Water-soluble Ions In PM2 Research Articles

Characteristics of Water-soluble Ion Pollution in PM2.5 and the Causes of High Acidity of PM2.5 in Dalian

To gain a deeper understanding of the pollution status and influencing factors of fine particles （PM2.5） and their water-soluble ions （WSI） in Dalian and to implement precise control of pollution events such as haze and acid rain, PM2.5 samples were collected in Dalian from June 2021 to May 2022. Then, the mass concentrations of PM2.5 and WSI were determined using the weight method and ion chromatography, respectively, and the pollution characteristics and sources were analyzed. Furthermore, the causes of the high acidity of PM2.5 in spring were discussed. The results showed that the annual average mass concentrations of PM2.5 and WSI in Dalian during the sampling period were （33.24 ±28.87） μg·m-3 and （18.66 ±20.52） μg·m-3, respectively, and the secondary ions （SNA, including SO42-, NO3-, and NH4+） accounted for the highest proportion of WSI [（86.2 ±9.3）%]. The order of ion concentration levels from highest to lowest was： NO3->SO42->NH4+>Cl->K+>Ca2+>Na+>Mg2+>F-. Due to the influence of meteorological conditions and coal combustion emissions during the concentrated heating period from late autumn to early spring, the seasonal variation in PM2.5 and WSI was winter>spring>autumn>summer, whereas SNA was the highest in spring and the lowest in summer. The results of correlation and principal component analysis showed that WSI in PM2.5 was mainly from the secondary transformation of atmospheric SO2 and NO2 （contributing to the majority of SNA）, mixed sources of combustion and dust （characterized by K+, Mg2+, Cl-, and F-）, and sources of sand and sea salt （characterized by Na+, Ca2+, and Mg2+）. In summer, the main combustion source was biomass burning, whereas in autumn, winter, and spring, coal combustion emissions were predominant. The change in wind direction from autumn to winter brought by a shift from the source of sea salt to soil dust； additionally, the external pollution transported by northwest winds contributed to the complexity of the sources of WSI in PM2.5 during spring in Dalian. ISORROPIA-II model simulations suggested NH4NO3 as the most present solid aerosol form in PM2.5 in Dalian, followed by CaSO4 and （NH4）2SO4； compared to that in solid aerosols, more SNA existed in liquid aerosols. The annual average pH of PM2.5 in Dalian was 5.65 ±3.00, with pH values close to neutral in summer, autumn, and winter but significantly acidic in spring （2.03 ±3.18）. The high acidity observed in spring was attributed to the combination of low temperature, high humidity, and high SNA concentrations. These conditions resulted in higher aerosol water content and increased gas-to-particle conversion rates, ultimately leading to an ammonia-deficient environment. The backward trajectory and PSCF results indicated that the external transport of high acidity PM2.5 in spring mainly came from the northwest （45.0%） and southwest （40.8%） directions. Mobile source emissions made the most significant contribution to the transportation of pollutants in the former, forming high-pollution source areas in the Beijing-Tianjin-Hebei Region, which may have been mainly related to urban motor vehicle and port vessel emissions； the latter was influenced by relatively strong stationary sources and showed higher SO2 emissions in the southern part of Henan Province and the central part of Jiangsu Province.

Composition, sources and potential source regions of aerosols under contrasting environment conditions of Lanzhou, a valley city of western China: Observations by means of topographic relief

Chemical composition in PM2.5 (particulate matter with a diameter less than 2.5 μm) is essential information for evaluating their climate, environment and health effects. Concentrations of carbonaceous components and water-soluble ions in PM2.5 and the differences under varying environmental conditions in western China are poorly understood. During the period from July 2021 to July 2022, we conducted synchronous offline sampling of PM2.5 by deploying four identical sampling devices at altitudes ranging from 1500 m to 3600 m along the unique topography of the Lanzhou River Valley in western China. The major chemical components in PM2.5 are carbonaceous aerosols, NO3− and SO42− with the average concentrations of 28.07, 8.66 and 6.01 μg m−3 for the urban and surrounding rural areas, and 9.94, 2.45 and 3.11 μg m−3 for background site of Lanzhou. The concentrations of OC (organic carbon) and EC (elemental carbon) gradually decrease from urban area to suburban sites with increasing elevation. Coal combustion, vehicle emissions, secondary formation, salted aerosols and surface dust resuspension are found to be the primary sources of PM2.5 in both urban and rural areas of Lanzhou. The contribution of vehicle emissions decreases from urban areas to mountainous rural areas, contrary to the coal combustion and biomass burning. The study is significant for taking targeted measures to solve air pollution problem at different environmental conditions (urban, rural and background) over complex terrain.

