scholarly journals Consumption of reactive halogen species from sea-salt aerosol by secondary organic aerosol: slowing down the bromine explosion

2015 ◽  
Vol 12 (4) ◽  
pp. 476 ◽  
Author(s):  
Joelle Buxmann ◽  
Sergej Bleicher ◽  
Ulrich Platt ◽  
Roland von Glasow ◽  
Roberto Sommariva ◽  
...  
Keyword(s):  
Loss Rate ◽  
Secondary Organic Aerosols ◽  
Current Knowledge ◽  
Organic Aerosols ◽  
Absorption Spectrometry ◽  
Sea Salt ◽  
Box Models ◽  
Reactive Halogen Species ◽  
Blank Experiment ◽  
Halogen Species

Environmental context Secondary organic aerosols together with sea-salt aerosols are a major contribution to global aerosols and influence the release of reactive halogens, which affect air quality and human health. In this study, the loss of reactive halogen species from simulated salt aerosols due to three different types of secondary organic aerosols was quantified in chamber experiments and investigated with the help of a numerical model. The loss rate can be included into chemistry models of the atmosphere and help to quantify the halogen budget in nature. Abstract The interaction between secondary organic aerosols (SOAs) and reactive bromine species (e.g. BrO, Br2, HOBr) coexisting in the environment is not well understood and not included in current chemistry models. The present study quantifies the quenching of bromine release from an artificial salt aerosol caused by SOAs from ozonolysis of three precursors (α-pinene, catechol or guaiacol) in a Teflon smog chamber and incorporates it into a chemical box model. The model simulations perform very well for a blank experiment without SOA precursor, capturing BrO formation, as detected by differential optical absorption spectrometry. A first-order BrO loss rate of 0.001s–1 on the surface of SOA represents the overall effective Brx (total inorganic bromine) loss included in the model. Generally, the model agrees with the maximum BrO mixing ratio in time and magnitude, with some disagreements in the exact shape. Formation of reactive OClO was observed in the presence of organics but could not be reproduced by the model. According to current knowledge, most inorganic chlorine would be in the form of HCl in the presence of organics, as predicted by the model. In order to reproduce the net effects of the presence of SOA, the effective uptake coefficients of reactive bromine on the SOA surface are estimated to be 0.01, 0.01 and 0.004 for α-pinene, catechol and guaiacol respectively. The uptake coefficient can now be incorporated into box models and even global models, where sinks for bromine species are thought to be inadequately represented.

scholarly journals Importance of reactive halogens in the tropical marine atmosphere: a regional modelling study using WRF-Chem

2019 ◽  
Vol 19 (5) ◽  
pp. 3161-3189 ◽  
Author(s):  
Alba Badia ◽  
Claire E. Reeves ◽  
Alex R. Baker ◽  
Alfonso Saiz-Lopez ◽  
Rainer Volkamer ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Sea Salt ◽  
Heterogeneous Chemistry ◽  
Marine Atmosphere ◽  
Tropical Ocean ◽  
Mixing Ratios ◽  
Reactive Halogen Species ◽  
Inorganic Iodine ◽  
The Impact ◽  
Halogen Species

