Air-sea exchange of gaseous mercury in the East China Sea

• Published in: Environmental pollution (1987) 2016-05, Vol.212, p.535-543
• Main Authors: Wang, Chunjie, Ci, Zhijia, Wang, Zhangwei, Zhang, Xiaoshan
• Format: Article
• Language: English
• Subjects: Air Pollutants - chemistry; Air-sea exchange; China; Dissolved gaseous mercury; East China Sea; Environmental Monitoring; Environmental Pollutants - chemistry; Fluorescence; Gaseous elemental mercury; Gases - chemistry; Marine; Mercury - chemistry; Oceans and Seas; Seasons; Seawater - chemistry
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2016.03.016

Two oceanographic cruises were carried out in the East China Sea (ECS) during the summer and fall of 2013. The main objectives of this study are to identify the spatial-temporal distributions of gaseous elemental mercury (GEM) in air and dissolved gaseous mercury (DGM) in surface seawater, and then to estimate the Hg0 flux. The GEM concentration was lower in summer (1.61 ± 0.32 ng m−3) than in fall (2.20 ± 0.58 ng m−3). The back-trajectory analysis revealed that the air masses with high GEM levels during fall largely originated from the land, while the air masses with low GEM levels during summer primarily originated from ocean. The spatial distribution patterns of total Hg (THg), fluorescence, and turbidity were consistent with the pattern of DGM with high levels in the nearshore area and low levels in the open sea. Additionally, the levels of percentage of DGM to THg (%DGM) were higher in the open sea than in the nearshore area, which was consistent with the previous studies. The THg concentration in fall was higher (1.47 ± 0.51 ng l−1) than those of other open oceans. The DGM concentration (60.1 ± 17.6 pg l−1) and Hg0 flux (4.6 ± 3.6 ng m−2 h−1) in summer were higher than those in fall (DGM: 49.6 ± 12.5 pg l−1 and Hg0 flux: 3.6 ± 2.8 ng m−2 h−1). The emission flux of Hg0 from the ECS was estimated to be 27.6 tons yr−1, accounting for ∼0.98% of the global Hg oceanic evasion though the ECS only accounts for ∼0.21% of global ocean area, indicating that the ECS plays an important role in the oceanic Hg cycle. •Hg0 in air and surface seawater were determined in the East China Sea.•The levels of GEM, DGM, and THg were higher in coastal area than in the open sea.•Flux of Hg0 in the East China Sea was higher than those of other open oceans.•The DGM was positively correlated with THg, solar radiation, and water fluorescence. The GEM, DGM and THg levels in the nearshore area were higher than those in the open sea, and the estimated Hg0 flux in the ECS was higher than the average Hg0 flux of global oceans.