Observations of inorganic bromine (HOBr, BrO, and Br2) speciation at Barrow, Alaska, in spring 2009
TL;DR: The first direct measurements of hypobromous acid (HOBr) as well as observations of BrO and molecular bromine (Br2) by chemical ionization mass spectrometry at Barrow, Alaska in spring 2009 during the Ocean-Atmospheric-Sea Ice-Snowpack (OASIS) campaign were reported as discussed by the authors.
Abstract: [1] Inorganic bromine plays a critical role in ozone and mercury depletions events (ODEs and MDEs) in the Arctic marine boundary layer. Direct observations of bromine species other than bromine oxide (BrO) during ODEs are very limited. Here we report the first direct measurements of hypobromous acid (HOBr) as well as observations of BrO and molecular bromine (Br2) by chemical ionization mass spectrometry at Barrow, Alaska in spring 2009 during the Ocean-Atmospheric-Sea Ice-Snowpack (OASIS) campaign. Diurnal profiles of HOBr with maximum concentrations near local noon and no significant concentrations at night were observed. The measured average daytime HOBr mixing ratio was 10 pptv with a maximum value of 26 pptv. The observed HOBr was reasonably well correlated (R2 = 0.57) with predictions from a simple steady state photochemical model constrained to observed BrO and HO2 at wind speeds <6 m s−1. However, predicted HOBr levels were considerably higher than observations at higher wind speeds. This may be due to enhanced heterogeneous loss of HOBr on blowing snow coincident with higher wind speeds. BrO levels were also found to be higher at elevated wind speeds. Br2 was observed in significant mixing ratios (maximum = 46 pptv; average = 13 pptv) at night and was strongly anti-correlated with ozone. The diurnal speciation of observed gas phase inorganic bromine species can be predicted by a time-dependent box model that includes efficient heterogeneous recycling of HOBr, hydrogen bromide (HBr), and bromine nitrate (BrONO2) back to more reactive forms of bromine.
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TL;DR: This critical review summarises the current understanding and uncertainties of the main halogen photochemistry processes, including the current knowledge of the atmospheric impact of halogen chemistry as well as open questions and future research needs.
Abstract: Halogen chemistry is well known for ozone destruction in the stratosphere, however reactive halogens also play an important role in the chemistry of the troposphere. In the last two decades, an increasing number of reactive halogen species have been detected in a wide range of environmental conditions from the polar to the tropical troposphere. Growing observational evidence suggests a regional to global relevance of reactive halogens for the oxidising capacity of the troposphere. This critical review summarises our current understanding and uncertainties of the main halogen photochemistry processes, including the current knowledge of the atmospheric impact of halogen chemistry as well as open questions and future research needs.
290 citations
University of Toronto1, Centre national de la recherche scientifique2, University of California, Los Angeles3, University of Gothenburg4, City University of New York5, Natural Environment Research Council6, Royal Holloway, University of London7, Spanish National Research Council8, Purdue University9, University College Cork10, University of Colorado Boulder11, University of East Anglia12, University of Cambridge13
TL;DR: The role of ice in the formation of chemically active halogens in the environment requires a full understanding because of its role in atmospheric chemistry, including controlling the regional atmospheric oxidizing capacity in specific situations as mentioned in this paper.
Abstract: The role of ice in the formation of chemically active halogens in the environment requires a full understanding because of its role in atmospheric chemistry, including controlling the regional atmospheric oxidizing capacity in specific situations. In particular, ice and snow are important for facilitating multiphase oxidative chemistry and as media upon which marine algae live. This paper reviews the nature of environmental ice substrates that participate in halogen chemistry, describes the reactions that occur on such substrates, presents the field evidence for ice-mediated halogen activation, summarizes our best understanding of ice-halogen activation mechanisms, and describes the current state of modeling these processes at different scales. Given the rapid pace of developments in the field, this paper largely addresses advances made in the past five years, with emphasis given to the polar boundary layer. The integrative nature of this field is highlighted in the presentation of work from the molecular to the regional scale, with a focus on understanding fundamental processes. This is essential for developing realistic parameterizations and descriptions of these processes for inclusion in larger scale models that are used to determine their regional and global impacts.
200 citations
TL;DR: In this paper, measurements on Alaskan snow and sea ice suggest that photochemical reactions in surface snow serve as a major source of reactive bromine to the overlying atmosphere, contributing to episodic ozone depletion.
