scholarly journals Heterogeneous reaction of SO2 with soot: The roles of relative humidity and surface composition of soot in surface sulfate formation

2017 ◽  
Vol 152 ◽  
pp. 465-476 ◽  
Author(s):  
Yan Zhao ◽  
Yongchun Liu ◽  
Jinzhu Ma ◽  
Qingxin Ma ◽  
Hong He
Keyword(s):  
Relative Humidity ◽  
Surface Composition ◽  
Heterogeneous Reaction ◽  
Sulfate Formation

scholarly journals Effects of NO<sub>2</sub> and C<sub>3</sub>H<sub>6</sub> on the heterogeneous oxidation of SO<sub>2</sub> on TiO<sub>2</sub> in the presence or absence of UV–Vis irradiation

2019 ◽  
Vol 19 (23) ◽  
pp. 14777-14790 ◽  
Author(s):  
Biwu Chu ◽  
Yali Wang ◽  
Weiwei Yang ◽  
Jinzhu Ma ◽  
Qingxin Ma ◽  
...  
Keyword(s):  
Active Sites ◽  
Heterogeneous Reaction ◽  
Reaction System ◽  
Heterogeneous Reactions ◽  
Heterogeneous Oxidation ◽  
Inorganic Species ◽  
Sulfate Formation ◽  
Dark Conditions ◽  
Diffuse Reflectance Infrared ◽  
Reaction Processes

Abstract. The heterogeneous reactions of SO2 in the presence of NO2 and C3H6 on TiO2 were investigated with the aid of in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) under dark conditions or with UV–Vis irradiation. Sulfate formation with or without the coexistence of NO2 and/or C3H6 was analyzed with ion chromatography (IC). Under dark conditions, SO2 reacting alone resulted in sulfite formation on TiO2, while the presence of parts per billion (ppb) levels of NO2 promoted the oxidation of SO2 to sulfate. The presence of C3H6 had little effect on sulfate formation in the heterogeneous reaction of SO2 but suppressed sulfate formation in the heterogeneous reaction of SO2 and NO2. UV–Vis irradiation could significantly enhance the heterogeneous oxidation of SO2 on TiO2, leading to copious generation of sulfate, while the coexistence of NO2 and/or C3H6 significantly suppressed sulfate formation in experiments with UV–Vis lights. Step-by-step exposure experiments indicated that C3H6 mainly competes for reactive oxygen species (ROS), while NO2 competes with SO2 for both surface active sites and ROS. Meanwhile, the coexistence of NO2 with C3H6 further resulted in less sulfate formation compared to introducing either one of them separately to the SO2–TiO2 reaction system. The results of this study highlighted the complex heterogeneous reaction processes that take place due to the ubiquitous interactions between organic and inorganic species and the need to consider the influence of coexisting volatile organic compounds (VOCs) and other inorganic gases in the heterogeneous oxidation kinetics of SO2.

scholarly journals Kinetics and mechanism of heterogeneous oxidation of sulfur dioxide by ozone on surface of calcium carbonate

2006 ◽  
Vol 6 (9) ◽  
pp. 2453-2464 ◽  
Author(s):  
L. Li ◽  
Z. M. Chen ◽  
Y. H. Zhang ◽  
T. Zhu ◽  
J. L. Li ◽  
...  
Keyword(s):  
Heterogeneous Reaction ◽  
Global Climate ◽  
Chemical Properties ◽  
Heterogeneous Oxidation ◽  
Reactive Component ◽  
Rate Determining Step ◽  
Important Pathway ◽  
Sulfate Formation ◽  
Heterogeneous Formation ◽  
Diffuse Reflectance Infrared

Abstract. Sulfate particles play a key role in the air quality and the global climate, but the heterogeneous formation mechanism of sulfates on surfaces of atmospheric particles is not well established. Carbonates, which act as a reactive component in mineral dust due to their special chemical properties, may contribute significantly to the sulfate formation by heterogeneous processes. This paper presents a study on the oxidation of SO2 by O3 on CaCO3 particles. Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), the formation of sulfite and sulfate on the surface was identified, and the roles of O3 and water in oxidation processes were determined. The results showed that in the presence of O3, SO2can be oxidized to sulfate on the surface of CaCO3 particles. The reaction is first order in SO2 and zero order in O3. The reactive uptake coefficient for SO2 [(0.6–9.8)×1014 molecule cm-3] oxidation by O3 [(1.2–12)×1014 molecule cm-3] was determined to be (1.4±0.3)×10-7 using the BET area as the reactive area and (7.7±1.6)×10-4 using the geometric area. A two-stage mechanism that involves adsorption of SO2 followed by O3 oxidation is proposed and the adsorption of SO2 on the CaCO3 surface is the rate-determining step. The proposed mechanism can well explain the experiment results. The atmospheric implications were explored based on a box model calculation. It was found that the heterogeneous reaction might be an important pathway for sulfate formation in the atmosphere.

