Atmospheric gaseous elemental mercury (GEM) concentrations and mercury depositions at a high-altitude mountain peak in south China

摘要

China is regarded as the largest contributor of mercury (Hg) to the globalatmospheric Hg budget. However, concentration levels and depositions ofatmospheric Hg in China are poorly known. Continuous measurements ofatmospheric gaseous elemental mercury (GEM) were carried out from May 2008to May 2009 at the summit of Mt. Leigong in south China. Simultaneously,deposition fluxes of THg and MeHg in precipitation, throughfall andlitterfall were also studied. Atmospheric GEM concentrations averaged2.80±1.51 ng m−3, which was highly elevated compared to globalbackground values but much lower than semi-rural and industrial/urban areasin China. Sources identification indicates that both regional industrialemissions and long range transport of Hg from central, south and southwestChina were corresponded to the elevated GEM level. Seasonal and diurnalvariations of GEM were observed, which reflected variations in sourceintensity, deposition processes and meteorological factors. Precipitationand throughfall deposition fluxes of THg and MeHg in Mt. Leigong werecomparable or lower compared to those reported in Europe and North America,whereas litterfall deposition fluxes of THg and MeHg were higher compared toEurope and North America. This highlights the importance of vegetation to Hgatmospheric cycling. In th remote forest ecosystem of China, deposition ofGEM via uptake of foliage followed by litterfall was very important for thedepletion of atmospheric Hg. Elevated GEM level in ambient air mayaccelerate the foliar uptake of Hg through air which may partly explain theelevated litterfall deposition fluxes of Hg observed in Mt. Leigong.