PM10 Aerosol Research Articles

Contribution to the study of possible transport of PM10 aerosols in the eastern part of the Czech Republic

The article deals with the assessment of air pollution in the eastern regions of the Czech Republic: Moravia and Silesia, where the limits for the protection of human health for PM and benzo[a]pyrene are significantly exceeded, especially in the north-eastern area. The extent to which this heavily polluted part of Moravia and Silesia affects the central, southern and south-eastern parts of Moravia, i.e. south-eastern part of the Czech Republic, has often been discussed but not proven. The assessment demonstrated the influence and extent of pollutant transport by determining the prevailing daily wind direction. The prevailing NE wind direction results in worse dispersion conditions and higher PM10 concentrations throughout the study area. Conversely, the SW wind direction is a carrier of better dispersion conditions with lower PM10 concentrations in the area. The effect of transport of PM10 pollution in the daily type from the NE direction can be observed at those sites located in the NE of the area of interest from the border with Poland to the Prerov site. In the case of more southerly sites, the methodology used does not allow to determine whether and to what extent they are affected by pollution transport from the northeastern part of Moravia or from neighbouring Poland. This methodology is particularly useful when only 24-h pollutant concentrations are available (not at more detailed, e.g. 1-hour intervals). The internal methodology of the Czech Hydrometeorological Institutefor calculating back trajectories of wind from ground stations is particularly applicable for detecting the origin of short-term episodes with high pollutant concentrations.

Stable isotope compositions, source apportionment and transformation processes of carbonaceous aerosols in PM10 in the urban city of Hyderabad, India

This study apportions sources of carbonaceous aerosols using isotopic characteristics of total carbon (TC) and elemental carbon (EC) in PM10 aerosols using filter-based CTO-375 method for pre-monsoon (summer), post-monsoon, and winter (2019–2021) over Hyderabad, India. Highest secondary organic carbon, SOC (primary organic carbon, POC) of 13.78 ± 10.25 (7.87 ± 2.48) μg/m3 was during post-monsoon 2020 (2019), while lowest was 8.90 ± 5.55 (4.18 ± 0.92) μg/m3 during pre-monsoon 2021 (post-monsoon 2020), respectively. Average effective carbon ratio (ECR) > 1 indicates dominance of light scattering aerosols during pre-monsoon and post-monsoon. δ13CTC and δ13CEC varied from – 28.1 to – 24.7 ‰ (avg. – 26.5 ± 0.7) and - 32.5 to – 24.6 ‰ (avg. – 27.4 ± 1.1), indicating contribution from C3 plant burning and liquid fuel combustion. Positive value of δ13COC – δ13CEC and heavier δ13CTC, along with gradual enrichment in δ13CTC and δ13CEC from December 2020 to March 2021, suggested photochemical aging of carbonaceous aerosols. Lighter δ13CTC and OC/EC > 4 for all seasons indicates dominance of biomass burning (wood and crop residue burning), photochemical oxidation and secondary organic aerosol (SOA) formation. The tropical study experiences dominance of lighter δ13CEC compared to subtropical, high latitude regions.

The seasonal variation of Asian dust, anthropogenic PM, and their sources in Dushanbe, Tajikistan

