Gaseous H2SO4 Research Articles

Importance of microphysical settings for climate forcing by stratospheric SO2 injections as modeled by SOCOL-AERv2

Abstract. Solar radiation modification by a sustained deliberate source of SO2 into the stratosphere (strat-SRM) has been proposed as an option for climate intervention. Global interactive aerosol–chemistry–climate models are often used to investigate the potential cooling efficiencies and associated side effects of hypothesized strat-SRM scenarios. A recent model intercomparison study for composition–climate models with interactive stratospheric aerosol suggests that the modeled climate response to a particular assumed injection strategy depends on the type of aerosol microphysical scheme used (e.g., modal or sectional representation) alongside host model resolution and transport. Compared to short-duration volcanic SO2 emissions, the continuous SO2 injections in strat-SRM scenarios may pose a greater challenge to the numerical implementation of microphysical processes such as nucleation, condensation, and coagulation. This study explores how changing the time steps and sequencing of microphysical processes in the sectional aerosol–chemistry–climate model SOCOL-AERv2 (40 mass bins) affects model-predicted climate and ozone layer impacts considering strat-SRM by SO2 injections of 5 and 25 Tg(S) yr−1 at 20 km altitude between 30° S and 30° N. The model experiments consider the year 2040 to be the boundary conditions for ozone-depleting substances and greenhouse gases (GHGs). We focus on the length of the microphysical time step and the call sequence of nucleation and condensation, the two competing sink processes for gaseous H2SO4. Under stratospheric background conditions, we find no effect of the microphysical setup on the simulated aerosol properties. However, at the high sulfur loadings reached in the scenarios injecting 25 Tg(S) yr−1 of SO2 with a default microphysical time step of 6 min, changing the call sequence from the default “condensation first” to “nucleation first” leads to a massive increase in the number densities of particles in the nucleation mode (R<0.01 µm) and a small decrease in coarse-mode particles (R>1 µm). As expected, the influence of the call sequence becomes negligible when the microphysical time step is reduced to a few seconds, with the model solutions converging to a size distribution with a pronounced nucleation mode. While the main features and spatial patterns of climate forcing by SO2 injections are not strongly affected by the microphysical configuration, the absolute numbers vary considerably. For the extreme injection with 25 Tg(S) yr−1, the simulated net global radiative forcing ranges from −2.3 to −5.3 W m−2, depending on the microphysical configuration. Nucleation first shifts the size distribution towards radii better suited for solar scattering (0.3 µm <R< 0.4 µm), enhancing the intervention efficiency. The size distribution shift, however, generates more ultrafine aerosol particles, increasing the surface area density and resulting in 10 DU (Dobson units) less ozone (about 3 % of the total column) in the northern mid-latitudes and 20 DU less ozone (6 %) over the polar caps compared to the condensation first approach. Our results suggest that a reasonably short microphysical time step of 2 min or less must be applied to accurately capture the magnitude of the H2SO4 supersaturation resulting from SO2 injection scenarios or volcanic eruptions. Taken together, these results underscore how structural aspects of model representation of aerosol microphysical processes become important under conditions of elevated stratospheric sulfur in determining atmospheric chemistry and climate impacts.

Titanium Dioxide Promotes New Particle Formation: A Smog Chamber Study.

TiO2 is a widely used material in building coatings. Many studies have revealed that TiO2 promotes the heterogeneous oxidation of SO2 and the subsequent sulfate formation. However, whether and how much TiO2 contributes to the gaseous H2SO4 and subsequent new particle formation (NPF) still remains unclear. Herein, we used a 1 m3 quartz smog chamber to investigate NPF in the presence of TiO2. The experimental results indicated that TiO2 could greatly promote NPF. The increases in particle formation rate (J) and growth rate due to the presence of TiO2 were quantified, and the promotion effect was attributed to the production of gaseous H2SO4. The promotion effect of TiO2 on SO2 oxidation and subsequent NPF decreased gradually due to the formation of surface sulfate but did not disappear completely, instead partly recovering after washing with water. Moreover, the promotion effect of TiO2 on NPF was observed regardless of differences in RH, and the most significant promotion effect of TiO2 associated with the strongest NPF occurred at an RH of 20%. Based on the experimental evidence, the environmental impact of TiO2 on gaseous H2SO4 and particle pollution in urban areas was estimated.

