Final 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 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

Objective:

The overall goal of the 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 integrated expertise in molecular marker source apportionment and the measurement of aerosol optical properties to quantitatively determine the source contributions to light-absorbing carbon (LAC). The work combined direct measurements of the emissions of dominant LAC sources and field measurements in a variety of urban and background locations to understand the influence of sources and atmospheric aging on aerosol light absorption.

Summary/Accomplishments (Outputs/Outcomes):

The following sections describe the research activities that were conducted by the University of Wisconsin–Madison, the Georgia Institute of Technology and Duke University. The report summarizes the major activities and accomplishments that occurred over the research period. The project summary focuses on the effect aerosols from sources and ambient locations have on multiwavelength visible light absorption, investigating the contribution of light-absorbing black carbon (BC) and organic carbon (OC) diverse regions, including the southeastern United States, California, India and China. Source sampling BC and brown carbon (BrC) results have been investigated and quantified, and the utilization of particulate matter (PM) filter-loading color has been investigated as an indicator of elemental carbon (EC) and OC composition. PM source contributions have been investigated using a combination of molecular marker chemical mass balance and positive matrix factorization model (CMB and PMF) results and linked to meteorological trajectory analysis to assess the variability of optical properties due to sources and transport mechanisms. Samples have been analyzed from a diverse range of global locations, which represent unique BC and BrC composition.

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 BC emissions and to estimate the BrC contribution of diesel engine sources. (2) Source sample investigation of BC and BrC from multiple combustion fuels have been published. These results utilized a test-specific correction methodology and segregated the absorption of BrC and BC from unique fuel type emissions; of particular interest is the reported source-specific BrC and BC 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. Results have been published, and the method is being applied globally by other research groups. (4) Ambient samples from urban and rural regions, as well as a high-loading-biomass-influenced region, have been collected and analyzed in conjunction with source apportionment and meteorological trajectories. The results of BC analysis of sources and regional contributions in Beijing, China, have been published. The BrC component of this research will be submitted for publication by January 2017. This work corresponded with 3 months of air samples collected under the Asia Pacific Economic Cooperation (APEC) meeting emission control and non-control regimes. The BrC and BC fractions have been quantified at multiple wavelengths using Aethalometer methodologies. (5) Through the application OC segregation methodologies, including atomization and of solvent extracted components and UV-Vis photospectrometry of extracts, have been being applied to source and ambient samples to quantify soluble fraction BrC absorption. These results have been compared to BrC reflection properties utilizing colorimetry to understand the visible spectrum absorption and reflective properties of PM to quantify the variability of BrC from sources and atmospheric aging. These results are expected to be submitted for publication in February 2017. (6) Unique sources samples of uncontrolled waste combustions have been analyzed to understand the BC and BrC components of the PM emission in India. In addition, sampling was conducted at a variety of locations in India to determine the sources of light-absorbing PM and their influence on the discoloration of the Taj Mahal. The research has been published. (7) The optical properties of size-segregated PM from a rural southeastern region of the United States have been invested, focusing on the impacts secondary organic aerosols (SOA) have on aerosol optical properties. This research has been published.

Diesel Engine Emissions

To better identify the role of modern heavy-duty diesel engines on the production of BC and BrC, emissions from a heavy-duty diesel engine operating with different emission control strategies were examined using a source dilution sampling system. The effect of control technology on LAC was evaluated at different engine operation modes. EC and BC emission rates normalized to the mass of CO2 emitted increased with increasing engine speed and load. Emission rates normalized to brake-specific work did not exhibit similar trends with speed and load, but rather the highest emission rate was measured at idle. EC and OC emissions were reduced by 99 percent when the diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) architecture was applied. The application of a DPF was equally effective at removing 99 percent of the BC fraction of PM, proving to be an important control strategy for both LAC and PM. BC emissions were unexpectedly increased across the DOC, seemingly due to a change in aerosol optical properties. Removal of exhaust gas recirculation (EGR) flow due to simulated EGR cooler failure caused a large increase in OC and BrC emission rates at idle but had limited influence during high-load operation. LAC emissions proved to be sensitive to the same control strategies effective at controlling the total mass of diesel PM. Additionally, optical monitoring techniques were investigated. The results showed excellent correlation (R2 = 0.95) between aerosol light absorption at the short infrared (IR) wavelength with EC concentration from a thermal optical reflectance, National Institute for Occupational Safety and Health (NIOSH) 5040 method. Resulting EC mass absorption cross-section (MAC) efficiencies differed by 25–30 percent from manufacturer-published values.

