Persistent organic pollutant and sterol distributions in the offshore East China Sea influenced by the low salinity water mass

Abstract

Surface seawater was analyzed for organochlorine compounds, polycyclic aromatic hydrocarbons (PAHs), and sterols in the offshore (approximately 250 km from the shore) East China Sea influenced by low salinity water masses. The spatial distribution and molecular composition of the target chemicals were investigated to identify the origin of the low salinity water mass and the organic chemicals. ΣDDTs and ΣPCBs in suspended particulate matter (SPM) were ranging from 3.3 to 39 and from 20 to 68 pg/L respectively. ΣPAHs were ranged from 3.0 to 33.6 ng/L with an average of 12.3 ng/L. PAHs, DDTs and Chlordane were relatively higher in the less-saline water masses, suggesting the influx of the organic contaminants into the northern East China Sea by the low salinity water mass. ΣSterol concentrations ranged from 3.2 to 31.9 ng/L in the SPM. Although marine sterols dominated with 71% in the overall sterol composition, molecular signatures of allochthonous terrestrial plants were still visible and there was a relationship between the low salinity water mass in the East China Sea and the terrestrial sterols. Considering the proximity of the Yangtze River and the presence of the Changjiang River Diluted Water (CRDW) in the study area, it was probable that these chemicals were transported for long-distance from the Yangtze River runoff by the CRDW. The compositional similarity of PAHs in the less-saline water masses with thoibution and molecular composition of the target chemicals were investigated to identify the origin of the low salinity water mass and the organic chemicals. ΣDDTs and ΣPCBs in suspended particulate matter (SPM) were ranging from 3.3 to 39 and from 20 to 68 pg/L respectively. ΣPAHs were ranged from 3.0 to 33.6 ng/L with an average of 12.3 ng/L. PAHs, DDTs and Chlordane were relatively higher in the less-saline water masses, suggesting the influx of the organic contaminants into the northern East China Sea by the low salinity water mass. ΣSterol concentrations ranged from 3.2 to 31.9 ng/L in the SPM. Although marine sterols dominated with 71% in the overall sterol composition, molecular signatures of allochthonous terrestrial plants were still visible and there was a relationship between the low salinity water mass in the East China Sea and the terrestrial sterols. Considering the proximity of the Yangtze River and the presence of the Changjiang River Diluted Water (CRDW) in the study area, it was probable that these chemicals were transported for long-distance from the Yangtze River runoff by the CRDW. The compositional similarity of PAHs in the less-saline water masses with tho