Influence of Aerosol Chemical Composition on Condensation Sink Efficiency and New Particle Formation in Beijing.

Relatively high concentrations of preexisting particles, acting as a condensation sink (CS) of gaseous precursors, have been thought to suppress the occurrence of new particle formation (NPF) in urban environments, yet NPF still occurs frequently. Here, we aim to understand the factors promoting and inhibiting NPF events in urban Beijing by combining one-year-long measurements of particle number size distributions and PM2.5 chemical composition. Our results show that indeed the CS is an important factor controlling the occurrence of NPF events, with its chemical composition affecting the efficiency of the background particles in removing gaseous H2SO4 (effectiveness of the CS) driving NPF. During our observation period, the CS was found to be more effective for ammonium nitrate-rich (NH4NO3-rich) fine particles. On non-NPF event days, particles acting as CS contained a larger fraction of NH4NO3 compared to NPF event days under comparable CS levels. In particular, in the CS range from 0.02 to 0.03 s–1, the nitrate fraction was 17% on NPF event days and 26% on non-NPF event days. Overall, our results highlight the importance of considering the chemical composition of preexisting particles when estimating the CS and their role in inhibiting NPF events, especially in urban environments.

Mechanism of SO3/H2SO4 transformation and reduction in wet flue gas desulfurization systems

In this study, a unique sampling unit combining quartz wool filtration and salt adsorption, which can measure aerosol and gaseous H2SO4 simultaneously, was adopted to reveal the transformation and reduction of SO3/H2SO4 in a lab-scale wet flue gas desulfurization (WFGD) scrubber. The results showed that H2SO4 in flue gas at the inlet of the WFGD scrubber is in both gaseous and aerosol states, and the gaseous state constitutes a larger proportion, differing from the conventional realization that all H2SO4 at WFGD scrubber inlets is gaseous. The experiments showed that the amount of H2SO4 aerosols increased, and that of H2SO4 vapor decreased in the scrubber, indicating H2SO4 transformation from a gaseous to an aerosol state after quenching. However, there is always a small portion of H2SO4 vapor that could be detected at the outlet, suggesting that H2SO4 cannot be completely converted to aerosols in the scrubber, differing from traditional assumption. We also found that spraying droplets could reduce H2SO4 but with low efficiency. The demister installed at the scrubber outlet is more efficient at reducing H2SO4 than the droplets, which inspires a new understanding of the mechanism of H2SO4 reduction in WFGD processes.

Toward Building a Physical Proxy for Gas-Phase Sulfuric Acid Concentration Based on Its Budget Analysis in Polluted Yangtze River Delta, East China.

Gaseous sulfuric acid (H2SO4) is a crucial precursor for secondary aerosol formation, particularly for new particle formation (NPF) that plays an essential role in the global number budget of aerosol particles and cloud condensation nuclei. Due to technology challenges, global-wide and long-term measurements of gaseous H2SO4 are currently very challenging. Empirical proxies for H2SO4 have been derived mainly based on short-term intensive campaigns. In this work, we performed comprehensive measurements of H2SO4 and related parameters in the polluted Yangtze River Delta in East China during four seasons and developed a physical proxy based on the budget analysis of gaseous H2SO4. Besides the photo-oxidation of SO2, we found that primary emissions can contribute considerably, particularly at night. Dry deposition has the potential to be a non-negligible sink, in addition to condensation onto particle surfaces. Compared with the empirical proxies, the newly developed physical proxy demonstrates extraordinary stability in all the seasons and has the potential to be widely used to improve the understanding of global NPF fundamentally.

