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Articoli di riviste sul tema "Tropospheric halogens":
1
Caram, Cyril, Sophie Szopa, Anne Cozic, Slimane Bekki, Carlos A. Cuevas e Alfonso Saiz-Lopez. "Sensitivity of tropospheric ozone to halogen chemistry in the chemistry–climate model LMDZ-INCA vNMHC". Geoscientific Model Development 16, n. 14 (18 luglio 2023): 4041–62. http://dx.doi.org/10.5194/gmd-16-4041-2023.
Abstract (sommario):
Abstract. The atmospheric chemistry of halogenated species (Cl, Br, I) participates in the global chemical sink of tropospheric ozone and perturbs the oxidising capacity of the troposphere, notably by influencing the atmospheric lifetime of methane. Global chemistry–climate models are commonly used to assess the global budget of ozone and its sensitivity to emissions of its precursors, as well as to project its long-term evolution. Here, we report on the implementation of tropospheric sources and chemistry of halogens in the chemistry–climate model LMDZ-INCA (Laboratoire de Météorologie Dynamique general circulation model, LMDZ, and Interactions with Chemistry and Aerosols, INCA, version with Non-Methane HydroCarbon chemistry, vNMHC) and evaluate halogen effects on the tropospheric ozone budget. Overall, the results show that the model simulates satisfactorily the impact of halogens on the photo-oxidising system in the troposphere, in particular in the marine boundary layer. To quantify the effects of halogen chemistry in LMDZ-INCA, standard metrics representative of the behaviour of the tropospheric chemical system (Ox, HOx, NOx, CH4 and non-methane volatile organic compounds – NMVOCs) are computed with and without halogens. The addition of tropospheric halogens in the LMDZ-INCA model leads to a decrease of 22 % in the ozone burden, 8 % in OH and 33 % in NOx. Sensitivity simulations show for the first time that the inclusion of halogen chemistry makes ozone more sensitive to perturbations in CH4, NOx and NMVOCs. Consistent with other global model studies, the sensitivity of the tropospheric ozone burden to changes from pre-industrial to present-day emissions is found to be ∼20 % lower when tropospheric halogens are taken into account.
2
Sherwen, Tomás, Mat J. Evans, Lucy J. Carpenter, Johan A. Schmidt e Loretta J. Mickley. "Halogen chemistry reduces tropospheric O<sub>3</sub> radiative forcing". Atmospheric Chemistry and Physics 17, n. 2 (31 gennaio 2017): 1557–69. http://dx.doi.org/10.5194/acp-17-1557-2017.
Abstract (sommario):
Abstract. Tropospheric ozone (O3) is a global warming gas, but the lack of a firm observational record since the preindustrial period means that estimates of its radiative forcing (RFTO3) rely on model calculations. Recent observational evidence shows that halogens are pervasive in the troposphere and need to be represented in chemistry-transport models for an accurate simulation of present-day O3. Using the GEOS-Chem model we show that tropospheric halogen chemistry is likely more active in the present day than in the preindustrial. This is due to increased oceanic iodine emissions driven by increased surface O3, higher anthropogenic emissions of bromo-carbons, and an increased flux of bromine from the stratosphere. We calculate preindustrial to present-day increases in the tropospheric O3 burden of 113 Tg without halogens but only 90 Tg with, leading to a reduction in RFTO3 from 0.43 to 0.35 Wm−2. We attribute ∼ 50 % of this reduction to increased bromine flux from the stratosphere, ∼ 35 % to the ocean–atmosphere iodine feedback, and ∼ 15 % to increased tropospheric sources of anthropogenic halogens. This reduction of tropospheric O3 radiative forcing due to halogens (0.087 Wm−2) is greater than that from the radiative forcing of stratospheric O3 (∼ 0.05 Wm−2). Estimates of RFTO3 that fail to consider halogen chemistry are likely overestimates (∼ 25 %).
3
Wang, Siyuan, Johan A. Schmidt, Sunil Baidar, Sean Coburn, Barbara Dix, Theodore K. Koenig, Eric Apel et al. "Active and widespread halogen chemistry in the tropical and subtropical free troposphere". Proceedings of the National Academy of Sciences 112, n. 30 (29 giugno 2015): 9281–86. http://dx.doi.org/10.1073/pnas.1505142112.
Abstract (sommario):
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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Long, M. S., W. C. Keene, R. C. Easter, R. Sander, X. Liu, A. Kerkweg e D. Erickson. "Sensitivity of tropospheric chemical composition to halogen-radical chemistry using a fully coupled size-resolved multiphase chemistry/global climate system – Part 1: Halogen distributions, aerosol composition, and sensitivity of climate-relevant gases". Atmospheric Chemistry and Physics Discussions 13, n. 3 (7 marzo 2013): 6067–129. http://dx.doi.org/10.5194/acpd-13-6067-2013.