Abstract: Following the spring-time polar sunrise, ozone concentrations in the lower troposphere episodically decline to near-zero levels. Measurements on Alaskan snow and sea ice suggest that photochemical reactions in surface snow serve as a major source of reactive bromine to the overlying atmosphere, contributing to episodic ozone depletion.
172 citations
Georgia Institute of Technology1, Earth System Research Laboratory2, Cooperative Institute for Research in Environmental Sciences3, Sandia National Laboratories4, University of Colorado Boulder5, National Center for Atmospheric Research6, Purdue University7, University of California, Davis8, University of Helsinki9, Environment Canada10
TL;DR: In this paper, the authors show that chlorine radicals function as a strong atmospheric oxidant, particularly in polar regions, where levels of hydroxyl radicals are low, and they find high levels of molecular chlorine during the day consistent with a photochemical source.
Abstract: Chlorine radicals function as a strong atmospheric oxidant, particularly in polar regions, where levels of hydroxyl radicals are low. Measurements in the Arctic reveal high levels of molecular chlorine during the day, consistent with a photochemical source.
100 citations
TL;DR: This study provides a breakthrough in quantitatively constraining bromine chemistry in the polar atmosphere, where this chemistry connects the rapidly changing surface to pollutant fate.
Abstract: Bromine atoms play a central role in atmospheric reactive halogen chemistry, depleting ozone and elemental mercury, thereby enhancing deposition of toxic mercury, particularly in the Arctic near-surface troposphere. However, direct bromine atom measurements have been missing to date, due to the lack of analytical capability with sufficient sensitivity for ambient measurements. Here we present direct atmospheric bromine atom measurements, conducted in the springtime Arctic. Measured bromine atom levels reached 14 parts per trillion (ppt, pmol mol−1; 4.2 × 108 atoms per cm−3) and were up to 3–10 times higher than estimates using previous indirect measurements not considering the critical role of molecular bromine. Observed ozone and elemental mercury depletion rates are quantitatively explained by the measured bromine atoms, providing field validation of highly uncertain mercury chemistry. Following complete ozone depletion, elevated bromine concentrations are sustained by photochemical snowpack emissions of molecular bromine and nitrogen oxides, resulting in continued atmospheric mercury depletion. This study provides a breakthrough in quantitatively constraining bromine chemistry in the polar atmosphere, where this chemistry connects the rapidly changing surface to pollutant fate.
61 citations
Cites methods from "Observations of inorganic bromine (..."
...This inlet design has been used to measure surface-active gases including HNO3 (52), NH3 (53), BrO (27, 49), HOBr (26, 48), and ClO (24)....
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...Hydrated I clusters [I·(H2O)n ] were used as the reagent ion to measure Br [m/z 206 (I(79)Br) and 208 (I(81)Br)], Br2 [m/z 287 (I(79)Br(81)Br) and 289 (I(81)Br(81)Br)], BrO [m/z 222 (I(79)BrO) and 224 (I(81)BrO)], HOBr [m/z 223 (IHO(79)Br) and 225 (IHO(81)Br)], Cl2 [m/z 197 (I(35)Cl(35)Cl) and 199 (I(35)Cl(37)Cl)], and ClO [m/z 178 (I(35)ClO) and 180 (I(37)ClO)], with isotope ratios used for verification of ion identities (24, 48, 50)....
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...1) (48) are described in previous studies....
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References
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01 Oct 2015
TL;DR: This is the eighteenth in a series of evaluated sets of rate constants, photochemical cross sections, heterogeneous parameters, and thermochemical parameters compiled by the NASA Panel for Data Evaluation as mentioned in this paper.
Abstract: This is the eighteenth in a series of evaluated sets of rate constants, photochemical cross sections, heterogeneous parameters, and thermochemical parameters compiled by the NASA Panel for Data Evaluation. The data are used primarily to model stratospheric and upper tropospheric processes, with particular emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena. The evaluation is available in electronic form from the following Internet URL: http://jpldataeval.jpl.nasa.gov/
1,830 citations
TL;DR: In this paper, the authors focus on recent ground-level observations from the Canadian baseline station at Alert (82.5° N, 62.3° W) and from aircraft that show that ozone destruction is occurring under the Arctic surface radiation inversion during March and April as the Sun rises.