Abstract. This study investigates the impact of reactive halogen species (RHS, containing chlorine (Cl), bromine (Br) or iodine (I)) on atmospheric chemistry in the tropical troposphere and explores the sensitivity to uncertainties in the fluxes of RHS to the atmosphere and their chemical processing. To do this, the regional chemistry transport model WRF-Chem has been extended to include Br and I, as well as Cl chemistry for the first time, including heterogeneous recycling reactions involving sea-salt aerosol and other particles, reactions of Br and Cl with volatile organic compounds (VOCs), along with oceanic emissions of halocarbons, VOCs and inorganic iodine. The study focuses on the tropical east Pacific using field observations from the Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC (TORERO) campaign (January–February 2012) to evaluate the model performance. Including all the new processes, the model does a reasonable job reproducing the observed mixing ratios of bromine oxide (BrO) and iodine oxide (IO), albeit with some discrepancies, some of which can be attributed to difficulties in the model's ability to reproduce the observed halocarbons. This is somewhat expected given the large uncertainties in the air–sea fluxes of the halocarbons in a region where there are few observations of their seawater concentrations. We see a considerable impact on the inorganic bromine (Bry) partitioning when heterogeneous chemistry is included, with a greater proportion of the Bry in active forms such as BrO, HOBr and dihalogens. Including debromination of sea salt increases BrO slightly throughout the free troposphere, but in the tropical marine boundary layer, where the sea-salt particles are plentiful and relatively acidic, debromination leads to overestimation of the observed BrO. However, it should be noted that the modelled BrO was extremely sensitive to the inclusion of reactions between Br and the oxygenated VOCs (OVOCs), which convert Br to HBr, a far less reactive form of Bry. Excluding these reactions leads to modelled BrO mixing ratios greater than observed. The reactions between Br and aldehydes were found to be particularly important, despite the model underestimating the amount of aldehydes observed in the atmosphere. There are only small changes to the inorganic iodine (Iy) partitioning and IO when the heterogeneous reactions, primarily on sea salt, are included. Our model results show that tropospheric Ox loss due to halogens ranges between 25 % and 60 %. Uncertainties in the heterogeneous chemistry accounted for a small proportion of this range (25 % to 31 %). This range is in good agreement with other estimates from state-of-the-art atmospheric chemistry models. The upper bound is found when reactions between Br and Cl with VOCs are not included and, consequently, Ox loss by BrOx, ClOx and IOx cycles is high (60 %). With the inclusion of halogens in the troposphere, O3 is reduced by 7 ppbv on average. However, when reactions between Br and Cl with VOCs are not included, O3 is much lower than observed. Therefore, the tropospheric Ox budget is highly sensitive to the inclusion of halogen reactions with VOCs and to the uncertainties in current understanding of these reactions and the abundance of VOCs in the remote marine atmosphere.

scholarly journals The influence of nitrogen oxides on the activation of bromide and chloride in salt aerosol

2014 ◽  
Vol 14 (7) ◽  
pp. 10135-10166 ◽  
Author(s):  
S. Bleicher ◽  
J. C. Buxmann ◽  
R. Sander ◽  
T. P. Riedel ◽  
J. A. Thornton ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Absorption Spectrometry ◽  
Liquid Water Content ◽  
Ionization Mass ◽  
Mixing Ratios ◽  
Time Profiles ◽  
Flame Ionization ◽  
Reactive Halogen Species ◽  
Halogen Species ◽  
Cl Atoms

Abstract. Experiments on salt aerosol with different salt contents were performed in a Teflon chamber under tropospheric light conditions with various initial contents of nitrogen oxides (NOx = NO + NO2). A strong activation of halogens was found at high NOx mixing ratios, even in samples with lower bromide contents such as road salts. The ozone depletion by reactive halogen species released from the aerosol, was found to be a function of the initial NOx mixing ratio. Besides bromine, large amounts of chlorine have been released in our smog chamber. Time profiles of the halogen species Cl2, Br2, ClNO2, BrNO2 and BrO, ClO, OClO and Cl atoms were simultaneously measured by various techniques (chemical ionization mass spectrometry, differential optical absorption spectrometry coupled with a multi-reflection cell and gas chromatography of hydrocarbon tracers for Cl and OH, employing cryogenic preconcentration and flame ionization detection). Measurements are compared to calculations by the CAABA/MECCA 0-D box model, which was adapted to the chamber conditions and took the aerosol liquid water content and composition into account. The model results agree reasonably with the observations and provide important information about the prerequisites for halogen release, such as the time profiles of the aerosol bromide and chloride contents as well as the aerosol pH.

scholarly journals Reactive bromine in the low troposphere of Antarctica. Estimations at two research sites