Characteristics, source analysis, and health risk of PM2.5 in the urban tunnel environment associated with E10 petrol usage.

The increase in the number of motor vehicles has intensified the impact of traffic sources on air quality. Our aim was to illustrate the characteristics of PM2.5 emissions from vehicles fueled with E10 (a blend of 10% ethanol and 90% gasoline). A 21-day PM2.5 sampling in a fully enclosed urban tunnel and the component analysis were completed, and the characteristics, sources, and health risks of tunnel PM2.5 were studied. Moreover, the PM2.5 pH and its sensitivity were investigated by the thermodynamic model (ISORROPIA-II). In addition, exposure models were used to assess the health risks of different heavy metals in PM2.5 to humans through respiratory pathways. The two-point Cu/Sb ratio (entrance: 4.0 ± 1.4; exit: 4.4 ± 1.7) was close to the diagnostic criteria indicating a significant impact from brake wear. NO3-, NH4+, and SO42- constituted the main components of water-soluble ions in PM2.5 of the tunnel, accounting for 83.0-84.6% of the total concentration of inorganic ions. The organic carbon/elemental carbon ratio of the tunnel was greater than 2, indicating that the contribution of gasoline vehicle exhaust was significant. The average emission factors of PM2.5 in the fleet was 31.4 ± 16.6 mg/(veh·km). The pH value of PM2.5 in a tunnel environment (4.6 ± 0.3) was more acidic than that in an urban environment (4.9 ± 0.6). The main sensitive factors of PM2.5 pH in the urban atmosphere and tunnel environment were total ammonia (sum of gas and aerosol, NH3) and temperature, respectively. The results of the health risk assessment showed that Pb posed a potential carcinogenic risk, while As and Cd presented unacceptable risks for tunnel workers. The non-carcinogenic risk index of heavy metals of PM2.5 in the tunnel environment exceeded the safety threshold.

Implications of PM2.5 chemical composition in modulating microbial community dynamics during spring in Seoul

Particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) harbors a diverse microbial community. To assess the ecological dynamics and potential health risks associated with airborne microorganisms, it is crucial to understand the factors influencing microbial communities within PM2.5. This study investigated the influence of abiotic parameters, including air pollutants, PM2.5 chemical composition (water-soluble ions and organics), and meteorological variables, on microbial communities in PM2.5 samples collected in Seoul during the spring season. Results revealed a significant correlation between air pollutants and water-soluble ions of PM2.5 with microbial α-diversity indices. Additionally, air pollutants exerted a dominant effect on the microbial community structure, with stronger correlations observed for fungi than bacteria, whereas meteorological variables including temperature, pressure, wind speed, and humidity exerted a limited influence on fungal α-diversity. Furthermore, the results revealed specific water-soluble ions, such as SO42−, NO3−, and NH4+, as important factors influencing fungal α-diversity, whereas K+ negatively correlated with both microbial α-diversity. Moreover, PM2.5 microbial diversity was affected by organic compounds within PM2.5, with fatty acids exhibited a positive correlation with fungal diversity, while dicarboxylic acids exhibited a negative correlation with it. Furthermore, network analysis revealed direct links between air pollutants and dominant bacterial and fungal genera. The air pollutants exhibited a strong correlation with bacterial genera, such as Arthrospira and Clostridium, and fungal genera, including Aureobasidium and Cladosporium. These results will contribute to our understanding of the ecological dynamics of airborne microorganisms and provide insights into the potential risks associated with PM2.5 exposure.

Pollution Characteristics, Source Apportionment, and Meteorological Response of Water-soluble Ions in PM2.5 in Xinxiang, North China

