Average Mass Concentrations Of PM2 Research Articles

Insight Study of Trace Elements in PM2.5 During Nine Years in Delhi, India: Seasonal Variation, Source Apportionment, and Health Risks Assessment.

This study investigated the concentrations, seasonal variations, sources, and human health risks associated with exposure to heavy elements (As, Al, Pb, Cr, Mn, Cu, Zn, and Ni) of PM2.5 at an urban location of Delhi (28° 38' N, 77° 10' E; 218m amsl), India, from January 2013 to December 2021. The average mass concentration of PM2.5 throughout the study period was estimated as 127 ± 77µgm-3, which is exceeding the National Ambient Air Quality Standards (NAAQS) limit (annual: 40µgm-3; 24h: 60µgm-3). The seasonal mass concentrations of PM2.5 exhibited at the order of post-monsoon (192 ± 110 µgm-3) > winter (158 ± 70 µgm-3) > summer (92 ± 44 µgm-3) and> monsoon (67 ± 32 µgm-3). The heavy elements, Al (1.19µgm-3), Zn (0.49µgm-3), Pb (0.43µgm-3), Cr (0.21µgm-3), Cu (0.21µgm-3), Mn (0.07µgm-3), and Ni (0.14µgm-3) exhibited varying concentrations in PM2.5, with the highest levels observed in the post-monsoon season, followed by winter, summer, and monsoon seasons. Six primary sources throughout the study period, contributing to PM2.5 were identified by positive matrix factorization (PMF), such as dust (paved/crustal/soil dust: 29.9%), vehicular emissions (17.2%), biomass burning (15.4%), combustion (14%), industrial emissions (14.2%), and Br-rich sources (9.2%). Health risk assessments, including hazard quotient(HQ), hazard index(HI), and carcinogenic risk(CR), were computed based on heavy elements concentrations in PM2.5. Elevated HQvalues for Cr and Mn linked with adverse health impacts in both adults and children. High carcinogenic risk values were observed for Cr in both adults and children during the winter and post-monsoon seasons, as well as in adults during the summer and monsoon seasons. The combined HIvalue exceeding one suggests appreciable non-carcinogenic risks associated with the examined elements. The findings of this study provide valuable insights into the behaviour and risk mitigation of heavy elements in PM2.5, contributing to the understanding of air quality and public health in the urban environment of Delhi.

Characteristics of Fine Particulate Matter (PM2.5) Chemical Composition in the North Jakarta Industrial Area

Air pollution around industrial area has become a serious concern for both the public and local government. Thus, research on PM2.5 characterization is urgently needed. This study identifies the concentration and chemical characteristics of PM2.5 to provide an in-depth understanding of the composition of these particles around the largest industrial complex in North Jakarta. Sixty samples of PM2.5 were collected from residential sites around industrial areas in North Jakarta. Samples were collected on Teflon filters using a SuperSASS instrument during the period from February to July 2023, representing the wet and dry seasons. Mass concentrations of PM2.5, black carbon, and 19 chemical elements were determined. The average mass concentration of PM2.5 in the wet and dry seasons was 27.81±11.82 µg/m3 and 46.63±14.37 µg/m3, respectively. Although the concentration of PM2.5 was lower during the wet season, the concentrations of black carbon and certain elements did not decrease significantly. This shows that pollutants play an important role in both seasons in the study location. Sulfur is the most abundant element with the average concentration in the dry season (2,727.89 ng/m3) higher than in the wet season (1,983.18 ng/m3). The PM2.5 mass reconstruction results show that ammonium sulfate and black carbon have the largest portion of PM2.5 mass. The results are expected to be used as a scientific reference in studying air pollution problems in this region and assist in formulating air protection policies to reduce PM2.5 emissions.

Indoor air quality and sick-building syndrome at a metro station in Tianjin, China

Metro systems play a crucial role in public transportation worldwide. Given that metro stations are unique built environments with a significant volume of daily commuters, ensuring a satisfactory air quality in these spaces becomes paramount. This study involved measurements of indoor air quality (IAQ), staff satisfaction, particulate matter (PM) chemical composition, and heavy metal health risks at a typical metro station in Tianjin over two seasons. Although the air exchange rate was sufficient to maintain a CO2 concentration less than 1000 ppm, the proportion of staff reporting no sick-building symptoms decreased from 83 % in spring to 25 % in winter. An average mass concentration of PM with an aerodynamic diameter smaller than 2.5 μm (PM2.5) of 68.0 ± 42.2 μg/m3 and an average PM1 mass concentration of 51.8 ± 33.3 μg/m3 were observed on the platform in winter. PM2.5 contained more metal in winter than in spring. PM2.5 in winter contained more metal in winter than in spring. With a lower relative humidity in winter, the coefficient of friction between railway wheels and rails increased, thus increasing particle emission. The carcinogenic risk of Cr on the platform was unacceptable. Moreover, the health risks induced by Ba should be investigated. The findings indicate that PM control at metro stationss, particularly on platforms in winter, should be emphasized.

