Heterogeneous Ozone Chemistry Research Articles

Heterogeneous chemistry of ozone with floor cleaning agent: Implications of secondary VOCs in the indoor environment

Human daily activities such as cooking, and cleaning can affect the indoor air quality by releasing primary emitted volatile organic compounds (VOCs), as well as by the secondary product compounds formed through reactions with ozone (O3) and hydroxyl radicals (OH). However, our knowledge about the formation processes of the secondary VOCs is still incomplete. We performed real-time measurements of primary VOCs released by commercial floor-cleaning detergent and the secondary product compounds formed by heterogeneous reaction of O3 with the constituents of the cleaning agent by use of high-resolution mass spectrometry. We measured the uptake coefficients of O3 on the cleaning detergent at different relative humidities in dark and under different light intensities (320 nm < λ < 400 nm) relevant for the indoor environment. On the basis of the detected compounds we developed tentative reaction mechanisms describing the formation of the secondary VOCs. Intriguingly, under light irradiation the formation of valeraldehyde was observed based on the photosensitized chemistry of acetophenone which is a constituent of the cleaning agent. Finally, we modeled the observed mixing ratios of three aldehydes, glyoxal, methylglyoxal, and 4-oxopentanal with respect to real-life indoor environment. The results suggest that secondary VOCs initiated by ozone chemistry can additionally impact the indoor air pollution.

Molecular Characterization of the Product Compounds Formed Upon Heterogeneous Chemistry of Ozone With Riverine Surface Microlayer

AbstractOzone (O3) is an important trace gas and oxidant in the atmosphere which sources and sinks are not well understood. In this study we measured the uptake coefficients of O3 (100 ppb) on authentic riverine surface microlayers (SML) collected on three different places on Pearl River in Guangzhou by a vertical wetted wall flow tube reactor which enables to estimate the deposition velocity of O3 on the fresh water surface. The product compounds formed upon interfacial reactions of O3 with the SML have been investigated by a Fourier transform ion cyclotron resonance mass spectrometry. About 10 times more product compounds were formed upon ozonolysis on the SML sample collected in a transportation hub close to the Estuary zone compared to the products formed upon ozonolysis on the SML sampled at the upper reach of the river at the periphery of Guangzhou. Moreover, 933 nitrogen (N)‐containing organic compounds which are associated with nitrooxy amines, organonitrates, nitroaromatics, and peroxyacetyl nitrates were formed upon heterogeneous reaction of ozone with the SML collected near the Estuary zone compared to 165 N‐containing compounds formed upon ozonolysis of the SML sample collected at the periphery of the city. Hence, the formed condensed phase product compounds through the reactions of ozone with the riverine SML can affect the freshwater biodiversity. An important fraction of brown carbon compounds was formed, which may be released to the air by wind‐wave interactions and influence the chemical composition of the atmosphere and thus, radiative forcing of the aerosols.

Electrolytes Change the Interfacial Water Structure but Not the Vibrational Dynamics.

Heterogeneous ozone chemistry occurring on aerosols is driven by interfacial chemistry and thus affected by the surface state of aerosol particles. Therefore, the effect of electrolytes on the structure of interfacial water has been under intensive investigation. However, consequences for energy dissipation rates and mechanisms at the interface are largely unknown. Using time-resolved sum frequency generation spectroscopy, we reveal that the relaxation pathway is the same for neat water-air as for aqueous solutions of Na2SO4 and Na2CO3. We further show that similar lifetimes are extracted from all investigated systems and that these lifetimes show an excitation frequency dependent relaxation time from 0.2 ps up to 1 ps. Hence, despite static SFG on the same systems revealing that the interfacial aqueous structure changes upon adding electrolytes, the vibrational dynamics are indistinguishable for both pure water and different electrolyte solutions.

