Ambient volatile organic compounds in the Seoul metropolitan area of South Korea: Chemical reactivity, risks and source apportionment.

The chemical reactivity, contribution of emission sources, and risk assessment of volatile organic compounds (VOCs) in the atmosphere of the Seoul metropolitan area (SMA) were analyzed. Datasets collected from 6 photochemical assessment monitoring stations (PAMS) of SMA from 2018 to 2021 were used. Alkenes and aromatics contributed significantly to ozone formation relative to the emission concentrations, and aromatics accounted for most of the secondary organic aerosols (SOA) formation in the SMA. The contributions of ozone and SOA formation were found to be notably higher at measurement stations in residential areas such as Guwol (GW) and Sosabon (SS) compared to other measurement stations. From the results of an emission source analysis, it was confirmed that anthropogenic sources such as combustion sources, vehicle exhaust, fuel evaporation, and solvent use had a significant effect at all measurement stations. Assessing the health risk, non-carcinogenic compounds were at acceptable level at all measurement stations. On the other hand, carcinogenic compounds were approaching risk level (10-4), thereby demanding immediate attention. The level of exposure to carcinogenic compounds increased by age group, and male was more vulnerable than female. It was found that SS had the highest level of exposure to carcinogens in the atmosphere of the population ages 60 or older. The health threat of the SMA population is expected due to direct exposure from inhalation of ambient toxic compounds and indirect exposure from ozone and PM2.5 formations through oxidation of VOCs. This study emphasizes the importance of addressing specific emission sources within the metropolitan area and developing comprehensive regional strategies to mitigate VOCs.

Development of PM10 and PM2.5 cyclones for small sampling ports at stationary sources: Numerical and experimental study.

Air pollution caused by particulate matter (PM) has become a serious issue, and significant research has focused on managing large stationary emission sources, i.e., the primary sources of PM. Currently, the U.S. Environmental Protection Agency (EPA) Method 201A and ISO 23210 are predominantly employed to measure the PM emissions at large stationary sources. Method 201A is designated as a standard test method in Korea, but it is difficult to measure PM10 and PM2.5 simultaneously owing to the size of the full-set cyclone. In large stationary emission sources, the use of a serial connection of PM10 and PM2.5 cyclones is unsuitable for measurements at conventional sampling ports featuring diameters of approximately 100 mm. Therefore, in this study, PM10 and PM2.5 cyclones were developed to replace the cyclones currently used in Method 201A. The developed cyclones featured a cutoff diameter, which was confirmed by numerical and experimental analyses that were close to Method 201A. Moreover, there was an increase in the stiffness of collection efficiency. The hook adaptor, which is a key accessory used in Method 201A, was found to be applicable to the newly developed cyclones. This alternative method will help reduce the measurement time by simultaneously measuring TSP, PM10, and PM2.5 and eliminates the costs of installing or refurbishing additional sampling ports at existing large stationary sources.

Study of stainless steel electrodes after electrochemical analysis in sea water condition.

For water electrolysis, a rare earth material (eg., platinum) is often used as an electrode, but because of the high cost and toxicity of chemicals, researchers are searching for cost effective and eco-friendly alternative materials. Various alloys and metals have been long explored for use as electrode materials in different media. Stainless steel (SS 304) electrodes are cost effective and have a large surface area; further their catalytic performance is comparable to that of carbon coated noble metals cathodes. Stainless steel has good mechanical properties and durability so it is widely used in desalination plants, oil and gas industries, ship building, etc. However, over a period of time it corrodes very quickly in saline water. To improve the stability and durability of the electrodes (i.e., to minimize corrosion), we anneal the samples under two different sets of conditions and test the electrodes in 3.5% NaCl solution. The anodic peak (-0.25 V) observed for bare stainless steel result from the formation of iron (II) hydroxide [Fe(OH)2]. The Raman bands observed at 210 and 274 cm-1 for bare stainless steel result from the formation of α-Fe2O3 owing to partial, anodic, and cathodic reactions occurring on the electrode which disrupts the surface layers. High intensity X-ray diffraction (XRD) and Raman peaks of Cr2O3 and MnCr2O4 observed in argon and hydrogen annealed sample after cyclic voltammetry reveal that this sample is more stable than bare and air annealed samples. XRD reveals mixed oxide phases in addition to eskolaite and magnetite phases. Scanning electron microscope (SEM) images show that although the air-annealed sample has a soft, spongy structure, Na and Cl ions are adsorbed in the voids on the outer surface of the electrode leading to quick degradation. For the air-annealed sample the oxide appears to adhere poorly to the stainless steel. Oxygen (ie., oxide composition) may play a key role in adherence and growth of Cr2O3 formed at high temperature. X-ray photoelectron spectroscopy (XPS) reveals that large amounts of Cr and Mn are dissolved/corroded into the electrolyte for air annealed sample which is in good agreement with the Raman and SEM results.

