Fine Aerosol Research Articles

Understanding organic aerosols in Bogotá, Colombia: In-situ observations and regional-scale modeling

Organic aerosol (OA) is one of the major components of fine atmospheric aerosol particles. Recent field campaigns and modeling studies in Colombia have demonstrated the presence of a large OA fraction in urban and rural aerosols. In this work we focus on constraining the sources associated with OA and its precursors over the city of Bogotá, Colombia. We used PM2.5 chemical speciation data from field campaigns carried out during 2018 to evaluate the ability of a regional transport model to reproduce and explain the observed OA. The samples were collected at three sites during high- and low-aerosol concentration seasons in the region. We used The Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) with two different chemical mechanisms and aerosol schemes, RACM/MADE-VBS and MOZART/MOSAIC, in conjunction with the detailed in-situ aerosol chemical speciation observations to analyze the seasonality of OA in the city of Bogotá, and to establish the most relevant sources. Simulations were carried out for the same periods for which data is available, spanning a high biomass burning (BB) season (February 2018) and a low biomass burning season (September 2018). We demonstrated that long-range transport of BB emissions from Northern Amazonia can episodically increase aerosol loading during September, while BB activity in the Grasslands of the Orinoco River Basin are the main source during February. The two aerosol schemes utilized in this work reproduce the observed seasonal variations in total fine aerosol concentration, with a difference between February and September of 10 μg m−3. The comparison between aerosol schemes demonstrated that MOZART/MOSAIC consistently predicted more OA with a larger SOA:OA ratio than in the RACM/MADE-VBS experiment. SOA dominates the OA fraction by 66% for RACM/MADE-VBS and 74% for MOZART/MOSAIC during February and 69% for RACM/MADE-VBS and 71% for MOZART/MOSAIC during September. These differences between organic aerosol burden between the mechanisms used in this study may be attributed to the different treatment of SOA gas/particle partitioning in the schemes.

Dwindling aromatic compounds in fine aerosols from chunk coal to honeycomb briquette combustion

With the implementation of clean coal policy in China, the chunk coal has been gradually replaced by honeycomb briquette in domestic energies. In this study, the molecular composition of fine particles (PM2.5) from chunk coal and honeycomb briquette combustion is characterized using the Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). More than 6000 molecular formulae were detected in each PM2.5 sample. A remarkable decrease in unsaturation and aromatic compounds was found from chunk coal to honeycomb briquette derived aerosols. Around 73.6% of the unique CHON compounds in chunk coal are considered to have aromatic structures, while it decreased to 7.3% in honeycomb briquette. Most of these nitroaromatics detected only in chunk coal are highly carcinogenic and mutagenic with 4–6 rings. Moreover, the aromatic compounds in sulfur-containing compounds also showed a significant decrease. Meanwhile, because of the perforated shape and the additives added during the production of honeycomb briquettes, there are more heteroatoms-containing molecules released from honeycomb briquette combustion, which are highly functional compounds with high molecular weight, high degree of oxidation, and low volatility. Our results provide molecular level evidence that the transformation from chunk coal to honeycomb briquette can effectively reduce the emission of aromatic compounds, which is beneficial to assessing and reducing the impacts to climate change as well as human health.

Fragment ion–functional group relationships in organic aerosols using aerosol mass spectrometry and mid-infrared spectroscopy

Abstract. Aerosol mass spectrometry (AMS) and mid-infrared spectroscopy (MIR) are two analytical methods for characterizing the chemical composition of organic matter (OM). While AMS provides high-temporal-resolution bulk measurements, the extensive fragmentation during the electron ionization makes the characterization of OM components limited. The analysis of aerosols collected on polytetrafluoroethylene (PTFE) filters using MIR, on the other hand, provides functional group information with reduced sample alteration but results in a relatively low temporal resolution. In this work, we compared and combined MIR and AMS measurements for several environmental chamber experiments of combustion-related aerosols to achieve a better understanding of the AMS spectra and the OM chemical evolution with aging. Fresh emissions of wood and coal burning were injected into an environmental simulation chamber and aged with hydroxyl and nitrate radicals. A high-resolution time-of-flight AMS measured the bulk chemical composition of fine OM. Fine aerosols were also sampled on PTFE filters before and after aging for the offline MIR analysis. After comparing AMS and MIR bulk measurements, we used multivariate statistics to identify the functional groups associated the most with the AMS OM for different aerosol sources and oxidants. We also identified the key fragment ions resulting from molecules containing each functional group for the complex OM generated from biomass and fossil fuel combustion. Finally, we developed a statistical model that enables the estimation of the high-time-resolution functional group composition of OM using collocated AMS and MIR measurements. AMS spectra can be used to interpolate the functional group measurements by MIR using this approach. The latter allows us to better understand the evolution of OM during the aging process.

