Final Report: Understanding the Hygroscopic Properties of Black Carbon/Organic Carbon Mixing States: Connecting Climate and Health Impacts of Anthropogenic Aerosol

EPA Grant Number: R835040
Title: Understanding the Hygroscopic Properties of Black Carbon/Organic Carbon Mixing States: Connecting Climate and Health Impacts of Anthropogenic Aerosol
Investigators: Asa-Awuku, Akua
Institution: University of California - Riverside
EPA Project Officer: Chung, Serena
Project Period: October 1, 2011 through September 30, 2014 (Extended to September 30, 2016)
Project Amount: $449,925
RFA: Black Carbon's Role In Global To Local Scale Climate And Air Quality (2010) RFA Text |  Recipients Lists
Research Category: Global Climate Change , Climate Change , Air

Objective:

The objective of the study is to understand properties of black carbon (BC) containing aerosol that is well mixed with organic hygroscopic material. The mixtures of BC and organic material significantly affect water uptake and cloud nucleating ability. To address these scientific questions, the principal investigator (PI) (1) has designed a novel apparatus to control and modify BC/organic carbon (OC) aerosol mixing states for subsequent testing; (2) has addressed and identified unique and viable online and offline measurement techniques to characterize BC/OC water-uptake and droplet growth of diverse aerosol sources; and (3) initiated a testing protocol to measure the in situ cloud droplet ability of mixed BC/OC aerosol from alternative fuel emissions and advanced vehicle technologies. 

Summary/Accomplishments (Outputs/Outcomes):

The PI’s research group has investigated the water-nucleating properties of BC containing aerosol from two distinct sources: biomass burning and vehicular emissions. The contribution of BC to the total biomass burning aerosol mass decreases during ageing and photochemistry as additional organic material is formed during controlled aging environmental chamber experiments. The changes in fractal nature and effective particle density have been observed and have been shown to affect cloud nucleation predictions. In addition, the organic mixture has been shown to be surface active; hence, though black carbonaceous material is often considered insoluble, the mixture with surface active organic composition can facilitate cloud nucleation and promote cloud condensation nuclei (CCN) activity in biomass burning systems. This work is now published in leading scientific journals in the field. The PI and her research group also have developed a viable online technique to characterize the water-nucleating properties of BC-aerosol compositions. The technique has been applied to vehicular studies that investigate the emission from alcohol (ethanol – E10 and butanol – B15) gasoline fuel blends in commercial light-duty vehicles. BC concentrations are measured for light-duty vehicles operated on the federal test procedure and unified testing cycle. To date, two distinct vehicle technologies have been tested: port-fuel injection and gasoline direct injection vehicles. The BC concentrations have been compared to insoluble mass fractions inferred with the online technique. Lastly, the PI has designed and developed a mixing apparatus to control and modify BC/OC mixing states. BC emissions data from the vehicle studies has been submitted to journals and is currently in review. The initial CCN mixing state measurements with known aerosol compounds have been conducted with the mixing state apparatus and results are being compiled and will be submitted for publication in 2016. The work also has resulted in three Ph.D. theses. 

Conclusions:

  • The contribution of BC to the total biomass-burning aerosol mass decreases during ageing and photochemistry as additional organic material is formed during controlled ageing environmental chamber experiments.
  • In addition, the organic mixture has been shown to be surface active; hence, though black carbonaceous material is often considered insoluble, the mixture with a surface active organic composition can facilitate cloud nucleation and promote CCN activity in biomass burning systems.
  • The changes in fractal nature and effective particle density have been observed and affect cloud nucleation predictions. The effective density of a biomass particle can enhance apparent hygroscopicity three-fold. Using a closer approximation of the spherical size with the use of effective density and TEM images shows that the CCN activity of BC containing biomass-burning aerosol is much larger than expected.
  • BC concentrations have been measured for light-duty vehicles operated on the Federal Test Procedure and Unified Testing Cycle. In both cycles, BC concentrations are greatest in the first cold start phase.
  • The PI and her research group have developed a viable online technique to understand the nucleating properties of BC-aerosol compositions. The technique has been applied to vehicular studies that investigate the emission from alcohol (ethanol – E10, E15, E20 and butanol – Bu16, Bu24, Bu32) gasoline fuel blends in commercial light-duty vehicles.
  • The PI completed the construction of the mixing apparatus in the second year and has collected preliminary data with known compounds as proposed. The behavior of mixing state on CCN activation has been observed. Multiple activation peaks correspond to mixed aerosol. The process for which CCN observed in laboratory or in the field must account for mixing state of complex aerosol sources. 