Pollution variation, source characteristics, and meteorological effects of water-soluble inorganic ions (WSIIs) in PM2.5 were analyzed in Xinxiang city, Henan Province. PM2.5 samples and their chemical components were monitored online by using URG-9000 in four seasons:winter (January, 2022), spring (April, 2022), summer (July, 2022), and fall (October, 2022). The results showed that the TWSIIs had the same seasonal fluctuations as PM2.5. The average seasonal concentrations of WSIIs ranged from 19.62-72.15 μg·m-3, accounting for more than 60% of PM2.5, demonstrating that WSIIs were the major components of PM2.5. The annual concentration value of NO3-/SO42- was 2.11, which showed an increasing trend, suggesting predominantly mobile sources for secondary inorganic aerosols (SNA). Further, the molar concentration value [NH4+]/[NO3-] was 1.95, demonstrating that agriculture emissions were the dominant contributors to atmospheric nitrogen. Furthermore, the backward trajectory analysis showed that the concentrations of Ca2+ and Mg2+ were higher when the northeasterly wind prevailed and the wind speed was high. High values of SOR and NOR were correlated with low temperatures and high relative humidity (T < 8℃, RH > 60%), demonstrating that more gaseous precursors were converted into sulfate and nitrate. At high temperatures (T > 24℃), there was no apparent high NOR value like that for SOR, mainly due to the decomposition of NH4NO3 at high temperatures. Finally, backward trajectories associated with the PMF-resolved results were used to explore the regional transport characteristics. The results illustrated that dust sources in the study areas were mainly influenced by air trajectories originating from the northwest regions, whereas secondary sulfate, secondary nitrate, and biomass sources contributed more to WSIIs when wind speed and altitude air masses were low in the area surrounding the observation site.

Study of PM2.5 particles in the Gucheng, North China Plain: Morphology, mixing state, and source apportionment

The PM2.5 samples were collected at regular intervals from April to October 2017 at a meteorological station in Gucheng (GC) (39.08。 N, 115.44。E), Hebei Province, China. An important site in the North China Plains (NCP). The internal composition, mixing state, and elemental mapping were determined by scanning electron microscope (SEM) and Transmission electron microscope in scanning mode (STEM). Several core-shell (C–S) structures had sulfate and nitrate shells with mineral and sea salt cores, indicating particle aging and distant transport. The major water-soluble ions (WSIs) found were NH4+, Na+, K+, Ca2+, Mg2+, Br−, Cl−, NO2−, NO3−, PO43− and SO42−. The three most dominant ions were NH4+, NO3−, and SO42−, with an average concentration of 16.02, 14.90, and 11.03 μg/m3, respectively, accounting for more than 80% of the total WSIs in PM2.5. Ion balance measurements showed that the PM2.5 were slightly acidic. [NO3−/SO42−] ratio of 1.11 shows a slightly high contribution from the mobile sources. The sea salt contribution was investigated by the molar ratio Cl−/Na+, which was slightly higher (1.9) than that for seawater (1.7), indicating an additional source, other than sea salt, for Cl− and Na+. The SOR was higher at all temperatures than NOR; SOR was strongly correlated with temperature, indicating gas-phase oxidation of SO2 to SO42− by OH radicle. The SO42− being positively correlated with NH4+ suggests NH4HSO4 and (NH4)2SO4 to be the dominant forms of SO42− present. Based on the internal structure, principal component analysis (PCA), and positive matrix factorization (PMF) analysis, the major sources of sulfate were industrial emissions from the surrounding cities, also confirmed by the Hysplit backward trajectory analysis. Nitrates arise mainly from local vehicular and industrial emissions and ammonia from fertilizers and animal manure. The local emissions and the regional transport from Shanxi, Shaanxi, Tianjin, Beijing, and Inner Mongolia were the main contributors to PM2.5 particles.

Temporal and spatial dynamics in emission of water-soluble ions in fine particulate matter during forest fires in Southwest China