Abstract (sommario):
Abstract. Observations and model studies suggest a significant but highly non-linear role for halogens, primarily Cl and Br, in multiphase atmospheric processes relevant to tropospheric chemistry and composition, aerosol evolution, radiative transfer, weather, and climate. The sensitivity of global atmospheric chemistry to the production of marine aerosol and the associated activation and cycling of inorganic Cl and Br was tested using a size-resolved multiphase coupled chemistry/global climate model (National Center for Atmospheric Research's Community Atmosphere Model (CAM); v3.6.33). Simulation results showed strong meridional and vertical gradients in Cl and Br species. The simulation reproduced most available observations with reasonable confidence permitting the formulation of potential mechanisms for several previously unexplained halogen phenomena including the enrichment of Br− in submicron aerosol, and the presence of a BrO maximum in the polar free troposphere. However, simulated total volatile Br mixing ratios were generally high in the troposphere. Br in the stratosphere was lower than observed due to the lack of long-lived organobromine species in the simulation. Comparing simulations using chemical mechanisms with and without reactive Cl and Br species demonstrated a significant temporal and spatial sensitivity of primary atmospheric oxidants (O3, HOx, NOx), CH4, and non-methane hydrocarbons (NMHC's) to halogen cycling. Simulated O3 and NOx were globally lower (65% and 35%, respectively, less in the planetary boundary layer based on median values) in simulations that included halogens. Globally, little impact was seen in SO2 and non-sea-salt SO42− processing due to halogens. Significant regional differences were evident: the lifetime of nss-SO42− was extended downwind of large sources of SO2. The burden and lifetime of DMS (and its oxidation products) were lower by a factor of 5 in simulations that included halogens, versus those without, leading to a 20% reduction in nss-SO42− in the Southern Hemisphere planetary boundary layer based on median values.
5
Lary, D. J. "Halogens and the chemistry of the free troposphere". Atmospheric Chemistry and Physics Discussions 4, n. 5 (16 settembre 2004): 5367–80. http://dx.doi.org/10.5194/acpd-4-5367-2004.
Abstract (sommario):
Abstract. The role of halogens in both the marine boundary layer and the stratosphere has long been recognized, while their role in the free troposphere is often not considered in global chemical models. However, a careful examination of free-tropospheric chemistry constrained by observations using a full chemical data assimilation system shows that halogens do play a significant role in the free troposphere. In particular, the chlorine initiation of methane oxidation in the free troposphere can contribute more than 10%, and in some regions up to 50%, of the total rate of initiation. The initiation of methane oxidation by chlorine is particularly important below the polar vortex and in northern mid-latitudes. Likewise, the hydrolysis of alone can contribute more than 35% of the production rate in the free-troposphere.
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Lary, D. J. "Halogens and the chemistry of the free troposphere". Atmospheric Chemistry and Physics 5, n. 1 (27 gennaio 2005): 227–37. http://dx.doi.org/10.5194/acp-5-227-2005.
Abstract (sommario):
Abstract. The role of halogens in both the marine boundary layer and the stratosphere has long been recognized, while their role in the free troposphere is often not considered in global chemical models. However, a careful examination of free-tropospheric chemistry constrained by observations using a full chemical data assimilation system shows that halogens do play a significant role in the free troposphere. In particular, the chlorine initiation of methane oxidation in the free troposphere can contribute more than 10%, and in some regions up to 50%, of the total rate of initiation. The initiation of methane oxidation by chlorine is particularly important below the polar vortex and in northern mid-latitudes. Likewise, the hydrolysis of alone can contribute more than 35% of the production rate in the free-troposphere.
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Cadoux, Anita, Susann Tegtmeier e Alessandro Aiuppa. "Natural Halogen Emissions to the Atmosphere: Sources, Flux, and Environmental Impact". Elements 18, n. 1 (1 febbraio 2022): 27–33. http://dx.doi.org/10.2138/gselements.18.1.27.
Abstract (sommario):
Understanding the atmospheric geochemical cycle of both natural and anthropogenic halogens is important because of the detrimental effect halogens have on the environment, notably on tropospheric and stratospheric ozone. Oceans are the primary natural source for atmospheric Cl, F, Br, and I, but anthropogenic emissions are still important, especially for Cl. While emissions of human-made halocarbons (e.g., chlorofluorocarbons or CFCs) are expected to continue to decrease allowing progressive stratospheric ozone recovery, volcanic activity (e.g., clusters of mid-scale explosive eruptions or large-scale explosive eruptions) might disturb this recovery over the next decades. This review provides a synthesis of natural halogen fluxes from oceanic, terrestrial, and volcanic sources, and discusses the role of natural halogen species on atmosphere chemistry and their environmental impact.
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Sherwen, Tomás, Johan A. Schmidt, Mat J. Evans, Lucy J. Carpenter, Katja Großmann, Sebastian D. Eastham, Daniel J. Jacob et al. "Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem". Atmospheric Chemistry and Physics 16, n. 18 (29 settembre 2016): 12239–71. http://dx.doi.org/10.5194/acp-16-12239-2016.
