| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | January 2, 2018 |
| Latest Amendment Date: | November 1, 2018 |
| Award Number: | 1748080 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Sylvia Edgerton
sedgerto@nsf.gov (703)292-8522 AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | January 15, 2018 |
| End Date: | December 31, 2021 (Estimated) |
| Total Intended Award Amount: | $420,528.00 |
| Total Awarded Amount to Date: | $439,151.00 |
| Funds Obligated to Date: |
FY 2019 = $18,623.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
310 E CAMPUS RD RM 409 ATHENS GA US 30602-1589 (706)542-5939 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
310 East Campus Rd. Athens GA US 30602-1589 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Atmospheric Chemistry |
| Primary Program Source: |
01001920DB NSF RESEARCH & RELATED ACTIVIT 01002021DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Over the past two decades, it has been established that black carbon (BC), also known as soot, is a significant light absorber with a climate-warming effect potentially second only to carbon dioxide. However, the climate forcing effect of BC is subject to large uncertainties, and resolution is crucial for constraining the climate sensitivity of combustion carbon. One of the major contributors to this uncertainty is the limited understanding of light absorption by BrC, which is often co-emitted with BC, thus coupling the effects of the two. This project will promote graduate and undergraduate research by constituting a major component of a PhD dissertation and involving undergraduate students in the project. Third, the project will involve an outreach component through the involvement in workshops led by the UGA College of Education aiming at creating spaces where bilingual (Hispanic) middle- and high-school students, their parents and teachers, and researchers can engage in science-learning (STEM) activities.
BrC light-absorption properties (the most relevant properties for climate calculations) are poorly constrained, with reported values varying over two orders of magnitude. The source of this variability is largely unknown, posing major challenges to representing BrC in climate models. This work will build on advances in BC formation research in the field of combustion science and recent findings by the PI to understand the effects of BrC. The main hypothesis of the project is that a major fraction of BrC is comprised of organic precursors of BC, and that BrC exhibits a continuum of light-absorption properties that can be correlated with molecular mass and volatility.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Light-absorbing organic aerosol, or brown carbon (BrC), plays a significant role in perturbing the radiative balance in the atmosphere. However, BrC exhibits highly variable light-absorption properties. The source of this variability has been largely unknown, hindering accurate representation of BrC in radiative-transfer calculations. This project led to developing the brown-black continuum hypothesis, which elucidates the source of variability of the light-absorption properties of BrC produced in combustion. The brown-black continuum hypothesis states that an important fraction of BrC is formed through the same pathways as black carbon (BC), but at combustion conditions that are not conducive for the full progression of the soot-formation process. This was confirmed by performing novel controlled-combustion experiments. By changing the combustion conditions, the experiments reproduced the spectrum of BrC emitted from real-life uncontrolled combustion. The findings from this project led to establishing a transformative framework that represents BC and BrC on the same optical continuum, which is associated with a continuum of physicochemical properties (molecular sizes, volatility, and solubility). The framework can be used to interpret both laboratory and field measurements, and provides a basis for parameterizing BrC in radiative-transfer calculations, thus enhancing the understanding of the effect of combustion aerosol emissions on the climate system.
The fundamental groundwork laid in this project was employed in two applications. The first application involved investigating aerosol formation under low-temperature combustion conditions that are relevant for next-generation advanced compression ignition (ACI) engines. In concordance with the brown-black continuum hypothesis, results from this project showed that compared to conventional compression-ignition engines, the low-temperature combustion in ACI engines shifts the aerosol emissions profile from BC to BrC. The second application involved categorizing BrC in biomass-burning emissions into weakly-absorbing BrC and strongly-absorbing BrC fractions based on their solubility in methanol.
Three PhD students, six undergraduate students, and one high-school intern gained hands-on experience in conducting the experiments and analyzing the data under this project. Two of the undergraduate students went on to pursue graduate degrees in STEM, and the high-school intern went on to pursue an undergraduate degree in STEM. The project supported the development of material that was incorporated in an undergraduate course on Air Pollution Engineering and a graduate course on Aerosol Science and Engineering, as well as a lesson plan on ?Aerosols and the Environment? for local high schools.
Last Modified: 04/27/2022
Modified by: Rawad Saleh
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