Chemical composition, sources and formation mechanism of urban PM2.5 in Southwest China: a case study at the beginning of 2023

Abstract. Despite significant improvements in air quality in recent years, the Sichuan Basin (SCB) is still facing frequent haze pollution in winter, and the causes of severe haze formation have not yet been fully investigated. In this study, the chemical components of PM2.5 (i.e., particulate matter with an aerodynamic diameter of less than 2.5 µm) in a typical pollution period at the beginning of 2023 in Chengdu, a megacity in the SCB, were characterized by bulk-chemical and single-particle analysis, and the PM2.5 sources and formation mechanism of pollution were analyzed. The average mass concentration of PM2.5 during the study period was 95.6 ± 28.7 µg m−3. Organic matter (OM) was the most abundant component (35.3 %), followed by nitrate (22.0 %), sulfate (9.2 %) and ammonium (7.8 %). The individual aerosol particles were classified into five categories, i.e., mineral, OM, secondary inorganic aerosol (SIA), soot and fly ash/metal particles, and most of them were in the state of being internally mixed. The entire observation period could be divided into two non-pollution periods (NP-1 and NP-2) and two haze periods (Haze-1 and Haze-2). With the evolution of pollution, the bulk-chemical and single-particle analysis exhibited similar characteristics, suggesting that Haze-1 was mainly caused by pollutants related to fossil fuel combustion, especially local mobile sources, while Haze-2 was triggered by the rapidly increasing secondary pollutants, which mainly came from regional transmission. The PM2.5 sources included dust (8.5 %), biomass burning (3.5 %), coal combustion (15.4 %), industrial processes (6.5 %), vehicular emissions (25.6 %) and secondary sources (40.5 %). Analysis of Weather Research and Forecasting model with Chemistry (WRF-Chem) model results showed that the average contributions of local sources and regional transmission to pollution in Chengdu were the same (50 % vs. 50 %). In addition, the source composition and WRF-Chem simulation results in different periods confirmed our analysis of the formation mechanisms of the two haze events. This study confirms that further significant reductions in PM2.5 in Chengdu are still needed, and more effective policies for local emission reduction or joint prevention and control of regional air pollution will be necessary in the future.

Characteristics and Source Apportionment of Carbonaceous Aerosols in the Typical Urban Areas in Chongqing During Winter

To investigate the characteristics, source apportionment, and potential source areas of carbonaceous aerosols in Chongqing during winter, PM2.5 samples were collected from January 2021 to February 2021 in the urban areas of Wanzhou (WZ), Yubei (YB), and Shuangqiao (SQ). The results showed that the average mass concentrations of PM2.5, OC, and EC in SQ were (72.6 ±33.3), (18.2 ±8.2), and (4.4 ±1.7) μg·m-3, respectively, higher than those in WZ[(67.2 ±30.3), (17.2 ±7.4), and (5.1 ±2.4) μg·m-3] and YB[(63.4 ±25.7), (15.4 ±6.3), and (4.2 ±1.9) μg·m-3]. Compared with that during the clear period, the concentration and fraction of EC in total carbon increased by 103.0% and 8.1%, respectively, in WZ compared to that in other areas during pollution period, whereas the OC/EC ratio was decreased significantly (-10.5%), indicating that the primary emission of carbonaceous aerosols increased significantly during the pollution period. The average mass concentrations of secondary organic carbon (SOC) in SQ and YB were (7.7 ±4.8) μg·m-3 and (6.9 ±2.8) μg·m-3 significantly higher, respectively, than that in WZ[(4.5 ±1.9) μg·m-3] during the campaign. This indicated that the secondary transformation had a greater influence on the carbonaceous aerosols in SQ and YB than that in WZ. Furthermore, in contrast to that in WZ, the ratios of SOC/OC were increased with the increase in PM2.5 concentrations, and significant correlations between SOC concentration and aerosol water content, NO2 concentration, and the value of NOR were observed in SQ and YB (P < 0.01), indicating that the increasing of carbonaceous aerosol concentrations might be mainly driven by the SOC with -NO2 groups produced by aqueous chemical reactions during winter in SQ and YB. The positive definite matrix factor (PMF) results in these urban areas showed that the contribution of biomass/coal combustion source in WZ (47.4%) was significantly higher than that in YB (34.2%) and SQ (38.1%), whereas the gasoline motor vehicle emission and secondary transformation impacts were more significant in YB. The results of the concentration weighted trajectory (CWT) showed that the potential sources of carbonaceous aerosols were mainly the local and northeastern parts of these urban areas (such as Changshou).

