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Abstract. Methodologies for identifying atmospheric oxidized mercury (HgII) compounds, including particulate-bound HgII (HgII(p)) and gaseous oxidized mercury (HgII(g)), by mass spectrometry are currently under development. This method requires preconcentration of HgII for analysis due to high instrument detection limits relative to ambient HgII concentrations. The objective of this work was to identify and test materials for quantitative capture of HgII from the gas phase and to suggest potential surfaces onto which HgII can be collected, thermally desorbed, and characterized using mass spectrometry methods. From the literature, several compounds were identified as potential sorbent materials and tested in the laboratory for uptake of gaseous elemental mercury (Hg0) and HgII(g) (permeated from a HgBr2 salt source). Chitosan, α-Al2O3, and γ-Al2O3 demonstrated HgII(g) capture in ambient air laboratory tests, without sorbing Hg0 under the same conditions. When compared to cation exchange membranes (CEMs), chitosan captured a comparable quantity of HgII(g), while ≤90 % of loaded HgII(g) was recovered from α-Al2O3 and γ-Al2O3. When deployed in the field, the capture efficiency of chitosan decreased compared to CEMs, indicating that environmental conditions impacted the sorption efficiency of this material. The poor recovery of HgII from the tested materials compared to CEMs in the field indicates that further identification and exploration of alternative sorbent materials are required to advance atmospheric mercury chemistry analysis by mass spectrometry methods. 

Mercury (Hg) researchers have made progress in under- standing atmospheric Hg, especially with respect to oxidized Hg (HgII) that can represent 2 to 20% of Hg in the atmosphere. Knowledge developed over the past ∼10 years has pointed to existing challenges with current methods for measuring atmospheric Hg concentrations and the chemical composition of HgII compounds. Because of these challenges, atmospheric Hg experts met to discuss limitations of current methods and paths to overcome them considering ongoing research. Major conclusions included that current methods to measure gaseous oxidized and particulate-bound Hg have limitations, and new methods need to be developed to make these measurements more accurate. Developing analytical methods for measure- ment of HgII chemistry is challenging. While the ultimate goal is the development of ultrasensitive methods for online detection of HgII directly from ambient air, in the meantime, new surfaces are needed on which HgII can be quantitatively collected and from which it can be reversibly desorbed to determine HgII chemistry. Discussion and identification of current limitations, described here, provide a basis for paths forward. Since the atmosphere is the means by which Hg is globally distributed, accurately calibrated measurements are critical to understanding the Hg biogeochemical cycle.