Central Asia's arid climate and growing population make it susceptible to air pollution from mineral dust and anthropogenic sources. To assess the impact of these pollution sources on local air quality, the chemical composition of PM10 aerosol particles was collected within a year at Dushanbe, Tajikistan. Primary sources of the pollutants, their impact on PM10 composition, and their seasonal trends were assessed. The measurement approach employed analysis of trace metals, ions, organic compounds, laboratory investigations, diagnostic ratio calculations, all complemented by positive matrix factor analysis. The results reveal that for about 70% of the year, PM10 levels (80 ± 55 μg m−3 as the annual average) in Dushanbe were higher than the WHO limits, with varying levels during the seasons. Summer concentrations peaked up to 434 μg m−3 due to a combined mineral and road dust influence. Interestingly, winter concentrations reached 152 μg m−3 due to strong contributions (about 64%) from residential heating and fossil fuel combustion, often triggered during sub-10 °C temperatures. Mineral dust events were associated with elevated concentrations of trace metals, including Zn and Pb, alongside organic carbon and high-chain n - alkanes. During such events, Ca/Fe, Ca/Al ratios exceeded those of Saharan dust, suggesting a high salt content in Asian dust, potentially influenced by dried-off lake emissions. It was striking to observe that winter periods exhibited concerning levels of carcinogenic PAHs, such as benzo(b)fluoranthene (<25 ng m−3) and benzo[a]pyrene (<12 ng m−3, BaP), with average values of 4.1 ± 5.9 ng m−3 (BaP) that significantly exceed WHO recommendations. The high PM10 and PAH exposure could pose severe health risks, necessitating collective attention from the local authorities in developing new mitigation strategies concerning the reduction of emissions from residential heating of coal and wood in winter to curb combustion emissions and reduce exposure.

Characteristics and Sources of Organic Aerosol in PM2.5 at Yangbajing in Tibetan Plateau

The climate and environment of the Tibetan Plateau (TP) are sensitive to human activities. As a key component highly influencing global climate and environment, organic aerosol over the TP is investigated in this study, especially in organic composition and its sources. This study aims to explore the composition characteristics, seasonal variation, and potential sources of organic aerosol including two episodes through one-year sampling at the Yangbajing (YBJ) site in the TP. A total of 120 primary and secondary organic species as well as organic carbon (OC) and elemental carbon (EC) were measured in PM2.5. The annual average concentrations of OC, EC, and organic species were 3.12 ± 3.73 μgC/m3, 0.28 ± 0.18 μgC/m3 and 104 ± 36.6 ng/m3, respectively. High ratio of OC to EC (OC/EC) and low ratio of fatty acids to n-alkanes were found for aerosol in the TP. The OC/EC ratio was 11.8 ± 10.2 on average at the YBJ site and strongly correlated with levoglucosan, a tracer for biomass burning, but not so with typical secondary species, indicating that the high ratio of OC/EC over the TP was more influenced by biomass burning than secondary formation. The ratio of fatty acids to n-alkanes at YBJ was 1.39 ± 0.29 on average, lower than those reported over urban areas (3.13 ± 1.49), probably owing to less residential cooking activities. Seasonally, the non-monsoon season had significant increases in primary organic aerosol (POA) tracers, among which biomass burning tracers had a higher increase percentage than other specific tracers. On the contrary, the levels of secondary organic aerosol (SOA) tracers, especially isoprene- and monoterpene-derived SOA tracers were enhanced in the monsoon season (summer time), largely resulting from high emissions of biogenic volatile organic compounds. Two episodes characterized with much higher concentrations of organic species (1215 and 688 ng/m3) were observed in this study. One was characterized by significant enhancement of POA tracers with the air masses originated from South Asia, and the other showed large increases in SOA and POA tracers with the air masses transported across multiple regions. This study could help to better understand the influence of human activities on atmospheric organic aerosol in remote regions and how POA and SOA vary with seasons and in different episodes.

Long-term evolution of carbonaceous aerosols in PM2.5 during over a decade of atmospheric pollution outbreaks and control in polluted central China