Long-Term (2017–2020) Aerosol Optical Depth Observations in Hohhot City in Mongolian Plateau and the Impacts from Different Types of Aerosol

Aerosol optical depth (AOD) measurements for 2017–2020 in urban Hohhot of the Mongolian plateau, a transition zone between the depopulated zone and East Asian urban agglomeration, were analyzed for the first time. Results show that annual AOD500 and Ångström exponent α440-675 were 0.36 ± 0.09 and 1.11 ± 0.16 (2017), 0.41 ± 0.12 and 0.90 ± 0.28 (2018), 0.38 ± 0.09 and 1.13 ± 0.24 (2019), 0.38 ± 0.12 and 1.17 ± 0.22 (2020), respectively, representing a slightly polluted level with a mixed type of coarse dust aerosol and a fine urban/industrial aerosol. Throughout the year, depopulated-zone continental air flows predominated in Hohhot (i.e., NW-quadrant wind), accounting for 82.12% (spring), 74.54% (summer), 63.61% (autumn), and 100% (winter). The clean and strong NW-quadrant air flows induced by the south movement of a Siberian anticyclone resulted in a low 500-nm AOD of 0.30 ± 0.29, 0.20 ± 0.15, 0.24 ± 0.29, and 0.13 ± 0.08 from spring to winter. Meanwhile, the local emissions from Hohhot city, as well as anthropogenic urban/industrial aerosols transported by southern and western air masses, originating from southern urban agglomeration and western industrial cities (Baotou, Wuhai, etc.), contributed to the highest aerosol loading, with significant transformation rates of the secondary aerosols Sulfate-Nitrate-Ammonium (SNA) of 47.45%, 57.39%, 49.88%, and 45.16–47.36% in PM2.5 for each season. The extinction fraction of fine aerosols under these anthropogenic trajectories can be as high as 80%, and the largest fine aerosol size was around 0.2–0.25 μm. Dust aerosols were suspending in urban Hohhot all year, although at different levels for different seasons, and the extinction fraction of dust aerosol during sandstorms was generally higher than 70%.

CFD Study of Dry Pulmonary Surfactant Aerosols Deposition in Upper 17 Generations of Human Respiratory Tract

The efficient generation of high concentrations of fine-particle, pure surfactant aerosols provides the possibility of new, rapid, and effective treatment modalities for Acute Respiratory Distress Syndrome (ARDS). SUPRAER-CATM is a patented technology by Kaer BiotherapeuticsTM, which is a new class of efficient aerosol drug generation and delivery system using Compressor Air (CA). SUPRAER-CA is capable of aerosolizing relatively viscous solutions or suspensions of proteins and surfactants and of delivering them as pure fine particle dry aerosols. In this Computational Fluid Dynamics (CFD) study, we select a number of sites within the upper 17 generations of the human respiratory tract for calculation of the deposition of dry pulmonary surfactant aerosol particles. We predict the percentage of inhaled dry pulmonary surfactant aerosol arriving from the respiratory bronchioles to the terminal alveolar sacs. The dry pulmonary surfactant aerosols, with a Mass Median Aerodynamic Diameter (MMAD) of 2.6 µm and standard deviation of 1.9 µm, are injected into the respiratory tract at a dry surfactant aerosol flow rate of 163 mg/min to be used in the CFD study at an air inhalation flow rate of 44 L/min. This CFD study in the upper 17th generation of a male adult lung has shown computationally that the penetration fraction (PF) is approximately 25% for the inhaled surfactant aerosols. In conclusion, an ARDS patient might receive approximately one gram of inspired dry surfactant aerosol during an administration period of one hour as a possible means of further inflating partly collapsed alveoli.

On the Redox-Activity and Health-Effects of Atmospheric Primary and Secondary Aerosol: Phenomenology

The RHAPS (Redox-Activity And Health-Effects Of Atmospheric Primary And Secondary Aerosol) project was launched in 2019 with the major objective of identifying specific properties of the fine atmospheric aerosol from combustion sources that are responsible for toxicological effects and can be used as new metrics for health-related outdoor pollution studies. In this paper, we present the overall methodology of RHAPS and introduce the phenomenology and the first data observed. A comprehensive physico-chemical aerosol characterization has been achieved by means of high-time resolution measurements (e.g., number size distributions, refractory chemical components, elemental composition) and low-time resolution analyses (e.g., oxidative potential, toxicological assays, chemical composition). Preliminary results indicate that, at the real atmospheric conditions observed (i.e., daily PM1 from less than 4 to more than 50 μg m−3), high/low mass concentrations of PM1, as well as black carbon (BC) and water soluble Oxidative Potential (WSOP,) do not necessarily translate into high/low toxicity. Notably, these findings were observed during a variety of atmospheric conditions and aerosol properties and with different toxicological assessments. Findings suggest a higher complexity in the relations observed between atmospheric aerosol and toxicological endpoints that go beyond the currently used PM1 metrics. Finally, we provide an outlook to companion papers where data will be analyzed in more detail, with the focus on source apportionment of PM1 and the role of source emissions on aerosol toxicity, the OP as a predictive variable for PM1 toxicity, and the related role of SOA possessing redox-active capacity, exposure-response relationships for PM1, and air quality models to forecast PM1 toxicity.

