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Abstract. Reactive mercury (RM), the sum of both gaseous oxidized Hg and particulatebound Hg, is an important component of the global atmospheric mercury cycle,but measurement currently depends on uncalibrated operationally definedmethods with large uncertainty and demonstrated interferences and artifacts.Cation exchange membranes (CEMs) provide a promising alternative methodologyfor quantification of RM, but method validation and improvements are ongoing.For the CEM material to be reliable, uptake of gaseous elemental mercury(GEM) must be negligible under all conditions and RM compounds must becaptured and retained with high efficiency. In this study, the performance ofCEM material under exposure to high concentrations of GEM (1.43×106 to 1.85×106 pg m−3) and reactive gaseous mercurybromide (HgBr2 ∼5000 pg m−3) was explored using acustom-built mercury vapor permeation system. Quantification of totalpermeated Hg was measured via pyrolysis at 600 ∘C and detectionusing a Tekran® 2537A. Permeation tests wereconducted over 24 to 72 h in clean laboratory air, with absolute humiditylevels ranging from 0.1 to 10 g m−3 water vapor. GEM uptake by the CEMmaterial averaged no more than 0.004 % of total exposure for all testconditions, which equates to a non-detectable GEM artifact for typicalambient air sample concentrations. Recovery of HgBr2 on CEM filters wason average 127 % compared to calculated total permeated HgBr2 based onthe downstream Tekran® 2537A data. The lowHgBr2 breakthrough on the downstream CEMs (< 1 %) suggests thatthe elevated recoveries are more likely related to suboptimal pyrolyzerconditions or inefficient collection on the Tekran® 2537A gold traps. 

A method was developed to measure gaseous oxidized mercury (GOM) air-surface exchange using 2 replicated dynamic flux chambers (DFCs) in conjunction with cation exchange membrane (CEM) filters. The experimental design and method was developed and tested in a laboratory setting, using materials collected from industrial scale open pit gold mines in central Nevada, USA. Materials used included waste rock, heap leach ore, and tailings, with substrate concentrations ranging from 100 to 40000 ng g-1 total mercury (THg). CEM filters were used to capture GOM from the DFC sample lines while a Tekran® 2537A analyzer measured GEM concurrently. Previous and ongoing work has demonstrated that CEM do not collect GEM and efficiently collect multiple compounds of GOM. GOM emission rates up to 4000 pg m- 2 h-1 were measured from tailings materials with high Hg substrate concentrations, and this has significant implication with respect to air-Hg surface exchange. GOM flux was variable for lower Hg concentration substrates, with both emission and deposition observed, and this was affected by ambient air GOM concentrations. For substrates that experienced GOM deposition, deposition velocities were in the range 0.01 – 0.07 cm s-1.