A practical uncertainty budget for ambient mercury vapour measurement

Brown, Richard; Brown, Andrew S.; Yardley, R E; Corns, Warren T.; Stockwell, Peter

doi:10.1016/j.atmosenv.2007.12.012

Cited by 41 publications

(55 citation statements)

References 14 publications

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“…The detection limit of the Tekran 2537A is <0.1 ng m −3 (Temme et al, 2007). Uncertainties in the measured concentrations have been estimated at 5-17% (95% CL) based on both field intercomparisons (Aspmo et al, 2005;Ebinghaus et al, 1999) and propagating errors in the concentration calculation (Brown et al, 2008;Temme et al, 2007). Hourly mean concentrations were calculated for this analysis, requiring 25% completeness.…”

Section: Methodsmentioning

confidence: 99%

Trends in long-term gaseous mercury observations in the Arctic and effects of temperature and other atmospheric conditions

Cole

Steffen

2010

Atmos. Chem. Phys.

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Abstract. Gaseous elemental mercury (GEM) measurements at Alert, Canada, from 1995 to 2007 were analyzed for statistical time trends and for correlations with meteorological and climate data. A significant decreasing trend in annual GEM concentration is reported at Alert, with an estimated slope of −0.0086 ng m −3 yr −1 (−0.6% yr −1 ) over this 13-year period. It is shown that there has been a shift in the month of minimum mean GEM concentration from May to April due to a change in the timing of springtime atmospheric mercury depletion events (AMDEs). These AMDEs are found to decrease with increasing local temperature within each month, both at Alert and at Amderma, Russia. These results support the temperature dependence suggested by previous experimental results and theoretical kinetic calculations on both bromine generation and mercury oxidation and highlight the potential for changes in Arctic mercury chemistry with climate. A correlation between total monthly AMDEs at Alert and the Polar/Eurasian Teleconnection Index was observed only in March, perhaps due to higher GEM inputs in early spring in those years with a weak polar vortex. A correlation of AMDEs at Alert with wind direction supports the origin of mercury depletion events over the Arctic Ocean, in agreement with a previous trajectory study of ozone depletion events. Interannual variability in total monthly depletion event frequency at Alert does not appear to correlate significantly with total or first-year northern hemispheric sea ice area or with other major teleconnection patterns. Nor do AMDEs at either Alert or Amderma correlate with local wind speed, as might be expected if depletion events are sustained by stable, low-turbulence atmospheric conditions. The data presented here -both the change in Correspondence to: A. S. Cole (amanda.cole@ec.gc.ca) timing of depletion events and their relationship with temperature -can be used as additional constraints to improve the ability of models to predict the cycling and deposition of mercury in the Arctic.

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Section: Methodsmentioning

confidence: 99%

Trends in long-term gaseous mercury observations in the Arctic and effects of temperature and other atmospheric conditions

Cole

Steffen

2010

Atmos. Chem. Phys.

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“…Since low concentrations (in the pg m −3 range) are typically observed for Hg 2+ and Hg p , a thorough assessment of linearity is especially important for these species. Hg 0 measurement uncertainty was reported to be 12-20 % (2σ ), which has direct implications for Hg 2+ and Hg p , since these species are ultimately detected as Hg 0 (Aspmo et al, 2005;Temme et al, 2007 andBrown et al, 2008).…”