Investigating the performance of biomass-derived biochars for the removal of gaseous ozone, adsorbed nitrate and aqueous bisphenol A

In this study, we evaluated for the first time the capacity of six biochars to remove gaseous ozone, adsorbed nitrate and aqueous bisphenol A (BPA). An experimental setup was developed to study the heterogeneous chemistry of ozone and nitrate on the surface of biochars. Biochars showed excellent performance in removing ozone (55 ppbv) for periods up to 24 h, and no volatile byproducts were observed during the reaction process. Challenging biochars with adsorbed nitrate led to the formation of reduced nitrogen oxides (NO and NO2) under UV irradiation. The photoreduction of nitrate was induced by the reduced carbon present in the biochars which led to the formation of nitrite followed by photoreduction to NO in the gas phase and on the surface. Adsorption capacities of biochars for removing BPA from water were also estimated. After long-term aging by ozone, BPA adsorption capacities of all biochars did not change while they were found to decrease slightly after nitrate aging. This could be attributed to partial oxidation of biochar surface as evidenced by infrared analysis and the formation of surface-hydroxyl and -carbonyl groups. This study will allow a better evaluation of biochars as promising materials for removal of air and aqueous pollutants.

Tobacco smoke aging in the presence of ozone: A room-sized chamber study

a b s t r a c t Exposure to tobacco pollutants that linger indoors after smoking has taken place ( thirdhand smoke , THS ) can occur over extended periods and is modulated by chemical processes involving atmospheric reactive species. This study investigates the role of ozone and indoor surfaces in chemical transformations of tobacco smoke residues. Gas and particle constituents of secondhand smoke (SHS) as well as sorbed SHS on chamber internal walls and model materials (cotton, paper, and gypsum wallboard) were charac- terized during aging. After smoldering 10 cigarettes in a 24-m 3 room size chamber, gas-phase nicotine was rapidly removed by sorption to chamber surfaces, and subsequently re-emitted during ventilation with clean air to a level of w10% that during the smoking phase. During chamber ventilation in the presence of ozone (180 ppb), ozone decayed at a rate of 5.6 h ! 1 and coincided with a factor of 5 less nicotine sorbed to wallboard. In the presence of ozone, no gas phase nicotine was detected as a result of re-emission, and higher concentrations of nicotine oxidation products were observed than when ventilation was performed with ozone-free air. Analysis of the model surfaces showed that heteroge- neous nicotine-ozone reaction was faster on paper than cotton, and both were faster than on wallboard. However, wallboard played a dominant role in ozone-initiated reaction in the chamber due to its large total geometric surface area and sink potential compared to the other substrates. This study is the first to show in a room-sized environmental chamber that the heterogeneous ozone chemistry of sorbed nicotine generates THS constituents of concern, as observed previously in bench-top studies. In addition to the main oxidation products (cotinine, myosmine and N-methyl formamide), nicotine-1-oxide was detected for the first time.

Results from a new linear O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; scheme with embedded heterogeneous chemistry compared with the parent full-chemistry 3-D CTM

Abstract. A detailed full-chemistry 3-D chemistry and transport model (CTM) is used to evaluate the current stratospheric O3 parameterisation in the European Centre for Medium-Range Weather Forecasts (ECMWF) model and to obtain an alternative version of the ozone scheme implicitly including heterogeneous chemistry. The approach avoids the inaccurate treatment currently given to heterogeneous ozone chemistry in the ECMWF model, as well as the uncertainties of a cold-tracer. The new O3 scheme (COPCAT) is evaluated within the same CTM used to calculate it. It is the first time such a comparison has been possible, providing direct information on the validity of the linear parameterisation approach for stratospheric ozone. Simulated total column and O3 profiles are compared against Total Ozone Mapping Spectrometer (TOMS) and Halogen Occultation Experiment (HALOE) observations. COPCAT successfully simulates polar loss and reproduces a realistic Antarctic O3 hole. The new scheme is comparable to the full-chemistry in many regions for multiannual runs. The parameterisation produces less ozone over the tropics around 10 hPa, compared to full-chemistry and observations. However, this problem can be ameliorated by choosing a different ozone climatology for the scheme. The new scheme is compared to the current ECMWF scheme in the same CTM runs. The Antarctic O3 hole with the current ECMWF scheme is weaker and disappears earlier than with the new COPCAT scheme. Differences between the current ECMWF scheme and COPCAT are difficult to explain due to the different approach used for heterogeneous chemistry and differences in the photochemical models used to calculate the scheme coefficients. Results with the new COPCAT scheme presented here show that heterogeneous and homogeneous ozone chemistry can be included in a consistent way in a linear ozone parameterisation, without any additional tunable parameters, providing a parameterisation scheme in better agreement with the current knowledge of stratospheric O3 chemistry than previous approaches.

