Laboratory Studies of Cloud Particle Formation, Mixing State, Physicochemical and Optical Properties of Carbonaceous Aerosols

Description

Aerosol particles affect climate by changing the earth’s atmospheric radiation balance. These climate effects may be as large as that of the greenhouse gases, but generally opposite in sign and much more uncertain. The high uncertainties are due to the current, inadequate representation of aerosol interactions with solar radiation (direct effect) and clouds (indirect effect). These interactions are complicated because of the constantly evolving chemical composition, morphology, and size of particles throughout their atmospheric lifetimes. Carbonaceous materials, including black carbon (BC), brown carbon (BrC), and secondary organic aerosol (SOA), are found on almost all atmospheric particles and significantly influence particle behavior. However, the effects of these carbonaceous materials on climate are still not well understood. The objective of our laboratory-based studies is to reduce the uncertainties related to the direct and indirect effects of carbonaceous-containing aerosols, with a specific focus on BC, BrC, and SOA. Our laboratory measurements are focused on three primary research objectives: (1) The potential of BC- and SOA-containing particles acting as cloud condensation nuclei (CCN) and ice nuclei (IN), as a function of particle phase and hygroscopicity; (2) Chemical, morphological, and mixing state studies of BC-containing particles and their effects on optical properties; and (3) Optical properties of SOA and BC-containing particles. We will highlight recent work accomplished as part of our DOE ASR funded project, with a focus on three specific topics: (1) the role of particle phase state and molecular solubility on SOA hygroscopicity; (2) the optical properties of laboratory-flame soot, with and without SOA coatings; and (3) insights into the SOA formation mechanisms and phase partitioning from the ozone and OH radical oxidation of α-pinene in a flow reactor as characterized by a recently developed Filter Inlet for Gases and Aerosols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) with acetate reagent ion chemistry.