Formation Environments of Metasomatites and Ores of the Epithermal Gold–silver Deposits

Preore metasomatites of epithermal gold–silver deposits are formed by various types of hydrothermal solutions—from highly acidic and oxidized (argillization, alunitization, secondary quartzites) and moderately acid (sericitization) to rather reduced and alkaline (adularia). The possible processes creating highly acid mineralizing fluids at shallow depths are: (a) the condensation of the acid gas phase of heterogenized fluids (including also the condensation of gaseous HCl, HF and H2SO4 whose water solutions possess properties of maximum boiling azeotropic mixtures); (b) the oxidation of containing SO2 and H2S magmatogene gases by meteoric waters rich in oxygen; and also c) possible disproportionation of sulfur from SO2 to H2S and H2SO4. The epithermal gold–silver deposits of high sulfidation type form at the upper parts of heterophase fluid systems. The major gold–silver and sulfide mineralization (except small amounts of earlier generations of pyrite, enargite, and luzonite) precipitates not synchronously with the acid metasomatites, but essentially later, when the water table of liquid and less acid fluids raise into the realm of ore deposition. At zones of flat subducting ocean crust, the deposits of copper–porphyry type are quite often found beneath the epithermal Au–Ag deposits. However, the former cannot be considered the bottom of the gold–silver ore-forming systems, because they sometimes form much earlier and in closed systems; therefore, they have their own bottom part of the ore-forming system (a zone of K-feldspathization with related molybdenum ore) and the top part (a zone of sericitization with related copper mineralization). In addition, in steep subduction zones typical of the Central West Pacific region, including Khabarovsk and Primorsky krais and Japan, epithermal Au–Ag deposits have no spatial or temporal relations to copper–porphyry deposits due to the nearly complete absence of the latter. There are the alkaline metasomatites that form in the lower, bottom parts of epithermal heterophase fluid systems, creating the major bonanza gold–silver and sulfide mineralization of the adularia (low sulfidation) type in the Russian Far East, western America, and Japan. The term high sulfidation widely used now was created by the artificial combination of the terms high sulfate and high oxidation and is very ambiguous, because it really does not imply sulfidization processes. This type of mineralization would be better named acid sulfate.

Evaluation of the controlled condensation method for flue gas SO3/H2SO4 measurement

Controlled condensation method (CCM) is widely accepted for detecting sulfur trioxide (SO3)/sulfuric acid (H2SO4) in flue gas. However, this method cannot be calibrated accurately because of the absence of the standard gas that contains H2SO4 vapor. We attempted to calibrate CCM by adopting another SO3/H2SO4 detection method that has been proven accurate. The following conclusions have been derived. The performance of the core component of CCM (i.e., the condenser) is acceptable. However, H2SO4 still escaped from the condenser, thereby confirming its negative errors. The filter set behind the condenser can prevent most of, but not all of, the escaping H2SO4 by intercepting aerosol H2SO4. Any flue gas cooling processes that occur in the sampling probe and the connecting pipe under 260 °C before the condenser can possibly cause negative errors because of acid condensation. The ash layer that formed during the ash filtration process cannot only intercept the aerosol H2SO4 but can also absorb the gaseous H2SO4, thereby resulting in negative errors. Errors caused by the accessories (i.e., the sampling probe, the connecting pipe, and the ash filtration) may be greater than those caused by the condenser, which may make the measurement invalid.

