Two years of measurements of atmospheric total gaseous mercury (TGM) at a remote site in Mt. Changbai area, Northeastern China
Total gaseous mercury (TGM) was continuously monitored at a remote site (CBS) in Mt. Changbai area, Northeastern China from 24 October 2008 to 31 October 2010. The overall mean TGM concentration was 1.60 plus or minus 0.51 ng m super(-3), which is lower than those reported from remote sites in Eastern, Southwestern, and Western China, indicating a relatively lower regional anthropogenic mercury (Hg) emission intensity in Northeastern China. Measurements at a site in the vicinity ( mu 1.2 km) of CBS station from August 2005 to July 2006 showed a significantly higher mean TGM concentration of 3.58 plus or minus 1.78 ng m super(-3). The divergent result was partially attributed to fluctuations in the relatively frequencies of surface winds during the two study periods and moreover an effect of local emission sources. The temporal variation of TGM at CBS was influenced by regional sources as well as long-range transported Hg. Regional sources frequently contributing to episodical high TGM concentrations were pin-pointed as a large iron mining district in Northern North Korea and two large power plants and urban areas to the southwest of the sampling site. Source areas in Beijing, Tianjin, southern Liaoning, Hebei, northwestern Shanxi, and northwestern Shandong were found to contribute to elevated TGM observations at CBS via long-range transport. Diurnal pattern of TGM at CBS was mainly controlled by regional sources, likely as well as intrusion of air masses from the free troposphere during summer season. There are no consistent seasonal pattern of TGM at CBS, and the monthly TGM variations showed links with the patterns of regional air movements and long-range transport.