Concentrations and sources of aerosol ions and trace elements during ANTCI-2003

As part of the Antarctic Tropospheric Chemistry Investigation (ANTCI), bulk aerosol-particle samples collected at the South Pole were analyzed for nitrate, sulfate, methanesulfonate (MSA), selected trace elements and radionuclides. The samples were collected in the same manner as in the Investigation of Sulfur Chemistry in the Antarctic Troposphere (ISCAT) campaigns of 1998 and 2000. The ANTCI mean sulfate (124 ng m−3) and MSA (9.1 ng m−3) concentrations were comparable to those during ISCAT, but high MSA and sodium and high MSA/sulfate in late November/early December indicated pervasive maritime influences during that time. Trajectory analyses indicate that the Weddell Sea and the Southern Ocean near Wilkes Land were probable sources for the ocean-derived sulfate. The transport of marine air occurs mainly in the buffer layer or free troposphere, and the rapid oxidation of biogenic sulfur to SO2 appears to be the basis for the observed low MSA/sulfate ratios. Elements typically associated with mineral dust (Al, Fe, K) and other elements with continental sources (Pb, Sb, Zn) had higher concentrations during ANTCI than ISCAT. The mean filterable nitrate (f-NO3−) concentration (280 ng m−3) also was conspicuously higher than during ISCAT (39 and 150 ng m−3). Several peaks in f-NO3− were synchronous with those for MSA and sulfate, but some samples had high f-NO3− but neither high MSA nor sulfate. While there is some evidence that nitrate or nitric acid is transported to SP from distant sources, local emissions of nitrogen oxides from the snow are a far more important source overall.