Atmospheric SO2 Research Articles

Numerical modelling of Cz-β-Ga2O3 crystal growth in reactive atmosphere

The present study focuses on computer modeling of Cz- β-Ga2O3 crystal growth while also addressing the issue of minimizing Ir crucible oxidation. To accomplish this objective, a comprehensive framework was developed that combines thermodynamic equilibrium calculations with a CFD numerical model. This integrated approach is designed to simulate the impact of SO2 gas concentration in the chamber atmosphere. The primary goal of this numerical model is to assess deviations from the stoichiometric ratio in the Ga2O3 melt by examining the processes taking place at the free surface of the melt and their effects on its stoichiometry. These processes include the dissociation of the Ga2O3 melt into Ga and O ions, as well as the evaporation of volatile species from the melt surface.Simulations were conducted for both 2-inch and 4-inch crystals, with varying concentrations of SO2 and CO2 in an Ar atmosphere, facilitating a direct comparison between the two gases. The study's findings indicate that the optimal concentration of SO2 in the atmosphere should be approximately 40%, whereas for CO2, the optimal concentration is around 9%. Significantly reduced concentrations of both SO2 and CO2 were achieved by increasing the free melt surface area. Notably, the atmosphere with a SO2 concentration exhibited a substantial 30% reduction in the O concentration surrounding the crucible, underlining the advantages of using SO2 as a viable alternative to CO2.

Enhanced Sulfate Formation from Gas-Phase SO2 Oxidation in Non–•OH–Radical Environments

Recent research on atmospheric particle formation has shown substantial discrepancies between observed and modeled atmospheric sulfate levels. This is because models mostly consider sulfate originating from SO2 oxidation by •OH radicals in mechanisms catalyzed by solar radiation while ignoring other pathways of non-radical SO2 oxidation that would substantially alter atmospheric sulfate levels. Herein, we use high-level quantum chemical calculations based on density functional theory and coupled cluster theory to show that monoethanolamine (MEA), a typical alkanolamine pollutant released from CO2 capture technology, can facilitate the conversion of atmospheric SO2 to sulfate in a non–•OH–radical oxidation mechanism. The initial process is the MEA-induced SO2 hydrolysis leading to the formation of HOSO2−•MEAH+. The latter entity is thereafter oxidized by ozone (O3) and nitrogen dioxide (NO2) to form HSO4−•MEAH+, which is an identified stabilizing entity in sulfate-based aerosol formation. Results show that the HOSO2−•MEAH+ reaction with O3 is kinetically and thermodynamically more feasible than the reaction with NO2. The presence of an additional water molecule further promotes the HOSO2−•MEAH+ reaction with O3, which occurs in a barrierless process, while it instead favors HONO formation in the reaction with NO2. The investigated pathway highlights the potential role alkanolamines may play in SO2 oxidation to sulfate, especially under conditions that are not favorable for •OH production, thereby providing an alternative sulfate source for aerosol modeling. The studied mechanism is not only relevant to sulfate formation and may effectively compete with reactions with sulfur dioxide and hydroxyl radicals under heavily polluted and highly humid conditions such as haze events, but also an important pathway in MEA removal processes.

Unraveling the impact of SO2 on electron transfer and oxygen vacancy over MnOx-CeO2 for ozone decomposition

Mn-based catalysts for O3 decomposition (deO3) in industrial flue gas suffer from serious deactivation due to SO2, especially its impact on surface electron transfer and oxygen vacancy remains unclear. Herein, irreversible deactivation over MnOx-CeO2 in presence of SO2 and H2O was mainly attributed to the decrease of surface area, low-temperature reducibility and oxygen vacancies (Vo). SO2 was easily adsorbed on MnOx-CeO2 and further oxidized into SO42− under the aid of O3. Electron transfer from SO2 to Mn4+ and Ce4+ produced stable and inactive metal sulfates, which inhibited electron transfer in the redox cycles between Mn and O in O3 and between Mn and Ce. Moreover, metal sulfates occupied Vo, while Vo generation became difficult and its recovery from desorption of adsorbed oxygen intermediates was restricted, hence less O3 could be adsorbed and decomposed. Metal Ce protected active Mn species by reacting with SO2 preferentially. H2O generated active hydroxyl groups on Vo to react with O3 and hindered the contact of SO2 with Mn species, increasing deO3 activity under SO2 atmosphere. This study offers new insights into the poisoning mechanism of SO2 on electron transfer and oxygen vacancy in deO3 process, and sheds light on rational design of anti-SO2 deO3 catalysts.