Against the backdrop of an uncertain evolution of carbonaceous aerosols in polluted areas over the long term amid air pollution control measures, this 11-year study (2011–2021) investigated fine particulate matter (PM2.5) and carbonaceous components in polluted central China. Organic carbon (OC) and elemental carbon (EC) averaged 16.5 and 3.4 μg/m3, constituting 16 and 3 % of PM2.5 mass. Carbonaceous aerosols dominated PM2.5 (35 and 27 %) during periods of excellent and good air quality, while polluted days witnessed other components as dominants, with a significant decrease in primary organic aerosols and increased secondary pollution. From 2011 to 2021, OC and EC decreased by 53 and 76 %, displaying a high-value oscillation phase (2011–2015) and a low-value fluctuation phase (post-2016). A substantial reduction in high OC and EC concentrations in 2016 marked a milestone in significant air quality improvement attributed to effective control measures, especially targeting OC and EC, evident from their decreased proportion in PM2.5. Primary OC (POC) in winter exhibited the most pronounced reduction (8 % per year), and the seasonal disparities in PM2.5 and carbonaceous components were reduced, showcasing the effectiveness of control measures. Contrary to the more pronounced reduction of EC, which decreased in proportion to PM2.5, secondary OC (SOC) in PM2.5 exhibited an increasing trend. Along with rising OC/EC, SOC/OC, and SOC/EC ratios, this indicates a growing prominence of secondary pollution compared to the decrease in primary pollution. SOC shows an increasing trend with NO2 rise (r = 0.53), without O3 promoting SOC. Positive correlations of SOC with SO2, CO (r = 0.41, 0.59), also highlight their influence on atmospheric conditions, oxidative capacity, and chemical reactions, indirectly impacting SOC formation. The implementation of precise precursor emission reduction measures holds the key to future efforts in mitigating SOC pollution and reducing PM2.5 concentrations, thereby contributing to improved air quality.

Refined Sea Salt Markers for Coastal Cities Facilitating Quantification of Aerosol Aging and PM2.5 Apportionment.

Sea salt (ss) aerosols in PM2.5 are often quantified through source apportionment by applying sodium (Na+) and chloride (Cl-) as the markers, but both markers can be substantially emitted from anthropogenic sources. In this study, we differentiate ss from nonss (nss) portions of Na+ and Cl- to better apportion PM2.5 in a coastal tropical urban environment. Size-resolved ionic profiles accounting for Cl- depletion of aged ss were applied to 162-day measurements during 2012 and 2018-2019. Results show that the nss (likely anthropogenic) portions, on average, account for 50-80% of total Na+ and Cl- in submicron aerosols (PM1). This corresponds to up to 2.5 μg/m3 of ss in submicron aerosols that can be ∼10 times overestimated if one attributes all Na+ and Cl- in PM1 to ss. Employing the newly speciated ss- and nss-portions of Na+ and Cl- to source apportionment of urban PM2.5 via positive matrix factorization uncovers a new source of transported anthropogenic emissions during the southwest monsoon, contributing to 12-15% of PM2.5. This increases anthropogenic PM2.5 by ≥19% and reduces ss-related PM2.5 by >30%. In addition to demonstrating Cl- depletion (aging) in submicron aerosols and quantifying ssNa+, nssNa+, ssCl-, as well as nssCl- therein, the refined PM2.5 apportionment resolves new insights on PM2.5 of anthropogenic origins in urban environments, useful to facilitate policy making.

Urban heat and pollution island in the Moscow megacity: Urban environmental compartments and their interactions

Cities are highly interconnected systems where specific interactions between various urban environments occur due to the Urban Heat Island (UHI) and Urban Pollution Island (UPI) effects. Four compartments of the environment (atmospheric air, road dust, streamflow, and people) are discussed for Moscow city. Long-term meteorological, radiative, air quality, and precipitation measurements, the non-hydrostatic regional numerical COSMO model, and extensive hydrological and geochemical sampling were used. To characterize mortality and UPI interaction, a family of distributed lag non-linear models (DLNM) was applied. The study reveals increased aerosols concentrations which reduce the incoming solar radiation and increase the atmospheric longwave radiation. UHI strengthens the low-troposphere convergence due to urban breeze circulation and atmospheric circulation due to elevated surface roughness, the effect which leads to 11.6% heaviest precipitation increase compared to background values. Increased precipitation doubles streamflow rates and enhances the contribution of rain floods to annual flow. Similar geochemical associations with Sb, W, Zn, Cd, Pb, and Cu were found in aerosol PM10, indicating transport and road dust impact. Finally, associations between high temperatures and human mortality which are generally stronger at high levels of air pollution for both PM10 and NO2, and for lag 1 day and 2–6 days are discussed.

Short-Term Effects of Primary and Secondary Particulate Matter on Ceramide Metabolism, Pro-Inflammatory Response, and Blood Coagulation.

