To insight into the impacts of biomass burning in Southeast Asia(SEA)and anthropogenic sources in inland China on distribution of atmospheric mercury in southwestern(SW)China.A monitoring project of atmospheric mercury has been carried out at Ailao Station(ALS)for Subtropical Forest Ecosystem Studies(2450 m above sea level)of Yunnan province,SW China.From May 2011 to May 2012,Measurements of total gaseous mercury(TGM,defined as the sum of Gaseous Eelemental Mercury,GEM,and gaseous oxidized mercury,GOM),GOM and particulate-bound mercury(PBM)were performed and one year of data have been processed.Meanwhile,to catch the information of biomass burning from SEA,the CO concentrations were monitored continually from September 2011 to May 2012.TGM at ALS showed a monsoonal distribution pattern with elevated concentrations since the onset of Indian summer monsoon(ISM)from May to September and low concentrations in the non-ISM period.Similarly,GOM and PBM showed a higher level in ISM period than non-ISM period.The study suggests that the ISM climate has a strong impact on long-range transport of Hg from anthropogenic sources and biomass burning in Southeast Asia(SEA)and South Asia(SA)as well as inland China,and contribute the higher TGM levels at ALS in ISM period.The high TGM events always accompanied with the appearance of northern wind in ISM period,and there were high Hg and CO events aroused with southern wind in non-ISM period.Obviously,high anthropogenic Hg emission from inland China could rapidly increase the TGM levels at ASL due to the strengthening of East Asia Summer Monsoon,the high-frequency fire events and biomass burning in SEA could be also an important reason for the high TGM level at ALS in non-ISM period.