Characterization of a New WCPC to Measure Nanometric Carbonaceous Aerosols Sampled from a Sooting Laminar Premixed Flame

FARNAZ KHOSRAVI, Arantzazu Eiguren-Fernandez, Gregory S. Lewis, Michel Attoui, Francesco Carbone, University of Connecticut

     Abstract Number: 49
     Working Group: Instrumentation and Methods

Abstract
One of the major contributors to pollution in urban areas is carbonaceous materials emitted from combustion sources that are known to impact human health and climate change. Consequently, the total mass concentration of particulate matter is stringently regulated but the smallest, most numerous, and likely, most toxic nanoparticles are not controlled by the existing legislation because of the lack of reliable standardized detection approaches. Condensation Particle Counting (CPC) is one of the most attractive technologies for implementing the needed monitoring of the smallest particles in the atmosphere thanks to some distinctive features such as reliability, affordability, and the ability to directly measure the particle number concentrations with a large dynamic range. The water-based MAGIC CPC is a particularly attractive option because of its low usage of a non-toxic odorless condensing fluid and the minimal power consumption but water condensation is known to be influenced by the chemical composition (e.g., hygroscopicity) of the particles and its widespread use requires the characterization of the detection efficiency for the smallest nanoparticles originating from combustion sources. In this study, such efficiency has been characterized by relying on incipient soot particles generated from a laminar premixed flame which are size classified using a Half-Mini Differential Mobility Analyzer (DMA) after being sampled and diluted from the flame. Results show that the MAGIC CPC can be readily operated to activate the condensation growth and detection (with a 50% efficiency) of flame particles at least as small as 3nm. The detection efficiency is slightly sensitive to the polarity of particles classified by the DMA with an enhanced detection of particles with a positive charge. Results also suggest that further improvements in the detection efficiency of the smallest particles are achievable by implementing approaches to reduce particle diffusion losses and increase the supersaturation ratio and available condensation growth time in the MAGIC CPC.