Leucine improves the aerosol performance of dry powder inhaler formulations of siRNA-loaded nanoparticles

Thermostable dry powder inhaler (DPI) formulations with high aerosol performance are attractive inhalable solid dosage forms for local treatment of inflammatory lung diseases. We recently demonstrated that lipidoid-polymer hybrid nanoparticles (LPNs) loaded with small interfering RNA (siRNA) directed against tumor necrosis factor alpha (TNF-α) mediate efficient intracellular siRNA delivery and reduce inflammation in vivo. Here, we show that mixtures of the stabilizing excipients trehalose (Tre) and dextran (Dex), in combination with the shell-forming dispersion enhancer leucine (Leu), stabilize TNF-α siRNA-loaded LPNs during spray drying into nanocomposite microparticles, and result in DPI formulations with high aerosol performance. At low Leu content (0 to 10%, w/w), the DPI formulations were amorphous, and exhibited poor aerosol performance. When the Leu content was increased from 20 to 60% (w/w), the surface content of Leu increased from 39.2 to 68.1 mol%, and the flowability was significantly improved. Microscopy analysis suggest that the improved powder dispersibility is the result of a wrinkled surface morphology, which reduces the surface area available for interparticle interactions. Increasing the Leu content further (to above 10%, w/w) did not influence the aerosol performance, and the aerosol yield was maximal at 30–40% Leu (w/w). Formulations containing 40% Leu and a Tre:Dex ratio of 10:90 (w/w) displayed a high fine particle fraction and aerosol properties suitable for inhalation. The chemical integrity of TNF-α siRNA was preserved in the solid state, and biodistribution studies in mice showed that pulmonary administration of DPI formulations with high aerosol performance resulted in homogenous deep lung deposition. Our results demonstrate that at optimal ratios, ternary excipient mixtures of Leu, Tre and Dex protect TNF-α siRNA-loaded LPNs during spray drying. Hence, this study shows that microparticles with an amorphous Tre/Dex matrix and a crystalline Leu shell efficiently stabilize the nanocomposite LPNs in the solid state, and ensure aerosol properties suitable for inhalation.

The Effect of Varying Aerosol Concentrations on Visibility and Particle Size Distribution in Urban Atmosphere: Validating OPAC Results using MERRA Satellite Aerosol Data

Well validated simulation software and models are meant to add value through a more precise representation of different atmospheric features and climate characteristics that are physically out of reach. In this work, comparison and validation was carried out using the Modern Era Retrospective Analysis for Research and Applications (MERRA) averaged Angstrom Exponents (α) and averaged visibilities for ten urban countries against simulated Optical Properties of Aerosols and Clouds (OPAC) urban components. The simulations of OPAC were performed at 0%, 50%, 70%, 80%, 90%, 95%, 98% and 99% relative humidities (RH) while the MERRA satellite data were extracted at an average of 78% relative humidity. results based on α values showed that OPAC was only able to simulate well the insoluble and soot aerosol particle size distributions of India’s urban atmosphere such that it had approximately the same insoluble and soot aerosol particle size distributions as India. For the rest of the nine countries (USA, Brazil, Indonesia, China, Japan, Mexico, Nigeria, Pakistan and Ethiopia), OPAC was seen to either overestimate or underestimate water soluble, insoluble and soot aerosol particle size distributions. For visibility and water soluble or insoluble aerosol concentrations, OPAC showed good simulated values that were approximately the same as those found within Ethiopia’s and Japan’s urban atmosphere. OPAC also had visibility value and insoluble aerosol concentration that were approximately the same as those found within China’s atmosphere. For all other countries (India, USA, Brazil, Indonesia, Mexico, Nigeria and Pakistan) OPAC either overestimated their visibilities and underestimated their water soluble, insoluble and soot aerosol concentrations or vice versa. With both OPAC and MERRA, the presence of fine mode aerosol particles in an urban atmosphere was established with α values > 1. But MERRA also showed otherwise for three countries (Nigeria, Ethiopia and Pakistan) that had α values < 1 which implied the presence of coarse mode aerosol particles. The relationship between visibility and α satisfied the direct power law for OPAC, for MERRA the relationship approximately satisfied the power law for most of the countries.

