Mercury and Reactive Halogens:  The Thermochemistry of Hg + {Cl<sub>2</sub>, Br<sub>2</sub>, BrCl, ClO, and BrO}

Balabanov, Nikolai B.; Peterson, Kirk A.

doi:10.1021/jp035547p

Cited by 89 publications

(86 citation statements)

References 65 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: 93%

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: 93%

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

“…The Cl atom can also oxidize Hg 0 to produce HgCl (Balabanov and Peterson, 2003;Donohoue et al, 2005). found that a broad range of radical oxidants could oxidize HgBr and HgCl including Y ≡ NO 2 and HO 2 , the most abundant atmospheric radicals, as well as Y ≡ BrO, ClO, and Cl.…”

Section: Chemical Mechanismmentioning

confidence: 99%

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

et al. 2017

View full text Add to dashboard Cite

Abstract. Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg 0 . Oxidation to water-soluble Hg II plays a major role in Hg deposition to ecosystems. Here, we implement a new mechanism for atmospheric Hg 0 / Hg II redox chemistry in the GEOS-Chem global model and examine the implications for the global atmospheric Hg budget and deposition patterns. Our simulation includes a new coupling of GEOS-Chem to an ocean general circulation model (MITgcm), enabling a global 3-D representation of atmosphereocean Hg 0 / Hg II cycling. We find that atomic bromine (Br) of marine organobromine origin is the main atmospheric Hg 0 oxidant and that second-stage HgBr oxidation is mainly by the NO 2 and HO 2 radicals. The resulting chemical lifetime of tropospheric Hg 0 against oxidation is 2.7 months, shorter than in previous models. Fast Hg II atmospheric reduction must occur in order to match the ∼ 6-month lifetime of Hg against deposition implied by the observed atmospheric variability of total gaseous mercury (TGM ≡ Hg 0 + Hg II (g)). We implement this reduction in GEOS-Chem as photolysis of aqueous-phase Hg II -organic complexes in aerosols and clouds, resulting in a TGM lifetime of 5.2 months against deposition and matching both mean observed TGM and its variability. Model sensitivity analysis shows that the interhemispheric gradient of TGM, previously used to infer a longer Hg lifetime against deposition, is misleading because Southern Hemisphere Hg mainly originates from oceanic emissions rather than transport from the Northern Hemisphere.The model reproduces the observed seasonal TGM variation at northern midlatitudes (maximum in February, minimum in September) driven by chemistry and oceanic evasion, but it does not reproduce the lack of seasonality observed at southern hemispheric marine sites. Aircraft observations in the lowermost stratosphere show a strong TGM-ozone relationship indicative of fast Hg 0 oxidation, but we show that this relationship provides only a weak test of Hg chemistry because it is also influenced by mixing. The model reproduces observed Hg wet deposition fluxes over North America, Europe, and China with little bias (0-30 %). It reproduces qualitatively the observed maximum in US deposition around the Gulf of Mexico, reflecting a combination of deep convection and availability of NO 2 and HO 2 radicals for second-stage HgBr oxidation. However, the magnitude of this maximum is underestimated. The relatively low observed Hg wet deposition over rural China is attributed to fast Hg II reduction in the presence of high organic aerosol concentrations. We find that 80 % of Hg II deposition is to the global oceans, reflecting the marine origin of Br and low concentrations of organic aerosols for Hg II reduction. Most of that deposition takes place to the tropical oceans due to the availability of HO 2 and NO 2 for second-stage HgBr oxidation.

show abstract

“…There have been several quantum chemical studies of mercury compounds, [18,19, where those of the Peterson group [18,[21][22][23][24][25][26][27][28] and those by Tossell [29][30][31][32][33] are most noteworthy. Each of these investigations focused on selected mercury compounds HgX; however none of them attempted a comprehensive study of mercury bonding by varying X systematically within the periodic table.…”

Section: Bdea C H T U N G T R E N N U N G (Hgx)àbdea C H T U N G T R mentioning

confidence: 99%

“…However this reaction sequence can be excluded on the basis of theoretical calculations carried out herein and in the studies of others. [18][19][20][21][22][23][24][25][26][27][28][29][30] The reaction of elemental Hg with OH radicals is more likely considering a reaction energy of 12 kcal mol…”

mentioning

confidence: 99%

Bonding in Mercury Molecules Described by the Normalized Elimination of the Small Component and Coupled Cluster Theory

2008

View full text Add to dashboard Cite

Bond dissociation energies (BDEs) of neutral HgX and cationic HgX+ molecules range from less than a kcal mol−1 to as much as 60 kcal mol−1. Using NESC/CCSD(T) [normalized elimination of the small component and coupled‐cluster theory with all single and double excitations and a perturbative treatment of the triple excitations] in combination with triple‐zeta basis sets, bonding in 28 mercury molecules HgX (X=H, Li, Na, K, Rb, CH3, SiH3, GeH3, SnH3, NH2, PH2, AsH2, SbH2, OH, SH, SeH, TeH, O, S, Se, Te, F, Cl, Br, I, CN, CF3, OCF3) and their corresponding 28 cations is investigated. Mercury undergoes weak covalent bonding with its partner X in most cases (exceptions: X=alkali atoms, which lead to van der Waals bonding) although the BDEs are mostly smaller than 12 kcal mol−1. Bonding is weakened by 1) a singly occupied destabilized σ*‐HOMO and 2) lone pair repulsion. The magnitude of σ*‐destabilization can be determined from the energy difference BDE(HgX)−BDE(HgX+), which is largest for bonding partners from groups IVb and Vb of the periodic table (up to 80 kcal mol−1). BDEs can be enlarged by charge transfer from Hg and increased HgX ionic bonding, provided the bonding partner of Hg is sufficiently electronegative. The fine‐tuning of covalent and ionic bonding, σ‐destabilization, and lone‐pair repulsion occurs via relativistic effects where 6s AO contraction and 5d AO expansion are decisive. Lone pair repulsion involving the mercury 5d AOs plays an important role in the case of some mercury chalcogenides HgE (E=O, Te) where it leads to 3Π rather than 1Σ+ ground states. However, both HgE(3Π) and HgE(1Σ+) should not be experimentally detectable under normal conditions, which is in contrast to experimental predictions suggesting BDE values for HgE between 30 and 53 kcal mol−1. The results of this work are discussed with regard to their relevance for mercury bonding in general, the chemistry of mercury, and reactions of elemental Hg in the atmosphere.

show abstract

Mercury and Reactive Halogens: The Thermochemistry of Hg + {Cl₂, Br₂, BrCl, ClO, and BrO}

Cited by 89 publications

References 65 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

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

Bonding in Mercury Molecules Described by the Normalized Elimination of the Small Component and Coupled Cluster Theory

Contact Info

Product

Resources

About

Mercury and Reactive Halogens: The Thermochemistry of Hg + {Cl2, Br2, BrCl, ClO, and BrO}

Cited by 89 publications

References 65 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

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

Bonding in Mercury Molecules Described by the Normalized Elimination of the Small Component and Coupled Cluster Theory

Contact Info

Product

Resources

About

Mercury and Reactive Halogens: The Thermochemistry of Hg + {Cl₂, Br₂, BrCl, ClO, and BrO}