Distributions, transports and fates of short- and medium-chain chlorinated paraffins in a typical river-estuary system

Chlorinated paraffins (CPs) are widely employed in a variety of domestic and industrial products, and are ubiquitously detected in the environment. Short-chain chlorinated paraffins (SCCPs) have been listed in the Stockholm Convention as persistent organic pollutants (POPs), but not medium-chain chlorinated paraffins (MCCPs), even though they exhibit physicochemical properties and environmental behaviors similar to SCCPs. However, very limited data are available regarding their environmental behaviors and fates in river-estuary systems. China is the major producer of chlorinated paraffins (CPs), and Shandong Province is the main producer of CPs in China. Here, we investigated the distribution, transport, and fate of SCCPs and MCCPs in a heavily polluted river in Shandong Province, aiming to explore the distributions of CPs between dissolved and particulate phases, and between water and sediment phases, as well as the transport of CPs from river headwaters to estuaries and the roles of the estuarine turbidity maximum zone (ETM) on the fate of CPs. CP concentrations in sediments were 9.1–16,000 ng/g dw (mean value: 1000 ng/g dw) for SCCPs and 2.4–27,000 ng/g dw (mean value: 4400 ng/g dw) for MCCPs. In the water column, CP concentrations were 7.4–470 ng/L for SCCPs (mean value: 43 ng/L) and 4.0–120 ng/L for MCCPs (mean value: 27 ng/L). CP concentrations in riverine sediments were among the highest worldwide. SCCPs accounted for 95% of CPs (sum of SCCPs and MCCPs) in the dissolved phase. Cities around the river basin were found to be important pollution sources for CPs. Long-chained and more chlorinated congeners with larger LogKow values might be more likely to be ‘salted-out’, and thus, will be sequestrated in sediments in the ETM, while those lighter congener groups with relatively high water solubility were prone to be transported by water flow to larger distances.