Production of molecular iodine from the heterogeneous reaction of nitrogen dioxide with solid potassium iodide

[1] Molecular iodine impacts tropospheric chemistry, especially in coastal regions of the marine boundary layer where iodine bursts correlate with ultrafine particle formation. Although biogenic sources dominate coastal I2 release, inorganic heterogeneous chemistry may also contribute to the global iodine budget. We investigated the heterogeneous chemistry of NO2/N2O4 with solid KI, a component of dehydrated sea salt aerosol, and identified I2(g) as the major gaseous product. Diffuse reflectance infrared spectroscopy and ion chromatography identified nitrite as the major condensed-phase product for the reaction of KI(s) + NO2(g) (5.4 × 1013 to 2.0 × 1015 molecules cm−3) at relative humidities between 2% and 30%. The reaction was second order with respect to NO2, suggesting that N2O4 was the reactive species. Reactive uptake coefficients, calculated with respect to [N2O4], were independent of relative humidity with an average value of γBET = (6.1 ± 0.3) × 10−4. Concurrent gas phase UV-visible spectroscopy indentified I2(g) production with near stoichiometric release corresponding to 2 KI(s) + N2O4(ads) → 2 KNO2(s) + I2(g). Condensed-phase nitrate was also identified at high [N2O4] and low RH, which was attributed to the oxidation of product KNO2 by gaseous NO2/N2O4. The heterogeneous chemistry of ozone with aqueous iodide has previously been considered as a source of molecular iodine in the marine boundary layer. These results suggest that the heterogeneous chemistry between NO2/N2O4 and iodide deserves further consideration as a nonbiogenic source of molecular iodine.

Ozone trends at northern mid- and high latitudes – a European perspective

Abstract. The EU CANDIDOZ project investigated the chemical and dynamical influences on decadal ozone trends focusing on the Northern Hemisphere. High quality long-term ozone data sets, satellite-based as well as ground-based, and the long-term meteorological reanalyses from ECMWF and NCEP are used together with advanced multiple regression models and atmospheric models to assess the relative roles of chemistry and transport in stratospheric ozone changes. This overall synthesis of the individual analyses in CANDIDOZ shows clearly one common feature in the NH mid latitudes and in the Arctic: an almost monotonic negative trend from the late 1970s to the mid 1990s followed by an increase. In most trend studies, the Equivalent Effective Stratospheric Chlorine (EESC) which peaked in 1997 as a consequence of the Montreal Protocol was observed to describe ozone loss better than a simple linear trend. Furthermore, all individual analyses point to changes in dynamical drivers, such as the residual circulation (responsible for the meridional transport of ozone into middle and high latitudes) playing a key role in the observed turnaround. The changes in ozone transport are associated with variations in polar chemical ozone loss via heterogeneous ozone chemistry on PSCs (polar stratospheric clouds). Synoptic scale processes as represented by the new equivalent latitude proxy, by conventional tropopause altitude or by 250 hPa geopotential height have also been successfully linked to the recent ozone increases in the lowermost stratosphere. These show significant regional variation with a large impact over Europe and seem to be linked to changes in tropospheric climate patterns such as the North Atlantic Oscillation. Some influence in recent ozone increases was also attributed to the rise in solar cycle number 23. Changes from the late 1970s to the mid 1990s were found in a number of characteristics of the Arctic vortex. However, only one trend was found when more recent years are also considered, namely the tendency for cold winters to become colder.

