This study designed an improved parallel-plate particle separator, the Keio Measurement System of Aerosol Charging State (K-MACS), using numerical simulations to achieve a stable laminar flow field in practical devices. Combined with optical particle counters (OPCs), the system enables high-temporal-resolution (20 s) measurements of number concentrations of positively charged, uncharged, and negatively charged particles, allowing estimation of charge distributions for submicron particles (0.3–0.5 µm). The average particle charge number (pave) and standard deviation (1σ) were obtained by fitting the distributions to a Gaussian function. Experimental evaluation demonstrated that multiply charged particles moved toward oppositely charged electrodes and identified an optimum voltage of approximately 5.4 kV, where experimental and theoretical charge distributions agreed well. Measurement uncertainties for 1σ and distribution amplitude were reduced to 5
This study characterizes the chemical and optical properties of carbonaceous aerosols in urban Chiang Mai, Thailand, during an intensive monitoring period in March 2024. The campaign coincided with a strong El Niño event, resulting in extreme high temperatures and severe drought conditions. The mean PM2.5 concentration was 64.3 µg/m³, exceeding the WHO 24-hour guideline (15 µg/m³) by approximately 4.3 times. High OC/EC ratios (mean 6.0) and a strong correlation with CO (R = 0.71, 924.5 ppb) indicated a strong influence of biomass burning on particulate air quality, while urban baseline emissions also contributed. Furthermore, severe nighttime atmospheric stagnation trapped pollutants, exacerbating high-concentration episodes. Source apportionment via an Aethalometer model revealed that biomass burning-derived black carbon (BCbb) drove the overall variability during these episodes. Notably, brown carbon (BrC) significantly enhanced shortwave light absorption at 370 nm, accounting for a campaign mean contribution of 35.1
PM10 (particles with aerodynamic diameter ≤ 10 μm) is a carrier of toxic elements from diverse sources. This study examined the origin and potential health risks associated with trace elements in PM10 during the dry season in Ghana. A Gent sampler, equipped with a Gast pump and a stacked filter unit, was employed to collect airborne particulates at the Winneba Highway Intersection (WHI) and the Apam Fish-smoking Community (AFC). Sampling was conducted three times per week from November 2022 to March 2023, with each session lasting 24 h. The particulate samples were analysed for elemental and Black Carbon (BC) concentrations using Ag-anode X-ray tube spectrometer and a smoke stain reflectometer, respectively. The US EPA Air Quality Index (AQI) and health risk assessment models evaluated air quality and elemental toxicity risks, respectively. Notably, the average levels of Chromium (77 ng/m3) and Nickel (210 ng/m3) at WHI, and Chromium (310 ng/m3) and Nickel (470 ng/m3) at AFC, exceeded the US EPA threshold limits. Pearson’s correlation model linked BC, sulphur, and potassium to combustion-related emission sources. Principal Component Analysis (PCA) showed that PM10 at WHI originated from fugitive dust and sea salt, vehicular emissions, and minor industrial activities, whereas sea salt, dust, biomass burning, and vehicular emissions contributed to PM10 at AFC. AQI ratings indicated moderate air quality during December to February, implying potential health risks for sensitive populations. Cancer risk levels were relatively higher in adults than in children. Adopting clean fuels and sustainable transport is vital to reducing PM₁₀ health risks.
