2013 Progress 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 Period Covered by this Report: October 1, 2012 through September 30,2013
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


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 PI 1) has designed a novel apparatus to control and modify BC/OC aerosol mixing states for subsequent testing; 2) has addressed and identified unique and viable on-line and off-line 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.

Progress Summary:

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 black carbon to the total biomass burning aerosol mass decreases during ageing and photochemistry as additional organic material is formed during controlled ageing 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 CCN activity in biomass burning systems. The PI and her research group have also developed a viable on-line 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. In the 2nd year of the proposed work, the majority of biomass burning studies have been completed; BC emissions data from the vehicle studies is nearing final testing and initial CCN mixing state measurements with known aerosol compounds have been conducted with the mixing state apparatus.

Future Activities:

The PI will focus on the mixing apparatus studies in the laboratory environment. Preliminary studies have been made with known inorganic and organic mixtures. PI will introduce and modify BC/OC mixing states in the final Year. Results from both biomass burning and vehicular emissions are slated for publication in the subsequent reporting period.

Journal Articles on this Report : 1 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
  • Abstract: ES&T-Abstract
  • Other: ES&T-Full Text PDF
  • Supplemental Keywords:

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

    Relevant Websites:


    Progress and Final Reports:

    Original Abstract
    2012 Progress Report
    2014 Progress Report
    2015 Progress Report
    Final Report