scholarly journals Kinetics and mechanism of heterogeneous oxidation of sulfur dioxide by ozone on surface of calcium carbonate

2006 ◽  
Vol 6 (1) ◽  
pp. 579-613 ◽  
Author(s):  
L. Li ◽  
Z. M. Chen ◽  
Y. H. Zhang ◽  
T. Zhu ◽  
J. L. Li ◽  
...  
Keyword(s):  
Heterogeneous Reaction ◽  
Global Climate ◽  
Chemical Properties ◽  
So2 Oxidation ◽  
Heterogeneous Oxidation ◽  
Reactive Component ◽  
Rate Determining Step ◽  
Sulfate Formation ◽  
Heterogeneous Formation ◽  
Diffuse Reflectance Infrared

Abstract. Sulfate particles play a key role in the air quality and the global climate, but the heterogeneous formation mechanism of sulfates on surfaces of atmospheric particles is not well established. Carbonates, which act as a reactive component in mineral dust due to their special chemical properties, may contribute significantly to the sulfate formation by heterogeneous processes. This paper presents a study on the oxidation of SO2 by O3 on CaCO3 particles. Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), the formation of sulfite and sulfate on the surface was identified, and the roles of O3 and water in oxidation processes were determined. The results showed that in the presence of O3, SO2 can be oxidized to sulfate on the surface of CaCO3 particles. The reaction is first order in SO2 and zero order in O3. The reactive uptake coefficient for SO2 oxidation by O3 was determined to be (1.4±0.3)×10−7 using the BET area as the reactive area and (7.7±1.6)×10−4 using the geometric area. A two-stage mechanism that involves adsorption of SO2 followed by O3 oxidation is proposed and the adsorption of SO2 on the CaCO3 surface is the rate-determining step. The proposed mechanism can well explain the experiment results. The atmospheric implications were explored based on a box model calculation. It was found that the heterogeneous reaction might be an important pathway for sulfate formation in the atmosphere.

scholarly journals Heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with illite and Arizona test dust particles

2014 ◽  
Vol 14 (1) ◽  
pp. 245-254 ◽  
Author(s):  
M. J. Tang ◽  
G. Schuster ◽  
J. N. Crowley
Keyword(s):  
Relative Humidity ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Heterogeneous Reaction ◽  
Thermal Dissociation ◽  
Dust Particles ◽  
Mineral Surfaces ◽  
Uptake Coefficient ◽  
Flow Tube ◽  
Aerosol Flow

Abstract. The heterogeneous reaction of N2O5 with airborne illite and Arizona test dust (ATD) particles was investigated at room temperature and at different relative humidities using an atmospheric pressure aerosol flow tube. N2O5 at concentrations in the range 8 to 24 × 1012 molecule cm−3 was monitored using thermal-dissociation cavity ring-down spectroscopy at 662 nm. At zero relative humidity a large uptake coefficient of N2O5 to illite was obtained, γ(N2O5) = 0.09, which decreased to 0.04 as relative humidity was increased to 67%. In contrast, the uptake coefficient derived for ATD is much lower (~0.006) and displays a weaker (if any) dependence on relative humidity (0–67%). Potential explanations are given for the significant differences between the uptake behaviour for ATD and illite and the results are compared with uptake coefficients for N2O5 on other mineral surfaces.

scholarly journals Simulations of Sulfate-Nitrate-Ammonium (SNA) aerosols during the extreme haze events over Northern China in October 2014

2016 ◽  
Author(s):  
Dan Chen ◽  
Zhiquan Liu ◽  
Jerome Fast ◽  
Junmei Ban
Keyword(s):  
Relative Humidity ◽  
Observational Data ◽  
Heterogeneous Reaction ◽  
Northern China ◽  
Reaction Rates ◽  
Heterogeneous Reactions ◽  
Formation Mechanisms ◽  
Emission Rates ◽  
Oxidation Rates ◽  
The North

