|  |
Program |
 |
| |
 |
Special Session 4: Biogeochemical cycling of trace elements in the ocean: GEOTRACES and beyond |
| |
|
|
Methylmercury mass budgets and its distribution characteristics in the Western Pacific Ocean: Application of excitation-emission matrix fluorescence spectroscopy
SS4-03
Seunghee Han* , Gwangju Institute of Science and Technology (GIST)
Hyunji Kim, Gwangju Institute of Science and Technology (GIST)
Presenter Email: shan@gist.ac.kr
|
| The sources of methylmercury (MeHg) in the surface and subsurface ocean remain uncertain, although MeHg accumulation in marine organisms poses serious risks to human health. Here, we report MeHg mass budgets for the Western Pacific Ocean estimated based on cruise observations. The major net source of MeHg in surface water was estimated to be a vertical diffusion from the subsurface layer (1.8 to 12 nmol m-2 yr-1). A higher upward diffusion in the North Pacific (12 nmol m-2 yr-1) than in the Equatorial Pacific (1.8–5.7 nmol m-2 yr-1) seemed to cause higher surface MeHg concentrations observed in the North Pacific. Whereas we found that the surface MeHg concentrations and subsurface methylation rates were higher in the North Pacific, the slope of the linear regression line for MeHg and humic-like fluorescence dissolved organic matter (FDOMH) versus apparent oxygen utilization for the North Pacific was 0.59 and 0.38 times that of the Equatorial Pacific, respectively. This could be explained by an enhanced organic matter remineralization rate in the Equatorial Pacific, associated with redistribution of surface water in the tropical convergence zone. A positive correlation observed between FDOMH and MeHg suggests the applicability of excitation-emission fluorescence spectroscopy for characterizing MeHg dynamics in ocean water. |
|
|
|
|