PM10 Ratio Research Articles

Relationship between atmospheric pollution and polycyclic aromatic hydrocarbons in fresh snow during heavy pollution episodes in a cold city, northeast China

Air quality index (AQI) and air pollutants during two typical pollution episodes, and polycyclic aromatic hydrocarbons (PAHs) in fresh snow after each episode in the winter 2019 across Harbin City in northeast China were investigated to explore the co-environmental behaviors. Significantly greater values of AQI and PAHs were found in the more serious atmospheric pollution episode (episode Ⅱ), demonstrating that PAHs in fresh snow is a robust indicator. PM2.5 was the primary air pollutant in both episodes based on PM2.5/PM10 ratios, which might be attributed to fine particulate converted from gas-to-particle process. PM2.5 and 4-ring PAHs significantly positive correlated, indicating that airborne particulate PAHs were co-emitted and co-transported with atmospheric fine particles released from coal combustion and vehicular emission under low temperature and high relative humidity. 3- and 4- rings PAHs were dominant in episode Ⅱ, while 5- and 6- rings PAHs were found the lowest in both episodes. These characteristics reflected that long-range transportation of coal and biomass burning were from the surrounding areas, while vehicle exhausts were mainly from local emissions. Except for the impact of local pollution source emissions, the regional transport could make a greater contribution in a more serious pollution event.

Do heat waves worsen air quality? A 21-year observational study in Seoul, South Korea

Heat waves are generally known to deteriorate air quality. However, the impacts of heat waves on air quality can substantially vary depending on the characteristics of heat waves. In this study, we examine air quality changes in Seoul during heat waves and their associations with large-scale atmospheric patterns. For this, air quality data from 25 stations and meteorological data from 23 weather stations and reanalysis datasets during July and August of 2001–2021 are used. Under heat waves, the mean daily PM10, NO2, and CO concentrations decrease by 7.9 %, 6.1 %, and 4.6 %, respectively, whereas the mean daily PM2.5, O3, and SO2 concentrations increase by 4.1 %, 17.2 %, and 2.9 %, respectively. The atmospheric circulation under heat waves is less favorable for long-range transport of air pollutants to Seoul. The PM2.5/PM10 ratio increases under heat waves, indicating that the secondary formation of aerosols becomes more important under heat waves. 37 % of the heat wave days are accompanied by severe O3 pollution exceeding the O3 concentration standard in South Korea. There is a significant variability of air quality in Seoul within heat waves. The heat wave days with higher concentrations of PM2.5, PM10, O3, NO2, and CO than their non-heat wave means exhibit a prominent difference in large-scale atmospheric pattern from the heat wave days with lower concentrations. This difference is characterized by a zonal wave-like pattern of geopotential height, which is similar to the circumglobal teleconnection pattern known as one of the major patterns for heat waves in South Korea. This zonal wave-like pattern produces more stagnant conditions over Seoul.

Secondary sources of PM2.5 based on the vertical distribution of organic carbon, elemental carbon, and water-soluble ions in Bangkok

Ambient PM2.5 pollution can affect human health and the environment in global megacities. Secondary PM2.5 is produced by physical and chemical reactions of primary air pollutants. Sources of secondary PM2.5 in Bangkok have been considered in most on-target investigations for the control and management of air quality. This research aims to identify the vertical distribution of secondary PM2.5 sources in Bangkok, Thailand. Vertical distributions of PM2.5 in haze and non-haze periods were collected at different heights (30, 75, and 110 m above ground level) at the Air Pollutants Monitoring Tower, Kasetsart University (KU tower) between November 2020 and July 2021. The carbon components were analyzed by an OCEC analyzer using the IMPROVE thermal/optical reflectance (TOR) protocol, and the ionic species were determined by ion chromatography. The results showed that the organic carbon (OC) to elemental carbon (EC) ratios of PM2.5 tended to increase with altitude at 30, 75, and 110 m in the range of 2.0 - 7.7, 3.4 - 8.0 and 3.0 - 16.6, respectively. In the haze period (Jan-Feb 2021), the SOC within PM2.5 was the highest at 110 m which was 24.5%. In addition, the key components of SOC, NO3−, NH4+, and SO42− within PM2.5 were found in secondary aerosols in Bangkok. The chemical compositions indicated that secondary PM2.5 is mainly contributed by local vehicle exhaust (30 m) and long-range transported biomass burning (75 and 110 m). This research provides useful information that could be applied for urban secondary PM2.5 control and management.