Abstract. Extreme haze events have occurred frequently over China in recent years. Although many studies have investigated the formation mechanisms associated with PM2.5 for heavily polluted regions in China based on observational data, adequately predicting peak PM2.5 concentrations is still challenging for regional air quality models. In this study, we evaluate the performance of one configuration of the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and use the model to investigate the sensitivity of heterogeneous reactions on simulated peak sulfate, nitrate, and ammonium concentrations in the vicinity of Beijing during four extreme haze episodes in October 2014 over the North China Plain. The highest observed PM2.5 concentration of 469 μg m-3 occurred in Beijing. Comparisons with observations show that the model reproduced the temporal variability in PM2.5 with the highest PM2.5 values on polluted days (defined as days in which observed PM2.5 is greater than 75 μg m-3), but predictions of sulfate, nitrate, and ammonium were too low on days with the highest observed concentrations. Observational data indicate that the sulfur/nitric oxidation rates are strongly correlated with relative humidity during periods of peak PM2.5; however, the model failed to reproduce the highest PM2.5 concentrations due to missing heterogeneous reactions. As the parameterizations of those reactions is not well established yet, estimates of SO2-to-H2SO4 and NO2/NO3-to-HNO3 reaction rates that depend on relative humidity were applied which improved the simulation of sulfate, nitrate, and ammonium enhancement on polluted days in terms of both concentrations and partitioning among those species. Sensitivity simulations showed that the extremely high heterogeneous reaction rates and also higher emission rates than those reported in the emission inventory were likely important factors contributing to those peak PM2.5 simulations.

scholarly journals Relative humidity and O<sub>3</sub> concentration as two prerequisites for sulfate formation

2019 ◽  
Vol 19 (19) ◽  
pp. 12295-12307 ◽  
Author(s):  
Yanhua Fang ◽  
Chunxiang Ye ◽  
Junxia Wang ◽  
Yusheng Wu ◽  
Min Hu ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Relative Humidity ◽  
Water Content ◽  
Seasonal Variations ◽  
Formation Mechanisms ◽  
Particle Volume ◽  
Multiphase Reactions ◽  
Sampling Campaign ◽  
Sulfate Formation ◽  
Concentration Threshold

Abstract. Sulfate formation mechanisms have been discussed extensively but are still disputed. In this work, a year-long particulate matter (PM2.5) sampling campaign was conducted together with measurements of gaseous pollutant concentrations and meteorological parameters in Beijing, China, from March 2012 to February 2013. The sulfur oxidation ratio (SOR), an indicator of secondary sulfate formation, displayed a clear summer peak and winter valley, even though no obvious seasonal variations in sulfate mass concentration were observed. A rapid rise in the SOR was found at a relative humidity (RH) threshold of ∼45 % or an O3 concentration threshold of ∼35 ppb, allowing us to first introduce the idea that RH and O3 concentrations are two prerequisites for rapid sulfate formation via multiphase reactions. In the case of the RH threshold, this is consistent with current understanding of the multiphase formation of sulfate, since it relates to the semisolid-to-liquid phase transition of atmospheric aerosols. Correlation analysis between SOR and aerosol water content (AWC) further backed this up. In the case of the O3 concentration threshold, this is consistent with the consumption of liquid oxidants in multiphase sulfate formation. The thresholds introduced here lead us to a better understanding of the sulfate formation mechanisms and sulfate formation variations. H2O2 might be the major oxidant of sulfate formation, since another liquid-phase oxidant, O3, has previously been shown to be unimportant. The seasonal variations in sulfate formation could be accounted for by variations in the RH and O3 prerequisites. For example, over the year-long study, the fastest SO2-to-sulfate conversion occurred in summer, which was associated with the highest values of O3 (and also H2O2) concentration and RH. The SOR also displayed variations with pollution levels; i.e. the SOR increased with PM2.5 in all seasons. Such variations were primarily associated with a transition from the slow gas-phase formation of sulfate to rapid multiphase reactions, since RH increased higher than its prerequisite value of around 45 % as pollution evolved. In addition, the self-catalytic nature of sulfate formation (i.e. the formation of hydrophilic sulfate aerosols under high RH conditions results in an increase in aerosol water content, which results in greater particle volume for further multiphase sulfate formation) also contributed to variations among the pollution scenarios.

scholarly journals Effects of stabilized Criegee Intermediates (sCI) on the sulfate formation: A case study during summertime in Beijing-Tianjin-Hebei (BTH), China

2019 ◽  
Author(s):  
Lang Liu ◽  
Naifang Bei ◽  
Jiarui Wu ◽  
Suixin Liu ◽  
Jiamao Zhou ◽  
...  
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Heterogeneous Reaction ◽  
Reaction Rate Constant ◽  
So2 Emissions ◽  
So2 Oxidation ◽  
Formation Pathway ◽  
Criegee Intermediates ◽  
Sulfate Formation ◽  
Stabilized Criegee Intermediates