Responses of gaseous sulfuric acid and particulate sulfate to reduced SO2 concentration: A perspective from long-term measurements in Beijing

SO2 concentration decreased rapidly in recent years in China due to the implementation of strict control policies by the government. Particulate sulfate (pSO42−) and gaseous H2SO4 (SA) are two major products of SO2 and they play important roles in the haze formation and new particle formation (NPF), respectively. We examined the change in pSO42− and SA concentrations in response to reduced SO2 concentration using long-term measurement data in Beijing. Simulations from the Community Multiscale Air Quality model with a 2-D Volatility Basis Set (CMAQ/2D-VBS) were used for comparison. From 2013 to 2018, SO2 concentration in Beijing decreased by ~81% (from 9.1 ppb to 1.7 ppb). pSO42− concentration in submicrometer particles decreased by ~60% from 2012–2013 (monthly average of ~10 μg·m−3) to 2018–2019 (monthly average of ~4 μg·m−3). Accordingly, the fraction of pSO42− in these particles decreased from 20–30% to <10%. Increased sulfur oxidation ratio was observed both in the measurements and the CMAQ/2D-VBS simulations. Despite the reduction in SO2 concentration, there was no obvious decrease in SA concentration based on data from several measuring periods from 2008 to 2019. This was supported by the increased SA:SO2 ratio with reduced SO2 concentration and condensation sink. NPF frequency in Beijing between 2004 and 2019 remains relatively constant. This constant NPF frequency is consistent with the relatively stable SA concentration in Beijing, while different from some other cities where NPF frequency was reported to decrease with decreased SO2 concentrations.

Experimental method for observing the fate of SO3/H2SO4 in a temperature-decreasing flue gas flow: Creation of state diagram

The condensation behavior of sulfur trioxide/sulfuric acid (SO3/H2SO4) in flue gas is closely related to corrosion, aerosol formation, and blue plume discharge. Thus, it has become a hot issue in energy and environmental fields. However, no accurate method is currently available to observe this condensation behavior. In this work, an experimental method was developed to explore the fate of SO3/H2SO4 in a temperature-decreasing flue gas flow among the range of 260 °C–40 °C. A novel sampling unit with quartz wool and sodium chloride (NaCl) layer in series was adopted to accomplish the task of collecting aerosol and gaseous H2SO4, respectively, from flue gas. Bench scale experiments were performed to verify the reliability of the method. A state diagram was created according to the experimental results to reveal the fate evolution of H2SO4 as the flue gas temperature dropped. On the basis of the state diagram, the existing empirical models for predicting acid dew point (ADP) were evaluated. The predicted ADP values were found to deviate from the definition, falling within the temperature range in which H2SO4 condensed rapidly instead of the point in which H2SO4 was beginning to condense. The state diagram derived in this work can reveal slight acid condensation behavior better than other methods could.

The millimeter-wavelength absorption of sulfuric acid vapor measured under simulated Venus conditions

Laboratory measurements of the 2–4 millimeter-wavelength rotational absorption spectrum of H2SO4 vapor pressure-broadened by CO2 have been made under simulated Venus conditions using a semi-confocal microwave open resonator. Results of the measurements are used to derive an absorption model based on the JPL Millimeter Spectral Line Catalog using a Van Vleck-Weisskopf lineshape. The millimeter-wavelength H2SO4 vapor absorption predicted by this derived model contrasts with extrapolation of the absorption model of Kolodner and Steffes (1998), which is based on the results of centimeter-wavelength measurements made under similar conditions. The results of the measurements presented here and other laboratory measurements under Venus conditions have been used to develop a Venus microwave radiative transfer model. This model can be used to predict the wavelength-dependent brightness temperature observed by remote sensing platforms and Earth-based radio telescopes. Based on the results of the new model for H2SO4 vapor absorption, previously measured brightness temperature variations >10 K in the 3 millimeter wavelength range are unlikely directly due to variations in the abundance of gaseous H2SO4.

