Distribution of mercury over the Atlantic Ocean in 1996 and 1999–2001

A series of measurements of total gaseous mercury (TGM) made over the Atlantic Ocean in 1977–1980, 1990, and 1994 has been continued by measurements made on board the research vessel (RV) Polarstern during three cruises: from Bremerhaven to Punta Quilla (October–November 1996), Bremerhaven–Cape Town–Antarctica–Cape Town (December 1999–March 2000), and Antarctica–Punta Arenas (February 2001). The data from these cruises are presented and compared with the data from previous cruises. In both hemispheres the average and median TGM concentrations in 1996 and 2000 were comparable to those measured in 1977–1980 but substantially lower than those observed in 1990. TGM measurements on board ships proved to provide a valuable complementary information to measurements by a ground based monitoring network since they show a large-scale distribution and can provide information about sources of mercury and its long-range transport in areas not covered by the present monitoring network.