Journal of Oceanography, Vol. 62 (No. 3), pp. 249-257, 2006
Masahiro Narukawa1*, Masahiro Sakata2, Kohji Marumoto3 and Kazuo Asakura4
1Solar-Terrestrial Environment Laboratory, Nagoya University, Honohara, Toyokawa, Aichi 442-8507, Japan
2Institute for Environmental Sciences, University of Shizuoka, Yada, Suruga, Shizuoka, Shizuoka 422-8526, Japan
3National Institute for Minamata Disease, Hama, Minamata, Kumamoto 867-0008, Japan
4Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), Abiko, Abiko, Chiba 270-1194, Japan
(Received 9 August 2005; in revised form 7 December 2005; accepted 16 December 2005)
Abstract: In Tokyo Bay the concentrations of dissolved gaseous mercury (DGM) in the surface seawater and total gaseous mercury (TGM) over the sea were measured during December 2003, October 2004 and January 2005. Based on these data, the evasional fluxes of mercury from the sea surface were estimated using a gas exchange model. In addition, an automatic wet and dry deposition sampler was used to measure the wet and dry depositional fluxes of mercury from December 2003 to November 2004 at three locations in and near Tokyo Bay. The results indicate that the average DGM and TGM levels of seven locations are 52 ± 26 ng m-3 and 1.9 ± 0.6 ng m-3, respectively, which shows that the surface seawater in Tokyo Bay is supersaturated with gaseous mercury, leading to an average mercury evasional flux of 140 ± 120 ng m-2d-1. On the other hand, the annual average wet and dry depositional fluxes of mercury at three locations were 19 ± 3 μg m-2yr-1 and 20 ± 9 μg m-2yr-1, respectively. These depositional fluxes correspond to the daily average total depositional flux of 110 ± 20 ng m-2d-1. Thus, it is suggested that in Tokyo Bay, the evasional fluxes of mercury are comparable to the depositional fluxes.