AimsThe aim of this study was to analyze changes in emission of water-soluble ions in fine particulate matter over time and in different southwest forest areas in China based on China’s Forestry Statistical Yearbook and MODIS satellite fire point data.MethodsWe took 6 dominant tree species samples in the southwestern forest region of China and simulated combustion using controllable biomass combustion devices. Based on the spatial analysis method of ArcGIS, combining satellite fire point data and official statistical yearbooks, we analyzed the spatial and temporal dynamics of emissions of water-soluble ions in PM2.5 released by forest fires in southwestern forest areas from 2004 to 2021.ResultsThe total amount of forest biomass combusted in southwest forest areas was 64.43 kt. Among the different forest types, the proportion of burnt subtropical evergreen broad-leaved forest was the largest (60.49%) followed by subtropical mixed coniferous and broad-leaved forest (22.78%) and subtropical evergreen coniferous forest (16.72%). During the study period, 61.19 t of water-soluble ions were released in PM2.5 from forest fires, and the emissions of Li+, Na+, NH4+, K+, Mg2+, Ca2+, F−, Cl−, Br−, NO3−, PO43− and SO42− were 0.48 t, 11.54 t, 2.51 t, 19.44 t, 2.12 t, 2.92 t, 1.94 t, 12.70 t, 1.12 t, 1.18 t, 1.17 t and 4.07 t, respectively. Yunnan was the province with the highest emissions of water-soluble ions in PM2.5 in the southwest forest areas, and the concentration K+ was the highest. Emission of water-soluble ions in Yunnan and Sichuan all showed a significant downward trend, while the overall decrease in Tibet, Chongqing and Guizhou was not significant. The peak emission of water-soluble ions in PM2.5 during forest fires appeared in spring and winter, which accounted for 87.66% of the total emission.DiscussionThis study reveals the spatiotemporal changes in water-soluble ion emissions from forest fires, by studying the spatiotemporal dynamics of water-soluble ions in PM2.5, we can better understand the sources, distribution, and change patterns of these ions, as well as their impact on the atmospheric environment, ecosystems, and climate change. This information is crucial for predicting and managing air pollution, as well as developing effective forest management and environmental protection policies to respond to fires; and hence concerted fire prevention efforts should be made in each province, taking into account the season with higher probability of fire occurrence to reduce the potential impact of fire-related pollutions.

Outdoor PM2.5 and their water-soluble ions in the Northern part of the Persian Gulf

Background: The environmental conditions potentially predispose the northern part of the Persian Gulf to the occurrence of dust storms. Outdoor PM2.5 and their water-soluble ions in Bushehr port were studied from December 2016 to September 2017. Methods: A total of 46 outdoor PM2.5 samples were collected by high-volume air sampler and eight water-soluble ions, including Ca2+, Mg2+, Na+, K+, F- , Cl- , NO3 - , and SO4 2- in PM2.5 were also measured by ion chromatography (IC). Results: The 24-hour average concentration of PM2.5 was in the range of 22.09 to 292.45 µg/m3 . The mean concentration of water-soluble ions in PM2.5 was in the range of 0.10±0.14 to 6.76±4.63 µg/m3 . The major water-soluble ions were the secondary inorganic aerosols (SO4 2- and NO3 - ), which accounted for nearly 41% of total water-soluble ions in PM2.5. The total water-soluble ions level of PM2.5 in winter was higher than that in spring and summer. The positive matrix factorization (PMF) model showed that the source contributions of PM2.5 were in the order of dust (55.8%), sea salt (17.1%), secondary sulfate (11.8%), industries (7%), vehicular emission (4.7%), and secondary nitrate (3.7%). Conclusion: According to the results, dust and sea salt are the main sources of water-soluble ions in PM2.5 in Bushehr port, which should attract much attention.

Chemical characteristics of PM2.5 emitted from motor vehicles exhaust under the plateau with low oxygen content

To investigate the chemical characteristics of PM2.5 emitted from motor vehicles under the plateau with low oxygen content, tunnel experiments and bench tests were carried out in Yunnan. By analyzing the component characteristics of carbonaceous components, inorganic elements and water-soluble ions in PM2.5, the differences in the concentrations and emission factors of PM2.5 were described and compared respectively, significant differences in the chemical characteristics of OC, EC in PM2.5 were determined. The study indicated the concentrations of PM2.5 in the tunnels of Caohai and Xidu were 251.88 ± 34.62 and 536.75 ± 97.29 μg/m3, respectively. The emission factor of PM2.5 in the Caohai Tunnel was 201.56 ± 60.92 mg/veh/km, and that for gasoline and diesel vehicles in bench tests were 73.62 ± 23.47 and 531.45 ± 107.46 mg/kg fuel. This study indicated the concentrations and emission factors of PM2.5 emitted from motor vehicles in the plateau were significantly higher than those in plain, meanwhile, the higher content of OC and emission factor of CO emitted from motor vehicles in the bench tests strongly indicated the inadequate combustion of fuels in engine under the plateau with low oxygen content. The results can enrich the local database of motor vehicles exhaust in the plateau and support the effective formulation of control policies.

