Aircraft measurements of atmospheric mercury over southern and eastern Germany

The concentration of atmospheric mercury was measured on 13 June 1996, during a level flight from Munich to Halle at an altitude of 900 m a.s.l. and back at 2500 m a.s.l. Measurements, corrected for pressure dependence of the instrument response, showed that, with the exception of the southernmost part of the return flight with higher concentrations, mercury was horizontally evenly distributed over a distance of 400 km. The total gaseous mercury (TGM) concentration at an altitude of 2500 m a.s.l. (in the free troposphere) was with 1.635 plus/minus 0.094 ng m high -3 (n = 22) slightly lower than at 900 m a.s.i. (in the mixing layer) with 1.774 plus/minus 0.101 ng m high -3 (n = 17). Higher TGM concentrations of 2.190 plus/minus 0.255 ng m high -3 (n = 2) during the southernmost part of the flight south of Munich and of 2.321 plus/minus 0.133 ng m high -3 (n = 8) at the summit of the mountain Wank was attributed to a different air mass. Substantially higher TGM concentrations were observed in the mixing layer downwind of a former chlor-alkali plant at Schkopau. From the downwind/upwind concentration difference and the prevailing wind conditions, a mercury emission of about 0.4 kg d high -1 was estimated for the plant area.