Determination of the emission rate for ultrafine and accumulation mode particles as a function of time during the pan-frying of fish.

Particulate matter (PM) from cooking is considered one of the most harmful indoor air pollutants causing numerous adverse health effects, and it is essential to comprehend the characteristics of the particles generated from cooking to prevent these problems. In this study, we investigated PM from the pan-frying of salmon using number concentration and developed emission rates as a function of time for ultrafine particles (UFPs < 100 nm) and accumulation mode particles (AMPs 0.1-1 µm). The newly defined emission rates vary significantly with time and are very different from the conventionally determined rates that do not consider the variation of particle concentration with time. The emission rate of UFPs decreased over time after a sharp rise, whereas that of AMPs continued to increase, resulting in a change in the proportions of UFPs and AMPs in the total PM from 93 to 7% to 72 and 28%, respectively. Particle-particle interactions such as coagulation and coalescence were observed between primary particles via high resolution transmission electron microscopy (HR-TEM), which is a plausible reason for the decreasing emission rate of UFPs with time. The emission rate as a function of time can serve as a tool to estimate PM from cooking, as well as to monitor the change trends through phenomena such as agglomeration.

Hygroscopic Properties and Respiratory System Deposition Behavior of Particulate Matter Emitted By Mining and Smelting Operations.

This study examines size-resolved physicochemical data for particles sampled near mining and smelting operations and a background urban site in Arizona with a focus on how hygroscopic growth impacts particle deposition behavior. Particles with aerodynamic diameters between 0.056-18 µm were collected at three sites: (i) an active smelter operation in Hayden, AZ, (ii) a legacy mining site with extensive mine tailings in Iron King, AZ, and (iii) an urban site, inner-city Tucson, AZ. Mass size distributions of As and Pb exhibit bimodal profiles with a dominant peak between 0.32 and 0.56 µm and a smaller mode in the coarse range (>3 µm). The hygroscopicity profile did not exhibit the same peaks owing to dependence on other chemical constituents. Submicrometer particles were generally more hygroscopic than supermicrometer ones at all three sites with finite water-uptake ability at all sites and particle sizes examined. Model calculations at a relative humidity of 99.5% reveal significant respiratory system particle deposition enhancements at sizes with the largest concentrations of toxic contaminants. Between dry diameters of 0.32 and 0.56 µm, for instance, ICRP and MPPD models predict deposition fraction enhancements of 171%-261% and 33%-63%, respectively, at the three sites.

Evidence of aqueous secondary organic aerosol formation from biogenic emissions in the North American Sonoran Desert.

This study examines the role of aqueous secondary organic aerosol formation in the North American Sonoran Desert as a result of intense solar radiation, enhanced moisture, and biogenic volatile organic compounds (BVOCs). The ratio of water-soluble organic carbon (WSOC) to organic carbon (OC) nearly doubles during the monsoon season relative to other seasons of the year. When normalized by mixing height, the WSOC enhancement during monsoon months relative to preceding dry months (May-June) exceeds that of sulfate by nearly a factor of 10. WSOC:OC and WSOC are most strongly correlated with moisture parameters, temperature, and concentrations of O3 and BVOCs. No positive relationship was identified between WSOC or WSOC:OC and anthropogenic tracers such as CO over a full year. This study points at the need for further work to understand the effect of BVOCs and moisture in altering aerosol properties in understudied desert regions.

α-Fe2O3 nanoparticles and hazardous air pollutants release during cooking using cast iron wok in a commercial Chinese restaurant.