Photosensitized Heterogeneous Chemistry of Ozone on Organic Films

The interactions of ozone with benzophenone and phenol solid films have been investigated under simulated atmospheric conditions with respect to relative humidity, pressure, temperature, and O3 concentration using a coated flow tube reactor. The steady-state reactive uptake coefficients (gammass) of ozone on benzophenone films ranged from below 10(-6) in dark conditions to approximately 4 x 10(-6) under UV-A irradiation and decreased with increasing O3 concentration in the range 28-320 ppbv. A similar trend was observed for the initial uptake coefficient (gammai) which varied from ca. 1.5 x 10(-6) in the dark to approximately 7 x 10(-6) under UV-A irradiation. The uptake coefficients under irradiation were strongly dependent on the relative humidity (from 5 to 70%), with their lowest values at high humidity (70% RH). The ozone uptakes for multilayer coverage turned out to be independent of the deposited mass of the organic compound. The benzophenone-phenol mixture also showed photoenhanced uptake with a larger steady-state uptake under visible irradiation, approximately 2.9 x 10(-6). Contact angle measurements showed an increase of the organic film hydrophobicity for the benzophenone-phenol mixture upon combined exposure to light and ozone. A linear dependence of the kinetic values on the photon flux has been demonstrated and when extrapolated to the solar spectral irradiance would lead to uptake coefficients of approximately 10(-5). UV-vis analysis and contact angle measurements of the organic film after irradiation and ozone exposure showed relevant changes only in the mixture, with an increase in the hydrophobic character of the film and the appearance of a new absorption band up to 450 nm.

Photosensitized Heterogeneous Chemistry of Ozone on Organic Films

Photosensitized Heterogeneous Chemistry of Ozone on Organic Films

Simulation of stratospheric water vapor trends: impact on stratospheric ozone chemistry

Abstract. A transient model simulation of the 40-year time period 1960 to 1999 with the coupled climate-chemistry model (CCM) ECHAM4.L39(DLR)/CHEM shows a stratospheric water vapor increase over the last two decades of 0.7 ppmv and, additionally, a short-term increase after major volcanic eruptions. Furthermore, a long-term decrease in global total ozone as well as a short-term ozone decline in the tropics after volcanic eruptions are modeled. In order to understand the resulting effects of the water vapor changes on lower stratospheric ozone chemistry, different perturbation simulations were performed with the CCM ECHAM4.L39(DLR)/CHEM feeding the water vapor perturbations only to the chemistry part. Two different long-term perturbations of lower stratospheric water vapor, +1 ppmv and +5 ppmv, and a short-term perturbation of +2 ppmv with an e-folding time of two months were applied. An additional stratospheric water vapor amount of 1 ppmv results in a 5–10% OH increase in the tropical lower stratosphere between 100 and 30 hPa. As a direct consequence of the OH increase the ozone destruction by the HOx cycle becomes 6.4% more effective. Coupling processes between the HOx-family and the NOx/ClOx-family also affect the ozone destruction by other catalytic reaction cycles. The NOx cycle becomes 1.6% less effective, whereas the effectiveness of the ClOx cycle is again slightly enhanced. A long-term water vapor increase does not only affect gas-phase chemistry, but also heterogeneous ozone chemistry in polar regions. The model results indicate an enhanced heterogeneous ozone depletion during antarctic spring due to a longer PSC existence period. In contrast, PSC formation in the northern hemisphere polar vortex and therefore heterogeneous ozone depletion during arctic spring are not affected by the water vapor increase, because of the less PSC activity. Finally, this study shows that 10% of the global total ozone decline in the transient model run can be explained by the modeled water vapor increase, but the simulated tropical ozone decrease after volcanic eruptions is caused dynamically rather than chemically.