Geochemical and Photochemical Constraints on S[IV] Concentrations in Natural Waters on Prebiotic Earth

AbstractAqueous S[IV] species (, ) derived from volcanogenic atmospheric SO2 are important to planetary habitability through their roles in proposed origins‐of‐life chemistry and influence on atmospheric sulfur haze formation, but the early cycling of S[IV] is poorly understood. Here, we combine new laboratory constraints on S[IV] disproportionation kinetics with a novel aqueous photochemistry model to estimate the concentrations of S[IV] in natural waters on prebiotic Earth. We show that S[IV] disproportionation is slow in pH ≥ 7 waters, with timescale T ≥ 1 year at room temperature, meaning that S[IV] was present in prebiotic natural waters. However, we also show that photolysis of S[IV] by UV light on prebiotic Earth limited [S[IV]] < 100 µM in global‐mean steady‐state. Because of photolysis, [S[IV]] was much lower in natural waters compared to the concentrations generally invoked in laboratory simulations of origins‐of‐life chemistry (≥10 mM), meaning further work is needed to confirm whether laboratory S[IV]‐dependent prebiotic chemistries could have functioned in nature. [S[IV]] ≥ 1 µM in terrestrial waters for: (a) SO2 outgassing ≥20× modern, (b) pond depths <10 cm, or (c) UV‐attenuating agents present in early waters or the prebiotic atmosphere. Marine S[IV] was sub‐saturated with respect to atmospheric SO2, meaning that atmospheric SO2 deposition was efficient and that, within the constraints of present knowledge, UV‐attenuating sulfur hazes could only have persisted on prebiotic Earth if sulfur emission rates were very high (≳100× modern). Our work illustrates the synergy between planetary science, geochemistry and synthetic organic chemistry toward understanding the emergence and maintenance of life on early Earth.

So2 aerosol removal: The cause of global warming

Archived satellite images of atmospheric SO2 aerosols show that their decrease since 1980, due to global “Clean Air” efforts and Net Zero activities, is the cause of all of our modern warming. To avoid even more warming, and their associated environmental disasters, these activities need to be abandoned.

Impacts of Air Pollution and Thermal Discomfort in Hospitalizations for Multiple Sclerosis in Sao Paulo, Brazil

Multiple sclerosis (MS) is an autoimmune, neurological, and demyelinating disease of unknown etiology. Neuroinflammation caused by the disease has been associated with air pollution as well as bioclimatic conditions. The aim of this study was to investigate the impacts of air pollution and human thermal discomfort on hospitalizations for multiple sclerosis in Sao Paulo, Brazil, from 2008 to 2015. Generalized Additive Model for Location Scale and Shape (GAMLSS) with Zero Inflated Poisson was used to relate multiple sclerosis hospitalizations in three age groups (less than 30 years old, between 30 and 50 years old, and more than 50 years old) and gender (female and male) with atmospheric pollutants PM10, SO2, NO2, NO, and NOx and thermal discomfort. The results showed that the exposure to an increase of 1 µg/m3 in SO2 concentration is highly associated with a 10% increase of the risk of MS hospitalization (95% CI: 2–21%) in female patients and a 7.5% (95% CI: 1.5–16%) increase in male patients. PM10 and NO were associated with increased MS risk only for female patients, mainly aged between 30 and 50 years old (2% and 1% increase in hospitalizations, respectively). The cold discomfort was also associated with MS hospitalization, mainly in males (2% increase in hospitalizations; 95% IC: 1–3%). These results are important, since there are few studies that relate air pollution and thermal discomfort with hospitalizations for multiple sclerosis in Brazil.

