Gaseous elemental mercury (Hg(0)) in the surface air over the Sea of Japan, the Sea of Okhotsk and the Kuril-Kamchatka sector of the Pacific Ocean in August–September 2017

Abstract

The northwestern Pacific Ocean including the Sea of Japan and the Sea of Okhotsk is one of the least studied regions in terms of mercury behavior and distribution in the sea-atmosphere system. In August and September 2017, we determined gaseous elemental mercury (Hg(0)) in the surface air over this water areas along a 12,000 km cruise. Concentrations varied from 1.07 to 2.74 ng m−3, with an average value of 1,68 ± 0.23 ng m−3 (N = 1853). The average concentrations for the Sea of Japan, the Sea of Okhotsk and the Kuril-Kamchatka sector of the Pacific Ocean were 1.61 ng m−3, 1.71 ng m−3 and 1.61 ng m−3, respectively. The maximum concentrations were observed in the Sea of Okhotsk during periods when air masses arrived from the southern and central Kuril Islands. We believe that the reason for that was volcanic activity. The minimum concentrations were registered in air masses arriving from the northeastern Russia and from open sea areas. In the Sea of Okhotsk we measured Hg(0) concentrations near the cyclone eye and did not register any increase due to increased turbulence. This fact contradicts the previously expressed hypothesis that a strong turbulence above the sea surface causes enhanced Hg(0) concentrations in the air. Apparently there are additional or completely different influencing factors which could provide such increase. Also we found that the diurnal Hg(0) cycle in the Sea of Japan was the opposite of the diurnal Hg(0) cycle in the Sea of Okhotsk.