Abstract: There is increasing evidence that at polar sunrise sunlight-induced changes in the composition of the lower Arctic atmosphere (0–2 km) are taking place that are important regarding the tropospheric cycles of ozone, bromine, sulphur oxides1, nitrogen oxides2 and possibly iodine3. Here we focus on recent ground-level observations from the Canadian baseline station at Alert (82.5° N, 62.3° W) and from aircraft that show that ozone destruction is occurring under the Arctic surface radiation inversion during March and April as the Sun rises. The destruction might be linked to catalytic reactions of BrOx radicals and the photochemistry of bromoform, which appears to have a biological origin in the Arctic Ocean. This may clarify previously unexplained regular springtime occurrences of ozone depletion at ground level in a 10-year data record at Barrow, Alaska4, as well as peaks in aerosol bromine observed throughout the Arctic in March and April3. Current information does not allow us to offer more than a speculative explanation for the chemical mechanisms leading to these phenomena.
939 citations
Book•
01 Jan 1970
TL;DR: In this article, the processes leading to the formation of high-dispersed aerosols with particle size below 0.1 μ and the methods of generation and investigation of these aerosols are treated as well as their physical properties differing fundamentally from those of coarse aerosols.
Abstract: The processes leading to the formation of high-dispersed aerosols with particle size below 0.1 μ and the methods of generation and investigation of these aerosols are treated as well as their physical properties differing fundamentally from those of coarse aerosols. In spite of the great role played by high-dispersed aerosols in the important process of vapor condensation in space and their significance for many industries and meteorology, there are no monographs or reviews on this subject available in the literature, and the aim of the present work is to fill this gap.
802 citations
University of Alaska Fairbanks1, University of East Anglia2, National Institute of Water and Atmospheric Research3, British Antarctic Survey4, McGill University5, Environment Canada6, University of Bremen7, University of York8, Heidelberg University9, University of Southern Denmark10, University of Leeds11, University of Hamburg12, Earth System Research Laboratory13, Max Planck Society14, Purdue University15, University College Cork16
TL;DR: In the polar regions, unique photochemistry converts inert halide salt ions (e.g. Br−) into reactive halogen species that deplete ozone in the boundary layer to near zero levels as discussed by the authors.
Abstract: . During springtime in the polar regions, unique photochemistry converts inert halide salt ions (e.g. Br−) into reactive halogen species (e.g. Br atoms and BrO) that deplete ozone in the boundary layer to near zero levels. Since their discovery in the late 1980s, research on ozone depletion events (ODEs) has made great advances; however many key processes remain poorly understood. In this article we review the history, chemistry, dependence on environmental conditions, and impacts of ODEs. This research has shown the central role of bromine photochemistry, but how salts are transported from the ocean and are oxidized to become reactive halogen species in the air is still not fully understood. Halogens other than bromine (chlorine and iodine) are also activated through incompletely understood mechanisms that are probably coupled to bromine chemistry. The main consequence of halogen activation is chemical destruction of ozone, which removes the primary precursor of atmospheric oxidation, and generation of reactive halogen atoms/oxides that become the primary oxidizing species. The different reactivity of halogens as compared to OH and ozone has broad impacts on atmospheric chemistry, including near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere. Recent changes in the climate of the Arctic and state of the Arctic sea ice cover are likely to have strong effects on halogen activation and ODEs; however, more research is needed to make meaningful predictions of these changes.
581 citations
TL;DR: In this paper, the authors proposed a mechanism based on known aqueous phase chemistry, which rapidly converts HBr, HOBr and BrNO3 back to Br and BrO radicals.
Abstract: NEAR-TOTAL depletion of the ozone in surface air is often observed in the Arctic spring, coincident with high atmospheric concentrations of inorganic bromine1–5. Barrie et al.1 suggested that the ozone depletion was due to a catalytic cycle involving the radicals Br and BrO (ref. 6); however, these species are rapidly converted to the nonradical species HBr, HOBr and BrNO3, quenching ozone loss. McConnell et al.7 proposed that cycling of inorganic bromine between aerosols and the gas phase could maintain sufficiently high levels of Br and BrO to destroy ozone, but they did not specify a mechanism for aerosol-phase production of active bromine species. Here we propose such a mechanism, based on known aqueous-phase chemistry, which rapidly converts HBr, HOBr and BrNO3 back to Br and BrO radicals. This mechanism should be particularly efficient in the presence of the high concentrations of sulphuric acid aerosols observed during ozone depletion events3.
444 citations
"Observations of inorganic bromine (..." refers background in this paper
...bromine ((R10) and (R7)) [Fan and Jacob, 1992]....
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..., 2011a], which confirmed that BrO is a photochemically generated species with a short lifetime [e.g., Evans et al., 2003; Fan and Jacob, 1992]....
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..., Br2) (R7) [Fan and Jacob, 1992]....
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