Induced synthesis of SO2-promoting and H2O-tolerant sorbents for elemental mercury removal from flue gas

In this study, novel S-doped sorbents synthesized via one-step co-pyrolysis of biomass and scrap tires under SO2 atmosphere were developed for elemental mercury (Hg0) removal from coal-fired flue gas. The presence of SO2 could regulate the sulfur species in S-doped sorbents and improve their Hg0 removal performance. Sample characterization exhibited that SO2 activation increased the sulfur content and decreased the carbon content in sorbents due to the occurrence of carbothermal reduction reaction. The specific surface area, pore volume, and micropore content in S-doped sorbents were obviously improved compared with raw sorbents. After SO2 activation, partial inorganic sulfide was converted into sulfur-containing functional groups and more oxygen-containing functional groups were generated on the sorbents. The S-doped sorbents presented more excellent performance for Hg0 removal compared with raw sorbents. The optimal pyrolysis temperature and SO2 concentration in activation atmosphere were 700 °C and 10%, respectively. It was surprising that SO2 facilitated Hg0 removal and the S-doped sorbents showed good water-resistance due to the presence of ZnS. O2 and NO had positive effects on Hg0 removal. A close fitting to the pseudo-second-order model was obtained for the behavior of Hg0 removal over S-doped sorbents. Aliphatic sulfur, sulfoxide, carbonyl and carboxyl/ester groups functioned as active components for Hg0 removal.

Investigation of the LAIC mechanism of the Haiti earthquake (August 14, 2021) using CSES-01 satellite observations and other earthquake precursors

A powerful Mw = 7.2 earthquake occurred in Haiti on August 14, 2021 at 12:29:08 UTC (18.434° N, 73.482° W, depth ∼10 km). In this study, in a period of three months from June 1 to August 31, 2021, the variations in electron density and temperature parameters obtained from CSES-01 satellite measurements in the Dobrovolsky’s area the Haiti earthquake are considered. With the aim of investigating the proposed mechanisms for interactions between different layers of the Earth in the process of earthquakes (LAIC-Lithospheric Atmospheric Ionospheric Coupling), the behavior of 48 other precursors obtained from the data of other satellites in the same location and time period were analyzed. These precursors are 1) TEC obtained from GPS satellite data, 2) scalar and vector magnetic field data as well as electron density and temperature measured by the related sensors of three Swarm A, B and C satellites during day and night and 3) Variations in lithospheric and atmospheric parameters NO2 and SO2 obtained from OMI satellite measurements and also Ozone, carbon monoxide and surface temperature parameters obtained from AIRS data. By analyzing the above mentioned precursors, abnormal behaviors are observed around 30 and 50 days before the earthquake, and especially 1 to 15 days before the earthquake and by comparative study of the observed anomalies, possible LAIC mechanisms are discussed. The findings of this study can acknowledge the sequence of seismic anomalies observed in the lithosphere, then the atmosphere and finally the ionosphere. Therefore, this study once again emphasizes the necessity of performing multi-precursor analysis with the aim of justifying the LAIC mechanism and also observing seismically prone anomalies in the time period of about 10 days before powerful earthquakes.

Significant Enhanced SO2 Resistance of Pt/SiO2 Catalysts by Building the Ultrathin Metal Oxide Shell for Benzene Catalytic Combustion.