Evidence of the precise biological pathway responsible for acute cardiovascular events triggered by particulate matter (PM) exposure from anthropogenic emissions is sparse. We investigated the associations of biomarkers relevant to the pathophysiology of atherothrombosis (ceramide metabolism, pro-inflammatory response, and blood coagulation) with primary and secondary components in particulate matter with aerodynamic diameters less than 2.5 μm (PM2.5). A total of 152 healthy participants were followed with four repeated clinical visits between September 2019 and January 2020 in Beijing. Exposure to ambient inorganic aerosols (sulfate, nitrate, ammonium, and chloride), as well as organic aerosols (OA) in PM2.5, was measured by a real-time aerosol chemical speciation monitor, and sources of OA were performed by positive matrix factorization. We found significant increases of 101.9-397.9% in ceramide indicators associated with interquartile-range increases in inorganic aerosols and OA prior to 72 h of exposure. Higher levels of organic and inorganic aerosols in PM2.5 were associated with increases of 3.1-6.0% in normal T cells regulated upon activation and expressed and secreted relevant to the pro-inflammatory response; increases of 276.9-541.5% were observed in D-dimers relevant to coagulation. Detrimental effects were further observed following OA exposure from fossil fuel combustion. Mediation analyses indicated that ceramide metabolism could mediate the associations of PM2.5 components with pro-inflammatory responses. Our findings expand upon the current understanding of potential pathophysiological pathways of cardiovascular events posed by ambient particulates and highlight the importance of reducing primary and secondary PM from anthropogenic combustions.

Characteristics and Source Analysis of Carbonaceous Aerosols in PM2.5 in Huaxi District, Guiyang

Carbonaceous aerosol, as an important component of atmospheric aerosol, has a significant impact on atmospheric environmental quality, human health, and global climate change. To investigate the characteristics and sources of carbonaceous aerosol in atmospheric fine particulate matter (PM2.5) in Huaxi District of Guiyang, an in-situ observational study was conducted during different seasons in 2020, and the carbonaceous components of PM2.5 were measured using a thermal-optical carbon analyzer (DRI Model 2015). The results of the study showed that the average concentrations of PM2.5, total carbonaceous aerosol (TCA), organic carbon (OC), secondary organic carbon (SOC), and elemental carbon (EC) concentrations during the observation period were (39.7±22.3), (14.1±7.2), (7.6±3.9), (4.4±2.6), and (2.0±1.0) μg·m-3, respectively, and the mean value of OC/EC was (3.9±0.8). ρ(PM2.5), ρ(TCA), ρ(OC), ρ(SOC), and ρ(EC) showed a seasonal variation pattern with the highest in winter [(52.6±28.6), (17.0±9.6), (9.1±5.2), (6.1±3.9), and (2.4±1.2) μg·m-3, respectively] and the lowest in summer [(25.1±7.1), (11.6±3.6), (6.3±1.9), (3.7±1.2), and (1.6±0.6) μg·m-3, respectively]. The seasonal variation in OC/EC showed summer (4.2±0.8) > winter (3.8±0.9) > autumn (3.8±0.5) > spring (3.7±0.9), indicating the presence of SOC generation in all seasons in Huaxi District. SOC showed a significant correlation with OC (R2 =0.9), and the SOC concentration tended to increase with the increase in atmospheric oxidation. OC showed a good correlation with EC in all seasons, with the highest in autumn (R2 =0.9) and lower correlations in the other three seasons (R2 ranged from 0.74 to 0.75), indicating a common source. According to OC/EC ratio range, it was preliminarily determined that carbonaceous aerosol came from vehicle exhaust emissions, coal burning emissions, and biomass combustion emissions. In order to further quantify the contribution of major emission sources to carbonaceous aerosol, the results of this study using PMF to analyze the sources of carbonaceous aerosol showed that the main sources of carbonaceous aerosol in Huaxi District of Guiyang were coal combustion sources (29.3%), motor vehicle emission sources (21.5%), and biomass combustion sources (49.2%).