Long-term exposure to fine particles (PM2.5), ultrafine particles (UFPs), and volatile organic compounds (VOCs) emissions from cooking has been linked to adverse human health effects. Here, we measured the real-time number size distribution of particles emitted when cooking two served food in Chinese restaurants and estimated the emission rate of UFPs and PM2.5. Experiments were conducted under a control hood, and both online measurement and offline analysis of PM2.5 were carried out. The measured emission rates of PM2.5 generated from deep-frying and grilling were 0.68 ± 0.11 mg/min and 1.58 ± 0.25 mg/min, respectively. Moreover, the UFPs emission rate of deep-frying (4.3 × 109 #/min) is three times higher than that of grilling (1.4 × 109 #/min). Additionally, the PM2.5 emission of deep-frying was comprised of a considerable amount of α-Fe2O3 (5.7% of PM2.5 total mass), which is more toxic than other iron oxide species. A total of six carcinogenic HAPs were detected, among which formaldehyde, acrolein, and acetaldehyde were found to exceed the inhalation reference concentration (RfC) for both cooking methods. These findings can contribute to future evaluation of single particle and HAPs emission from cooking to better support toxicity assessment.

Analysis of VOCs Emitted from Small Laundry Facilities: Contributions to Ozone and Secondary Aerosol Formation and Human Risk Assessment.

Volatile organic compounds (VOCs) emitted to the atmosphere form ozone and secondary organic aerosols (SOA) by photochemical reactions. As they contain numerous harmful compounds such as carcinogens, it is necessary to analyze them from a health perspective. Given the petroleum-based organic solvents used during the drying process, large amounts of VOCs are emitted from small laundry facilities. In this study, a laundry facility located in a residential area was selected, while VOCs data emitted during the drying process were collected and analyzed using a thermal desorption-gas chromatography/mass spectrometer (TD-GC/MS). We compared the results of the solvent composition, human risk assessment, contribution of photochemical ozone creation potential (POCP), and secondary organic aerosol formation potential (SOAP) to evaluate the chemical species. Alkane-based compounds; the main components of petroleum organic solvents, were dominant. The differences in evaporation with respect to the boiling point were also discerned. The POCP contribution exhibited the same trend as the emission concentration ratios for nonane (41%), decane (34%), and undecane (14%). However, the SOAP contribution accounted for o-xylene (28%), decane (27%), undecane (25%), and nonane (9%), thus confirming the high contribution of o-xylene to SOA formation. The risk assessment showed that acrylonitrile, carbon tetrachloride, nitrobenzene, bromodichloromethane, and chloromethane among carcinogenic compounds, and bromomethane, chlorobenzene, o-xylene, and hexachloro-1, 3-butadiene were found to be hazardous, thereby excessing the standard value. Overall these results facilitate the selection and control of highly reactive and harmful VOCs emitted from the dry-cleaning process.

Hygroscopic and Chemical Properties of Aerosol Emissions at a Major Mining Facility in Iran: Implications for Respiratory Deposition.

This study characterizes the hygroscopic and chemical nature of aerosols originating from ten locations (4 outdoors and 6 indoors) around the Gol-E-Gohar (GEG) iron ore mine (Iran), including an assessment of how hygroscopic growth alters particulate deposition in the respiratory system. Aerosols collected on filters in three diameter (Dp) ranges (total suspended particulates [TSP], Dp ≤ 10 µm [PM10], and Dp ≤ 2.5 µm [PM2.5]) were analyzed for chemical and hygroscopic characteristics. The water-soluble aerosol composition is dominated by species associated with directly emitted crustal matter such as chloride, sodium, calcium, and sulfate. There was minimal contribution from organic acids and other secondarily formed species such as inorganic salts. Aerosol growth factors at 90% relative humidity varied between 1.39 and 1.72 and exceed values reported for copper mines in the United States where similar data are available. Values of the hygroscopicity parameter kappa (0.19 to 0.45) were best related to the mass fraction of chloride among all the studied species. Kappa values were generally similar when comparing the three types of samples (TSP, PM2.5, PM10) at each site and also when comparing each of the ten sampling sites. Accounting for hygroscopic growth yields an increase in the deposition fraction for aerosols with a dry Dp between 0.2 and 2 µm based on International Commission on Radiological Protection model calculations, with more variability when examining each of the three individual head airway regions.

Pd Nanocluster/Monolayer MoS2 Heterojunctions for Light-Induced Room-Temperature Hydrogen Sensing.