Assessment of Air Pollution Levels during Sugarcane Stubble Burning Event in La Feria, South Texas, USA

Agricultural stubble burning is the third largest source of air pollution after vehicular and industrial emissions. Fine particulate matter (PM2.5), volatile organic compounds (VOCs), carbon monoxide (CO), nitrogen dioxide (NO2), and black carbon (BC) are some of the pollutants emitted during such burning events. The Lower Rio Grande Valley (RGV) region of South Texas is a major hub of agricultural activity, and sugarcane farming is one of them. Unfortunately, this activity results in episodic events of high air pollution in this low-resourced, Hispanic/Latino majority region of the U.S.–Mexico border. This study presents results from a sugarcane site in La Feria, South Texas, where the air quality was monitored before, during, and after the sugarcane stubble burning. Various parameters were monitored on an hourly basis from 24 February 2022 to 4 April 2022. Our results demonstrate high levels of all the monitored pollutants during the burning phase in contrast to the pre- and post-burning period. The black carbon levels went up to 6.43 µg m−3 on the day of burning activity. An increase of 10%, 11.6%, 25.29%, 55%, and 67.57% was recorded in the PM1, PM2.5, PM10, Black Carbon, and CO levels, respectively, during the burning period in comparison with the total study period. The absorption Ångström exponent value reached a maximum value of 2.03 during the burning activity. ThePM2.5/PM10 ratio was 0.87 during the burning activity. This study also highlights the importance for continuous monitoring of air quality levels due to stubble burning in the Lower Rio Grande Valley Region of South Texas.

An evaluation of the U.S. EPA's correction equation for PurpleAir sensor data in smoke, dust, and wintertime urban pollution events

Abstract. PurpleAir sensors (PASs) are low-cost tools to measure fine particulate matter (PM) concentrations and are now widely used, especially in regions with few regulatory monitors. However, the raw PAS data have significant biases, so the sensors must be calibrated to generate accurate data. The U.S. EPA recently developed a national correction equation and has integrated corrected PAS data onto its AirNow website. This integration results in much better spatial coverage for PM2.5 (particulate matter with diameters less than 2.5 µm) across the US. The goal of our study is to evaluate the EPA correction equation for three different types of aerosols: typical urban wintertime aerosol, smoke from biomass burning, and mineral dust. We identified 50 individual pollution events, each having a peak hourly PM2.5 concentration of at least 47 µg m−3 and a minimum of 3 h over 40 µg m−3 and characterized the primary aerosol type as either typical urban, smoke, or long-range transported dust. For each event, we paired a PAS sampling outside air with a nearby regulatory PM2.5 monitor to evaluate the agreement. All 50 events show statistically significant correlations (R values between 0.71–1.00) between the hourly PAS and regulatory data but with varying slopes. We then corrected the PAS data using either the correction equation from Barkjohn et al. (2021) or a new equation that is now being used by the U.S. EPA for the AirNow Fire and Smoke Map (U.S. EPA, 2022b). Both equations do a good job at correcting the data for smoke and typical pollution events but with some differences. Using the Barkjohn et al. (2021) equation, we find mean slopes of 1.00 and 0.99 for urban and smoke aerosol events, respectively, for the corrected data versus the regulatory data. For heavy smoke events, we find a small change in the slope at very high PM2.5 concentrations (> 600 µg m−3), suggesting a ∼ 20 % underestimate in the corrected PAS data at these extremely high concentrations. Using the new EPA equation, we find slopes of 0.95 and 0.88 for urban and smoke events, respectively, indicating a slight underestimate in PM2.5 using this equation, especially for smoke events. For dust events, while the PAS and regulatory data still show significant correlations, the PAS data using either correction equation underestimate the true PM2.5 by a factor of 5–6. We also examined several years of co-located regulatory and PAS data from a site near Owens Lake, California (CA), which experiences high concentrations of PM2.5 due to both smoke and locally emitted dust. For this site, we find similar results as above; the corrected PAS data are accurate in smoke but are too low by a factor of 5–6 in dust. Using these data, we also find that the ratios of PAS-measured PM10 / PM1 mass and 0.3 µm / 5 µm particle counts are significantly different for dust compared to smoke. Using this difference, we propose a modified correction equation that improves the PAS data for some dust events, but further work is needed to improve this algorithm.