Abstract (sommario):
Abstract. We present a simulation of the global present-day composition of the troposphere which includes the chemistry of halogens (Cl, Br, I). Building on previous work within the GEOS-Chem model we include emissions of inorganic iodine from the oceans, anthropogenic and biogenic sources of halogenated gases, gas phase chemistry, and a parameterised approach to heterogeneous halogen chemistry. Consistent with Schmidt et al. (2016) we do not include sea-salt debromination. Observations of halogen radicals (BrO, IO) are sparse but the model has some skill in reproducing these. Modelled IO shows both high and low biases when compared to different datasets, but BrO concentrations appear to be modelled low. Comparisons to the very sparse observations dataset of reactive Cl species suggest the model represents a lower limit of the impacts of these species, likely due to underestimates in emissions and therefore burdens. Inclusion of Cl, Br, and I results in a general improvement in simulation of ozone (O3) concentrations, except in polar regions where the model now underestimates O3 concentrations. Halogen chemistry reduces the global tropospheric O3 burden by 18.6 %, with the O3 lifetime reducing from 26 to 22 days. Global mean OH concentrations of 1.28 × 106 molecules cm−3 are 8.2 % lower than in a simulation without halogens, leading to an increase in the CH4 lifetime (10.8 %) due to OH oxidation from 7.47 to 8.28 years. Oxidation of CH4 by Cl is small (∼ 2 %) but Cl oxidation of other VOCs (ethane, acetone, and propane) can be significant (∼ 15–27 %). Oxidation of VOCs by Br is smaller, representing 3.9 % of the loss of acetaldehyde and 0.9 % of the loss of formaldehyde.
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Lehrer, E., G. Hönninger e U. Platt. "The mechanism of halogen liberation in the polar troposphere". Atmospheric Chemistry and Physics Discussions 4, n. 3 (28 giugno 2004): 3607–52. http://dx.doi.org/10.5194/acpd-4-3607-2004.
Abstract (sommario):
Abstract. Sudden depletions of tropospheric ozone during spring were reported from the Arctic and also from Antarctic coastal sites. Field studies showed that those depletion events are caused by reactive halogen species, especially bromine compounds. However the source and seasonal variation of reactive halogen species is still not completely understood. There are several indications that the halogen mobilisation from the sea ice surface of the polar oceans may be the most important source for the necessary halogens. Here we present a 1-D model study aimed at determining the primary source of reactive halogens. The model includes gas phase and heterogeneous bromine and chlorine chemistry as well as vertical transport between the surface and the top of the boundary layer. The autocatalytic Br release by photochemical processes (bromine explosion) and subsequent rapid bromine catalysed ozone depletion is well reproduced in the model and the major source of reactive bromine appears to be the sea ice surface. The sea salt aerosol alone is not sufficient to yield the high levels of reactive bromine in the gas phase necessary for fast ozone depletion. However, the aerosol efficiently 'recycles' less reactive bromine species (e.g. HBr) and feeds them back into the ozone destruction cycle. Isolation of the boundary layer air from the free troposphere by a strong temperature inversion was found to be critical for boundary layer ozone depletion to happen. The combination of strong surface inversions and presence of sunlight occurs only during polar spring.
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Lehrer, E., G. Hönninger e U. Platt. "A one dimensional model study of the mechanism of halogen liberation and vertical transport in the polar troposphere". Atmospheric Chemistry and Physics 4, n. 11/12 (6 dicembre 2004): 2427–40. http://dx.doi.org/10.5194/acp-4-2427-2004.
Abstract (sommario):
Abstract. Sudden depletions of tropospheric ozone during spring were reported from the Arctic and also from Antarctic coastal sites. Field studies showed that those depletion events are caused by reactive halogen species, especially bromine compounds. However the source and seasonal variation of reactive halogen species is still not completely understood. There are several indications that the halogen mobilisation from the sea ice surface of the polar oceans may be the most important source for the necessary halogens. Here we present a one dimensional model study aimed at determining the primary source of reactive halogens. The model includes gas phase and heterogeneous bromine and chlorine chemistry as well as vertical transport between the surface and the top of the boundary layer. The autocatalytic Br release by photochemical processes (bromine explosion) and subsequent rapid bromine catalysed ozone depletion is well reproduced in the model and the major source of reactive bromine appears to be the sea ice surface. The sea salt aerosol alone is not sufficient to yield the high levels of reactive bromine in the gas phase necessary for fast ozone depletion. However, the aerosol efficiently "recycles" less reactive bromine species (e.g. HBr) and feeds them back into the ozone destruction cycle. Isolation of the boundary layer air from the free troposphere by a strong temperature inversion was found to be critical for boundary layer ozone depletion to happen. The combination of strong surface inversions and presence of sunlight occurs only during polar spring.
