Comprehensive Screening and Environmental Fate of Chlorinated Paraffins and Their Structural Analogs in a Freshwater Lake Ecosystem.

Chlorinated paraffins (CPs) are emerging persistent organic pollutants whose large-scale production and application have led to their widespread environmental occurrence. However, the occurrence and environmental fate of CPs and their structural analogs (CPSAs) remain largely unknown in lake systems. In this study, paired water and sediment samples from Lake Taihu were comprehensively screened for CPs and CPSAs using Ph4PCl-enhanced ionization coupled with UPLC-Orbitrap-MS. A total of 139 CP congeners (28 SCCPs, 22 MCCPs, 89 LCCPs) and 217 CPSAs (14 very short-chain CPs (vSCCPs), 51 unsaturated CPs (un-CPs), and 152 oxygenated CPs (CPs-O)) were identified. CPs dominated the contamination in water (92%), while in sediments, CPs-O (48%) slightly exceeded CPs (47%), revealing a substantial and previously overlooked contribution of oxygenated derivatives. Spatial distributions were governed primarily by emission sources from surrounding industrial cities and hydrological conditions. Sediment-water partitioning was mainly determined by carbon chain length for CPs, and oxygen-containing functional groups (CP(O2)s) introduce nonlinear partitioning behavior. Although individual CP risks were low at most sites, the combined exposure (PEC/PNEC)m ratios exceeded 1 in 33.3% of water samples and one sediment sample, and the exclusion of CPSAs from current risk assessments may lead to underestimation of total risks.