AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Chemical and Optical Changes to Black Carbon during Aging
ELEANOR BROWNE, Jonathan Franklin, Jesse Kroll, MIT
Abstract Number: 364 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Black carbon (BC) is the second most important contributor to global warming. Due to its short atmospheric lifetime (~days), reductions in BC may be the quickest mechanism to reduce warming. Recent field measurements indicate that BC is a chemically and physically dynamic atmospheric constituent, suggesting that radiative forcing effects of BC may evolve quickly (on the timescale of hours) in the atmosphere. The specifics of how (and even if) the radiative forcing potential of BC changes as it ages, however, is currently under debate, thus leading to significant uncertainties on the magnitude of BC contribution to radiative forcing.
We attempt to help constrain this uncertainty using a series of laboratory measurements that systematically study the aging process of BC. These laboratory measurements are carried out using a photo-oxidation chamber and an extensive suite of measurements including an Aerodyne Soot-Particle Aerosol Mass Spectrometer (SP-AMS) and a Cavity Attenuated Phase Shift – Single Scattering Albedo (CAPS-SSA) instrument. The SP-AMS allows us to quantify and chemically characterize both the BC as well as any coatings present and the CAPS-SSA provides measurements of optical properties. Using this instrument suite, we characterize how the chemical and optical properties of BC change as it is aged heterogeneously (by OH and ozone) and as it is coated by organic material.