Characterization of carbonaceous particles by single particle aerosol mass spectrometer in the urban area of Chengdu, China.

Carbonaceous particles are an important chemical component of atmospheric fine particles. In this study, a single particle aerosol mass spectrometer was used to continuously measure the carbonaceous particles in Chengdu, one of the megacities most affected by haze in China, from January 22 to March 3, 2021. During the observation period, the average mass concentration of PM2.5 was 62.3 ± 37.2 μg m-3, and the emissions from mobile sources were more prominent. Carbonaceous particles accounted for 68.6% of the total particles and could be classified into 10 categories, with elemental carbon (EC) mixed with sulfate (EC-S) particles making the highest contribution (33.1%). EC particles rich in secondary components and organic carbon (OC) particles rich in secondary component exhibited different diurnal variations, suggesting different sources and mixing mechanisms. From "excellent" to "polluted" days, the contributions of EC-S, EC mixed with sulfate and nitrate (EC-SN) and OC mixed with EC (OC-EC) particles increased by 9.8%, 4.5% and 6.6%, respectively, and thus these particles are key targets for future pollution control. The potential source contribution of the southwest area was stronger than that of other areas, and the potential contribution of regional transport to EC-related particles was stronger than to OC-related particles. Most particles were highly mixed with sulfate or nitrate, and the level of secondary mixing further enhanced as pollution worsened.

Analysis of PM2.5 Synergistic Governance Path from a Socio-Economic Perspective: A Case Study of Guangdong Province

Analyzing the influencing factors of PM2.5 concentration, scenario simulations, and countermeasure research to address the problem of PM2.5 pollution in Guangdong Province is of great significance for governments at all levels for formulating relevant policies. In this study, the ChinaHighPM2.5 dataset and economic and social statistics for Guangdong Province from 2010 to 2019 were selected, and a PM2.5 pollution management compliance path formulation method based on the multi-scenario simulation was proposed by combining the differences in city types and PM2.5 concentration prediction. Based on the prediction model of PM2.5 concentration constructed by the Ridge and SVM models and facing the PM2.5 pollution control target in 2025, the urban PM2.5 pollution control scenario considering the characteristics of urban development was constructed. According to the scenario simulation results of the PM2.5 prediction model, the PM2.5 pollution control path suitable for Guangdong Province during the 14th Five-Year Plan period was explored. The coupling coordination model was used to explore the spatial and temporal pattern evolution of PM2.5 pollution collaborative governance in various prefecture-level cities under the standard path, and the policy recommendations for PM2.5 pollution control during the 14th Five-Year Plan period are proposed. The results showed the following: ① in the case of small samples, the model can provide effective simulation predictions for the study of urban pollutant management compliance pathways. ② Under the scenario of PM2.5 management meeting the standard, in 2025, the annual average mass concentration of PM2.5 in all prefecture-level cities in Guangdong Province will be lower than 22 μg/m3, and the annual average concentration of PM2.5 in the whole province will drop from 25.91 μg/m3 to 21.04 μg/m3, which will fulfil the goal of reducing the annual average concentration of PM2.5 in the whole province to below 22 μg/m3, as set out in the 14th Five-Year Plan for the Ecological Environmental Protection of Guangdong Province. ③ Under the path of PM2.5 control and attainment, the regional coordination relationship among prefecture-level cities in Guangdong Province is gradually optimized, the number of intermediate-level coordinated cities will increase, and the overall spatial distribution pattern will be low in the middle and high in the surrounding area. Based on the characteristics of the four city types, it is recommended that a staggered development strategy be implemented to achieve synergy between economic development and environmental quality. Urban type I should focus on restructuring freight transportation to reduce urban pollutant emissions. City type II should focus on urban transportation and greening. For city type III, the focus should be on optimizing the industrial structure, adjusting the freight structure, and increasing the greening rate of the city. For city type IV, industrial upgrading, energy efficiency, freight structure, and management of industrial pollutant emissions should be strengthened.

