Fundamental and Applied Chemistry of Soot Particles from Aviation Fuels
EMSL Project ID
47523
Abstract
Soot is known to affect global climate by altering the earth’s radiative balance directly through absorption of solar radiation, as well as indirectly through contrail and cloud (cirrus and stratus) formation. Moreover, it may alter the atmospheric environment through reacting with a variety of trace gaseous species. Studies have shown that soot produced in aircraft engines is responsible for the light absorbing (black) carbon loading in the upper troposphere and lower stratosphere, altitudes at which indirect effects and heterogeneous processing are important. A key component in assessing soot’s impact on the atmospheric environment is soot’s sizedependent chemistry. Aircraft soot's chemistry, as well as its size dependency, is currently not well known. Moreover, hygroscopic data for aircraft PM is scarce, and more work is required to understand its propensity to act as condensation nuclei in forming clouds. Previous studies have shown that soot from laboratory burners contain PAHs that are harmful for human health. These particles may be inhaled and lodged into tissue, and any hazardous PAHs absorbed onto the particle surface could serve as mutagens and carcinogens. No such data is currently available for aircraft PM. The need for alternative fuels (synthetic) to supplement petroleum–based fuels continues to increase as the amount of air traffic increases and petroleum resources diminish. Current testing addresses only the feasibility (engine performance, production, cost, etc.) of proposed alternative fuels, and does not consider their impact on the environment or human health. Assessing soot’s impact is very important and, thus, imperative in selecting an alternative fuel for aviation. The state-of-the-art analytical tools housed at EMSL are well suited to aid in this assessment by probing the chemistry of soot from an aircraft engine combusting conventional (JP-8) and alternative fuels (e.g., Fischer-Tropsch). Specifically, micro-FTIR spectroscopy will be performed to quantify the concentration of functional groups present in soot, and advanced molecular speciation of those functionalities will be carried out with nano-DESI mass spectrometry. Analyses will be performed to understand the variation in chemistry with fuel characteristics, engine power and particle size. Analyses of high-resolution mass spectrometry results will show the presence of PAHs adsorbed onto soot surface. Previous work performed at EMSL has shown that its surface chemistry may be indicative of its physical structure: the liquid-like behavior of nascent soot is likely due to nonaromatic functionalities present at the particle surface. No experimental evidence has been obtained to date showing a correlation between the particle’s chemistry and physical structure. Particle imaging is needed to observe this correlation and further understand soot, as current models do not account for such chemistry or physical makeup. EMSL is well equipped to perform nanoparticle imaging in order to determine the chemistry–structure relationship. Additional imaging of the samples at various supersaturations in an environmental TEM will be performed to understand its hygroscopic behavior (interfacial phenomenon). Overall, this work will aid in understanding soot at the molecular level, perform advanced chemical characterization of aviation particulates for assessing current and future impacts (environmental and health) of aircraft engines.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2012-10-01
End Date
2013-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members