Distribution Characteristics Of Per-and Polyfluoroalkyl Substances In The Yangtze River Estuary And Coastal Waters

Per-and polyfluoroalkyl substances(PFAS)are a type of synthetic organic pollutants that are widely used in production and daily life because of their unique physical and chemical properties.Currently,PFAS have been detected in various environmental media such as the atmosphere,water bodies,sediment,and biota worldwide,and some monosubstances can be magnified through the food chain,posing great risks to ecosystems and human health,and attracting international attention.With the addition of PFOS and PFOA to the Stockholm Convention,the production and use of short-chain PFAS and new types of PFAS are gradually expanding,and they are continuously being detected in the environment,becoming a new research hotspot.This study used solid-phase extraction combined with ultra-high-performance liquid chromatography-tandem triple quadrupole mass spectrometry(UHPLC-MS/MS)and high-resolution mass spectrometry combined with non-target analysis technology to analyze the pollution characteristics of 32 PFAS in the Yellow Sea,East China Sea,Yangtze River Estuary,and nearby waters.The work was divided into three parts: 1)quantitative analysis of new and traditional PFAS in seawater,revealing the pollution characteristics of PFAS,and elucidating the distribution behavior and spatial distribution of PFAS in the Yellow Sea,East China Sea,and Yangtze River Estuary.2)Analysis of the impact of the Yangtze River Estuary on nearby PFAS in surface seawater,source analysis,clarification of the sources and migration behavior of PFAS in estuaries and nearshore areas,and estimation of the input flux of the Yangtze River Estuary to the East China Sea.3)Identification of non-target PFAS in surface water of the Yangtze River Estuary.The specific conclusions are as follows:1)The level of PFAS contamination in seawater is higher in the Yellow Sea than in the East China Sea.The main pollutants in the Yellow Sea are PFOA,PFHp A,HFPO-TA,and PFHx A,while in the East China Sea,the main pollutants are PFOA,PFHx A,PFHp A,PFBA,and HFPO-TA.The study results show that PFAS with carbon chain lengths below9 are more easily transported by seawater.Novel PFAS were detected in surface seawater in both the Yellow Sea and the East China Sea at different concentrations,with FBSA,HFPO-DA,and HFPO-TA having higher detection rates in surface seawater.Surface seawater may be an important long-term sink for FBSA,HFPO-DA,HFPO-TA,and other PFAS with carbon chain lengths below 9.There were significant differences in the levels and composition of SPM PFAS in surface seawater in the northern and southern parts of the Yellow Sea,with higher concentrations in the northern part,mainly of HFPO-TA,with pollution mainly coming from the fluorine chemical park in Shandong province.In the southern part,the main pollutants were PFOA and HFPO-TA,with pollution mainly coming from coastal fluorine chemical enterprises in Jiangsu province.Temperature and salinity changes in seawater with depth have different effects on PFAS.Studies have shown that PFCAs are more easily transported into seawater.As the sampling depth increases,the total concentration of PFAS decreases slightly,and the composition of PFAS changes,with a decrease in the proportion of PFOA,a slight increase in the proportion of PFPe A,and fluctuations in the proportion of PFBA.Therefore,PFBA and PFPe A have higher solubility and vertical ocean turbulence and are more easily vertically transported.2)The total concentration of PFAS in surface seawater samples from the Yangtze River estuary and the northwest part of the East China Sea ranged from 1.19 to 26.41ng/L,with a mean of 9.73 ng/L and a median of 9.63 ng/L,indicating that the Yangtze River estuary is a significant source of PFAS pollution in the northwest part of the East China Sea.The water in the Yangtze River estuary is affected by wastewater from the Changshu fluorine chemical park upstream and Shanghai Pudong Airport.Investigation of the seawater around the Zhoushan Archipelago in the northwest of the East China Sea showed that the airport and port on Putuo Island in Zhoushan would cause PFAS pollution in the surrounding waters,with PFBA being a prominent pollutant.Due to the influence of coastal currents,PFAS-contaminated seawater in this area is transported to the southern waters,with less impact on the waters in the eastern region.6:2 Cl-PFESA can be detected in the water of the Yangtze River estuary,which is due to the influence of the Changshu fluorine chemical park upstream and the sewage treatment plant in Bailong Port on the south bank.Pudong Airport discharges 9.1 tons of PFAS into the Yangtze River estuary every year,accounting for 58%of the total amount of PFAS discharged into the East China Sea from the Yangtze River estuary annually.Compared with the estimated PFAS flux in the Yangtze River estuary in 2016,the PFAS flux in the Yangtze River estuary decreased by 50%in 2019.3)Non-target analysis techniques were used to analyze high-resolution mass spectra,which ultimately led to the discovery of 21 PFAS compounds in the surface water of the Yangtze River estuary that were not detected by the quantitative method.This suggests that factories and enterprises are looking for alternative PFAS substances and using them in production.However,research on these alternative substances is limited,and their physical and chemical properties,migration characteristics,and biological toxicity are unclear,indicating a need for further research in the future.By comparing the PFAS pollution levels and composition differences in the Yellow Sea,East China Sea,and Yangtze River estuary,it was found that different PFAS pollution sources have different impacts on their surrounding environmental media,and the properties of the compounds and hydrological conditions of different regions also affect the impact of PFAS.Research indicates that land-based pollution sources can cause PFAS pollution in the nearshore areas through rivers,and non-target analysis can identify 21non-targeted PFAS compounds in the water of the Yangtze River estuary.Therefore,in future studies on the distribution,allocation,migration,and transformation of PFAS in water environments,factors such as point source characteristics,compound properties,and hydrology in different regions should be considered.This will provide a more comprehensive and detailed analysis of PFAS in the environment.