Developing sensing approaches that can exploit visible light for the detection of low-concentration hydrogen at room temperatures has become increasingly important for the safe use of hydrogen in many applications. In this study, heterostructures composed of monolayer MoS2 and Pd nanoclusters (Pd/MoS2) acting as photo- and hydrogen-sensitizers are successfully fabricated in a facile and scalable manner. The uniform deposition of morphologically isotropic Pd nanoclusters (11.5 ± 2.2 nm) on monolayer MoS2 produces a plethora of active heterojunctions, effectively suppressing charge carrier recombination under light illumination. The dual photo- and hydrogen-sensitizing functionality of Pd/MoS2 can enable its use as an active sensing layer in optoelectronic hydrogen sensors. Gas-sensing examinations reveal that the sensing performance of Pd/MoS2 is enhanced three-fold under visible light illumination (17% for 140 ppm of H2) in comparison with dark light (5% for 140 ppm of H2). Photoactivation is also found to enable excellent sensing reversibility and reproducibility in the obtained sensor. As a proof-of-concept, the integration of Pd nanoclusters and monolayer MoS2 can open a new avenue for light-induced hydrogen gas sensing at room temperature.

Quantification of tire wear particles in road dust from industrial and residential areas in Seoul, Korea.

In this study, we examined tire and road wear microparticles (TRWMPs) in road dust along the Seoul metropolitan area, from industrial and residential areas. The road dust samples were collected via vacuum sweep methods and then filtered to obtain particles with diameters less than 75 µm. To quantify the TRWMPs in road dust, we used the raw materials of tire components, natural rubber (NR), and styrene-butadiene rubber (SBR), as standard materials. We evaluated the usability of the pyrolyzer-gas chromatography/mass spectrometry py-GC/MS method introduced in ISO/TS 20593 by confirming the decomposition temperatures of the NR and SBR by thermogravimetric (TG) and evolved gas analysis (EGA)-MS. The average of TRWMPs in industrial and residential area road dust were 22,581 and 9818 µg/g, respectively, indicating that the industrial area has 2.5 times higher TRWMPs concentration. Further, the NR, the main component of truck bus radial, to SBR, the main component of passenger car radial, ratio was slightly higher in the industrial area than in the residential area. This presumably means that the high traffic volume, including heavy duty vehicles in industrial areas, affected the higher concentration of TRWMPs. This study reveals the growing evidence of the importance of TRWMPs in road dust and how TRWMPs quantity can impact the air quality of the Seoul metropolitan area.

Relationship between Cytotoxicity and Surface Oxidation of Artificial Black Carbon.

The lacking of laboratory black carbon (BC) samples have long challenged the corresponding toxicological research; furthermore, the toxicity tests of engineered carbon nanoparticles were unable to reflect atmospheric BC. As a simplified approach, we have synthesized artificial BC (aBC) for the purpose of representing atmospheric BC. Surface chemical properties of aBC were controlled by thermal treatment, without transforming its physical characteristics; thus, we were able to examine the toxicological effects on A549 human lung cells arising from aBC with varying oxidation surface properties. X-ray photoelectron spectroscopy, as well as Raman and Fourier transform infrared spectroscopy, verified the presence of increased amounts of oxygenated functional groups on the surface of thermally-treated aBC, indicating aBC oxidization at elevated temperatures; aBC with increased oxygen functional group content displayed increased toxicity to A549 cells, specifically by decreasing cell viability to 45% and elevating reactive oxygen species levels up to 294% for samples treated at 800 °C.

Prediction Model for Dry Eye Syndrome Incidence Rate Using Air Pollutants and Meteorological Factors in South Korea: Analysis of Sub-Region Deviations.

Here, we develop a dry eye syndrome (DES) incidence rate prediction model using air pollutants (PM10, NO2, SO2, O3, and CO), meteorological factors (temperature, humidity, and wind speed), population rate, and clinical data for South Korea. The prediction model is well fitted to the incidence rate (R2 = 0.9443 and 0.9388, p < 2.2 × 10-16). To analyze regional deviations, we classify outpatient data, air pollutant, and meteorological factors in 16 administrative districts (seven metropolitan areas and nine states). Our results confirm NO2 and relative humidity are the factors impacting regional deviations in the prediction model.

