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Emissions and Radiative Impacts of Sub-10 nm Particles from Biofuel and Fossil Fuel Cookstoves
SHANTANU JATHAR, Naman Sharma, Kelsey Bilsback, Jeffrey R. Pierce, Joonas Vanhanen, Timothy Gordon, John Volckens, Colorado State University
Abstract Number: 219
Working Group: Aerosols, Clouds and Climate
Abstract
Combustion sources have been shown to directly emit particles smaller than 10 nm. The emission of 1-3 nm particles from biofuel or fossil-fuel cookstoves has not been studied previously, nor have the radiative impacts of these emissions been investigated. In this work, emissions (number of particles) were measured during a water boiling test performed on five different cookstoves (three-stone fire, rocket elbow, gasifier, charcoal, and liquefied petroleum gas [LPG]) for particle diameters between ~1 and ~1000 nm. We found significant emissions of particles smaller than 10 nm for all cookstoves (>5×1015 # kg-fuel-1). Furthermore, cleaner (e.g., LPG) cookstoves emitted a larger fraction of sub-10 nm particles (relative to the total particle counts) than traditional cookstoves (e.g., three-stone fire). Simulations performed with the global chemical transport model GEOS-Chem-TOMAS that were informed by emissions data from this work suggested that sub-10 nm particles were unlikely to significantly influence number concentrations of particles with diameters larger than 80 nm that can serve as cloud condensation nuclei (CCN) (<0.3%, globally averaged) or alter the cloud-albedo indirect effect (absolute value <0.005 W m-2, globally averaged). The largest, but still relatively minor, localized changes in CCN-relevant concentrations (<10%) and the cloud-albedo indirect effect (absolute value <0.5 W m-2) were found in large biofuel combustion source regions (e.g., Brazil, Tanzania, Southeast Asia) and in the Southern Ocean. Enhanced coagulation-related losses of these sub-10 nm particles at sub-grid scales will tend to further reduce their impact on particle number concentrations and the aerosol indirect effect, although they might still be of relevance for human health.