Seasonal Variation of Mercury and Its Isotopes in Atmospheric Particles at the Coastal Zhongshan Station, Eastern Antarctica

Abstract

Mercury (Hg) is a globally spread trace metal due to its long atmospheric residence time. Yet, our understanding of atmospheric processes (e.g., redox reactions and deposition) driving Hg cycling is still limited, especially in polar regions. The Antarctic continent, by virtue of its remoteness, is the perfect location to investigate Hg atmospheric processes in the absence of significant local anthropogenic impact. Here, we present the first 2 year record (2016–2017) of total suspended particulate mercury (PHg) concentrations along with a year-round determination of an Hg stable isotopic composition in particles collected at Zhongshan Station (ZSS), eastern Antarctic coast. The mean PHg concentration is 21.8 ± 32.1 pg/m3, ranging from 0.9 to 195.6 pg/m3, and peaks in spring and summer. The negative mass-independent fractionation of odd Hg isotopes (odd-MIF, average −0.38 ± 0.12‰ for Δ199Hg) and the slope of Δ199Hg/Δ201Hg with 0.91 ± 0.12 suggest that the springtime isotope variation of PHg is likely caused by in situ photo-oxidation and reduction reactions. On the other hand, the increase of PHg concentrations and the observed odd-MIF values in summer are attributed to the transport by katabatic winds of divalent species derived from the oxidation of elemental Hg in the inland Antarctic Plateau.

Katabatic Wind and Sea–Ice Dynamics Drive Isotopic Variations of Total Gaseous Mercury on the Antarctic Coast

“…The fitted slope of Δ 199 Hg/Δ 201 Hg ratios in the austral winter was 0.83 ± 0.11 (mean ± 1SD, R 2 = 0.79, P < 0.01, Figure S3). For reference, two of the most negative Δ 199 Hg values observed in PBM at another coastal station, Zhongshan, the eastern Antarctic (Figure S1), were also observed in March and October . Positive MDF and negative odd-MIF could be observed in most PBM values at the Zhongshan station (Figure ) compared to isotopic compositions of TGM at GWS, and the fitted slopes of Δ 199 Hg/Δ 201 Hg ratios in PBM at the Zhongshan station were 0.77 and 0.65 in the austral autumn and winter, respectively .…”

“…For reference, two of the most negative Δ 199 Hg values observed in PBM at another coastal station, Zhongshan, the eastern Antarctic (Figure S1), were also observed in March and October. 61 Positive MDF and negative odd-MIF could be observed in most PBM values at the Zhongshan station (Figure 1) compared to isotopic compositions of TGM at GWS, 61 and the fitted slopes of Δ 199 Hg/Δ 201 Hg ratios in PBM at the Zhongshan station were 0.77 and 0.65 in the austral autumn and winter, respectively. 61 These phenomena may be associated with AMDEs through a mechanism such as the oxidation process at a continental scale.…”

“…Stable isotopes have been utilized in many atmospheric Hg tracing studies globally outside the Antarctic ,,,,− and could thus be a useful tool to investigate the transport and transformation of atmospheric Hg in the Antarctic as well. However, only one isotopic study on PBM has been conducted at one coastal site in the eastern Antarctic . The isotopic composition of GEM as the dominated speciation of atmospheric Hg remains unknown in the Antarctic, preventing further understanding of the transport and transformation of atmospheric Hg.…”

“…However, only one isotopic study on PBM has been conducted at one coastal site in the eastern Antarctic. 61 The isotopic composition of GEM as the dominated speciation of atmospheric Hg remains unknown in the Antarctic, preventing further understanding of the transport and transformation of atmospheric Hg.…”

Spatial Distribution of Atmospheric Mercury Species in the Southern Ocean

“…These observations revealed that the atmosphere of the Antarctic continent during the sunlit season has a high oxidization capacity that could result in a high GOM content and/or obvious depletion of GEM (Angot, Dastoor et al., 2016). Several studies have shown that the Antarctic Plateau plays a key role in influencing the atmospheric Hg cycle at a continental scale (Angot, Dastoor et al., 2016; Li et al., 2020; Temme et al., 2003).…”