BC and BrC From Multiple Combustion Fuels

Multiple wavelength absorption was measured from fuels, including wood, agricultural biomass, coals, plant-matter and petroleum distillates, in controlled-combustion settings. Filter-based absorption measurements were corrected and compared to photo-acoustic absorption results. BC absorption was segregated from the total light extinction to estimate the BrC absorption from individual sources. Results were compared to EC/OC concentrations to determine composition’s impact on light absorption. Multiple wavelength absorption coefficients, Angstrom Exponent (6.9 to < 1.0), MAC and Delta-C (97 ug m-3 to ~ 0 ug m-3) were highly variable. Sources such as incense and peat emissions showed ultraviolet wavelength (370 nm) BrC absorption over 175 and 80 times (respectively) the BC absorption, but only 21 and 11 times (respectively) at 520 nm wavelength. The bulk EC MACEC, λ (Ave. at 520 nm = 9.0 ±3.7 m2g-1; with OC fraction < 0.85 = ~7.5 m2g-1) and the BrC OC MACs (MACBrC,OC,λ) were calculated and at 370 nm ultraviolet wavelengths, the MACBrC,OC,λ ranged from 0.8 m2g-1 to 2.29 m2g-1 (lowest peat, highest kerosene), while at 520 nm wavelength MACBrC,OC,λ ranged from 0.07 m2g-1 to 0.37 m2g-1 (lowest peat, highest kerosene/incense mixture). These MAC results show OC content can be an important contributor to light absorption when present in significant quantities (> 0.9 OC/TC), source emissions have variable absorption spectra and non-biomass combustion sources can be significant contributors to BrC.

Color Space EC/OC Analysis

A fast and cost-effective application of color sensing was used to quantify color coordinates of atmospheric PM collected on filters to quantify EC/OC loading. The unique method used a colorimeter and digital photography to obtain XYZ color space values and mathematically transformed them to Hue, Saturation, Value (HSV) cylindrical-coordinates; a quantification method was applied to estimate the NIOSH and Interagency Monitoring of Protected Visual Environments thermal optical reflectance (IMPROVE (TOR)) EC/OC loadings from a set of globally diverse PM samples. When applied to 315 samples collected at three U.S. Environmental Protection Agency Chemical Speciation Network sampling sites, the HSV model proved to be a robust method for EC measurement with an R2 = 0.917 for predicted versus measured loading results and a coefficient of variation of the root-mean square error (CV(RMSE)) = 16.1 percent. The OC quantified from the same sample filters had an R2 = 0.671 and a CV(RMSE) = 24.8 percent between the predicted and measured results. The method was applied to NIOSH EC/OC results from a set of samples from rural China, Baghdad and the San Joaquin Valley, California, and the EC and OC CV(RMSE) was 30.8 percent and 49.3 percent, respectively. Additionally, the method was applied to samples with color quantified by a digital photographic image (DPI) with EC results showing good agreement with a CV(RMSE) of 22.6 percent. OC concentrations were not captured as accurately with the DPI method, with a CV(RMSE) of 77.5 percent. 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.

Ambient Source Apportionment Coupled With Meteorological Trajectory

The APEC Conference was held near Yanqi Lake, Huairou, in Beijing, China, November 10–11, 2014. Associated with the conference period, Beijing and surrounding provinces implemented a series of emission controls. Three months of Aethalometer 880 nm BC measurements were examined to understand the hourly fluctuations in BC concentrations that resulted from emission controls and meteorology changes. Measurements were collected at two locations in the Beijing region. Six cluster groups were identified through analysis of backward trajectories based on air mass transport from various areas, such as Inner Mongolia, Russia, three provinces in the northeast and Hebei industrial areas, to the measurement sites. Air pollution control measures during the APEC Conference significantly reduced BC at the conference site (Huairou) and in Central Beijing, with greater reductions in BC concentrations at the conference site than in Central Beijing. The highest BC concentrations in Huairou were associated with air masses originating from Central Beijing rather than from the Hebei industrial region. The success of the control measures implemented in Beijing and the surrounding regions demonstrates that BC concentrations can be effectively reduced to protect human health and mitigate regional climate forcing. This study also demonstrates the need for regional strategies to reduce BC concentrations.

