This paper presents novel results from size-resolved particulate matter (PM)
mass, composition, and morphology measurements conducted during the 2018
southwest monsoon (SWM) season in Metro Manila, ...Philippines. Micro-orifice
uniform deposit impactors (MOUDIs) were used to collect PM sample sets
composed of size-resolved measurements at the following aerodynamic cut-point
diameters (Dp): 18, 10, 5.6, 3.2, 1.8, 1.0, 0.56, 0.32, 0.18, 0.10, and
0.056 µm. Each sample set was analyzed for composition of the
water-soluble fraction. Analysis for mass was carried out on two sample sets, whereas
black carbon (BC) and morphology analysis were analyzed on a single sample set.
The bulk of the PM mass was between 0.18 and 1.0 µm with a dominant mode
between 0.32 and 0.56 µm. Similarly, most of the black carbon (BC) mass
was found between 0.10 and 1.0 µm, peaking between 0.18 and 0.32 µm.
These peaks are located in the Greenfield gap, or the size range between
0.10 and 1.0 µm, where wet scavenging by rain is relatively inefficient.
In the range between 0.10 and 0.18 µm, BC constituted 78.1 % of the
measured mass. Comparable contributions of BC (26.9 %) and the
water-soluble fraction (33.4 %) to total PM were observed and most of the
unresolved mass, which amounted to 39.6 % in total, was for diameters
exceeding 0.32 µm. The water-soluble ions and elements exhibited an
average combined concentration of 8.53 µg m−3, with
SO42-, NH4+, NO3-, Na+, and Cl− as
the major contributors. Positive matrix factorization (PMF) was applied to
identify the possible aerosol sources and estimate their contribution to the
water-soluble fraction of collected PM. The factor with the highest
contribution was attributed to “aged aerosol” (48.0 %), while “sea
salt” (22.5 %) and “combustion” emissions (18.7 %) had comparable
contributions. “Vehicular/resuspended dust” (5.6 %) and “waste
processing” emissions (5.1 %) were also identified. Microscopy analysis
highlighted the ubiquity of nonspherical particles regardless of size,
which is significant when considering calculations of parameters such as
single scattering albedo, the asymmetry parameter, and the extinction efficiency. The significant influence from aged aerosol to Metro Manila during the SWM
season indicates that local sources in this megacity do not fully govern
this coastal area's aerosol properties. The fact that the majority of the regional
aerosol mass burden is accounted for by BC and other insoluble components
has important downstream effects on the aerosol hygroscopic properties,
which depend on composition. The results are relevant for understanding the
impacts of monsoonal features on size-resolved aerosol properties, notably
aqueous processing and wet scavenging. Finally, the results of this work
provide contextual data for future sampling campaigns in Southeast Asia such
as the airborne component of the Cloud, Aerosol, and Monsoon Processes
Philippines Experiment (CAMP2Ex) planned for the SWM season in 2019.
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-aerosol-loading 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.
Fireworks degrade air quality, reduce visibility, alter atmospheric chemistry, and cause short-term adverse health effects. However, there have not been any comprehensive physicochemical and optical ...measurements of fireworks and their associated impacts in a Southeast Asia megacity, where fireworks are a regular part of the culture. Size-resolved particulate matter (PM) measurements were made before, during, and after New Year 2019 at the Manila Observatory in Quezon City, Philippines, as part of the Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex). A high-spectral-resolution lidar (HSRL) recorded a substantial increase in backscattered signal associated with high aerosol loading ∼440 m above the surface during the peak of firework activities around 00:00 (local time). This was accompanied by PM2.5 concentrations peaking at 383.9 µg m−3. During the firework event, water-soluble ions and elements, which affect particle formation, growth, and fate, were mostly in the submicrometer diameter range. Total (>0.056 µm) water-soluble bulk particle mass concentrations were enriched by 5.7 times during the fireworks relative to the background (i.e., average of before and after the firework). The water-soluble mass fraction of PM2.5 increased by 18.5 % above that of background values. This corresponded to increased volume fractions of inorganics which increased bulk particle hygroscopicity, kappa (κ), from 0.11 (background) to 0.18 (fireworks). Potassium and non-sea-salt (nss) SO42- contributed the most (70.9 %) to the water-soluble mass, with their mass size distributions shifting from a smaller to a larger submicrometer mode during the firework event. On the other hand, mass size distributions for NO3-, Cl−, and Mg2+ (21.1 % mass contribution) shifted from a supermicrometer mode to a submicrometer mode. Being both uninfluenced by secondary aerosol formation and constituents of firework materials, a subset of species were identified as the best firework tracer species (Cu, Ba, Sr, K+, Al, and Pb). Although these species (excluding K+) only contributed 2.1 % of the total mass concentration of water-soluble ions and elements, they exhibited the highest enrichments (6.1 to 65.2) during the fireworks. Surface microscopy analysis confirmed the presence of potassium/chloride-rich cubic particles along with capsule-shaped particles in firework samples. The results of this study highlight how firework emissions change the physicochemical and optical properties of water-soluble particles (e.g., mass size distribution, composition, hygroscopicity, and aerosol backscatter), which subsequently alters the background aerosol's respirability, influence on surroundings, ability to uptake gases, and viability as cloud condensation nuclei (CCN).
