Pollution Characteristics and Risk Assessment of Chlorinated Paraffins in Seawater and Kelp from Kelp Mariculture Areas of the Shandong Peninsula

Chlorinated paraffins (CPs) are persistent, bioaccumulative, and toxic. In marine environments, most studies have focused on short-chain CPs (SCCPs) in animals, while medium-and long-chain CPs (MCCPs and LCCPs) in plants have been neglected. In this study, samples collected from kelp mariculture zones in different seasons were analyzed for the CPs' contamination characteristics and spatiotemporal distributions in seawater and contamination profiles, bioaccumulation behavior, and dietary exposure risks in kelp. In seawater, the total concentration ranges of SCCPs, MCCPs, and LCCPs were 25.44-245.75, 8.24-27.19, and not detected at 3.26 ng/L, respectively. Spatially, the CP concentrations were influenced by industrial discharge, riverine inputs, and dilution effects, and were significantly higher in nearshore water than in offshore areas (<i>p</i> < 0.05). The concentrations were significantly higher in February than in May, which was attributed to emissions from winter heating and reduced vessel activity during a fishing moratorium. In kelp, the total concentration ranges of SCCPs, MCCPs, and LCCPs were 5.4-210.9, 0.007-0.87, and 0.0-4.45 ng/g wet weight, respectively. Kelp exhibited significant growth-stage-dependent bioaccumulation of CPs, with higher CP concentrations and bioaccumulation factors in its tender stage (February) than during its mature stage (May). Congener analysis revealed similar composition patterns between seawater and kelp. According to a dietary risk assessment (hazard quotient < 0.01), the potential health risks associated with kelp consumption are low.