Implementation of the DOAS Method for Measuring Concentrations of Chlorine and Bromine Oxide Molecules in the Atmosphere in the UV Region of the Spectrum

Abstract. Record breaking loss of ozone (O3) in the Arctic stratosphere has been reported in winter–spring 2010/2011. We examine in detail the composition and transformations occurring in the Arctic polar vortex using total column and vertical profile data products for O3, bromine oxide (BrO), nitrogen dioxide (NO2), chlorine dioxide (OClO), and polar stratospheric clouds (PSC) retrieved from measurements made by SCIAMACHY (Scanning Imaging Absorption SpectroMeter for Atmospheric CHartography) on-board Envisat (Environmental Satellite), as well as total column ozone amount, retrieved from the measurements of GOME-2 (Global Ozone Monitoring Experiment) on MetOp-A (Meteorological Experimental Satellite). Similarly we use the retrieved data from DOAS (Differential Optical Absorption Spectroscopy) measurements made in Ny-Ålesund (78.55° N, 11.55° E). A chemical transport model (CTM) has been used to relate and compare Arctic winter–spring conditions in 2011 with those in the previous year. In late winter–spring 2010/2011 the chemical ozone loss in the polar vortex derived from SCIAMACHY observations confirms findings reported elsewhere. More than 70% of O3 was depleted by halogen catalytic cycles between the 425 and 525 K isentropic surfaces, i.e. in the altitude range ~16–20 km. In contrast, during the same period in the previous winter 2009/2010, a typical warm Arctic winter, only slightly more than 20% depletion occurred below 20 km, while 40% of O3 was removed above the 575 K isentrope (~23 km). This loss above 575 K is explained by the catalytic destruction by NOx descending from the mesosphere. In both Arctic winters 2009/2010 and 2010/2011, calculated O3 losses from the CTM are in good agreement to our observations and other model studies. The mid-winter 2011 conditions, prior to the catalytic cycles being fully effective, are also investigated. Surprisingly, a significant loss of O3 around 60%, previously not discussed in detail, is observed in mid-January 2011 below 500 K (~19 km) and sustained for approximately 1 week. The low O3 region had an exceptionally large spatial extent. The situation was caused by two independently evolving tropopause elevations over the Asian continent. Induced adiabatic cooling of the stratosphere favoured the formation of PSC, increased the amount of active chlorine for a short time, and potentially contributed to higher polar ozone loss later in spring.

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Spectroscopic Measurement of Bromine Oxide, Ozone, and Nitrous Acid in Alert

The Tropospheric Chemistry of Ozone in the Polar Regions ◽

10.1007/978-3-642-78211-4_13 ◽

1993 ◽

pp. 189-203 ◽

Cited By ~ 3

Author(s):

M. Hausmann ◽

T. Rudolf ◽

U. Platt

Keyword(s):

Nitrous Acid ◽

Spectroscopic Measurement ◽

Bromine Oxide

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Kinetic studies of oxy-halogen radical systems

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1968.0048 ◽

1968 ◽

Vol 303 (1473) ◽

pp. 207-231 ◽

Cited By ~ 60

Keyword(s):

