The Tibetan Plateau,known as the “Third Pole”,has been regarded as a sensitive region to global contaminant such as Hg impact due to its unique landform,fragile ecosystem and special monsoon circulation.Quantifying the contribution of Hg in wet deposition is important for understanding Hg biogeochemical cycling,anthropogenic sources,and verifying atmospheric models in the Tibetan Plateau.Hg in wet deposition was measured in Lhasa(the capital and largest city in Tibet)in 2010 and in Nam Co Station(a remote and background site in the Tibetan Plateau)from 2010 to 2011,respectively.Analysis of Hg speciation has presented HgP dominated the HgT in the wet-deposition samples and most of the Hg wet deposition fluxes occurred during the monsoon season.However,in contrast to the governing factor affecting HgT wet deposition flux at Nam Co Station,HgT concentration rather than precipitation amount was the factor governing HgT wet deposition flux at Lhasa.The greatest introduction of HgR%and MeHg%to terrestrial and aquatic landscapes occurs at the time biological activity peaks up during the growing season,indicating that deposited Hg might enhance MeHg availability for potential biotic uptake and thus endanger the ecosystem of the Tibetan Plateau at high ecological risk from MeHg bioavailability.Moreover,measured annual HgT flux was comparable to the estimates reconstructed from environmental records in the Nam Co region,suggesting that snowpit/lake sediment records appear to be reliable archives for estimating historical Hg accumulation rates in the Tibetan Plateau.A comparison among modeled wet and dry deposition,and measurements at Lhasa suggested that estimates of both wet and dry Hg deposition by GEOS-Chem model were 2 to 3 times higher than the measured annual wet flux.