Grantee Research Project Results
Final Report: Rethinking the Formation of Secondary Organic Aerosols (SOA) Under Changing Climate by Incorporating Mechanistic and Field Constraints
EPA Grant Number: R835877Title: Rethinking the Formation of Secondary Organic Aerosols (SOA) Under Changing Climate by Incorporating Mechanistic and Field Constraints
Investigators: Jimenez, Jose-Luis , Emmons, Louisa , Hodzic, Alma , Aumont, Bernard , Lamarque, Jean-Francois , Madronich, Sasha
Institution: University of Colorado at Boulder , National Center for Atmospheric Research
EPA Project Officer: Keating, Terry
Project Period: January 1, 2016 through December 31, 2018 (Extended to October 15, 2020)
Project Amount: $469,808
RFA: Particulate Matter and Related Pollutants in a Changing World (2014) RFA Text | Recipients Lists
Research Category: Air , Climate Change
Objective:
The overall objective of this work is to evaluate the changes and impacts of secondary organic aerosols (SOA) under current and future climate scenarios, using more realistic formation mechanisms than have been used in past studies. This is important because SOA has important impacts on human health and radiative forcing, and at present it is unclear how those effects will change under future climate and emission conditions. SOA parameterizations have been made more realistic and traceable by constraining them with the semi-explicit and explicit models, and constraining them with oxidation flow reactor (OFR), thermodenuder (TD), environmental chamber, and ambient observations. Regional and global model results have been evaluated against observations from high quality airborne field campaigns and from ground sites and networks. The 3D models were then used to project the changes and impacts of SOA under future climate scenarios.
As part of these investigations of SOA, in addition to the larger-scale modeling efforts, a wide range of box and chemical modeling and field data investigations were conducted to better understand properties and processes (e.g., volatility, SOA formation potential and yields, new particle formation, gas-particle partitioning) that are important for controlling SOA formation and life cycles in the atmosphere and within tools used to study SOA (e.g., OFR, TD, environmental chambers, chemical kinetic simulation software). Developments and findings from those efforts will help to provide more effective tools and new constraints to study and understand SOA, and thus aid in further improvements of larger scale SOA modeling.
Conclusions:
There are 3 main objectives in this project: (1) develop and test updated SOA formation parameterizations; (2) calculate present SOA using 3D models and compare to observations; and (3) evaluate SOA using 3D models under future climate scenarios. Work was completed on all three objectives. A summary of the results are described below and directly address the objectives of this proposal and will help improve SOA modeling under current and future climate scenarios. Therefore, these results contribute to EPA’s mission to protect human health and the environment through the improved understanding and ability to predict the behavior of aerosols in the atmosphere, which are known to have major effects on human health and climate. The improved understanding provided by the more efficient and accurate modeling, will aid in devising and implementing effective strategies to mitigate air pollution-related health effects and climate change and help society adapt to current and future environmental changes.
Objective 1: Improve SOA mechanisms for use in global models
- New SOA modules for global models have been developed using the Statistical Oxidation Model (SOM). The SOM is a semi-explicit model, which was fit to results from chamber experiments. This process allowed taking into account the effect of vapor wall losses on chamber experiments, which results in larger SOA yields, although the effects are quite sensitive to the precursor/oxidant combination. These results are documented in Hodzic et al. (2016).
- We proposed to use emerging constraints from oxidation of ambient air in Oxidation Flow Reactors (OFRs). The interpretation of the OFR results, in order to allow evaluation of SOA models, has turned out to be quite complex. For this reason we invested a considerable amount of effort to clarify this interpretation, including the quantitative aspects: estimation of OH and NO3 exposures, lack of importance of irrelevant chemistry, quantification of SOA yields, and similarity between the detailed chemistry in the OFR vs. ambient air and laboratory chambers. These results are documented in several publications (Peng et al., 2015, 2016, 2018, 2019; Peng and Jimenez, 2017, 2020). We publically released an explicit model of the radical chemistry in OFRs (Peng et al., 2020), which has been experimentally verified and can be run within the free KinSim software that we also released (Peng and Jimenez, 2019). We also performed analyses on multiple ambient datasets where OFRs were used to oxidize ambient air in urban and forested locations, which provide useful constraints to SOA models (Palm et al., 2016; 2017; 2108; Ortega et al., 2016). We found that SOA formation from OH oxidation of ambient air is underpredicted in all locations when using only VOC precursors, and that semivolatile and intermediate volatility precursors are needed to close the gap. In contrast, SOA formation from ozone or NO3 radicals was reasonably captured by models. Finally, we performed a collaborative study of new particle formation (NPF) from oxidation of ambient air in an OFR, which enables a better understanding on using that technique to study NPF in the future (Hodshire et al., 2018).