A new air-washing method to clean fabric filters clogged with submicron fume particles: A pilot-scale study.

This study investigates a new air-washing cleaning system that directly injects compressed air on the filter surface for filter regeneration in a fabric filter (FF) dust collector. A pilot-scale FF is designed to test the new system and to compare it with the conventional pulse-jet cleaning system with regard to filter clogging by fume particles. A pleated filter with a filtration area of 2.4 m2 is installed in the FF and a thermal steel spraying gun is used to supply the fume particles. Pressure drop and particle emission concentration are monitored to examine the effect of the new system on filter regeneration and collection efficiency. The results show that the air-washing cleaning is effective for filter regeneration, as it allows the FF to operate stably for a long time, whereas the pulse-jet cleaning fails to achieve filter regeneration, resulting in a continuously increasing pressure drop. In addition, air-washing cleaning shows better performance on collection efficiency than the pulse-jet cleaning method, as it reduces the outlet particulate matter concentration to less than half that of the pulse-jet cleaning.

Characteristics of nanoparticle formation and hazardous air pollutants emitted by 3D printer operations: from emission to inhalation.

This study examined the emissions of nanoparticles and hazardous air pollutants (HAPs) by 3D printer operations and evaluated nanoparticle deposition behavior using a prediction model. Nanoparticles and HAPs were sampled at the Inha University 3D printing center with five fused filament fabrication (FFF)-type 3D printers. The number size distribution of the nanoparticles exhibited a bimodal distribution with dominant peaks over a large size range between 70 and 100 nm and a smaller size range between 10 and 20 nm. With increasing 3D printer operation, the number concentration of 10 nm particles increased, and the final number concentration was 3.6 times higher than that of the background concentration. Nanoparticle formation and agglomeration were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Model calculations revealed that a large number of nanoparticles between 10 and 30 nm in size are deposited in the lower human respiratory tract (generation number: 16-22). A total of 14 HAPs species were detected, among which hexane, acrylonitrile, and benzene concentrations were the highest.

Development of a Conjunctivitis Outpatient Rate Prediction Model Incorporating Ambient Ozone and Meteorological Factors in South Korea.

Ozone (O3) is a commonly known air pollutant that causes adverse health effects. This study developed a multi-level prediction model for conjunctivitis in outpatients due to exposure to O3 by using 3 years of ambient O3 data, meteorological data, and hospital data in Seoul, South Korea. We confirmed that the rate of conjunctivitis in outpatients (conjunctivitis outpatient rate) was highly correlated with O3 (R 2 = 0.49), temperature (R 2 = 0.72), and relative humidity (R 2 = 0.29). A multi-level regression model for the conjunctivitis outpatient rate was well-developed, on the basis of sex and age, by adding statistical factors. This model will contribute to the prediction of conjunctivitis outpatient rate for each sex and age, using O3 and meteorological data.

Surface and Airborne Measurements of Organosulfur and Methanesulfonate Over the Western United States and Coastal Areas.

This study reports on ambient measurements of organosulfur (OS) and methanesulfonate (MSA) over the western United States and coastal areas. Particulate OS levels are highest in summertime, and generally increase as a function of sulfate (a precursor) and sodium (a marine tracer) with peak levels at coastal sites. The ratio of OS to total sulfur (TS) is also highest at coastal sites, with increasing values as a function of Normalized Difference Vegetation Index (NDVI) and the ratio of organic carbon to elemental carbon. Correlative analysis points to significant relationships between OS and biogenic emissions from marine and continental sources, factors that coincide with secondary production, and vanadium due to a suspected catalytic role. A major OS species, methanesulfonate (MSA), was examined with intensive field measurements and the resulting data support the case for vanadium's catalytic influence. Mass size distributions reveal a dominant MSA peak between aerodynamic diameters of 0.32-0.56 µm at a desert and coastal site with nearly all MSA mass (≥ 84%) in sub-micrometer sizes; MSA:non-sea salt sulfate ratios vary widely as a function of particle size and proximity to the ocean. Airborne data indicate that relative to the marine boundary layer, particulate MSA levels are enhanced in urban and agricultural areas, and also the free troposphere when impacted by biomass burning. Some combination of fires and marine-derived emissions leads to higher MSA levels than either source alone. Finally, MSA differences in cloud water and out-of-cloud aerosol are discussed.