Trends in Atmospheric Mercury Concentrations over the Atlantic Ocean and at the Wank Summit, and the Resulting Constraints on the Budget of Atmospheric Mercury

In 1977 – 1980, 1990, and 1994 we measured the latitudinal distribution of atmospheric mercury over the Atlantic Ocean. The results of these measurements show a pronounced concentration gradient between the northern and southern hemispheres and a rather small variability of mercury concentrations within the hemispheres, especially within the southern hemisphere. The measurements made during the cruises also suggest globally increasing atmospheric mercury concentrations by 17.5% in the northern and 14.0% in the southern hemispheres between 1977 – 1980 and 1990 to concentrations of 2.25 ng Hg m3 in the northern and 1.50 ng Hg nr3 in the southern hemispheres in 1990 and a global decrease between 1990 and 1994. The decrease between 1990 and 1994 of 20.4% in the northern and 21.2% in the southern hemispheres is consistent with the decrease of 23.3% observed in the same period at the Wank summit (1780 m a.s.l) in southern Germany. The results of all these measurements are reviewed. From these results and from measurements reported by others, we derive several constraints on the budget of atmospheric mercury, its atmospheric burden, residence time, sources, and sinks.