This study utilizes multiple aerosol datasets collected in Metro Manila, Philippines to investigate sea salt aerosol characteristics. This coastal megacity allows for an examination of the impacts of ...precipitation and mixing of different air masses on sea salt properties, including overall concentration and size-resolved composition, hygroscopicity, and morphology. Intensive size-resolved measurements with a Micro-Orifice Uniform Deposit Impactor (MOUDI) between July–December 2018 revealed the following major results: (i) sea salt levels exhibit wide variability during the wet season, driven primarily by precipitation scavenging; (ii) ssNa+ and Cl− peaked in concentration between 1.8 and 5.6 μm, with Cl− depletion varying between 21.3 and 90.7%; (iii) mixing of marine and anthropogenic air masses yielded complex non-spherical shapes with species attached to the outer edges and Na+ uniformly distributed across particles unlike Cl−; (iv) there was significant contamination of sea salt aerosol by a variety of crustal and anthropogenic pollutants (Fe, Al, Ba, Mn, Pb, NO3−, V, Zn, NH4+); (v) categorization of samples in five different pollutant type categories (Background, Clean, Fire, Continental Pollution, Highest Rain) revealed significant differences in overall Cl− depletion with enhanced depletion in the submicrometer range versus the supermicrometer range; (vi) κ values ranged from 0.02 to 0.31 with a bimodal profile across all stages, with the highest value coincident with the highest sea salt volume fraction in the 3.2–5.6 μm stage, which is far lower than pure sea salt due to the significant influence of organics and black carbon. Analysis of longer term PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) and PMcoarse (= PM10 – PM2.5) data between August 2005 and October 2007 confirmed findings from the MOUDI data that more Cl− depletion occurred both in the wet season versus the dry season and on weekdays versus weekend days. This study demonstrates the importance of accounting for two factors in future studies on sea salt: (i) non-sea salt (nss) sources of Na+ impact calculations such as for Cl− depletion that typically assume that total Na+ concentration is derived from salt; and (ii) considering precipitation data over a larger spatial domain rather than a point measurement at the study site to investigate wet scavenging.
•Precipitation ranged widely and governed variability in sea salt concentrations.•Mixing of sea salt with other air masses manipulated sea salt properties.•Hygroscopicity (κ ~ 0.3) was highest where sea salt was most enhanced (3.2–5.6 μm).•Accounting for non-sea salt sources of Na+ impacts calculations relevant to sea salt.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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, still leaving 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 (149 ± 94 ng m−3 versus others being
< 10 ng m−3) across the 0.056–18 µm size range. Both
positive matrix factorization (PMF) and correlation analysis are conducted
with tracer species to investigate the possible sources of organic acids
and MSA. Enhanced biomass burning influence in the 2018 southwest monsoon
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 biomass burning and combustion. Enhanced
precipitation during the two monsoon seasons (8 June–4 October 2018 and
14 June–7 October 2019) coincided with a 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 is consistent with submicrometer peaks for the organic acids and
MSA, 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. However, high concentrations during periods of low rain and high
solar radiation suggest photo-oxidation is an important formation pathway.
Leveraging aerosol data from multiple airborne and surface‐based field campaigns encompassing diverse environmental conditions, we calculate statistics of the oxalate‐sulfate mass ratio (median: ...0.0217; 95% confidence interval: 0.0154–0.0296; R = 0.76; N = 2,948). Ground‐based measurements of the oxalate‐sulfate ratio fall within our 95% confidence interval, suggesting the range is robust within the mixed layer for the submicrometer particle size range. We demonstrate that dust and biomass burning emissions can separately bias this ratio toward higher values by at least one order of magnitude. In the absence of these confounding factors, the 95% confidence interval of the ratio may be used to estimate the relative extent of aqueous processing by comparing inferred oxalate concentrations between air masses, with the assumption that sulfate primarily originates from aqueous processing.