BrC data were collected using an Aethalometer during the APEC meeting and during the heating season in Beijing, similar to the BC data; the measured results were interpreted based on six geographical clusters, derived using meteorological data residence time analysis. Absorption coefficients were calculated and converted to LAC mass estimates using previously reported MAC. On average, the controls enacted during the APEC meeting reduced both BC and BrC by factors of three to four times. BC and BrC averaged around 1 ugm-3 and 3 ugm-3, respectively, during the control period, while BC and BrC exceeded 6 and 25 ugm-3, respectively, during the heating period following the APEC meeting. During the heating period, all cluster directions showed high levels of LAC; however, the highly populated regions south and east of Beijing were the dominant contributors to regional BC and BrC during extreme air pollution events.

Water and Organic Solvent Soluble Fraction of Emission Impact on Absorption

OC was extracted with water, methanol and dichloromethane from solid fuel source combustion emissions and ambient PM from Atlanta, Georgia, and Los Angeles, California. The multiple-wavelength absorption spectrum was quantified using three methods: (1) the Aethalometer difference method, (2) atomization and Aethalometer measurement of extractable components, and (3) UV-Vis photospectrometry of extracts. The results showed good agreement across methods; however, notable differences were identified, which could be applied for better understanding of source origin and for climate model calculations. All source samples exhibited greater absorption in the UV and near-UV with MeOH extracted BrC as compared to water and dichloromethane (DCM) extracts. Source sample emissions extracted by methanol had absorption coefficients (UV-Vis method) approximately three to five times larger than water extracts, and at 370 nm methanol extracts could exceed 20 times greater absorption. The MACs were calculated and ranged from 2.4–3.7 m2g-1 for methanol at 370 nm, while water extracts were more variable with a MAC370 range from 0.4–3.8 m2g-1. Both water and methanol MACs decreased rapidly with increased wavelength and exhibited a MAC Angstrom exponent between 4.9 and 6.8 for methanol extracts and 1.4 to 6.2 for water-extractable BrC. For ambient samples, the dominant BrC extraction varied between water and methanol. In most samples, the methanol- and water-extractable BrC absorbed light to a similar degree, and the methanol-extractable BrC demonstrated slightly greater absorption than water-extractable BrC. However, under specific source influences, the water-soluble BrC can dominate absorption. Additionally, fresh emissions showed greater MACs for both water- and methanol-extractable BrC as compared to aged ambient PM. The results indicate that coupling light absorption with solubility gives increased understanding of source composition and PM age.

Sources and Light-Absorbing Properties of PM in India: Focus on Trash/Refuse Burning

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. 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 OC/EC, BrC, and toxicity (i.e., redox activity, measured via the Dithiothreitol (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, as well as characteristic differences from ambient samples. OC/EC ratios for trash-burning emissions range from 0.8 to 1,500, 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 (i.e., the carbonaceous fraction that is BrC decreases) and more toxic.

Light Absorption by BC and BrC Over the Indo-Gangetic Plain and Radiative Impacts

The Indo-Gangetic Plain 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 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 BrC on the radiative balance in the region. With this in mind, we made measurements over a 1-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 analysis, based on aerosol mass spectrometer measurements, resolved organic carbon into four factors, including low-volatile oxygenated organic aerosols, semi-volatile oxygenated organic aerosols, biomass burning organic aerosols and hydrocarbon-like organic aerosols. Three-wavelength absorption and scattering coefficient measurements from a Photo Acoustic Soot Spectrometer 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 percent, accompanied by a 25 percent 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 percent 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.

