AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Urban Atmospheric Aerosol Size Distributions: A Global Perspective
Tianren Wu, BRANDON E. BOOR, Purdue University
Abstract Number: 818 Working Group: Urban Aerosols
Abstract Measurements of aerosol particle size distributions (PSDs) have been widely conducted in the urban atmospheric environment. However, there is limited research summarizing and synthesizing such measurements in order to identify geographical variations in the shape and magnitude of number and mass PSDs. The objective of this study is to establish a comprehensive urban PSD database by analyzing urban PSDs measured in cities around the globe.
The urban PSD database contains n=800 PSDs measured over the past two decades in n=124 cities in n=51 countries. Urban PSDs are classified by region: Africa (AF); Central, South, and Southeast Asia (CSSA); East Asia (EA); Europe (EU); Latin America (LA); North America (NA); Oceania (OC); and West Asia (WA). Collectively, the PSDs span the nucleation to coarse modes (3 to 10,000 nm). Multi-lognormal fitting parameters for each number and mass PSD are provided to facilitate subsequent analysis by the aerosol research community. Several different multi-lognormal fitting strategies were utilized according to the different size ranges and measurement techniques. Details on the measurement conditions are provided. The electrical mobility diameter was used as the reference size definition for the database. A size-resolved urban aerosol effective density database was compiled to allow for accurate conversion between the number and mass PSDs and from aerodynamic to electrical mobility diameter.
Geographical variations in the shape and magnitude of urban PSDs were identified. Significant variations in urban number PSDs were found between cities in EU, NA, and OC with those in CSSA and EA. In general, number PSDs in EU, NA, and OC are dominated by nucleation (3 to 10 nm) and Aitken (10 to 100 nm) mode particles, while those measured in CSSA and EA are shifted to larger particles and tend to present a dominant peak in the accumulation (100 to 1,000 nm) mode. Urban mass PSDs in CSSA, EA, EU, NA, and LA are typically bi-modal, exhibiting a dominant peak in the accumulation mode and a secondary peak in the coarse (1,000 to 10,000 nm) mode, while those in WA often show a dominant peak in the coarse mode. Weighted median agglomerated normalized PSDs are provided for each region. Most urban PSD measurements were short-term, with only 14% providing data for > 6 months. There are a paucity of urban PSDs measured in AF, CSSA, and LA, demonstrating the need for long-term aerosol measurements across wide size ranges in many cities around the globe.