Calculation of the Energetics for Oxidation of Gas-Phase Elemental Hg by Br and BrO

Tossell, J. A.

doi:10.1021/jp030390m

Cited by 83 publications

(80 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Field studies (Peleg et al, 2007;Lindberg et al, 2002), laboratory studies (Donohoue et al, 2006), quantum calculations (Goodsite et al, 2004;Cremer et al, 2008;Balabanov et al, 2003;Tossell, 2003), and modeling studies (Holmes et al, 2006(Holmes et al, , 2009Selin et al, 2007) consistently suggest 2 Authors wish to note that the use of geometric AMFs for this calculation is a simplification of the radiative transfer process. We have carried out full radiative transfer calculations that varied in the assumptions about the BrO vertical distribution and find this simplification equally represents the uncertainty arising from the lack of knowledge about the true BrO vertical distribution aloft.…”

Section: Measurement Resultsmentioning

confidence: 94%

The CU ground MAX-DOAS instrument: characterization of RMS noise limitations and first measurements near Pensacola, FL of BrO, IO, and CHOCHO

et al. 2011

View full text Add to dashboard Cite

Abstract. We designed and assembled the University of Colorado Ground Multi AXis Differential Optical Absorption Spectroscopy (CU GMAX-DOAS) instrument to retrieve bromine oxide (BrO), iodine oxide (IO), formaldehyde (HCHO), glyoxal (CHOCHO), nitrogen dioxide (NO 2 ) and the oxygen dimer (O 4 ) in the coastal atmosphere of the Gulf of Mexico. The detection sensitivity of DOAS measurements is proportional to the root mean square (RMS) of the residual spectrum that remains after all absorbers have been subtracted. Here we describe the CU GMAX-DOAS instrument and demonstrate that the hardware is capable of attaining RMS of ∼6 × 10 −6 from solar stray light noise tests using high photon count spectra (compatible within a factor of two with photon shot noise).Laboratory tests revealed two critical instrument properties that, in practice, can limit the RMS: (1) detector non-linearity noise, RMS NLin , and (2) temperature fluctuations that cause variations in optical resolution (full width at half the maximum, FWHM, of atomic emission lines) and give rise to optical resolution noise, RMS FWHM . The nonlinearity of our detector is low (∼10 −2 ) yet -unless actively controlled -is sufficiently large to create RMS NLin of up to 2 × 10 −4 . The optical resolution is sensitive to temperature changes (0.03 detector pixels • C −1 at 334 nm), and temperature variations of 0.1 • C can cause RMS FWHM of ∼1 × 10 −4 . Both factors were actively addressed in the design of the CU GMAX-DOAS instrument. With an integration time of 60 s Correspondence to: R. Volkamer (rainer.volkamer@colorado.edu) the instrument can reach RMS noise of 3 × 10 −5 , and typical RMS in field measurements ranged from 6 × 10 −5 to 1.4 × 10 −4 .The CU GMAX-DOAS was set up at a coastal site near Pensacola, Florida, where we detected BrO, IO and CHO-CHO in the marine boundary layer (MBL), with daytime average tropospheric vertical column densities (average of data above the detection limit), VCDs, of ∼2 × 10 13 molec cm −2 , 8 × 10 12 molec cm −2 and 4 × 10 14 molec cm −2 , respectively. HCHO and NO 2 were also detected with typical MBL VCDs of 1 × 10 16 and 3 × 10 15 molec cm −2 . These are the first measurements of BrO, IO and CHOCHO over the Gulf of Mexico. The atmospheric implications of these observations for elevated mercury wet deposition rates in this area are briefly discussed. The CU GMAX-DOAS has great potential to investigate RMS-limited problems, like the abundance and variability of trace gases in the MBL and possibly the free troposphere (FT).

show abstract

Section: Measurement Resultsmentioning

confidence: 94%

The CU ground MAX-DOAS instrument: characterization of RMS noise limitations and first measurements near Pensacola, FL of BrO, IO, and CHOCHO

et al. 2011

View full text Add to dashboard Cite

show abstract

“…GEM is oxidized in the atmosphere by OH radicals. The rate constant of the reaction is from Sommar et al (2001) but scaled down by a coefficient of 0.34 to take into account possible dissociation/reduction reactions (Tossell et al, 2003;Goodsite et al, 2004). The gaseous oxidation of mercury by bromine is applied in polar regions using reaction rate constants from Donohoue et al (2006), Dibble et al (2012), and Goodsite et al (2004).…”

