Detection and Classification of Super-Micron Urban Aerosols with Open-Path Digital Holography

NICHOLAS GOOD, Matt Freer, Gavin McMeeking, Benjamin Swanson, Matthew Berg, CloudSci LLC

     Abstract Number: 127
     Working Group: Identifying and Addressing Disparate Health and Social Impacts of Exposure to Aerosols and Other Contaminants across Continents, Communities, and Microenvironments

Abstract
Super-micron aerosols are an important component of urban air that have impacts on human health and climate. They vary significantly over space and time, more so than accumulation mode particles, due to their wide range of sources and short atmospheric lifetimes. Urban environments face major challenges in adapting to a changing climate and will require better information regarding sources of air contaminants resulting from greening and electrification efforts, which will likely replace combustion sources over time. There are few instruments suitable for measuring super-micron particle properties such as size, shape, and abundance, rapidly and over the large spatial and temporal scales needed. An additional challenge is the difficulty of sampling large particles through instrument inlets without losses or other measurement artifacts. To meet these needs, we are developing a novel, lower-cost sensor based on digital inline holography. It features an open path design and novel triggering system, eliminating inlet artifacts. We present results from laboratory experiments in a custom-built wind tunnel capable of generating aerosols and propelling them through the holography apparatus at a range of velocities expected in urban environments. The new sensor is evaluated against an aerodynamic particle sizer and microscopy analysis of filter samples. Particles evaluated include glass bead size standards, non-spherical particle standards, common allergens such as pollen and dust mites, and road dust. Initial field measurements in two urban locations are also presented.