10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Quantifying High-resolution Spatial Variations and Local Source Impacts of Urban Ultrafine Particle Exposure
PROVAT SAHA, Naomi Zimmerman, Luke Snell, Joshua Apte, Allen Robinson, Albert A. Presto, Carnegie Mellon University
Abstract Number: 1357 Working Group: Aerosol Exposure
Abstract To quantify the fine-scale spatial variations and local source impacts of urban ultrafine particles (UFP) exposure, we conducted systematic measurements of the concentration of UFP at thirty (30) sites in Pittsburgh, Pennsylvania. Sites were selected to span a range of urban land use attributes, including urban background, near-local and arterial roads, traffic-intersections, near-highway, urban street canyon, and restaurant density. 3-6 weeks of continuous measurements of particle number concentration were collected at each site using a rotating network of condensation particle counters (CPC). Other measurements included PM2.5, NO2, CO, O3, SO2, CO2, temperature and RH at each site.
Spatial variations in urban UFP concentrations varied by about a factor of three. Background and nucleating particle concentrations are relatively uniformly distributed while spatial variations are driven by local sources. Traffic is an important contributor to local spatial variations. Near arterial roads UFP concentrations are ~2 times than the regional background; in the urban street canyon and near-highway UFP concentrations are ~3 times higher. Other sources, such as restaurants and cooking emissions, are also important in certain micro-environments.
There are substantial diurnal and weekday/weekend variations in urban UFP concentrations. On a relative basis, there is stronger rush-hours traffic influence at high traffic sites compared to background sites, indicating the spatial pattern of UFP concentrations evolves over the course of the day. For example, the UFP concentrations on the weekday morning traffic-rush hours are 20-30% higher than daily-average near arterial roads and highway sites, whereas it is only 10% higher in the background sites.
Long-term particle size distribution measurements indicate that freshly nucleated particles only contributes ~10% of average UFP concentrations at urban background sites in Pittsburgh. Therefore, people with higher UFP exposure are exposed to more fresh particles emitted from local sources, which might have higher toxicity. More than 50% of Pittsburgh residents live near-local sources and are therefore exposed to elevated UFP concentrations. We are developing a land use regression (LUR) model for UFP concentrations to assess the population impacts and to explore the association between trends in UFP and other pollutants. The results from this study provide new insights into the extent of spatial variations and local source impacts of urban UFP exposure to improve air pollution policy and decision making.