Wet deposition of Total Mercury: Concentration, Rainfall Depth and Fluxes in the Southern Indian Ocean at Amsterdam Island (38°S): GMOS project.

Mercury (Hg) is a toxic worldwide trace element which due to its volatility once emitted into the atmosphere from both natural and anthropogenic sources, is transported to long distance and transferred to aquatic and terrestrial receptors by wet and dry deposition. Amsterdam Island (AMS) hosts a French Scientific Base were in the framework of the Global Mercury Observation System (GMOS) project scientists performed for the first time measurements of mercury in ambient air and deposition. Rainfall depth and Total Mercury (THg) concentrations and fluxes in wet deposition were determined for all samples collected from March 2013 to December 2014 at this GMOS master site. Weekly, biweekly and monthly-based precipitation samples were collected using automated wet-only precipitation collection system. Samples were treated according to GMOS protocol and analyzed by cold vapor atomic fluorescence spectrometry (CVAFS). This report presents the results of THg concentrations in precipitation. THg concentration in wet deposition samples ranged from 0.6 ng L-1 to 4.6 ng L-1 (September 2013), and the rainfall depth values were 2.9 and 123.9 mm (April 2013). The volume-weighted mean (VWM) concentrations and annual wet deposition fluxes of THg in precipitation were 2.0 ng L-1 and 3.4 micro g m-2 yr-1 respectively. For the entire study THg flux has been estimated to be 5.4 ng m-2 d-1. Annual mean of THg concentrations in rainy samples obtained at Amsterdam Island site during this study was comparable to the mean values observed at rural and remote sites at different latitudes reported in scientific papers and project reports.