Atmospheric particulate mercury in Lhasa city, Tibetan Plateau

Abstract

In an effort to understand the biogeochemical cycling and seasonal characteristics of atmospheric Hg, a total of 80 daily sampled total suspended particulates were collected at Lhasa, the largest city of Tibet, from April 2013 to August 2014 for particulate-bound Hg (HgP) analysis. Daily concentrations of atmospheric HgP ranged from 61.2 to 831 pg m−3 with an average of 224 pg m−3, which were unexpectedly comparable to those measured in most of the Chinese metropolises. Both the daily/monthly average HgP concentrations were slightly but not significantly higher during the non-monsoon season than during the monsoon season. Together with the fact that there was lack of significant relationship between HgP concentration and most meteorological parameters, no significant and distinct pattern for the seasonal characteristics of atmospheric HgP could be mainly attributed to the almost equal emission strength of two principal anthropogenic Hg sources (i.e., industrial emission sources during the non-monsoon season, and vehicular traffic and religious sources during the monsoon season). Moreover, the HgP dry deposition rate was estimated to be 35.3 μg m−2 yr−1 by using a theoretical model, which was significantly higher than those Hg wet fluxes. The elevated deposition rate implied that dry deposition may play an important role in the biogeochemical Hg cycling over the Tibetan Plateau.