Search Results (47)

Agricultural crop residue burning is a major driver of seasonal PM2.5 pollution and greenhouse gas (GHG) emissions in Northern Thailand. This study quantified GHG emissions from the open burning of rice, maize, and sugarcane residues across six provinces (Chiang Mai, Mae Hong Son, Lampang, Uttaradit, Nakhon Sawan, and Kamphaeng Phet) from 2019 to 2024 using the 2006 IPCC emission methodology. Spatiotemporal patterns of fire hotspots were characterized using MODIS and VIIRS satellite data, combined with kernel density estimation (KDE) and land-use classification in ArcGIS Pro. Total non-CO₂ GHG emissions (CH₄ and N₂O, expressed as CO₂-eq using GWP100 from IPCC AR5) over the six years totaled 2,599,551 tCO₂-eq, with major rice contributing the largest share (35%), followed by sugarcane (24%), second rice (21%), and maize (20%). Nakhon Sawan was the leading emitter (41%), reflecting its extensive rice and sugarcane cultivation. Pearson correlation analysis revealed consistently positive relationships between daily fire hotspot counts and PM2.5 concentrations (r = 0.30–0.84), with the strongest correlations observed in Mae Hong Son, where basin topography traps pollutants. Time-series analysis confirmed pronounced seasonal PM2.5 peaks that exceeded Thailand’s 24-h NAAQS limit (37.5 μg/m³) by 7–9 times in severe years. Biochar production via pyrolysis was evaluated as a zero-burning alternative, with an estimated annual carbon sequestration potential of 2.3–3.5 million tCO₂-eq, substantially exceeding emissions from open burning. These findings indicate that crop-residue valorization options—including biochar production, composting, and biochar co-compost—could theoretically offset agricultural GHG emissions and reduce field-burning PM2.5 emissions in Northern Thailand. However, the realized mitigation will depend on (i) verification of biochar long-term stability in tropical Thai soils through dedicated in situ trials, (ii) economic incentives that offset biochar production costs of approximately 1500–3500 THB per tonne, and (iii) integration within a policy mix that combines burning bans, mechanization support, and farmer extension services. Without these enabling conditions, biochar should be regarded as a future-perspective option rather than an immediately deployable solution. Full article

Most air pollution research in India has predominantly focused on the Indo-Gangetic Plain (IGP) owing to its high pollution levels and dense populations, leaving peninsular India comparatively undercharacterized. In contrast, South India remains underexplored because of its relatively limited long-term monitoring and more favorable meteorology. This geographical imbalance restricts a comprehensive national understanding of particulate matter (PM) dynamics. Addressing this gap, the present study delivers a multi-scale (hourly to interannual) spatiotemporal assessments of PM_2.5 across eight monitoring stations in Andhra Pradesh, a South Indian State, for the period 2020–2024. The analysis reveals pronounced seasonal variability, with persistent winter and post-monsoon maxima. Although overall concentrations are low compared to northern India, urban–industrial centers such as Visakhapatnam and Rajahmahendravaram frequently exceeded both the National Ambient Air Quality Standards (NAAQS) and World Health Organization (WHO) guidelines. Notably, Amaravati, a non-industrial and low-lying inland site, exhibited anomalously moderate PM_2.5 levels, with ~11.58% of hourly values surpassing 60 µg m⁻³. The COVID-19 lockdown period further offered a natural experiment, revealing substantial reductions (30–65%) in PM_2.5 and PM₁₀ at major urban sites while concurrent ozone enhancements (up to ~50%) at Tirupati and Rajahmundry exposed complex photochemical sensitivity under reduced NO_x conditions. Satellite-based MERRA-2 estimates corroborated inter-annual variability and the short-lived improvement in air quality. This study demonstrates that air quality dynamics in the state of Andhra Pradesh are governed by region-specific meteorological controls, episodic processes, and localized emission characteristics, necessitating expanded long-term monitoring infrastructure and improved satellite–ground calibration frameworks. Full article

