Formation of Refractory Black Carbon by SP2-Induced Charring of Organic Aerosol
Abstract
Black carbon (BC) in the atmosphere continues to be a focus of research because its light-absorptive properties put it second only to CO2 as a warming agent of Earth's climate. Towards this end, the measurement of ambient BC has been aided greatly by the development of the Single Particle Soot Photometer (SP2) - an instrument that detects refractory black carbon (rBC) through laser-induced incandescence. Potential interference from other substances that can incandesce under 1064 nm illumination (e.g., some metals and minerals) is mitigated through the use of spectral bandpass filters (color temperature) to ensure that the SP2 remains highly selective to rBC. Here, we report on the detection of rBC that is produced through SP2 laser-induced charring (i.e., carbonization) of organic aerosol particles. Nigrosin, a non-BC-containing material, was used as a surrogate for light absorbing organic aerosol. The imaginary part of the refractive index of nigrosin is sufficiently high that the particles heated rapidly in the SP2, causing charring, and thus allowing the particle to be detected to by the SP2 as rBC. The color temperature of the detected particles originating from charred nigrosin is near that of carbon black, fullerene soot, and ethylene soot, indicating that it is rBC. In a separate set of experiments where fulvic acid and humic acid particles were sent into a denuder prior to SP2 sampling, rBC was detected and exhibited a dependence on laser power, suggesting that the denuder changed the chemical, and thus optical properties of the particles, which were then charred by the SP2. Failure to properly account for this heretofore unidentified source of rBC will lead to an overestimate of rBC loadings, which could, in turn, impact aerosol radiative forcing model predictions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A33L3364S
- Keywords:
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- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE