Isolating Weakly and Strongly-Absorbing Classes of Carbonaceous Aerosol: Optical Properties, Abundance and Lifecycle
- Univ. of Illinois, Urbana-Champaign, IL (United States)
The goal of this project was to evaluate climate-relevant properties of carbonaceous particles and the transformations of those particles in the atmosphere, with the purpose of developing lumped classes of carbonaceous particles suitable for use in large-scale models. These climate-relevant properties included light absorption and hygroscopicity. Hygroscopicity is a measure of water affinity, which governs particle growth at humid conditions and absorption and scattering under those conditions. It also controls particles’ activation into cloud droplets, which in turn affects cloud albedo and particle removal. This project used laboratory measurements of fresh and aged carbonaceous aerosol, and predictions of properties using a particle-resolved model, to identify sensitivities. The focus in this project was on aerosol from biomass pyrolysis, abbreviated BrC (“brown carbon”). We measured absorption by aerosol from biomass pyrolysis from two sources with very different composition: wood and corn stalk. For both sources, the greatest light absorption occurred at the highest generation temperature, and this maximum absorption was very similar to that of wood-generated aerosol. We suggest that pyrolysis products can be considered surrogates for a wide range of biomass aerosol. We captured aerosol emitted from biomass pyrolysis on filters and exposed it to ultraviolet radiation, to the atmospheric trace gases ozone, ammonia (NH3) and nitrogen oxide; and to aqueous saturated salt solutions of ammonium sulfate, ammonium nitrate, sodium chloride and sodium sulfate. Absorption increased, but by only small amounts for all of these treatments, with one exception: after aging with ammonia, absorption increased by almost a factor of four. Absorption increased more at visible wavelengths. We confirmed that a significant change occurred in the aerosol phase, by measuring absorption by suspended particles after aging with NH3 and finding doubled aerosol absorption. Aging by NH3 produces a mild increase in the hygroscopicity of BrC, and a greater increase in cloud condensation nucleus activity. Therefore, reactions with NH3 form compounds that absorb more light than the original aerosol and act as surfactants, increasing the likelihood that these particles will participate in cloud formation. The particle-resolved model PartMC was enhanced to include additional physical processes. It was calibrated against chamber results, and we needed to account for the non-spherical structure of particle agglomerates, even for ammonium sulfate. We implemented the “volatility basis set” (VBS) framework in the model. The updated PartMC-MOSAIC model was able to simulate gas and aerosol concentrations from the CARES campaign at levels similar to observations. The PartMC model was used to evaluate plume dynamics affecting CCN activity of biomass burning aerosols early in a plume. Coagulation limits emission of CCN to about 1016 per kg of fuel. Co-emitted, semi-volatile organic compounds or emission at small particle sizes can homogenize composition before plume exit, and SVOC co-emission can be the main factor determining plume-exit CCN for hydrophobic or small particles. When externally-mixed, accumulation-mode particles are emitted in the absence of SVOCs, CCN can be overestimated by up to a factor of two. This means that measurements made on aerosol from all phases of combustion gathered into a single chamber may incorrectly estimate CCN properties. Based on the findings here, we make some recommendations for use in large-scale models: (1) inventories should represent “internally” versus “externally” mixed under certain combustion conditions; (2) consideration of non-spherical particles when coagulation is important for climate-relevant properties near sources; (3) designating organic biomass particles as weakly absorbing; (4) “inherent absorption” and hygroscopicity are not altered with aging by ozone or ultraviolet light, and inherent absorption is not altered with salt addition, but both cloud activity and absorption are altered by aging with ammonia and could require a separate class in large-scale models.
- Research Organization:
- University of Illinois at Urbana Champaign, Urbana, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science and Technology (ST)
- DOE Contract Number:
- SC0006689
- OSTI ID:
- 1354700
- Report Number(s):
- DOE-UIUC-06689
- Resource Relation:
- Related Information: Peer Reviewed Publications: Published/AcceptedApplication of the stochastic particle-resolved aerosol model PartMC to chamber experiments, J. Tian, B. Brem, M. West, T. C. Bond, M. J. Rood, N. Riemer, in press at Aerosol Science and Technology, March 2017.Light absorption of organic aerosol from pyrolysis of corn stalk, X. Li, Y. Chen and T. C. Bond, Atmospheric Environment 144, 249-256, 2016.Peer Reviewed Publications: SubmittedHygroscopic growth and cloud condensation nuclei activity of fresh and chemically-aged biomass-pyrolyzed organic aerosol, R. U. Shah, H. Emamipour, M. J. Rood, and T. C. Bond, submitted to Aerosol Science and Technology (currently in revision).A plume-exit approach to determine cloud condensation nuclei activity of aerosols from residential biofuel combustion, F. Mena, T. C. Bond, N. Riemer, submitted to Atmospheric Chemistry and Physics (currently in revision).Peer Reviewed Publications: Acknowledging DoE as Funding for Related WorkT. C. Bond, S. J. Doherty, D. W. Fahey, P. M. Forster, T. Berntsen, B. J. DeAngelo, M. G. Flanner, S. Ghan, B. Kārcher, D. Koch, S. Kinne, Y. Kondo, P. K. Quinn, M. C. Sarofim, M. G. Schultz, M. Schulz, C. Venkataraman, H. Zhang, S. Zhang, N. Bellouin, S. K. Guttikunda, P. K. Hopke, M. Z. Jacobson, J. W. Kaiser, Z. Klimont, U. Lohmann, J. P. Schwarz, D. Shindell, T. Storelvmo, S. G. Warren, C. S. Zender, Bounding the role of black carbon in the climate system: A scientific assessment, Journal of Geophysical Research-Atmospheres, 118, doi:10.1002/jgrd.50171, 2013.Lu, Z., D. G. Streets, E. Winijkul, F. Yan, Y. Chen, T. C. Bond, Y. Feng, M. K. Dubey, S. Liu, J. P. Pinto, and G. R. Carmichael, Light Absorption Properties and Radiative Effects of Primary Organic Aerosol Emissions, Environ. Sci. Technol., 49(8), 4868-4877, 10.1021/acs.est.5b00211, 2015.
- Country of Publication:
- United States
- Language:
- English
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