Air quality in the San Joaquin Valley (SJV) often fails to meet Environmental Protection (EPA) Standards for particulate matter (PM) ≤ 2.5 microns. The San Joaquin Valley Center for Air Injustice Reduction (SJV-CAIR) at the University of California, Merced, partnered with local community-based organizations to expand networks of low-cost air quality monitors (PurpleAir, PA-II) in Fresno County to increase community air monitoring to better characterize air pollution trends and spatial variability. In this study, we compared community and regulatory air pollution monitoring using PM_2.5 data from the SJV-CAIR network in Fresno County during June–July 2023. Measurements from community monitors identified locations across the county that may episodically exceed National Ambient Air Quality Standards (NAAQS) compared with regulatory monitors, while providing similar concentration estimates. Our study also compared characterization of spatial variability in PM exposure using interpolation maps with only regulatory monitors and the enhanced community monitoring network. These analyses identified four weeks with increased PM_2.5 concentrations in some locations that were not identified by regulatory monitors. These findings indicate that low-cost community sensors can be an effective tool for supplementing regulatory monitoring to provide localized PM_2.5 exposure information to residents and, importantly, identify high-risk areas that warrant ongoing assessment using approved regulatory monitors. Full article

Air density and pressure above the Earth’s surface in the tropospheric region depend on altitude relative to sea level. When a given amount of pollutant gas enters the atmosphere at sea level, it produces a contaminated air mixture; if the same amount of pollutant gas enters the atmosphere at a location situated at higher altitude, atmospheric pollution certainly also occurs. However, the relative compositions are not the same in both cases due to the greater air density present at sea level compared to the air density at higher altitude. Current regulatory frameworks, including the National Ambient Air Quality Standards (NAAQS) of the United States Environmental Protection Agency and the Air Quality Guidelines (AQG) of the World Health Organization, establish constant numerical values for air quality standards uniformly applicable at all geographic locations, regardless of altitude, resulting in inadequate health protection for millions of people. To address this critical gap, a universal adjustment factor for atmospheric pollutant gas concentrations at different altitudes has been derived from first principles of atmospheric physics; this factor is $f=e^{-0.000115 h}$, where h is expressed in meters, assuming air at constant temperature given that small temperature variations do not substantially influence atmospheric density and pressure or pollutant concentrations at different altitudes. The factor was systematically applied to the NAAQS and WHO AQG, demonstrating that for altitudes of 3500 m, representative of cities such as Cusco, Peru, the adjusted standards are approximately 67% of the nominal values established at sea level, preserving the gaseous pollutant–air proportionality. Experimental measurements of atmospheric density in six Peruvian cities distributed along an altitudinal gradient of 0–3826 m validated the theoretical model with relative deviations less than 5%, confirming the physical consistency of the derived factor. The importance of this research lies in adequately regulating air quality standards related to public health and the environment, supporting the implementation of equitable environmental policies aligned with the United Nations (UN) 2030 Sustainable Development Goals, and establishing that the constant values defined at sea level must be adjusted according to the aforementioned factor when geographic altitude is considered. Full article

The paper presents a number of tests of the carbon monoxide concentration in a single-car garage equipped with exhaust ventilation, while the combustion engine of a parked passenger car is operating. The main source of carbon monoxide in the garage is the internal combustion engine of a passenger car. Single-car garages are characterized by a relatively small volume, which causes a rapid accumulation of carbon monoxide inside the garage. The aim of this publication is to present the results of research on carbon monoxide concentration in a single-family building garage with the combustion engine in a passenger car running and at various air exchanges in the garage. The test results showed that the permissible values (WHO, NAAQS) of carbon monoxide concentrations were significantly exceeded, both with the exhaust ventilation switched on and off. The highest carbon monoxide concentration values (2253 ppm) in the garage were observed when the exhaust ventilation was turned off. The study also developed two one-dimensional models of carbon monoxide concentrations in a garage with the combustion engine of a passenger car turned on, with the exhaust ventilation turned on and off. The models developed can be used in ventilation design to estimate the carbon monoxide concentrations in garages, based on the type of car and the number of air changes. Full article

