Abstract:Abstract. The Dead Sea is an excellent natural laboratory for the investigation of Reactive Bromine Species (RBS) chemistry, due to the high RBS levels observed in this area, combined with anthropogenic air pollutants up to several ppb. The present study investigated the basic chemical mechanism of RBS at the Dead Sea using a numerical one-dimensional chemical model. Simulations were based on data obtained from comprehensive measurements performed at sites along the Dead Sea. The simulations showed that the hi… Show more
“…However, results from both studies differ significantly from what is presented by Tas et al (2006) and their follow up paper (Tas et al, 2008). Below we list the main differences in the model approaches used in this study and the study by Tas et al (2006).…”
Section: Literature Comparisoncontrasting
confidence: 45%
“…1). It has been suggested several times that due to the very high bromide content and low pH of the Dead Sea water and thus of emitted sea salt aerosol particles the above explained process leads to extraordinary high BrO mixing ratios and the related ODEs (Tas et al, 2003(Tas et al, , 2005(Tas et al, , 2006. Two, very general points speak against this hypothesis (i) The wind speed over the Dead Sea is often low.…”
Section: Motivationmentioning
confidence: 76%
“…In their model calculations, Tas et al (2006) consider aerosols as the only gas phase bromine source.…”
Section: Literature Comparisonmentioning
confidence: 99%
“…Smoydzin and R. von Glasow: Modelling chemistry over the Dead Sea study by Tas et al (2006) tries to explain the high bromine levels observed at the Dead Sea by using a model setup including only the source for gas phase bromine by the release of bromine species from sea salt aerosols which are emitted from the Dead Sea water. They suggest that sea salt aerosols are the predominant source of bromine for the atmosphere above the Dead Sea.…”
Abstract. Measurements of O 3 and BrO concentrations over the Dead Sea indicate that Ozone Depletion Events (ODEs), widely known to happen in polar regions, are also occuring over the Dead Sea due to the very high bromine content of the Dead Sea water. However, we show that BrO and O 3 levels as they are detected cannot solely be explained by high Br − levels in the Dead Sea water and the release of gas phase halogen species out of sea borne aerosol particles and their conversion to reactive halogen species. It is likely that other sources for reactive halogen compounds are needed to explain the observed concentrations for BrO and O 3 . To explain the chemical mechanism taking place over the Dead Sea leading to BrO levels of several pmol/mol we used the one-dimensional model MISTRA which calculates microphysics, meteorology, gas and aerosol phase chemistry. We performed pseudo Lagrangian studies by letting the model column first move over the desert which surrounds the Dead Sea region and then let it move over the Dead Sea itself. To include an additional source for gas phase halogen compounds, gas exchange between the Dead Sea water and the atmosphere is treated explicitly. Model calculations indicate that this process has to be included to explain the measurements.
“…However, results from both studies differ significantly from what is presented by Tas et al (2006) and their follow up paper (Tas et al, 2008). Below we list the main differences in the model approaches used in this study and the study by Tas et al (2006).…”
Section: Literature Comparisoncontrasting
confidence: 45%
“…1). It has been suggested several times that due to the very high bromide content and low pH of the Dead Sea water and thus of emitted sea salt aerosol particles the above explained process leads to extraordinary high BrO mixing ratios and the related ODEs (Tas et al, 2003(Tas et al, , 2005(Tas et al, , 2006. Two, very general points speak against this hypothesis (i) The wind speed over the Dead Sea is often low.…”
Section: Motivationmentioning
confidence: 76%
“…In their model calculations, Tas et al (2006) consider aerosols as the only gas phase bromine source.…”
Section: Literature Comparisonmentioning
confidence: 99%
“…Smoydzin and R. von Glasow: Modelling chemistry over the Dead Sea study by Tas et al (2006) tries to explain the high bromine levels observed at the Dead Sea by using a model setup including only the source for gas phase bromine by the release of bromine species from sea salt aerosols which are emitted from the Dead Sea water. They suggest that sea salt aerosols are the predominant source of bromine for the atmosphere above the Dead Sea.…”
Abstract. Measurements of O 3 and BrO concentrations over the Dead Sea indicate that Ozone Depletion Events (ODEs), widely known to happen in polar regions, are also occuring over the Dead Sea due to the very high bromine content of the Dead Sea water. However, we show that BrO and O 3 levels as they are detected cannot solely be explained by high Br − levels in the Dead Sea water and the release of gas phase halogen species out of sea borne aerosol particles and their conversion to reactive halogen species. It is likely that other sources for reactive halogen compounds are needed to explain the observed concentrations for BrO and O 3 . To explain the chemical mechanism taking place over the Dead Sea leading to BrO levels of several pmol/mol we used the one-dimensional model MISTRA which calculates microphysics, meteorology, gas and aerosol phase chemistry. We performed pseudo Lagrangian studies by letting the model column first move over the desert which surrounds the Dead Sea region and then let it move over the Dead Sea itself. To include an additional source for gas phase halogen compounds, gas exchange between the Dead Sea water and the atmosphere is treated explicitly. Model calculations indicate that this process has to be included to explain the measurements.