Polycyclic aromatic hydrocarbons (PAHs) exposure in children has been associated with various health impacts, including increased risk of asthma, skin diseases and allergies. In this study, we investigated the distribution, possible sources, and potential health risks of PAHs bound to fine particulate matter (PM2.5) collected in urban primary school environments. PM2.5 samples were collected using two identical low-volume samplers (LVS) equipped with quartz fibre filters (QMA) in both indoor and outdoor environments. The samples underwent ultrasonic extraction with a mixture of dichloromethane/n-Hexane (1:1) before analysis using gas chromatography-mass spectrometry (GC-MS). The results showed the mean total concentration of PAHs (∑PAHs) for indoor and outdoor environments were 4.34 ± 2.39 ng m− 3 and 5.62 ± 2.39 ng m− 3, respectively. High molecular weight (HMW) PAHs with five- and six-rings accounted for over 60
Ozone (O3) pollution has emerged as a critical environmental issue in the Pearl River Delta (PRD), particularly during spring and autumn. This study employs the Weather Research and Forecasting (WRF) model coupled with the Community Multiscale Air Quality (CMAQ) modeling system, a widely used tool for simulating atmospheric processes and chemistry, to investigate the drivers of O3 pollution in May 2022, focusing on the impacts of meteorological variations and changes of other factors, including emission and ozone formation sensitivity variations. Results indicate that the 90th percentile of maximum daily average of 8-hour O3 concentrations across the PRD cities increased by an average of 44.2
Tropospheric ozone (O3) formation in rural environments is controlled by interactions among nitrogen oxides (NOx), volatile organic compounds (VOCs), radical chemistry, and meteorology. This study investigated photochemical O3 formation and oxidant variability at a rural agricultural site in Buan, South Korea, using three years (2023–2025) of continuous observations. Because direct VOC and radical measurements were unavailable, an observation-based proxy framework constrained by the oxidant indicator Ox (O3 + NO2) was applied using routinely measured NO, NO2, O3, temperature, and relative humidity. Ox was used to represent oxidant levels while reducing the influence of rapid NO titration. During the study period, annual mean NO2 declined, whereas O3 and Ox remained within relatively narrow ranges. O3 and Ox showed clear seasonal cycles, with elevated levels from spring to early summer. Proxy-derived OH, VOC oxidation, HO2, RO2, and p(O3) also exhibited pronounced warm-season maxima, indicating enhanced daytime photochemical activity under favorable conditions. Annual statistics of integrated daytime proxy p(O3) and observed daytime oxidant enhancement (ΔOx) showed only modest interannual variability, with a slight decrease from 2023 to 2025. Regime filtering further identified a high-photochemistry regime under warm, relatively dry, and low-NO conditions, in which both integrated proxy p(O3) and observed daytime ΔOx were substantially higher than under a contrasting low-photochemistry regime. These results indicate that local daytime oxidant enhancement at the Buan site was most clearly expressed under conditions favorable for radical production and photochemical processing. Although the proxy-derived variables do not represent absolute radical concentrations or ozone production rates, the framework provides a practical tool for diagnosing relative photochemical behavior in rural environments where direct VOC and radical measurements are unavailable.
The Republic of Korea estimates annual air pollutant emissions through the Clean Air Policy Support System (CAPSS), based on 260 types of basic data collected from approximately 150 institutions. These estimation results are published annually as national statistics and are used to formulate and evaluate national air quality policies. This study analyzed the emission characteristics by source type and administrative region using the 2022 Republic of Korea National Air Pollutant Emissions Inventory (NEI). The results were further categorized according to improvements compared with 2021—specifically in estimation methods, emission factors, policies, and socioeconomic conditions. In 2022, national emissions of major air pollutants were as follows: PM₂.₅, 59,459 tons; SOₓ, 126,743 tons; NOₓ, 857,026 tons; VOCs, 938,341 tons; NH₃, 242,227 tons; and CO, 921,783 tons. The primary emission sources for each pollutant were: fugitive dust for PM₂.₅ (26.1