A noble metal catalyst shows excellent low-temperature oxidation activity in the catalytic combustion of benzene but has the problem of SO2 poisoning. We all know that SO2 easily competes with the reactant molecules for adsorption of the active site and has electronic effects on the active site to deactivate the catalyst. Therefore, the sulfur resistance of catalysts is the key problem to be solved in the process of catalytic combustion of benzene. Herein, the Pt/SiO2 catalyst with an ordered mesoporous structure was prepared by a one-step hydrothermal method, and MgO, ZnO, and MnOx were, respectively, coated on the surface of Pt/SiO2 as ultrathin shells to improve the sulfur resistance of Pt/SiO2. We observed that the sulfur resistance of the Pt/SiO2 catalyst was significantly improved due to the protective effect of the metal oxide shell. By comparing the three core-shell catalysts, it was found that the Pt/SiO2@MnOx catalyst coated with a MnOx shell had the best performance. The reason was that the MnOx shell not only protected the Pt active site but also had a good electron transfer effect on the core Pt, so it could effectively avoid the rapid adsorption poisoning of SO2 on the active Pt0 site. In addition, it was verified that the excellent redispersion of MnOx species in a SO2 atmosphere could increase the low-temperature oxidation activity of the Pt/SiO2@MnOx catalyst. Meanwhile, in situ DRIFT results also confirmed that the MnOx shell could significantly promote the oxidation of benzene molecules in the SO2 atmosphere.

Oxalate-Promoted SO2 Uptake and Oxidation on Iron Minerals: Implications for Secondary Sulfate Aerosol Formation.

Mineral dust serves as a significant source of sulfate aerosols by mediating heterogeneous sulfur dioxide (SO2) oxidation in the atmosphere. Given that a considerable proportion of small organic acids are deposited onto mineral dust via long-range transportation, understanding their impact on atmospheric SO2 transformation and sulfate formation is of great importance. This study investigates the effect of oxalate on heterogeneous SO2 uptake and oxidation phenomenon by in situ FTIR, theoretical calculation, and continuous stream experiments, exploiting hematite (Fe2O3) as an environmental indicator. The results highlight the critical role of naturally deposited oxalate in mononuclear monodentate coordinating surface Fe atoms of Fe2O3 that enhances the activation of O2 for oxidizing SO2 into sulfate. Meanwhile, oxalate increases the hygroscopicity of Fe2O3, facilitating H2O dissociation into reactive hydroxyl groups and further augmenting the SO2 uptake capacity of Fe2O3. More importantly, other conventional iron minerals, such as goethite and magnetite, as well as authentic iron-containing mineral dust, exhibit similar oxalate-promoted sulfate accumulation behaviors. Our findings suggest that oxalate-assisted SO2 oxidation on iron minerals is one of the important contributors to secondary sulfate aerosols, especially during the nighttime with high relative humidity.

Atmospheric corrosion and impact toughness of steels: Case study in steels with and without galvanizing, exposed for 3 years in Rapa Nui Island

We studied atmospheric corrosion on Rapa Nui Island, using galvanized and non-galvanized SAE 1020 steel samples exposed on racks. We also added Charpy samples of both materials to directly determine the effect of corrosion rate on these materials' impact toughness. The results indicated a correlation between corrosion rate and toughness loss in the studied materials. In the corrosion study, we could also demonstrate the effect from increased insular population growth on contaminants which aid atmospheric corrosivity. Results showed that atmospheric SO2 has tripled compared with similar corrosion studies done 20 years ago (Mapa Iberoamericano de Corrosión, MICAT), increasing corrosion rates. Our results show how human factors can influence changes in environmental variables that strengthen corrosion.

Edge-Enriched Molybdenum Disulfide Ultrathin Nanosheets with a Widened Interlayer Spacing for Highly Efficient Gaseous Elemental Mercury Capture.

Transition metal sulfides have exhibited remarkable advantages in gaseous elemental mercury (Hg0) capture under high SO2 atmosphere, whereas the weak thermal stability significantly inhibits their practical application. Herein, a novel N,N-dimethylformamide (DMF) insertion strategy via crystal growth engineering was developed to successfully enhance the Hg0 capture ability of MoS2 at an elevated temperature for the first time. The DMF-inserted MoS2 possesses an edge-enriched structure and an expanded interlayer spacing (9.8 Å) and can maintain structural stability at a temperature as high as 272 °C. The saturated Hg0 adsorption capacities of the DMF-inserted MoS2 were measured to be 46.91 mg·g-1 at 80 °C and 27.40 mg·g-1 at 160 °C under high SO2 atmosphere. The inserted DMF molecules chemically bond with MoS2, which prevents possible structural collapse at a high temperature. The strong interaction of DMF with MoS2 nanosheets facilitates the growth of abundant defects and edge sites and enhances the formation of Mo5+/Mo6+ and S22- species, thereby improving the Hg0 capture activity at a wide temperature range. Particularly, Mo atoms on the (100) plane represent the strongest active sites for Hg0 oxidation and adsorption. The molecule insertion strategy developed in this work provides new insights into the engineering of advanced environmental materials.