Data on particulate matter, gaseous pollutants, and AQI values from three cities (Haikou, Sanya, and Danzhou) between January 2018 and December 2022 were obtained in order to analyze the spatiotemporal distribution characteristics of air pollution, the correlation between pollutants with meteorological conditions, and the potential sources in Hainan Island. The spatiotemporal distribution’s characteristics demonstrated that the annual mean concentrations of SO₂, NO₂, CO, O₃, PM₁₀ and PM_2.5 were 4.34 ± 1.11 μg m⁻³, 9.87 ± 1.87 μg m⁻³, 0.51 ± 0.06 mg m⁻³, 73.04 ± 6.36 μg m⁻³, 27.31 ± 3.63 μg m⁻³, and 14.01 ± 2.02 μg m⁻³, respectively. The yearly mean concentrations were trending downward in the past few years and were below the National Ambient Air Quality Standard (NAAQS) Grade II. Summer was the season with the lowest concentrations of all pollutants (3.84 μg m⁻³, 7.34 μg m⁻³, 0.42 mg m⁻³, 52.80 μg m⁻³, 18.67 μg m⁻³ and 8.67 μg m⁻³ for SO₂, NO₂, CO, O₃, PM₁₀ and PM_2.5, respectively), and afternoons were the time with the lowest concentrations of pollutants (except for 78.04 μg m⁻³ for O₃). The influence of meteorological conditions on pollutants was examined: there was a prominent positive correlation between temperature and O₃ in summer, and relative humidity largely influenced the concentrations of PM. The pollution in Hainan was affected more by regional transport; according to the backward trajectory results, Hainan is susceptible to air masses from Guangdong and Fujian to the northeast, the Indochina Peninsula to the southwest, and the South China Sea to the southeast. The results of PSCF and CWT analyses indicated that Guangdong, Jiangxi, Hunan, and Fujian were the primary potential sources of PM_2.5 and O₃. Full article

The comparison between Federal Equivalent Method (FEM) and Federal Reference Method (FRM) monitors in measuring fine particulate matter (PM_2.5) concentrations frequently raises concerns about the accuracy and reliability of data. The comparability, or lack thereof, of data between FRM and FEM monitors may have significant implications for maintaining compliance with the National Ambient Air Quality Standards (NAAQSs). This study investigates the performance of continuous FEM monitors collocated with FRM monitors across 10 EPA regions in the U.S., focusing on PM_2.5 measurements collected from 276 monitoring stations. Through an analysis of annually averaged paired concentration data, the study examines concentration ratios (FEM/FRM) and associated biases (in %, defined as [(FEM/FRM)−1] × 100) in FEM monitors across different manufacturers, measurement methods, EPA regions, and sampling location types. The study findings reveal a varied distribution of FEM/FRM ratios, with more than 50% of the FEM monitors having FEM/FRM > 1.1 and approximately 30% having FEM/FRM > 1.2. Substantial variations in estimated biases are identified among monitor types, measurement methods, EPA regions, and sampling site locations. Light scatter-based FEM monitors, notably Teledyne models 640 and 640x, dominate all locations (urban, suburban, and rural), with rural areas exhibiting higher mean bias values for both light scatter and beta attenuation FEM monitors (41% and 23%, respectively). On average, light scatter-based FEM monitors demonstrate higher biases compared to beta attenuation monitors across all EPA regions (28% vs. 12%). Irrespective of the measurement method employed, FEM monitors demonstrate a significant positive bias (mean bias 22%) relative to FRM monitors, which could result in an overestimation of PM_2.5 design values (DVs) by 13–21% at monitoring sites designating FEMs as primary monitors for NAAQSs compliance designations. These findings emphasize the critical need to address method comparability issues, especially considering the recent tightening of NAAQSs for PM_2.5 (annual) from 12 µg/m³ to 9 µg/m³ in the U.S. Full article