Development of a new corona discharge based ion source for high resolution time-of-flight chemical ionization mass spectrometer to measure gaseous H2SO4 and aerosol sulfate

A new corona discharge (CD) based ion source was developed for a commercial high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS) (Aerodyne Research Inc.) to measure both gaseous sulfuric acid (H2SO4) and aerosol sulfate after thermal desorption. Nitrate core ions (NO3−) were used as reagent ions and were generated by a negative discharge in zero air followed by addition of excess nitrogen dioxide (NO2) to convert primary ions and hydroxyl radicals (OH) into NO3− ions and nitric acid (HNO3). The CD-HRToF-CIMS showed no detectable interference from hundreds parts per billion by volume (ppbv) of sulfur dioxide (SO2). Unlike the atmospheric pressure ionization (API) ToF-CIMS, the CD ion source was integrated onto the ion–molecule reaction (IMR) chamber and which made it possible to measure aerosol sulfate by coupling to a filter inlet for gases and aerosols (FIGAERO). Moreover, compared with a quadrupole-based mass spectrometer, the desired HSO4− signal was detected by its exact mass of m/z 96.960, which was well resolved from the potential interferences of HCO3−⋅(H2O)2 (m/z 97.014) and O−⋅H2O⋅HNO3 (m/z 97.002). In this work, using laboratory-generated standards the CD-HRToF-CIMS was demonstrated to be able to detect as low as 3.1 × 105 molecules cm−3 gaseous H2SO4 and 0.5 μg m−3 ammonium sulfate based on 10-s integration time and two times of the baseline noise. The CD ion source had the advantages of low cost and a simple but robust structure. Since the system was non-radioactive and did not require corrosive HNO3 gas, it can be readily field deployed. The CD-HRToF-CIMS can be a powerful tool for both field and laboratory studies of aerosol formation mechanism and the chemical processes that were critical to understand the evolution of aerosols in the atmosphere.

Effect of a gas–gas-heater on H2SO4 aerosol formation: Implications for mist formation in amine based carbon capture

This study is to our knowledge the first to describe the effect of a Gas–Gas Heater (GGH) of a coal fired power plant’s has on (i) the H2SO4 concentration and (ii) the particle/aerosol number concentration and particle size distribution present in the flue gas. In the absence of a GGH, homogenous nucleation takes places inside the Wet Flue Gas Desulphurisation (WFGD) converting the gaseous H2SO4 into aerosol H2SO4. This leads to a high aerosol number concentration behind the WFGD with 80% of the aerosols being smaller than 0.02μm. This implies that an amine based carbon capture (CC) installation treating this flue gas can suffer from amine mist formation due to the high amount of available nuclei (i.e., H2SO4 aerosols) resulting in high amine emissions. In contrast, in the presence of a GGH not only 70% of the H2SO4 is removed from the flue gas (measured at the Nijmegen powerplant), but also homogenous nucleation in the WFGD is prevented resulting in low particle number concentrations. The flue gas leaving the GGH will not create any mist formation issues in an amine based CC installation due to the low amount of nuclei present in the flue gas. It is not the reduction in H2SO4 concentration by 70% inside the GGH as such that prevents mist formation but absence of H2SO4 in its aerosol form. These results are most likely quite widely transformable to other power plants that burn low sulfur coal i.e., around 0.7 weight%. This information will serve future pilot and demo CC installation around the world; in particular when retrofitted on power plants that have a GGH.

Experimental Evaluation and Field Application of a Salt Method for SO3 Measurement in Flue Gases

