Decoding historical and emerging environmental concerns of C₆₋₃₆ chlorinated paraffins: Insights from marine sediment cores in the Pearl River Estuary

Chlorinated paraffins (CPs) readily deposit in sediments upon entering estuaries and adjacent seas. Time-series investigations are indispensable for the long-term monitoring of historical releases and identifying CPs of emerging concerns in the marine environment. In this study, short-, medium-, and long-chain CPs (SCCPs, MCCPs, and LCCPs) were investigated using time-of-flight high-resolution mass spectrometry (ToF-HRMS) in sediment cores, dated between the 1920s and the 2010s sampled from Hong Kong waters and Lingdingyang of the Pearl River Estuary (PRE), South China. Levels of SCCPs remained steady since the 1980s, while increasing trends of MCCPs and LCCPs were observed, indicating a market supply shift from SCCPs to MCCPs and LCCPs, potentially influenced by global restrictions. This is the first study to report C₁₈₋₃₁ CPs in Chinese marine sediments. C_>20 very long-chain CPs (C_>20 vLCCPs) subcategorized from LCCPs were semi-quantified via ToF-HRMS and positively correlated with those of other CP categories, implying their synchronized release in the investigated regions. C_>20 vLCCPs, contributing an average of 27% of total CP concentrations in two cores, were found at higher levels than LCCPs (7%). Hence, the risk of C_>20 vLCCP contamination should not be ignored. By highlighting the temporal variations in the world's largest producer and consumer of CPs, the present study augments the database of the continuous deposition of SCCPs and MCCPs in marine sediments in the PRE and highlights the unrecognized risks of LCCP contaminations.