[Variation characteristics of total gaseous mercury at Wuzhi mountain (Wuzhishan) background station in Hainan].

Total gaseous mercury (TGM) was continuously monitored at Wuzhi mountain (Wuzhishan) using the high-resolution automatic atmospheric mercury vapor analyzer (Tekran 2537B) from May 2011 to May 2012. The annual geometric mean TGM concentration was (1.58 ± 0.71) ng x m(-3), suggesting that the atmosphere was not obviously polluted. The TGM level at WuZhi mountain remained low from June to August in 2011 and from March to May in 2012, while higher values were observed from September in 2011 to January in 2012. Tropical monsoons played an important role in the monthly variation of TGM. TGM concentrations showed a clear diurnal trend with the minimum concentration occurring at 09:00 AM and the peak concentration at 19:00 PM due to the combined impact of the long-range transport of atmospheric mercury and local meteorological conditions. The temporal trend of TGM highlighted the impact of long-range transport from the mainland of China on the distribution of TGM in ambient air at Wuzhi mountain by the results of backward trajectory analysis using HYSPLIT.