Dynamic Modulation of SO2 Atmosphere for Enhanced Fresh-Keeping of Grapes Using a Novel Starch-Based Biodegradable Foam Packaging.

To improve the fresh-keeping of highly perishable fruits with high commercial value, a novel starch-based foam packaging material was developed in this study. The foam incorporated the antiseptic ingredient Na2S2O5, which chemically interacted with environmental moisture to release SO2 as an antifungal agent. Scanning electron microscopy (SEM), moisture absorption and mechanical measurements were used to characterize the unique sandwich-like inner structure of the foam which allowed for the modulable release of SO2. The starch-based foam exhibited sufficient resilience (~100%) to provide ideal cushioning to prevent physical damage to fresh fruits during transportation. When 25 g/m2 of Na2S2O5 was applied, the foam stably released over 100 ppm SO2 and demonstrated satisfactory antifungal performance (inhibition over 60%) in terms of maintaining the appearance and nutritional values (such as soluble solids 14 vs. 11%, total acidity 0.45 vs. 0.30%, and Vitamin C 3.4 vs. 2.5 mg/100 g) of fresh grapes during a 21 day storage period. Additionally, the residual SO2 (14 mg/kg) also meets the safety limits (<30 mg/kg). These research findings suggest great potential for the utilization of this novel foam in the food industry.

Insight into the contributions of primary emissions of sulfate, nitrate, and ammonium from residential solid fuels to ambient PM2.5

Understanding the primary emissions of sulfate (SO42−), nitrate (NO3−), and ammonium (NH4+) (SNA) from solid fuels (coal and biomass) combustion is important to study their roles in haze formation and particle growth. In this study, direct emissions of SNA and other inorganic ions (including Na+, K+, Mg2+, Ca2+, and Cl−) in fine particulate matter (PM2.5) from residential coal combustion (RCC) and biomass burning (BB) were quantified through combustion chamber experiments. Emission factors (EFs) of the total quantified ions for the five types of solid fuels are in the range of 178–3880 mg/kg, accounting for 5.8%–41.1% of the emitted PM2.5 mass. The average proportions of SO42−, NO3−, and NH4+ in PM2.5 emitted from RCC are 3.7%, 0.9%, and 1.0%, respectively, in comparison to 1.3%, 0.8%, and 0.1%, respectively, for BB. Despite the variations of SNA proportions seen among the solid fuel types, SO42− is the most dominating inorganic ion, consistent with the emission profiles shown in other literatures. Similar mass fraction and its range of SO42− are found between RCC and ambient in the northern cities, implying that the primary emission from RCC is a significant source contributor to atmospheric SO42−, particularly in wintertime. According to the EFs and mass fractions of SNA determined for the solid fuels, the contribution of secondary formation to atmospheric SO42− should be overestimated in ambient PM2.5 source apportionment.

Ni-doped HfSe2 monolayer as a gas scavenger toward SO2 and SOF2: a DFT study

In this work, the adsorption behavior of a monolayer of HfSe2 (Ni-HfSe2) decorated with a Ni catalyst toward the SF6 decomposed gases SO2 and SOF2 is examined using the first-principles theory. On the pure HfSe2 surface, Ni atom as the catalyst substitutes the Se atom. This theoretical work investigates the geometry configurations of Ni-HfSe2 monolayers both before and after gas adsorption, as well as the electronic properties and sensitivities. The greater performance of the Ni-HfSe2 monolayer on the SO2 molecule is implied by the simulation's calculation of the of SO2 and SOF2 gas adsorption systems as −2.21 eV and −0.68 eV, respectively. This is further verified by the DOS, BS and WF analyses. The formula predicts that the Ni-HfSe2 monolayer can detect SO2 and SOF2 with sensitivity up to −80.89% and 105.59%, respectively, at room temperature (298 K), which demonstrates the sensor's advantageous sensitivity to both gases as a chemical resistance-type sensor. It is hopeful that a Ni-HfSe2 monolayer-based gas sensor will be able to distinguish between SO2 and SOF2 in a single gas atmosphere. In conclusion, this study may promote the steady operation of the power system and provide some guidance for cutting-edge electrical engineering resistance-type sensing materials.

