Distribution, behavior and budget of Pb in suspended particles in the Changjiang Estuary and adjacent east China sea

Abstract

Content, isotopes and budget of Pb in suspended particulate matter (SPM) in the Changjiang Estuary and adjacent East China Sea (ECS) were determined to investigate the biogeochemical cycling of particulate Pb in coastal sea. The content of particulate Pb ranged from 11.3 to 669.4 μg/g in February (winter) and from 20.1 to 79.4 μg/g in August (summer). Except in surface water, particulate Pb content in August is higher than that in February. In lower water, particulate Pb and Th and SPM all decreased gradually from the estuary towards the sea, indicating their lithogenic origin from the Changjiang River. Particulate Pb displayed abnormally high concentration in February surface water, resulting from the atmospheric deposition of anthropogenic Pb in winter. 208Pb/206Pb and 207Pb/206Pb in surface water north to the estuary were higher than background values, suggesting anthropogenic disturbance of Pb. Particulate Pb content in the Changjiang River and the estuary had increased by 77–78% from the 1980s to 2016 due to pollution. Pb was also scavenged by organic matter, leading to higher Pb content in waters with high productivity. Budget of particulate Pb in the northern ECS was established. The Changjiang River contributed 97.0% and 58.1% of particulate Pb input in summer and winter half year, respectively. 88.8% of particulate Pb was deposited in the estuary and adjacent coastal sea in summer but 88.7% was exported with southward coastal currents in winter.