In this study, an SO3 measurement technique was evaluated and developed. In the method, a salt is used to capture gaseous SO3/H2SO4. Various salts were tested to evaluate the suitability to measure SO3/H2SO4 without interference from SO2. Salts tested include NaCl, KCl, K2CO3, and CaCl2. The salts were tightly packed into a Teflon tube, and the gas was fed through the salt tube with subsequent reaction between SO3/H2SO4 and the salt with formation of sulfates of the respective salt. After the measurement, the salt was dissolved in water, and the solution was analyzed for sulfate ions. The SO3/H2SO4 concentration in the flue gas could then be determined because the gas volume flowing through the salt was measured together with the amount of sulfate bound in the salt. The method was tested in laboratory conditions, in a 100 kWth test unit during air-firing and oxy-fuel combustion, and in an industrial boiler. A first attempt to continuously measure SO3/H2SO4 indirectly with an FTIR, by measuring the release of HCl in the sulfation of KCl, was also made. The conversion of SO3 to H2SO4 in flue gas conditions is discussed. It was found that at the measurement conditions almost all SO3 is present as H2SO4. Therefore, the laboratory study was made with gaseous H2SO4 instead of SO3. The laboratory tests showed that all salts captured all H2SO4. The best selectivity toward H2SO4 was shown for NaCl and KCl; no significant amount of SO2 was captured in these salts. An in situ implementation of the salt method using KCl as salt was used during heavy oil combustion in a Kraft recovery boiler. The salt method showed to be an accurate, inexpensive, and easy way to measure SO3/H2SO4 in flue gases.

Gas phase formation of extremely oxidized pinene reaction products in chamber and ambient air

Abstract. High molecular weight (300–650 Da) naturally charged negative ions have previously been observed at a boreal forest site in Hyytiälä, Finland. The long-term measurements conducted in this work showed that these ions are observed practically every night between spring and autumn in Hyytiälä. The ambient mass spectral patterns could be reproduced in striking detail during additional measurements of α-pinene (C10H16) oxidation at low-OH conditions in the Jülich Plant Atmosphere Chamber (JPAC). The ions were identified as clusters of the nitrate ion (NO3−) and α-pinene oxidation products reaching oxygen to carbon ratios of 0.7–1.3, while retaining most of the initial ten carbon atoms. Attributing the ions to clusters instead of single molecules was based on additional observations of the same extremely oxidized organics in clusters with HSO4− (Hyytiälä) and C3F5O2− (JPAC). The most abundant products in the ion spectra were identified as C10H14O7, C10H14O9, C10H16O9, and C10H14O11. The mechanism responsible for forming these molecules is still not clear, but the initial reaction is most likely ozone attack at the double bond, as the ions are mainly observed under dark conditions. β-pinene also formed highly oxidized products under the same conditions, but less efficiently, and mainly C9 compounds which were not observed in Hyytiälä, where β-pinene on average is 4–5 times less abundant than α-pinene. Further, to explain the high O/C together with the relatively high H/C, we propose that geminal diols and/or hydroperoxide groups may be important. We estimate that the night-time concentration of the sum of the neutral extremely oxidized products is on the order of 0.1–1 ppt (~106–107 molec cm−3). This is in a similar range as the amount of gaseous H2SO4 in Hyytiälä during day-time. As these highly oxidized organics are roughly 3 times heavier, likely with extremely low vapor pressures, their role in the initial steps of new aerosol particle formation and growth may be important and needs to be explored in more detail in the future.

Measurements of gaseous H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; by AP-ID-CIMS during CAREBeijing 2008 Campaign

Abstract. As part of the 2008 Campaign of Air Quality Research in Beijing and Surrounding Regions (CAREBeijing 2008), measurements of gaseous sulfuric acid (H2SO4) have been conducted at an urban site in Beijing, China from 7 July to 25 September 2008 using atmospheric pressure ion drift – chemical ionization mass spectrometry (AP-ID-CIMS). This represents the first gaseous H2SO4 measurements in China. Diurnal profile of sulfuric acid is strongly dependent on the actinic flux, reaching a daily maximum around noontime and with an hourly average concentration of 5 × 106 molecules cm−3. Simulation of sulfuric acid on the basis of the measured sulfur dioxide concentration, photolysis rates of ozone and nitrogen dioxide, and aerosol surface areas captures the trend of the measured H2SO4 diurnal variation within the uncertainties, indicating that photochemical production and condensation onto preexisting particle surface dominate the observed diurnal H2SO4 profile. The frequency of the peak H2SO4 concentration exceeding 5 × 106 molecules cm−3 increases by 16 % during the period of the summer Olympic Games (8–24 August 2008), because of the implementation of air quality control regulations. Using a multivariate statistical method, the critical nucleus during nucleation events is inferred, containing two H2SO4 molecules (R2 = 0.85). The calculated condensation rate of H2SO4 can only account for 10–25 % of PM1 sulfate formation, indicating that either much stronger sulfate production exists at the SO2 source region or other sulfate production mechanisms are responsible for the sulfate production.