Human health risk assessment of air pollutants in the largest coal mining area in Brazil.

The Candiota region, located in the extreme south of Brazil, has the largest mineral coal deposit in the country, and this activity is capable of releasing pollutants in which they are associated with the contamination of different matrices (soil, water, and air). The present study aimed to carry out a risk assessment to human health of atmospheric pollutants NO2 and SO2 and PM10-bound metal(loid)s in the municipality of Candiota, in addition to evaluating the correlation of meteorological parameters for the dynamics and potential risk of these pollutants. Pollutants were sampled from stations located almost 4km from coal exploration activities, and the trace elements As, Cd, Se, Pb, and Ni, in addition to NO2 and SO2, were evaluated. Risk assessment was conducted taking into account the risk to adults via the inhalation route. During the sampling period, all pollutants presented values lower than national legislation or internationally accepted values, and Pb was the element that presented the highest values throughout the sampled period. The risk assessment showed no carcinogenic and non-carcinogenic risks, even when considering the sum of the risk of all analyzed pollutants. It can be observed that the highest levels of Pb, As, and Se occurred in the winter season, while the levels of Ni and Cd were higher in the spring, and the meteorological parameters were correlated with the pollutants, even using a temporal lag of 5days. Although the air pollutants evaluated did not present a risk to human health, continuous monitoring of regions with strong mineral exploration activity must be carried out with a view to maintaining the well-being of exposed populations, mainly because there are people living in areas closer to sources of coal pollution than distance to air quality monitoring stations.

Forest growth responds more to air pollution than soil acidification.

The forests of central Europe have undergone remarkable transitions in the past 40 years as air quality has improved dramatically. Retrospective analysis of Norway spruce (Picea abies) tree rings in the Czech Republic shows that air pollution (e.g. SO2 concentrations, high acidic deposition to the forest canopy) plays a dominant role in driving forest health. Extensive soil acidification occurred in the highly polluted "Black Triangle" in Central Europe, and upper mineral soils are still acidified. In contrast, acidic atmospheric deposition declined by 80% and atmospheric SO2 concentration by 90% between the late 1980s and 2010s. In this study we oserved that annual tree ring width (TRW) declined in the 1970s and subsequently recovered in the 1990s, tracking SO2 concentrations closely. Furthermore, recovery of TRW was similar in unlimed and limed stands. Despite large increases in soil base saturation, as well as soil pH, as a result of repeated liming starting in 1981, TRW growth was similar in limed and unlimed plots. TRW recovery was interrupted in 1996 when highly acidic rime (originating from more pronounced decline of alkaline dust than SO2 from local power plants) injured the spruce canopy, but recovered soon to the pre-episode growth. Across the long-term site history, changes in soil chemistry (pH, base saturation, Bc/Al soil solution ratio) cannot explain observed changes in TRW at the two study sites where we tracked soil chemistry. Instead, statistically significant recovery in TRW is linked to the trajectory of annual SO2 concentrations or sulfur deposition at all three stands.

The Cause of “Atmospheric Rivers”

Extreme flooding due to ”Atmospheric Rivers” has been observed for centuries, but they are considered to be natural events, with no known explanation for their occurrence. However, it has been observed that they are always preceded by periods of higher temperatures caused by volcanic droughts (periods of 4-5 years without any VEI4 or higher volcanic eruptions), where there are no remaining volcanic Sulfur Dioxide (SO2) aerosols circulating in Earth’s atmosphere, or other instances where atmospheric SO2 aerosol levels have been reduced, such as during American business recessions, (due to idled foundries, factories, etc.). With lower levels of SO2 aerosol pollution in the atmosphere, temperatures rise, and heat waves, droughts, famines, and torrential downpours happen around the world.