Year-round observations of stable carbon isotopic composition of carboxylic acids, oxoacids and α-Dicarbonyls in fine aerosols at Tianjin, North China: Implications for origins and aging

To better understand the origins and photochemical processing (aging) of organic aerosols (OA), we studied fine aerosols (PM2.5) collected at urban (Nankai District (ND)) and suburban (Haihe Education Park (HEP)) Tianjin, North China over a one-year period (2018–2019) for stable carbon isotopic composition (δ13C) of water-soluble diacids, oxoacids, α-dicarbonyls and fatty acids. Maleic (M, −18.3 ± 10.9‰ at ND and −23.5 ± 10.2‰ at HEP) and fumaric (F, −22.0 ± 12.1‰ at ND and −22.5 ± 10.5‰ at HEP) acids were found to be most enriched with 13C followed by oxalic acid (C2, −24.7 ± 3.9‰ at ND and −25.9 ± 4.7‰ at HEP) during the campaign. Based on seasonal changes in δ13C of selected marker species: C6 and C9 diacids, phthalic, glyoxylic and pyruvic acids and glyoxal, and their comparison with the source signatures, we found that water-soluble OA in Tianjin were mainly originated from fossil fuel combustion and biomass burning emissions and were subjected for significant aging. The contribution from fossil fuel combustion including coal combustion was high in autumn and winter, especially at ND. Considering the enrichment of 13C in specific species together with linear relations of δ13C of selected species with their concentrations, with mass ratios and with the relative abundance of C2 diacid, we inferred that the photochemical transformations of longer-chain diacids, oxidation of α-dicarbonyls (Gly and mGly), preferably in gas phase, were important in warm period (March–September), whereas the oxidation of Gly, mGly and other precursors in aqueous phase were major in cold period (October–February).

Robust Evidence of 14C, 13C, and 15N Analyses Indicating Fossil Fuel Sources for Total Carbon and Ammonium in Fine Aerosols in Seoul Megacity.

Carbon- and nitrogen-containing aerosols are ubiquitous in urban atmospheres and play important roles in air quality and climate change. We determined the 14C fraction modern (fM) and δ13C of total carbon (TC) and δ15N of NH4+ in the PM2.5 collected in Seoul megacity during April 2018 to December 2019. The seasonal mean δ13C values were similar to −25.1‰ ± 2.0‰ in warm and −24.2‰ ± 0.82‰ in cold seasons. Mean δ15N values were higher in warm (16.4‰ ± 2.8‰) than in cold seasons (4.0‰ ± 6.1‰), highlighting the temperature effects on atmospheric NH3 levels and phase-equilibrium isotopic exchange during the conversion of NH3 to NH4+. While 37% ± 10% of TC was apportioned to fossil-fuel sources on the basis of fM values, δ15N indicated a higher contribution of emissions from vehicle exhausts and electricity generating units (power-plant NH3 slip) to NH3: 60% ± 26% in warm season and 66% ± 22% in cold season, based on a Bayesian isotope-mixing model. The collective evidence of multiple isotope analysis reasonably supports the major contribution of fossil-fuel-combustion sources to NH4+, in conjunction with TC, and an increased contribution from vehicle emissions during the severe PM2.5 pollution episodes. These findings demonstrate the efficacy of a multiple-isotope approach in providing better insight into the major sources of PM2.5 in the urban atmosphere.

Characterization of Aerosol Pollution in Two Hungarian Cities in Winter 2009–2010

