2015 Progress Report: Development of a Quantitative Accounting Framework for Black Carbon and Brown Carbon from Emissions Inventory to Impacts

EPA Grant Number: R835039
Title: Development of a Quantitative Accounting Framework for Black Carbon and Brown Carbon from Emissions Inventory to Impacts
Investigators: Schauer, James J. , Bergin, Michael
Institution: University of Wisconsin - Madison , Georgia Institute of Technology
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, 2014 through September 30,2015
Project Amount: $899,600
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 overall goal of this project is to develop a framework, and the necessary supporting data, to quantitatively account for the contributions of source emissions and atmospheric processing to the radiative absorption by carbonaceous aerosols in the atmosphere. This goal is being accomplished via two integrated approaches: (1) quantification of the relationships of the optical and chemical properties of the major components of light absorbing carbon in the emissions from key air pollution sources, and (2) elucidating how these relationships evolve during atmospheric processing and transport. The project team will integrate expertise in molecular marker source apportionment tools as well as in the measurement of aerosol optical properties that will provide a mechanism to quantitatively determine the source contributions to light absorbing carbon. The work will combine direct measurements of the emissions of dominant light absorbing carbon sources with field measurements in both urban and background locations to understand the influence of sources and atmospheric aging on aerosol light absorption. 

Progress Summary:

The following sections describe the ongoing research activities that have been conducted by the UW-Madison and Georgia Tech. These activities are a continuation of previously reported work summarized in the February 2015 “Black Carbon” EPA grant progress report. The current progress focuses on data analysis and reporting of previous source and ambient sampling with a focus on quantification of organic carbons’ role in multi-wavelength visible light absorption, as well as estimates of the contribution of light absorbing black carbon and organic carbon to radiative forcing in both the south eastern US and northern India. Source sampling black and brown carbon results have been investigated and quantified, and the utilization of PM filter-loading color has been investigated as an indicator of EC/OC composition. Through the coordination with other ongoing projects, ambient and source samples from global locations, including China, India, and California have been analyzed to understand BrC and BC impacts on air quality.     

Specifically, the following research tasks have been conducted: (1) Results from diesel engine testing have been published, assessing the impact of engine condition and after-treatment on the quantification of black carbon emissions and to estimate the brown carbon contribution of diesel engine sources. (2) Source sample investigation results from multiple combustion fuels have been published. These results utilized a test specific correction methodology and segregated the absorption of brown and black carbon from unique fuel type emissions; of particular interest is the reported source specific brown and black carbon absorption cross-section at multiple visible wavelengths. (3) The utilization of a cost-effective color space measurement of PM filter loading has been investigated and a model was developed to estimate both EC and OC filter loading. This method offers the ability to quantify carbonaceous composition at extremely low cost. The research is currently being considered for publication. (4) Ambient samples from urban, rural, and a high-loading biomass influenced regions have been collected and analyzed. (5) Estimates of the relative contributions of black carbon and light absorbing organic carbon have been made. The brown and black carbon fractions are being quantified at multiple wavelengths using Aethalometer data analysis. Also, OC segregation methodologies, including atomization and of solvent extracted component, and UV-Vis Photospectrometry of extracts are being applied to quantify BrC absorption. These results are expected to be submitted for publication in January 2016 (6) Three months of urban China ambient air samples have been collected both under the APEC emission control regimes and without controls. The brown and black carbon fractions have been quantified at multiple wavelengths using Aethalometer methodologies, but also solvent extracted component may be investigated using UV-Vis Photospectrometry. Concentration field analysis (CFA) has been applied to determine source sectors associated with the multiple wavelength absorption measurements made by the Aethalometer and the corresponding filter EC/OC results. Source apportionment techniques (CMB) will be applied to chemical speciation results and optical measurements will be reconstructed using the established source absorption cross-sections.

Below is a brief summary of each major research activity that was conducted as part of the project. 

Color Space EC/OC analysis – Exploiting BrC to Quantify OC

The application of color sensing was used to quantify color coordinates of atmospheric particulate matter collected on filters to quantify elemental and organic carbon (EC/OC) loading. The method used a colorimeter and digital photography to obtain XYZ color space values and mathematically transformed them to HSV cylindrical-coordinates; a quantification method was applied to estimate the NIOSH and IMPROVE (TOR) EC/OC loadings from a set of globally diverse PM samples. The method's low analytical cost makes it a valuable tool for estimating EC/OC exposure in developing regions and for large scale monitoring campaigns. The method was validated using data from the US EPA CSN Network using samples from  LA, Riverside, and Denver.  The ability to apply the PM sample hue and saturation are the basis for estimating the OC loading. 