Pollution Characterization, Meteorological Effects, and Sources of Carbon Aerosols in PM2.5 in Urban Xiangtan during Winter

Pollution Characterization, Meteorological Effects, and Sources of Carbon Aerosols in PM2.5 in Urban Xiangtan during Winter

A comprehensive exploration of characteristics and source attribution of carbonaceous aerosols in PM2.5 in an East China megacity

A total of 84 PM2.5 (fine particulate matter) aerosol samples were collected between October 2020 and August 2021 within an urban site in Hangzhou, an East China megacity. Chemical species, such as organic carbon (OC), elemental carbon (EC), as well as char, soot, and n-alkanes, were analyzed to determine their pollution characteristics and source contributions. The mean yearly concentrations of OC, EC, char, soot, and total n-alkanes (∑n-alkane) were 8.76 ± 3.61 μg/m3, 1.44 ± 0.76 μg/m3, 1.21 ± 0.69 μg/m3, 0.3 ± 0.1 μg/m3, and 24.2 ± 10.6 ng/m3. The OC, EC, and ∑n-alkanes were found in the highest levels during winter and lowest during summer. There were strong correlations between OC and EC in both winter and spring, suggesting similar potential sources for these carbonaceous components in both seasons. There were poor correlations among the target pollutants due to summertime secondary organic carbon formation. Potential source contribution functions analysis showed that local pollution levels in winter and autumn were likely influenced by long-range transportation from the Plain of North China. Source index and positive matrix factorization models provided insights into the complex sources of n-alkanes in Hangzhou. Their major contributors were identified as terrestrial plant releases (32.7%), traffic emissions (28.8%), coal combustion (27.3%), and microbial activity (11.2%). Thus, controlling vehicular emissions and coal burning could be key measures to alleviate n-alkane concentrations in the atmosphere of Hangzhou, as well as other Chinese urban centers.

Ambient Air Quality in Upper Silesia Region Pre-During, and Post-COVID-19 Periods

Abstract Governments worldwide have established lockdowns to limit the spread of COVID-19 during the pandemic. The restrictions on travel and reduction of economic activity have led to a temporary improvement in air quality in several countries, especially in urban areas. This study investigates the changes in concentration levels of air pollutants (PM10, PM2.5, SO2, NO2, and bacterial aerosol) in the Upper Silesia Region of Southern Poland, during three periods: pre (March 2018 and 2019), during (March 2020, and 2021) and post-COVID-19 lockdown period (March 2022 and 2023). Our findings indicate that COVID-19 restrictions had a moderate impact on PM10 levels in comparison to pre- and post-COVID-19 periods. PM2.5 during lockdown was significantly lower than in the pre-COVID period and not significantly higher after COVID. PM10 and PM2.5 average concentrations decreased during COVID-19 restrictions by 27.8% and 12.7%, respectively. Compared with the results from the pre-COVID-19 phase, the reductions in NO2 and SO2 during the lockdown were 9.5% and 34.0%. Among other pollutants, bacterial aerosol (BA) concentrations also decreased during the lockdown by 23.0%, compared to the results from the pre-COVID-19 period.

Monitoring Aerosol Optical Depth for Air Quality Through Himawari-8 in Urban Area West Java Province Indonesia

Air quality is a crucial parameter in human life. One air quality indicator can be observed through Aerosol Optical Depth (AOD). If these substances are pollutants such as particulate matter, aerosols, and ozone, it is confident that air quality will deteriorate, threatening human health and causing climate change. AOD monitoring can be used as a basis for policymakers and related parties to maintain the stability of air quality in the atmosphere. Many ground observation stations monitor air quality by obtaining data on PM2.5 and PM10 aerosol particles. However, the number of ground stations is limited, resulting in incomplete data. Fortunately, remote sensing satellites have the advantage of covering large areas and providing continuous observations, with the ability to gather information on large-scale aerosol and obtain spatiotemporal distribution. Therefore, this research aims to obtain AOD through Himawari-8 and analyze the spatiotemporal air quality in urban areas of West Java based on AOD. The research methodology used in this study is descriptive analysis with an empirical research approach. Assisted by remote sensing technology and Geographic Information Systems, this research generates AOD data extraction that can be obtained from the new generation satellite of Himawari-8. The distribution of AOD levels and spatiotemporal monitoring in urban areas of West Java is very dynamic depending on anthropogenic activity in a particular area and time. Keywords: Aerosol Optical Depth (AOD), Air Quality, Himawari-8

