Atmospheric mercury observations from Antarctica: seasonal variation and source and sink region calculations

Abstract

Abstract. Long term atmospheric mercury measurements in the Southern Hemisphere are scarce and in Antarctica completely absent. Recent studies have shown that the Antarctic continent plays an important role in the global mercury cycle. Therefore, long term measurements of gaseous elemental mercury (GEM) were initiated at the Norwegian Antarctic Research Station, Troll (TRS) in order to improve our understanding of atmospheric transport, transformation and removal processes of GEM. GEM measurements started in February 2007 and are still ongoing, and this paper presents results from the first four years. The mean annual GEM concentration of 0.93 ± 0.19 ng m −3 is in good agreement with other recent southern-hemispheric measurements. Measurements of GEM were combined with the output of the Lagrangian particle dispersion model FLEXPART, for a statistical analysis of GEM source and sink regions. It was found that the ocean is a source of GEM to TRS year round, especially in summer and fall. On time scales of up to 20 days, there is little direct transport of GEM to TRS from Southern Hemisphere continents, but sources there are important for determining the overall GEM load in the Southern Hemisphere and for the mean GEM concentration at TRS. Further, the sea ice and marginal ice zones are GEM sinks in spring as also seen in the Arctic, but the Antarctic oceanic sink seems weaker. Contrary to the Arctic, a strong summer time GEM sink was found, when air originates from the Antarctic plateau, which shows that the summertime removal mechanism of GEM is completely different and is caused by other chemical processes than the springtime atmospheric mercury depletion events. The results were corroborated by an analysis of ozone source and sink regions.

Comparison of mercury concentrations measured at several sites in the Southern Hemisphere

“…The station has been in operation since January/February 2007 and its current continuous measurements include mercury, CO, O 3 , particles, greenhouse gases, hydrocarbons, persistent organic compounds (POPs) and meteorological parameters (Hansen et al, 2009;Pfaffhuber et al, 2012). Mercury has been measured using the Tekran 2537B instrument since February 2007 with a 5 min sampling frequency.…”

Chemical cycling and deposition of atmospheric mercury in polar regions: review of recent measurements and comparison with models

“…While the Arctic has been extensively monitored -with hundreds of publications focusing on AMDEs -measurements are sporadic in Antarctica. To the best of the author's knowledge, only 11 studies dealing with atmospheric mercury in Antarctica (and using modern instrument) have been published (Ebinghaus et al, 2002;Sprovieri et al, 2002;Temme et al, 2003;Brooks et al, 2008a, b;Dommergue et al, 2012;Pfaffhuber et al, 2012;Nerentorp Mastromonaco et al, 2016;Wang et al, 2016). The earliest studies showed the occurrence of AMDEs in coastal Antarctica after polar sunrise.…”

Trend and seasonal variation of atmospheric mercury concentrations at the Cape Point GAW observatory, South Africa

“…The maxima in July and August in the high resolution data look like a systematic feature whose origin has yet to be investigated. The seasonal variation at the Troll station (Pfaffhuber et al, 2012) is different with a maximum from April till July and a minimum in austral spring and summer (November -January). The difference is most likely due to mercury depletion events in Antarctica occurring during austral spring and summer (Steffen et al, 2008).…”

“…All measurements were thus used in Fig. 1 Pfaffhuber et al (2012). In contrast to the absence of trends at both stations in the southern hemisphere, a decreasing trend of -0.049 ng m -3 yr -1 can be derived from the GEM monthly means at Mace Head since March 2007 until the end of 2011.…”