Impact of Air Pollution on Respiratory Diseases in Typical Industrial City in the North China Plain

Air pollution can lead to the elevated incidence of various respiratory diseases, seriously endangering the health of urban residents. To better comprehend the association between urban air pollution and respiratory disease incidence, this study focused on Xinxiang City, a typical industrial city in the North China Plain, as the research object. By analyzing monthly air pollution index concentrations from 2018 to 2021 and confirmed cases of respiratory diseases, and incorporating meteorological factors as reference points, we conducted a correlation analysis between disease data and pollutant concentrations. We then constructed a Poisson regression model to obtain maximum likelihood estimates, which were used to predict the quantitative relationship between the incidence of respiratory diseases and air pollution indicators. The results showed that an increase of 1 μg/m³ in the average mass concentration of PM2.5, PM10, NO2, and SO2 in ambient air was associated with an elevated incidence of respiratory diseases by 0.2–1.4%, 0.7–1.6%, 3.7–8.2%, and 0.5–2.3%, respectively; meanwhile, a monthly mean mass concentration of CO increased by 1 mg/m³ led to a rise in pulmonary tuberculosis incidence by 2.9%. Additionally, based on health risk data following exposure to air pollution in Xinxiang City, it was confirmed that the impact of respiratory diseases as measured by the air quality composite index was more applicable than the single pollution index. Furthermore, there was a significant association between air pollution and the incidence of respiratory diseases.

Source apportionment of PM2.5 in Thailand's deep south by principal component analysis and impact of transboundary haze.

Atmospheric particulate matter smaller than 2.5 micron (PM2.5) was evaluated at four sites in the lower southern part of Thailand during 2019-2020 to understand the impact of PM2.5 transport from peatland fires in Indonesia on air quality during the southwest monsoon season. Mass concentration and chemical bound-PM, including carbon composition, e.g., organic carbon (OC) and elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), and inorganic elements, were analyzed. The PM2.5 emission sources were identified by principal components analysis (PCA). The average mass concentrations of PM2.5 in the normal period, which represents clean background air, from four sites was 3.5-5.1µg/m3, whereas during the haze period, it rose to 5.4-13.5µg/m3. During the haze period, both OC and EC were 3.5 times as high as in the normal period. The average total PAHs and BaP-TEQ of PM2.5 during the haze period were ~ 1.3-1.7 and ~ 1.2-1.9 times higher than those in the normal period. The K concentrations significantly increased during haze periods. SO42- dominated throughout the year. The effects of external sources, especially the transboundary haze from peatland fires, were significantly enhanced, because the background air in the study locations was generally clean. PCA indicated that vehicle emission, local biomass burning, and secondary particles played a key role during normal period, whereas open biomass burning dominated during the haze phenomena. This was consistent with the OC/EC and PAH diagnostic ratios. Backward trajectories confirmed that the sources of PM during the haze period were predominantly peatland fires in Sumatra, Indonesia, due to southwest wind.

Assessment and sources identification of air quality pollution in Klang Valley, Kuala Lumpur, Malaysia

Air quality pollution increases a research interest due to its importance ininfluencing weather and temperature, restricting visibility and causing harmful effects on human health. Samples of airborne particulate matter (APM) were collected weekly during the period from 2018 to 2020 at Klang Valley, Kuala Lumpur. The samples were collected using a Gent stacked filter sampler in two fractions particulate matter PM2.5 (PM2.5 – size of particulate < 2.5 μm) and particulate matter PM10 (PM10 – size of particulate 2.5 – 10 μm). 100 pairs of APM samples were analysed by Energy Dispersive X-Ray Fluorescence (EDXRF) for their elemental composition. The analysis result of air quality in Klang Valley, Kuala Lumpur, for an average mass concentration of PM2.5 (26.8 μg/m3) and PM10 (44.8 μg/m3) were higher compared to the interim value of Malaysian ambient air quality standard 2020 (MAAQS-2020) (PM2.5 = 15.0 μg/m3; PM10 = 40.0μg/m3). The results showed the possible sources of air pollution in the Klang Valley contributed by biomass burning/smoke (31.6%), soil dust (10.3%), industries (8.4%), motor vehicles (7.1%), sea spray (6.3%) and secondary sulphate (5.5%).