Tesi sul tema "Tropospheric halogens":
1
Choi, Sungyeon. "Investigation of tropospheric bro using space-based total column bro measurements". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43682.
Abstract (sommario):
We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL). Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo >0.7), for solar zenith angle <80 degree and clear sky conditions. The rapid activation of BrO due to surface processes (the bromine explosion) is apparent in both the OMI and GOME-2 based tropospheric columns. The wide orbital swath of OMI allows examination of the evolution of tropospheric BrO on about hourly time intervals near the pole. Low surface pressure, strong wind, and high PBL height are associated with an observed BrO activation event, supporting the notion of bromine activation by high winds over snow. We also provide monthly climatological maps of free tropospheric BrO volume mixing ratio (VMR) derived using the so-called cloud slicing technique. In this approach, the derived slope of the total column BrO versus cloud pressure is proportional to free tropospheric BrO VMR. Estimated BrO VMR shows a minimum in the tropics and greater values at higher latitudes in both hemispheres. High tropospheric BrO VMR at high latitudes in spring could be influenced by near-surface bromine activation.
2
Galeazzo, Tommaso. "Tracking volcanic sulphate : modelling tropospheric volcanic sulphate formation and its oxygen isotopic signatures". Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS300.
Abstract (sommario):
Les émissions volcaniques sont une source importante de soufre. Le soufre volcanique est oxydé et forme des aérosols sulfatés qui influencent le climat en absorbant et en dispersant le rayonnement solaire incident. Les émissions de soufre dans la troposphère influencent le climat local et régional, mais de grandes incertitudes subsistent en ce qui concerne l’oxydation et sa conversion en aérosols de sulfate volcanique. L’oxydation du soufre dans une vaste gamme de panaches volcaniques et l’influence des halogènes volcaniques sur la chimie du panache sont étudiées à l’aide d’un modèle de boîte chimique. Parallèlement, la composition isotopique en oxygène du sulfate volcanique, à savoir l’excès de 17-O (∆17O), est à l’étude, ce qui peut limiter les voies d’oxydation du soufre. Les résultats suggèrent qu’en présence de gouttelettes d’eau et de cendres, l’oxydation du soufre dans les panaches est principalement due à l’oxydation en phase aqueuse avec de l’O2 catalysé par des ions de métaux de transition (TMI). Les émissions d’halogènes favorisent la dominance de l’O2 /TMI en induisant des phénomènes d’appauvrissement de la couche d’ozone (ODE). En l’absence de gouttelettes d’eau, la chimie du panache est largement déterminée par la chimie hétérogène des aérosols primaires sulfatés. Les oxydants dominants dans ces panaches sont OH et H2O2. Le taux d’oxydation du soufre est considérablement réduit par rapport aux panaches contenant des gouttelettes d’eau. Les résultats montrent que les isotopes de l’oxygène dans les sulfates exercent de fortes contraintes sur l’équilibre chimique du soufre dans les panaches volcaniques et sur le rôle des halogènes volcaniquesVolcanic emissions are a major source of sulphur. Volcanic sulphur is oxidized and forms sulphate aerosols that influence the climate by absorbing and dispersing incident solar radiation. Sulphur emissions in the troposphere influence local and regional climate, but large uncertainties remain regarding oxidation and its conversion into volcanic sulphate aerosols. The oxidation of sulphur in a wide range of volcanic plumes and the influence of volcanic halogens on plume chemistry are studied using a chemical box model. At the same time, the isotopic oxygen composition of volcanic sulphate, namely the excess of 17-O (∆17O), is being explored, which can provide constraints on sulphur oxidation pathways. The results suggest that in the presence of water droplets and ash, the oxidation of sulphur in plumes is mainly due to aqueous phase oxidation with O2 catalyzed by transition metal ions (TMI). Halogen emissions promote the domi- nance of O2 /TMI by inducing ozone depletion events (ODEs). In the absence of water droplets, plume chemistry is largely determined by heterogeneous chemistry on primary sulphate aerosols. The dominant oxidants in these plumes are OH and H2O2. The oxidation rate of sulphur is significantly reduced compared to plumes containing water droplets. The results show that oxygen isotopes in sulphates provide strong constraints on the chemical balance of sulphur in volcanic plumes and on the role of volcanic halogens
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Caram, Cyril. "Rôle et fonctionnement des atmosphères naturelles ou faiblement polluées dans la régulation de la capacité oxydante de l’atmosphère terrestre". Electronic Thesis or Diss., université Paris-Saclay, 2021. http://www.theses.fr/2021UPASJ008.
