A 2 year record of atmospheric mercury species at a background Southern Hemisphere station on Amsterdam Island
Scarcity of mercury species records in the Southern Hemisphere is a critical weak point for the development of appropriate modeling and regulation scenarios. Under the framework of the “Global Mercury Observation System” (GMOS) project, a monitoring station has been set up on Amsterdam Island (37_480 S, 77_340 5 E) in the remote southern Indian Ocean. For the first time in the Southern Hemisphere, a 2 year record of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle-bound mercury (PBM) is presented. GEM concentrations were remarkably steady (1.03±0.08 ngm−3) while RGM and PBM concentrations were very low and 10 exhibited a strong variability (mean: 0.34 pgm−3 [range: 0.28–4.07 pgm−3] and mean: 0.67 pgm−3 [range: 0.28–12.67 pgm−3], respectively). Despite the remoteness of the island, wind sector analysis, air mass back trajectories and the observation of radonic storms highlighted a long-range contribution from the southern African continent to the GEM and PBM budgets in winter during the biomass burning season. Lowest con15 centrations of GEM were associated with southerly polar and marine air masses from the remote southern Indian Ocean. This unique dataset provides new baseline GEM concentrations in the Southern Hemisphere mid-latitudes for further modeling studies, while mercury speciation along with upcoming wet deposition data will help improving our understanding of mercury cycle in the marine boundary layer.