Section: Operational Uncertaintiesmentioning

confidence: 99%

Evaluation of discrepancy between measured and modelled oxidized mercury species

et al. 2013

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Abstract. L. Zhang et al. (2012), in a recent report, compared model estimates with new observations of oxidized and particulate mercury species (Hg2+ and Hgp) in the Great Lakes region and found that the sum of Hg2+ and Hgp varied between a factor of 2 to 10 between measurements and model. They suggested too high emission inputs as Hg2+ and too fast oxidative conversion of Hg0 to Hg2+ and Hgp as possible causes. This study quantitatively explores measurement uncertainties in detail. These include sampling efficiency, composition of sample, interfering species and calibration errors. Model (Global/Regional Atmospheric Heavy Metals Model – GRAHM) sensitivity experiments are used to examine the consistency between various Hg measurements and speciation of Hg near emission sources to better understand the discrepancies between modelled and measured concentrations of Hg2+ and Hgp. We find that the ratio of Hg0, Hg2+ and Hgp in the emission inventories, measurements of surface air concentrations of oxidized Hg and measurements of wet deposition are currently inconsistent with each other in the vicinity of emission sources. Current speciation of Hg emissions suggests higher concentrations of Hg2+ in air and in precipitation near emission sources; however, measured air concentrations of Hg2+ and measured concentrations of Hg in precipitation are not found to be significantly elevated near emission sources compared to the remote regions. The averaged unbiased root mean square error (RMSE) between simulated and observed concentrations of Hg2+ is found to be reduced by 42% and for Hgp reduced by 40% for 21 North American sites investigated, when a ratio for Hg0 : Hg2+ : Hgp in the emissions is changed from 50 : 40 : 10 (as specified in the original inventories) to 90 : 8 : 2. Unbiased RMSE reductions near emissions sources in the eastern United States and Canada are found to be reduced by up to 58% for Hg2+. Significant improvement in the model simulated spatial distribution of wet deposition of mercury in North America is noticed with the modified Hg emission speciation. Measurement-related uncertainties leading to lower estimation of Hg2+ concentrations are 86%. Uncertainties yielding either to higher or lower Hg2+ concentrations are found to be 36%. Finally, anthropogenic emission uncertainties are 106% for Hg2+. Thus it appears that the identified uncertainties for model estimates related to mercury speciation near sources, uncertainties in measurement methodology and uncertainties in emissions can close the gap between modelled and observed estimates of oxidized mercury found in L. Zhang et al. (2012). Model sensitivity simulations show that the measured concentrations of oxidized mercury, in general, are too low to be consistent with measured wet deposition fluxes in North America. Better emission inventories (with respect to speciation), better techniques for measurements of oxidized species and knowledge of mercury reduction reactions in different environments (including in-plume) in all phases are needed for improving the mercury models.

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“…A comprehensive analysis of all random and systematic uncertainties involved in a single manual determination of mercury concentration in air is given by Brown et al (2008), who estimated the combined relative uncertainty to be 16.7 % at the concentration of 1.2 ng m −3 . This uncertainty includes the uncertainty from different published mercury vapour pressure curves and can be reduced to 12.6 % when one vapour pressure curve is accepted to be correct, as is the case here.…”

Section: F Slemr Et Al: Comparison Of Mercury Concentrations Measurmentioning

confidence: 99%

Comparison of mercury concentrations measured at several sites in the Southern Hemisphere

et al. 2015

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Abstract. Our knowledge of the distribution of mercury concentrations in air of the Southern Hemisphere was until recently based mostly on intermittent measurements made during ship cruises. In the last few years continuous mercury monitoring has commenced at several sites in the Southern Hemisphere, providing new and more refined information. In this paper we compare mercury measurements at several remote sites in the Southern Hemisphere made over a period of at least 1 year at each location. Averages of monthly medians show similar although small seasonal variations at both Cape Point and Amsterdam Island. A pronounced seasonal variation at Troll research station in Antarctica is due to frequent mercury depletion events in the austral spring. Due to large scatter and large standard deviations of monthly average median mercury concentrations at Cape Grim, no systematic seasonal variation could be found there. Nevertheless, the annual average mercury concentrations at all sites during the 2007-2013 period varied only between 0.85 and 1.05 ng m −3 . Part of this variability is likely due to systematic measurement uncertainties which we propose can be further reduced by improved calibration procedures. We conclude that mercury is much more uniformly distributed throughout the Southern Hemisphere than the distributions suggested by measurements made onboard ships. This finding implies that smaller trends can be detected in shorter time periods. We also report a change in the trend sign at Cape Point from decreasing mercury concentrations in 1996-2004 to increasing concentrations since 2007.

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A practical uncertainty budget for ambient mercury vapour measurement

Cited by 41 publications

References 14 publications

Trends in long-term gaseous mercury observations in the Arctic and effects of temperature and other atmospheric conditions

Trends in long-term gaseous mercury observations in the Arctic and effects of temperature and other atmospheric conditions

Evaluation of discrepancy between measured and modelled oxidized mercury species

Comparison of mercury concentrations measured at several sites in the Southern Hemisphere

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