- An important property of SOA from a global model perspective is its volatility. Older models represented SOA as too volatile, which led to very large effects of temperature on SOA mass as the air moved to different atmospheric regions. E.g., some models predicted large amounts of SOA in the upper free troposphere due to this effect, which are not present in the observations. We proposed to use the results of thermal denuder measurements to provide a constraint on the volatility of model SOA. However, there has been some controversy in the field about the realism of VBS determined from thermal denuder measurements. We have worked to clarify this issue, and investigations resulted in a paper where we show that TD measurements provide the most accurate representation of OA volatility among the methods currently available (Stark et al., 2017). Based on this information, we then used the TD results from multiple field campaigns to evaluate the volatility of the new VBS parameterizations.
- A parameterization method has been developed to simulate the SOA formed from isoprene-derived epoxydiols (IEPOX-SOA). Our parameterization enables the fast calculation of IEPOX-SOA mass, maintaining accuracy compared to full chemistry simulation results. It uses the chemical environment (e.g., OH, HO2, and NO) and aerosol properties (e.g., pH and surface area), to estimate the yield of this chemistry at different locations. This results in much better accuracy compared to the constant 3% yield from isoprene emissions used in most global modeling studies. Our parameterization accurately captures the response to changes on NOx and SO2 emissions, which is a critical factor for long-term climate simulations. This is a major improvement compared to the constant 3% yield and VBS approaches, that show almost no response of isoprene SOA after large changes on NOx and/or SO2. A paper detailing these findings has been published in Geoscientific Model Development (Jo et al., 2019).
- We have explored applying a simpler box model (KinSim, within Igor Pro) and the fully explicit GECKO-A box model to simulate in detail the chemistry within the oxidation flow reactors (OFR), including that of oxidized nitrogen species, peroxy radicals, and volatile organic compounds. We are also developing an interface using Igor Pro to enable the exploration of GECKO-A results in a non-Unix setting (i.e. Windows or Mac). The results show reasonable correspondence to simulated chemistry in a typical chamber and in the ambient atmosphere under a subset of explored physical conditions, which have been identified. In particular, we have found that under low-NO conditions, achieving a peroxy radical chemistry that is as relevant to the atmosphere as possible requires physical conditions leading to relatively low OH exposure (compared to the highest achievable OFR OH concentrations, but still much higher than ambient values) to allow isomerizations of peroxy radicals and avoid their reactions with OH. These results have been published in a manuscript (Peng et al., 2019). We were also invited by Chemical Society Reviews to contribute a review paper summarizing all the recent findings of OFR radical chemistry, which was also recently published (Peng and Jimenez, 2020).
- A new VBS parametrization has been developed for monoterpene-derived SOA. We have taken into account as many constraints as possible, including constraints from field measurements. These include SOA yields at OA concentrations of ~1–10 μg m-3 measured in traditional chamber experiments, new SOA yields at very low OA concentrations (from extremely low volatility species, or ELVOCs), OA volatility quantified in aircraft measurements under small temperature changes, and OA evaporation at higher temperatures in thermal denuder (TD) experiments. With these constraints considered, the new parametrization would be suitable for modeling monoterpene-derived SOA formation more robustly across a range of conditions, in pristine regions (where only low-volatility species contribute to OA growth), in colder regions (e.g., the Arctic or the upper free troposphere), and in a warming climate.
- The Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) box model has been used under multiple environmental conditions to study the SOA formation and properties from typical hydrocarbon precursors and (ii) to fit a Volatility Basis Set (VBS) type parameterization, which can be used in 3D models. The set of parent hydrocarbons includes n-alkanes and 1-alkenes with 10, 14, 18, 22, and 26 carbon atoms,α-pinene, β-pinene and limonene, benzene, toluene, o-xylene, m-xylene and p-xylene. Isoprene chemistry was not considered as GECKO does not treat the aqueous phase formation, and a different approach has been adapted to develop a parameterization for isoprene SOA (see above). Its evaluation shows that VBS-GECKO captures the dynamic of SOA formation for a large range of conditions within 20% of the explicit simulations. This VBS-GECKO is however computationally very demanding, and we are currently working on a reduced version of it. A paper detailing these results has been published (Lannuque et al., 2018).
- SOA formation in winter in the NE US and over Seoul, South Korea, has been quantified and compared to prior studies (Nault et al., 2018; Schroder et al., 2018; Shah et al., 2019). A broad survey of observations in urban outflow (11 urban areas in 3 continents) showed that anthropogenic SOA (ASOA) was pervasively a large contribution to submicron particles, but with variable production efficiencies. The differences and the factors controlling SOA production efficiency among megacities was investigated. Dependencies on VOC emissions composition such as differences in the emissions of aromatics and intermediate-and semi-volatile organic compounds, and on relative contributions from sources, have been found. Parameterizations of those relationships and associated emissions have been incorporated into a GEOS-Chem chemical transport model to show that globally ~340,000 less premature deaths per year are attributed to ASOA. Further details can be found in Nault et al., (2020).