Surface Microbial Contamination and Air Quality before and after Regular Cleaning Procedures

Studies on indoor air quality (IAQ) have linked exposure to microorganisms in indoor air to a variety of illnesses. The association between indoor air quality, surface contamination, and IAQ under heterogeneous cleaning procedures are all crucial factors that were investigated in this study. The ATP bioluminescence test demonstrated a significant correlation (r = 0.89; p 0.05) with bacterial count obtained from swab specimens and a moderate correlation (r = 0.57; p 0.001) with viable settling bacterial count. For the entire sample (pre- and post-cleaning), the ATP values were heterogeneous, averaging 230 RLU/100 cm2, 140 RLU/100 cm2, 120 RLU/100 cm2, 135 RLU/100 cm2, 99 RLU/100 cm2, and 80 RLU/100 cm2, in offices, classrooms, toilet doorknobs, reception desks, main lobbies, and exit doorknobs, respectively. An insignificant association between indoor and outdoor PM2.5 (r = 0.21; p 0.05), an I/O ratio of PM2.5 with an average value of 1.2, and an I/O ratio of CO2 exceeding 1 suggest a minor impact of outdoor air. After cleaning, the bacterial and fungal counts on indoor surfaces showed significant reduction, suggesting that the cleaning procedures were effective. The concentrations of VOC but not HCHO in indoor air were significantly affected by cleaning, but not by temperature or relative humidity (RH). We propose ATP bioluminescence as a surrogate for detecting bacterial contamination rather than fungal contamination, which requires additional validation. We suggest that the results of active microbial sampling (in CFU/m3) and settling plates (in CFU/m2/h) be interpreted independently to avoid confusion.

Weekend effect of air pollutants in small and medium-sized cities: The role of policies stringency to COVID-19 containment

Although the pattern of air pollutants has been extensively studied during the COVID-19 pandemic, the weekend effect has been rarely investigated. In order to understand the impact of policies stringency as well as the interruption-recovery pattern, the aim of the study was to investigate the levels of air pollutants (O3, NO2, SO2, PM2.5, PM10) and PM2.5/PM10 ratio before and after the COVID-19 pandemic in four cities in the state of Rio Grande do Sul, Brazil, evaluating the weekend effect at these two scenarios and also identifying how the restriction measures applied locally had an impact on this effect. For this, daily data from two years of monitoring of air pollutants were collected and the weekend effect was calculated based on the levels from Monday to Friday (weekday) and Saturday and Sunday (weekend). There was a positive weekend effect for almost all criteria air pollutants in the four cities, and an intrinsic relation between the weekend effect and the restriction measures adopted. A negative weekend effect was observed in the scenario characterized by less restrictive and more permissive policies for daily and occupational activities. Conversely, when more stringent measures were implemented, this trend was reversed and higher intensities of positive weekend effect were observed as restrictions increased. In conclusion, the COVID-19 perturbation to air quality changed as regions tighten and loosen restrictions on human mobility. These insights that can guide responsible authorities about future strategies and policies for air quality control.

Performance of Cold Atmospheric Plasma in Reducing Airborne Particles and Carbon Dioxide Concentrations in Sports Facilities

According to a few reports recently published, cold atmospheric pressure plasma (CAP) is a state-of-the-art technique in the field of environmental science. Studies reported the performance of CAP in the removal of particulate matter (PM) and microorganisms, including fungi, bacteria, and viruses. The CAP also effectively removed the odor, volatile organic compounds (VOCs), and numerous chemicals, including formaldehyde. However, studies on the control of PM and carbon dioxide (CO₂) in sports facilities are limited. This study was conducted in two parts. In Part 1, the levels of indoor PM10, PM2.5, PM1.0, and CO₂ were measured in two sports facilities, including a table tennis center and a fitness center, to determine the occupants’ exposure levels to the pollutants. In part 2, the performance of the CAP technique in the reduction of airborne concentrations of PM10 and CO₂ was investigated. The PM10 concentrations were significantly higher in the fitness center than in the table tennis center. The concentration ratios of PM10, PM2.5, and PM1.0 to PM10 concentrations were 1.00, 0.95, and 0.81, respectively. The CO₂ concentrations were significantly higher in table tennis centers where aerobic exercise was predominant. The performance of CAP on the removal of PM10 and CO₂was highly promising. The average reduction rates against PM10 and CO₂ concentrations were 69% and 35%, respectively. Further studies on the performance of CAP against other pollutants, such as total volatile organic compounds and microorganisms in sports facilities are needed.

