Occurrence and risk of emerging short- and medium-chained chlorinated paraffins in the aquatic environment of a typical shallow lake and its inflow river estuaries in China.

Short-chained chlorinated paraffins (SCCPs) and medium-chained chlorinated paraffins (MCCPs) have recently garnered significant attention due to their persistence, toxicity, and potential for bioaccumulation. In this study, we comprehensively investigate the occurrence, spatiotemporal variability, congener profiles, potential sources, and ecological risks of SCCPs and MCCPs in the aquatic environment of a typical shallow lake (Nansi Lake) severely affected by industrial development and the estuaries of its inflowing rivers. A total of 90 water and sediment samples were collected across both wet and dry seasons from the lake and surrounding estuaries. The analytical results revealed that the mean concentrations of total SCCPs and MCCPs in water samples varied between 7.38 and 518.37 ng/L (mean: 51.15 ng/L) and 2.61-106.58 ng/L (mean: 18.78 ng/L), respectively. The concentrations of SCCP and MCCP in water were obviously higher during the dry season than during the wet season. Additionally, the levels of SCCPs and MCCPs in the sediments ranged from 60.12 to 1219.17 ng/g (mean: 465.62 ng/g) and 252.32-1819.14 ng/g (mean: 779.23 ng/g), respectively. These levels were found to be moderate to elevated when compared with concentrations observed in other rivers and lakes globally. Spatial distribution patterns of SCCPs and MCCPs in water were consistent across both seasons. The use of chlorinated paraffins (CPs) and riverine transport may be the most likely primary contributors. The Log K values for SCCPs and MCCPs exhibited a positive correlation with carbon chain length, while a negative correlation with chlorine content was also observed. Preliminary ecological risk assessments indicated that SCCPs and MCCPs pose a low level of ecological risk within the Nansi Lake watershed.