Quantifying the pollution characteristics of chemical components in PM2.5 in the North China Plain, China: Spatiotemporal variation and health risk

To fully grasp the features of aerosol chemical composition in North China Plain (NCP) region from winter through spring, this study chose five typical cities (Jinan, Shijiazhuang, Taiyuan, Tianjin and Zhengzhou) and analyzed their spatiotemporal variation, sources and health risk from January to March 2018. The average mass concentration of PM2.5 ranged from 65.65 μg/m3 (Tianjin)–101.23 μg/m3 (Shijiazhuang). It was high in the southwest and low in the northeast because of better diffusion conditions in coastal areas than inland. In PM2.5, organic carbon (OC) accounted for 8.28% (Jinan)–35.36% (Shijiazhuang), elemental carbon (EC) accounted for 3.75% (Tianjin)–13.31% (Shijiazhuang), water-soluble ions (WSIs) accounted for 34.8% (Shijiazhuang)–57.16% (Tianjin), and elements accounted for 3.01% (Zhengzhou)–4.74% (Taiyuan). In carbonaceous aerosols, primary OC (POC) was dominant in coastal areas while secondary OC (SOC) was dominant inland. The source of OC and EC emissions in northern and central cities was coal combustion, whereas in southern cities, both vehicles and coal combustion were involved. Although NO3−, SO42− and NH4+ accounted for 70.09% (Taiyuan)–73.02% (Jinan) of WSIs over the whole region, SO42− dominated in the west and center region, and NO3− dominated in the east and south. K, Fe, and Ca had the highest concentrations in elements, accounting for 76.77% (Tianjin)–79.80% (Taiyuan). Potential ecological risk index (RI) for 7 toxic heavy metal elements—Cd, Cr, Cu, Ni, Pb, V and Zn—more than 600 (Pb contributed 51.37%) in Taiyuan and more than 1200 (Cd contributed 87.54%–97.71%) in other cities showed severe metal pollution. Kids and adults living here faced non-carcinogenic risk by exposure pathways of dermal contact and respiratory inhalation, respectively. At the same time, kids also faced non-carcinogenic risk.

Pollution Characteristics and Factors Influencing the Reduction in Ambient PM2.5 in Beijing from 2018 to 2020

Air quality data from 33 environment sites and five regional sites from 2018 to 2020, as well as meteorological data, were used to research PM2.5 variation,spatial and temporal change, diurnal variation, and heavy pollutions in Beijing. The annual average mass concentrations of PM2.5 in Beijing were 51, 42, and 38 μg·m-3, which showed great progress in air quality improvement. However, the PM2.5 concentration in 2020 was still 8.6% above the national limit value despite a 30.9% decline since 2017. The PM2.5 south-north gradient in Beijing remained throughout the three years, but this pattern showed a less significant trend. The highest monthly mean PM2.5 concentrations in Beijing tended to occur in January-March, with the lowest in August-September. NOx, CO, and PM2.5 concentrations were significantly higher in the heating season than in the non-heating season by 58.4%, 52.9%, and 27.5%, respectively. Diurnal variation showed that greater PM2.5 concentrations were observed at nighttime during the heating season and, conversely, at noontime during the non-heating season. Sixteen pollution episodes occurred in Beijing over the last three years, resulting in 25 heavy pollution days distributed in autumn-winter of 2018-2020. The regional heavy pollution characteristics of PM2.5 in Beijing were significant. Through analysis, a continuous pollution reduction was still the most important reason for the yearly decrease in PM2.5. The concentrations of organic matter, elemental carbon, and crustal matter in the PM2.5 in Beijing decreased by 43.3%, 53.2%, and 51.5% since 2017, respectively, and nitrate, sulfate, and ammonium decreased by 34.2%, 52.2%, and 43.7%.The results showed that the control effect of PM2.5 in Beijing was obvious.