The Impact of Local Environment and Neighboring Pollution on the Spatial Variation of Particulate Matter in Chinese Mainland

Particulate matter (PM) pollution has caused several environmental problems and damaged human health. To understand the different driving forces of PM2.5 and PM10, we investigated the spatial distribution of PM2.5, PM10, and the ratio of PM2.5 to PM10 (PM2.5/PM10), and simulated how they respond to socioeconomic, natural conditions and pollutant transmission in 336 cities across Chinese mainland in 2017. The results indicated that 35.4% and 49.7% of cities in Chinese mainland satisfied the national level II standard for PM2.5 (35 μg/m3) and PM10 (70 μg/m3), respectively. The average PM2.5/PM10 was 57.5 ± 9.4%, which is a relatively high value across the world. Global spatial regression results revealed that the transport of pollutants emitted from neighboring regions was the most important factor for local PM concentrations, while population density was the dominant local variable. The influence of socioeconomic factors and the neighboring pollution level on PM2.5 was greater than that on PM10, while the effect of precipitation was greater on PM10. Cluster analysis revealed that 336 Chinese cities could be classified into three groups. The regions with a high PM concentration and a high level of social economy were included in Group 1 (G1). Group 2 (G2) was predominantly observed in southern China, while Group 3 (G3) was seen in western China. Furthermore, population density significantly affected the PM in G2 and PM2.5 in G3, and PM levels in G1 and G3 had a sensitive response to the variation in precipitation, especially PM10.

Analysis of fine particulate matter blocking effect by air curtain at school entrance through experimental measurement

Fine particulate matter is classified as a first-class carcinogen and is receiving global attention. In particular, particulate matter (PM2.5, and PM10) are more fatal in students at a growing age while their respiratory system develops than in ordinary adults. During school hours, the main entrance is often left open for the convenience of students and staff. In this situation, the inflow of PM2.5 through the main entrance increases significantly. Thus, air curtains are widely used at the main entrance to block the inflow of PM2.5. However, few experimental studies have examined the effect of blocking PM2.5 through such air curtains. This study analyzed the effectiveness of reducing PM2.5 inflow by installing an air curtain at the main entrance of a school. The efficiency in blocking PM2.5 was determined by analyzing the average I/O ratio of PM2.5 at the respiratory height through experimental measurements. The average I/O ratio of PM2.5 in the school entrance was 0.84 before the installation of the air curtain, which was reduced to 0.46 after installing the air curtain. The blockage efficiency of the air curtain was 42%. This study quantitatively confirms that air curtains effectively reduce the inflow of PM2.5 in schools.

PS-C35-1: SPOT URINE SODIUM: CREATININE RATIO: A SIMPLE METHOD TO ESTIMATE SODIUM INTAKE

Objective: High sodium intake is a worldwide problem and contributes to high blood pressure and target organ damage. Measurement of 24-hour urine sodium excretion is gold standard for sodium intake evaluation but it is difficult to practice. In this study, the correlation between spot urine sodium: creatinine ratio from second void (AM), before dinner (PM), before bedtime (HS) and 24-hr samples with 24-hour urine sodium were evaluated. Methods: The participants were recruited from single hospital. Participants with age > 20 years, eGFR > 60 ml/min/1.73 m2 and no history of diuretics use were included. Urine sodium, urine creatinine and urine volume of each sample were measured. Urine sodium (mmol/L): urine creatinine (mg/dL) ratio of AM, PM, HS and 24-hour samples were calculated. Correlations of each ratio with 24 hour urine sodium (mmol/day) were studied by Pearson correlation coefficients. Results: 43 participants were included in this study. Mean age was 46.9 ± 13.6 years. Hypertension was diagnosed in 31 participants (72%). Mean blood pressure was 134 ± 15/81 ± 9 mmHg. Estimated eGFR was 100 ± 16 ml/min/1.73 m2. Mean 24 hour urine sodium was 178 + 92 mmol/day (equivalent to sodium intake 4,094 + 2,116 mg/day). Urine sodium: creatinine ratio of AM, PM, HS and 24-hr samples (correlation coefficient, r, with 24-hour urine sodium excretion) were 1.6 ± 0.8 (r = 0.11, P = 0.49), 1.9 ± 1.1 (r = 0.71, P < 0.001), 1.7 ± 1.1 (r = 0.59, P < 0.001) and 1.8 ± 0.7 (r = 0.77, < 0.001) respectively. Spot urine sodium: creatinine ratio from PM sample cut-off point of 1.2 had sensitivity of 81% and specificity of 73% to determine 24-hr urine sodium of 100 mmol/day. Conclusions: Spot urine sodium: creatinine ratio from PM sample correlates well with 24-hr urine sodium (r = 0.62) and ratio of 1.2 is equivalent to 24-hr urine sodium of 100 mmol/day. Sodium intake of study participants was 178 mmol/day which higher than recommended level.

