Laboratory studies of carbonaceous aerosols: characterization and atmospheric processing

 
Poster PDF

Authors

Timothy B Onasch — Aerodyne Research, Inc.
Andrew Thomas Lambe — Aerodyne Research, Inc.
David Croasdale — Boston College
Justin Wright — Boston College
Alex T Martin — Boston College
Paola Massoli — Aerodyne Research, Inc.
Leah R Williams — Aerodyne Research Inc

Charles E. Kolb — Aerodyne Research, Inc.
Paul Davidovits — Boston College

Category

Aerosol Properties

Description

Carbonaceous aerosols, including black carbon and/or organic material derived from energy-related processes, can affect climate by direct or indirect processes. In the direct process, aerosols alter the atmospheric radiation budget by either absorbing or scattering incoming light depending on their composition and morphology. The indirect effects of aerosols occur through changes in cloud properties controlled by the ability of particles to act as cloud condensation nuclei (CCN). The uncertainty in the climatic effects of carbonaceous particles is driven in part by several important factors: poorly understood formation (e.g., secondary organic aerosol (SOA) generation), poorly quantified atmospheric processing (e.g., hydrophobic into hydrophilic), and limited information on the UV-VIS-IR optical properties. These uncertainties are complicated by the lack of measurement techniques that can unambiguously measure (isolate) carbonaceous particles’ properties.

Our current work involves testing and applying new, high-oxidant, wall-less flow tube reactor techniques for generating SOA from the gas-phase oxidation of volatile and intermediate volatility organic compounds and oxidized primary organic aerosol (OPOA) from heterogeneous oxidation of atmospherically relevant primary aerosols by OH radicals. Specifically, we are using a photochemical system originally developed to provide a measure of the “potential aerosol mass” of an airmass (i.e., PAM, developed by Brune et al. at PSU) in the laboratory as a complementary approach to conventional environmental chambers. The resulting particles are characterized using a suite of online particle instruments (including aerosol mass spectrometers, low pressure impactors for particle bounce, and CCN instruments) and offline, filter-based techniques. Our goals are to identify correlations between the chemical, physical, and optical properties of laboratory-generated SOA and OPOA that may help explain field measurements and enable more accurate climate modeling from hours to days of equivalent atmospheric aging. We will present results from our investigations covering a range of atmospherically relevant anthropogenic and biogenic precursors that provide insights into SOA oxidation pathways and that correlate chemical properties of laboratory-generated OPOA and SOA with their corresponding phase state, CCN activity, and optical properties.