Potential Source Area and Transport Route of Atmospheric Particulates in Xi’an, China

Atmospheric particulate pollution is one of the most common pollution related issues and poses a serious threat to human health. PM2.5 and PM10 are important indicators of atmospheric particulate pollution currently. Based on the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the hourly 72 h backward trajectory of particulate matter in Xi’an from March 2019 to February 2022 was calculated, and the main path of air flow to Xi’an was studied by cluster analysis. Combined with hourly concentration monitoring data of PM2.5 and PM10 at each station, the potential source area of particles in Xi’an was calculated by potential source contribution factor analysis and concentration weighted trajectory analysis. The results show that Xi’an was most polluted in winter, followed by autumn and spring, and cleanest in the summer. The annual average mass concentrations of PM2.5 and PM10 are 48.5 ± 28.7 μg/m3 and 89.2 ± 39.2 μg/m3, respectively, both exceeding the national secondary standard for ambient air quality. On an annual basis, back-trajectory analysis showed that predominantly transport was rapid from the northwest (44%). Transport from the other sectors were 24%, 19%, and 14% from the northeast, southeast, and southwest, respectively, and featured lower windspeeds on average. The potential source areas of particulate matter in Xi’an in the spring are mainly located at the junction of Chongqing, Hunan, and Hubei, and parts of the southeast and north of Sichuan. This study provides context for air quality and atmospheric transport conditions in this region of China.

Online chemical characterization of atmospheric fine secondary aerosols and organic nitrates in summer Nanjing, China

The mechanisms leading to secondary aerosol pollution in the Yangtze Delta region (such as Nanjing) are still poorly constrained. Here we conducted a field campaign to elucidate the chemical characteristics of fine aerosols, with a focus on variations and formation mechanisms of secondary components in summer Nanjing. The average PM1 mass concentration was 18.88 μg m−3 and was dominated by the secondary species (78%). Secondary inorganic species accounted for 30% of PM1 mass and high PM1 loading was closely relevant with nitrate rather than sulfate. Nitrate was mainly produced from nighttime heterogeneous/aqueous process (production rate of 0.38 g/g H2O) and its variation was driven by thermodynamic equilibrium. On the other hand, sulfate was governed by daytime photochemical production (production rate of 0.013 g/g Ox)(Ox=NO2 + O3) while contribution of aqueous process was minor. Positive matrix factorization identified and quantified a traffic-related hydrocarbon OA (HOA), a cooking OA (COA), and four SOA factors including a local secondary OA (LSOA), a less oxygenated OA (LO-OOA), a moderately oxygenated OA (MD-OOA), and a more-oxidized oxygenated OA (MO-OOA). LSOA was likely from local photochemical conversion of HOA and COA; LO-OOA was semi-volatile thus evaporation/diffusion would offset its weak photochemical production. MO-OOA was very clearly linked with photochemistry, based on its afternoon enhancement and tight positive correlations with Ox (0.029 g/g Ox, occupying ∼60% of photochemical SOA production) and sulfate. MD-OOA was a minor contributor of SOA (∼6%) but it was clearly from aqueous process given the strong positive correlation with aerosol liquid water content (ALWC) and nitrate. Both nitrate and MD-OOA concentrations increased against pH while those of sulfate and MO-OOA decreased. We further investigated the organic nitrate (ON) characteristics, and found that ON was a very minor component of OA in summer Nanjing (0.08–0.14 μg m−3, 0.6–1.1% of OA) and it was predominantly associated with aqueous process. Overall, this work reveals in details formation processes of different secondary species, and therefore is insightful for future air pollution modelling and efficient control in similar regions.

Chemical-composition characteristics of PM1 and PM2.5 and effects on pH and light-extinction coefficients under different pollution levels in Zhengzhou, China

Atmospheric particulate matter (PM) is a significant pollutant in the atmosphere. An increase in PM2.5 concentration notably diminishes atmospheric visibility and leads to haze formation. PM1, a type of atmospheric PM with smaller particle size, has a more pronounced effect on visibility and aerosol pH compared to PM2.5. In this study, PM1 and PM2.5 samples were collected in August, November, and December of 2020, as well as in April of 2021 in Zhengzhou. The chemical composition, aerosol pH, and light-extinction coefficients (bext) of PM1 and PM2.5 were analyzed based on the aerosol concentrations in three pollution categories. Throughout the sampling period, the average mass concentrations of PM1 and PM2.5 were 56.2 and 71.9 μg m−3, respectively, with nitrate constituting 24.3% of PM2.5. This highlights the severe submicron-level particulate pollution in Zhengzhou. Differences in the composition of PM1 and PM2.5 led to variations in aerosol water content, but the combined effect on aerosol pH was minimal. PM1 displayed a stronger negative correlation with visibility because SNA (NO3−, SO42−, and NH4+) was primarily concentrated in PM1. The bext of nitrate consistently increased during the pollution period, reaching 58% during the moderate pollution phase. This result suggests that the extinction contribution of nitrate was the main factor contributing to the decreased visibility in Zhengzhou. Reducing nitrogen oxide emissions can lower PM2.5 concentrations and enhance visibility. Additionally, controlling nitrate production can achieve a secondary reduction in aerosol concentration by decreasing the aerosol water content, which in turn reduces the secondary formation of PM. This study is beneficial for formulating measures to reduce the concentration of PM2.5 and reducing pollution.

