Correlation slopes of GEM / CO, GEM / CO<sub>2</sub>, and GEM / CH<sub>4</sub> and estimated mercury emissions in China, South Asia, the Indochinese Peninsula, and Central Asia derived from observations in northwestern and southwestern China

Abstract

Abstract. Correlation analyses between atmospheric mercury (Hg) and other trace gases are useful for identification of sources and constraining regional Hg emissions. Emissions of Hg in Asia contribute significantly to the global budget of atmospheric Hg. However, due to the lack of reliable data on the source strength, large uncertainties remain in the emission inventories of Hg in Asia. In the present study, we calculated the correlation slopes of GEM / CO, GEM / CO 2 , and GEM / CH 4 for mainland China, South Asia, the Indochinese Peninsula, and Central Asia using the ground-based observations at three remote sites in northwestern and southwestern China, and applied these values to estimate GEM emissions in the four source regions. The geometric mean GEM / CO correlation slopes for mainland China, South Asia, the Indochinese Peninsula, and Central Asia were 7.3 ± 4.3, 7.8 ± 6.4, 7.8 ± 5.0, and 13.4 ± 9.5 pg m −3 ppb −1 , respectively, and values in the same source regions were 33.3 ± 30.4, 27.4 ± 31.0, 23.5 ± 15.3, and 20.5 ± 10.0 pg m −3 ppb −1 for the GEM / CH 4 correlation slopes, respectively. The geometric means of GEM / CO 2 correlation slopes for mainland China, South Asia, and Central Asia were 240 ± 119, 278 ± 164, 315 ± 289 pg m −3 ppm −1 , respectively. These values were the first reported correlation slopes of GEM / CO, GEM / CO 2 , and GEM / CH 4 in four important source regions of Asia, not including the GEM / CO ratios in mainland China. The correlation slopes of GEM / CO, GEM / CO 2 , and GEM / CH 4 in Asia were relatively higher than those observed in Europe, North America, and South Africa, which may highlight GEM emissions from nonferrous smelting, large-scale and artisanal mercury and gold production, natural sources, and historically deposited mercury (re-emission) in Asia. Using the observed GEM / CO and GEM / CO 2 slopes, and the recently reported emission inventories of CO and CO 2 , the annual GEM emissions in mainland China, South Asia, the Indochinese Peninsula, and Central Asia were estimated to be in the ranges of 1071-1187, 340-470, 125, and 54-90 t, respectively. The estimated quantity of GEM emissions from the GEM / CH 4 correlation slopes is significantly larger, which may be due to the larger uncertainties in CH 4 emissions in Asia as well as insufficient observations of GEM / CH 4 correlation slopes, therefore leading to an overestimate of GEM emissions. Our estimates of GEM emissions in the four Asian regions were significantly higher (3-4 times) than the anthropogenic GEM emissions reported in recent studies. This discrepancy could come from a combination of reasons including underestimates of anthropogenic and natural GEM emissions; large uncertainties related to CO, CO 2 , and CH 4 emission inventories; and inherent limitations of the correlation slope method.

Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

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Monsoon-facilitated characteristics and transport of atmospheric mercury at a high-altitude background site in southwestern China

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Atmospheric wet and litterfall mercury deposition at urban and rural sites in China

“…Recent studies revealed that Hg emissions from anthropogenic and natural sources in China were in the range of 800-1200 t (Shetty et al, 2008; S. X. Fu et al, 2015a;Wang et al, 2016), approximately 1/6 of the global Hg emissions into the atmosphere Song et al, 2015). The large emissions in China not only have an impact on the domestic Hg pollution (Fu et al, 2015b), but also have the potential to enhance atmospheric Hg concentration and deposition elsewhere (Seigneur et al, 2004;Strode et al, 2008;Durnford et al, 2010).…”