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Abstract
The particulate heavy metal concentrations of Tl, Cu, Cd, Pb, Zn, Ni, Cr, and Fe were determined in the atmosphere over the Atlantic Ocean from 77°S (Antarctica) to 54°N (Europe) using the analytical method of isotope dilution mass spectrometry. The samples were collected on board of the German polar research vessel “Polarstern” during four different expedition legs from September 1987 to March 1990. Analyses of the crustal reference element Fe resulted in the calculation of enrichment factors EF(Fe), which were used for interpretation of crustal influences on heavy metal contents as well as for contamination control. The variations in concentration of the dominant crust element Fe run up to five orders of magnitude (0.22–36200 ng m−3). The region between the equator and 20°N was strongly influenced by crustal material transported by the north-eastern trades out of the Sahara. EF(Fe) values around unity and the highest measured concentrations of the dominant crustal elements Fe (36200 ng m−3), Cr (50.6 ng m−3), and Ni (33.7 ng m−3) were found in this area. The mainly anthropogenic elements Cd, Pb, and Zn reached their maximum concentration approaching the European Continent in the English Channel: Cd (1.3 ng m−3), Pb (61.6 ng m−3), Zn (115.9 ng m−3). Elements like Tl and Cu had their highest concentration in the area influenced by Saharan mineral dust (Tl = 96.6 pg m−3, Cu = 9.9 ng m−3) as well as near the highly industrialized European Continent (Tl = 212 pg m−3; Cu = 11.1 ng m−3). A difference in contents between the South Atlantic and the North Atlantic was registered as roughly one order of magnitude for Tl, Cd and Pb. Data from former expeditions were in good agreement with respect to the corresponding meteorological and local conditions. The absolutely lowest concentrations of <0.2–4 pg m−3 were measured for Tl in the remote Antarctic region. The contents of the other trace elements in Antarctica were determined to be: Cu = <0.03–0.3 ng m−3, Cd = 0.005–0.5 ng m−3, Pb = 0.07–0.9 ng m−3, Zn = < 1–21 ng m−3, Ni = <0.03–0.06 ng m−3, Cr = <0.04–0.1 ng m−3, and Fe = 0.2–9 ng m−3. The high EF(Fe) values of Zn = 240–16000, of Pb = 230–1800 and especially of Cd = 800–90000 suggest that other sources than crustal material are responsible for the measured contents in this area, e.g. biogenic emissions.