Thermal Decomposition ◽

Chlorine Dioxide ◽

Peroxy Radical ◽

Kinetic Studies ◽

Bromine Oxide ◽

Chlorine Oxide ◽

Direct Reactions ◽

Rapid Reaction ◽

Atomic Chlorine ◽

Halogen Radical

Chlorine oxide radicals, ClO( 2 II , v " = 0) were obtained as a product of (a) the rapid reaction of Cl with chlorine dioxide at 300°K, Cl + OClO → ClO + ClO, (1) (b) the initiated thermal decomposition of OClO above 320°K, (c) the rapid reaction of Cl with ozone at 300°K, Cl + O 3 → ClO + O 2 . Bromine oxide radicals, BrO ( 2 II , v " = 0), have also been detected in the reaction of bromine atoms with ozone. The decay reaction of ClO radicals was second order in [ClO] at all temperatures studied (294 to 495°K). The decay of [ClO] in the presence of chlorine atom scavengers (H 2 , Br 2 , OClO) has also been studied. The direct reactions of ClO with H 2 (7), and with O 3 (9), were undetectably slow, with k 7 < 10 8.5 and k 9 < 10 9.5 cm 3 mole -1 s -1 at 294°K. The recombination of two ClO radicals probably takes place through a mechanism involving small concentrations of atomic chlorine and the short-lived, ClOO peroxy radical, ClO + ClO → k 2 C1 + ClOO, (2) ClOO + Cl → Cl 2 ( 1 ∑ + g , 3 II Ou+ + O 2 , (3) ClOO + M → Cl + O 2 + M . (4) Rate measurements gave k 2 = (7 ± 2) x 10 11 exp [(— 2500 ± 300)/ RT ] cm 3 mole -1 s -1 from 294 to 495°K. The present values for k 2 are compared with those found previously.

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Precipitation of salts in freezing seawater and ozone depletion events: a status report

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-7317-2008 ◽

2008 ◽

Vol 8 (23) ◽

pp. 7317-7324 ◽

Cited By ~ 32

Author(s):

S. Morin ◽

G. M. Marion ◽

R. von Glasow ◽

D. Voisin ◽

J. Bouchez ◽

...

Keyword(s):

Ozone Depletion ◽

Marine Boundary Layer ◽

State Of The Art ◽

Electrolyte Solutions ◽

Subzero Temperature ◽

Status Report ◽

Bromine Oxide ◽

Mixing Ratios ◽

Laboratory Investigations ◽

Freezing Seawater

Abstract. In springtime, the polar marine boundary layer exhibits drastic ozone depletion events (ODEs), associated with elevated bromine oxide (BrO) mixing ratios. The current interpretation of this peculiar chemistry requires the existence of acid and bromide-enriched surfaces to heterogeneously promote and sustain ODEs. Sander et al. (2006) have proposed that calcium carbonate (CaCO3) precipitation in any seawater-derived medium could potentially decrease its alkalinity, making it easier for atmospheric acids such as HNO3 and H2SO4 to acidify it. We performed simulations using the state-of-the-art FREZCHEM model, capable of handling the thermodynamics of concentrated electrolyte solutions, to try to reproduce their results, and found that when ikaite (CaCO3·6H2O) rather than calcite (CaCO3) precipitates, there is no such effect on alkalinity. Given that ikaite has recently been identified in Antarctic brines (Dieckmann et al., 2008), our results show that great caution should be exercised when using the results of Sander et al. (2006), and reveal the urgent need of laboratory investigations on the actual link(s) between bromine activation and the pH of the surfaces on which it is supposed to take place at subzero temperature. In addition, the evolution of the Cl/Br ratio in the brine during freezing was computed using FREZCHEM, taking into account Br substitutions in Cl–containing salts.

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Major influence of BrO on the NOx and nitrate budgets in the Arctic spring, inferred from Δ17O(NO3 - ) measurements during ozone depletion events

Environmental Chemistry ◽

10.1071/en07003 ◽

2007 ◽

Vol 4 (4) ◽

pp. 238 ◽

Cited By ~ 9

Author(s):

S. Morin ◽

J. Savarino ◽

S. Bekki ◽

A. Cavender ◽

P. B. Shepson ◽

...

Keyword(s):

