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Perfluoroalkyl substances (PFASs) have been found in environment globally. However, studies on PFAS occurrence in sediments of lakes or reservoirs remain relatively scarce. In this study, two hundred and sixty-two surface sediment samples were collected from forty-eight lakes and two reservoirs all over China. Average PFAS concentrations in surface sediments from each lake or reservoir varied from 0.086 ng/g dw to 5.79 ng/g dw with an average of 1.15 ng/g dw. Among five lake regions, average PFAS concentrations for the lakes from Eastern Plain Region were the highest. Perfluorooctanoic acid, perfluoroundecanoic acid and perfluorooctane sulfonic acid (PFOS) were the predominant PFASs in surface sediments. The significant positive correlations between PFAS concentrations and total organic carbon, total nitrogen and total phosphorus contents in sediments revealed the influences of sedimentary characteristics on PFAS occurrence. A two-dimensional hierarchical cluster analysis heat map was depicted to analyze the possible origins of sediments and individual PFAS. The food-packaging, textile, electroplating, firefighting and semiconductor industry emission sources and the precious metals and coating industry emission sources were identified as the main sources by two receptor models, with contributions of 77.7 and 22.3% to the total concentrations of C4-C14- perfluoroalkyl carboxylic acids and PFOS, respectively.

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In this study, the sediment profiles of total phosphorus (TP), inorganic phosphorus (P i ), organic phosphorus (P o ), C/P and N/P were used to investigate time-dependent P distribution changes in Lake Chaohu. The characteristics of P i and P o fractions in the surface sediments were studied and the difference between east and west lake region was also discussed. The P i and P o contents displayed a clear gradient from east to west in sediments of Lake Chaohu, and the P o /P ratios were lower in sediments with industrial and urban pollution sources input in west lake region. The study indicated that different sediments area had diverse concentrations and distributions of P o fractions due to their different drainage basin and pollution sources. The profile distribution of the C/P and N/P ratios decreased with increasing depths and stayed relatively constant ratios at the depths of 15-30 cm. The C/P and N/P ratios were always below Redfield ratios in sediment profile, indicating P enrichment but likely due to the preferential loss of carbon in respect to phosphorus. The rank order of P i -fractions extracted was HCl-P i [ NaOH-P i [ NaHCO 3 -P i in surface sediments. The relative distribution of NaHCO 3 -P i and HCl-P i was in agreement with the trophic conditions of the regions studied. Among the sequentially extracted P o forms, the rank order of P o fractions was residual P o [ HCl-P o [ fulvic acid-P [ humic acid-P [ NaHCO 3 -P o , with mean relative proportion of 5.4:3.4:2.2:1.1:1.0.

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