Section: Gem-mach-hgmentioning

confidence: 99%

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

et al. 2017

View full text Add to dashboard Cite

Abstract. Atmospheric chemistry and transport of mercury play a key role in the global mercury cycle. However, there are still considerable knowledge gaps concerning the fate of mercury in the atmosphere. This is the second part of a model intercomparison study investigating the impact of atmospheric chemistry and emissions on mercury in the atmosphere. While the first study focused on ground-based observations of mercury concentration and deposition, here we investigate the vertical and interhemispheric distribution and speciation of mercury from the planetary boundary layer to the lower stratosphere. So far, there have been few model studies investigating the vertical distribution of mercury, mostly focusing on single aircraft campaigns. Here, we present a first comprehensive analysis based on various aircraft observations in Europe, North America, and on intercontinental flights.The investigated models proved to be able to reproduce the distribution of total and elemental mercury concentrations in the troposphere including interhemispheric trends. One key aspect of the study is the investigation of mercury oxidation in the troposphere. We found that different chemistry schemes were better at reproducing observed oxidized mercury patterns depending on altitude. High concentrations of oxidized mercury in the upper troposphere could be reproduced with oxidation by bromine while elevated concentrations in the lower troposphere were better reproduced by OH and ozone chemistry. However, the results were not always conclusive as the physical and chemical parameterizations in the chemistry transport models also proved to have a substantial impact on model results.

show abstract

“…GEM (Hg(0)) is oxidized to GOM and PBM in the atmosphere by OH and bromine (Sommar et al, 2001;Donohoue et al, 2006;Dibble et al, 2012;Goodside et al, 2004). No aqueous-phase reduction reactions are included; however, the OH reaction rate constant is scaled down by a coefficient of 0.34 to take into account dissociation reactions (Tossell, 2003;35 Goodsite et al, 2004 (Platt and Janssen, 1995). GEM-MACH includes a full tropospheric chemistry reaction mechanism, and particle chemistry and microphysics (Makar et al, 2015a,b); the OH concentrations are used for oxidation of GEM and are derived from this oxidation mechanism.…”

Section: Gem-mach-hg Is the Mercury Version Of The Eccc's Current Opementioning

confidence: 99%

How important is biomass burning in Canada to mercury contamination?

Fraser¹,

Dastoor²,

Ryjkov³

2017

Preprint

View full text Add to dashboard Cite

Abstract.Wildfire frequency has increased in past four decades in Canada, and is expected to increase in future as a result of climate change (Wotton et. al. 2010). Mercury (Hg) emissions from biomass burning are known to be significant; however, the impact of biomass burning on air concentration and deposition fluxes in Canada has not been previously quantified. We use 10 estimates of burned biomass from FINN (Fire Inventory from NCAR) and vegetation-specific Emission Factors (EFs) of mercury to investigate the spatiotemporal variability of Hg emissions in Canada. We use Environment and Climate Change Canada's GEM-MACH-Hg (Global Environmental Multi-scale, Modelling Air quality and Chemistry model, mercury version) to quantify the impact of biomass burning in Canada on spatiotemporal variability of air concentrations and deposition fluxes of mercury in Canada. We use North American gaseous elemental mercury (GEM) observations (2010)(2011)(2012)(2013)(2014)(2015), 15 and an inversion technique to optimize the emission factors for GEM for five vegetation types represented in North American fires to constrain the biomass burning impacts of mercury. We use three biomass burning Hg emissions scenarios in Canada to conduct three sets of model simulations for 2010-2015: two scenarios where Hg is emitted only as GEM using literature or optimized EFs, and a third scenario where Hg is emitted as GEM using literature EFs and particle bound mercury (PBM) emitted using the average GEM/PBM ratio from lab measurements. The three biomass burning emission scenarios represent the range of 20 possible values for the impacts of Hg emissions from biomass burning in Canada on Hg concentration and deposition.We find total biomass burning Hg emissions to be highly variable from year to year, and estimate average 2010-2015 total atmospheric biomass burning emissions of Hg in Canada to be between 6-14 t during the biomass burning season (i.e., from May to September), which is 3 -7 times the mercury emission from anthropogenic sources in Canada for this period. On average, 65% of the emissions occur in the provinces west of Ontario. We find that while emissions from biomass burning have a small 25 impact on surface air concentrations of GEM averaged over individual provinces/territories, the impact at individual sites can be as high as 95% during burning events. We estimate average annual mercury deposition from biomass burning in Canada to be between 0.3 -2.8 t, compared to 0.14 t of mercury deposition from anthropogenic sources during the biomass burning season in Canada. Compared to the biomass burning emissions, the relative impact of fires on mercury deposition is shifted eastward, with on average 54% percent of the deposition occurring in provinces west of Ontario. While the relative contribution of Canadian 30 biomass burning to the total mercury deposition over each province/territory is no more than 9% between 2010-2015, the local contribution in some locations (including areas downwind of biomass burning) can be as high as...

show abstract

Calculation of the Energetics for Oxidation of Gas-Phase Elemental Hg by Br and BrO

Cited by 83 publications

References 40 publications

The CU ground MAX-DOAS instrument: characterization of RMS noise limitations and first measurements near Pensacola, FL of BrO, IO, and CHOCHO

The CU ground MAX-DOAS instrument: characterization of RMS noise limitations and first measurements near Pensacola, FL of BrO, IO, and CHOCHO

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

How important is biomass burning in Canada to mercury contamination?

Contact Info

Product

Resources

About