Characteristics and atmospheric processes of water-soluble ions in PM2.5 and PM10 over an industrial city in the National Capital Region (NCR) of India

This study investigates water-soluble inorganic ions (WSIIs), their potential formation mechanism, particle bound water content and acidity (pH) in ambient aerosols in Ghaziabad, an industrial city located downwind of Delhi, the Indian National Capital. 24-hour integrated PM2.5 and PM10 samples were collected using collocated samplers at two receptor locations every third day throughout the year. The samples were collected on Nylon filter substrates (preceded by a denuder upstream for capturing acidic gases) and Teflon filter substrates for WSII and mass measurements, respectively. Further, on-site meteorological parameters were recorded at both locations. The annual average PM concentrations observed were: PM2.5: 144 ± 81 μgm−3 (Site A), 163 ± 95 μgm−3 (Site B); and PM10: 245 ± 116 μgm−3 (Site A), 279 ± 152 μgm−3 (Site B). On average, SO42−, NO3−, Cl− and NH4+ contributed to ∼90% to PM2.5WSII mass and ∼82% to PM10WSII mass, which in turn made up ∼35% of PM2.5 mass and ∼23% of the PM10 mass across both sites. SO42− concentration was found to be highest followed by NO3−, NH4+ and Cl− for both PM fractions. Mann-Whitney U test revealed that both sites were similar with respect to WSII mass indicating city's airshed average concentration with respect to the major ions. The highest WSII contribution to the total PM was found in winter season (37–40% for PM2.5 and 27–31% for PM10) followed by monsoon (36–38% for PM2.5 and 18–21% for PM10), post-monsoon (28–34% for PM2.5 and 21–23% for PM10) and pre-monsoon (21–27% for PM2.5 and 15% for PM10). High contribution during winter was because of higher emissions of precursor gases in combination with moderate relative humidity (36–59%) and minimal precipitation (average ∼0.2 mm). Sulphur Oxidation Ratio and Nitrogen Oxidation Ratio indicated high photochemical oxidation with a greater extent of SO42− formation compared to NO3−. Although high concentrations of NH3 gas were observed, there was insufficient NH4+ ions for neutralizing counter ions with Ammonium Neutralization Ratio values of 0.76±0.14 for PM2.5 and 0.62±0.14 for PM10. Finally, aerosol liquid water content (ALWC) and acidity were estimated using a thermodynamic equilibrium model, ISORROPIA-II. It was found that PM2.5 pH varied from 2.9 to 6.2 (avg. 4.4±0.8) and the PM2.5 mass doubled at RH ∼90% because of the high particle bound water. Consequently, a reduction in SO2 would result in instantaneous cuts of SO42−, PM2.5, and ALWC.

Characterisation and Source Identification of Inorganic Water-Soluble Ions in PM2.5 in a Small-Size Steel City of China

Ambient PM2.5 samples were collected in Laiwu, a small industrial city in China known for steel production, to measure and evaluate the mass concentrations of PM2.5 and the inorganic water-soluble ions (IWS ions). The highest PM2.5 value recorded was 251.28 μg/m3, which occurred during winter and was lower than other major Chinese cities. The spatial distribution showed that the center of the city, which is connected to the downtown area, was heavily polluted (170 μg/m3 higher) compared to the suburbs. With the exception of winter, the weight of PM2.5 was dominated by IWS ions, with three secondary ions (NO3 -, SO4 2-, and NH4 +) accounting for more than 70% of the total ions in mass. This percentage is higher than that of big cities. An increase in sulfur oxidation ratios (SOR), nitrogen oxidation rate (NOR), and anion equivalent/cation equivalent (AE/CE) indicated that the atmosphere in Laiwu was more oxidized than other big cities. The ion analysis revealed that PM2.5 was highly correlated with NO3 -, SO4 2-, and NH4 +. The principal component analysis indicated that district heating during winter and industrial output and secondary transformation during summer were the major sources of the water-soluble ions. The backward trajectory study identified the north of Shandong Province as the likely source-area that affected air quality in Laiwu.

Pollution Characteristics and Sources of Water-soluble Ions in PM2.5 in Zhengzhou City

In order to explore the pollution characteristics, seasonal variations, and sources of water-soluble inorganic ions (WSIIs) in PM2.5 in Zhengzhou, PM2.5 samples were seasonally collected from December 2020 to October 2021; then, combining gaseous pollutants (SO2, NO2, and O3) and meteorological parameters (temperature and relative humidity), nine WSIIs (NO3-, NH4+, SO42-, Ca2+, K+, Na+, Mg2+, F-, and Cl-) were analyzed. The results showed that the annual average concentration of the total water-soluble ions (TWSIIs) was (39.34±21.56) μg·m-3for the four seasons, showing obvious seasonal variations with the maximum value in winter and the minimum value in summer. Annual PM2.5 was slightly alkaline in Zhengzhou, and NH4+ most likely existed in the form of NH4NO3 and (NH4)2SO4. The average sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) were 0.35 and 0.19, respectively, indicating that SO42- and NO3- mainly derived from secondary formation. The main potential source regions of WSIIs obtained by the concentration weight trajectory (CWT) model showed temporal and spatial variations. The significant sources of WSIIs based on principal component analysis (PCA) were dust, secondary generation, combustion, and industrial activities, which were obviously influenced by wind direction and speed in Zhengzhou.