- Net SOA formation from wildfire plumes is a controversial topic, with field studies showing typically no increase or decrease in mass with photochemical aging, while lab studies suggest very strong increases in mass due to SOA formation. We have collaborated on a Critical Review in ES&T that summarizes all the literature studies to date, and set up the state of the field ahead of the WE-CAN and FIREX-AQ experiments (Hodshire et al., 2019).
- We studied the effect of walls on SOA yields in Teflon chambers when operated in both batch and flowthrough modes. Prior publications have argued that flowthrough chambers are not subject to wall losses, however our results show that this is incorrect, and that wall losses can be very important under the typical conditions where such chambers are run in the literature. The results and methods will help in interpretation and experimental planning for SOA-formation chamber experiments. (Krechmer et al., 2020)
Objective 2: Implement the new mechanisms in global models and simulate present conditions
- New mechanisms based on SOM (and on GECKO for some precursors) were implemented in GEOS-Chem and evaluated against observations, as documented in Hodzic et al. (2016). The updated model presents a more dynamic picture of the life cycle of atmospheric SOA, with production rates 3.9 times higher and sinks a factor of 3.6 more efficient than in the base model. In particular, the updated model predicts larger SOA concentrations in the boundary layer and lower concentrations in the upper troposphere, leading to better agreement with surface and aircraft measurements of organic aerosol compared to the base model. Our analysis thus suggests that the long-standing discrepancy in model predictions of the vertical SOA distribution can now be resolved, at least in part, by a stronger source and stronger sinks leading to a shorter lifetime. The predicted global SOA burden in the updated model is 0.88 Tg and the corresponding direct radiative effect at top of the atmosphere is −0.33 W m-2, which is comparable to recent model estimates constrained by observations. The updated model predicts a population-weighted global mean surface SOA concentration that is a factor of 2 higher than in the base model, suggesting the need for a reanalysis of the contribution of SOA to PM pollution-related human health effects.
- New parameterizations developed in this project have been applied to two major 3D global chemistry models — GEOS-Chem and CAM-chem. First, IEPOX-SOA parameterization was implemented in the GEOS-Chem. The parameterization successfully captures global spatial and temporal distributions of IEPOX-SOA simulated by the explicit full chemistry (Jo et al., 2019). Second, the new VBS parametrization for monoterpene SOA is implemented in CAM-chem. The result shows substantial changes in SOA concentrations for pristine and colder regions, which can help to understand SOA partitioning of 3D models in these regions.
- Our group has acquired (with separate funding) a unique global dataset of OA on the NASA ATOM campaigns, which sampled the remote free troposphere over the Pacific and Atlantic, from pole to pole, over 4 seasons. Results from these measurements have been extensively compared to results from different global models, including CESM/CAM-Chem, GEOS-Chem and several other GCMs. While the new implementations of CAM-Chem and GEOS-Chem reproduce total OA observations fairly well, this is partially for the wrong reasons as POA is severely overestimated and SOA is underestimated. Model sensitivities were investigated with respect to wall-corrected yields, photolytic removal, heterogeneous reaction with ozone, convective removal, SOA sources, and the degree of oxygenation. A paper evaluating the models with the ATOM measurements has been published (Hodzic et al., 2020).
Objective 3: Evaluate SOA using 3D models under future climate scenarios
- We have updated the Community Earth System Model (CESM) version 2.1.0 to incorporate the mechanistic approach of SOA simulation especially for IEPOX-SOA, including the detailed isoprene gas-phase chemistry, aerosol thermodynamic model, and heterogeneous reactive uptake process of IEPOX. The updated model was used to conduct four Tier 1 SSP socioeconomic pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) for the 2050s. We have found that IEPOX-SOA is predicted to be increased over Tropics in all future climatic conditions mainly due to increased isoprene, but it can be either increased or decreased over the US according to the scenario and model assumptions (due to inhibiting effects of IEPOX-SOA formation, such as decreased aerosol acidity and surface area). Effects of CO2 inhibition on isoprene emissions are also explored, which have a major effect but are very uncertain. We also found that the isoprene emission was the main driving factor of IEPOX-SOA burden differences between the SSP scenarios, but the chemistry was important, and can change the SOA burden per unit isoprene emission up to 50% (SSP3-7.0 vs SSP1-2.6). We have analyzed the results in detail and a paper has been submitted and revised after peer-review (Jo et al. 2020).
