| Four kinds of volatile cyclosiloxane(D3-D6)were studied in the Bohai Sea and the North Yellow Sea near the Liaodong Peninsula and its adjacent waters.The optimized method of dispersion liquid-liquid microextraction combined with GC-MS was used to analyze and detect the collected seawater samples.Based on the analysis of the concentration level of D3-D6 in different sea areas,the regional distribution characteristics and the variation of the high and low water season were studied.And the emphasis is placed on Dalian and its surrounding waters:In order to explore the possible source of cVMSs in seawater,through the technical route of source analysis,the study on the cVMSs discharge law of effluent from sewage treatment plant was added,and the correlation analysis between the concentration of cVMSs in seawater and the conventional five items was carried out.The concentration of cVMSs in 32 national control points in the coastal area of Liaodong Peninsula was analyzed in four months.The results showed that the total concentration of cVMSs was 36358.97 ng/L,and the mean concentrations of D3-D6 at each point were35.12±73.13 ng/L,145.70±268.39 ng/L,48.04±95.27 ng/L,47.68±61.53 ng/L,respectively.The average concentration of cVMSs in 2016 was 117.74 ±136.85 ng/L.In 2017,the average concentration of cVMSs was 409.85±395.66 ng/L.For D4,it was found that the inshore concentrations of D3 and D4 in the Yellow Sea and Bohai Sea were higher than those in the far shore in every month.According to the analysis of D5 and D6,it was found that the concentration of near shore in the Yellow Sea and Bohai Sea was the same in July and August during the wet season.During the dry season in May,the concentration of D5 was higher than that of D6 in other areas except the offshore area of Bohai Sea.In the middle of October during the dry season,the concentration of cVMSs in the near shore of Huang Hai and the Bohai Sea was lower than that of D6,while the concentration of D5 in the offshore of Bohai Sea is contrary to that of the near shore of Bohai Sea.It is concluded that the main source of D4 in the waters around Liaodong Peninsula is continental.In the waters around Liaodong Peninsula,the main sources of D5 and D6 are land in the wet season and coexisting with the land in the dry season.The intensity of land pollution in the Bohai Sea was greater than that in the sea in May,and the intensity of pollution in the sea in October is greater than that of the land.In the study of the source of cVMSs in Dalian and its surrounding waters,the average concentrations of effluent from Dalian and sewage treatment plants were compared with those of D3,D4,D5 and D6.The 2016 multiples were 4.97,7.75,0.2 and 0.1 respectively.And the 2017 multiples were 4.51,2.02,1.2 and 1.28 respectively.It is concluded that the main sources of D3 and D4,D5 and D6 were the same.There is no obvious change in the types of pollution sources in the last two years,and sewage treatment plants are the main sources.At the same time,correlation analysis was carried out with marine environmental factors,D3 and D4(r=0.342),D3 and chemical oxygen demand(r=0.415),D4 and chemical oxygen demand(r=0.401).The correlation between D3 and Nonionic ammonia(r=0.428)and D6 and dissolved oxygen(r=0.428)reached a significant level of 0.5%.There were negative correlations between D6 and inorganic nitrogen(r=0.359),and between D6 and chemical oxygen demand(r=-0.381),respectively.It is concluded that D3 and D4 are the same source of pollution,and through the analysis of pollutant characteristics,the possible sources are domestic sewage,farmland sewage,chemical and pharmaceutical plants,gas coking plants,and so on.The source of D6 is different from that of D3 and D4,and the main source of pollution is not related to the wastewater of chemical industry. |
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