Chemical composition, levels, and I/O ratios of PM10 and PM2.5 in the laboratory near the copper smelter in Bor, Serbia

Numerous studies have reported that particulate matter and its specific chemical constituents were linked to the incidence of respiratory diseases and mortality and lung function. The main aim of this study is to determine metallic content in PM10 and PM2.5 samples taken simultaneously at several locations in the close vicinity of the copper smelter in Bor and the influence of outdoor PM pollution on indoor PM levels. The measurement campaign was conducted, during the non-heating season of 2020. PM samples were collected at all sampling sites with low-volume samplers (Sven/Leckel LVS3) on quartz fiber filters (Whatman QMA, 47mm). All samples were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP MS). In this way, the mass concentrations of 4 priority elements (As, Cd, Pb, and Ni) in PM samples were identified and quantified. It has been determined that average indoor PM levels in the laboratory were higher than outdoors. A strong correlation was found between PM10 and PM2.5 particle levels inside the laboratory and in the outdoor air. Also, a very strong correlation was found between the levels of Pb, Ni, As, and Cd determined in PM10 and PM2.5 samples inside the laboratory and in the outdoor air. This confirms that mentioned elements originate from the same sources located in the copper smelter complex.

Comparison of PM2.5 Monitoring Data Using Light Scattering and Beta Attenuation Methods: A Case Study in Seoul Metro Subway

A study on monitoring PM2.5 concentrations at an underground subway station using light scattering and beta attenuation methods was conducted. Six optical particle counters (OPCs), which were representative of the light scattering method and had 16 size channels, were installed at different sampling sites in the waiting room and platforms to compare PM2.5 concentrations, determine PM2.5 /PM10 ratios, and characterize the size distribution based on particle number. In terms of the beta attenuation method, a beta-ray attenuation monitor (BAM) was set up at the platform to compare it with OPCs for one month. It was found that 1h-average PM2.5 concentrations varied at different sampling sites depending on PM composition, while 24h-average PM2.5 concentrations were independent of the sampling sites. There was a significant difference between the means of 1h-average PM2.5 concentrations observed by the BAM and OPC when PM2.5 contributed to less than 50% or higher than 80% of PM10. In contrast, the 24h-average PM2.5 concentrations observed by the BAM and OPC showed the same patterns as each other with an insignificant difference. Therefore, an OPC can be used to monitor the 24h-average PM2.5 concentration in an underground subway station. However, the use of OPC to measure the 1h-average PM2.5 concentration should consider PM composition and other factors. In addition, more frequent calibration is needed on a regular basis.

Indoor Particle's Pollution in Bucharest, Romania.