Abstract (sommario):
La chimie des espèces halogénées (Cl, Br, I) dans l’atmosphère joue un rôle, à l’échelle mondiale, dans le puits chimique d'ozone troposphérique, gaz à effet de serre et source principale du radical hydroxyle (OH). Par conséquent, la chimie des composés halogénés peut affecter le radical OH dont la concentration est assimilée au pouvoir oxydant de la troposphère, et ainsi modifier le temps de vie de gaz à effet de serre comme le méthane. Néanmoins, cette chimie est rarement représentée pour la troposphère dans les modèles de chimie climat. Le modèle numérique tridimensionnel de chimie-climat LMDz-INCA, qui est inclus dans le modèle de système Terre de l’IPSL, a été utilisé tout au long de cette thèse pour comprendre et quantifier le rôle de la chimie des composés halogénés sur la chimie troposphérique photooxydante dans des atmosphères naturelles. Dans un premier temps, les espèces halogénées, leurs sources d’émissions vers l’atmosphère et leurs puits physiques, leurs réactions chimiques ont été intégrées dans INCA. Un important travail d’évaluation des résultats du modèle pour une simulation de référence d’un an a été réalisé en confrontant ces résultats à des synthèses d’observations in-situ des concentrations de composés halogénés et aux résultats de modèles équivalents. Il a été démontré que la représentation de cette chimie était suffisamment satisfaisante pour simuler l’impact des halogènes sur le système photooxydant dans la troposphère et particulièrement dans la couche limite atmosphérique. La réponse du système chimique troposphérique Ox, HOx, NOx, CH4 et COVs à ces changements a ainsi pu être quantifiée. À l’échelle de toute la troposphère, la charge massique d’O3 diminue de 22%, celle d’OH de 8% et celle des NOx de 33% lors de la prise en compte de la chimie des espèces halogénées.Pour mieux appréhender l’ampleur de ces changements sur la capacité oxydante et en comprendre les mécanismes, des tests de sensibilités, consistant à diminuer tour à tour les émissions ou concentrations des précurseurs de l’ozone, ont été réalisés. Ceux-ci ont montré qu’avec la prise en compte de la chimie des composés halogénés, l’O3 devient plus sensible aux perturbations en NOx, CH4 et COV. Par contre, le radical OH devient plus résilient face à ces perturbations puisqu’il devient moins dépendant de l’O3 et plus dépendant de ses autres sources chimiques, espèces halogénées y compris. La comparaison entre les simulations pour des conditions préindustrielles et présentes ont montré que la sensibilité de la charge massique d’ozone troposphérique aux changements d’émissions qui se sont déroulées depuis 1850 est ~20% plus faible lorsque la chimie des composés halogénés est prise en compte. Afin de mieux comprendre la résilience du radical OH face à des changements d’émissions, la probabilité de recyclage a été quantifiée. Dans un scénario préindustriel, r augmente de 12% ce qui montre l’importance de la considération de la chimie des composés halogénés pour explorer la chimie oxydante des atmosphères du passé. Pour les conditions actuelles, r dépasse 60% en moyenne mondiale, suggérant qu’un effet tampon sur les concentrations d’OH se met en place. L’impact de la chimie des composés halogénés étant important sur les changements de charge massique de l’ozone et la capacité oxydante, entre l’époque préindustrielle et aujourd’hui, les exercices internationaux s’intéressant à l’évolution de ces espèces entre le préindustriel, le présent et le futur auraient intérêt à considérer cette chimie pour mieux caractériser le forçage radiatif lié notamment à l’ozoneThe atmospheric chemistry of halogenated species (Cl, Br, I) plays a role in the global chemical sink of tropospheric ozone, a greenhouse gas that is also the main source of hydroxyl radicals (OH). As a consequence, the chemistry of halogenated compounds can perturb OH, whose concentration reflects the oxidizing capacity of the troposphere, and can therefore influence the atmospheric lifetime of greenhouse gases such as methane. Despite this, tropospheric chemistry of halogen is rarely described in climate-chemistry models. The LMDz-INCA 3-D climate-chemistry model, which is part of the IPSL Earth system model, has been used throughout this thesis to understand and quantify the role of tropospheric halogenated compounds on the photooxidizing chemistry in natural atmospheres. First, the halogenated species, their emission sources and physical sinks, their chemistry were integrated into INCA. A one-year reference simulation was used to carry out an in depth model evaluation. Comparisons were made with compilations of in-situ observations of some halogenated species and with the results from similar models. The representation of this chemistry was shown to correctly simulate the impact of halogens on the photooxidizing system in the troposphere and in particular in the boundary layer. The changes affecting the tropospheric chemical system (Ox, HOx, NOx, CH4 and VOCs) were thus quantified. The chemistry of halogenated species was shown to decrease O3 burden by 22%, that of OH by 8% and that of NOx by 33%.Second, to better understand the effect on the oxidizing capacity, sensitivity tests, consisting of reducing independently the emissions or concentrations of ozone precursors, were carried out. They show that in the presence of the chemistry of halogenated compounds, O3 becomes more sensitive to perturbations in NOx, CH4 and VOC. On the other hand, the OH radical becomes more resilient to these changes since it becomes less dependent on O3 and more dependent on its other chemical sources, which include halogenated species. The comparison between pre-industrial and present-day simulations show that the sensitivity of the tropospheric ozone burden is ~20% lower when the chemistry of halogenated compounds is considered. In order to better understand the resilience of the OH radical to changes in emissions, the recycling probability of OH (r) was quantified. In a pre-industrial scenario, r increases by 12%, thus emphasizing the importance of considering the chemistry of halogens in exploring the oxidative chemistry of past atmospheres. For current conditions, r exceeds 60% on a global average, suggesting that a buffering effect on OH concentrations is occurring. Since changes in ozone burden and oxidative capacity between pre-industrial and present-day simulations are considerable, international exercises aiming at assessing the evolution of these species over the preindustrial, the present and the future periods should account for the role of tropospheric chemistry of halogenated compounds to better quantify the ozone radiative forcing
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Impey, Gary A. "Photolyzable halogens in the Arctic troposphere". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0027/NQ39274.pdf.