In this study, atmospheric particulate matter (APM) pollution was compared in urban background sites of two cities in Hungary—namely the capital Budapest and Debrecen—by analyzing daily aerosol samples collected between 8 December 2009 and 18 March 2010. Concentration, elemental composition, including BC, and sources of fine (PM2.5) and coarse (PM2.5–10) aerosol pollution, as well as their variation due to meteorological conditions and anthropogenic activities, were determined for both cities. The average PM2.5 concentrations were 22 μg/m3 and 17 μg/m3 in Budapest and Debrecen, respectively. In the case of PM10, the mean concentration was 32 μg/m3 in Budapest and 23 μg/m3 in Debrecen. The concentration of the coarse fraction decreased significantly over the weekends compared to working days. The number of exceedances of the WHO recommended limit value for PM2.5 (15 μg/m3) were 67 in Budapest and 46 in Debrecen, which corresponds to 73% and 50% of the sampling days, respectively. At the time of the exceedances the daily average temperature was below freezing. The average PM2.5/PM10 ratio was 70% and 75% for the two sites, indicating the dominance of the fine fraction aerosol particles during the study period. Elements of natural origin (Al, Si, Ca, Ti, Mn, Fe, Ba) and chlorine were found to be dominant in the coarse fraction, while elements of anthropogenic origin (S, K, Cu, Zn, Pb) were characteristic to the fine fraction. Similar concentrations were measured in the two cities in the case of S which originates from regional transport and K which serves as a tracer for biomass combustion. Traffic-related elements were present in 2–3 times higher concentrations in Budapest. The episodic peaks in the Cl time series could be attributed to salting after snowfalls. The following sources of APM pollution were identified by using the EPA Positive Matrix Factorization (PMF) 5.0 receptor model: soil, traffic, road dust, secondary sulfate, biomass burning, and de-icing of streets. On polluted days when the PM2.5 concentration exceeded the 25 μg/m3 value the contribution of secondary sulfate, domestic heating, and traffic increased significantly compared to the average. On weekends and holidays the contribution of soil and traffic decreased. The main pollution sources and their contributions were similar to the ones in other cities in the region. Comparing our findings to results from winter 2015 it can be concluded that while the PM2.5 pollution level remained almost the same, a significant increase in the contribution of biomass burning was observed in both cities from 2010 to 2015, indicating a change of heating habits.

Trends in the types and absorption characteristics of ambient aerosols over the Indo-Gangetic Plain and North China Plain in last two decades

The sixth assessment report released by the Intergovernmental Panel on Climate Change (IPCC) in 2021 states that our inadequate understanding of magnitudes and trends of atmospheric aerosols, particularly over Asia, is a major source of uncertainty in climate change. In this study, the climatology and trends in different types of aerosols with focus on absorbing aerosols over Kanpur located in the Indo-Gangetic Plain (IGP) in South Asia and Beijing in the North China Plain (NCP) in East Asia are derived for the first time. We perform a first analysis of high-quality time series of columnar aerosols observations over a period of nearly two-decades, along with satellite observations to provide a broader regional perspective. The satellite retrieved aerosol Ångström exponent (AE) values have increased (10–20%) suggesting an increasing contribution of fine aerosols to aerosol optical depth (AOD) over Asia in last 2-decades. Among the three aerosol types [urban-industrial (UI), biomass burning (BB), and dust (DU)], only UI and BB aerosols are present over Kanpur throughout the year, while DU is present along with UI and BB aerosols only during pre-monsoon and monsoon. Overall, there is a positive trend in BB aerosols over both Kanpur and Beijing, a positive (negative) trend in UI aerosols over Kanpur (Beijing), and positive (negative) trend in dust over Beijing (Kanpur). However, only the positive trend in BB aerosol type over Kanpur is statistically significant. Further, among the three absorbing aerosol types [mostly black carbon (MBC), mostly dust (MDU), and mixed (MIX) containing BC and dust], only MBC and MIX are present in post-monsoon and winter over IGP, and MDU is present along with MBC and MIX only during pre-monsoon and monsoon, which is in agreement with aerosol types found. Trends in MBC, MIX and MDU over Kanpur in IGP and in MIX over Beijing are statistically significant. These trends are attributed mainly to the changes in anthropogenic aerosol emissions, and not to natural and climatic factors as their changes are relatively small. These findings on hitherto unavailable climatology and trends in aerosols and absorbing aerosols over two global aerosol hotspots and identified contrasts will be crucial in model simulations to better decipher the aerosol-climate interactions over Asia.

The effect of aerosol size on Fe solubility and deposition flux: A case study in the East China Sea

Aerosol sizes are highly associated with the solubilities and the deposition fluxes of aerosol Fe in the surface ocean since the sizes may reflect the sources and decide the deposition velocities. However, systematic studies for the association of the solubilities and fluxes have been limited. In this study, five size-fractions of dry aerosols were collected monthly for a year at two islets in the East China Sea, where large amounts of both fine anthropogenic and coarse lithogenic aerosols deposit. Both pure water and buffer leached methodologies were applied to determine the two operationally defined dissolvable Fe fractions, instantly dissolved Fe (DFe) and supposedly Fe-ligand complexed labile Fe (LFe), respectively. We found that the solubilities of DFe varied up to 4 orders of magnitude with the size spectrum and exhibited a highly linear correlation with non-sea-salt sulfur, indicating that the solubilities of DFe were closely associated with the acidity. Finer aerosols (PM 3) accounted for 90% of total DFe but coarser aerosols (>PM 3) contributed 66% of the difference between LFe and DFe (LFe-DFe). The increasing trend of the difference with increasing sizes indicates that the residence time of coarse aerosol particles and their interaction with Fe-ligands are critical factors deciding the total fluxes of LFe in the ocean. Considering the deposition velocities of each size of aerosols, the averaged fluxes of aerosol Fe of the fine and coarse aerosols were 1.8 and 5.9 nmol m−2 d−1 for DFe; and 2.8 and 62 nmol m−2 d−1 for LFe in the East China Sea, respectively. Attributed to the relatively low deposition velocities of fine aerosols, we found that either single or two averaged deposition velocities (fine/coarse) that were used in most of the previous studies would significantly overestimate dissolvable Fe fluxes in regions where the contribution of fine anthropogenic aerosols is dominant, such as the open ocean. In conclusion, this study demonstrates that aerosol sizes are essential and powerful parameters to accurately estimate the solubility and the fluxes of aerosol dissolvable Fe.