Air pollution risk factor on human health was surpassed only by high blood pressure, tobacco use and poor diet. Total number of deaths due to air pollution worldwide was estimated to 6.67 million people in 2019. In the European Union, 97% of the urban population is exposed to levels of fine particulate matter above the latest guideline levels set by the World Health Organization. Air pollution accounts for 20% of newborn deaths worldwide, most related to complications of low birth weight and preterm birth. Low birth weight and preterm birth are responsible for 1.8 million deaths worldwide. Bucharest is the capital city of Romania and one of the most polluted cities in Europe, ranking in the 9th position out of 96 of the top cities from Europe and in the 4th position out of 32 of the top cities in Eastern Europe, data from June 2022. The aim of this study was to measure the real time level of indoor particulate pollution levels in different indoor environments from Bucharest, during the pandemic period. The PM2.5/PM10 ratio and its rate of change were also determined for the measured data. The PM2.5/PM10 ratio and its rate of change were also calculated based on the measurement data. The PM2.5/PM10 ratio showed an upward trend on weekends compared to weekdays, suggesting a relationship with outdoor PM where leisure activities and traffic infiltrated the indoors. The fluctuation range of the PM2.5/PM10 ratio was 0.44~0.95, and low measured values were detected on weekdays. Of the seasons, the proportion of particulate in autumn and its rate of change tended to be higher than in summer. It was suggested that outdoor air may have permeated the room. In addition, the relationship was considered, such as it is a holiday period, there are few rainy days, the concentration of coarse particles is high, and the number of residents in the city decreases. When it comes to indoor air quality, the higher this ratio, the more serious the air pollution. PM10 concentrations decreased by 29.1% in the absence of human activity and increased by 35.1% in the presence of humans. PM2.5 concentration decreased by 30.3% without human activity and increased by 3.1% with the presence of humans. Certain trends were suggested for the resumption of human activity and an increase in PM2.5 concentrations. The average relative difference between October 2021, a pandemic period, and October 2022, a post pandemic period, was 64% for PM10 and 47% for PM2.5. The pandemic period brought a significantly better indoor air quality from the particulate pollution point of view.

Investigation of the particulate air pollution and the ratio of PM2.5 to PM10 concentrations in the atmosphere over the lignite mining and lignite-fired power plants region of Western Macedonia, Greece.

The lignite long-lasting exploitation has resulted in a series of negative impacts on the air quality of the lignite basin of Ptolemaida, Amynteo and Florina. The coal-fired plants in this region are the greatest sources of air pollutants, such as SO2, NOX, CO2, PM, heavy metals and fly ash. In this study, we investigate the air quality of Western Macedonia based on measurements of PM2.5 and PM10 in ten air quality monitoring stations (Filotas, Koilada, Oikismos, Petrana, Komi, Amyntaio, Florina, Vevi-Meliti, Pontokomi and Anargyroi) which are located in the broader area of the lignite power plants. The trends of PM time series over a 12-year period (2010-2021) show a gradual decrease of PM2.5 and PM10 concentrations following the decline of lignite production in Greece. In order to characterize the underlying atmospheric and anthropogenic processes affecting the PM concentrations we assessed the ratios of PM2.5 to PM10. The high ratios of PM2.5/PM10 indicate a major contribution of fine particles attributable to anthropogenic air pollution sources, while small ratios indicate that coarse particles are dominant, which might be related to natural sources of air pollution. We found that average PM2.5/PM10 ratios during the study period ranged between 0.48 in Oikismos and 0.70 in Florina and Vevi-Meliti. For Florina and Vevi-Meliti, the daily PM2.5/PM10 ratios were found to reach the value of 1.0, while the daily average ratios of PM2.5/PM10 were above 0.9 for almost the 15 % of the days in these sites. In the other sites high daily ratios of PM2.5/PM10 were found for a lesser number of days. The high ratios which have been found at these sites indicate the considerable contribution of energy combustion for heating purposes and other anthropogenic processes. Overall, we used the PM2.5/PM10 ratio to characterize the processes affecting the air quality within the local environment.

Impact of ventilation methods on indoor particle concentrations in a daycare center.

The objective of this study was to quantify the influence of ventilation methods on children's exposure to indoor particles in a daycare center located in an urban area. The ventilation methods applied to the center were monitored for 1 year. It appears that indoor PM10 and PM2.5 concentrations of the center were basically determined by outdoor conditions. The fluctuations in outdoor particle concentration also affected the ventilation behavior during class. The windows and doors of the classroom were frequently closed during both class hours and nights when the outdoor particle concentrations were at high levels. Statistically significant differences in the I/O ratios were found among the ventilation methods. The PM10 I/O ratio with the closed windows was significantly higher (p < 0.01) than that with the open windows, and when the mechanical fans were operated, the I/O ratio dramatically decreased (p < 0.01). The I/O ratio of PM2.5 showed a similar trend to that of PM10 except for the mechanical fan operation. The filters rated lower than MERV 11 appear to be insufficient to remove submicron particles from the mechanically supplied outdoor air when the PM2.5 concentrations are high, such as during the heating period.

Particulate matter concentrations and characterization in urban subway system-case study Tehran, Iran.