“…30,[59][60][61][62][63][64][65][66][67][68][69][70][71] These reactive halogen gases play a significant role in the chemistry and composition of the marine boundary layer (MBL). 45,[72][73][74][75][76][77][78][79][80][81] In the coastal MBL, the photochemical cycling of chlorine enhances tropospheric ozone, whereas gaseous bromine species cause ozone destruction during polar sunrise in polar regions 75,76,[82][83][84][85] as well as in midlatitudes. [78][79][80][81]86,87 However, despite laboratory and field measurements of halogen gases, the mechanisms responsible for halogen release, including those associated with reactive intermediates from nitrate ion photochemistry, are not well understood.…”
aNitrate and halide ions coexist in particles generated in marine regions, around alkaline dry lakes, and in the Arctic snowpack. Although the photochemistry of nitrate ions in bulk aqueous solution is well known, there is recent evidence that it may be more efficient at liquid-gas interfaces, and that the presence of other ions in solution may enhance interfacial reactivity. This study examines the 311 nm photolysis of thin aqueous films of ternary halide-nitrate salt mixtures (NaCl-NaBr-NaNO 3 ) deposited on the walls of a Teflon chamber at 298 K. The films were generated by nebulizing aqueous 0.25 M NaNO 3 solutions which had NaCl and NaBr added to vary the mole fraction of halide ions. Molar ratios of chloride to bromide ions were chosen to be 0.25, 1.0, or 4.0. The subsequent generation of gas phase NO 2 and reactive halogen gases (Br 2 , BrCl and Cl 2 ) were monitored with time. The rate of gas phase NO 2 formation was shown to be enhanced by the addition of the halide ions to thin films containing only aqueous NaNO 3 .] r 1.0, the NO 2 enhancement was similar to that observed for binary NaBr-NaNO 3 mixtures, while with excess chloride NO 2 enhancement was similar to that observed for binary NaCl-NaNO 3 mixtures. Molecular dynamics simulations predict that the halide ions draw nitrate ions closer to the interface where a less complete solvent shell allows more efficient escape of NO 2 to the gas phase, and that bromide ions are more effective in bringing nitrate ions closer to the surface. The combination of theory and experiments suggests that under atmospheric conditions where nitrate ion photochemistry plays a role, the impact of other species such as halide ions should be taken into account in predicting the impacts of nitrate ion photochemistry.
About 90 % of the main constituents of earth's atmosphere (nitrogen and oxygen), and most atmospheric trace constituents exists in the troposphere. Almost all trace species found in the troposphere are substances emitted from anthropogenic and/or natural sources on the ground, and from volcanoes and aircraft into the free troposphere. The exceptions are O 3 and other secondary products formed by the chemical reactions in the atmosphere, or produced by lightning such as NO. Tropospheric chemistry is a research field for studying a series of processes as a system, including the identification and quantification of emission sources, chemical reactions and transport in the atmosphere, transformation from the gas phase molecules to liquid and/or solid particles, and deposition to clouds and fog, raindrops, and earth surface. Tropospheric chemistry is the most important fundamental discipline for various air pollution issues on the global, regional and urban scales that affect the social life of human beings. For the integrated management of air pollution global warming/climate change, atmospheric chemistry, particularly tropospheric chemistry, provides important scientific knowledge together with atmospheric physics and meteorology. As for atmospheric /tropospheric chemistry as a holistic system science, many textbooks have been published in recent decades (for example,
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