Journal of Oceanography, Vol. 62 (No. 4), pp. 473-480, 2006
Gui-Peng Yang1,2*, Shizuo Tsunogai1 and Shuichi Watanabe3
1Laboratory of Marine and Atmospheric Geochemistry, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan
2Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266003, China
3Mutsu Institute for Oceanography, Japan Agency for Marine-Earth Science and Technology, Sekine, Mutsu 035-0022, Japan
(Received 25 July 2005; in revised form 27 January 2006; accepted 30 January 2006)
Abstract: The tendency of dimethylsulfide (DMS) to form complexes with heavy metal ions in aqueous solutions and the factors that influence it have been investigated. Among five heavy metal ions examined (Cu2+, Cd2+, Zn2+, Pb2+ and Hg2+), only Hg2+ bound significantly with DMS in aqueous solutions in which Hg2+ concentration was increased to much higher levels than that of natural seawater. The complexation capacity of Hg2+ for DMS was influenced by pH and media. The affinity of Hg2+ for DMS was generally lower at high than at low pH, presumably due to the competition of hydroxide ion to form hydroxomercury species. In different solutions, the affinity of Hg2+ for DMS followed the following sequence: ultra-purified water > 35 NaCl solution > seawater. It seems apparent that chloride had a negative impact on the complexation of DMS by Hg2+, owing to the competition of chloride with DMS for complexing Hg2+. In addition, the affinity of Hg2+ for DMS in the bulk seawater appeared to be higher than that in the surface microlayer seawater. The tendency of Hg2+ to form complexes with DMS in aqueous solution can be reduced by the presence of 2 mM amino-acid such as glycine, alanine, serine and cysteine, as these ligands give stable mercury complexes. However, the presence of 2 mM acetate in experimental solutions had no significant effect on the complexation of Hg2+ with DMS, even though this ligand has a relatively strong complexing capacity for Hg2+. Although mercury ions appeared to have a strong affinity for DMS, the concentration of mercury in seawater is too low to produce a great effect on the distribution of DMS in oceans.