The present work aims to evaluate the indoor and outdoor air quality in the stations of the Tehran subway system. In this study, the particulate sampling of the four Tehran subway stations was conducted in March-July 2018 during different seasons to determine indoor and outdoor PM10 and PM2.5 concentrations and elemental composition. The samples were analyzed to determine 11 elements such as Pb(Lead), Cd(Cadmium), Ni(Nickel), Co(Cobalt), Mn(Manganese), Zn(Zink), Fe(Iron), Cu(Copper), As(Arsenic), Al(Aluminum) and Cr(Chromium) qualitatively. The experimental results indicated that the average concentrations of both PM10 and PM2.5 in indoor stations (platforms) were approximately 2-5 times higher than those in the outdoors (ambient air). In addition, PM10 and PM2.5 concentrations exceeded the daily-standard values (US-EPA; PM10 = 50µg.m-3, PM2.5 = 25µg.m-3) in 100% indoor measurements and 84% outdoor measurements. Moreover, the average indoor PM10 and PM2.5 concentrations in weekday values were 1.4 and 1.5 times higher than those measured on weekends, which may be related to the lower frequency of trains. Further, indoor and outdoor correlation of PM10 concentrations (Pearson r = 0.6) was more than that of PM2.5 concentrations (Pearson r = 0.2), indicating the additional sources for PM2.5 in indoor stations. Additionally, the average PM2.5 / PM10 ratio was 0.52 for indoor measurements and 0.34 for outdoors, indicating that PM10 particles were the dominant particle type in both sampling areas and passengers in indoor stations exposed to higher PM2.5 concentrations than those in outdoor stations. Finally, based on elemental analysis, Fe was the most enriched element in indoor and outdoor PM10 and PM2.5 samples. The concentration of Fe ranged from 16 to 81µg.m-3in indoor stations and0.6 to 2.5µg.m-3in outdoors. Other enriched elements were Al, Cu, Zn, and Mn, respectively.

Air Pollution Characteristics during the 2022 Beijing Winter Olympics.

Using air pollution monitoring data from 31 January to 31 March 2022, we evaluated air quality trends in Beijing and Zhangjiakou before and after the 2022 Winter Olympics and compared them with the conditions during the same period in 2021. The objective was to define the air quality during the 2022 Winter Olympics. The results indicated that: (1) the average concentrations of PM2.5, PM10, NO2, CO, and SO2 in Zhangjiakou during the 2022 Winter Olympics were 28.15, 29.16, 34.96, 9.06, and 16.41%, respectively, lower than those before the 2022 Winter Olympics; (2) the five pollutant concentrations in Beijing showed the following pattern: during the 2022 Winter Olympics (DWO) < before the 2022 Winter Olympics < after 2022 Winter Paralympics < during 2022 Winter Paralympics; (3) on the opening day (4 February), the concentrations of the five pollutants in both cities were low. PM2.5 and PM10 concentrations varied widely without substantial peaks and the daily average maximum values were 15.17 and 8.67 µg/m3, respectively, which were 65.56 and 69.79% lower than those of DWO, respectively; (4) the PM2.5 clean days in Beijing and Zhangjiakou DWO accounted for 94.12 and 76.47% of the total days, respectively, which were 11.76 and 41.18% higher than those during the same period in 2021; (5) during each phase of the 2022 Winter Olympics in Beijing and Zhangjiakou, the NO2/SO2 and PM2.5/SO2 trends exhibited a decrease followed by an increase. The PM2.5/PM10 ratios in Beijing and Zhangjiakou were 0.65 and 0.67, respectively, indicating that fine particulate matter was the main contributor to air pollution DWO.

Temporal variations in the geochemistry of Mesozoic mafic–intermediate volcanic rocks in the northern Great Xing'an Range, Northeast China, and implications for deep lithospheric mantle processes

