Detection and quantification of gas-phase oxidized mercury compounds by GC/MS

Abstract

Most mercury pollution is emitted to the atmosphere, and the location and bioavailability of deposited mercury largely depends on poorly understood atmospheric chemical reactions that convert elemental mercury into oxidized mercury compounds. Current measurement methods do not speciate oxidized mercury, leading to uncertainty about which mercury compounds exist in the atmosphere and how oxidized mercury is formed. We have developed a gas chromatography/mass spectrometry (GC-MS)-based system for identification and quantification of atmospheric oxidized mercury compounds. The system consists of an ambient air collection device, a thermal desorption module, a cryofocusing system, a gas chromatograph, and an ultra-sensitive mass spectrometer. It was able to separate and identify mercury halides with detection limits low enough for ambient air collection (90 pg), but an improved ambient air collection device is needed. The GC/MS system was unable to quantify HgO or Hg(NO 3 ) 2 , and data collected cast doubt upon the existence of HgO in the gas phase.Published by Copernicus Publications on behalf of the European Geosciences Union.

Chemical cycling and deposition of atmospheric mercury in polar regions: review of recent measurements and comparison with models

“…Identification of Hg(II) species in ambient air emerges as one of the priorities for future research (Gustin et al, 2015). Recent advancement on analytical techniques may offer new insights into Hg(II) speciation Jones et al, 2016) but further research is still needed. Such advancement will greatly improve our understanding of atmospheric redox processes.…”

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

“…It is now well established that the corresponding HgOH and HgO products are too thermally unstable to enable oxidation to Hg II under atmospheric conditions Goodsite et al, 2004;Calvert and Lindberg, 2005;Hynes et al, 2009;Jones et al, 2016). OH and ozone could still potentially be important oxidants on aerosols (Ariya et al, 2015).…”

“…The speciation of atmospheric Hg II is unknown (Jaffe et al, 2014;Gustin et al, 2015;Jones et al, 2016). It is generally assumed from chemical equilibrium considerations that the main Hg II species are HgCl 2 in the gas phase and Hgchloride complexes in the aqueous phase (Hedgecock and Pirrone, 2001;Selin et al, 2007;Holmes et al, 2009).…”

Evaluation of CMAQ Coupled With a State‐of‐the‐Art Mercury Chemical Mechanism (CMAQ‐newHg‐Br)

“…The products from GEM 1 O 3 and GEM 1 OH reactions were assumed to be 50% of GOM and 50% PBM in the default CMAQ-Hg. Experimental studies suggest that the products of these two reactions could adsorb to the wall of the reaction chamber, forming clusters and aerosols (Jones et al, 2016;Subir et al, 2011 and references therein). Therefore, in NEW_noOH and NEW the products from these two reactions were assumed to directly deposit to the Earth's surface in the model layer at the surface-atmosphere interface and to form PBM on the surface of aerosols in the upper model layers.…”