Use of Passive Sampling Methods and Models to Understand Sources of Mercury Deposition to High Elevation Sites in the Western United States

Abstract

To understand gaseous oxidized mercury (GOM) sources to the Western US, data were collected with passive samplers for ambient GOM concentrations and dry deposition at 10 sites from the coast of the Pacific Ocean to Great Basin National Park. Tests were done to better understand the samplers and the materials used. Measured dry deposition of GOM was significantly higher at sites >2000 m elevation relative to those below due to high GOM concentrations and atmospheric turbulence. At these high elevation sites, GOM dry deposition was higher in spring due to long-range transport from Asia (air parcels from the free troposphere) and some high GOM dry deposition events were related to regional emissions. Dry deposition of GOM at two sites was calculated using the passive sampler data and a multiple-resistance model. A previously developed relationship between the sampling rate of the passive sampler and GOM concentrations was used to estimate dry deposition and a scaling factor of 3 was used to adjust GOM concentrations, due to underestimation by KCl-coated denuder measurements. With the scaling factor of 3, modeled deposition was in the range of results estimated from two different models settings. However, dry deposition did not correlate consistently with either model. The disagreement could be due to uncertainties associated with measurements and/or modeling, or different GOM compounds existing in the atmosphere. If the atmospheric GOM compounds are known, dry deposition velocities could be estimated more accurately. Lastly, we investigated the potential for use of a new sampling material for GOM and checked the efficiency of the passive sampler.

Evaluation of cation exchange membrane performance under exposure to high Hg<sup>0</sup> and HgBr<sub>2</sub> concentrations

“…Similar variable breakthrough issues were observed in the earliest field-based CEM measurements as well (Mason et al, 1997). In contrast to ambient measurements, previous laboratory experiments have reported only minor (0 % to 16 %) or no breakthrough (Huang and Gustin, 2015a;Huang et al, 2013). Limited experimental work with flow rates of 1.0 and 16.7 L min −1 in ambient air could not provide an explanation for differing breakthrough rates (Pierce and Gustin, 2017).…”

“…450 material indicated it does not adsorb significant quantities of GEM in passive exposures but does selectively uptake gas-phase Hg 2+ species (Lyman et al, 2007). The CEM material was subsequently adapted for use in active sample flow systems, with the presumption of continued inertness to GEM and selectivity for GOM (Huang and Gustin, 2015a;Huang et al, 2013). These studies and others (Lyman et al, 2016) have shown better GOM recovery on CEM material compared to potassium chloride (KCl)-coated denuder methods.…”

Deciphering potential chemical compounds of gaseous oxidized mercury in Florida, USA

“…Observations from the three GOM sampling methods (Tekran ® , and nylon and cation exchange membranes) showed higher GOM concentrations in spring relative to other seasons (Table 1). Concentrations of GOM measured by cation-exchange membranes in the active system were significantly (p value < 0.05, paired-t test) higher than those measured by Tekran ® KCl-coated denuder and nylon membranes, both of which have been reported to be influenced by relative humidity (Huang and Gustin, 2015b;Gustin et al, 2015). Mean cation-exchange membrane concentrations were higher than Tekran ® -derived GOM by 14, 48, 11, and 13 times in the spring, summer, fall, and winter, respectively.…”

“…Because of the low GOM concentrations and influence of humidity on the nylon membrane measurements (Huang and Gustin, 2015b), GOM compounds were identified only in one summertime sample as HgN 2 O 6 q H 2 O. During this time, measured GOM dry deposition was ∼ 6 times higher than both modeled results, and considering the Tekran ® correction factor of 3, membranebased HgN 2 O 6 q H 2 O dry-deposition flux was ∼ 18 times higher than the Tekran ® -model-based value.…”

Historical (1850–2010) mercury stable isotope inventory from anthropogenic sources to the atmosphere

“…Such an inventory is the first step in incorporating Hg isotopes into state-of-the-science global Hg cycling models. This would in turn help constrain current poorly-known Hg fluxes and transformations such as volcanic Hg emissions, Hg wet/dry deposition, atmospheric Hg 0 oxidation and Hg II reduction, marine and terrestrial Hg re-emissions (Engstrom et al, 2014;Holmes et al, 2010;Huang and Gustin, 2015;Lindberg et al, 2007;Obrist et al, 2014;Pongprueksa et al, 2008;Pyle and Mather, 2003;Streets et al, 2011).…”