INDICATION OF CHANGE IN GLOBAL AND REGIONAL TRENDS OF ATMOSPHERIC MERCURY CONCENTRATIONS

In 1992 we reported an indication of global increase of atmospheric mercury concentrations obtained from the measurements of total gaseous mercury (TGM) over the Atlantic Ocean during five ship cruises between 1977 and 1990 [Slemr and Langer, 1992]. The observed rate of concentration increase and its implications were consistent with previous measurements and the trends derived from analyses of dated peat bog and lake sediment records. To avoid uncertainties from the intermittent character of ship measurements and to obtain more detailed information about this trend, we have continuously monitored TGM concentrations at the summit of the Wank mountain (1780 m a.s.l.) near Garmisch-Parten-kirchen in southern Germany since March 1990. These measurements and the results of another cruise in 1994 indicate a significant change in the trend of global TGM concentration, with a decrease of about 22 % in the years between 1990 and 1994. This decrease is most likely the result of reduction in coal consumption and control measures taken in the OECD countries.