The distribution and speciation of mercury in the South and equatorial Atlantic

Mercury concentration and speciation were measured in surface and deep ocean waters of the South and equatorial Atlantic. In the surface waters, total Hg was 2.9±1.7 pM on average, with a significant fraction present as reactive Hg (1.7±1.2 pM). The reactive Hg fraction consisted of elemental Hg (Hg°) as the dominant species (1.2±0.8 pM). Measurements in surface waters also showed that Hg partitioned to the “colloidal” phase (0.33±0.28 pM) and was associated with particulate matter (0.1±0.05 pM). No dimethylmercury (DMHg;