Abstract View
Optical and Microphysical Properties of Aerosols Emitted from a Marine Engine
NILOFAR RAEOFY, Justin Dingle, Roya Bahreini, Andrew Metcalf, Gavin McMeeking, Tony Hansen, Yu Jiang, Jiacheng Yang, Kevin Thomson, Stephanie Gagne, Tak Chan, Jacob Swanson, Heejung Jung, Georgios Karavalakis, David R. Cocker III, Thomas D. Durbin, Wayne Miller, Kent Johnson, University of California, Riverside
Abstract Number: 622
Working Group: Aerosol Physics
Abstract
Black Carbon (BC) emissions from ships have important implications on air quality, climate, and health. A study of aerosol emissions was carried out on a 2-stroke marine engine operated at 25%, 50%, and 75% load with three different fuels including distillate marine (DMA), low-sulfur residual marine (RMB-30) and high-sulfur residual marine (RMG-380). Aerosol emissions in the exhaust were sampled unconditioned or through a catalytic stripper/sulfur adsorber and analyzed by several instruments. In this analysis, we focus on the measurements related to optical and microphysical properties of the aerosols to gain insight on the emissions of climate-relevant components, namely BC and brown carbon (BrC). BrC are light-absorbing organic aerosols that exhibit a strong absorption wavelength dependence, increasing towards the shorter visible and ultraviolet (UV) wavelengths. A photoacoustic extinctiometer and an aethalometer were used to calculate single scattering albedo (SSA, λ=375 nm) and wavelength dependence of absorption (Absorption Ångström Exponent, AAE, λ=370 and λ=880 nm). The SSA values of unconditioned aerosols at 25% load were similar for all fuel types at ~0.23-0.33 while they all decreased to ~0.13 at 75% load, suggesting a higher contribution of strongly absorbing aerosols at the higher engine load. AAE values of the unconditioned aerosols for RMG-380, RMB-30, and DMA at 25% loads were 1.5-1.9, 0.7-0.9, and ~1, respectively. Different values of AAE suggest different types of aerosols were generated depending on the fuel, with the highest proportion of BC suspected to have been generated using the DMA fuel. The AAE values for all fuels also decreased in going from 25% to 75% load. A single-particle soot photometer (SP2) was used for measuring BC size distributions and microphysical properties. Data based on its color ratio and mixing state will be used to differentiate the nature of BC aerosols during the different runs and sampling conditions.