Identifying the composition of the recycled materials in the lithospheric mantle is crucial for establishing links between mantle geochemical ‘reservoirs’ and deep mantle geodynamic processes. However, studies that focus on deep mantle processes under multiple subduction tectonic regimes have been absent. In this paper, we present 40 Ar/ 39 Ar age, whole-rock geochemical, and Sr–Nd–Pb–Hf isotope, zircon Hf-O isotope, and in situ plagioclase Pb isotope data for Mesozoic mafic–intermediate volcanic rocks in the northern Great Xing'an Range, northeast China. These and published data are used to constrain the deep processes that occurred in the lithospheric mantle during the Mesozoic, in the context of the evolution of the Mongol–Okhotsk Ocean and whether subduction of the Paleo-Pacific Plate affected the formation of volcanic rocks in the western part of northeast China. The Mesozoic mafic–intermediate volcanic rocks in the northern Great Xing'an Range can be divided into three stages: Early Jurassic (~180 Ma), Late Jurassic (~155 Ma), and late Early Cretaceous (~120 Ma). These rocks are mainly basalt, basaltic andesite, andesite, and trachyandesite. The Mesozoic mafic–intermediate volcanic rocks have SiO 2 = 47.34–60.00 wt%, TFe 2 O 3 = 4.73–11.63 wt%, and Mg # = 26–66, belong to the medium- to high-K calc-alkaline series, exhibit enrichment in light rare earth elements and large-ion lithophile elements, exhibit depletions in heavy rare earth elements and high-field-strength elements (e.g., Nb and Ta), and have no obvious Eu anomalies. These geochemical features are similar to those of arc igneous rocks. Relative to mid-ocean ridge basalts, these mafic–intermediate volcanic rocks exhibit more radiogenic Sr-Pb and less radiogenic Nd-Hf isotopic compositions. The Th/Yb (1.47–3.43) and (Hf/Sm) PM (0.80–1.15) ratios of the Early Jurassic mafic–intermediate volcanic rocks are much lower than those of the Late Jurassic mafic–intermediate volcanic rocks (Th/Yb = 4.31–5.25; (Hf/Sm) PM = 1.49–2.60), whereas the late Early Cretaceous igneous rocks exhibit large variations in these ratios (Th/Yb = 0.37–14.8; (Hf/Sm) PM = 0.59–2.14). The above features show that: (1) the primary magmas of the mafic–intermediate volcanic rocks were mainly derived by partial melting of depleted lithospheric mantle; (2) the lithospheric mantle was mainly metasomatized by sediment-derived fluids related to subduction of the Mongol–Okhotsk oceanic plate during the Early Jurassic, whereas the mantle source was mainly modified by sediment-derived melts triggered by the collapse of thickened lithosphere after closure of the Mongol–Okhotsk Ocean in the Late Jurassic; and (3) sediment-derived fluids associated with subduction of the Paleo-Pacific Plate caused further enrichment of the lithospheric mantle in the western part of northeast China during the late Early Cretaceous. • J 1 , J 3 and K 1 mafic magmas were derived by melting of depleted lithospheric mantle. • J 1 lithospheric mantle was modified by the Mongol-Okhotsk slab-derived fluid. • J 3 lithospheric mantle was modified by the Mongol-Okhotsk slab sediment-derived melt. • K 1 lithospheric mantle was re-modified by the Paleo-Pacific slab-derived fluid.

Occurrence and characteristics of atmospheric microplastics in Mexico City

While atmospheric microplastics have attracted scientific attention as a significant source of microplastic contamination in the environment, studies in large population centers remain sparse. Here we present the first report on the occurrence and distribution of atmospheric microplastics in Mexico City (Latin America's second most densely populated city), collected using PM10 and PM2.5 active samplers at seven monitoring stations (urban, residential, and industrial) during the dry and wet seasons of 2020. The results showed that microplastics were detected in all of the samples examined, with mean microplastic concentrations (items m−3) of 0.205 ± 0.061 and 0.110 ± 0.055 in PM10 and PM2.5, respectively. The spatial distribution of microplastics showed seasonal variation, with greater abundances in locations closer to industrial and urban centers. There was also a significant difference in microplastic concentrations in PM10 and PM2.5 between the dry and wet seasons. The mean PM2.5/PM10 ratio was 0.576, implying that microplastics were partitioned more towards PM2.5 than PM10 in Mexico City. Fibers were the most prominent shape (>75 %), and blue was the most common color (>60 %). The size characteristics indicated microplastics of varying lengths, ranging from 39 to 5000 μm, with 66 % being <500 μm. Metal contaminants such as aluminum, iron, and titanium were detected using SEM-EDX on randomly selected microplastics. The microplastics were identified as cellophane, polyethylene, polyethylene terephthalate, polyamide, and cellulose (rayon) using ATR-FTIR spectral analysis. Our findings unravel the extent and characteristics of atmospheric microplastics in the Mexico City metropolitan area, which will aid future research to better understand their fate, transport, and potential health risks, demanding more investigations and close monitoring.