Plain Language Summary
The extent of atmospheric chemical processing remains an uncertain aspect of air mass characterization. Addressing this uncertainty is important because chemical reactions in the atmosphere in the presence of water (aqueous processing) produce a large fraction of global aerosol mass. The oxalate‐to‐sulfate ratio has been proposed as an indicator of aqueous processing, where higher values point to increased processing of an air mass. In this study, we quantify a range in the oxalate‐to‐sulfate mass ratio (0.0154–0.0296) using data from multiple field campaigns encompassing a diverse set of environments. This range is robust near the surface for particles below 1 micrometer in diameter. Larger particles, especially dust, and biomass burning particles significantly affect the oxalate‐to‐sulfate ratio and thus may confound the interpretation of a high oxalate‐to‐sulfate ratio as a signal of aqueous processing. In the absence of dust and biomass burning particles, the oxalate‐to‐sulfate ratio range may be used to compare the relative extent of aqueous processing between different air masses.
Key Points
Oxalate‐sulfate mass ratios show similarity across multiple environments (95% confidence interval: 0.0154–0.0296; R = 0.76; N = 2,948)
Oxalate‐sulfate mass ratio is biased toward higher values in presence of coarse aerosol particles and/or biomass burning
Ground‐based, size‐resolved measurements reveal that the ratio can be robust within the mixed layer for the submicrometer mode
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Size-resolved aerosol samples were collected in Metro Manila between July 2018 and October 2019. Two Micro-Orifice Uniform Deposit Impactors (MOUDI) were deployed at Manila Observatory in Quezon ...City, Metro Manila with samples collected on a weekly basis for water-soluble speciation and mass quantification. Additional sets were collected for gravimetric and black carbon analysis, including during special events such as holidays. The unique aspect of the presented data is a year-long record with weekly frequency of size-resolved aerosol composition in a highly populated megacity where there is a lack of measurements. The data are suitable for research to understand the sources, evolution, and fate of atmospheric aerosols, as well as studies focusing on phenomena such as aerosol-cloud-precipitation-meteorology interactions, regional climate, boundary layer processes, and health effects. The dataset can be used to initialize, validate, and/or improve models and remote sensing algorithms.
We present the first study of the weekly cycles (WCs) of chemically speciated and size‐resolved particulate matter (PM) in Metro Manila, Philippines, a coastal megacity located within a highly ...complex meteorological environment that is subject to both anthropogenic and natural sources. To measure PM, Micro‐Orifice Uniform Deposit Impactors (MOUDIs) were deployed in Metro Manila from August 2018 to October 2019 and samples were analyzed for ionic and elemental species, including black carbon (BC). The WC in Metro Manila varied remarkably across seasons, linked to shifts in meteorology, transport, and aerosol source. Identified aerosol sources were traffic, local and regional burning, dust, sea salt, and secondary aerosol formation. Direct emissions induced a late workweek peak, while secondary aerosol formation led to a weekend peak in response to precursor buildup mainly from traffic. Seasonal analysis revealed that local burning from solid waste management and agricultural fires induced a strong WC peak while regional burning emissions from the Maritime Continent (MC) and possibly the Asian continent elevated seasonal baseline concentrations of the WC. BC showed a seasonally persistent WC, consistent in magnitude, weekly peak timing, and particle size. The dominant submicrometer WC and the contribution of BC across seasons have important ramifications on public health and policymaking, which are also discussed. As many of the observed WC patterns are undetectable when using only bulk PM, this study demonstrates that a seasonal, size‐resolved, and chemically speciated characterization is required to more fully understand the driving mechanisms governing WCs.
