Anomalous mercury in near-bottom water of a Mid-Atlantic Rift valley

Abstract

MERCURY analysis¹ of over 1,000 water samples from GEOSECS stations in the western Atlantic indicated extremely low mercury concentrations (2–40 ng 1⁻¹) in much of the ocean between 15°N and 35°S, and identified a large core of water of relatively high concentration (80–400 ng 1⁻¹) between 25°N and 50°N. These increased concentrations may result¹ from the entrainment of Hg which diffuses from the active spreading centre of the Mid-Atlantic Ridge, by Mediterranean water which flows over the ridge into the western basin of the Atlantic Ocean. Mercury concentrations are as high as 1,370 ng 1⁻¹ at a depth of 2,435 m at GEOSECS station 27 (42°00′N, 41°59′W), (ref. 1).