Nighttime chemical evolution of aerosol and trace gases in a power plant plume: Implications for secondary organic nitrate and organosulfate aerosol formation, NO3 radical chemistry, and N2O5 heterogeneous hydrolysis

Nighttime chemical evolution of aerosol and trace gases in a coal‐fired power plant plume was monitored with the Department of Energy Grumman Gulfstream‐1 aircraft during the 2002 New England Air Quality Study field campaign. Quasi‐Lagrangian sampling in the plume at increasing downwind distances and processing times was guided by a constant‐volume balloon that was released near the power plant at sunset. While no evidence of fly ash particles was found, concentrations of particulate organics, sulfate, and nitrate were higher in the plume than in the background air. The enhanced sulfate concentrations were attributed to direct emissions of gaseous H2SO4, some of which had formed new particles as evidenced by enhanced concentrations of nucleation‐mode particles in the plume. The aerosol species were internally mixed and the particles were acidic, suggesting that particulate nitrate was in the form of organic nitrate. The enhanced particulate organic and nitrate masses in the plume were inferred as secondary organic aerosol, which was possibly formed from NO3 radical‐initiated oxidation of isoprene and other trace organic gases in the presence of acidic sulfate particles. Microspectroscopic analysis of particle samples suggested that some sulfate was in the form of organosulfates. Microspectroscopy also revealed the presence of sp2 hybridized C = C bonds, which decreased with increasing processing time in the plume, possibly because of heterogeneous chemistry on particulate organics. Constrained plume modeling analysis of the aircraft and tetroon observations showed that heterogeneous hydrolysis of N2O5 was negligibly slow. These results have significant implications for several issues related to the impacts of power plant emissions on air quality and climate.

One conceivable mechanism of UV-light induced SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Oxidation to H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;

Abstract. The electron-excited chemistry of sulfur dioxide oxidation induced by UV irradiation of air with trace O3 and SO2 is considered. The importance of this mechanism is evaluated based on recent laboratory experiments on SO2 oxidation in a laminar tube with air induced by UV irradiation. Results show that under respective conditions the route of SO2 oxidation involving electron excited oxygen molecules may present an additional source of gaseous H2SO4 production to known OH-radical mechanism.

Effect of aerosol precursors from gas turbine engines on the volatile sulfate aerosols and ion clusters formation in aircraft plumes

A comprehensive analysis of the influence of sulfate aerosol precursor gases and chemi-ions generation in the internal flow of a jet engine (gas turbine engine) on sulfate volatile aerosols and ion cluster formation in an aircraft plume is presented. The evolution of the aerosol size distribution and the chemical composition change is simulated using a previously developed quasi one-dimensional flow field model with coupled gas phase kinetics, aerosol nucleation, condensation, and coagulation processes. An increased abundance of the aerosol precursors SO3, HSO3, and H2SO4 at the nozzle exit leads to an increased number of larger volatile aerosol particles, with diameter > 5 and 9 nm, than previously measured in aircraft exhaust plumes. Most of the gaseous H2SO4 gets converted to liquid aerosol particles within about 1 s. The generation of HSO4−, NO3−, NO+, and H3O+ ions in the combustor results in the formation of charged clusters, mostly HSO4−(H2SO4)m, NO3−(HNO3)(H2O), HSO4−(HNO3)n, H3O+(H2O)m, H3O+(CH2O)(H2O)n in the near field plume (first few hundred meters). For typical cruise conditions of a B-747 aircraft the calculated values of ion cluster concentration at the distance from nozzle exit L<40 m are around 3 × 105–3 × 106 cm−3 for fuel sulfur content (FSC≥0.04%) and only 7 × 104 cm−3 for free sulfur fuel (FSC=0%).

