Long-range aerosol transport and impacts on size-resolved aerosol composition in Metro Manila, Philippines

Abstract

This study analyzes long-range transport of aerosol and aerosol chemical characteristics based on instances of high-and low-aerosol-loading events determined via ground-based size-resolved aerosol measurements collected at the Manila Observatory in Metro Manila, Philippines, from July to October 2018. Multiple data sources, including models, remote sensing, and in situ measurements, are used to analyze the impacts of long-range aerosol transport on Metro Manila and the conditions at the local and synoptic scales facilitating this transport. Through the use of case studies, evidence of long-range transport of biomass burning aerosol and continental emissions is identified in Metro Manila. Long-range transport of biomass burning aerosol from the Maritime Continent, bolstered by southwesterly flow and permitted by low rainfall, was identified through model results and the presence of biomass burning tracers (e.g., K, Rb) in the ground-based measurements. The impacts of emissions transported from continental East Asia on the aerosol characteristics in Metro Manila are also identified; for one of the events analyzed, this transport was facilitated by the nearby passage of a typhoon. Changes in the aerosol size distributions, water-soluble chemical composition, and contributions of various organic aerosol species to the total water-soluble organic aerosol were examined for the different cases. The events impacted by biomass burning transport had the overall highest concentration of water-soluble organic acids, while the events impacted by long-range transport from continental East Asia showed high percent contributions from shorter-chain dicarboxylic acids (i.e., oxalate) that are often representative of photochemical and aqueous processing in the atmosphere. The low-aerosolloading event was subject to a larger precipitation accumulation than the high-aerosol events, indicative of wet scavenging as an aerosol sink in the study region. This low-aerosol event was characterized by a larger relative contribution from supermicrometer aerosols and had a higher percent contribution from longer-chain dicarboxylic acids (i.e., maleate) to the water-soluble organic aerosol fraction, indicating the importance of both primary aerosol emissions and local emissions.

Sources and characteristics of size-resolved particulate organic acids and methanesulfonate in a coastal megacity: Manila, Philippines

“…To qualify as a valid result, reported PMF results had to meet the following criteria: (i) factors are mapped with BS runs, (ii) there are no factor swaps in DISP, (iii) displacements from its fitted values (dQ) are close or equal to 0 %, and (iv) there are no factor swaps in BS-DISP, where Al, Ti, K, Rb, V, Ni, As, Cd, Pb, Na + , Cl − , NO − 3 , and SO 2− 4 were displaced. PMF diagnostics can be seen in Table S4 based on the method of Brown et al (2015).…”

An annual time series of weekly size-resolved aerosol properties in the megacity of Metro Manila, Philippines

“…The site was segregated from surrounding urban areas, including a major roadway, by a grove of trees circling the campus. However, it was clearly impacted by local urban emissions and long-range transport based on results from the first six months of data collected [16][17][18] . Sampling took place on the 3 rd floor of the MO office building, which was approximately 85 m above sea level.…”

“…Cruz et al 16 looked at size-resolved PM composition during the 2018 southwest monsoon season and conducted positive matrix factorization (PMF) to identify PM sources, which were attributed to aged PM, sea salt, combustion emissions, vehicular/resuspended dust, and waste processing emissions. Braun et al 18 presented case examples of long-range transport of PM from east and southeast Asia, such as biomass burning from the Maritime Continent and transport from continental East Asia. They also presented examples of different transport pathways of pollution to the study site which yielded concentration differences for species such as K, Rb, Ba, V, Pb, Mo, and Sn.…”

Characterizing Weekly Cycles of Particulate Matter in a Coastal Megacity: The Importance of a Seasonal, Size‐Resolved, and Chemically Speciated Analysis

“…As biofuel combustion is a major aerosol source in Southeast Asia (Reid et al, 2012), it is important to consider its influence both locally and regionally. Potassium serves as our main tracer (Landis et al, 2017;S.-C. Hsu et al, 2009), supplemented by sulfate, organic acids, and ammonium as these are tracers of both burning activity and transport (Braun et al, 2020;Calzolai et al, 2015;Perrone et al, 2019). The WCs of burning tracers are most active in the 0.18-to 1.0-μm range and are present in all seasons except in SON, likely due to burning levels hindered locally by precipitation ( Figure 1a) and regionally because of the monsoon transition ( Figure 2d).…”