Occurrence, sources, partitioning and ecological risk of short- and medium-chain chlorinated paraffins in river water and sediments in Shanghai

Highlights: • SCCPs and MCCPs in water and sediments came from different sources. • CPs in water and sediments were not influenced by DOC and TOC. • Partition coefficients of SCCPs and MCCPs were calculated for the first time. • Log K_oc exhibited a second-order polynomial relationship with molecular weight. • MCCPs in water were the major ecological risk drivers for aquatic life. -- Abstract: The characteristics of regional environmental pollution of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in river system from Shanghai were comprehensively investigated in this study for the first time. The total concentrations of SCCPs and MCCPs ranged from 15.0 to 1640 ng L⁻¹ (median: 278 ng L⁻¹) and 40.3 to 3870 ng L⁻¹ (median: 939 ng L⁻¹) in water, and from not detected (ND) to 2020 ng g⁻¹ (median: 89.3 ng g⁻¹) and 10.1 to 10,800 ng g⁻¹ (median: 947 ng g⁻¹) in sediments, respectively. The higher levels of SCCPs and MCCPs were found in water from Jinhui and Yexie rivers, and in sediments from Huangpu River, respectively. The concentrations of MCCPs were higher than those of SCCPs in both water and sediments, suggesting that the river system was mainly contaminated by MCCPs. Compared with other areas around the world, the concentrations of SCCPs and MCCPs were at medium to high levels in water and sediments. Factor analysis results revealed that SCCPs and MCCPs had different sources in both water and sediments. The log K_oc values of CPs were significantly correlated with carbon chain lengths (p < 0.01), but not with chlorine number for both SCCPs and MCCPs (p > 0.05). A significant second-order polynomial relationship was observed between log K_oc values and molecular weights of homologue groups of SCCPs (p < 0.001) and MCCPs (p < 0.01), respectively. SCCPs in water posed a low ecological risk at all sampling sites, and MCCPs in water posed a moderate ecological risk to aquatic life at nearly a fifth of sampling sites. SCCPs and MCCPs in sediments posed a low ecological risk to sediment dwelling organisms at most sampling sites.