Seasonal Variation and Source Identification of PM10 in an Industrialized City

AbstractA 1‐year PM10 sampling campaign from January 2019 to December 2019 is conducted in an urban industrial area Raipur, India. For the development of effective pollution control strategies, quantitative assessment of potentially toxic metals and accurate identification of pollutant sources are essential. The annual average PM10 aerosol mass concentration during the study period is recorded as 187.89 ± 91 µg m−3. PM10 concentrations are found to vary with meteorological parameters such as wind speed, temperature, rainfall, and humidity. Heavy metals including Fe, Mn, Ni, Pb, Zn, Al, Ba, Cr, Sr, Ga, Mg, and V are studied using atomic absorption spectroscopy (AAS). Seasonally, average winter time PM10 concentration (234.86 ± 104.3 µg m−3) is accounted higher as compared to summer (169.02 ± 27.1 µg m−3) and rainy season (106.28 ± 32.6 µg m−3) during the study period. The aerosol sources identified by positive matrix factorization (PMF) model are: iron and steel production (34.7%), vehicular emissions (29.3%), road dust (14.6%), heavy oil/petroleum (14.6%), and coal combustion (6.9%). Among these sources, iron and steel production contributes maximum in PM10 concentrations. The probable source locations are recognized through concentration weighted trajectory (CWT) analysis. The AirQ+ model is used to assess the health effects of regional PM10 concentrations.

Evaluation the in vivo behaviors of PM2.5 in rats using noninvasive PET imaging with mimic particles

Inhaled PM2.5 particles is harmful to human health. However, real-time tracking of PM2.5 particles and dynamic evaluation of the pharmacokinetic behaviors in vivo are still challenging. Here, PET imaging is utilized to noninvasively monitor the in vivo behavior of PM2.5 particles in rats. To mimic aerosol PM2.5 particles suspended in ambient air, 89Zr-labeled melanin nanoparticles (89Zr-MNP) are nebulized into microscopic liquid particles with a mean size of 2.5 μm. Then, the 89Zr-labeled PM2.5 mimic particles (89Zr-PM2.5) are administrated into rats via inhalation. PET imaging showed that 89Zr-PM2.5 mainly accumulated in the lungs for up to 384 h after administration. Besides, we also observe that a small amount of 89Zr-PM2.5 can penetrate the brain through the inhalation. Further PET imaging showed that enhanced uptakes of 18F-FDG and 18F-DPA-714 were found in the brain of rats upon PM2.5 mimic particle exposure, which revealed that pulmonary exposure to PM2.5 could cause potential damages to the brain. Note that abnormal glucose metabolism was reversed, but the neuroinflammation was permanent and could not be alleviated after ceasing PM2.5 exposure. Our results demonstrate that PET is a sensitive and feasible tool for evaluating the in vivo behaviors of PM2.5.

Mineral dust scavenges anthropogenic aerosols in polluted environment

Scavenging of anthropogenic aerosols by mineral dust in polluted environment was investigated in this work based on comprehensive observations of a long durative dust event from March 15 to 18, 2021 over north China. Combined observations of a Raman-depolarization lidar (355 nm) and a micro-pulse lidar (532 nm) show that dust particles become more spherical after mixing with anthropogenic pollutants in a polluted environment, likely due to mixing with anthropogenic aerosols. A sharply decease in anthropogenic aerosol in PM2.5 during dust event, especially for inorganic components (e.g., nitrate (NO3−), sulfate (SO42+), ammonium (NH4+)), supports the above viewpoint. The mass concentration of anthropogenic aerosol in PM2.5 decreased by 78% in late period of dust event. Further analyses suggest that such a decrease of anthropogenic aerosol in PM2.5 is caused by the coating of fine anthropogenic aerosols on coarse dust particles, rather than enhanced atmospheric diffusion capacity or weakened chemical reactions. Dust particles own high deposition velocity due to their coarse size. Hence, the coating of anthropogenic aerosols on dust particles enhance the scavenging of anthropogenic aerosols.