Investigating the hygroscopicities of calcium and magnesium salt particles aged with SO2 using surface plasmon resonance microscopy

The hygroscopicities of calcium and magnesium salts strongly affect the environment and climate, but the aging products of these salts at high relative humidities (RHs) are still poorly understood. In this study, surface plasmon resonance microscopy (SPRM) was used to determine the hygroscopic growth factors (GFs) of Ca(NO3)2 and Mg(NO3)2 separately or mixed with galactose at different mass ratios at different RHs before and after aging. For all particles, the measured GFs showed no indication of deliquescence across the range of RHs tested, and overall hygroscopicity was clearly lower after than before aging. The Ca(NO3)2 and Mg(NO3)2 GFs at 90 % RH were 1.80 and 1.66, respectively, before aging and 1.33 and 1.42, respectively, after 4 h aging, meaning aging decreased the GFs by 26.11 % and 14.46 %, respectively. Aging decreased the hygroscopicity because insoluble or sparingly soluble substances (CaSO3, CaSO4, MgSO3) formed and strongly changed the overall hygroscopicity. For bicomponent aerosols with different mass ratios, the GFs (calculated using the Zdanovskii-Stokes-Robinson method) of the other components except galactose at 90 % RH after 1 h aging were all lower, respectively, than the measured GFs of pure Ca(NO3)2 and Mg(NO3)2 after aging for 1 h, especially with the mass ratio of 1:2, their GFs have decreased by 14.63 % and 7.50 %, respectively. Subsequently, Ion chromatograms indicated that the peak area ratio of SO42− to NO3− ratios were higher for the aged bicomponent particles than aged single-component particles, possibly because adding galactose improved the gas–liquid state stability during drying after the aging process and therefore promoted nitrate consumption and sulfate formation. The results indicated that organic components may play important roles in heterogeneous reactions between trace gases and multicomponent aerosols and should be considered in evaluating the impacts on submicron aerosol composition of high atmospheric SO2 concentrations at high humidities.

Evaluation of reaction between SO2 and CH2OO in MCM mechanism against smog chamber data from ethylene ozonolysis

Environmental context The process of ethylene ozonolysis is an essential source of CH2OO radicals, and the latter is an important oxidant for the atmospheric pollutant SO2. The accuracy of a widely used atmospheric chemistry model (Master Chemical Mechanism, MCM) in quantifying SO2 oxidation has not been evaluated. In this study, this accuracy was evaluated, and optimal parameters underpinned by data from smog chamber experiments. Rationale The oxidation of SO2 by CH2OO radicals in the ethylene-O3 system is one of the important pathways of sulfate aerosol formation, but the accuracy of Master Chemical Mechanism (MCM) simulation for this reaction was not evaluated, although the MCM has been widely used in previous studies. Methodology The oxidation of SO2 in the ethylene-O3 system was performed in detail under different conditions, which were used to evaluate the accuracy of MCM simulation for the reactions in this study. Results The experimental conditions of low RH and high initial SO2 concentration favour the SO2 oxidation in the ethylene ozonolysis, and the yield of CH2OO in the ethylene ozonolysis without irradiations was determined to be 0.43. The n-hexane (C6H14) oxidation intermediates can promote the SO2 oxidation rate by generating sulfur-containing organics in the aerosol water. The original MCM simulated SO2 consumption after 4-h reaction was more than 70% smaller than the measured results. By adjusting the yield of CH2OO and updating the reaction rate constants of CH2OO-related reactions (e.g. with SO2, H2O and organic acid), the difference between experiments and simulations decreased from 70% to 6.6%. Discussion The promotion effects of n-hexane on the oxidation of SO2 suggest that alkanes may be the precursors of sulfur-containing organics in the atmospheric environment. This study further confirms the effect of CH2OO on the oxidation of SO2 in the atmospheric environment and provides information on the performance of MCM simulation.