scholarly journals Year-round modeling of sulfate aerosol over Asia through updates of aqueous-phase oxidation and gas-phase reactions with stabilized Criegee intermediates

2021 ◽  
pp. 100123
Author(s):  
Syuichi Itahashi ◽  
Risa Uchida ◽  
Kazuyo Yamaji ◽  
Satoru Chatani
Keyword(s):  
Gas Phase ◽  
Aqueous Phase ◽  
Sulfate Aerosol ◽  
Gas Phase Reactions ◽  
Criegee Intermediates ◽  
Phase Oxidation ◽  
Stabilized Criegee Intermediates

scholarly journals The influences of ammonia on aerosol formation in the ozonolysis of styrene: roles of Criegee intermediate reactions

2018 ◽  
Vol 5 (5) ◽  
pp. 172171 ◽  
Author(s):  
Qiao Ma ◽  
Xiaoxiao Lin ◽  
Chengqiang Yang ◽  
Bo Long ◽  
Yanbo Gai ◽  
...  
Keyword(s):  
Gas Phase ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Gas Phase Reactions ◽  
Aerosol Composition ◽  
Theoretical Methods ◽  
Criegee Intermediates ◽  
Secondary Ozonide

The influences of ammonia (NH 3 ) on secondary organic aerosol (SOA) formation from ozonolysis of styrene have been investigated using chamber experiments and quantum chemical calculations. With the value of [O 3 ] 0 /[styrene] 0 ratios between 2 and 4, chamber experiments were carried out without NH 3 or under different [NH 3 ]/[styrene] 0 ratios. The chamber experiments reveal that the addition of NH 3 led to significant decrease of SOA yield. The overall SOA yield decreased with the [NH 3 ] 0 /[styrene] 0 increasing. In addition, the addition of NH 3 at the beginning of the reaction or several hours after the reaction occurs had obviously different influence on the yield of SOA. Gas phase reactions of Criegee intermediates (CIs) with aldehydes and NH 3 were studied in detail by theoretical methods to probe into the mechanisms behind these phenomena. The calculated results showed that 3,5-diphenyl-1,2,4-trioxolane, a secondary ozonide formed through the reactions of C 6 H 5 ĊHOO· with C 6 H 5 CHO, could make important contribution to the aerosol composition. The addition of excess NH 3 may compete with aldehydes, decreasing the secondary ozonide yield to some extent and thus affect the SOA formation.

scholarly journals CAPRAM reduction towards an operational multiphase halogen and DMS chemistry treatment in the chemistry transport model COSMO-MUSCAT(5.04e)

2020 ◽  
Author(s):  
Erik H. Hoffmann ◽  
Roland Schrödner ◽  
Andreas Tilgner ◽  
Ralf Wolke ◽  
Hartmut Herrmann
Keyword(s):  
Gas Phase ◽  
Aqueous Phase ◽  
Transport Model ◽  
Chemical Transport ◽  
Regional Models ◽  
Gas Phase Reactions ◽  
Oxidation Rates ◽  
Reduced Mechanism ◽  
Equilibrium Reactions ◽  
Stratiform Clouds

Abstract. A condensed multiphase halogen and dimethyl sulfide (DMS) chemistry mechanism for application in chemical transport models is developed by reducing the CAPRAM DMS module 1.0 (CAPRAM-DM1.0) and the CAPRAM halogen module 3.0 (CAPRAM-HM3.0). The reduction is achieved by determining the main oxidation pathways from analysing the mass fluxes of complex multiphase chemistry simulations with the air parcel model SPACCIM. These simulations are designed to cover both pristine and polluted marine boundary layer conditions. Overall, the reduced DM1.0 contains 32 gas-phase reactions, 5 phase transfers, and 12 aqueous-phase reactions, of which two processes are described as equilibrium reactions. The reduced CAPRAM-HM3.0 contains 199 gas-phase reactions, 23 phase transfers, and 87 aqueous-phase reactions. For the aqueous-phase chemistry, 39 processes are described as chemical equilibrium reactions. A comparison of simulations using the complete DM1.0 and CAPRAM-HM3.0 mechanisms against the reduced ones indicates that the percentage deviations are below 5 % for important inorganic and organic air pollutants and key reactive species under pristine ocean and polluted conditions. The reduced mechanism has been implemented into the chemical transport model COSMO-MUSCAT and tested by performing 2D-simulations under prescribed meteorological conditions that investigate the effect of stable (stratiform cloud) and more unstable weather conditions (convective clouds) on marine multiphase chemistry. The simulated maximum concentrations of HCl are in the range of 109 molecules cm−3 and those of BrO are at around 1 · 107 molecules cm −3 reproducing the range of ambient measurements. Afterwards, the oxidation pathway of DMS in a cloudy marine atmosphere has been investigated in detail. The simulations demonstrate that clouds have both a direct and an indirect photochemical effect on the multiphase processing of DMS and its oxidation products. The direct photochemical effect is related to in-cloud chemistry that leads to high DMSO oxidation rates and a subsequently enhanced formation of methane sulfonic acid compared to aerosol chemistry. The indirect photochemical effect is characterised by cloud shading, which occurs particularly in the case of stratiform clouds. The lower photolysis rate affects the activation of Br atoms and consequently lowers the formation of BrO radicals. The corresponding DMS oxidation flux is lowered by up to 30 % under thick optical clouds. Moreover, high updraft velocities lead to a strong vertical mixing of DMS into the free troposphere predominately under cloudy conditions. Furthermore, HOX photolysis is reduced as well, resulting in higher HOX-driven sulfite oxidation in aerosol particles below stratiform clouds. Altogether, the present model simulations have demonstrated the ability of the reduced mechanism to be applied in studying marine aerosol cloud processing effects in regional models such as COSMO-MUSCAT and can be applied for more adequate interpretations of complex marine field measurement data, also by other regional models.