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Enami, Shinichi. "Halogen cycles in the stratosphere and troposphere". 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/136139.
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Allan, Beverley. "A spectroscopic study of radical chemistry in the troposphere". Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266729.
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Sihler, Holger [Verfasser], e Ulrich [Akademischer Betreuer] Platt. "Halogen Activation in the Polar Troposphere / Holger Sihler ; Betreuer: Ulrich Platt". Heidelberg : Universitätsbibliothek Heidelberg, 2012. http://d-nb.info/1179786041/34.
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Viswanathan, Balakrishnan. "Theoretical investigation of mercury reactions with halogen species in the Arctic troposphere". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33038.
Abstract (sommario):
Mercury is one of the most toxic elements present in the geosphere, present in many chemical and physical forms. Nearly uniform mixing ratios are observed within a hemisphere, the concentration being higher in the northern than in the Southern Hemisphere. Lack of kinetic data regarding mercury reactions prevents an explanation of the behaviour and deposition pathways of mercury from the atmosphere. Theoretical calculations have been carried out using DFT theory to investigate the thermodynamics and kinetics of the reactions of Hg0 with Cl, Br, ClO, and BrO radicals and with Cl 2 and Br2. The results from these calculations were used to evaluate the kinetic rate constants at 298.15 K and 238.15 K for the reactions involving gaseous mercury. In this paper, the results of this study are presented and relevance to the chemistry of the Arctic is discussed.
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Cao, Le [Verfasser], e Eva [Akademischer Betreuer] Gutheil. "Numerical Investigation of Tropospheric Halogen Release and Ozone Depletion in the Polar Spring / Le Cao ; Betreuer: Eva Gutheil". Heidelberg : Universitätsbibliothek Heidelberg, 2014. http://d-nb.info/1179924622/34.
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Leather, Kimberley. "Tropospheric ozone and photochemical processing of hydrocarbons : laboratory based kinetic and product studies". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/tropospheric-ozone-and-photochemical-processing-of-hydrocarbons-laboratory-based-kinetic-and-product-studies(39b76a99-2358-4db2-be58-baa75d18efea).html.
Abstract (sommario):
Laboratory based temperature-dependent kinetics and product yields for alkene ozonolysis and the reaction of CH3O2 with ClO and BrO have been measured via chamber studies and a turbulent flow tube coupled to CIMS (Chemical Ionisation Mass Spectrometry). In order to gain a better understanding of the fate of the products formed during hydrocarbon oxidation and their subsequent impact on the ozone budget (and so the oxidising capacity of the atmosphere) it is imperative to know the rate at which these reactions proceed and to identify their product yields. As tropospheric temperature varies, Arrhenius parameters were determined during the ozonolysis of selected alkenes. The temperature dependent kinetic database was extended and the activation energies for the ozonolysis of selected alkenes were correlated with an existing SAR (Structure Activity Relationship). Given the myriad organic species in the atmosphere, SARs are useful tools for the prediction of rate coefficients. Inclusion of Arrhenius parameters into the SAR allows for prediction over a range of temperatures, improving the conditions reflected in models. Achieving mass balance for alkene ozonolysis has proven to be a difficult challenge considering the numerous pathways of the Criegee Intermediate (CI). The product yield of formic acid – an organic acid with significant atmospheric implications which is under predicted by models – was determined as a function of relative humidity during ethene ozonolysis. This reaction exhibited a strong water dependence which lead to the prediction of the reaction rate of the CI with water which ranges between 1 × 10-12 – 1 × 10-15 cm3 molecule-1 s-1 and will therefore dominate its loss with respect to bimolecular processes in the atmosphere. Peroxy radicals, strongly influence the total oxidising capacity of the troposphere. The reaction of peroxy radicals with halogen oxides is recognised to be responsible for considerable ozone depletion in the atmosphere, exacerbated by reactive halogens (X, XO) taking part in catalytic cycles. Arrhenius parameters were determined for ClO + CH3O2 and BrO + CH3O2. Temperature is an important parameter affecting rate, exemplified here as the reaction involving ClO exhibited a positive temperature dependence whereas for BrO a negative temperature dependence was evident. As a consequence, the impact of ClO + CH3O2 with respect to ozone loss is diminished. Global modelling predicts a reduction in ozone loss by a factor of around 1.5 and implicates regions such as clean marine environments rather than the polar stratosphere. Conversely, a more pronounced temperature dependence for the reaction of BrO with CH3O2 placed particular importance on lower stratospheric chemistry where the modelled CH3O2 oxidation is doubled. The main products for this reaction were identified to be HOBr and CH2O2. The decomposition of CH2O2 could enhance HOx in the lower and middle stratosphere and contribute to a significant source of HOx in the upper troposphere. Bimolecular reaction of CH2O2 with water could also provide a none negligible source HC(O)OH in the upper troposphere. Alkenes and peroxy radicals undergo chemical processing in the atmosphere whilst acting as a source and sink of ozone and thus can impose detrimental effects on the biosphere, climate and air quality of the Earth.
