Intercontinental transport and deposition patterns of atmospheric mercury from anthropogenic emissions

Abstract

Abstract. Global policies that regulate anthropogenic mercury emissions to the environment require quantitative and comprehensive source-receptor relationships for mercury emissions, transport and deposition among major continental regions. In this study, we use the GEOS-Chem global chemical transport model to establish source-receptor relationships among 11 major continental regions worldwide. Source-receptor relationships for surface mercury concentrations (SMC) show that some regions (e.g., East Asia, the Indian subcontinent, and Europe) should be responsible for their local surface Hg(II) and Hg(P) concentrations due to near-field transport and deposition contributions from their local anthropogenic emissions (up to 64 and 71 % for Hg(II) and Hg(P), respectively, over East Asia). We define the region of primary influence (RPI) and the region of secondary influence (RSI) to establish intercontinental influence patterns. Results indicate that East Asia is the SMC RPI for almost all other regions, while Europe, Russia, and the Indian subcontinent also make some contributions to SMC over some receptor regions because they are dominant RSI source regions. Source-receptor relationships for mercury deposition show that approximately 16 and 17 % of dry and wet deposition, respectively, over North America originate from East Asia, indicating that transpacific transport of East Asian emissions is the major foreign source of mercury deposition in North America. Europe, Southeast Asia, and the Indian subcontinent are also important mercury deposition sources for some receptor regions because they are the dominant RSIs. We also quantify seasonal variation on mercury deposition contributions over other regions from East Asia. Results show that mercury deposition (including dry and wet) contributions from East Asia over the Northern Hemisphere receptor regions (e.g., North America, Europe, Russia, the Middle East, and Middle Asia) vary seasonally, with the maximum values in summer and minimum values in winter. The opposite seasonal pattern occurs on mercury dry deposition contributions over Southeast Asia and the Indian subcontinent.

Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

“…The transport of GEM is 34% in summer, 26% in winter, 22% in spring, and 18% in autumn; while the TB of GOM and PBM are consistently negative during spring and summer, suggesting a net removal of GOM/PBM from air in the region. These findings are consistent with earlier results by the global models that GEM is the main Hg form exported from East Asia and GOM/PBM deposit locally (L. Chen et al, 2014;H. S. Chen et al, 2015;Selin et al, 2008).…”

“…Given the difference of total deposition between the base-case and zero emission case in Tables 2 and S3, it is estimated that~65% Hg deposition in Mainland China is caused by domestic emissions. This is consistent with these results from L. Chen et al (2014) and Lin et al (2010), which exhibits that 60-75% deposition in China is caused by local emissions. Table 3 shows a summary of results obtained from regional and global scale Hg modeling assessments (L. Chen et al, 2014;H.…”

“…The so-called natural emission in this study refers to the Hg release associated with natural processes emitting Hg 0 from the natural surfaces including soil, water, vegetation, ice, and snow surfaces, including re-emission of previously deposited Hg. Hg emissions and their outflow from East Asia have been regarded as a concern to global Hg pollution due to the large quantity of Hg release in the region (L. Chen et al, 2014;Jaffe et al, 2005;Lin et al, 2010). According to the 2013 Global Mercury Assessment, anthropogenic Hg emissions in East Asia account for 35% of global total in 2010 (UNEP, 2013), with China as the largest emitter .…”

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

“…It can be seen that the models generally underestimate mercury concentrations. This is in line with many previous model studies which found that models tend to underestimate current TM concentrations in Europe (Bieser et al, 2014b;Chen et al, 2014;Muntean et al, 2014;Gencarelli et al, 2017). Based on a model run from 1996 to 2008, Muntean et al (2014) hypothesized that this was due to an overestimation of emission reductions in the last decade.…”

Biological and chemical contaminants as drivers of change in the Great Lakes–St. Lawrence river basin

“…Hg may also travel tens of thousands of kilometers through the atmosphere before deposition, making its potential sources within the Great Lakes basin also a source to national and global ecosystems. East Asia was recently identified as contributing to nearly 16% of Hg deposition in North America (Chen et al, 2013). In the form of methylmercury (MeHg), Hg is biomagnified with a concentration factor of 100 between phytoplankton and piscivorous fish.…”