Impact of aging on the sources, volatility, and viscosity of organic aerosols in Chinese outflows

Abstract. To investigate the impact of aging on the sources, volatility, and viscosity of organic aerosol (OA) in Chinese outflows, a high-resolution time-of-flight aerosol mass spectrometer (HR-AMS) coupled with a thermodenuder (TD) was deployed in the spring of 2018 in Dongying, which is a regional receptor site of metropolitan emissions in the North China Plain (NCP). The average mass concentration of PM1 is 31.5±22.7 µg m−3, which is mainly composed of nitrate (33 %) and OA (25 %). The source apportionment results show that the OA is mainly contributed by oxygenated OA (OOA) from secondary sources, including background-OOA (33 %) representing a background concentration of OA (2.6 µg m−3) in the NCP area, and transported-OOA (33 %) oxidized from urban emissions. The other two factors include aged hydrocarbon-liked OA (aged-HOA, 28 %) from transported vehicle emissions and biomass burning OA (BBOA, 5 %) from local open burning. The volatility of total OA (average C*=3.2×10-4 µg m−3) in this study is generally lower than that reported in previous field studies, which is mainly due to the high OA oxidation level resulting from aging processes during transport. The volatilities of OA factors follow the order of background-OOA (average C*=2.7×10-5 µg m−3) &lt; transported-OOA (3.7×10-4µgm-3)&lt; aged-HOA (8.1×10-4µgm-3)&lt; BBOA (0.012 µg m−3). Extremely low volatilities in ambient air indicate that oligomers may exist in aged plumes. The viscosity estimation suggests that the majority of ambient OA in this study behaves as semisolid (60 %), liquifies at higher relative humidity (RH) (21 %), and solidifies (19 %) during noon when the RH is low and the oxidation level is high. Finally, the estimated mixing time of molecules in 200 nm OA varies dramatically from minutes at night to years in the afternoon, emphasizing the need to consider its dynamic kinetic limits when modeling OA. In general, the overall results of this study improve our understanding of the impact of aging on OA volatility and viscosity.

Spatiotemporal, Morphological and Source Analysis of Ultrafine Particulates (PM1) over Bengaluru, Karnataka, India

Measurement and analysis of Particulate Matter of aerodynamic diameter less than 1µm (PM1) has been carried out using indigenously built air sampler at the following locations of Bengaluru city: Basavanagudi (BAS), Domlur (DOM), Hosur road (HOS) and DC Halli (DCH). The PM1mass concentrations were observed to vary from 20.16 µg/m3 to 68.64 µg/m3 during the study period. The highest mass concentration of 68.64 µg/m3 was observed for the location BAS and the lowest mass concentration of 20.16 µg/m3 was observed for the location DOM. The average mass concentration of PM1 around Bengaluru for winter, summer, monsoon &amp; post monsoon season is observed to be 47.60 µg/m3, 40.24 µg/m3, 30.85 µg/m3 and 38.76 µg/m3 respectively. Some of the collected samples showed the presence of microorganism such as bacillus. Elemental composition analysis showed the presence of non-metals Carbon, Oxygen, Nitrogen, Sulphur and traces of metals such as Sodium, Aluminium, Calcium and Potassium.&#x0D;

Characteristics of Water-Soluble Inorganic Ions in PM2.5 in Typical Urban Areas of Beijing, China.

Following the implementation of “coal-to-gas conversion” policy in the Haidian District of Beijing during summer, the present comparative study was performed employing 41 PM2.5 samples as precursors to analyze the characteristics of water-soluble inorganic ions. The concentrations of water-soluble inorganic ions in PM2.5 were analyzed by ion chromatography, and the occurrence form of ions was characterized via time-of-flight secondary ion mass spectrometry (TOF-SIMS). Results revealed that the daily average mass concentration of PM2.5 in Beijing during the sampling period was 94.28 ± 52.49 μg/m3. As compared to the winter of 2016, the average daily PM2.5 concentration in Beijing decreased by 29 μg/m3 in 2017 (28.2% decrease), with a remarkable decline in the number of days with pollution. During the pollution period, the concentrations of NO3–, SO42–, and NH4+ were significantly higher in PM2.5 as compared to the cleaning period. The ratio of the concentrations of [NO3–]/[SO42–] was greater than 1, and the contribution from mobile sources was relatively large, indicating that the implementation of the “coal-to-gas conversion” policy in Beijing has led to the reduction of SO42– emissions from fixed sources, such as coal. Furthermore, TOF-SIMS analysis results showed that NH4+ tended to exist in the form of molecular ammonium sulfate or ammonium hydrogen sulfate during the period of pollution.