Over the past decade, with the implementation of a series of prevention and control measures, the concentration of PM2.5 at the surface in China has rapidly decreased. However, the issue of environmental ozone in the Guangdong-Hong Kong-Macao Greater Bay Area, which is located in South China, has begun to stand out, becoming a key factor affecting air quality. Currently, research on ground ozone pollution primarily focuses on super city clusters with high pollutant emissions, while there is comparatively limited research on the cities with lower emissions on the outskirts of the Pearl River Delta. This study utilized continuous automatic monitoring data for air quality and meteorological conditions from 2019 to 2023 to summarize ground-level ozone pollution events in Heyuan, South China, with a focus on the characteristics of ozone pollution and associated weather types. Over the five-year study period, a total of 39 ozone pollution days were observed in Heyuan, which mainly occurred in spring and autumn. Specifically, the annual number of ozone pollution days was 7 in 2019, 6 in 2020, 11in 2021, 10 in 2022 and 5 in 2023, with an annual average of 7.8 days. Additionally, low-level pollution, characterized by AQI values between 101 and 110, comprised a significant proportion (53.8
Wintertime particulate matter (PM) episodes in Seoul are marked by elevated nitrate, yet nighttime formation remains poorly understood. We reexamined high-PM periods during the Fine Particle Research Initiative in East Asia considering National Differences (FRIEND) campaign (December 2020–January 2021) using a box model Korea Air Quality Observation-Based Box model (KAB) enhanced with a double-layer structure and expanded sensitivity tests. Contrary to previous work, residual-layer chemistry alone did not explain nighttime nitrate underestimation. Instead, model results indicate that recirculation of secondary pollutants—exported under westerlies and reintroduced under northeasterlies—was the primary driver of elevated nighttime nitrate. Prescribing a background nitrate concentration during PM episodes greatly improved model–observation agreement, highlighting the importance of regional transport. Empirical Kinetic Modeling Approach (EKMA) simulations with the tuned model show that ozone, nitrate, and secondary organic aerosol (SOA) formation during PM episodes occurred in a volatile organic compound (VOC)-limited and nitrogen oxides ( NO_x )-saturated regime. Under these high- NO_x conditions, precursor reductions produced only modest decreases in secondary pollutants although it is possible that the sensitivity was substantially underestimated because the KAB model represents recirculation using a constant boundary condition. Sensitivity analyses further show that aromatic VOCs—especially xylene species—play a disproportionately large role in secondary pollutant formation relative to their mass contribution. These results underscore the influence of regional recirculation and aromatic hydrocarbon chemistry on wintertime secondary pollution, and emphasize the need for improved treatment of regional transport, SOA formation, and VOC speciation to support effective winter air-quality management in the Seoul metropolitan area.
Abstract In this study, a Differential Absorption Lidar (DIAL) system was employed to remotely quantify the concentration distribution and flux of benzene released from a flare stack. The measurements were conducted on May 2, 2024, at Plant B located within the A petrochemical industrial complex in Korea, and a total of six repeated measurements were performed for a single flare stack. The on-resonant wavelength $$\:\left({\lambda\:}_{on}\right)$$ was determined as 252.1998 nm through a cell scan procedure. A cross-wind measurement geometry was applied to obtain transverse concentration distributions at a distance of approximately 400–430 m from the DIAL. The scan was conducted over 11 lines (line 1–11) ranging from 14.9° to 15.9°. Each line was measured for 50 s at a repetition rate of 10 Hz, yielding 500 shots per line and a total scan duration of 550 s per measurement. The maximum observed benzene concentrations were 2.62, 3.17, 3.11, 2.65, 3.13, and 2.23 ppm for each case. By combining the concentration data with flare stack height wind speeds estimated using a logarithmic wind profile, the corresponding benzene flux was calculated as 7.13, 6.18, 7.61, 8.11, 10.33, and 10.17 kg·hr⁻¹, respectively. The results indicate that wind speed variations significantly influence flux estimation. This study represents the first reported application of a remote DIAL system to quantitatively determine benzene flux from an industrial flare stack in Korea.