Impact of Gaseous Pollutants Reduction on Fine Particulate Matter and Its Secondary Inorganic Aerosols in Beijing–Tianjin–Hebei Region

A reduction in gaseous pollutants is an important method for mitigating PM2.5 concentration in the atmosphere, and the reduction in SO2/NH3/NOx is beneficial to control secondary inorganic aerosols in PM2.5. In this study, the Weather Research and Forecasting model with Chemistry model (WRF-Chem) was applied to study the impact on the PM2.5 and its secondary inorganic aerosols using the scenario simulation method in the Beijing–Tianjin–Hebei (BTH) region. The results showed that the BTH region is characterized by being NH3-rich and having a higher [NH4+]/[SO42−] ratio in southern BTH, with a ratio of more than 6.0. Source contribution to PM2.5 was highest in the 30%_SO2_40%_NH3_40%_NOx scenario, with a contribution ratio of 6.8%, followed by 3.8% contribution in the 30%_SO2_40%_NH3 scenario, and a 3.4% contribution in the 30%_SO2_60%_NH3_60%_NOx scenario. These results indicate that synergistic reduction measures may be suitable for controlling PM2.5 concentrations. A lower sensitivity factor, β value between PM2.5 and NH3 suggests that solely reducing NH3 emissions is not beneficial for the BTH region. However, this study indicates that the sensitivity of NO3− would improve significantly if NH3 emissions are reduced sharply. A slight reduction in NH3 was found to be beneficial for controlling NO3− in medium and small cities, while a significant decrease in NH3 would be more suitable for mega-cities. The study also observed that SO42− and its constituents continued to decrease with a consistent β value of approximately 0.14 in the 30%_SO2_%_NH3 scenario and between 10.5 and 12.8 in the 30%_SO2_%_NH3_%_NOx scenario. These findings suggest that a synergistic reduction in SO2-NH3-NOx emissions may be more effective in reducing PM2.5 concentrations and its secondary inorganic aerosols (SIAs). However, it is important to ensure that the reduction in NH3 and NOx exceeds 60% in low SO2 concentration conditions.

Effect of Clean Heating on Carbonaceous Aerosols in PM2.5 During the Heating Period in Baoding

In order to study the effects of clean heating measures on the concentration and source of carbonaceous aerosols in PM2.5 in Baoding, we collected PM2.5 samples in Baoding during the winter heating periods of 2014 and 2019. The concentrations of OC and EC in the samples were determined by using a DRI Model 2001A thermo-optical carbon analyzer.The results showed that the average values of ρ(OC) and ρ(EC) in the heating period in 2014 were 60.92 μg·m-3 and 18.15 μg·m-3, and the average values of ρ(OC) and ρ(EC) in the heating period in 2019 were 36.63 μg·m-3 and 6.07 μg·m-3. Compared with those in 2014, the concentrations of OC and EC decreased by 39.87% and 66.56%, respectively, in 2019; the decrease in EC was larger than that in OC, and the meteorological conditions in 2019 were more severe than those in 2014, which was not conducive to the spread of pollutants.The correlation analysis and SOC estimation of OC and EC indicated that the correlation R2 of OC and EC in Baoding in 2014 and 2019 were 0.874 and 0.811, respectively, indicating that OC and EC in Baoding had relatively consistent sources. The average values of ρ(SOC) in 2014 and 2019 were 16.59 μg·m-3 and 11.31 μg·m-3, respectively, and the contribution rates to OC were 27.23% and 30.87%, respectively. This showed that in 2019, compared with that in 2014, the primary pollution decreased, but the secondary pollution increased, and the atmospheric oxidation increased.The analysis of the pollution sources of carbonaceous aerosols revealed that in 2014 and 2019 before and after the implementation of clean heating, the carbonaceous aerosols in the atmosphere were mainly from biomass combustion, coal combustion, and vehicle exhaust emissions. However, the contribution from biomass burning and coal burning decreased in 2019 compared to that in 2014. The decrease in OC and EC concentrations was attributed to the control of coal-fired and biomass-fired sources by clean heating. At the same time, the implementation of clean heating measures reduced the contribution of primary emissions to carbonaceous aerosols in PM2.5 in Baoding City.