Variations of PM2.5 sources in the context of meteorology and seasonality at an urban street canyon in Southwest Germany

In order to assess the factors controlling urban air pollution, we characterized fine particulate matter (PM2.5) at an urban street canyon in southwest Germany, in summer 2019 and winter 2020. The average mass concentration of PM2.5 was higher in dry and hot summer (7.0 ± 3.5 μg m−3) than in cold and humid winter (5.8 ± 2.8 μg m−3) with frequent wet scavenging. The non-refractory PM2.5 (NR-PM2.5) measured with an aerosol mass spectrometer (AMS) plus black carbon (BC) mostly consists of organic aerosol (OA) with 60% in summer and 44% in winter. The contributions of sulfate to NR-PM2.5 plus BC was higher in summer (18%) than in winter (13%), while that of nitrate was lower in summer (6%) than in winter (22%). During the entire measurement periods in both seasons, relatively flat diurnal variations of sulfate were found, suggesting that it was associated with regional transport. However, occasionally rapid increase of sulfate can be caused by the transport of upwind industrial sources and enhanced vertical mixing processes. Nitrate showed a peak at morning rush hours related to traffic emissions, and then subsequently decreased by evaporation processes during daytime with higher temperature. Positive matrix factorization analysis revealed that the total OA was dominated by secondary organic aerosol (SOA) over the primary traffic emissions with ∼82% in summer and ∼48% in winter. A detailed analysis of two pollution episodes clearly demonstrated the impact of meteorological conditions on secondary aerosol formation and accumulation. A summertime heatwave episode showed high contributions of SOA to PM2.5 mass, which formed locally through daytime photochemical oxidation as well as nighttime chemistry of biogenic precursors. A wintertime transitional episode occurred with significant shift from relatively warm and humid to cold and dry conditions. The fast formation of sulfate, nitrate, ammonium and SOA were found under the warm and humid period after receiving a local industrial emission plume. The cold and dry period was influenced by various sources including long-range transport of Saharan dust and anthropogenic emissions in central Europe. This study highlights the variations of urban PM2.5 sources under certain meteorological conditions such as summer heatwave and humid winter, which are expected high occurrence in future. Our results provide the implication on actual needs of mitigation actions to these pollution episodes in less-polluted western Europe cities.

Chemical characteristics and regional transport of submicron particulate matter at a suburban site near Lanzhou, China

Lanzhou, which is a valley city on the Loess Plateau, frequently suffered from aerosol pollution in recent years, especially in winter. However, the lack of understanding of factors governing aerosol pollution limits the implementation of effective emission policies in and around Lanzhou. To help solve this problem, an intensive field campaign was conducted at the SACOL site, which is a suburban site near Lanzhou, in winter 2018. The chemical characteristics and sources of submicron particulate matter (PM1) were investigated, and the influence of the topography around Lanzhou on aerosol pollution was examined. In the present study, the average PM1 mass concentration reached 25.6 ± 12.8 μg m−3, with 41.0% organics, 16.1% sulfate, 19.7% nitrate, 10.7% ammonium, 3.1% chloride, and 9.4% black carbon (BC). Three organic aerosol (OA) factors were identified with the positive matrix factorization (PMF) algorithm, including a biomass burning OA (BBOA, 13.6%), a coal combustion OA (CCOA, 34.2%), and an oxygenated OA (OOA, 52.2%). The significant relationships between organics, BC, and chloride and wind pattern suggested that the SACOL site was strongly influenced by regionally transported aerosols. Further analysis suggested that these aerosol regional transport events were caused by topography. Due to the limitation of the valley, aerosols accumulated in the valley. These accumulated aerosols were then transported to the SACOL site along the valley by prevailing winds. Our study highlights enhanced aerosol regional transport in valleys, which provides a new perspective for future studies on aerosol pollution in basins and valleys.