华北煤矿区PM&lt;sub&gt;2.5&lt;/sub&gt;中水溶性离子特征及来源解析

华北煤矿区PM&lt;sub&gt;2.5&lt;/sub&gt;中水溶性离子特征及来源解析

Distribution Characteristics and Source Apportionment of Winter Carbonaceous Aerosols in a Rural Area in Shandong, China

PM2.5 samples were collected for 15 consecutive days in a rural area in Shandong from January to February 2022. The carbon components and water-soluble ions in PM2.5 were measured, and the distribution characteristics and sources of the carbonaceous aerosols were analysed. It was found that the concentrations of PM2.5 in the region were high in winter (55.79–236.11 μg/m³). Organic carbon (OC) and elemental carbon (EC) accounted for 11.61% and 4.57% of PM2.5, respectively. The average concentrations of OC (19.01 μg/m³) and EC (7.49 μg/m³) in PM2.5 were high. The mean value of secondary organic carbon (SOC), estimated by the minimum R squared (MRS) method, was 14.76 μg/m3, accounting for a high proportion of OC (79.41%). Four OC fractions (OC1, OC2, OC3, and OC4) were significantly correlated with SOC, indicating that the OC components contained a large amount of SOC. OC3, OC4, EC1, and OC2 dominated (accounting for 80% of TC) among the eight carbon fractions. Water-soluble organic carbon (WSOC, 12.82 μg/m³) and methanol-soluble organic carbon (MSOC) (16.28 μg/m³) accounted for 67.47% and 84.99% of OC, respectively, indicating that SOC accounted for a high proportion of OC. The proportion of eight water-soluble ions in PM2.5 was 47.48%. NH4+ can neutralise most of the SO42− and NO3−, forming (NH4)2SO4 and NH4NO3, while Cl− mainly exists in the form of KCl and MgCl2. The ratios of some typical components showed that PM2.5 was not only affected by local combustion sources, but also by mobile sources. The cluster analysis results of the backward trajectory model showed that primary and secondary sources in Shandong Province had a great impact on PM2.5 (64%). The analysis results of the positive matrix factorisation (PMF) model showed that the sources of PM2.5 in the region included mobile sources, primary combustion sources, secondary sources, and dust sources, among which secondary sources contributed the most (60.46%).

Chemical Component of Particulate Matters and VOCs Characteristics During Vehicle Brake Processes

Six sets of brake systems were tested using a brake dynamometer, and the brake wear particles (BWPs) and volatile organic compounds (VOCs) were collected during the braking process. In total, 39 elements, 12 water-soluble ions, 7 carbon components, and 18 polycyclic aromatic hydrocarbons (PAHs) in BWPs were extracted and detected, and 74 VOCs in gas samples were analyzed. The average mass fractions of 12 inorganic elements (i.e., Sb, Mg, Cu, Zn, Ti, Ca, Si, Zr, K, Ba, Al, and Fe) with higher contents in PM2.5 and PM10 were 43.4% and 40.3%, respectively, and the average mass fraction of Fe was the highest, accounting for 16.6% and 13.1% of PM2.5 and PM10, respectively. The average mass fractions of the 12 water-soluble ions in PM2.5 and PM10 were 16.5% and 12.6%, respectively, and NO3-, SO42-, and Ca2+ were the ions with high contents. The average mass fraction of total carbon (TC) in PM2.5 and PM10 were 21.9% and 18.1%, respectively, and the average mass fraction of organic carbon (OC) was approximately five times that of elemental carbon (EC). There were six types of PAHs with a detection rate greater than 50%, among which naphthalene (Nap) was the most abundant. The average mass concentration of 74 VOCs was 316.04 μg·m-3, of which the aromatic hydrocarbon had the highest mass concentration. The compositions of BWPs and VOCs emitted by the six sets of brake systems were quite different, which was mainly determined by the brand and raw materials of the brake pads.

