A mass balance budget for mercury at Ocean margins is proposed on the basis of recent data on exchange fluxes with terrestrial, atmospheric and marine reservoirs. The largest single mercury flux consists of particulate species from rivers (~5 Mmol a-1), which is, primarily, unreactive and quickly buried in nearshore sediments. The most important source of mobile mercury for ocean margins is the atmosphere directly via deposition and indirectly via upwellings (total ≈ 5 Mmol a-1). The direct atmospheric input to coastal zones rivers (~2 Mmol a-1), exceeds considerably the dissolved inputs from rivers (~0.13 Mmol a-1). The evasion of elemental mercury from coastal surface waters is balanced by the mercury deposition from the atmosphere, but geographical differences exist suggesting a net mercury transfert to the higher latitudes. The overall residence time for mercury on the continental shelves is about 4 months. This is less than the mean residence time of water on the shelves (~1.3 year) and confirms the known reactivity of mercury in aquatic environments. However, two fractions of mercury are actively recycled (through the atmosphere and through the organic carbon recycling). The highly productive zones associated with frontal stuctures near the shelf edges appear to be very active in redistributing mercury species between ocean and coastal areas. One consequence is that the main source of methylmercury for coastal waters is upwelled oceanic waters.
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- Mercury Fluxes at the Ocean Margins
- Springer Netherlands