Journal Articles on this Report : 9 Displayed | Download in RIS Format

Other project views: All 34 publications 9 publications in selected types All 9 journal articles
Type Citation Project Document Sources
Journal Article Giordano MR, Short DZ, Hosseini S, Lichtenberg W, Asa-Awuku AA. Changes in droplet surface tension affect the observed hygroscopicity of photochemically aged biomass burning aerosol. Environmental Science & Technology 2013;47(19):10980-10986. R835040 (2013)
R835040 (2014)
R835040 (2015)
R835040 (Final)
  • Abstract from PubMed
  • Full-text: ES&T-Full Text HTML
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  • Abstract: ES&T-Abstract
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  • Other: ES&T-Full Text PDF
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  • Journal Article Giordano MR, Asa-Awuku A. Rebuttal to correspondence on "Changes in droplet surface tension affect the observed hygroscopicity of photochemically aged biomass burning aerosol". Environmental Science & Technology 2014;48(3):2084-2085. R835040 (2014)
    R835040 (2015)
    R835040 (Final)
  • Abstract from PubMed
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  • Abstract: ES&T-First Page Preview
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  • Other: ES&T-Full Text PDF
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  • Journal Article Giordano M, Espinoza C, Asa-Awuku A. Experimentally measured morphology of biomass burning aerosol and its impacts on CCN ability. Atmospheric Chemistry and Physics 2015;15(4):1807-1821. R835040 (2014)
    R835040 (2015)
    R835040 (Final)
  • Full-text: ACP-Full Text PDF
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  • Abstract: ACP-Abstract
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  • Other: ResearchGate-Abstract & Full Text PDF
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  • Journal Article Karavalakis G, Short D, Vu D, Villela M, Russell R, Jung H, Asa-Awuku A, Durbin T. Regulated emissions, air toxics, and particle emissions from SI-DI light-duty vehicles operating on different iso-butanol and ethanol blends. SAE International Journal of Fuels and Lubricants 2014;7(1):183-199. R835040 (2014)
    R835040 (2015)
    R835040 (Final)
  • Full-text: University of California-Full Text PDF
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  • Abstract: SAE International-Abstract
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  • Journal Article Karavalakis G, Short D, Vu D, Villela M, Asa-Awuku A, Durbin TD. Evaluating the regulated emissions, air toxics, ultrafine particles, and black carbon from SI-PFI and SI-DI vehicles operating on different ethanol and iso-butanol blends. Fuel 2014;128:410-421. R835040 (2014)
    R835040 (2015)
    R835040 (Final)
  • Full-text: ScienceDirect-Full Text HTML
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDirect-Full Text PDF
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  • Journal Article Short DZ, Vu D, Durbin TD, Karavalakis G, Asa-Awuku A. Components of particle emissions from light-duty spark-ignition vehicles with varying aromatic content and octane rating in gasoline. Environmental Science & Technology 2015;49(17):10682-10691. R835040 (Final)
  • Abstract from PubMed
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  • Abstract: ES&T-Abstract
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  • Other: ES&T-Full Text PDF
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  • Journal Article Short D, Giordano M, Zhu Y, Fine PM, Polidori A, Asa-Awuku A. A unique online method to infer water-insoluble particle contributions. Aerosol Science and Technology 2014;48(7):706-714. R835040 (2012)
    R835040 (2014)
    R835040 (2015)
    R835040 (Final)
  • Full-text: Taylor&Francis-Full Text PDF
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  • Abstract: Taylor&Francis-Abstract
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  • Journal Article Short D, Vu D, Durbin TD, Karavalakis G, Asa-Awuku A. Particle speciation of emissions from iso-butanol and ethanol blended gasoline in light-duty vehicles. Journal of Aerosol Science 2015;84:39-52. R835040 (2014)
    R835040 (2015)
    R835040 (Final)
  • Full-text: ScienceDirect-Full Text HTML
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDirect-Full Text PDF
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  • Journal Article Short D, Vu D, Chen V, Espinoza C, Berte T, Karavalakis G, Durbin TD, Asa-Awuku A. Understanding particles emitted from spray and wall-guided gasoline direct injection and flex fuel vehicles operating on ethanol and iso-butanol gasoline blends. Aerosol Science and Technology 2017;51(3):330-341. R835040 (Final)
  • Full-text: Journal-dl-Full Text PDF
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  • Abstract: Taylor&Francis-Abstract
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  • Supplemental Keywords:

    Aerosol-indirect effect, atmospheric pollution, black carbon, climate, mixing state, particle hygroscopicity, tropospheric aerosol

    Progress and Final Reports:

    Original Abstract
    2012 Progress Report
    2013 Progress Report
    2014 Progress Report
    2015 Progress Report