AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
High Temporal and Spatial Variability in Ambient Black Carbon in an Urban Area from Fixed-Site and Mobile Monitoring
AJA ELLIS, Naomi Zimmerman, Hugh Li, Peishi Gu, Ellis Shipley Robinson, Allen Robinson, Joshua Apte, Albert A. Presto, R. Subramanian, Carnegie Mellon University
Abstract Number: 655 Working Group: Urban Aerosols
Abstract Black carbon (BC) is used as an air quality indicator for exposure to combustion-related primary particles, especially diesel exhaust particulate matter (DEPM), a known carcinogen. Fixed-site BC observations are often limited by low spatial and/or temporal resolution, and may not adequately represent population exposure by highly localized combustion sources. To better characterize spatial and temporal gradients in the urban environment, concurrent BC measurements were made across a rural-urban transect and a downtown area over a year-long period in Pittsburgh, PA. Mobile BC measurements were also made to increase the spatial resolution. Sites included a range of traffic, tall building, and restaurant densities, along with upwind and downwind urban background sites. Ambient BC was monitored using an array of instruments including a Magee Scientific Aethalometer, MetOne BC-1050, and multi-angle absorption photometers (MAAP), along with collocated measurements of ultrafine particle number, PM2.5, carbon dioxide (CO2), carbon monoxide (CO), nitrogen dioxide (NO2), and ozone (O3). The high spatial and temporal resolution measurements will be jointly analyzed with the collocated gaseous and aerosol measurements as well as mobile laboratory BC measurements to investigate the sources of and population exposure to BC across Pittsburgh. There are consistent diurnal trends with daytime peaks in BC across the city and substantial decreases in BC over weekends, particularly in downtown sites. Urban background BC increases across all monitors during atmospheric stagnation events. Two sites in downtown Pittsburgh revealed steep gradients in BC concentrations over short distances (~0.3 km) due to the urban street canyon effect. One downtown green space measured daily weekday concentrations over 2 μg m-3 and short duration (~30-min) events often topping 20 μg m-3, likely driven by nearby diesel bus traffic.