10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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High Resolution Chemical Transport Modeling of Ultrafine Particles over Pittsburgh
SHAYAK SENGUPTA, Pablo Garcia, David Patoulias, Provat Saha, Wei Ma, Christopher Tessum, Iannis Kioutsioukis, Sean Qian, Spyros Pandis, Inês Azevedo, Peter Adams, Carnegie Mellon University
Abstract Number: 511 Working Group: Aerosol Modeling
Abstract Ambient ultrafine particles (UFPs), solid or liquid particles in the atmosphere with diameters less than 100 nm, pose poorly understood human health impacts relative to well-understood impacts of PM2.5. Numerous studies have documented health effects related to roadway proximity, with UFP emissions from traffic as a possible culprit. However, high spatial variability and the lack of widespread monitoring complicate exposure quantification of UFPs. The goal of this work is to develop and evaluate high resolution (1 km) chemical transport model (CTM) simulations to quantify UFP concentrations as a step towards quantifying UFP exposure in an urban area. This study uses PM-CAMx-UF to predict UFP concentrations in the Pittsburgh metropolitan area at 1 km spatial resolution for multiple seasons in 2016 and 2017. PM-CAMx-UF is a state-of-the-science CTM which simulates the production and destruction of UFPs in the atmosphere by explicitly tracking both particle number and mass concentrations. Model inputs include traffic emissions at 1 km resolution, spatially resolved using a traffic model for Pittsburgh. Simulations test the CTM’s ability to accurately predict UFP concentrations and understand which sources impact particle number concentrations. Furthermore, we test simulations at 4 km, 12 km and 36 km resolutions to identify and compare the amount of spatial variability in UFP concentrations resolved by the CTM. We evaluate our model predictions with a distributed, intraurban network of observation sites which includes stationary water-based condensation particle counters, scanning mobility particle sizers, and beta attenuation monitors to monitor both particle mass and number concentrations in traffic-heavy and non-traffic-heavy locations. Mobile van sampling throughout Pittsburgh complement stationary observations to evaluate model performance. In addition to showing model performance evaluation, use of model results to predict population exposure will show the impact of model resolution on quantifying UFP and PM2.5 exposure. Any nonzero correlation between predicted total particle number concentration and PM2.5 mass concentration suggests potential exposure confounding in long-term health impact quantifications.