Despite extensive research on particulate matter (PM) pollution in India’s Indo-Gangetic Plain (IGP), source apportionment remains challenging. This study investigates the effect of particulate matter (PM₁₀)-associated water soluble inorganic ions (WSIIs) on ambient air concentration across the middle IGP from January to December 2018. Moreover, the seasonal fluctuation and chemical characterization of PM₁₀ were assessed for the year 2018. The results revealed a high concentration of PM₁₀ (156 µg/m³), exceeding the WHO and National Ambient Air Quality Standard (NAAQS) limits. The highest PM₁₀ levels were observed during autumn, winter, summer, and the rainy season. The study identified SO₄²⁻ and NH₄⁺ as the most common WSIIs, constituting 46% and 23% of the total WSIIs. Source apportionment analysis indicated that street dust, biomass burning, and vehicle and industrial emissions together with secondary formation significantly contributed to IGP’s PM pollution. Additionally, the investigation of air mass back trajectory suggests that air quality in IGP is largely influenced by eastern and western Maritime air masses originated from the Arabian Sea, the Bay of Bengal, Gujarat, Afghanistan, Pakistan, and Bangladesh. Full article

To evaluate carbonaceous components in the ambient air in the eastern region of Indonesia, 35 Total Suspended Particulate Matter (TSP) samples were collected on four characteristic roadsides on Sultan Alauddin Street, in Makassar City, using a high-volume air sampler. The average TSP concentration was 279.7 μg/m³, which exceeded both the National Ambient Air Quality Standard (NAAQS) of Indonesia and the World Health Organization (WHO) standards. The highest concentration reached 838.6 μg/m³ in the GR (gravel) site, which had the highest number of vehicles and was near a U-turn. TSP concentration was higher during peak hours (morning and late afternoon) than off-peak hours (noon). The main component of the total carbon (TC) fraction was organic carbon (OC), which showed a strong correlation with elemental carbon (EC) (r values for the morning, noon, and late afternoon were 0.89, 0.87, and 0.97, respectively), indicating that the carbon components were derived from common sources. TSP had a strong correlation with carbon components, except for char-EC. OC vs. soot-EC and EC vs. soot-EC also correlated well, suggesting the dominant influence of vehicle exhaust emissions. Non-exhaust emissions had a slight influence during peak hours, particularly at the GR site. Full article

Individuals who spend most of their time indoors are especially sensitive to indoor air quality (IAQ), which significantly impacts their general well-being and health. Traditional IAQ measurement techniques, however, are frequently pricy, complicated, and labor-intensive. In this study, we used a low-cost, simple-to-use, and handy sensor system to track the levels of carbon dioxide (CO₂), nitrogen dioxide (NO₂), ozone (O₃), particulate matter (PM_1.0, PM_2.5, and PM₁₀), temperature, and relative humidity (RH) in a laboratory at the Bamidele Olomilua University of Education, Science, and Technology in Ikere-Ekiti for a month. We contrasted the outcomes with other benchmarks and WHO recommendations. However, the NO₂ levels (144.00–303.00 ppb) exceeded the suggested levels (National Institute for Occupational Safety and Health (NIOSH)—70 ppb; National Ambient Air Quality Standards (NAAQS)—100 ppb; National Environmental Standards and Regulations Enforcement Agency (NESREA)—120 ppb; and World Health Organization (WHO)—25 ppb), suggesting a possible cause of indoor contaminants. We also noticed that the temperature and humidity varied considerably throughout the day, which impacted the inhabitants’ thermal comfort and ventilation. The principal component analysis (PCA) findings indicate that particulate matter, the weather, photochemical reactions, and combustion processes are the key contributors to fluctuation in the air quality measurements. Based on their quantities and relationships, these elements can have a variety of effects on both the natural environment as well as well-being. Our monitoring device can give immediate information and warnings, assisting in locating and reducing indoor airborne pollutant sources and enhancing indoor air quality (IAQ). This work shows that adopting a low-cost sensor system for IAQ measurement in underdeveloped nations, where such data are sparse and frequently erroneous, is both feasible and beneficial. Full article