2018 ◽  
Author(s):  
Cristina Prados-Roman ◽  
Laura Gómez-Martín ◽  
Olga Puentedura ◽  
Mónica Navarro-Comas ◽  
Javier Iglesias ◽  
...  
Keyword(s):  
Loss Rate ◽  
Arctic Region ◽  
The Arctic ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Ancillary Data ◽  
Reactive Halogen Species ◽  
The Antarctic ◽  
Halogen Species ◽  
The Arctic Region

Abstract. For decades, reactive halogen species (RHS) have been subject of detailed scientific research due to their influence on the oxidizing capacity of the atmosphere and on the climate. From the RHS, those containing bromine are of particular interest in the polar troposphere as a result of their link to ozone depletion events (ODEs) and to the perturbation of the cycle of e.g. the toxic mercury. Given its remoteness and related limited accessibility compared to the Arctic region, the RHS in the Antarctic troposphere are still poorly characterized. This work presents ground-based observations of tropospheric BrO from two different Antarctic locations: Marambio (64º13′ S, 56º37′ W) and Belgrano II (77º52′ S, 34º37′ W) during the sunlit period of 2015. By means of MAX-DOAS (Multi-axis Differential Optical Absorption Spectroscopy) measurements of BrO performed from the two research sites, the seasonal variation of this reactive trace gas is described along with its vertical and geographical distribution in the Antarctic environment. Results show an overall vertical profile of BrO mixing ratio decreasing with altitude, with a median value of 1.6 pmol mol−1 in the lowest layers of the troposphere and undetectable values above 2 km at both sites. Additionally, observations show that the polar sunrise triggers a heterogeneous increase of bromine content in the Antarctic troposphere yielding a maximum BrO at Marambio (26 pmol mol−1), amounting threefold the values observed at Belgrano at dawn. Data presented herein are combined with previous studies and ancillary data to update and expand our knowledge of the geographical and vertical distribution of BrO in the Antarctic troposphere, revealing Marambio as one of the locations with highest BrO reported so far in Antarctica. Furthermore, the observations gathered during 2015 serve as a proxy to investigate the budget of reactive bromine (BrOx = Br + BrO) and the bromine-mediated ozone loss rate in the Antarctic troposphere.

scholarly journals Large Discrepancy in the Formation of Secondary Organic Aerosols from Structurally Similar Monoterpenes

2021 ◽  
Vol 5 (3) ◽  
pp. 632-644
Author(s):  
Ditte Thomsen ◽  
Jonas Elm ◽  
Bernadette Rosati ◽  
Jane Tygesen Skønager ◽  
Merete Bilde ◽  
...  
Keyword(s):  
Secondary Organic Aerosols ◽  
Organic Aerosols

scholarly journals Aerosol chemical and optical properties over the Paris area within ESQUIF project

2006 ◽  
Vol 6 (11) ◽  
pp. 3257-3280 ◽  
Author(s):  
A. Hodzic ◽  
R. Vautard ◽  
P. Chazette ◽  
L. Menut ◽  
B. Bessagnet
Keyword(s):  
Optical Properties ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Dust Particles ◽  
Aerosol Size Distribution ◽  
Aerosol Composition ◽  
Aerosol Mass ◽  
Coarse Mode ◽  
Paris Area ◽  
Flight Trajectories