Gaseous SO3 and H2SO4 in the exhaust of an aircraft gas turbine engine: measurements by CIMS and implications for fuel sulfur conversion to sulfur (VI) and conversion of SO3 to H2SO4

Abstract An estimation of the conversion efficiency ( e ) of fuel sulfur to SO 3 and H 2 SO 4 , where e =([SO 3 ]+[H 2 SO 4 ])/[S T ] and [S T ] is the total sulfur atom concentration in the exhaust at the exit of an aircraft gas-turbine combustor, was derived from measurements by comparison with model results. The major results of the presented CIMS experiments and their interpretation with a model simulation are: (i) The efficiency is e =2.3±1% at an exhaust age of about 5 ms from the combustor exit; (ii) The SO 3 molecules represent a major fraction of sulfur (VI) gases e A 3 -conversion to H 2 SO 4 takes place in the sampling line where the exhaust gases spend a sufficiently long time and where the temperature is lower than in the hot exhaust. The coincidence of e from our work (measurements with the sampling point in the exhaust just behind the combustor exit) and e the measurements in an exhaust at a plume age of about 1 s suggests that the sulfur (VI) formation is inefficient in the post-combustor flow inside the aircraft engine.

Gaseous (DMS, MSA, SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; and DMSO) and particulate (sulfate and methanesulfonate) sulfur species over the northeastern coast of Crete

Abstract. A detailed study of the levels, the temporal and diurnal variability of the main compounds involved in the biogenic sulfur cycle was carried out in Crete (Eastern Mediterranean) during the Mediterranean Intensive Oxidant Study (MINOS) field experiment in July-August 2001. Intensive measurements of gaseous dimethylsulfide (DMS), dimethylsulfoxide (DMSO), sulfur dioxide (SO2), sulfuric (H2SO4) and methanesulfonic acids (MSA) and particulate sulfate (SO42-) and methanesulfonate (MS-) have been performed during the campaign. Dimethylsulfide (DMS) levels ranged from 2.9 to 136 pmol·mol-1 (mean value of 21.7 pmol·mol-1) and showed a clear diurnal variation with daytime maximum. During nighttime DMS levels fall close or below the detection limit of 2 pmol·mol-1. Concurrent measurements of OH and NO3 radicals during the campaign indicate that NO3 levels can explain most of the observed diurnal variation of DMS. Dimethylsulfoxide (DMSO) ranged between 0.02 and 10.1 pmol·mol-1 (mean value of 1.7 pmol·mol-1) and presents a diurnal variation similar to that of DMS. SO2 levels ranged from 220 to 2970 pmol·mol-1 (mean value of 1030 pmol·mol-1), while nss-SO42- and MS- ranged from 330 to 7100 pmol·mol-1, (mean value of 1440 pmol·mol-1) and 1.1 to 37.5 pmol·mol-1 (mean value of 11.5 pmol·mol-1) respectively. Of particular interest are the measurements of gaseous MSA and H2SO4. MSA ranged from below the detection limit (3x104) to 3.7x107 molecules cm-3, whereas H2SO4 ranged between 1x105 and 9.0x107 molecules cm-3. The measured H2SO4 maxima are among the highest reported in literature and can be attributed to high insolation, absence of precipitation and increased SO2 levels in the area. From the concurrent SO2, OH, and H2SO4 measurements a sticking coefficient of 0.52±0.28 was calculated for H2SO4. From the concurrent MSA, OH, and DMS measurements the yield of gaseous MSA from the OH-initiated oxidation of DMS was calculated to range between 0.1-0.4%. This low MSA yield implies that gaseous MSA levels can not account for the observed MS- levels. Heterogeneous reactions of DMSO on aerosols should be considered to explain the observed levels of MS-.