Characterization, source apportionment and associated health risk assessment of respirable air particulates in Metro Manila, Philippines

Coarse (PM10) and fine (PM2.5) aerosols were sampled from June to November 2016 at three different sites in Metro Manila Philippines (Valenzuela, NAMRIA, and MMDA). PM2.5 average levels in all sites exceeded the World Health Organization annual and daily limits, indicating that the ambient air qualities in all sites were unhealthy. Black Carbon (BC), a fingerprint of incomplete combustion, constituted 31–46% of PM2.5. Multi-element analysis of PM indicated that the sulfur, lead, and zinc had substantial contributions to PM2.5, with the highest level found in Valenzuela. Receptor modeling highlighted six important sources: vehicular emissions, biomass burning, industrials, secondary sulfur, sea spray, and fine soil. Among the sources, vehicular emission was the most dominant source, comprising 20–35% of the apportioned sources. An industrial source, predominantly with Zn and Pb, was seen in Valenzuela, contributing about 5.4% of its PM2.5. The health risks of fine aerosol, BC, and major elements were evaluated also in this study. Elements studied showed negligible potential (HQ < 1) to cause non-carcinogenic health effects and very low (<1 × 10−6) carcinogenic health effects to children and adults. The observed trend for carcinogenic risks of PM2.5 in children was Valenzuela > MMDA > NAMRIA while a medium carcinogenic risk was observed for adults at all sites (CR > 1 × 10−5). The trend for PM2.5 average HQ values in both age groups was Valenzuela > MMDA > NAMRIA. Our results showcased varying levels and sources of PM and its components that can impact the health upon exposure and should be addressed in future policies to safeguard public health.

Wintertime haze and ozone at Dinosaur National Monument

ABSTRACT Dinosaur National Monument (DINO) is located near the northeastern edge of the Uinta Basin and often experiences elevated levels of wintertime ground-level ozone. Previous studies have shown that high ozone mixing ratios in the Uinta Basin are driven by elevated levels of volatile organic compounds (VOCs) and nitrogen oxides (NOx) from regional oil and gas development coupled with temperature inversions and enhanced photochemistry from persistent snow cover. Here, we show that persistent snow cover and temperature inversions, along with abundant ammonia, also lead to wintertime haze in this region. A study was conducted at DINO from November 2018 through May 2020 where ozone, speciated fine and coarse aerosols, inorganic gases, and VOCs were measured. Three National Ambient Air Quality Standards (NAAQS) ozone exceedances were observed in the first winter, and no exceedances were observed in the second winter. In contrast, elevated levels of particulate matter were observed both winters, with 24-h averaged particle light extinction exceeding 100 Mm−1. These haze events were dominated by ammonium nitrate, and particulate organics were highly correlated with ammonium nitrate. Ammonium nitrate formation was limited by nitric acid in winter. As such, reductions in regional NOx emissions should reduce haze levels and improve visibility at DINO in winter. Long-term measurements of particulate matter from nearby Vernal, Utah, suggest that visibility impairment is a persistent issue in the Uinta Basin in winter. From April through October 2019, relatively clean conditions occurred, with average particle extinction of ~10 Mm−1. During this period, ammonium nitrate concentrations were lower by more than an order of magnitude, and contributions from coarse mass and soil to haze levels increased. VOC markers indicated that the high levels of observed pollutants in winter were likely from local sources related to oil and gas extraction activities. Implications: Elevated ground-level ozone and haze levels were observed at Dinosaur National Monument in winter. Haze episodes were dominated by ammonium nitrate, with 24-h averaged particle light extinction exceeding 100 Mm−1, reducing visual range near the surface to ~35 km. Despite elevated ammonium nitrate concentrations, additional gas-phase ammonia was available, such that any increase in NOx emissions in the region is likely to lead to even greater haze levels.

