Grantee Research Project Results
2013 Progress Report: Black Carbon, Air Quality and Climate: From the Local to the Global Scale
EPA Grant Number: R835035Title: Black Carbon, Air Quality and Climate: From the Local to the Global Scale
Investigators: Pandis, Spyros N. , Robinson, Allen , Donahue, Neil , Adams, Peter
Institution: Carnegie Mellon University
EPA Project Officer: Chung, Serena
Project Period: September 1, 2011 through August 31, 2014
Project Period Covered by this Report: September 1, 2012 through August 31,2013
Project Amount: $900,000
RFA: Black Carbon's Role In Global To Local Scale Climate And Air Quality (2010) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Climate Change , Air
Objective:
Reduction of black carbon (BC) emissions represents a potential win-win strategy in our effort to improve air quality while limiting climate change. However, the magnitude of the benefits remains quite uncertain because of our limited understanding of the contributions of the various source sectors to the BC mass and number concentrations, the atmospheric processing of black carbon particles including their physical and chemical changes, the role of other absorbing organics (brown carbon), the contributions of the various source sectors (and long range transport) to the direct and indirect effects of BC on climate, and the effect of BC on local and regional meteorology. Control strategies resulting in changes to BC emissions often will result in changes to emissions of various co-pollutants (primary and secondary organic aerosol, sulfur, particle number concentration) and may have significant effects on the aerosol and cloud droplet number concentrations. Reduction of the above uncertainties and quantification of the effects of the various BC control strategies on both air quality and climate change in the United States are the main objectives of the proposed study.
Progress Summary:
Experiments were conducted to investigate light absorption of organic aerosol (OA) in fresh and photochemically aged biomass-burning emissions. The experiments considered residential hardwood fuel (oak) and fuels commonly consumed in wild-land and prescribed fires in the United States (pocosin pine and gallberry). Photochemical aging was performed in an environmental chamber. We constrained the effective light-absorption properties of the OA using conservative limiting assumptions, and found that both primary organic aerosol (POA) in the fresh emissions and secondary organic aerosol (SOA) produced by photo-chemical aging contain brown carbon and absorb light to a significant extent. This work presents the first direct evidence that SOA produced in aged biomass-burning emissions is absorptive. For the investigated fuels, SOA is less absorptive than POA in the long visible, but exhibits stronger wavelength-dependence and is more absorptive in the short visible and near-UV. Light absorption by SOA in biomass burning emissions might be an important contributor to the global radiative forcing budget.
We have used the new source-resolved number emissions inventory developed in the project to gain insights about the sources of particle number during the summer in the Eastern United States. In the Eastern U.S. domain, nucleation is predicted to form the majority of ultrafine particles (75%), while the other 25 percent is due to primary emissions. Gasoline automobiles are responsible for 40 percent of the ultrafine particle emissions, followed by 33 percent from industrial sources, 16 percent from non-road diesel, and 11 percent from on-road diesel for the summertime period studied. For the ambient primary particle concentrations the contributions are: gasoline 31 percent, industrial sources 25 percent, long range transport 18 percent, non-road diesel 14 percent, and on-road diesel 8 percent. The importance of primary particles and hence black carbon emissions increases as the particle size increases. For particles larger than 100 nm, the primary particles are responsible for around 80 percent of the particle number. These results are consistent with the observation-based source apportionment of particle number during the Pittsburgh Air Quality Study (PAQS) for Pittsburgh and indicate that BC containing particles are a small fraction of total particle number during photochemically active periods but are quite important for Cloud Condensation Nuclei size particles.
We have developed a novel approach for using long-term size distribution observations to evaluate an aerosol model’s ability to predict formation rates of CCN from nucleation and growth events. We derived from observations at several locations nucleation-relevant metrics such as nucleation rate of particles at a diameter of 3 nm, diameter growth rate, particle survival probability, condensation and coagulation sinks, and CCN formation rate. These quantities also were derived for a global microphysical model, GEOS-Chem-TOMAS, and were compared to the observations on a daily basis. Using GEOS-Chem-TOMAS, we simulated nucleation events predicted by ternary or activation nucleation over 1 year and found that the model slightly understated the observed annual average CCN formation mostly due to bias in the nucleation rate predictions, but by no more than 4 in 50 percent in the ternary simulations. Model-predicted annual average growth rates were within 25 percent across all sites but also show a slight tendency to underestimate the observations, at least in the ternary nucleation simulations. These results add support to the use of global models as tools assessing the contributions of primary sources and microphysical processes such as nucleation to the total number and CCN budget.
We have investigated the effect of climate change on BC concentrations in the Eastern United States assuming constant emissions but a changing climate. We used the coupled global-regional atmospheric chemistry and climate modeling system GRE-CAPS to compare current (2000s) BC concentration fields with those predicted for the 2050s. The effect of this predicted to be quite variable in space with decreases in the northeast and increases in the south. GRE-CAPS predicts that precipitation changes will dominate the overall change with changes in wind speed and mixing heights also contributing to this complex picture. While the average changes will be modest, the local changes can be quite significant.
Future Activities:
During the third year of the project, we will:
- Perform additional experiments aging primary emissions using OH radicals.
- Finalize the development and evaluation of BC number and mass inventories.
- Quantify the contributions of the different BC source sectors (including long-range transport) to BC mass and number concentrations.
- Investigate the effectiveness of different control strategies.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
| Other project views: | All 25 publications | 11 publications in selected types | All 11 journal articles |
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Day MC, Pandis SN. Effects of a changing climate on summertime fine particulate matter levels in the eastern U.S. Journal of Geophysical Research: Atmospheres 2015;120(11):5706-5720. |
R835035 (2013) R835035 (Final) R833374 (Final) |
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Posner LN, Pandis SN. Sources of ultrafine particles in the Eastern United States. Atmospheric Environment 2015;111:103-112. |
R835035 (2013) R835035 (Final) R833374 (Final) R835405 (2014) R835405 (Final) |
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Saleh R, Hennigan CJ, McMeeking GR, Chuang WK, Robinson ES, Coe H, Donahue NM, Robinson AL. Absorptivity of brown carbon in fresh and photo-chemically aged biomass-burning emissions. Atmospheric Chemistry and Physics 2013;13(15):7683-7693. |
R835035 (2013) R835035 (Final) R833747 (Final) |
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Westervelt DM, Pierce JR, Riipinen I, Trivitayanurak W, Hamed A, Kulmala M, Laaksonen A, Decesari S, Adams PJ. Formation and growth of nucleated particles into cloud condensation nuclei: model-measurement comparison. Atmospheric Chemistry and Physics 2013;13(15):7645-7663. |
R835035 (2013) R835035 (Final) R833374 (Final) |
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Supplemental Keywords:
Air quality modeling, smog, particulate matter, PM, general circulation modelProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.