| Environment problems caused by perfluoroalkyl substances(PFASs) have attached great importance and extensive attention of international organizations and scientific researchers. A majority of PFASs are released to surface waters in the process of PFAS production, use and disposal. PFASs in the environment are mainly buried in sediments or transported into Deep Ocean. However, studies on PFASs in sediments are rather limited. This paper has investigated the pollution statuses, spatial distribution differences, historical deposition behaviors and pollution sources of PFASs in nationwide lake sediments by ultra-high performance liquid chromatography tandem mass spectrometry, using solid phase extraction, isotope dating and multivariate statistical methods. The main conclusions are summarized as follows:(1) The average PFAS concentrations in surface sediments from Eastern Plain lake region were 3.0-6.3 times higher than those from Northeastern Plain lake region, Yunnan-Guizhou Plateau lake region, Qinghai-Tibet Plateau lake region and Mongolia-Xinjiang Plateau lake region. The average PFAS concentrations in surface sediments have increased about 5.3 times along the flow direction of Yangtze River, untouched by the dilution effect of the water current.(2) Compared with other provinces, average PFAS concentrations in surface sediments were extremely higher from the lakes in Jiangsu Province. Pearson correlation analysis showed that C8 and C10-C14-perfluoroalkyl carboxylic acids(PFCAs), perfluorooctane sulfonic acid(PFOS) and the ∑12PFASs concentrations had significantly positive correlations with gross domestic product and the total sewage amount of the provinces and municipalities.(3) The ∑12PFASs were significantly and positively correlated with total organic carbon(TOC) in surface sediments from Eastern Plain lake region(Pearson correlation,r = 0.765,p = 0.000). PFASs in surface sediments from Jiangsu Province were positively correlated with TOC, total nitrogen(TN) and total phosphorus(TP) to some extent.(4) The ΣPFASs concentrations in surface sediments of Lake Chaohu had a decreased tendency from west to east as a whole and a substantial increase adjacent to Chaohu City. Shiwuli River had the extremely highest concentrations. PFAS concentrations in sediments of Nanfei River increased slightly before reaching Hefei City, rose dramatically after flowing through the city, and subsequently decreased downstream. PFAS levels were also significantly higher in sediments of Pai River adjacent to Feixi County and decreased downstream. From Lake Wanfohu to Hangbu River, PFAS concentrations increased sevenfold.(5) The ΣPFASs in sediment core samples of Lake Chaohu had increasing trends with relatively higher levels in the upper slices than those in the bottom samples, which was synchronized with the mass production and wide use of PFASs in nearly 60 years.(6) Several PFAS congeners were significantly and positively correlated with TOC, TN, TP and heavy metals in three sediment core samples of Lake Chaohu, which mainly focused on the long-chained PFAS congeners(C9-C14). The correlation between PFOS and TOC was relatively stronger than that between PFOA and TOC. The ΣPFASs, C9-C14-ΣPFCAs, C7, C9-C13-PFCAs and PFOS were positively correlated with the percentage composition of particles sized <4 to 8 μm, conversely, negatively with particles sized 8-64 μm, median particle size and mean particle size of the sediment particles.(7) Hierarchical cluster analysis showed that two well-differentiated clusters were observed in surface sediments from 48 lakes and two reservoirs. PFOS and the long-chained PFCAs(C8-C14) were included in one group, while the short-chained PFCAs(C4-C7) were clustered into the other group. Significant positive correlations were observed among PFOS, C8-C14-PFCAs and the ∑12PFASs. There were also positive correlations between perfluoropentanoic acid and perfluorohexanoic acid, perfluorohexanoic acid and perfluoroheptanoic acid. Principal component analysis-multiple linear regression(PCA-MLR) and positive matrix factorization(PMF) models both provided good correlations between the measured and fitted PFAS concentrations with r2 values of 0.98 and 0.99(p = 0.000), respectively. Very similar slopes were detected in both cases and the intercepts did not vary greatly. The food-packaging, textile, electroplating, firefighting and semiconductor industry emission sources and the precious metal and coating industry emission sources were identified as the two main sources, with contributions of 77.7% and 22.3% to the ∑12PFASs, respectively.(8) Four conditions were considered for PCA-MLR, PMF and Unmix models: the fitting degree between the fitted and measured ∑12PFASs concentrations in a certain model, the fitting degree between the fitted ∑12PFASs concentrations among different models, the number and characteristics of identified sources as well as the contributions of each extracted source to the ∑12PFASs in lake sediments from Jiangsu Province. Results indicated that they all could well track the ∑12PFASs as well as the concentrations explained in sediments. |
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