Monsoon-seasonal validation of MODIS aerosol optical depth and characterization using AERONET observation retrieve over Italy.

This study used Angstrom Exponent (AE) relationship with Aerosol Optical Depth (AOD) obtained from space-based direct sky-radiometer of Moderate Resolution Imaging Spectroradiometer (MODIS) and direct Sun algorithm surface-based AERONET network (level 2.0 version 3) to evaluate monsoon season (June-September) aerosol optical depth and characterization at 7 Italy sites: IMAA_POTENZA (40.60N, 15.72E), ISPRA (45.80N, 8.62E), LAMPEDUSA (35.51N, 12.63E), MESSINA (38.19N, 15.56E), MODENA (44.63N, 10.94E), ROME_TOR_VERGATA (41.83N, 12.64E) and VENISE (45.31N, 12.50E) from 2010 to 2019. Standardized anomaly and the standard deviation ratio method of analysis to address the robustness of AE were identified to classify aerosols typing. The extracted monsoon AOD correlation between MODIS and AERONET is (r=0.95) which is plausible to determine discrepancy in data handling. In order to remove large influence of annual cycle, the data were first detrend. The results show that standard deviation value>1 indicates monthly dominance than climatology. The standardized anomaly records (-0.22±0.13) for MODIS and AERONET AODs with corresponding correlation of (r=0.96) in June. There is disparity in AOD data handling from MODIS in some periods, which could attribute that space-based interpretation, should be validated with ground-base observation over Italy. The fine mode aerosols due to high AE values interestingly present the characteristic of AOD dominance, but experience trans-seasonal change, where MODIS has weak correlation.

Airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Hospitals: Effects of Aerosol-Generating Procedures, HEPA-Filtration Units, Patient Viral Load, and Physical Distance.

BackgroundTransmission of coronavirus disease 2019 (COVID-19) can occur through inhalation of fine droplets or aerosols containing infectious virus. The objective of this study was to identify situations, patient characteristics, environmental parameters, and aerosol-generating procedures (AGPs) associated with airborne severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus.MethodsAir samples were collected near hospitalized COVID-19 patients and analyzed by RT-qPCR. Results were related to distance to the patient, most recent patient diagnostic PCR cycle threshold (Ct) value, room ventilation, and ongoing potential AGPs.ResultsIn total, 310 air samples were collected; of these, 26 (8%) were positive for SARS-CoV-2. Of the 231 samples from patient rooms, 22 (10%) were positive for SARS-CoV-2. Positive air samples were associated with a low patient Ct value (OR, 5.0 for Ct <25 vs >25; P = .01; 95% CI: 1.18–29.5) and a shorter physical distance to the patient (OR, 2.0 for every meter closer to the patient; P = .05; 95% CI: 1.0–3.8). A mobile HEPA-filtration unit in the room decreased the proportion of positive samples (OR, .3; P = .02; 95% CI: .12–.98). No association was observed between SARS-CoV-2–positive air samples and mechanical ventilation, high-flow nasal cannula, nebulizer treatment, or noninvasive ventilation. An association was found with positive expiratory pressure training (P < .01) and a trend towards an association for airway manipulation, including bronchoscopies and in- and extubations.ConclusionsOur results show that major risk factors for airborne SARS-CoV-2 include short physical distance, high patient viral load, and poor room ventilation. AGPs, as traditionally defined, seem to be of secondary importance.

Distribution and sources of SVOCs in fine and coarse aerosols in the megacity of Istanbul

Approximately 15.4 million people are continuously exposed to various air pollutants in the megacity of Istanbul. Anthropogenic activities in Istanbul generate emissions from mobile sources (i.e., vehicles, aircraft, ships, etc.) and stationary sources such as industrial and residential heating emissions. Biogenic emissions and long-range transport such as desert dust from Sahara and pollutants from Balkan countries also contribute to the local air pollution in Istanbul. In this work, fine (Dp < 2.5 μm) and coarse (Dp > 2.5 μm) particles were collected with a high-volume sampler during four seasons of the period Jan 2017 - Jan 2018. A total of 15 PAHs and 28 n-alkanes were identified and quantified with a newly developed thermal desorption – gas chromatography with mass spectrometry method (TD-GC–MS). Source analysis was performed with PAH and n-alkane diagnostic ratios, and source apportionment was performed with principal component analysis. The yearly averages of PAHs and n-alkanes in the fine fraction were 21.6 ng m−3 and 103.8 ng m−3, with daily averages of 7.1–80.8 ng m−3 and 55.3–204.2 ng m−3, respectively. Approximately 90% of the PAHs and n-alkanes were found in the fine PM fraction in this traffic site. The BaP carcinogenic (BaP-TEQ) and mutagenic (BaP-MEQ) equivalents were on average 5.47 ± 0.64 and 4.72 ± 0.8 ng m−3 in the fine fraction, respectively, and were approximately 6–7 times lower in the coarse fraction. This has important implications due to the respirable nature of fine aerosols and their longer lifetimes in the atmosphere. Multivariate analysis coupled with principal component analysis led to an important result that the organic aerosol mainly originates from two local sources: road traffic (50.4%) and shipping emissions (26.6%). The results found in this work indicate the urgent need for the application of mitigation measures to control road traffic and minimize the emissions from ships passing through the İstanbul Bosphorus.

