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

Abstract

Abstract. Correlation analysis between atmospheric mercury (Hg) and other trace gases are useful for identification of sources and constraining regional estimated 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 / CO2, and GEM / CH4 for mainland China, South Asia, Indochinese Peninsula, and Central Asia using the ground-based observations at three remote sites in northwest and southwest China, and applied the values to estimate GEM emissions in the four source regions. The geometric mean of the GEM / CO correlation slopes for mainland China, South Asia, 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. The values in the same source regions were 240 ± 119, 278 ± 164, 315 ± 289 pg m−3 ppm−1 for the GEM / CO2 correlation slopes; and 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 / CH4 correlation slopes, respectively. These values were the first reported correlation slopes of GEM / CO, GEM / CO2, and GEM / CH4 in four important source regions of Asia except the GEM / CO ratios in mainland China. The correlation slopes of GEM / CO, GEM / CO2 and GEM / CH4 in Asia were relatively higher than those observed in Europe, North America and South Africa, which may highlight GEM emissions from non-ferrous smelting, mercury mining, natural sources and historical deposited mercury (re-emission) in Asia. Using the observed GEM / CO and GEM / CO2 slopes, and the recently reported emission inventories of CO and CO2, the annual GEM emissions in mainland China, South Asia, Indochinese Peninsula, and Central Asia were estimated to be in the ranges of 1071–1187 t, 340–470 t, 125 t, and 54–90 t, respectively. The estimate quantity of GEM emissions from the GEM / CH4 correlation slopes is significantly larger, which may be due to fewer common emission sources of GEM and CH4 and large uncertainties associated with CH4 emission inventories in Asia and therefore lead 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 by recent studies. This may reflect the fast increasing anthropogenic GEM emissions in Asian countries in recent years. A preliminary assessment of natural emissions of GEM in China and other Asian regions was also made and well explains the discrepancies.

Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

“…The observational data sets obtained from the China “973” mercury ambient monitoring network and from earlier publications for the other sites are all measured during 2009–2014. A more detailed information of measured data set can be found in Table S4 (Bo et al, ; H. S. Chen et al, ; X. J. Chen et al, ; Ci et al, ; Ci, Zhang, & Wang, , Ci et al, ; Ci, Zhang, Wang, & Niu, , b; Friedli et al, ; Fu, Feng, Dong, et al, ; Fu, Feng, Liang, et al, ; Fu, Feng, Shang, et al, ; Fu et al, ; Fu, Feng, Sommar, et al, ; Fu, Feng, Zhu, et al, ; Fu, Zhu, et al, ; Fu, Yang, et al, ; Fu, Zhang, Lin, et al, ; Fu, Zhang, Yu, et al, ; J.‐S. Han et al, ; Y.‐J.…”

“…Observational and modeling evidence indicated a distinct trans‐Pacific transport of Hg from China by the prevailing westerlies (Jaffe et al, ; Jaffe & Strode, ; Strode et al, ). Atmospheric Hg monitoring and receptor modeling results from the China “973” project showed that Hg emissions from biomass burning in South and Southeast Asia can be transported to the southwest region of Mainland China, leading to elevated Hg concentration events (Fu, Zhang, Lin, et al, ; X. Wang et al, ; H. Zhang, Fu, et al, ). Furthermore, Hg observation at Mt.…”

Transboundary transport and deposition of Hg emission from springtime biomass burning in the Indo‐China Peninsula

“…Five‐minute TGM (GEM + GOM) concentrations were measured using a Tekran 2537A Hg analyzer. Details regarding the measurement system and the quality assurance routines have been presented in our earlier work [ Fu et al ., , , , ]. Briefly, the Tekran 2537A was automatically calibrated for Hg 0 every 73 h using an internal permeation source, which provides approximately 1 pg s −1 of Hg 0 at 50°C into a zero air stream.…”

“…The instrument has an analytical linearity of ±1% at full scale. The instrument was calibrated once a week using a CO standard at 1 ppmv to keep analytical sensitivity stable (recoveries in the range of 98%–102%) [ Fu et al ., ]. The hourly CO data (used in section 2.3) have an averaging uncertainty of <6%.…”

“…CO is regarded as an important tracer for Hg released by biomass burning [ Hamrud , ; Weinstock , ]. The correlation slope of TGM and CO concentration (ΔTGM/ΔCO) in fire plumes has been employed to estimate Hg emission from combustion sources [ Brunke et al ., ; Ebinghaus et al ., ; Friedli et al ., , , ; Fu et al ., ; Jaffe et al ., ; Sigler et al ., ; Weiss‐Penzias et al ., ]. Using ΔTGM/ΔCO slopes for estimating Hg emission has an advantage in averaging the emission heterogeneity for a large burned area and provides reasonable data in areas where Hg data of primeval forest ecosystems are not readily available [ Biswas et al ., ].…”