Libri sul tema "Tropospheric halogens":
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"HALOE algorithm improvements for upper tropospheric sounding": Yearly progress report, NRA-97-MTPE-04. [Washington, DC: National Aeronautics and Space Administration, 1999.
Capitoli di libri sul tema "Tropospheric halogens":
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Molina, Mario J. "Chemical Interactions of Tropospheric Halogens on Snow/Ice". In The Tropospheric Chemistry of Ozone in the Polar Regions, 273–79. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-78211-4_19.
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Lavigne, J. Allen, e Cooper H. Langford. "Liquid Phase Photochemistry in Relation to Tropospheric Chemistry of Halogens". In The Tropospheric Chemistry of Ozone in the Polar Regions, 307–16. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-78211-4_22.
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Hanson, David R., e A. R. Ravishankara. "Reactions of Halogen Species on Ice Surfaces". In The Tropospheric Chemistry of Ozone in the Polar Regions, 281–90. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-78211-4_20.
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Wine, P. H., J. M. Nicovich, R. E. Stickel, Z. Zhao, C. J. Shackelford, K. D. Kreutter, E. P. Daykin e S. Wang. "Halogen and Sulfur Reactions Relevant to Polar Chemistry". In The Tropospheric Chemistry of Ozone in the Polar Regions, 385–95. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-78211-4_28.
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Sander, Stanley P., Scott L. Nickolaisen e Randall R. Friedl. "ClO + ClO → Products: A Case Study in Halogen Monoxide Disproportionation and Recombination Reactions". In The Tropospheric Chemistry of Ozone in the Polar Regions, 337–49. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-78211-4_24.
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Platt, U. "Reactive Halogen Species in the Mid-Latitude Troposphere — Recent Discoveries". In Environmental Challenges, 229–44. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4369-1_20.
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Platt, Ulrich. "The Impact of Halogen Chemistry on the Oxidation Capacity of the Troposphere". In Global Atmospheric Change and its Impact on Regional Air Quality, 67–75. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0082-6_11.
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von Glasow, R., e P. J. Crutzen. "Tropospheric Halogen Chemistry". In Treatise on Geochemistry, 1–67. Elsevier, 2003. http://dx.doi.org/10.1016/b0-08-043751-6/04141-4.
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von Glasow, R., e P. J. Crutzen. "Tropospheric Halogen Chemistry". In Treatise on Geochemistry, 19–69. Elsevier, 2014. http://dx.doi.org/10.1016/b978-0-08-095975-7.00402-2.
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Calvert, Jack G., John J. Orlando, William R. Stockwell e Timothy J. Wallington. "The Impact of Inorganic Trace Gases on Ozone in the Atmosphere". In The Mechanisms of Reactions Influencing Atmospheric Ozone. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190233020.003.0010.
Abstract (sommario):
A major focus of the previous six chapters has been on the chemistry and interactions of the HOx, NOx, and volatile organic compound (VOC) families. Details of the reactions of O3 NO3, and HO that act to initiate VOC oxidation have been presented, as has the ensuing chemistry involving organic peroxy and alkoxy radicals and their interactions with NOx. In this chapter, we complete our discussion of thermal chemical reactions that impact tropospheric ozone. The chapter begins with a discussion of the budgets of two simple (inorganic) carbon-containing species not yet discussed, carbon dioxide (CO2) and carbon monoxide (CO). Although CO2 is not directly involved in ozone-related tropospheric chemistry, it is of course the species most critical to discussions of global climate change, and thus a very brief overview of its concentrations, sources, and sinks is presented. CO is a ubiquitous global pollutant, and its reaction with HO is an essential part of the tropospheric background chemistry. This is followed by a presentation of the tropospheric chemistry of halogen species, beginning with a discussion of inorganic halogen cycles that impact (in particular) the ozone chemistry of the marine boundary layer (MBL) and concluding with a detailed presentation of the reactions of Cl atoms and Br atoms with VOC species. The chapter concludes with an overview of tropospheric sulfur chemistry. The reactions leading to the oxidation of inorganic (SO2 and SO3) as well as organic sulfur compounds (e.g., DMS, CH3SCH3) are detailed, and a brief discussion of the effects of the oxidation of sulfur species on aerosol production in the troposphere and stratosphere is also given. The abundance of CO2 in the atmosphere has obviously received a great deal of attention in recent decades due to the influence of this gas on Earth’s climate system. Indeed, changes in the atmospheric CO2 concentration represent the single largest contributor to changes in radiative forcing since preindustrial times (c. 1750). The atmospheric burden of CO2 is controlled by the processes that make up the global carbon cycle—the exchanges of carbon (mostly in the form of CO2) between various “reservoirs,” including the atmosphere, land (vegetation and soil), the surface ocean, the intermediate and deep ocean, sediment on the ocean floor, and the fossil fuel reservoir (IPCC, 2007).