On the Speciation of Iodine in Marine Aerosol.

We have compiled and analyzed a comprehensive data set of field observations of iodine speciation in marine aerosol. The soluble iodine content of fine aerosol (PM1) is dominated by soluble organic iodine (SOI; ∼50%) and iodide (∼30%), while the coarse fraction is dominated by iodate (∼50%), with nonnegligible amounts of iodide (∼20%). The SOI fraction shows an equatorial maximum and minima coinciding with the ocean “deserts,” which suggests a link between soluble iodine speciation in aerosol and ocean productivity. Among the major aerosol ions, organic anions and non‐sea‐salt sulfate show positive correlations with SOI in PM1. Alkali cations are positively correlated to iodate and negatively correlated with SOI and iodide in coarse aerosol. These relationships suggest that under acidic conditions iodate is reduced to HOI, which reacts with organic matter to form SOI, a possible source of iodide. In less acidic sea‐salt or dust‐rich coarse aerosols, HOI oxidation to iodate and reaction with organic matter likely compete.

Evaluating the PurpleAir monitor as an aerosol light scattering instrument

Abstract. The Plantower PMS5003 sensors (PMS) used in the PurpleAir monitor PA-II-SD configuration (PA-PMS) are equivalent to cell-reciprocal nephelometers using a 657 nm perpendicularly polarized light source that integrates light scattering from 18 to 166∘. Yearlong field data at the National Oceanic and Atmospheric Administration's (NOAA) Mauna Loa Observatory (MLO) and Boulder Table Mountain (BOS) sites show that the 1 h average of the PA-PMS first size channel, labeled “&gt; 0.3 µm” (“CH1”), is highly correlated with submicrometer aerosol scattering coefficients at the 550 and 700 nm wavelengths measured by the TSI 3563 integrating nephelometer, from 0.4 to 500 Mm−1. This corresponds to an hourly average submicrometer aerosol mass concentration of approximately 0.2 to 200 µg m−3. A physical–optical model of the PMS is developed to estimate light intensity on the photodiode, accounting for angular truncation of the volume scattering function as a function of particle size. The model predicts that the PMS response to particles &gt; 0.3 µm decreases relative to an ideal nephelometer by about 75 % for particle diameters ≥ 1.0 µm. This is a result of using a laser that is polarized, the angular truncation of the scattered light, and particle losses (e.g., due to aspiration) before reaching the laser. It is shown that CH1 is linearly proportional to the model-predicted intensity of the light scattered by particles in the PMS laser to its photodiode over 4 orders of magnitude. This is consistent with CH1 being a measure of the scattering coefficient and not the particle number concentration or particulate matter concentration. The model predictions are consistent with data from published laboratory studies which evaluated the PMS against a variety of aerosols. Predictions are then compared with yearlong fine aerosol size distribution and scattering coefficient field data at the BOS site. Field data at BOS confirm the model prediction that the ratio of CH1 to the scattering coefficient would be highest for aerosols with median scattering diameters &lt; 0.3 µm. The PMS detects aerosols smaller than 0.3 µm diameter in proportion to their contribution to the scattering coefficient. The results of this study indicate that the PMS is not an optical particle counter and that its six size fractions are not a meaningful representation of particle size distribution. The relationship between the PMS 1 h average CH1 and bsp1, the scattering coefficient in Mm−1 due to particles below 1 µm aerodynamic diameter, at wavelength 550 nm, is found to be bsp1 = 0.015 ± 2.07 × 10−5 × CH1, for relative humidity below 40 %. The coefficient of determination r2 is 0.97. This suggests that the low-cost and widely used PA monitors can be used to measure and predict the submicron aerosol light scattering coefficient in the mid-visible nearly as well as integrating nephelometers. The effectiveness of the PA-PMS to serve as a PM2.5 mass concentration monitor is due to both the sensor behaving like an imperfect integrating nephelometer and the mass scattering efficiency of ambient PM2.5 aerosols being roughly constant.