scholarly journals Formation mechanism and source apportionment of water-soluble organic carbon in PM<sub>1</sub>, PM<sub>2.5</sub> and PM<sub>10</sub> in Beijing during haze episodes

2018 ◽  
Author(s):  
Qing Yu ◽  
Jing Chen ◽  
Weihua Qin ◽  
Yuepeng Zhang ◽  
Siming Cheng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Water Soluble ◽  
Distribution Characteristics ◽  
Secondary Sources ◽  
Phase Oxidation ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Haze Episode

Abstract. Water soluble organic carbon (WSOC) in atmospheric aerosols may pose significant impacts on haze formation, climate change, and human health. This study investigated the distribution characteristics and sources of WSOC in Beijing based on the diurnal PM1, PM2.5 and PM10 samples collected during haze episodes in winter and early spring of 2017. The haze episode in winter showed elevated level of WSOC, around three times of that in spring. WSOC was enriched in PM2.5 in winter while the proportions in both finer (0–1 μm) and coarse particles (2.5–10 μm) increased in spring. Several organic tracers were carefully selected and measured to demonstrate the sources and formation mechanism of WSOC. Most of the identified organic tracers showed similar seasonal variation, diurnal change and size distributions with WSOC, while the biogenic secondary organic aerosol (SOA) tracer cis-pinonic acid was an obvious exception. Based on the distribution characteristics of the secondary organic tracers and their correlation patterns with key influencing factors, the importance of the gas-phase versus aqueous-phase oxidation processes on SOA formation was explored. The gas-phase photochemical oxidation was weakened during haze episodes, whereas the aqueous-phase oxidation became the major pathway of SOA formation, especially in winter, at night and for the coarser particles. Secondary sources accounted for more than 50 % of WSOC in both winter and spring. Biomass burning was not the dominant source of WSOC in Beijing during haze episodes. Primary sources showed greater influence on finer particles while secondary sources became more important for coarser particles during haze episode in winter. SOC estimated by the OC-EC method, WSOC-levoglucosan method, and PMF-based methods were comparable, and the potential errors for different SOC estimation methods were discussed.

scholarly journals Differences in Model Performance and Source Sensitivities for Sulfate Aerosol Resulting from Updates of the Aqueous- and Gas-Phase Oxidation Pathways for a Winter Pollution Episode in Tokyo, Japan

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 544 ◽  
Author(s):  
Itahashi ◽  
Yamaji ◽  
Chatani ◽  
Hayami
Keyword(s):  
Air Quality ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Model Performance ◽  
Tokyo Bay ◽  
Volcanic Emissions ◽  
Phase Calculation ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
No2 Oxidation

During the Japanese intercomparison study, Japan’s Study for Reference Air Quality Modeling (J-STREAM), it was found that wintertime SO42– concentrations were underestimated over Japan with the Community Multiscale Air Quality (CMAQ) modeling system. Previously, following two development phases, model performance was improved by refining the Fe- and Mn-catalyzed oxidation pathways and by including an additional aqueous-phase pathway via NO2 oxidation. In a third phase, we examined a winter haze period in December 2016, involving a gas-phase oxidation pathway whereby three stabilized Criegee intermediates (SCI) were incorporated into the model. We also included options for a kinetic mass transfer aqueous-phase calculation. According to statistical analysis, simulations compared well with hourly SO42– observations in Tokyo. Source sensitivities for four domestic emission sources (transportation, stationary combustion, fugitive VOC, and agricultural NH3) were investigated. During the haze period, contributions from other sources (overseas and volcanic emissions) dominated, while domestic sources, including transportation and fuel combustion, played a role in enhancing SO42– concentrations around Tokyo Bay. Updating the aqueous phase metal catalyzed and NO2 oxidation pathways lead to increase contribution from other sources, and the additional gas phase SCI chemistry provided a link between fugitive VOC emission and SO42– concentration via changes in O3 concentration.

