SPM control on the partitioning and balance of ~(210)Po and ~(210)Pb in high-turbidity surface waters of the East China Sea

摘要

Po-210 and Pb-210 are well-known tracer pairs for some biomass and chemical processes in the marine system. In this study, Po-210 and Pb-210 were analyzed in surface seawater collected from the East China Sea (ECS), in atmospheric deposition, and in riverine input water collected along the ECS coast. The atmospheric fallouts of P-210 and Pb-210 were higher in the dry season, due to the arrival of storm dust from the northwestern region of China. In the riverine input water, the particulate Po-210 and Pb-210 dominated (corresponding to 33-94% and 50-92% of the total, respectively), especially during the flood season. In the surface seawaters, the percentage of particulate Po-210 (17-85%) was generally greater than that of Pb-210 (10-76%). Additionally, in the Changjiang Estuary, log K-d(Po) and log K-d(Pb) were negatively correlated with log suspended particulate matter (SPM) (R = 0.71, P = 0.013 for Po, R = 0.67, P = 0.019 for Pb). Pb-210 showed a stronger "particle effect" than 210 Po when SPM 1.00 mg L-1, and vice versa when SPM 1.00 mg L-1. The deficit of Po-210 relative to Pb-210 gradually decreased from the Changjiang Diluted Water, to the Shelf Merged Water and the Taiwan Warm Current Water. The mass balance of Po-210 and Pb-210 in the water column of the estuary indicated that the Changjiang River was the dominating input source (providing 91% and 88% of the Po-210 and Pb-210, respectively); meanwhile, the shelf export was the dominating output source (accounting for 68% and 78% of the Po-210 and Pb-210, respectively).