PM2.5 Composition, Sources, Chemistry and Volatility over Manila: Insights from the ASIA-AQ Campaign
GUY SYMONDS, Pedro Campuzano-Jost, Dongwook Kim, Douglas A. Day, Seonsik Yun, Eric Apel, Rebecca Hornbrook, Alan Hills, Daun Jeong, Taehyoung Lee, Taehyun Park, Jihee Ban, Armin Wisthaler, Felix Piel, Tobias Reinecke, Wojciech Wojnowski, Richard Moore, Luke Ziemba, Michael Shook, ASIA-AQ Science Team, Maria Cambaliza, Melliza Cruz, James Simpas, James Crawford, Jose-Luis Jimenez, University of Colorado Boulder
Abstract Number: 448
Working Group: Urban Aerosols
Abstract
Urban air pollution is one of the leading causes of mortality worldwide. Both ozone and particulate matter (PM) are formed by complex chemical processes and are often still poorly understood. There is limited data for many parts of Southeast (SE) Asia, one of the most populous regions on Earth. Importantly, most of the available measurements have been ground-based. Aircraft studies can provide a different context on sources, dynamics, and vertical distribution of pollutants. In early 2024 during the NASA-led ASIA-AQ mission, we collected data onboard the NASA DC-8 on a wide range of pollutants with the objective of elucidating the local and regional sources of PM in several Asian megacities. This work focuses on greater Manila in the Philippines. Data was collected both during days of strong transport from the Asian continent and days dominated by local pollution, providing contrasting conditions to study. Manila stands out from most other Asian megacities by its larger organic PM fraction. Substantial concentrations of nitrate were measured in the morning above Manila. To better understand the sources of the large organic aerosol (OA) concentrations, different approaches were taken to identify primary and secondary contributions (POA and SOA). Using Positive Matrix Factorization (PMF), the overall contribution of Biomass Burning OA (BBOA) appears small, and thus does not explain the high OA fraction of total PM (although trash burning is a known localized source still under investigation). An appreciable share of Isoprene Epoxydiols-derived SOA (IEPOX-SOA) was observed outside Manila, including in fresh volcanic outflow, which is consistent with high isoprene emissions, acidity impacts, and strong NOx gradients. We show that “intensive” urban SOA formation rates (i.e., per unit ΔCO and photochemical age) in Manila are similar to the median of previous studies of Western megacities, e.g., Los Angeles.