Lead and mercury in aerosol particles collected over the South Pole during ISCAT-2000

As part of the ISCAT-2000 field study, aerosol particle samples were collected over 24 hr intervals at the South Pole (SP), and they were analyzed for trace elements and for selected ions important for Antarctic sulfur and nitrogen chemistry. This paper focuses on lead and mercury while a companion paper in this issue presents the results of the aerosol ion studies. The results showed that most trace metals were below their limits of detection. Two that were not were Pb and Hg. Lead was only quantified in 15 of 53 samples, and based on those data, the mean concentration of Pb would be <0.032 ng m−3. This is substantially lower than the aerosol Pb concentrations reported for the SP in the early to mid-1970s, suggesting that the decrease may be related to controls on pollution emissions; however, contamination of the earlier samples also would explain the difference. The arithmetic mean concentration of filterable Hg was 0.04 ng m−3; thus approaching levels reported for the Arctic. In contrast to the Arctic, however, filterable Hg at the SP was not associated with low ozone mixing ratios; rather the reactions driving the cycling of Hg at the SP appear to involve HOx radicals, reactive nitrogen, and more than likely other substances through complex and not fully understood pathways.