Key Points
Significant variability was observed in the weekly cycle of particulate matter (particle size and composition) as a function of season
Submicrometer aerosol peak timing indicates that secondary formation increases in response to precursor buildup, inducing a weekend peak
Black carbon showed a seasonally persistent weekly cycle, consistent in magnitude, weekly peak timing, and particle size
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This study examines the mass size distributions and crustal enrichment factors (EFs) of arsenic (As), cadmium (Cd), and lead (Pb) for diverse regions: coastal marine (Marina, California), arid mining ...facility (Hayden, Arizona), arid urban (Tucson, Arizona), free troposphere (Mt. Lemmon, Arizona), and coastal urban (Manila, Philippines). Micro-orifice uniform deposit impactor (MOUDI) measurements revealed several notable features. All sites showed a bimodal profile with a peak in the submicrometer and supermicrometer diameter range except for Manila, which peculiarly lacked a peak above 1 μm. Enrichment factor analysis revealed contaminated dust at all sites, even the free tropospheric site, with greater contamination in the submicrometer range. The most extensive dataset in Manila allowed for seasonal analysis, which revealed differences among the same species based on seasonally-dependent transport patterns. Sites experiencing biomass burning influence (Manila and Marina) generally exhibited suppressed concentrations and crustal EFs during burning periods presumably because soil emitted from fires is fresh without extensive processing time to become contaminated. These results have important implications for a variety of aerosol effects dependent on aerosol size (e.g., public health, biogeochemical cycling, heterogeneous chemistry) and underscore the importance of accounting for the coarse aerosol mode as more dust emissions are expected in warmer climate scenarios.
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•Four sites reveal As, Cd, and Pb mass concentration peaks in the < 1 µm and > 1 µm range and a fifth only had a < 1 µm peak.•Enrichment factor (EF) analysis showed that all five sites experience dust contamination in the < 1 µm and > 1 µm range.•Manila revealed no change in concentration modes across seasons and the highest dust contamination in the < 1 µm range.•Periods influenced by fire exhibited lower concentrations and crustal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This work focuses on total organic carbon (TOC) and contributing species in cloud water over Southeast Asia using a rare airborne dataset collected during NASA's Cloud, Aerosol and Monsoon Processes ...Philippines Experiment (CAMP2Ex), in which a wide variety of maritime clouds were studied, including cumulus congestus, altocumulus, altostratus, and cumulus. Knowledge of TOC masses and their contributing species is needed for improved modeling of cloud processing of organics and to understand how aerosols and gases impact and are impacted by clouds. This work relies on 159 samples collected with an axial cyclone cloud-water collector at altitudes of 0.2–6.8 km that had sufficient volume for both TOC and speciated organic composition analysis. Species included monocarboxylic acids (glycolate, acetate, formate, and pyruvate), dicarboxylic acids (glutarate, adipate, succinate, maleate, and oxalate), methanesulfonic acid (MSA), and dimethylamine (DMA). TOC values range between 0.018 and 13.66 ppm C with a mean of 0.902 ppm C. The highest TOC values are observed below 2 km with a general reduction aloft. An exception is samples impacted by biomass burning for which TOC remains enhanced at altitudes as high as 6.5 km (7.048 ppm C). Estimated total organic matter derived from TOC contributes a mean of 30.7 % to total measured mass (inorganics + organics). Speciated organics contribute (on a carbon mass basis) an average of 30.0 % to TOC in the study region and account for an average of 10.3 % to total measured mass.The order of the average contribution of species to TOC, in decreasing contribution of carbon mass, is as follows (±1 standard deviation): acetate (14.7 ± 20.5 %), formate (5.4 ± 9.3 %), oxalate (2.8 ± 4.3 %), DMA (1.7 ± 6.3 %), succinate (1.6 ± 2.4 %), pyruvate (1.3 ± 4.5 %), glycolate (1.3 ± 3.7 %), adipate (1.0 ± 3.6 %), MSA (0.1 ± 0.1 %), glutarate (0.1 ± 0.2 %), and maleate (< 0.1 ± 0.1 %). Approximately 70 % of TOC remains unaccounted for, highlighting the complex nature of organics in the study region; in samples collected in biomass burning plumes, up to 95.6 % of TOC mass is unaccounted for based on the species detected. Consistent with other regions, monocarboxylic acids dominate the speciated organic mass (∼ 75 %) and are about 4 times more abundant than dicarboxylic acids.Samples are categorized into four cases based on back-trajectory history, revealing source-independent similarity between the bulk contributions of monocarboxylic and dicarboxylic acids to TOC (16.03 %–23.66 % and 3.70 %–8.75 %, respectively). Furthermore, acetate, formate, succinate, glutarate, pyruvate, oxalate, and MSA are especially enhanced during biomass burning periods, which is attributed to peat emissions transported from Sumatra and Borneo. Lastly, dust (Ca2+) and sea salt (Na+/Cl-) tracers exhibit strong correlations with speciated organics, supporting how coarse aerosol surfaces interact with these water-soluble organics.
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