Impact of dynamically induced ozone mini-hole events on PSC formation and chemical ozone destruction

The impact of ozone mini-holes over the extra-tropics of the northern hemisphere on the heterogeneous ozone chemistry is investigated, based on simulations with the coupled climate-chemistry model ECHAM4.L39(DLR)/CHEM. Ozone mini-holes are synoptic-scale regions of strongly reduced total ozone, directly associated with upper troposphere high pressure systems. The simulated mini-hole events are validated with a mini-hole climatology based on daily ozone measurements with the total ozone mapping spectrometer (TOMS) instrument on the satellite Nimbus-7 between 1979 and 1993. Furthermore, the impact of mini-holes on the stratospheric heterogeneous ozone chemistry is investigated indirectly. For this purpose, polar stratospheric cloud formation inside mini-holes is suppressed during the model simulation. Heterogeneous processes inside mini-holes amount to one third of the heterogeneous ozone destruction in general over northern mid- and high-latitudes during winter (January–April). This ozone perturbation subsides and recovers during summer with an e-folding time of two months.

Assimilation of GOME total‐ozone satellite observations in a three‐dimensional tracer‐transport model

AbstractA data‐assimilation scheme to assimilate the Global Ozone Monitoring Experiment (GOME) total‐ozone data is described. The corresponding software (called TM3DAM) has been operational since early 2000 and is used to produce daily ozone analyses and five‐day ozone forecasts. The model is a tracer‐transport model with a parametrized description of stratospheric gas‐phase and heterogeneous ozone chemistry. It is driven by operational meteorological fields from the ECMWF numerical weather‐prediction model. TM3DAM analyses near‐real‐time level‐2 ozone data from the GOME instrument on the ESA ERS‐2 satellite. The focus of this paper is on the data‐assimilation aspects and the analysis results. The assimilation approach is based on the Kalman‐filter equations and provides detailed and realistic maps of the forecast error. The analysis scheme is nevertheless computationally efficient. The forecast‐minus‐observation statistics, accumulated over a two‐year period, are described in detail. A comparison with TOMS and Brewer observations shows good agreement. Copyright © 2003 Royal Meteorological Society

Impact of ozone mini-holes on the heterogeneous destruction of stratospheric ozone.

A comprehensive study of ozone mini-holes over the mid-latitudes of both hemispheres is presented, based on model simulations with the coupled climate-chemistry model ECHAM4.L39(DLR)/CHEM representing atmospheric conditions in 1960, 1980, 1990 and 2015. Ozone mini-holes are synoptic-scale regions of strongly reduced total ozone, directly associated with tropospheric weather systems. Mini-holes are supposed to have chemical and dynamical impacts on ozone levels. Since ozone levels over northern mid-latitudes show a negative trend of approximately -4%/decade and since it exists a negative correlation between total column ozone and erythemally active solar UV-radiation reaching the surface it is important to understand and assess the processes leading to the observed ozone decline. The simulated mini-hole events are validated with a mini-hole climatology based on daily ozone measurements with the TOMS (total ozone mapping spectrometer) instrument on the satellite Nimbus-7 between 1979 and 1993. Furthermore, possible trends in the event frequency and intensity over the simulation period are assessed. In the northern hemisphere the number of mini-hole events in early winter decreases between 1960 and 1990 and increases towards 2015. In the southern hemisphere a positive trend in mini-hole event frequency is detected between 1960 and 2015 in spring associated with the increasing Antarctic Ozone Hole. Finally, the impact of mini-holes on the stratospheric heterogeneous ozone chemistry is investigated. For this purpose, a computer-based detection routine for mini-holes was developed for the use in ECHAM4.L39(DLR)/CHEM. This method prevents polar stratospheric cloud formation and therefore heterogeneous ozone depletion inside mini-holes. Heterogeneous processes inside mini-holes amount to one third of heterogeneous ozone destruction in general over northern mid- and high-latitudes during winter (January-April) in the simulation.

