Seasonal variation and chemical composition of particulate matter: A study by XPS, ICP-AES and sequential microanalysis using Raman with SEM/EDS

Toxic effect and mRNA mechanism of moon dust simulant induced pulmonary inflammation in rats

Moon dust presents a significant hazard to manned moon exploration missions, yet our understanding of its toxicity remains limited. The objective of this study is to investigate the pattern and mechanism of lung inflammation induced by subacute exposure to moon dust simulants (MDS) in rats. SD rats were exposed to MDS and silica dioxide through oral and nasal inhalation for 6 hours per day continuously for 15 days. Pathological analysis indicated that the toxicity of MDS was lower than that of silica dioxide. MDS led to a notable recruitment and infiltration of macrophages in the rat lungs. Material characterization and biochemical analysis revealed that SiO2, Fe2O3, and TiO2 could be crucial sources of MDS toxicity. The study revealed that MDS-induced oxidative stress response can lead to pulmonary inflammation, which potentially may progress to lung fibrosis. Transcriptome sequencing revealed that MDS suppresses the PI3K-AKT signaling pathway, triggers the Tnfr2 non-classical NF-kB pathway and IL-17 signaling pathway, ultimately causing lung inflammation and activating predominantly antioxidant immune responses. Moreover, the study identified the involvement of upregulated genes IL1b, csf2, and Sod2 in regulating immune responses in rat lungs, making them potential key targets for preventing pulmonary toxicity related to moon dust exposure. These findings are expected to aid in safeguarding astronauts against the hazardous effects of moon dust and offer fresh insights into the implications and mechanisms of moon dust toxicity.

PM2.5-bound trace metals in an urban area of Northern Mexico during the COVID-19 pandemic: characterization, sources, and health risk

Abstract

A field study was carried out in the Metropolitan Area of Monterrey (MAM), the second most populated city in Mexico, characterized by increasing urbanization, high traffic density, and intense industrial activity. These characteristics commonly present high concentrations of air pollutants leading to the degradation of air quality. PM2.5 was analyzed for heavy metals at two urban sites located within the MAM (Juarez and San Bernabe) in order to determine sources, health risk, morphology, and elemental content during the COVID-19 pandemic (autumn 2020 and spring 2021). Twenty-four-hour samples of PM2.5 were collected at each site during 30-day periods using high-volume equipment. Gravimetric concentrations and 11 metals were measured (Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Ni, Cr, and Pb) by different analytical techniques (flame atomic absorption spectroscopy, graphite furnace atomic absorption spectroscopy, and inductively coupled plasma optical emission spectroscopy). Selected samples were analyzed by scanning electron microscopy-energy-disperse spectroscopy in order to characterize their morphology and elemental content. PM2.5 concentrations exceeded the Mexican standard and WHO guidelines in Juarez during spring 2021. Cu, Cd, and Co were highly enriched by anthropogenic sources, and Ni, K, Cr, and Pb had a moderate enrichment. Mg, Mn, and Ca were of crustal origin. Bivariate statistics and PCA confirmed that alkaline metals originated from crustal sources and that the main sources of trace metals included traffic emissions, resuspension from soil/road dust, steel industry, smelting, and non-exhaust emissions at both sites. Lifetime cancer risk coefficients did not exceed the permissible levels established by EPA and WHO, implying that local residents are not at risk of developing cancer. Non-carcinogenic risk coefficients revealed that there is a possible risk of suffering cardiovascular and respiratory diseases due to inhalation of cobalt at the study sites.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11869-023-01372-7.

Source identification and apportionment of ambient particulate matter in Beijing using an advanced computer-controlled scanning electron microscopy (CCSEM) system

The use of electron microscopy to analyze the morphology, composition, and sources of atmospheric particles has been studied extensively worldwide. However, in China, there are few studies on single-particle source analysis based on computer-controlled scanning electron microscopy (CCSEM) technology for a large number of particles, and the related technical methods need to be established and improved. In this study, ambient particulate matter (PM) was collected simultaneously from urban, suburban, and background areas of Beijing in spring 2018 and subsequently characterized using the IntelliSEM-EPAS™ technology (an advanced CCSEM software). The deposition velocity model was used to deduce the size distribution and calculate the concentration of ambient PM. Based on the k-means algorithm and empirical rules, all particles investigated were quantitatively apportioned to nine major sources, including soil/road dust, carbonates-silicates, carbonates, irregular carbonaceous particles, irregular iron oxides, combustion/industry, calcium sulfate, secondary particles, and salt-related particles. The size-resolved contributions (mass and number) of different sources were calculated. For example, soil/road dust (65.1 %), carbonate-silicate (16.1 %), and carbonate (7.1 %) were the top three sources contributing to PM₁₀ mass. This study was the first localized application of IntelliSEM-EPAS technology in China, demonstrating its great promise in PM source apportionment. For further accurate and refined source apportionment, it is essential to build localized individual particle source profiles.