Abstract. Aerosol chemical and optical properties are extensively investigated for the first time over the Paris Basin in July 2000 within the ESQUIF project. The measurement campaign offers an exceptional framework to evaluate the performances of the chemistry-transport model CHIMERE in simulating concentrations of gaseous and aerosol pollutants, as well as the aerosol-size distribution and composition in polluted urban environments against ground-based and airborne measurements. A detailed comparison of measured and simulated variables during the second half of July with particular focus on 19 and 31 pollution episodes reveals an overall good agreement for gas-species and aerosol components both at the ground level and along flight trajectories, and the absence of systematic biases in simulated meteorological variables such as wind speed, relative humidity and boundary layer height as computed by the MM5 model. A good consistency in ozone and NO concentrations demonstrates the ability of the model to reproduce the plume structure and location fairly well both on 19 and 31 July, despite an underestimation of the amplitude of ozone concentrations on 31 July. The spatial and vertical aerosol distributions are also examined by comparing simulated and observed lidar vertical profiles along flight trajectories on 31 July and confirm the model capacity to simulate the plume characteristics. The comparison of observed and modeled aerosol components in the southwest suburb of Paris during the second half of July indicates that the aerosol composition is rather correctly reproduced, although the total aerosol mass is underestimated by about 20%. The simulated Parisian aerosol is dominated by primary particulate matter that accounts for anthropogenic and biogenic primary particles (40%), and inorganic aerosol fraction (40%) including nitrate (8%), sulfate (22%) and ammonium (10%). The secondary organic aerosols (SOA) represent 12% of the total aerosol mass, while the mineral dust accounts for 8%. The comparison demonstrates the absence of systematic errors in the simulated sulfate, ammonium and nitrates total concentrations. However, for nitrates the observed partition between fine and coarse mode is not reproduced. In CHIMERE there is a clear lack of coarse-mode nitrates. This calls for additional parameterizations in order to account for the heterogeneous formation of nitrate onto dust particles. Larger discrepancies are obtained for the secondary organic aerosols due to both inconsistencies in the SOA formation processes in the model leading to an underestimation of their mass and large uncertainties in the determination of the measured aerosol organic fraction. The observed mass distribution of aerosols is not well reproduced, although no clear explanation can be given.

scholarly journals Understanding the anthropogenic influence on formation of biogenic secondary organic aerosols in Denmark via analysis of organosulfates and related oxidation products

2014 ◽  
Vol 14 (17) ◽  
pp. 8961-8981 ◽  
Author(s):  
Q. T. Nguyen ◽  
M. K. Christensen ◽  
F. Cozzi ◽  
A. Zare ◽  
A. M. K. Hansen ◽  
...  
Keyword(s):  
Organic Acids ◽  
Long Range ◽  
Secondary Organic Aerosols ◽  
Global Radiation ◽  
Organic Aerosols ◽  
Photochemical Reactions ◽  
Common Mechanism ◽  
Aerosol Acidity ◽  
Local Impacts ◽  
Concentration Levels

Abstract. Anthropogenic emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) may affect concentration levels and composition of biogenic secondary organic aerosols (BSOA) through photochemical reactions with biogenic organic precursors to form organosulfates and nitrooxy organosulfates. We investigated this influence in a field study from 19 May to 22 June, 2011 at two sampling sites in Denmark. Within the study, we identified a substantial number of organic acids, organosulfates and nitrooxy organosulfates in the ambient urban curbside and semi-rural background air. A high degree of correlation in concentrations was found among a group of specific organic acids, organosulfates and nitrooxy organosulfates, which may originate from various precursors, suggesting a common mechanism or factor affecting their concentration levels at the sites. It was proposed that the formation of those species most likely occurred on a larger spatial scale, with the compounds being long-range transported to the sites on the days with the highest concentrations. The origin of the long-range transported aerosols was investigated using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model in addition to modeled emissions of related precursors, including isoprene and monoterpenes using the global Model of Emissions of Gases and Aerosols from Nature (MEGAN) and SO2 emissions using the European Monitoring and Evaluation Program (EMEP) database. The local impacts were also studied by examining the correlation between selected species, which showed significantly enhanced concentrations at the urban curbside site and the local concentrations of various gases, including SO2, ozone (O3), NOx, aerosol acidity and other meteorological conditions. This investigation showed that an inter-play of the local parameters such as the aerosol acidity, NOx, SO2, relative humidity (RH), temperature and global radiation seemed to affect the concentration level of those species, suggesting the influence of aqueous aerosol chemistry. The local impacts, however, seemed minor compared to the regional impacts. The total concentrations of organosulfates and nitrooxy organosulfates, on average, contributed to approximately 0.5–0.8% of PM1 mass at the two sampling sites.

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