Electron stimulated desorption of O- and O2- from condensed ozone: Possible implications for the heterogeneous photochemistry of stratospheric O3

We have studied the desorption of negative ions following low energy electron impact (0–15 eV) to ozone condensed in multilayer amounts on a cryogenically cooled gold surface. Intense desorption of O− is observed at low electron energies (below 4 eV) ia pronounced resonances with an estimated desorption cross section of the order of 10−18 cm2 (peak value). The resonant features in the ion yield indicate that O− desorption is driven by dissociative electron attachment to O3 molecules at or near the surface. While dissociative electron attachment (DA) from gas phase ozone generates the fragment ions O− and O2− at comparable intensities, desorption of O2− from condensed ozone is strongly suppressed, being only weakly observed within a resonance located at 7 eV. Possible implications for the heterogeneous chemistry of ozone on polar stratospheric cloud (PSC) particles, namely photo-induced dissociative electron transfer from the substrate, are discussed in the light of the effective O− desorption observed at low electron energies.

Ozone Reactive Chemistry on Interior Latex Paint

The heterogeneous chemistry of ozone on interior latex paint was investigated in a tube flow reactor. The emissions of several polar volatile organic compounds (VOCs) including organic acids and carbonyls (aldehydes and ketones) were measured while a glass tube coated with latex paint was exposed to clean air and ozone. Four different commercial brands of latex paint were tested. Formic and acetic acids were not found to be generated via ozone reactions ; however, both were found to off-gas from the latex paints, and the off-gasing increased with increasing relative humidity. The off-gasing rates are large enough, particularly for acetic acid, to impact residential concentrations significantly. Formaldehyde was found to be produced by reactions related to the ozone concentration. There was some evidence that acetaldehyde and acetone may also be produced by processes related to the ozone concentration. A steady-state model is presented that is used to extrapolate the chamber results to a representative indoor environment. The model is based on an experimentally derived parameter termed the VOC formation factor, which is defined as the number of VOC molecules of a particular species formed via an ozone reaction divided by the total number of ozone molecules sticking to the surface. Using this model, it was found that formaldehyde production via ozone reactions is significant enough to impact indoor concentrations of formaldehyde.

Hand pyrometer with two scale ranges

Exposure to tobacco pollutants that linger indoors after smoking has taken place (thirdhand smoke, THS) can occur over extended periods and is modulated by chemical processes involving atmospheric reactive species. This study investigates the role of ozone and indoor surfaces in chemical transformations of tobacco smoke residues. Gas and particle constituents of secondhand smoke (SHS) as well as sorbed SHS on chamber internal walls and model materials (cotton, paper, and gypsum wallboard) were characterized during aging. After smoldering 10 cigarettes in a 24-m3 room size chamber, gas-phase nicotine was rapidly removed by sorption to chamber surfaces, and subsequently re-emitted during ventilation with clean air to a level of ∼10% that during the smoking phase. During chamber ventilation in the presence of ozone (180 ppb), ozone decayed at a rate of 5.6 h−1 and coincided with a factor of 5 less nicotine sorbed to wallboard. In the presence of ozone, no gas phase nicotine was detected as a result of re-emission, and higher concentrations of nicotine oxidation products were observed than when ventilation was performed with ozone-free air. Analysis of the model surfaces showed that heterogeneous nicotine-ozone reaction was faster on paper than cotton, and both were faster than on wallboard. However, wallboard played a dominant role in ozone-initiated reaction in the chamber due to its large total geometric surface area and sink potential compared to the other substrates. This study is the first to show in a room-sized environmental chamber that the heterogeneous ozone chemistry of sorbed nicotine generates THS constituents of concern, as observed previously in bench-top studies. In addition to the main oxidation products (cotinine, myosmine and N-methyl formamide), nicotine-1-oxide was detected for the first time.