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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  27 Jul 2020

27 Jul 2020

Review status
A revised version of this preprint is currently under review for the journal ACP.

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

Connor Stahl1, Melliza Templonuevo Cruz2,3, Paola Angela Bañaga2,4, Grace Betito2,4, Rachel A. Braun1, Mojtaba Azadi Aghdam1, Maria Obiminda Cambaliza2,4, Genevieve Rose Lorenzo2,5, Alexander B. MacDonald1, Miguel Ricardo A. Hilario2, Preciosa Corazon Pabroa6, John Robin Yee6, James Bernard Simpas2,4, and Armin Sorooshian1,5 Connor Stahl et al.
  • 1Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona, 85721, USA
  • 2Manila Observatory, Quezon City, 1108, Philippines
  • 3Institute of Environmental Science and Meteorology, University of the Philippines, Diliman, Quezon City, 1101, Philippines
  • 4Department of Physics, School of Science and Engineering, Ateneo de Manila University, Quezon City, 1108, Philippines
  • 5Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, Arizona, 85721, USA
  • 6Philippine Nuclear Research Institute-Department of Science and Technology, Commonwealth Avenue, Diliman, Quezon City, 1101, Philippines

Abstract. A 16-month (July 2018–October 2019) dataset of size-resolved aerosol composition is used to examine the sources and characteristics of five organic acids (oxalate, succinate, adipate, maleate, phthalate) and methanesulfonate (MSA) in Metro Manila, Philippines. As one of the most polluted megacities globally, Metro Manila offers a view of how diverse sources and meteorology impact the relative amounts and size distributions of these species. A total of 66 sample sets were collected with a Micro-Orifice Uniform Deposit Impactor (MOUDI), of which 54 sets were analyzed for composition. Organic acids and MSA surprisingly were less abundant than in other global regions that are also densely populated. The combined species accounted for an average of 0.80 ± 0.66 % of total gravimetric mass between 0.056 and 18 µm, leaving still 33.74 % of mass unaccounted for after considering black carbon and water-soluble ions and elements. The unresolved mass is suggested to consist of non-water-soluble metals as well as both water-soluble and non-water-soluble organics. Oxalate was approximately an order of magnitude more abundant than the other five species (148.59 ± 94.26 ng m−3 versus others being < 10 ng m−3). Both PMF and correlation analysis is conducted with tracer species to investigate the possible sources for organic acids and MSA. Enhanced biomass burning influence in the 2018 southwest monsoon (SWM18) resulted in especially high levels of submicrometer succinate, MSA, oxalate, and phthalate. Peculiarly, MSA had negligible contributions from marine sources but instead was linked to burning and combustion. Enhanced precipitation during the two SWM seasons (8 June–4 October 2018 and 14 June–7 October 2019) coincided with stronger influence from local emissions rather than long-range transport, leading to notable concentration enhancements in both the sub- and supermicrometer ranges for some species (e.g., maleate and phthalate). While secondary formation via gas-to-particle conversion largely explained submicrometer peaks for all species, several species (i.e., phthalate, adipate, succinate, oxalate) exhibited a prominent peak in the coarse mode, largely owing to their association with crustal emissions (i.e., more alkaline aerosol type) rather than sea salt. Oxalate’s strong association with sulfate in the submicrometer mode supports an aqueous-phase formation pathway for the study region, but also high concentration during periods of low rain and high solar radiation indicates photo-oxidation is an important formation pathway.

Connor Stahl et al.

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Status: final response (author comments only)
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Connor Stahl et al.

Data sets

An Annual Time Series of Weekly Size-Resolved Aerosol Properties in the Megacity of Metro Manila, Philippines Connor Stahl, Melliza Templonuevo Cruz, Paola Angela Banaga, Grace Betito, Rachel A. Braun, Mojtaba Azadi Aghdam, Maria Obiminda Cambaliza, Genevieve Rose Lorenzo, Alexander MacDonald, Preciosa Corazon Pabroa, John Robin Yee, James Bernard Simpas, and Armin Sorooshian

Connor Stahl et al.


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Latest update: 21 Oct 2020
Publications Copernicus
Short summary
Long term (16-month) high frequency (weekly) measurements of size-resolved aerosol composition are reported. Important insights are discussed about factors (e.g., transport, fires, precipitation, photo-oxidation) impacting the mass size distributions of organic and sulfonic acids at a coastal megacity with diverse meteorology. The size-resolved nature of the data yielded one such finding that organic acids preferentially adsorb to dust rather than sea salt particles.
Long term (16-month) high frequency (weekly) measurements of size-resolved aerosol composition...