cVMS species in the samples were mainly D5,followed by D6 and D4.Among them,the highest content of cVMS is in the lower reaches of Dongting Lake.The total cVMS content in the shipyard is the highest,which is 996 ng/g dry weight,and the concentration of Yueyang Tower and seven Li Shan is relatively high.Through the preliminary analysis of the source of cVMS in the sample,the source of cVMS has the same source of pollution.The results show that the main source of cVMS in the Dongting Lake regional samples is the direct or indirect discharge of domestic sewage from the surrounding residents,the effluent from the industrial wastewater,the effluent from the municipal sewage treatment plant,and so on,and cVMS in the samples near the source of the pollution.The content of cVMS was significantly higher than that of the sample far from the source.The area of this study is mainly concentrated in the waters near the densely populated area of Dongting Lake.There are too many boats to go back and forth,fishing boats,industrial ships and merchant ships,which may also be one of the sources of cVMS in Dongting Lake.After sampling every half year of Dongting Lake,it was found that the concentration of cVMS was slightly greater than that in the dry period,but on the whole,there was no obvious increase in the content of cVMS in the Dongting Lake regional samples.The risk assessment study showed that the current content of cVMS in the Dongting Lake samples did not have a risk impact on aquatic organisms and surrounding residents(the risk values of D4 and D5 were 4.4 g/L and 17 mu g/L respectively).Although there is no risk at present,the long-term emission and exposure may increase cVMS to the natural environment and human health in the future because of the high concentration of human beings in the lake area and the long-term emission of cVMS.Therefore,increasing the long-term monitoring of Dongting Lake area is an important means.