Mercury is a persistent and bioaccumulative toxic pollutants(PBTs),which could cause adverse effects on the nervous system and liver of human body and has been identified as a potentially toxic chemical substance by the United Nations(UN).Atmospheric mercury is a global air pollutant distributed via long-range transport(LRT).The objective of this study is to introduce continuous monitoring to determine the atmospheric total gaseous mercury(TGM)at a remote site located at the Dongsha Islands of northern South China Sea,a small coral reef island with an area of 1.74 km2 which is about 440 km northeast to the Taiwan Island.The ambient air quality of the Dongsha Islands is influenced not only by the contaminants via long-range transport from northeastern Asia,but also from the Southeast Asia and the Southwest Chinas regional biomass burning in the springtime.Moreover,Taiwan is located at the downwind site of the gyre systems in Asia,which thus affected the ambient air quality of Taiwan Island.TGM sampling was conducted from February to July,2014.Twenty-four hour continuous monitoring of TGM was undertaken by using a mercury continuous monitor(Tekran 2537B)in which monitoring data was recorded by five-minute intervals,the dual gold amalgam setup in the Tekran 2537B could be used to adsorb and further analyze the TGM.This study also integrated the NOAA-HYSPLIT model with a global fire map and a backward trajectory to simulate the transportation routes of air mass.The results showed that the average concentration of TGM was 2.7±0.23 ng/m3 from February to July,while the average day and night concentrations were 2.9±0.20 ng/m3 and 2.7±0.23 ng/m3.Moreover,the results of backward trajectory simulation showed that the polluted air mass was mostly transported from the Northeast Asia.