The Wasatch Front in Utah, USA is currently a non-attainment area for ozone according to the Environmental Protection Agency’s (EPA) National Ambient Air Quality Standards (NAAQS). Nitrogen oxides (NO_x = NO₂ + NO) and volatile organic compounds (VOCs) in the presence of sunlight lead to ozone formation in the troposphere. When the rate of oxidant production, defined as the sum of O₃ and NO₂, is faster than the rate of NO_x production, a region is said to be NO_x-limited and ozone formation will be limited by the concentration of NOx species in the region. The inverse of this situation makes the region VOC-limited. Knowing if a region is NO_x-limited or VOC-limited can aid in generating effective mitigation strategies. Understanding the background or regional contributions to ozone in a region, whether it be from the transport of precursors or of ozone, provides information about the lower limit for ozone concentrations that a region can obtain with regulation of local precursors. In this paper, measured oxidant and NO_x concentrations are analyzed from 14 counties in the state of Utah to calculate the regional and local contributions to ozone for each region. This analysis is used to determine the nature of the atmosphere in each county by determining if the region is VOC- or NO_x-limited. Furthermore, this analysis is performed for each county for the years 2012 and 2022 to determine if there has been a change in the oxidative nature and quantify the regional and local contributions to ozone over a 10-year period. All studied counties—except for Washington County—in Utah were found to be VOC-limited in 2012. This shifted in 2022 to most counties being either in a transitional state or being NO_x-limited. Local contributions to ozone increased in two major counties, Cache and Salt Lake Counties, but decreased in Carbon, Davis, Duchesne, Uinta, Utah, Washington, and Weber Counties. Generally, the regional contributions to oxidant concentrations decreased across the state. A summertime spike in both regional and local contributions to oxidants was seen. Smoke from wildfires was seen to increase the regional contributions to oxidants and shift the local regime to be more NO_x-limited. Full article

Fourteen Indian cities, including urban and rural locations, were chosen for the present study across India, with unhealthy air quality based on National Air Quality Index (NAQI > 100). However, it was found that NAQI values over the locations are driven by the undifferentiated mass concentration of particulate matter (PM, both PM${}_{10}$ and PM${}_{2.5}$) than other criteria pollutants. The PM${}_{2.5}$ and PM${}_{10}$ concentration during the winter violated the National Ambient Air Quality Standards (NAAQS) of India by two to five times at six urban locations, with the mean daily PM${}_{2.5}$ concentration averaged over the month; the the largest being at Patna (353 µg m${}^{-3}$) during the winter and lowest at Bengaluru (27 µg m${}^{-3}$) during the summer. The analysis of chemical species, in general, indicated NO${}_2$ (SO${}_2$, CO) as having a 25% to 70% (16% to 50%, 16% to 85%) increase in concentration from the summer to winter, which is adequately reflected in higher fuzzy scores during the winter. Thus, to provide a realistic approach to air quality management, the present study focuses on identifying priority-based locations requiring immediate mitigation measures by developing a Prioritized Clean Air Assessment Tool (PCAT). The tool utilizes a fuzzy-based algorithm to incorporate the cumulative effect of all six criteria pollutants, taking into consideration the severity of their expected health implications. Using PCAT, Delhi and Varanasi cities are identified for prioritized mitigation considering the NAAQS of India, unlike all cities (except Bengaluru) during the winter and nine out of fourteen cities during the summer, considering the NAQI. Using more stringent WHO guideline values in PCAT, six cities out of fourteen were identified requiring immediate mitigation during the winter and summer months; locations such as Solapur and Patna are identified to need season-specific mitigation measures during the summer and winter, respectively. The tool is simplistic, user-friendly, and quickly evaluates multiple locations simultaneously to provide priority sites. Full article

