Development of a protocol for the auto-generation of explicit aqueous-phase oxidation schemes of organic compounds

Bräuer, Peter; Mouchel‐Vallon, Camille; Tilgner, Andreas; Mutzel, Anke; Böge, Olaf; Rodigast, Maria; Poulain, Laurent; Pinxteren, Dominik van; Wolke, Ralf; Aumont, Bernard; Herrmann, Hartmut

doi:10.5194/acp-19-9209-2019

Cited by 36 publications

(40 citation statements)

References 66 publications

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“…The key sinks of Pyr under daytime in-cloud conditions are aqueous-phase reactions of pyruvate with OH (58 %) and H 2 O 2 (29 %). This finding is consistent with results from laboratory experiments (Carlton et al, 2006). Under nighttime in-cloud conditions, the sink fluxes are very low and therefore can be ignored.…”

Section: Pyruvic Acid (Pyr)supporting

confidence: 92%

Multiphase MCM–CAPRAM modeling of the formation and processing of secondary aerosol constituents observed during the Mt. Tai summer campaign in 2014

Zhu¹,

Tilgner²,

Hoffmann³

et al. 2020

Atmos. Chem. Phys.

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Abstract. Despite the high abundance of secondary aerosols in the atmosphere, their formation mechanisms remain poorly understood. In this study, the Master Chemical Mechanism (MCM) and the Chemical Aqueous-Phase Radical Mechanism (CAPRAM) are used to investigate the multiphase formation and processing of secondary aerosol constituents during the advection of air masses towards the measurement site of Mt. Tai in northern China. Trajectories with and without chemical–cloud interaction are modeled. Modeled radical and non-radical concentrations demonstrate that the summit of Mt. Tai, with an altitude of ∼1.5 km a.m.s.l., is characterized by a suburban oxidants budget. The modeled maximum gas-phase concentrations of the OH radical are 3.2×106 and 3.5×106 molec. cm−3 in simulations with and without cloud passages in the air parcel, respectively. In contrast with previous studies at Mt. Tai, this study has modeled chemical formation processes of secondary aerosol constituents under day vs. night and cloud vs. non-cloud cases along the trajectories towards Mt. Tai in detail. The model studies show that sulfate is mainly produced in simulations where the air parcel is influenced by cloud chemistry. Under the simulated conditions, the aqueous reaction of HSO3- with H2O2 is the major contributor to sulfate formation, contributing 67 % and 60 % in the simulations with cloud and non-cloud passages, respectively. The modeled nitrate formation is higher at nighttime than during daytime. The major pathway is aqueous-phase N2O5 hydrolysis, with a contribution of 72 % when cloud passages are considered and 70 % when they are not. Secondary organic aerosol (SOA) compounds, e.g., glyoxylic, oxalic, pyruvic and malonic acid, are found to be mostly produced from the aqueous oxidations of hydrated glyoxal, hydrated glyoxylic acid, nitro-2-oxopropanoate and hydrated 3-oxopropanoic acid, respectively. Sensitivity studies reveal that gaseous volatile organic compound (VOC) emissions have a huge impact on the concentrations of modeled secondary aerosol compounds. Increasing the VOC emissions by a factor of 2 leads to linearly increased concentrations of the corresponding SOA compounds. Studies using the relative incremental reactivity (RIR) method have identified isoprene, 1,3-butadiene and toluene as the key precursors for glyoxylic and oxalic acid, but only isoprene is found to be a key precursor for pyruvic acid. Additionally, the model investigations demonstrate that an increased aerosol partitioning of glyoxal can play an important role in the aqueous-phase formation of glyoxylic and oxalic acid. Overall, the present study is the first that provides more detailed insights in the formation pathways of secondary aerosol constituents at Mt. Tai and clearly emphasizes the importance of aqueous-phase chemical processes on the production of multifunctional carboxylic acids.

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Section: Pyruvic Acid (Pyr)supporting

confidence: 92%

Multiphase MCM–CAPRAM modeling of the formation and processing of secondary aerosol constituents observed during the Mt. Tai summer campaign in 2014

Zhu¹,

Tilgner²,

Hoffmann³

et al. 2020

Atmos. Chem. Phys.

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“…ISORROPIA II uses mean activity coefficients for the cation-anion pairs in solution. For this, the Kusik and Meissner (1978) model for specific ionic pairs is applied in combination with the Bromley (1973) mixing rule for activity coefficients in the multicomponent mixtures found in the aerosol. ALWC is computed as a function of RH, using the Zdanovskii-Stokes-Robinson relation (Stokes and Robinson, 1966;Zdanovskii, 1948), using a water activity database computed from the E-AIM thermodynamic model, and incorporating the effect of temperature.…”

Section: Isorropia IImentioning

confidence: 99%

“…Together, using standard relationships, these enable mean activity coefficients to be calculated for different temperatures. Mean ionic activity coefficients in mixtures are estimated using the approach of Bromley (1973), based on values for the constituent pure aqueous solutions at the total ionic strength of the mixture. The equilibrium HSO − 4 H + + SO 2− 4 is calculated explicitly and is based on the same thermodynamic treatment as in E-AIM .…”

Section: Equisolv IImentioning

confidence: 99%

“…These models are based on the PSC model for activity coefficient and pH calculations, either directly or via polynomial expressions fitted to that model (and are thus related to E-AIM). The models SCAPE and SCAPE 2 (with NVCs), for inorganic aerosol thermodynamics (Kim and Seinfeld, 1995;Kim et al, 1993a, b), implement several activity coefficient methods, including Bromley's method (Bromley, 1973), the Kusik and Meissner method (Kusik and Meissner, 1978), and a Pitzer model. The Equilibrium Simplified Aerosol Model (EQSAM) (Metzger et al, 2002(Metzger et al, , 2006 computes gas-liquid-solid partitioning for aqueous inorganic aerosol systems, including crustal cations and iron (II, III) species.…”

