Detection of mercury in air in the presence of chlorine and water vapor

Menke, R; Wallis, George

doi:10.1080/15298668091424465

Cited by 33 publications

(14 citation statements)

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“…This trend is similar to the Cl 2 + Hg 0 (g) data of Menke and Wallis. 16 In the previous study of reaction 1 by Hall, 20 there was evidence for heterogeneous ozone chemistry. Hall found the rate of Hg 0 (g) loss was equal to k net [Hg 0 (g)][O 3 ] b , where b = 0.81.…”

Section: Kinetic Results and Potential Mechanismsmentioning

confidence: 93%

“…Among these oxidants considered, ozone was regarded as the among the most important mercury-depleting compounds in the troposphere outside marine or polar regions. 1 Previous studies have shown that the apparent rate constant for the oxidation of Hg 0 (g) can be increased if water is present; Menke and Wallis 16 found the rate of mercury oxidation by chlorine will triple when increasing RH to 80%. A later study by Lindqvist and Iverfeldt 17 observed that the presence of liquid water and ozone together will enhance deposition of Hg 0 (g).…”

Section: Introductionmentioning

confidence: 99%

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Effects of relative humidity and CO(g) on the O3-initiated oxidation reaction of Hg0(g): kinetic & product studies

Snider

Raofie

Ariya

2008

Phys. Chem. Chem. Phys.

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Ozone is assumed to be the predominant tropospheric oxidant of gaseous elemental mercury (Hg0(g)), defining mercury global atmospheric lifetime. In this study we have examined the effects of two atmospherically relevant polar compounds, H2O(g) and CO(g), on the absolute rate coefficient of the O3-initiated oxidation of Hg0(g), at 296 +/- 2 K using gas chromatography coupled to mass spectrometry (GC-MS). In CO-added experiments, we observed a significant increase in the reaction rate that could be explained by pure gas-phase chemistry. In contrast, we found the apparent rate constant, k(net), varied with the surface-to-volume ratio (0.6 to 5.5 L flasks) in water-added experiments. We have observed small increases in k(net) for nonzero relative humidity, RH < 100%, but substantial increase at RH > or = 100%. Product studies were performed using mass spectrometry and high resolution transmission electron microscopy coupled to an electron dispersive spectrometer (HRTEM-EDS). Our results give evidence for enhanced chain growth of HgO(s) on a carbon grid at RH = 50%. A water/surface/ozone independent ozone oxidation rate is estimated to be (6.2 +/- (1.1; tsigma/ radicaln) x 10(-19) cm3 molecule(-1) s(-1). The total uncertainty associated with the ensemble of experiments amount to approximately < or = 20%. The atmospheric implications of our results and the effect of an added reaction partner in homogeneous and heterogeneous atmospheric chemistry will be discussed.

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Section: Kinetic Results and Potential Mechanismsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Effects of relative humidity and CO(g) on the O3-initiated oxidation reaction of Hg0(g): kinetic & product studies

Snider

Raofie

Ariya

2008

Phys. Chem. Chem. Phys.

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“…For various concentrations of Hg 0 (g) and Cl2(g) ,rate constants of 9.8-5010 -18 cm 3 molecules -1 s -1 1have been reported (Sumner et al, 2005). Earlier kinetic studies (Medhekaret al, 1979;Menke and Wallis, 1980;Schroeder et al, 1991;Seignuer et al, 1994;Skare and Hohansson, 1992;Sliger et al,2000) yielded rate…”

Section: A14 Reaction With Cl2(g) Br2(g) I2(g) and F2(g)mentioning

confidence: 95%

A review of uncertainties in atmospheric modeling of mercury chemistry I. Uncertainties in existing kinetic parameters – Fundamental limitations and the importance of heterogeneous chemistry

Subir

Ariya

Dastoor

2011

Atmospheric Environment

146

152

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Mercury and its related compounds are widely recognized as global pollutants. The accurate atmospheric modeling of its transport and fate has been the subject of much research throughout the last decade. Atmospheric gas, aqueous and heterogeneous chemistry are expected to occur for Hg-containing specie sand accurate implementation of their chemical parameters is essential for realistic modeling of mercury cycling. Although significant progress has been made, the current state of knowledge of mercury chemistry exhibits numerous uncertainties. The objective of this two-part review is to explore the sources of uncertainty from the viewpoint of mercury chemistry. In this first part, we assess the discrepancy that exists in the currently available mercury kinetic parameters for the gas and aqueous phases. Theoretical and experimental approaches of rate constant determination exhibit various levels of limitation and accuracy. We present an overview of the available techniques and the assumptions and shortcomings associated with these methods in order to assist the atmospheric modellers. We review specific mercury oxidation and reduction reactions that have been investigated and are commonly implemented in mercury models with respect to the uncertainties associated with them. We reveal that for most of these mercury reactions our current state of knowledge reflects a lack of proper under-standing of their mechanisms. Atmospheric heterogeneity is a topic of great importance and we elaborate upon it in part II of this review.

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“…Our findings below are in agreement with the results of Fontijn and Hranisavljevic. Using Menke and Wallis' experimental results, 18 Schroeder et al 21 calculated a rate constant, providing an upper limit of 2.4 × 10 8 cm 3 mol −1 s −1 . However, they stated that the actual reaction is not entirely described by Hg + Cl 2 → HgCl 2 .…”

Section: ■ Introductionmentioning

confidence: 99%

Mercury Oxidation via Chlorine, Bromine, and Iodine under Atmospheric Conditions: Thermochemistry and Kinetics

2014

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Emissions of gaseous mercury from combustion sources are the major source of Hg in the atmosphere and in environmental waters and soils. Reactions of Hg(o)(g) with halogens are of interest because they relate to mercury and ozone depletion events in the Antarctic and Arctic early spring ozone hole events, and the formation of Hg-halides (HgX2) is a method for removal of mercury from power generation systems. Thermochemistry and kinetics from published theoretical and experimental studies in the literature and from computational chemistry are utilized to compile a mechanism of the reactions considered as contributors to the formation of HgX2 (X = Cl, Br, I) to understand the reaction paths and mechanisms under atmospheric conditions. Elementary reaction mechanisms are assembled and evaluated using thermochemistry for all species and microscopic reversibility for all reactions. Temperature and pressure dependence is determined with quantum Rice Ramsperger Kassel (RRK) analysis for k(E) and master equation analysis for fall-off. We find that reactions of mercury with a small fraction of the reactor surface or initiation by low concentrations of halogen atoms is needed to explain the experimental conversion of Hg to HgX2 in the gas phase. The models do not replicate data from experiments that do not explicitly provide an atom source. The Hg insertion reaction into X2 (Hg + X2 → HgX2) that has been reported is further studied, and we find agreement with studies that report high barriers. The high barriers prevent this insertion path from explaining the experimental data on HgX2 formation and Hg conversion under atmospheric conditions. Mechanism studies with low initial concentrations of halogen radicals show significant conversion of Hg under the experimental conditions.

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Detection of mercury in air in the presence of chlorine and water vapor

Cited by 33 publications

References 0 publications

Effects of relative humidity and CO(g) on the O3-initiated oxidation reaction of Hg0(g): kinetic & product studies

Effects of relative humidity and CO(g) on the O3-initiated oxidation reaction of Hg0(g): kinetic & product studies

A review of uncertainties in atmospheric modeling of mercury chemistry I. Uncertainties in existing kinetic parameters – Fundamental limitations and the importance of heterogeneous chemistry

Mercury Oxidation via Chlorine, Bromine, and Iodine under Atmospheric Conditions: Thermochemistry and Kinetics

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