Atti di convegni sul tema "Tropospheric halogens":
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Cao, Le, e Eva Gutheil. "Modeling and Simulation of Tropospheric Ozone Depletion in the Polar Spring". In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-22045.
Abstract (sommario):
In polar spring, tropospheric ozone depletion is related to the presence of halogen oxide concentrations in the atmospheric boundary layer. Halogen oxides such as BrO participate in an autocatalytic chemical reaction cycle, leading to the release of Br2 and BrCl from the fresh sea ice. The paper presents the identification of a detailed chemical reaction mechanism for the ozone depletion event, where bromine plays the major role. The heterogeneous reactions in the chemical reaction mechanism are studied in detail, and a sensitivity analysis is performed to identify the importance of each reaction in the mechanism. A skeletal reaction scheme is identified on the basis of the sensitivity analysis,. This skeletal chemical reaction mechanism then is used in a 3-D large eddy simulation (LES) with the Smagorinsky sub-grid model. The configuration studied includes a mountain located at the ground above which the ozone depletion is studied. In this situation, the height of the boundary layer varies, which greatly affects the ozone depletion event.
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Gunson, M. R., M. C. Abrams, C. B. Farmer, L. L. Lowes, C. P. Rinsland e R. Zander. "Results from the flight of the Atmospheric Trace Molecule Spectroscopy on the ATLAS-1 Space Shuttle Mission". In Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/orsa.1993.ma.4.
Abstract (sommario):
During the ATLAS-1 space shuttle mission, the ATMOS experiment, a Fourier transform infrared spectrometer operating in solar occultation mode from on-orbit (Farmer, 1987), collected data through more than 90 orbital sunrises and sunsets at latitudes between 30°N and 55°S. The resulting high-resolution infrared solar absorption spectra from these observations have so far been analyzed for the vertical profiles of several species (O3, HNO3, ClNO3, HCl, HF, N2O, CH4 and H2O) of immediate importance as correlative measurements for other satellite instruments, such as those carried on the Upper Atmospheric Research Satellite. Results for these gases together with those of other species measured by ATMOS, such as the more abundant man-made chlorofluorocarbons (CFC-11, CFC-12, HCFC-22) are compared with similar measurements made by this instrument from data acquired during its first flight in April, 1985. In the period between these two flights, the halogenated gases are expected to have increased measurably in concentration due to the continued release of the halogenated source gases. These ATMOS data provide a simultaneous measurement of the increase in the tropospheric source gases as well as the halogen sink species, HCl and HF.
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Russell, J. M., L. L. Gordley, J. H. Park e S. R. Drayson. "HALOE Observations of Ozone, Halogen, Nitrogen, and Hydrogen Compounds Made from the UARS Platform". In Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/orsa.1993.thd.3.
Abstract (sommario):
The Halogen Occultation Experiment (HALOE) was launched September 12, 1991, by the Space Shuttle Discovery into a 57°, 585-km, near-circular orbit onboard the Upper Atmosphere Research Satellite (UARS). The experiment was allowed to outgass for about 1 month before science observations began on October 11, 1991. The experiment approach is solar occultation. The instrument technique uses the principle of gas-filter radiometry in four channels to measure vertical profiles of HCℓ, HF, CH4, and NO, and broadband radiometry in four other channels to measure NO2, H2O, O3, and CO2. The latter channel is used for pressure registration and temperature versus pressure sounding of the atmosphere. Methane measurements extend to about 70 km, H2O and temperature to 80 km, O3 to 90 km, HCℓ and HF to ≈ 60 km, NO2 to ≈ 55 km, and NO to 120 km altitude. Results from this experiment have provided the first pressure versus latitude cross sections of HCℓ, HF, and NO, including continuous measurements of NO from the upper troposphere, in some cases, to the lower thermosphere. The data set will be used to pursue a number of scientific investigations, including stratospheric photochemistry and dynamics studies, evaluation of the impact of natural versus anthropogenic chlorine sources on total chlorine, the effect of volcanic aerosols on the chemistry, and study of Antarctic processes which occur during the ozone hole development and recovery phases.