Water and organic solvent soluble fraction of emission impact on absorption 

Direct measurement of the organic carbon absorption at multiple wavelengths was conducted through the atomization of both water soluble and organic solvent extractions. This allows a direct measurement of the brown carbon component of absorption from sources. Through the application of these methods we can quantify the organic aerosols absorption without interference from black carbon absorption and mixing state artifacts. Utilizing SMPS size distribution data and the scattering coefficients measured during atomization, the wavelength specific refractive index can be calculated using MIE theory. In addition, the extracted organic compounds have been analyzed using UV-Vis photospectrometer to give detailed wavelength absorption spectra of both water soluble and organic solvent soluble components.      

The results show a discrepancy between different BrC methods when the mass absorption cross-sections are reconstructed.   To further investigate the ability of extracted OC to absorb light across multiple wavelengths, a set of sources and ambient samples, including source apportioned samples, were analyzed using a UV-Vis photospectrometer to compare the relative absorption responses when extracted in water, DCM, and methanol solvents. Results from a set of combustion sources were analyzed using the UV-Vis Photospectometer and showed that absorption is dominated by OC extractable by methanol. These results are being compared to the extractable OC content to develop MAC for both sources and ambient samples.

We investigated the MAC absorption spectrum for source samples and the results show good agreement between the two WSOC methods (atomization with AE31 in line and the UV-Vis) for quantifying absorption at 370 nm. However, excess noise in the absorption data for atomized samples is observed due to the AE31 sensitivity to poorly absorbing aerosol. In both cases the MeOH absorption at 370 nm was several times higher than the other methods investigated.

MeOH has been shown to absorb a larger fraction of OC and likely different components of the PM OC. This is valuable in identifying source contribution of BrC. Specifically light absorption coupled with solubility in polar and semi-polar solvents gives understanding to aerosol aging and sources. WSOC absorption was found to be highly variable across samples while the MeOH extractable absorption was more stable. Additionally, if the extreme WSOC absorption measurements are ignored, a trend of decreased absorption efficiency is demonstrated as PM ages for both WSOC and MeOH extracts.  

BC and BrC associated With Sector Analysis

For a 3-month time period associated with the Beijing APEC Conference air pollution control period, daily sampling and Aethalometer data were collected. We examine the time series of BC (Aethalometer 880 nm) and BrC (excess at Aethalometer 370 nm) as a function of controls and meteorology. Results are currently being analyzed linking sector analysis observed BC and BrC concentrations. In addition, CMB source apportionment will be linked to these sectors to further define the PM compositions and sources to observed optical properties. 

The light absorbing nature of trash and refuse burning in India

Roadside trash burning is largely unexamined as a factor that influences air quality, radiative forcing, and human health even though it is ubiquitously practiced across many global regions, including throughout India. With this in mind, we conducted field measurements in India during October 2013 collecting filters in Bangalore, India. Our overall objective was to examine characteristics and redox activity of fine particulate matter (PM2.5) associated with roadside trash burning. Emissions from smoldering and flaming roadside trash piles (n = 24) were analyzed for organic and elemental carbon (OC/EC), brown carbon (BrC), and toxicity (i.e. redox activity, measured via the DTT assay). A subset of samples (n = 8) were further assessed for toxicity by a biological assay (macrophage assay) and also analyzed for trace organic compounds. Results show high variability of chemical composition and toxicity between trash-burning emissions, and characteristic differences from ambient samples. OC/EC ratios for trash-burning emissions range from 0.8 to 1500, while ambient OC/EC ratios were observed at 5.4 ± 1.8. Interestingly, results suggest that on a per-mass basis, fresh trash-burning emissions are less redox-active than ambient air (13.4 ± 14.8 pmol/min/μgOC in trash burning, 107.1 ± 25.0 pmol/min/μgOC for ambient). Overall results indicate that as trash-burning emissions age, they become less brown.

