Alternate materials for the capture and quantification of gaseous oxidized mercury in the atmosphere

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