Section: Other Thermodynamic Modelsmentioning

confidence: 99%

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The acidity of atmospheric particles and clouds

et al. 2020

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Abstract. Acidity, defined as pH, is a central component of aqueous chemistry. In the atmosphere, the acidity of condensed phases (aerosol particles, cloud water, and fog droplets) governs the phase partitioning of semivolatile gases such as HNO3, NH3, HCl, and organic acids and bases as well as chemical reaction rates. It has implications for the atmospheric lifetime of pollutants, deposition, and human health. Despite its fundamental role in atmospheric processes, only recently has this field seen a growth in the number of studies on particle acidity. Even with this growth, many fine-particle pH estimates must be based on thermodynamic model calculations since no operational techniques exist for direct measurements. Current information indicates acidic fine particles are ubiquitous, but observationally constrained pH estimates are limited in spatial and temporal coverage. Clouds and fogs are also generally acidic, but to a lesser degree than particles, and have a range of pH that is quite sensitive to anthropogenic emissions of sulfur and nitrogen oxides, as well as ambient ammonia. Historical measurements indicate that cloud and fog droplet pH has changed in recent decades in response to controls on anthropogenic emissions, while the limited trend data for aerosol particles indicate acidity may be relatively constant due to the semivolatile nature of the key acids and bases and buffering in particles. This paper reviews and synthesizes the current state of knowledge on the acidity of atmospheric condensed phases, specifically particles and cloud droplets. It includes recommendations for estimating acidity and pH, standard nomenclature, a synthesis of current pH estimates based on observations, and new model calculations on the local and global scale.

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“…For current model applications, the existing aqueous-phase mechanism CAPRAM 3.0i (Herrmann et al, 2005;Tilgner and Herrmann, 2010;Tilgner et al, 2013) and the latest CAPRAM4.0 (Bräuer et al, 2019) were rather complex. Hence, a condensed chemical mechanism that still reflects the main chemical processes in tropospheric cloud droplets and deliquesced particles was extracted from the CAPRAM3.0i mechanism.…”

Section: Multiphase Chemistry Mechanismmentioning

confidence: 99%

Treatment of non-ideality in the multiphase model SPACCIM-Part2: Impacts on the multiphase chemical processing in deliquesced aerosol particles

Rusumdar

Tilgner

Wolke

et al. 2019

Preprint

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Abstract. Tropospheric deliquesced particles are characterised by concentrated non-ideal solutions (<q>aerosol liquid water</q> or ALW) that can affect the occurring multiphase chemistry. However, such non-ideal solution effects have generally not yet been considered in and investigated by current complex multiphase chemistry models in an adequate way. Therefore, the present study aims at accessing the impact of non-ideality on multiphase chemical processing in concentrated aqueous aerosols. Simulations with the multiphase chemistry model (SPACCIM-SpactMod) are performed in different environmental and microphysical conditions with and without a treatment of non-ideal solutions in order to assess its impact on aqueous-phase chemical processing. The present study shows that activity coefficients of inorganic ions are often below unity under 90&#8201;% RH-deliquesced aerosol conditions, and that most uncharged organic compounds exhibit activity coefficient values of around or even above unity. Due to this behaviour, model studies have revealed that the inclusion of non-ideality considerably affects the multiphase chemical processing of transition metal ions (TMIs), oxidants, and related chemical subsystems such as organic chemistry. In detail, both the chemical formation and oxidation fluxes of Fe(II) are substantially lowered by a factor of 2.8 in the non-ideal base case compared to the ideal case. The reduced Fe(II) processing in the non-ideal base case, including lowered chemical fluxes of the Fenton reaction (&#8722;70&#8201;%), leads to a reduced processing of HOx/HOy. under deliquesced aerosol conditions. Consequently, higher multiphase H2O2 concentrations (larger by a factor of 3.1) and lower aqueous-phase OH concentrations (lower by a factor of &#8776;&#8201;4) are modelled during non-cloud periods. For H2O2, a comparison of the chemical reaction fluxes reveals that the most important sink, the reaction with HSO3&#8722;, contributes with a 40&#8201;% higher flux in the non-ideal base case than in the ideal case, leading to more efficient sulfate formation. On the other hand, the chemical fluxes of the OH radical are about 50&#8201;% lower in the non-ideal base case than in the ideal case, including lower degradation fluxes of organic aerosol components. Thus, considering non-ideality influences the chemical processing and the concentrations of organic compounds under deliquesced particle conditions in a compound-specific manner. For example, the reduced oxidation budget under deliquesced particle conditions leads to both increased and decreased concentration levels, e.g. of important C2/C3 carboxylic acids. For oxalic acid, the present study demonstrates that the non-ideality treatment enables more realistic predictions of high oxalate concentrations than observed under ambient highly polluted conditions. Furthermore, the simulations implicate that lower humidity conditions, i.e. more concentrated solutions, might promote higher oxalic acid concentration levels in aqueous aerosols due to differently affected formation and degradation processes.

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Development of a protocol for the auto-generation of explicit aqueous-phase oxidation schemes of organic compounds

Cited by 36 publications

References 66 publications

Multiphase MCM–CAPRAM modeling of the formation and processing of secondary aerosol constituents observed during the Mt. Tai summer campaign in 2014

Multiphase MCM–CAPRAM modeling of the formation and processing of secondary aerosol constituents observed during the Mt. Tai summer campaign in 2014

The acidity of atmospheric particles and clouds

Treatment of non-ideality in the multiphase model SPACCIM-Part2: Impacts on the multiphase chemical processing in deliquesced aerosol particles

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