Light absorption by BC and BrC over the Indo-Gangetic plain and radiative impacts

The Indo-Gangetic Plain (IGP) is a region of known high aerosol loading with substantial amounts of carbonaceous aerosols from a variety of sources, often dominated by biomass burning. Although black carbon (BC) has been shown to play an important role in the absorption of solar energy and hence direct radiative forcing (DRF), little is known regarding the influence of light absorbing brown carbon (BrC) on the radiative balance in the region. With this in we made measurements over a one month period during the winter-spring season of 2013 in Kanpur, India that measured aerosol chemical and physical properties that were used to estimate the sources of carbonaceous aerosols, as well as parameters necessary to estimate direct forcing by aerosols and the contribution of BrC absorption to the atmospheric energy balance. A Positive matrix factorization analyses, based on aerosol mass spectrometer measurements, resolved organic carbon into four factors including low-volatile oxygenated organic aerosols (LV-OOA), semi-volatile oxygenated organic aerosols (SV-OOA), biomass burning (BBOA) and hydrocarbon like (HOA) organic aerosols. Three-wavelength absorption and scattering coefficient measurements from a Photo Acoustic Soot Spectrometer (PASS-3) were used to estimate aerosol optical properties and estimate the relative contribution of BrC to atmospheric absorption. Mean ± standard deviation values of short-wave cloud free clear sky DRF exerted by total aerosols at the top of atmosphere, surface and within the atmospheric column are -6.1±3.2, -31.6±11 and 25.5±10.2 W/m2, respectively. During days dominated by biomass burning the absorption of solar energy by aerosols within the atmosphere increased by ~35%, accompanied by a 25% increase in negative surface DRF. DRF at the top of atmosphere during biomass burning days decreased in negative magnitude by several W/m2 due to enhanced atmospheric absorption by biomass aerosols, including BrC. The contribution of BrC to atmospheric absorption is estimated to range from on average 2.6 W/m2 for typical ambient conditions to 3.6 W/m2 during biomass burning days. This suggests that BrC accounts for 10-15% of the total aerosol absorption in the atmosphere, indicating that BrC likely plays an important role in surface and boundary temperature as well as climate.

Future Activities:

The bulk of the sampling and experimental procedures has been completed. Select chemical analysis will occur during January 2016, and finalization of remaining manuscripts will occur in the spring of 2016.  

The primary thrust of work activities is the completion of manuscripts for publication. 

Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other project views: All 12 publications 11 publications in selected types All 11 journal articles
Type Citation Project Document Sources
Journal Article Liu J, Scheuer E, Dibb J, Diskin GS, Ziemba LD, Thornhill KL, Anderson BE, Wisthaler A, Mikoviny T, Devi JJ, Bergin M, Perring AE, Markovic MZ, Schwarz JP, Campuzano-Jost P, Day DA, Jimenez JL, Weber RJ. Brown carbon aerosol in the North American continental troposphere: sources, abundance, and radiative forcing. Atmospheric Chemistry and Physics 2015;15(14):7841-7858. R835039 (2015)
R835039 (Final)
  • Full-text: ACP-Full Text PDF
  • Abstract: ACP-Abstract
  • Other: NASA-Abstract & Citation
  • Journal Article Olson MR, Garcia MV, Robinson MA, Van Rooy P, Dietenberger MA, Bergin M, Schauer JJ. Investigation of black and brown carbon multiple-wavelength-dependent light absorption from biomass and fossil fuel combustion source emissions. Journal of Geophysical Research: Atmospheres 2015;120(13):6682-6697. R835039 (2014)
    R835039 (2015)
    R835039 (Final)
  • Full-text: U.S. Forest Service-Full Text PDF
  • Abstract: Wiley Online-Abstract
  • Other: Wiley Online-Full Text PDF
  • Journal Article Robinson MA, Olson MR, Liu ZG, Schauer JJ. The effects of emission control strategies on light-absorbing carbon emissions from a modern heavy-duty diesel engine. Journal of the Air & Waste Management Association 2015;65(6):759-766. R835039 (2014)
    R835039 (2015)
    R835039 (Final)
  • Abstract from PubMed
  • Full-text: Taylor & Francis-Full Text HTML
  • Abstract: Taylor & Francis-Abstract
  • Other: Taylor & Francis-Full Text PDF
  • Journal Article Shamjad PM, Tripathi SN, Pathak R, Hallquist M, Arola A, Bergin MH. Contribution of brown carbon to direct radiative forcing over the Indo-Gangetic Plain. Environmental Science & Technology 2015;49(17):10474-10481. R835039 (2015)
    R835039 (Final)
    R835035 (Final)
  • Abstract from PubMed
  • Full-text: ES&T-Full Text PDF
  • Abstract: ES&T-Abstract
  • Other: ResearchGate-Abstract & Full Text PDF
  • Supplemental Keywords:

    Elemental carbon, EC, BC, brown carbon 

    Progress and Final Reports:

    Original Abstract
    2012 Progress Report
    2013 Progress Report
    2014 Progress Report
    Final Report