Nitrogen Oxides ◽

Isotopic Composition ◽

Atmospheric Chemistry ◽

Ozone Depletion ◽

Lower Atmosphere ◽

The Arctic ◽

Major Influence ◽

Peroxy Radicals ◽

Bromine Oxide ◽

Atmospheric Nitrate

Environmental context. Ozone depletion events (ODEs) in the Arctic lower atmosphere drive profound changes in the chemistry of nitrogen oxides (NOx) because of the presence of bromine oxide (BrO). These are investigated using the isotopic composition of atmospheric nitrate (NO3–), which is a ubiquitous species formed through the oxidation of nitrogen oxides. Since BrO is speculated to play a key role in the atmospheric chemistry of marine regions and in the free troposphere, our studies contribute to the improvement of the scientific knowledge on this new topic in atmospheric chemistry. Abstract. The triple oxygen isotopic composition of atmospheric inorganic nitrate was measured in samples collected in the Arctic in springtime at Alert, Nunavut and Barrow, Alaska. The isotope anomaly of nitrate (Δ17O = δ17O–0.52δ18O) was used to probe the influence of ozone (O3), bromine oxide (BrO), and peroxy radicals (RO2) in the oxidation of NO to NO2, and to identify the dominant pathway that leads to the production of atmospheric nitrate. Isotopic measurements confirm that the hydrolysis of bromine nitrate (BrONO2) is a major source of nitrate in the context of ozone depletion events (ODEs), when brominated compounds primarily originating from sea salt catalytically destroy boundary layer ozone. They also show a case when BrO is the main oxidant of NO into NO2.

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Constraining the concentration of the hydroxyl radical in a stratocumulus-topped marine boundary layer from sea-to-air eddy covariance flux measurements of dimethylsulfide

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-9225-2009 ◽

2009 ◽

Vol 9 (23) ◽

pp. 9225-9236 ◽

Cited By ~ 33

Author(s):

M. Yang ◽

B. W. Blomquist ◽

B. J. Huebert

Keyword(s):

Boundary Layer ◽

Hydroxyl Radical ◽

Eddy Covariance ◽

Diurnal Cycle ◽

Marine Boundary Layer ◽

High Reactivity ◽

Simple Method ◽

Bromine Oxide ◽

Dms Oxidation ◽

Strong Inversion

Abstract. The hydroxyl radical (OH) is an important oxidant in the troposphere due to its high reactivity and relative abundance. Measuring the concentration of OH in situ, however, is technically challenging. Here we present a simple method of estimating an OH-equivalent oxidant concentration ("effective OH") in the marine boundary layer (MBL) from the mass balance of dimethylsulfide (DMS). We use shipboard eddy covariance measurements of the sea-to-air DMS flux from the Vamos Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in October and November of 2008. The persistent stratocumulus cloud-cover off the west coast of South America and the associated strong inversion between MBL and the free troposphere (FT) greatly simplify the dynamics in this region and make our budget estimate possible. From the observed diurnal cycle in DMS concentration, the nighttime entrainment velocity at the inversion is estimated to be 4 mm s−1. We calculate 1.4(±0.2)×106 OH molecules cm−3 from the DMS budget, which represents a monthly effective concentration and is well within the range of previous estimates. Furthermore, when linearly proportioned according to the intensity of solar flux, the resultant diel OH profile, together with DMS surface and entrainment fluxes, enables us to accurately replicate the observed diurnal cycle in DMS (correlation coefficient over 0.9). The nitrate radical (NO3) is found to have little contribution to DMS oxidation during VOCALS-REx. An upper limit estimate of 1 pptv of bromine oxide radical (BrO) would account for 30% of DMS oxidation and lower the OH concentration to 1.0)×106 OH molecules cm−3. Our effective OH estimate includes the oxidation of DMS by such radicals.

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Active and widespread halogen chemistry in the tropical and subtropical free troposphere

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1505142112 ◽

2015 ◽

Vol 112 (30) ◽

pp. 9281-9286 ◽

Cited By ~ 63

Author(s):

Siyuan Wang ◽

Johan A. Schmidt ◽

Sunil Baidar ◽

Sean Coburn ◽

Barbara Dix ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Oxidative Capacity ◽