Abstract. Sulfate aerosols exert profound impacts on climate, ecosystem, visibility, and public health, but the sulfate formation pathway remains elusive. In the present study, a source-oriented WRF-Chem model is applied to simulate a persistent air pollution episode from 04 to 15 July 2015 in Beijing-Tianjin-Hebei (BTH), China to study contributions of four pathways to the sulfate formation. When comparing simulations to measurements in BTH, the index of agreement (IOA) of meteorological parameters, air pollutants and aerosol species generally exceeds 0.6. On average in BTH, the heterogeneous reaction of SO2 involving aerosol water and the SO2 oxidation by OH constitutes the two most important sulfate sources, with a contribution of about 35 %–38 % and 33 %–36 % respectively. The primary emission accounts for around 22 %–24 % of sulfate concentrations due to high SO2 emissions. The SO2 oxidation by stabilized Criegee Intermediates (sCI) also plays an appreciable role in the sulfate formation, with a contribution of around 9 % when an upper limit of the reaction rate constant of sCI with SO2 (κsCI + SO2 = 3.9 × 10−11 cm3 s−1) and a lower limit of the reaction rate constant of sCI with H2O (κsCI + H2O = 1.97 × 10−18 cm3 s−1) are used. Sensitivity studies reveal that there still exist large uncertainties in the sulfate contribution of the SO2 oxidation by sCI. The sulfate contribution of the reaction is decreased to less than 3 % when κsCI + SO2 is decreased to 6.0 × 10−13 cm3 s−1. Furthermore, when κsCI + H2O is increased to 2.38 × 10−15 cm3 s−1 based on the reported ratio of κsCI + SO2 to κsCI + H2O (6.1 × 10−5), the sulfate contribution becomes insignificant, less than 2%. Further studies need to be conducted to better determine κsCI + SO2 and κsCI + H2O to evaluate effects of the sCI chemistry on the sulfate formation.

scholarly journals Effects of NO<sub>2</sub> and C<sub>3</sub>H<sub>6</sub> on the heterogeneous oxidation of SO<sub>2</sub> on TiO<sub>2</sub> in the presence or absence of UV irradiation

2019 ◽  
Author(s):  
Biwu Chu ◽  
Yali Wang ◽  
Weiwei Yang ◽  
Jinzhu Ma ◽  
Qingxin Ma ◽  
...  
Keyword(s):  
Uv Irradiation ◽  
Active Sites ◽  
Heterogeneous Reaction ◽  
Reaction System ◽  
Heterogeneous Reactions ◽  
Heterogeneous Oxidation ◽  
Inorganic Species ◽  
Sulfate Formation ◽  
Dark Conditions ◽  
Reaction Processes

Abstract. The heterogeneous reactions of SO2 in the presence of NO2 and C3H6 on TiO2 were investigated with the aid of in situ DRIFTS under dark conditions or with UV irradiation. Sulfate formation with or without the coexistence of NO2 and/or C3H6 was analyzed with IC. Under dark conditions, SO2 reacting alone resulted in sulfite formation on TiO2, while the presence of ppb levels of NO2 promoted the oxidation of SO2 to sulfate. The presence of C3H6 had little effect on sulfate formation in the heterogeneous reaction of SO2 but suppressed sulfate formation in the heterogeneous reaction of SO2 and NO2. UV irradiation could significantly enhance the heterogeneous oxidation of SO2 on TiO2, leading to a copious generation of sulfate, while the coexistence of NO2 and/or C3H6 significantly suppressed sulfate formation in experiments with UV lights. Step-by-step exposure experiments indicated that C3H6 mainly competes for reactive oxygen species (ROS), while NO2 competes with SO2 for both surface active sites and ROS. Meanwhile, the coexistence of NO2 with C3H6 further resulted in less sulfate formation compared to introducing either one of them separately to the SO2-TiO2 reaction system. The results of this study highlighted the complex heterogeneous reaction processes that take place due to the ubiquitous interactions between organic and inorganic species, and the requirement to consider the influence of coexisting VOCs and other inorganic gases in the heterogeneous oxidation kinetics of SO2.

scholarly journals Heterogeneous Reaction of SO2 on Manganese Oxides: the Effect of Crystal Structure and Relative Humidity

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Weiwei Yang ◽  
Jianghao Zhang ◽  
Qingxin Ma ◽  
Yan Zhao ◽  
Yongchun Liu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Relative Humidity ◽  
Manganese Oxides ◽  
Heterogeneous Reaction
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