Airborne microbial community structure and potential pathogen identification across the PM size fractions and seasons in the urban atmosphere

As a vital component of airborne bioaerosols, bacteria and fungi seriously endanger human health as pathogens and allergens. However, comprehensive effects of environmental variables on airborne microbial community structures remain poorly understood across the PM sizes and seasons. We collected atmospheric PM1.0, PM2.5, and PM10 samples in Hefei, a typical rapidly-developing city in East China, across three seasons, and performed a comprehensive analysis of airborne microbial community structures using qPCR and high-throughput sequencing. Overall the bacterial and fungal abundances in PM1.0 were one to two orders of magnitude higher than those in PM2.5 and PM10 across seasons, but their α-diversity tended to increase from PM1.0 to PM10. The bacterial gene abundances showed a strong positive correlation (P < 0.05) with atmospheric SO2 and NO2 concentrations and air quality index. The bacterial gene abundances were significantly higher (P = 0.001) than fungi, and the bacterial diversity showed stronger seasonality. The PM sizes influenced distribution patterns for airborne microbial communities within the same season. Source-tracking analysis indicated that soils, plants, human and animal feces represented important sources of airborne bacteria with a total relative abundance of more than 60% in summer, but total abundance from the unidentified sources surpassed in fall and winter. Total 10 potential bacterial and 12 potential fungal pathogens were identified at the species level with the highest relative abundances in summer, and their abundances increased with the PM sizes. Together, our results indicated that a complex set of environmental factors, including water-soluble ions in PM, changes in air pollutant levels and meteorological conditions, and shifts in the relative importance of available microbial sources, acted to control the seasonal compositions of microbial communities in the urban atmosphere.

Characteristics of PM2.5 and Its Correlation with Feed, Manure and NH3 in a Pig-Fattening House.

Fine particulate matter (PM), including PM2.5 in pig houses, has received increasing attention due to the potential health risks associated with PM. At present, most studies have analyzed PM2.5 in Chinese pig houses utilizing natural ventilation. These results, however, are strongly affected by the internal structure and regional environment, thus limiting their applicability to non-mechanically ventilated pig houses. This experiment was carried out in an environmentally controlled pig house. The animal feeding operation and manure management in the house were typical for Southwest China. To reduce the influence of various environmental factors on PM2.5, the temperature and humidity in the house were maintained in a relatively stable state by using an environmental control system. The concentration of PM2.5 in the pig house was monitored, while the biological contents and chemical composition of PM2.5 were analyzed, and feed, manure, and dust particles were scanned using an electron microscope. Moreover, bacterial and fungal contents and some water-soluble ions in PM2.5 were identified. The results showed that the concentration of PM2.5 in the pig house was strongly affected by pig activity, and a phenomenon of forming secondary particles in the pig house was found, although the transformation intensity was low. The concentration of PM2.5 had negative correlations of 0.27 and 0.18 with ammonia and hydrogen sulfide, respectively. Interestingly, a stronger correlation was observed between ammonia and hydrogen sulfide and ammonia and carbon dioxide concentrations (the concentration of ammonia had stronger positive correlations with hydrogen sulfide and carbon dioxide concentrations at +0.44 and +0.59, respectively). The main potential sources of PM2.5 production were feed and manure. We speculate that manure could contribute to the broken, rough, and angular particles that formed the pig house PM2.5 that easily adhered to other components.

Influence of urban outflow on water-soluble ions in PM2.5 and > PM2.5 particles at a suburban Ho Chi Minh City site, Vietnam

In this study, a comprehensive dataset of daily water-soluble ions (WSIs) in PM2.5 and > PM2.5 particles was investigated at the suburban Ho Chi Minh City (HCMC) site, Vietnam. The study aimed to explore an impact of urban emission from the HCMC downtown on the air quality at the downwind region. The urban outflow was characterized by higher concentrations of WSIs in PM2.5 and their gaseous precursors even during the rainy months, and lower sea-salt fractions when compared to those observed under marine air masses. In PM2.5, SO42− was the most dominant species accounting for approximately 50% of the total ion content, followed by NO3−, K+, and NH4+. SO42− is mainly formed through gas-phase reactions especially under urban outflow when stronger oxidation capacity and higher levels of its precursors were observed. Based on Hysplit backward trajectories and concentration weighted trajectory analysis, it is found that the contribution of biomass burning to PM2.5 potassium was elevated consistent with the effect of air masses originated from the equatorial Southeast Asia countries. Hierarchical cluster analysis showed very strong correlation among three components K+–Cl−–NO3−, indicating that secondary NO3− formation through heterogeneous process was heavily dependent on the presence of biomass burning aerosols. The findings imply that the sampling site is impacted by urban emission and can be adopted as the mix receptor site for air quality management in the HCMC metropolitan area, an emerging megacity in developing country.

