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General Session 2: Marine & estuarine biogeochemistry |
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Heavy metals from Kueishantao shallow-sea hydrothermal vents, offshore northeast Taiwan
GS2-57-S
Xue-Gang Chen, Ocean College, Zhejiang University, Zhoushan 316021, China
Mingzhen Yu* , Ocean College, Zhejiang University, Zhoushan 316021, China
Presenter Email: yumzh3@163.com
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| Shallow water hydrothermal vents are a source of heavy metals eventually leading to their accumulation in the marine organisms that manage to live under extreme environmental conditions of low pH and high heavy metal concentrations. This is especially the case at Kueishantao (KST) shallow-sea vents system offshore northeast Taiwan, where the heavy metal distribution in vent fluids and ambient seawater is still poorly understood. In this study, we investigated the submarine venting of heavy metals from KST field and its impact on ambient surface seawater. The total heavy metal concentrations in the vent fluids and vertical plumes were 1-3 orders of magnitude higher than the overlying seawater values. When compared with other typical MOR hydrothermal systems, the estimated KST end-member fluids exhibited much lower concentrations of transition metals (e.g., Fe and Mn) but comparable contents of toxic metals such as Pb and As, that may be attributed to the lower temperature of the KST reaction zone and transporting fluids. Most of the heavy metals including Fe, Mn, As, Y, and Ba in the plumes and seawater mainly originated from submarine hydrothermal venting, while Cd and Pb were largely contributed by external sources as e.g., contaminated surface waters of coastal currents. The spatial distribution of heavy metals in the surface seawater indicated that seafloor venting has an impact on the ambient seawater which exhibited significantly elevated heavy metal concentrations. The measurable influence of KST hydrothermal venting, however, was quite localized and limited to an area of less than 1 km2. The estimated annual fluxes of heavy metals emanating from the yellow KST hydrothermal vent were: 430 - 2600 kg Fe, 24 - 145 kg Mn, 5- 32 kg Ba, 10-60 kg As, 0.3-1.9 kg Cd, and 2-10 kg Pb. This study provides important data on heavy metals from a shallow-sea hydrothermal field, and it helps to better understand the environmental impact of submarine shallow hydrothermal venting. |
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