Arizona, a rapidly growing state in the southwestern U.S., faces ozone pollution challenges, including nonattainment areas in Yuma and Maricopa counties influenced by neighboring state pollution ...transport. In this study, we use five-year (2017–2021) hourly back-trajectories and O3 concentration data for concentration-weighted trajectory (CWT) analysis to identify transport pathways and potential source regions of O3 at six monitoring sites in Arizona. We divide the data into five seasons (winter, spring, dry summer, monsoon summer, and fall) to examine variations in O3 concentration and transport across sites and seasons. The highest mean O3 concentrations occur during spring (37–49 ppb), dry summer (39–51 ppb), and monsoon summer (34–49 ppb), while winter (19–41 ppb) exhibits the lowest seasonal mean. The CWT results reveal that high O3 concentrations (≥40 ppb) in Arizona, with the exception of Phoenix and Tucson sites, are influenced significantly by regional and international transport, especially in spring (14.9–35.4%) and dry summer (12.7–26.9%). The major potential source areas (excluding the Phoenix and Tucson sites) are predominantly located outside Arizona. This study highlights the critical role of pollution transport in influencing O3 variability within Arizona and will be valuable in shaping pollution control strategies in the future.
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 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.
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.
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.
Existing studies that focus on personal exposure to or the deposition dose of particulate pollution in developing regions are limited. Hence, in this study, as a first step, we present results on how ...people spend their daily time in Metro Manila, Philippines. This information is critical to assessing personal exposure to and the deposition dose of particulate pollutants. We found that people spend less time at home on workdays than weekends (52% versus 70%), the fraction of time spent at work/school increases with age until retirement, adult males spend less time at home than females (18% versus 28%), and people spend most of their time indoors (84%). The biggest difference from previous studies is the discovery that people in Metro Manila spend 11% of their daily time on average in transit traffic, which is up to 2.2 times more than in Europe, America, Korea, or China. Longer times in transit traffic subject the population of Metro Manila to a higher risk of increased exposure to toxic pollutants and adverse health symptoms. The main results of this research will be used in an upcoming study on the personal deposition dose of soot.
Fine particulate matter (PM2.5) concentrations in Metro Manila, Philippines have consistently exceeded the guideline values set by the World Health Organization (WHO). Although there has been much ...progress in understanding the components and sources of PM2.5, limited research has been done on the influence of meteorological factors. In particular, the influence of the planetary boundary layer height (PBLH) on PM2.5 concentration has not been studied due to inadequate observations. From January 2019–June 2020, measurements from a High Spectral Resolution Lidar (HSRL) filled this gap and allowed for PBLH estimation and aerosol typing. This paper investigates the roles of PBLH and regional and local wind circulations on the temporal evolution of aerosol pollution. Results show that daytime and nighttime PBLH variability is associated with solar heating and radiative cooling, respectively. Cloud-free conditions during the dry season yield a higher PBL growth rate than during the wet season when lower daytime and elevated nighttime PBLH are observed. Lower PM2.5 levels are generally observed during daytime when PBLH is at its maximum. However, the PBLH has a significant inverse correlation with PM2.5 only in the months of December-January-February. We find that horizontal directional wind shear between synoptic and mesoscale circulations confounds the PM2.5 - PBLH relationship by creating stagnant conditions conducive to aerosol accumulation. The lower 20% of PM2.5 concentrations occur during the prevalence of strong monsoon winds. On the other hand, the upper 80% are found during the occurrence of compound mesoscale winds (i.e., sea/land/lake/valley/mountain breezes and channeling monsoon winds). In addition, mountain breeze is found to be associated with lifting of aerosols, resulting in multi-layering within the PBL. The findings in the present study emphasize the role of complex topography and mesoscale scale winds arising from the landscape on aerosol pollution variability.
•PM2.5 – PBLH - wind interactions were investigated in Metro Manila, Philippines.•Inverse correlation between PM2.5 and PBLH were observed only in the dry season.•Horizontal directional wind shear between mesoscale winds lead to PM2.5 accumulation.•Advection of marine airmass by strong southwest monsoon resulted in unvarying PBLH.•Mountain breeze lifts aerosols and creates multi-layering within the PBL.
Ultrafine soot particles (black carbon, BC) in urban environments are related to adverse respiratory and cardiovascular effects, increased cases of asthma and premature deaths. These problems are ...especially pronounced in developing megacities in South-East Asia, Latin America, and Africa, where unsustainable urbanization ant outdated environmental protection legislation resulted in severe degradation of urban air quality in terms of black carbon emission. Since ultrafine soot particles do often not lead to enhanced PM10 and PM2.5 mass concentration, the risks related to ultrafine particle pollution may therefore be significantly underestimated compared to the contribution of secondary aerosol constituents. To increase the awareness of the potential toxicological relevant problems of ultrafine black carbon particles, we conducted a case study in Metro Manila, the capital of the Philippines.
Here, we present a part of the results from a detailed field campaign, called Manila Aerosol Characterization Experiment (MACE, 2015). Measurements took place from May to June 2015 with the focus on the state of mixing of aerosol particles. The results were alarming, showing the abundance of externally mixed refractory particles (soot proxy) at street site with a maximum daily number concentration of approximately 15000 #/cm3. That is up to 10 times higher than in cities of Western countries. We also found that the soot particle mass contributed from 55 to 75% of total street site PM2.5. The retrieved refractory particle number size distribution appeared to be a superposition of 2 ultrafine modes at 20 and 80 nm with a corresponding contribution to the total refractory particle number of 45 and 55%, respectively. The particles in the 20 nm mode were most likely ash from metallic additives in lubricating oil, tiny carbonaceous particles and/or nucleated and oxidized organic polymers, while bigger ones (80 nm) were soot agglomerates. To the best of the authors' knowledge, no other studies reported such high number concentration of ultrafine refractory particles under ambient conditions. Inverse modeling of emission factors of refractory particle number size distributions revealed that diesel-fed public utility Jeepneys, commonly used for public transportation, are responsible for 94% of total roadside emitted refractory particle mass.
The observed results showed that the majority of urban pollution in Metro Manila is dominated by carbonaceous aerosol. This suggests that PM10 or PM2.5 metrics do not fully describe possible health related effects in this kind of urban environments. Extremely high concentrations of ultrafine particles have been and will continue to induce adverse health related effects, because of their potential toxicity. We imply that in megacities, where the major fraction of particulates originates from the transport sector, PM10 or PM2.5 mass concentration should be complemented by legislative measurements of equivalent black carbon mass concentration.
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•Aerosol particles in urban Metro Manila are mixed exclusively externally.•Urban aerosol is dominated by refractory ultrafine particles.•Soot emission from Jeepneys contributes up to 94% of total urban soot mass.•In developing countries PM10 is not sufficient metric to evaluate air quality.
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).
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.
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