Identifying and evaluating urban mercury emission sources through passive sampler-based mapping of atmospheric concentrations

Abstract

Beyond emissions from coal-fired power generation, urban sources of mercury (Hg) to the atmosphere, especially minor fugitive sources, are relatively poorly characterized. To identify urban sources of fugitive Hg emissions, passive air samplers (PASs) were deployed for periods of 4-6 weeks in the summer of 2016 at 145 sites across the Greater Toronto Area (GTA). PASs were also deployed along transects of increasing distance from five sites listed as Hg sources in the National Pollution Release Inventory (NPRI) within or near the GTA. Mean gaseous Hg concentrations in downtown Toronto (1.77 ± 0.28 ng m −3 ) are slightly, but significantly elevated relative to other parts of the GTA (1.42 ± 0.20 ng m −3 ). Similarly, concentrations at sites close to waste/recycling (1.61 ± 0.22 ng m −3 ) and hospitals/dental facilities (1.63 ± 0.21 ng m −3 ) are significantly higher than at sites presumably distant from potential sources (1.37 ± 0.20 ng m −3 ). Gaseous Hg concentrations are elevated near four of five NPRI source sites, but not near a wastewater treatment plant. Measured or predicted concentrations (using extrapolated transect relationships) close to known Hg sources do not correlate with reported NPRI emissions. For example, the Hg disposal company Aevitas Inc. has the lowest reported NPRI emissions (0.11 kg yr −1 ) among the five sources, but measured (12.3 ng m −3 ) and predicted (60.0 ng m −3 ) concentrations outside the facility are the highest. The PAS's ability to precisely and accurately discriminate small differences in gaseous Hg concentration (<0.2 ng m −3 ) at and near global background concentrations enables the mapping of the spatial concentration variability and the identification of fugitive Hg emission sources.

Ambient Mercury Observations near a Coal-Fired Power Plant in a Western U.S. Urban Area

“…In addition to previously deposited Hg from local or regional sources in the Colorado Front Range, one potentially interesting source of surface Hg flux that is adjacent to our measurement site is a 400-acre abandoned gold and silver mine tailings area (Gold Hill Mesa), approximately 1 km west-northwest of the monitoring site (Figure 1) [37], which May contain elevated levels of Hg and could contribute to elevated surface emissions [38]. Other potential sources of Hg in urban areas could include relatively low-level non-point emissions from buildings, waste centers, hospitals/dental facilities, or roads [39–41].…”

Where there is smoke there is mercury: Assessing boreal forest fire mercury emissions using aircraft and highlighting uncertainties associated with upscaling emissions estimates

“…was observed in the current study (McLagan et al, 2018;. Based on the estimated 0.5 Hz GEM concentration data from the GLP fires, a logarithmic relationship (R 2 = 0.998; Figure 4(b)) was used to project GEM concentrations at the wildfire source as it produced a stronger fit than a power relationship (R 2 = 0.976).…”

“…This data was also used to generate the three-dimensional GEM concentration flight path in Fig 2(a). 460 McLagan et al (2018; used power relationships between GEM concentrations and distance from source to estimate the concentrations at (1 m from) point sources. In these studies, passive https://doi.org/10.5194/acp-2020-1119 Preprint.…”

Where there is smoke there is mercury: Assessing boreal forest fire mercury emissions using aircraft and highlighting uncertainties associated with upscaling emissions estimates

“…2a. McLagan et al (2018McLagan et al ( , 2019) used power relationships between GEM concentrations and distance from source to estimate the concentrations at (1 m from) point sources. In these studies, passive samplers were used to measure GEM concentrations, which involved longer deployments and provided time-averaged concentrations that were unable to ensure measurements were always downwind of source.…”