Compositions and Sources of Organic Aerosol in PM2.5 in Nanjing in China

Organic aerosols are harmful to the environment because of their impact on air quality and visibility. They have serious effects not only on living beings and ecosystems because of their biological toxicity, but they also have an indirect effect on regional climate change as cloud condensation nuclei and radiation force. Many measures have been applied to decrease air pollution. Although the air quality has greatly improved, the standard of the World Health Organization (WHO) is far from being met at present. In this study, fine particulates were collected in Nanjing throughout 2019, and high-performance liquid chromatography–electrospray ion–mass spectrometry/mass spectrometry (HPLC-ESI-MS/MS) was carried out to determine 14 organic acids, 10 nitrated phenols, 1 aldehyde, and 1 ketone in aerosol samples. In this study, we further determined the changes in the pollutants in Nanjing in recent years compared to previous studies and characterized more kinds of species in the air. We found that different kinds of nitrated phenols showed similar trends of being abundant in winter and substituted in spring, autumn, and summer. 4-Nitrophenol was the most abundant species (2.83 ng m−3) among the nitrated phenols. p-Coumaric acid presented the highest level in summer with an average concentration of 1.55 ng m−3, indicating that grass burning was significant in summer, possibly due to wheat stalk and perennial ryegrass burning. The positive matrix fraction (PMF) model was applied to identify the sources of aerosols in Nanjing, including coal burning, grass burning, softwood burning, hardwood burning, anthropogenic secondary organic aerosols (SOAs), and biogenic SOAs. Coal burning and softwood burning contributed much more to the total determined species with values of 20.3% and 18.2%, respectively. Anthropogenic SOAs contributed 17.1%, and hardwood burning contributed 16.7%. The contribution of biogenic SOAs was 15%, and the grass-burning source contribution was the lowest, with 12.6%. With consideration of the large contribution from anthropogenic combustion activities, more strict measures are required to reduce emission pollutants in the future.

Novel Single-Particle Analytical Technique for Inhalable Airborne Microplastic Particles by the Combined Use of Fluorescence Microscopy, Raman Microspectrometry, and SEM/EDX.

This study presents a novel and efficient method for analyzing inhalable airborne microplastics (AMPs) in ambient PM10 aerosols. Although many studies have been conducted on MPs in a variety of environments, the physicochemical characteristics of AMPs of inhalable size (<10 μm) in ambient PM10 are poorly understood because of the lack of suitable analytical methods. The method employed in this study combines fluorescence microscopy, Raman microspectrometry (RMS), and scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM/EDX) for an efficient and reliable investigation of inhalable AMPs, which constitute a small portion of ambient PM10 aerosol particles. Fluorescence microscopy and staining are used to select particles with high MP potential from ambient urban PM10 aerosols. The combination of RMS and SEM/EDX then allows for a detailed characterization of these particles on a single-particle basis. The results of the study show that ∼0.008% of the particles collected using a PM10 sampler had high MP potential, corresponding to ∼800 particles/m3. Among the stained particles of <10 μm, 27% were determined to be plastic, while the remaining 73% were found to be from tire/road wear. The number of inhalable AMPs was estimated to be 192 (±127) particles/m3. This study provides an important insight into the characteristics of inhalable AMPs in ambient PM10 aerosols that are particularly critical in respect of human health and climate change. The authors highlight that the use of a single fluorescence staining method can overestimate the number of inhalable AMPs in ambient air by including tire/road wear particles. To the best of their knowledge, this is the first study to demonstrate the morphological and spectroscopic characteristics of the same individual inhalable AMPs.