Mercury being a neurotoxin poses great threat to the human health as well as environment. It is emitted into the atmosphere through both natural and anthropogenic sources and can travel long distances over time before being scavenged and deposited in the deep ocean beds or mineral soils thus becoming a global concern. It occurs in atmosphere largely in three different forms, viz., gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) or reactive gaseous mercury (RGM) and particulate bound mercury (PBM). Over > 95
Tropospheric ozone (O3) is widely recognized as a threat to global food security due to its detrimental effects on crop productivity. Previous studies have determined exposure-response functions, e.g., yield response to O3 metrics, through controlled O3 exposure experiments. However, this approach requires substantial cost and time. Therefore, we aimed to derive exposure-response functions epidemiologically and assess the impact of O3 on the productivity of rice and Japanese mustard spinach in Japan. Accumulated O3 exposure over a threshold of 40 ppb (AOT40, ppm h) during the growth period was calculated at O3 monitoring stations and spatially interpolated using the ordinary kriging method, then averaged for each prefecture. We derived the exposure-response relationships between prefecture-scale AOT40 and crop yields using the boundary line technique. Our results clearly demonstrated that yields of both species are reduced with increasing AOT40 levels, showing a decline of 2.01
Natural atmospheric particles, such as yellow sand, pollen, and volcanic ash, are frequently deposited on exposed surfaces, potentially reducing the optical performance of solar panels and other transparent systems. However, the removability of these particle types under environmental conditions has not been compared systematically. In this work, we conducted laboratory experiments to evaluate the removability of yellow sand, pollen, and volcanic ash deposited on slide glass surfaces as representative natural particulates. Controlled wind and simulated rainfall were applied separately and in combination to investigate particle adhesion and cleaning behavior. Although pollen was efficiently removed by wind, it had the greatest effect on light transmittance per unit weight. In contrast, yellow sand exhibited strong adhesion and low removability.
Volatile organic compounds (VOCs) are key precursors of ozone and secondary organic aerosols (SOA), yet emissions from agricultural and livestock activities remain largely unrecognized in emission inventories. This study conducted field measurements of 34 VOC species near livestock facilities and adjacent croplands in Chuncheon, South Korea, during April, December, and February to characterize their composition, temporal variation, and secondary organic aerosol formation potential (SOAFP). Sum of the measured VOCs concentrations were highest in February, with alkanes comprising about 60
This study evaluated multi-pollutant exposure and health risks of benzene, toluene, ethylbenzene and xylene (BTEX) and PM2.5-bound heavy metals in the Ulsan Mipo National Industrial Complex, one of Korea’s largest petrochemical zones. Real-time BTEX concentrations were measured using a Me-DOAS system, while PM2.5 chemical components were simultaneously analyzed to assess both acute and chronic exposures. Ethylbenzene (31.28 ± 29.39 µg/m3) and m-xylene (35.39 ± 37.21 µg/m3) were dominant among BTEX, showing concentrations 5–10 times higher than those reported in other industrial regions. Diurnal and seasonal variations were significant, with BTEX peaking in winter and nighttime, whereas PM2.5 and metallic constituents (Mn, Co, Cd, V) peaked in spring. Probabilistic exposure assessment revealed that HQ values for all pollutants were generally below 1.0, indicating negligible non-cancer risks. However, short-term evening and nighttime peaks led to higher HQ for benzene and p-xylene, occasionally approaching the threshold. Time-resolved cancer risk analysis showed nighttime benzene exposure dominated total carcinogenic risk (median ECR: 3.4E-07–5.5E-07; exceedance ≤ 8.3
Ethylene oxide (EtO) is a volatile organic compound that poses both acute and chronic risks to human health, prompting governments worldwide to implement measures aimed at reducing ambient EtO concentrations. In this study, regional chemical transport model calculations were performed using the EtO emission inventory provided by the Ministry of Economy, Trade and Industry and the Ministry of the Environment, Japan. The target area and period were the Greater Tokyo Area (GTA) in 2017. The results indicated that the modeled atmospheric EtO concentrations were lower than the observed concentration at all monitoring sites in the GTA, with the discrepancy reaching up to one order of magnitude. Long-range transport of EtO from the Asian continent to Japan was not identified as the primary cause of this discrepancy. Instead, the significant discrepancy might be attributed to global background concentrations of EtO, resulting from its long tropospheric lifetime. To improve the accuracy of atmospheric EtO assessments using chemical transport models, it is essential to account for global emissions.
