A Survey of Mercury in Air and Precipitation across Canada: Patterns and Trends

Abstract

Atmospheric mercury (Hg) measurements from across Canada were compiled and analysed as part of a national Hg science assessment. Here we update long-term trends of Hg in air and precipitation, and present more extensive measurements on patterns and trends in speciated Hg species (gaseous elemental mercury-GEM, reactive gaseous mercury-RGM, and total particulate mercury on particles <2.5 μm-TPM 2.5 ) at several sites. A spatial analysis across Canada revealed higher air concentrations and wet OPEN ACCESSAtmosphere 2014, 5 636 deposition of Hg in the vicinity of local and regional emission sources, and lower air concentrations of Hg at mid-latitude maritime sites compared to continental sites. Diel and seasonal patterns in atmospheric GEM, RGM and TPM 2.5 concentrations reflected differences in patterns of anthropogenic emissions, photo-induced surface emissions, chemistry, deposition and mixing. Concentrations of GEM decreased at rates ranging from −0.9% to −3.3% per year at all sites where measurements began in the 1990s. Concentrations of total Hg in precipitation declined up to 3.7% yr −1. Trends in RGM and TPM 2.5 were less clear due to shorter measurement periods and low concentrations, however, in spring at the high Arctic site (Alert) when RGM and TPM 2.5 concentrations were high, concentrations of both increased by 7%-10% per year.

Improved methods for signal processing in measurements of mercury by Tekran&lt;sup&gt;®&lt;/sup&gt; 2537A and 2537B instruments

“…S5a. Similarly, median concentrations of GOM and/or PBM measured at 10 sites in Canada during the years 2002-2011 were typically < 5 pg m −3 (Cole et al, 2014), corresponding with sample loadings of 3-9 pg. The corresponding median signal processing bias would be within −19 and −8 %, respectively, based on the fit in Fig.…”

Atmospheric mercury in the Southern Hemisphere tropics: seasonal and diurnal variations and influence of inter-hemispheric transport

“…Within tropical regions, wet deposition has been shown to be a significant pathway for mercury from the atmosphere to both oceanic and terrestrial ecosystems, even in relatively low-mercury air and despite the low solubility of mercury in its elemental form (Fostier et al, 2000;Costa et al, 2012;Hansen and Gay, 2013;Soerensen et al, 2014;Shanley et al, 2015). Mercury "rainout" -or the tendency for mercury rainwater loading to decrease with increasing precipitation -has also been demonstrated in Mercury Deposition Network (MDN) data in North America (Glass and Sorensen, 1999;Prestbo and Gay, 2009) and positive correlations between GEM (TGM) and rainwater mercury have been reported in MDN data (GEM; Cole et al, 2014) and at Cape Point, South Africa (TGM; Brunke et al, 2016). Re-emission of any deposited mercury is likely to be inhibited throughout the wet season, as it has been shown that GEM emission from background mercury soils is suppressed when the soils are saturated (Briggs and Gustin, 2013).…”

Global evaluation and calibration of a passive air sampler for gaseous mercury

“…The atmospheric 90 lifetime of GOM due to reduction and deposition is on the order of days to weeks (Ariya et al, 2015;Horowitz et al, 2017;Shah et al, 2016). Although uncertainties remain, the shorter atmospheric lifetime and higher deposition fluxes of GOM translate to GEM making up the majority of TGM in most places (typically >95%) (Cole et al, 2014;Driscoll et al, 2013;Rutter et al, 2009;Slemr et al, 2015). As such any uncertainty related to the uptake of GOM by the PASs is 95 likely small.…”