Isotopic composition for source identification of mercury in atmospheric fine particles

Qiang Huang,Jiubin Chen,Pingqing Fu,Hongming Cai,Xinbin Feng,Benjamin Guinot,Zhongwei Wang,Zhuhong Wang,Lihai Shang,Ben Yu,Lianfang Wei,Weilin Huang,Shengliu Yuan

doi:10.5194/acp-16-11773-2016

Abstract

Abstract. The usefulness of mercury (Hg) isotopes for tracing the sources and pathways of Hg (and its vectors) in atmospheric fine particles (PM2.5) is uncertain. Here, we measured Hg isotopic compositions in 30 potential source materials and 23 PM2.5 samples collected in four seasons from the megacity Beijing (China) and combined the seasonal variation in both mass-dependent fractionation (represented by the ratio 202Hg ∕ 198Hg, δ202Hg) and mass-independent fractionation of isotopes with odd and even mass numbers (represented by Δ199Hg and Δ200Hg, respectively) with geochemical parameters and meteorological data to identify the sources of PM2.5-Hg and possible atmospheric particulate Hg transformation. All PM2.5 samples were highly enriched in Hg and other heavy metals and displayed wide ranges of both δ202Hg (−2.18 to 0.51 ‰) and Δ199Hg (−0.53 to 0.57 ‰), as well as small positive Δ200Hg (0.02 to 0.17 ‰). The results indicated that the seasonal variation in Hg isotopic composition (and elemental concentrations) was likely derived from variable contributions from anthropogenic sources, with continuous input due to industrial activities (e.g., smelting, cement production and coal combustion) in all seasons, whereas coal combustion dominated in winter and biomass burning mainly found in autumn. The more positive Δ199Hg of PM2.5-Hg in spring and early summer was likely derived from long-range-transported Hg that had undergone extensive photochemical reduction. The study demonstrated that Hg isotopes may be potentially used for tracing the sources of particulate Hg and its vectors in the atmosphere.

Highlights

Mercury (Hg) is a globally distributed hazardous metal and is well known for its long-range transport, environmental persistence and toxicity (Kim et al, 2009; Selin, 2009; Schleicher et al, 2015)
Only a few prior studies quantified the Hg concentrations in PM2.5 samples collected from Beijing (Wang et al, 2006; Zhang et al, 2013b; Schleicher et al, 2015), while no research attempted to track its sources using the Hg isotope approach
Our study reported, for the first time, large range and seasonal variations in both MDF and MIF of Hg isotopes in haze particulate (PM2.5) samples collected from Beijing

Summary

Introduction

Mercury (Hg) is a globally distributed hazardous metal and is well known for its long-range transport, environmental persistence and toxicity (Kim et al, 2009; Selin, 2009; Schleicher et al, 2015). Hg is emitted to the atmosphere through natural and anthropogenic processes or reemission of previously deposited legacy Hg. Hg is emitted to the atmosphere through natural and anthropogenic processes or reemission of previously deposited legacy Hg It has three operationally defined forms: gaseous elemental Hg (GEM), reactive gaseous Hg (RGM) and particle-bound Hg (PBM) (Selin, 2009). GEM (> 90 % of the total Hg in atmosphere) is fairly stable and can be transported globally, whereas RGM is rapidly deposited from the atmosphere in wet and dry deposition, and PBM is assumed to be transported more regionally (Selin, 2009; Fu et al, 2012). PM2.5-Hg is of particular concern because, once inhaled, both Hg and its vectors might have adverse effects on human beings

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