SOA Optical Properties in the Southeastern United States

Measurements of wavelength-dependent aerosol light absorption coefficients were carried out as part of the Southern Oxidant and Aerosol Study during summer 2013 to determine the contribution of light-absorbing organic carbon to total aerosol light absorption in a rural location (Centreville, Alabama) and an urban area (Atlanta, Georgia). The light-absorption coefficients in the near-UV and visible wavelengths were measured for ambient air, thermal denuder (200 °C) amended PM for the removal of semivolatile organic compounds. Atlanta measurements show dominance of semivolatile BrC with an average absorption angstrom exponent (AAE) of 1.4 before heating and about 1.0 after heating. In urban Atlanta, a decrease of about 35 percent in the light-absorption coefficient at 370 nm after heating indicates that light-absorbing organic compounds are a substantial fraction of the light-absorption budget. Furthermore, a considerable increase in the fraction of light absorption by the semivolatile aerosol occurs during the daytime, likely linked with photochemistry. Measurements at rural Centerville, on the other hand, do not show any major change in AAE with values before and after heating of 0.99 and 0.98, respectively. Overall, the results suggest that photochemical aged urban emissions result in the presence of light-absorbing BrC, while at rural locations, which are dominated by aged aerosol and local biogenic emissions (based on measurements of Angstrom exponents), BrC does not significantly contribute to light absorption.

Conclusions:

All project work is complete. Several remaining manuscripts are in the process of being finalized.


Journal Articles on this Report : 11 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 Bergin MH, Tripathi SN, Jai Devi J, Gupta T, Mckenzie M, Rana KS, Shafer MM, Villalobos AM, Schauer JJ. The discoloration of the Taj Mahal due to particulate carbon and dust deposition. Environmental Science & Technology 2015;49(2):808-812. R835039 (Final)
R834799 (2015)
R834799 (2016)
R834799 (Final)
R834799C002 (2015)
R834799C002 (Final)
  • Abstract from PubMed
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  • Abstract: ES&T-Abstract
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  • Journal Article Devi JJ, Bergin MH, Mckenzie M, Schauer JJ, Weber RJ. Contribution of particulate brown carbon to light absorption in the rural and urban Southeast US. Atmospheric Environment 2016;136:95-104. R835039 (Final)
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  • Journal Article Liu J, Scheuer E, Dibb J, Ziemba LD, Thornhill KL, Anderson BE, Wisthaler A, Mikoviny T, Devi JJ, Bergin M, Weber RJ. Brown carbon in the continental troposphere. Geophysical Research Letters 2014;41(6):2191-2195. R835039 (Final)
    R834799 (2014)
    R834799 (2015)
    R834799 (2016)
    R834799 (Final)
    R834799C001 (2014)
    R834799C001 (2015)
    R834799C001 (Final)
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  • 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)
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  • 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)
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  • Abstract: Wiley Online-Abstract
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  • Journal Article Olson MR, Graham E, Hamad S, Uchupalanun P, Ramanathan N, Schauer JJ. Quantification of elemental and organic carbon in atmospheric particulate matter using color space sensing—hue, saturation, and value (HSV) coordinates. Science of the Total Environment 2016;548-549:252-259. R835039 (Final)
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  • 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
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  • Abstract: Taylor & Francis-Abstract
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  • Journal Article Robinson M, Liu Z, Olson M, Schauer J. Comparison of measurement strategies for light absorbing aerosols from modern diesel engines. SAE International Journal of Fuels and Lubricants 2014;7(2):543-550. R835039 (2014)
    R835039 (Final)
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  • 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
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  • Journal Article Vreeland H, Schauer JJ, Russell AG, Marshall JD, Fushimi A, Jain G, Sethuraman K, Verma V, Tripathi SN, Bergin MH. Chemical characterization and toxicity of particulate matter from roadside trash combustion in urban India. Atmospheric Environment 2016;147:22-30. R835039 (Final)
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  • Abstract: ScienceDirect-Abstract
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  • Journal Article Wang Y, de Foy B, Schauer JJ, Olson MR, Zhang Y, Li Z, Zhang Y. Impacts of regional transport on black carbon in Huairou, Beijing, China. Environmental Pollution 2017;221:75-84. R835039 (Final)
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  • Supplemental Keywords:

    Elemental carbon, EC, BC, BrC, brown carbon, black carbon, emissions

    Progress and Final Reports:

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