Volcanic and geothermal activities are one of the major emission sources of mercury (Hg), emitting 500 tons y− 1 into the atmosphere, and it is known that there are three main forms of Hg released to the atmosphere from these activities: gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (PBM). In this study, the concentrations of GEM, GOM and PBM2.5 (PBM in particles less than 2.5 μm) were continuously observed for 2 years at Sensuikyo Station, located 2.5 km northeast from Nakadake No. 1 Crater of Mt. Aso. The observed mean concentrations of GEM, GOM, and PBM2.5 in the entire period were 1.64, 0.021 and 0.021 ng m− 3, while maximum concentrations were 9.04, 2.45 and 3.20 ng m− 3, respectively. The concentrations increased significantly when the volcanic activity was high and when the wind blew from the crater. Under high volcanic activity, the mean concentrations of GEM, GOM and PBM2.5 were 1.3, 4.1, and 15.3 times higher than those during calm conditions. Changes in GOM and PBM2.5 concentrations between active and calm conditions were significantly higher than those of GEM. The amplitude of volcanic tremors is usually used as a reference indicator of the volcanic activity. GOM and PBM2.5 concentrations became higher before the volcanic tremor amplitude increased. However, the reliability of atmospheric GOM measurements in volcanic regions with high levels of acidic gases is still debatable. Therefore, PBM2.5 concentrations can be used as one of the indicators to assess the activity of Mount Aso volcano.
This study examines variations in PM2.5 mass, chemical composition, and oxidative potential (OP) at Gwanghwamun Square, Seoul, using intensive 3-h integrated sampling campaigns performed in September 2020 and 2022. The mean PM2.5 concentrations declined significantly from 20.66 µg/m3 in 2020 to 12.04 µg/m3 in 2022, indicating a 42
In this study, to assess the long-term air quality status in South Korea, we analyzed the concentration and attainment rate of air quality standards for 8 pollutants such as SO₂, NO₂, CO, O₃, PM₁₀, PM₂.₅, Pb, and benzene. In 2023, the average concentrations were as follows: PM₁₀ 37 µg/m³, PM₂.₅ 19 µg/m³, SO₂ 0.0025 ppm, NO₂ 0.0135 ppm, CO 0.39 ppm, O₃ 0.0327 ppm, Pb 0.01979 µg/m³, and benzene 0.64 µg/m³. Due to ongoing strict emission control policies, PM₂.₅ and NO₂ levels have decreased by approximately 27
Air pollution is the most significant environmental health risk, and the chemical composition of PM2.5 has the greatest impact on its effects on human health. While PM2.5 pollution has been widely studied, little attention has been given to the role of landfill fires in shaping PM2.5 composition and dispersion in medium-sized cities with complex topographies. This study integrates the physical and chemical characterization of PM2.5 (potassium, chlorine, and irregular morphology) with AERMOD dispersion modeling to assess exposure during a landfill fire in Guanajuato, Mexico. The maximum monthly average concentration was recorded in May at 22.4 µg m⁻3, while the 24-h average exceeded the allowable limit of 33 µg m⁻3 during the days of the landfill fire, reaching 50 µg m⁻3. The annual average concentration (13.4 µg m⁻3) also exceeded the 10 µg m⁻3 guideline. AERMOD simulations reproduced observed patterns, confirming northeastward dispersion toward the city hillside. Based on the 12-h moving average during the fire (45 µg m⁻3), residents were exposed to poor air quality and elevated risks of respiratory and cardiovascular diseases, stroke, and lung cancer. These results provide novel evidence of the contribution of landfill fires to urban PM2.5 pollution and associated health risks, offering valuable insights for air quality management and public health protection in cities with similar environmental conditions.