Pollution Characteristics of Water-soluble Ions in PM2.5 During the Lantern Festival of 2021 in Zibo City

Based on the online ion data, we have analyzed the cause of a PM2.5 pollution episode, which happened during the Lantern Festival in Zibo in 2021. The pollution characteristics of water-soluble ion components were analyzed, the formation mechanism of secondary inorganic ions (SNA) was discussed, and the changes in the liquid water content (LWC) and pH value of particulate matter before and after pollution were comparatively analyzed. The results showed that the pollution period before the Lantern Festival (T1) and the pollution period at night (T2) ρ(WSIIs) during the Lantern Festival were 46.83 μg·m-3 and 71.18 μg·m-3, respectively, which were 2.3 times and 3.6 times that of the cleaning period, respectively. Among them, the growth multiple of SNA during the T1 period was greater[ρ(NO3-) was 2.9 times, ρ(SO42-) was 2.8 times, and ρ(NH4+) was 2.4 times] than the growth multiple of PM2.5 (2.1 times), which showed that the increase in SNA concentration during the T1 period was the main reason for the increase in PM2.5 concentration. Furthermore, the Cl-, K+, and Mg2+ concentrations, which were 4.0, 14.8, and 16.5 times that of the cleaning period, respectively, increased significantly during the T2 period, indicating that the fireworks and firecrackers caused the rapid increase in the PM2.5 concentration during the T2 period. The LWC during the pollution period was 49.37 μg·m-3, which was 2.9 times that of the cleaning period. LWC was mainly affected by RH and NH4+ during the T1 period and was also affected by Mg2+ during the T2 period. The average pH during the pollution period in Zibo was 4.79±1.54, which was 0.14 lower than that during the cleaning period. The pH during the T1 period was affected by the combined effects of SO42- and NH4+, which made it decrease 0.53 compared to that during the cleaning period. The pH value during the T2 period may be affected by the K+, Cl-, and Mg2+ emitted from the fireworks and firecrackers, causing the pH to increase 0.65 compared to that during the cleaning period. The formation mechanism showed that SO42- was mainly generated by heterogeneous hydrolysis during the pollution episode, whereas NO3- was mainly generated by homogeneous reactions. On the whole, during the pollution episode, the increase in PM2.5 concentration before the Lantern Festival was mainly caused by the increase in SNA concentration, and the increase the night of the Lantern Festival was mainly caused by setting off fireworks and firecrackers.

Chemical significance and source apportionment of fine particles (PM2.5) in an industrial port area in East Asia

This study explored the chemical significance, seasonal variation, spatial distribution, and source apportionment of fine particles (PM2.5) in an industrial port area. 24-h PM2.5 was simultaneously sampled at three port sites. Five chemical contents in PM2.5 including water-soluble ions (WSIs), metallic elements, carbonaceous content, anhydrosugars, and organic acids were then analyzed. The source apportionment of PM2.5 was further resolved by trajectory simulation, principal component analysis (PCA), and chemical mass balance (CMB) receptor model. Both local sources and long-range transport contributed to the rise-up of PM2.5 levels. Secondary inorganic aerosols (SIAs) dominated WSIs in PM2.5. Crustal elements (Mg, Al, Ca, Fe, and K) dominated the metallic content of PM2.5, while trace elements (Ni, V, Cr, Zn, and Pb) were originated from anthropogenic sources. Ship emissions in the seaport and offshores caused high V/Ni ratios in summer. High OC/EC (2.04–2.23) and SOC/OC (28–34%) ratios were observed in fall and winter, implying the potential formation of secondary organic aerosols (SOAs) in atmosphere. High correlation of levoglucosan and K+ indicated that PM2.5 was greatly influenced by biomass burning (BB) in winter. Polluted air masses with high PM2.5 levels of 43.33 ± 11.84 μg/m3 in winter were blown from the norths by Asian Northeastern Monsoons (ANMs), while clean air masses with low PM2.5 levels of 9.13 ± 2.75 μg/m3 in summer came mainly from the oceans via Asian Southwestern Monsoons (ASMs). Source apportionment resolution showed that the dominant sources of PM2.5 in the Kaohsiung Seaport were industrial emissions, secondary aerosols (SIAs/SOAs), ship/vehicular exhausts, oceanic spray, and soil dust.