Domestic and Transboundary Sources of Atmospheric Particulate Bound Mercury in Remote Areas of China: Evidence from Mercury Isotopes

Abstract

Isotopic composition of atmospheric particulate bound mercury (PBM) was obtained at four remote sites in different geographical regions of China for three to 12 month periods. Mean (±1σ) Δ 199 Hg PBM was the highest at the site in southwestern China (0.66 ± 0.32‰), followed by the site in northeastern China (0.36 ± 0.34‰), the site in the marine boundary layer of East China Sea (0.35 ± 0.33‰), and was the lowest at the site in northwestern China (0.27 ± 0.22‰). Δ 199 Hg PBM was relatively higher in cold than warm season at the sites in northwestern and southwestern China, whereas the opposite was found at the site in northeastern China. We propose that the seasonal variations of Δ 199 Hg PBM were influenced by the exposure of air masses to regional (e.g., anthropogenic and dust related) and long-range (e.g., anthropogenic and oceanic) sources in the preceding several days, with the former characterized by lower Δ 199 Hg PBM and the latter characterized by more positive Δ 199 Hg PBM due to sufficient atmospheric transformations. Modeling results from Potential Source Contribution Function suggested that domestic anthropogenic emission was the major contributor to PBM pollution at the sites in northeastern and eastern China, whereas long-range transboundary transport of PBM from South Asia played a more important role at the sites in southwestern and northwestern China.

A Laboratory Study on the Isotopic Composition of Hg(0) Emitted From Hg‐Enriched Soils in Wanshan Hg Mining Area

“…A standard reference NIST SRM 3177 was analyzed repeatedly to obtain the analytical uncertainty of isotopic compositions during instrumental procedures. The mean values of δ 202 Hg, Δ 199 Hg, Δ 200 Hg, and Δ 201 Hg for all NIST SRM 3177 standard were −0.51 ± 0.13‰, −0.01 ± 0.06‰, 0.01 ± 0.05‰, and −0.01 ± 0.08‰ (2 SD, n = 30), respectively, which are in agreement with previously reported values (Fu, Zhang, Feng , et al, 2019; Sun et al, 2016). In addition, isotopic compositions of standard references of BCR 482 (δ 202 Hg = −1.63 ± 0.19‰; Δ 199 Hg = −0.58 ± 0.08‰; Δ 200 Hg = 0.07 ± 0.08‰; and Δ 201 Hg = −0.60 ± 0.12‰, 2 SD; n = 6) and NIST 2711 (δ 202 Hg = −0.18 ± 0.08‰; Δ 199 Hg = −0.24 ± 0.05‰; Δ 200 Hg = 0.00 ± 0.05‰; and Δ 201 Hg = −0.18 ± 0.08‰, 2 SD, n = 10) were also measured and agreed with previously published results (Biswas et al, 2008; Blum & Johnson, 2017; Estrade et al, 2010; Smith et al, 2015; Wiederhold et al, 2013).…”

Response to Referee #2's comments

“…The PMF model is widely used to quantitatively determine the source contributions of specific air pollutants (Gibson et al, 2015). The essential principle of PMF is that the concentration of each sample is determined by source profiles and different contributions.…”

Mercury isotopic compositions in fine particles and offshore surface seawater in a coastal area of East China: Implication for Hg sources and atmospheric transformations

“…What's more, specific ratios of Δ 199 Hg/Δ 201 Hg have been reported for different transformation processes, i.e.,~1.0 for photo-reduction and 92~1 .6 for photo-oxidation (Bergquist and Blum, 2007;Sun et al, 2016a). Even-MIF of Hg isotopes is observed mostly in atmosphere related samples, which is suggested to associate with photo-oxidation of Hg 0 by UV and oxidants (Chen et al, 2012;Blum and Johnson, 2017;Fu et al, 2019). Therefore, Hg isotopes are capable of becoming useful tracers for biogeochemical cycles of Hg in the environment.…”

“…Little literature is available on Hg isotopes of atmospheric samples due to the difficulty in sampling enough Hg mass for isotopes analysis. Even so, Hg isotopic compositions of atmosphere related samples, like speciated Hg, precipitation, and lichen, have been reported in recent years (Carignan et al, 2009;Gratz et al, 2010;Sherman et al, 2010;Chen et al, 2012;Rolison et al, 2013;Demers et al, 2013Demers et al, , 2015Fu et al, 2016Fu et al, , 2018Fu et al, , 2019Yu et al, 2016Yu et al, , 2020. Many studies have measured Hg isotopes in PM to investigate its potential sources and transformation processes in the atmosphere.…”

“…While HgPM in remote and coastal areas displays more significant odd-MIF, likely linking to enhanced photo-reactions (Rolison et al, 2013;Fu et al, 2019). To date, the fractionation of Hg isotopes in atmospheric processes has not been well elucidated, which hampers application of Hg isotopes in tracking the transfer and transformation paths of Hg.…”