Towards an advanced description and modelling of the atmospheric multiphase chemistry of mercury: CAPRAM HG module 1.0

2021 ◽  
Author(s):  
Erik Hans Hoffmann ◽  
Tao Li ◽  
Andreas Tilgner ◽  
Yan Wang ◽  
Hartmut Herrmann
Keyword(s):  
Gas Phase ◽  
Aqueous Phase ◽  
Aerosol Particles ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Gas Phase Reactions ◽  
Gaseous Elemental Mercury ◽  
Gas Phase Chemistry ◽  
Reactive Halogen Species ◽  
Phase Chemistry

&lt;p&gt;Mercury is a neurotoxic element emitted predominantly in its less-reactive form as gaseous elemental mercury (GEM) into the atmosphere by various natural and anthropogenic processes. Once emitted it undergoes chemical processing in the atmospheric gas and aqueous phase. There, GEM is oxidised into gaseous oxidised mercury (GOM), which partitions into aerosol particles residing there as particulate bounded mercury (PBM) due to its much higher solubility. The faster deposition of GOM and PBM compared to GEM is of special environmental importance, because they can be converted into more toxic organic mercury in aquatic environments and then take serious place in the food web. Thus, it is crucial for models to understand the transformation of GEM into GOM and PBM and vice versa. To date, numerous gas-phase chemistry simulations were performed, but reveal missing oxidation and reduction processes. However, only few models exist that investigate the multiphase mercury chemistry in a detailed manner.&lt;/p&gt;&lt;p&gt;Therefore, a comprehensive multiphase mercury chemistry mechanism, the CAPRAM HG module 1.0 (CAPRAM-HG1.0), has been developed. The CAPRAM-HG1.0 includes 74 gas-phase reactions, 22 phase transfers and 77 aqueous-phase reactions. It was coupled to the multiphase chemistry mechanism MCMv3.2/CAPRAM4.0 and the extended CAPRAM halogen module 3.0 (CAPRAM-HM3.0) for investigations of multiphase Hg redox under Chinese polluted conditions. Simulations were performed for summer conditions in 2014 using the air parcel model SPACCIM to investigate the performance of the model to simulate typical concentrations and patterns of GEM, GOM and PBM.&lt;/p&gt;&lt;p&gt;Under non-cloud conditions, model results reveal good coincides with concentrations and patterns for GEM, GOM and PBM measured in China. However, the simulations also show that there are still high uncertainties in atmospheric mercury chemistry. Especially, the complexation with HULIS within aerosol particles needs evaluation as the simulations indicate this process as key process driving concentrations and patterns of both GOM and PBM. Further, the present study demonstrates the need of a better understanding of continental concentrations of reactive halogen species and particle bounded halides as well as their link to the multiphase chemistry and atmospheric cycling of mercury.&lt;/p&gt;

scholarly journals Oxidation of SO<sub>2</sub> by stabilized Criegee intermediate (sCI) radicals as a crucial source for atmospheric sulfuric acid concentrations

2013 ◽  
Vol 13 (7) ◽  
pp. 3865-3879 ◽  
Author(s):  
M. Boy ◽  
D. Mogensen ◽  
S. Smolander ◽  
L. Zhou ◽  
T. Nieminen ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Gas Phase ◽  
Oxidation Mechanism ◽  
Ground Level ◽  
Reaction Rates ◽  
Rate Coefficients ◽  
Dimensional Model ◽  
Sulfuric Acid Production ◽  
Criegee Intermediates ◽  
Stabilized Criegee Intermediates

Abstract. The effect of increased reaction rates of stabilized Criegee intermediates (sCIs) with SO2 to produce sulfuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland, and Hohenpeissenberg, Germany. Results from MALTE, a zero-dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calculated by Mauldin et al. (2012) increases sulfuric acid by 30–40%. Increasing the rate coefficient for formaldehyde oxide (CH2OO) with SO2 according to the values recommended by Welz et al. (2012) increases the H2SO4 yield by 3–6%. Taken together, these increases lead to the conclusion that, depending on their concentrations, the reaction of stabilized Criegee intermediates with SO2 could contribute as much as 33–46% to atmospheric sulfuric acid gas phase concentrations at ground level. Using the SMEAR II data, results from SOSA, a one-dimensional model, show that the contribution from sCI reactions to sulfuric acid production is most important in the canopy, where the concentrations of organic compounds are the highest, but can have significant effects on sulfuric acid concentrations up to 100 m. The recent findings that the reaction of sCI + SO2 is much faster than previously thought together with these results show that the inclusion of this new oxidation mechanism could be crucial in regional as well as global models.

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