The Use of Black Carbon Sensors to Enhance Particulate Matter Monitoring in Communities

Rebecca A. Sugrue, CHELSEA V. PREBLE, James D.A. Butler, Alaia Redon-Gabel, Pietro Marconi, Karan Shetty, Lee Ann Hill, Audrey Smith, Boris Lukanov, Thomas W. Kirchstetter, UC Berkeley

     Abstract Number: 530
     Working Group: Urban Aerosols

Abstract
Low-cost air pollution sensors are increasingly deployed to understand community exposures and determine local emission sources. Fine particulate matter (PM_2.5) is commonly measured, due in part to the affordability of commercial sensors. However, a significant portion of ambient PM_2.5 may be attributable to pollution sources beyond the community boundaries. This study measured concentrations of PM_2.5 and black carbon (BC), a component of PM_2.5 emitted primarily from diesel engines and biomass burning, using low-cost monitors that employed laser scattering and filter-based absorption photometry methods, respectively. Over four weeks in two seasons, a monitoring network with 50 locations in Richmond, California, was established to evaluate the information gained from measuring both pollutants. Concentrations of BC varied more than PM_2.5 both temporally and spatially. Monthly network-average BC was 3× higher in winter than late spring, while PM_2.5 was instead 10% lower. In both seasons, average PM_2.5 concentrations at two-thirds of sites were within ±10% of the network average, whereas only one-third of sites were within ±10% of the network-average BC concentration. The most and least polluted locations were more persistent across seasons for BC than PM_2.5, and there was little commonality in the sites that experienced the highest concentrations of BC and PM_2.5. While the five most polluted sites in the winter had an average BC concentration 2.2× the average concentration of the five least polluted sites, the temporal dynamics of the BC pollution at each of the sites were similar. Together, these spatiotemporal trends show that BC, a primary aerosol, is a better indicator for local pollution sources than PM_2.5.