Free Troposphere ◽

Mercury Deposition ◽

Tropical Eastern Pacific ◽

Ice Clouds ◽

Bromine Oxide ◽

Halogen Chemistry ◽

Model Predictions ◽

Wet Scavenging

Halogens in the troposphere are increasingly recognized as playing an important role for atmospheric chemistry, and possibly climate. Bromine and iodine react catalytically to destroy ozone (O3), oxidize mercury, and modify oxidative capacity that is relevant for the lifetime of greenhouse gases. Most of the tropospheric O3 and methane (CH4) loss occurs at tropical latitudes. Here we report simultaneous measurements of vertical profiles of bromine oxide (BrO) and iodine oxide (IO) in the tropical and subtropical free troposphere (10°N to 40°S), and show that these halogens are responsible for 34% of the column-integrated loss of tropospheric O3. The observed BrO concentrations increase strongly with altitude (∼3.4 pptv at 13.5 km), and are 2–4 times higher than predicted in the tropical free troposphere. BrO resembles model predictions more closely in stratospheric air. The largest model low bias is observed in the lower tropical transition layer (TTL) over the tropical eastern Pacific Ocean, and may reflect a missing inorganic bromine source supplying an additional 2.5–6.4 pptv total inorganic bromine (Bry), or model overestimated Bry wet scavenging. Our results highlight the importance of heterogeneous chemistry on ice clouds, and imply an additional Bry source from the debromination of sea salt residue in the lower TTL. The observed levels of bromine oxidize mercury up to 3.5 times faster than models predict, possibly increasing mercury deposition to the ocean. The halogen-catalyzed loss of tropospheric O3 needs to be considered when estimating past and future ozone radiative effects.

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Atmospheric nitrogen oxides (NO and NO<sub>2</sub>) at Dome C, East Antarctica, during the OPALE campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-7859-2015 ◽

2015 ◽

Vol 15 (14) ◽

pp. 7859-7875 ◽

Cited By ~ 28

Author(s):

M. M. Frey ◽

H. K. Roscoe ◽

A. Kukui ◽

J. Savarino ◽

J. L. France ◽

...

Keyword(s):

Nitrogen Oxides ◽

Atmospheric Chemistry ◽

Ambient Air ◽

Skin Layer ◽

East Antarctica ◽

Atmospheric Nitrogen ◽

Bromine Oxide ◽

Diurnal Cycles ◽

Mixing Ratios ◽

Air Chemistry

Abstract. Mixing ratios of the atmospheric nitrogen oxides NO and NO2 were measured as part of the OPALE (Oxidant Production in Antarctic Lands & Export) campaign at Dome C, East Antarctica (75.1° S, 123.3° E, 3233 m), during December 2011 to January 2012. Profiles of NOx mixing ratios of the lower 100 m of the atmosphere confirm that, in contrast to the South Pole, air chemistry at Dome C is strongly influenced by large diurnal cycles in solar irradiance and a sudden collapse of the atmospheric boundary layer in the early evening. Depth profiles of mixing ratios in firn air suggest that the upper snowpack at Dome C holds a significant reservoir of photolytically produced NO2 and is a sink of gas-phase ozone (O3). First-time observations of bromine oxide (BrO) at Dome C show that mixing ratios of BrO near the ground are low, certainly less than 5 pptv, with higher levels in the free troposphere. Assuming steady state, observed mixing ratios of BrO and RO2 radicals are too low to explain the large NO2 : NO ratios found in ambient air, possibly indicating the existence of an unknown process contributing to the atmospheric chemistry of reactive nitrogen above the Antarctic Plateau. During 2011–2012, NOx mixing ratios and flux were larger than in 2009–2010, consistent with also larger surface O3 mixing ratios resulting from increased net O3 production. Large NOx mixing ratios at Dome C arise from a combination of continuous sunlight, shallow mixing height and significant NOx emissions by surface snow (FNOx). During 23 December 2011–12 January 2012, median FNOx was twice that during the same period in 2009–2010 due to significantly larger atmospheric turbulence and a slightly stronger snowpack source. A tripling of FNOx in December 2011 was largely due to changes in snowpack source strength caused primarily by changes in NO3− concentrations in the snow skin layer, and only to a secondary order by decrease of total column O3 and associated increase in NO3− photolysis rates. A source of uncertainty in model estimates of FNOx is the quantum yield of NO3− photolysis in natural snow, which may change over time as the snow ages.

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