This study reports the mass concentrations, elemental characterization and identification of the possible sources of PM_2.5 and PM₁₀ at a suburban site in Pathum Thani, Thailand. The sampling was done from 18 February 2021 to 14 September 2021. PM_2.5 concentrations were between 0.39 μg/m³ and 174.26 μg/m³, while PM₁₀ concentration ranged from 12.75 μg/m³ to 242.02 μg/m³. The average concentration of PM_2.5 in the wet season (61.96 μg/m³) in the study area exceeded the national ambient air quality standards (NAAQS). Particle-induced X-ray emission (PIXE) was used to measure the element concentrations. The main elements, namely Fe, K, Cr and Ca, in both PM_2.5 and PM₁₀ showed significantly higher concentrations in the summer season. A qualitative inter-elemental correlation analysis, principal component analysis (PCA) and cluster analysis (CA) were applied for source identification of PM_2.5 and PM₁₀. The results for the three procedures were in good agreement. Four and three factors of sources were isolated by the PCA for PM_2.5 and PM₁₀, respectively. The main sources identified by PCA were, for PM_2.5, soil dust and biomass burning (32%), road dust and industrial emission (25%), vehicle and industrial emission (10%) and soil dust (9%); for PM₁₀, road dust and industrial emission (36%), crustal and biomass burning (30%) and industrial sources (10%). Full article

Crop residue burning emits a variety of air pollutants that drastically affect air quality, both locally and regionally. To study the impact of crop residue burning, in the present study, concentrations of particulate matter (PM_2.5), trace gases (tropospheric ozone (O₃), nitrogen oxides (NO_x), carbon monoxide (CO), and volatile organic compounds (VOCs)) were recorded in Agra, a suburban downwind site. The study was conducted during the pre-harvest (15 September to 5 October 2021) and post-harvest periods (6 October to 10 November 2021). During the post-harvest period, PM_2.5 concentrations were recorded to be three to four times higher than the NAAQ Standards (35 µg/m³), while O₃ and VOC concentrations showed an increment of 16% and 30.4%, respectively. NO_x and CO concentrations also showed higher levels (19.7 ± 7.5 ppb and 1498.5 ± 1077.5 ppb) during this period. Moderate resolution imaging spectroradiometer (MODIS), along with air mass backward trajectory analysis (HYSPLIT Model), were used to detect fire hotspots that suggested that the enhanced pollutant levels may be due to the burning of crop residue in agricultural fields over the northwest Indo-Gangetic Plain (NW-IGP). Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX) analysis showed high K concentrations during the post-harvest period, which may be attributed to crop residue burning or biomass combustion. Full article

Texas was hit by a record-setting cold snap from the 14–17 February 2021 after three decades that resulted in power outages, disruption of the public water systems, and other cascading effects. This study investigates the unprecedented impact of winter storm Uri on power outages, air quality, and water systems in Texas, USA. Analysis of the Parameter Regression of Independent Slopes Model (PRISM) gridded climate data showed that the average daily freezing temperature range was 0–−19 °C on 14 February 2021, with severe levels (−17–−19 °C) occurring in the Texas High Plains. Our results showed that the extreme freezing temperature persisted from 14–17 February 2021, significantly affecting power operation and reliability, and creating power outages across Texas. Uri impacted the public water systems and air quality on time scales ranging from a few minutes to several days, resulting in 322 boiling notices. The air quality index level exceeded the standard limit by 51.7%, 61.7%, 50.8%, and 60% in Dallas–Fort Worth, Houston–Galveston, Austin, and Lubbock regions. The level of the pollutants exceeded the EPA NAAQS standard allowable limits during winter storm Uri. In general, this study gives information on the government’s future preparedness, policies, communication, and response to storm impacts on vulnerable regions and communities. Full article