Journal Articles on this Report : 6 Displayed | Download in RIS Format
Other project views: | All 53 publications | 53 publications in selected types | All 53 journal articles |
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Jo D, Hodzic A, Emmons L, Tilmes S, Schwantes R, Mills M, Campuzano-Jost P, Hu W, Zaveri R, Easter R, Singh B, Lu Z, Schulz C, Schneider J, Schilling J, Wisthaler A, Himinez J. Future changes in isoprene-epoxydiol-derived secondary organic aerosol IEPOX SOA under the Shared Socioeconomic Pathways:the importance of physicochemical dependency. ATMOSPHERIC CHEMISTRY AND PHYSICS 2021;21(5):3395-3425. |
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Nault BA, Jo DS, McDonald BC, Campuzano-Jost P, Day DA, Hu WW, Schroder JC, Allan J, Blake DR, Canagaratna MR, Coe H, Coggon MM, DeCarlo PF, Diskin GS, Dunmore R, Flocke F, Fried A, Gilman JB, Gkatzelis G, Hamilton JF, Hanisco TF, Hayes PL, Henze DK, Hodzic A, Hopkins J, Hu M, Huey LG, Jobson BT, Kter WC, Lewis A, Li M, Liao J, Nawaz MO, Pollack IB, Peischl J, Rappengluck B, Reeves CE, Richter D, Roberts JM, Ryerson TB, Shao M, Sommers JM, Walega J, Warneke C, Weibring P, Wolfe GM, Young DE, Yuan B, Zhang Q, de Gouw JA, Jimenez JL. Secondary organic aerosols from anthropogenic volatile organic compounds contribute substantially to air pollution mortality. ATMOSPHERIC CHEMISTRY AND PHYSICS 2021;21(14):11201-11224. |
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Nguyen TKV, Zhang Q, Jimenez JL, Pike M, Carlton AG. Liquid water: ubiquitous contributor to aerosol mass. Environmental Science & Technology Letters 2016;3(7):257-263. |
R835877 (2016) R835877 (2017) R835877 (2018) R835877 (2019) R835877 (Final) R835041 (Final) |
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Reddington CL, Carslaw KS, Stier P, Schutgens N, Coe H, Liu D, Allan J, Browse J, Pringle KJ, Lee LA, Yoshioka M, Johnson JS, Regayre LA, Spracklen DV, Mann GW, Clarke A, Hermann M, Henning S, Wex H, Kristensen TB, Leaitch WR, Poeschl U, Rose D, Andreae MO, Schmale J, Kondo Y, Oshima N, Schwarz JP, Nenes A, Anderson B, Roberts GC, Snider JR, Leck C, Quinn PK, Chi X, Ding A, Jimenez JL, Zhang Q. The Global Aerosol Synthesis and Science Project (GASSP): measurements and modelling to reduce uncertainty. Bulletin of the American Meteorological Society 2017;98(9):1857-1877. |
R835877 (2017) R835877 (2018) R835877 (2019) R835877 (Final) |
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Fry JL, Brown SS, Middlebrook AM, Edwards PM, Campuzano-Jost P, Day DA, Jimenez JL, Allen HM, Ryerson TB, Pollack I, Graus M, Warneke C, de Gouw JA, Brock CA, Gilman J, Lerner BM, Dubé WP, Liao J and Welti A. Secondary organic aerosol (SOA) yields from NO3 radical + isoprene based on nighttime aircraft power plant plume transects. Atmospheric Chemistry and Physics 2018; 18(16):11663-11682. |
R835877 (2018) R835877 (2019) R835877 (Final) R835399 (Final) |
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Hodzic A, Campuzano-Jost P, Bian H, Chin M, Colarco PR, Day DA, Froyd KD, Heinold B, Jo DS, Katich JM, Kodros JK, Nault BA, Pierce JR, Ray E, Schacht J, Schill GP, Schroder JC, Schwarz JP, Sueper DT, Tegen I, Tilmes S, Tsigaridis K, Yu P and Jimenez JL. Characterization of organic aerosol across the global remote troposphere:a comparison of ATom measurements and global chemistry models. Atmospheric Chemistry and Physics 2020; 20(8):4607-4635. |
R835877 (2019) R835877 (Final) |
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Supplemental Keywords:
secondary organic aerosol, SOA, modeling, atmospheric chemistry, air, ambient air, global climate, air quality, tropospheric, health effects, human health, environmental chemistry, oxidation flow reactor, OFR, organic aerosol, IEPOX, IEPOX-SOA, volatility, thermal denuder, GECKO, KinSim, GeosChem, CESM, VBS, ASOA, peroxy radicals, 3D model, CAM-chem, SOM, gas-particle partitioning, monoterpene, ATom
Relevant Websites:
- OFR Tutorial and operation /interpretation recommendations Exit
- OFR chemistry estimation equations, and RO2 fate estimation equation Exit
- KinSim chemical kinetics software instructions and introduction Exit
- KinSim chemical kinetics downloadable mechanisms Exit
- Group publications list Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
- 2019 Progress Report
- 2018 Progress Report
- 2017 Progress Report
- 2016 Progress Report
- Original Abstract
53 journal articles for this project