Chemical and morpho-structural characterization of atmospheric aerosol (PM10 and PM2.5) in a city of São Paulo state, Brazil

To access the sources of air pollutants is crucial to control atmospheric pollution in urban areas, minimizing human exposure. Particulate matter is a pollutant of great concern making its chemical and morpho-structural characterization of enormous importance. The present work aims at the characterization of atmospheric PM₁₀ and PM_2.5. Data of the aerosol mass concentration was correlated by multivariate analysis with water-soluble ion fraction composition accessed by ion chromatography (IC), as well as with meteorological information and air mass backward trajectories. The gravimetric analysis presented average values 3 to 4 times higher than the guide values recommended by the World Health Organization (WHO). A morpho-structural analysis by SEM/FEG coupled to EDS was also carried out identifying the coarse fraction elements from minerals and from soil resuspension organic spherical particles that originated from combustion processes as well as Ti, associated with long-distance transportation. In the fine fraction, Zn with origin probably in tires and vehicle brakes was found. These origins were confirmed by the air masses' backward trajectories obtained by the HYSPLIT model (NOAA). This study contributes to a better understanding of the complex composition of the particulate material in the atmosphere of Araraquara City, resulting from the combination of local and long-distance sources, and serves as a basis for the comparison with future studies related to the air quality at this and other regions in Brazil and in the world.

Morphological and elemental characterization of leaf-deposited particulate matter from different source types: a microscopic investigation

Particulate matter (PM) deposition on urban green enables the collection of particulate pollution from a diversity of contexts, and insight into the physico-chemical profiles of PM is key for identifying main polluting sources. This study reports on the morphological and elemental characterization of PM_2-10 deposited on ivy leaves from five different environments (forest, rural, roadside, train, industry) in the region of Antwerp, Belgium. Ca. 40,000 leaf-deposited particles were thoroughly investigated by particle-based analysis using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) and their physico-chemical characteristics were explored for PM source apportionment purposes. The size distribution of all deposited particles was biased towards small-sized PM, with 32% of the particles smaller than 2.5 μm (PM_2.5) and median diameters of 2.80-3.09 μm. The source type influenced both the particles' size and morphology (aspect ratio and shape), with roadside particles being overall the smallest in size and the most spherical. While forest and rural elemental profiles were associated with natural PM, the industry particles revealed the highest anthropogenic metal input. PM_2-10 profiles for roadside and train sites were rather comparable and only distinguishable when evaluating the fine (2-2.5 μm) and coarse (2.5-10 μm) PM fractions separately, which enabled the identification of a larger contribution of combustion-derived particles (small, circular, Fe-enriched) at the roadside compared to the train. Random forest prediction model classified the source type correctly for 61-85% of the leaf-deposited PM. The still modest classification accuracy denotes the influence of regional background PM and demands for additional fingerprinting techniques to facilitate source apportionment. Nonetheless, the obtained results demonstrate the utility of leaf particle-based analysis to fingerprint and pinpoint source-specific PM, particularly when considering both the composition and size of leaf-deposited particles.

Ruscogenin attenuates particulate matter-induced acute lung injury in mice via protecting pulmonary endothelial barrier and inhibiting TLR4 signaling pathway

The inhalation of particulate matter (PM) is closely related to respiratory damage, including acute lung injury (ALI), characterized by inflammatory fluid edema and disturbed alveolar-capillary permeability. Ruscogenin (RUS), the main active ingredient in the traditional Chinese medicine Ophiopogonis japonicus, has been found to exhibit anti-inflammatory activity and rescue LPS-induced ALI. In this study, we investigated whether and how RUS exerted therapeutic effects on PM-induced ALI. RUS (0.1, 0.3, 1 mg·kg-1·d-1) was orally administered to mice prior to or after intratracheal instillation of PM suspension (50 mg/kg). We showed that RUS administration either prior to or after PM challenge significantly attenuated PM-induced pathological injury, lung edema, vascular leakage and VE-cadherin expression in lung tissue. RUS administration significantly decreased the levels of cytokines IL-6 and IL-1β, as well as the levels of NO and MPO in both bronchoalveolar lavage fluid (BALF) and serum. RUS administration dose-dependently suppressed the phosphorylation of NF-κB p65 and the expression of TLR4 and MyD88 in lung tissue. Furthermore, TLR4 knockout partly diminished PM-induced lung injury, and abolished the protective effects of RUS in PM-instilled mice. In conclusion, RUS effectively alleviates PM-induced ALI probably by inhibition of vascular leakage and TLR4/MyD88 signaling. TLR4 might be crucial for PM to initiate pulmonary lesion and for RUS to exert efficacy against PM-induced lung injury.

Sequential SEM-EDS, PLM, and MRS Microanalysis of Individual Atmospheric Particles: A Useful Tool for Assigning Emission Sources

In this work, the particulate matter (PM) from three different monitoring stations in the Monterrey Metropolitan Area in Mexico were investigated for their compositional, morphological, and optical properties. The main aim of the research was to decipher the different sources of the particles. The methodology involved the ex situ sequential analysis of individual particles by three analytical techniques: scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), polarized light microscopy (PLM), and micro-Raman spectroscopy (MRS). The microanalysis was performed on samples of total suspended particles. Different morphologies were observed for particles rich in the same element, including prismatic, spherical, spheroidal, and irregular morphologies. The sequential microanalysis by SEM-EDS/PLM/MRS revealed that Fe-rich particles with spherical and irregular morphologies were derived from anthopogenic sources, such as emissions from the metallurgical industry and the wear of automobile parts, respectively. In contrast, Fe-rich particles with prismatic morphologies were associated with natural sources. In relation to carbon (C), the methodology was able to distinguish between the C-rich particles that came from different anthopogenic sources—such as the burning of fossil fuels, biomass, or charcoal—and the metallurgical industry. The optical properties of the Si-rich particles depended, to a greater extent, on their chemical composition than on their morphology, which made it possible to quickly and accurately differentiate aluminosilicates from quartz. The methodology demonstrated in this study was useful for performing the speciation of the particles rich in different elements. This differentiation helped to assign their possible emission sources.

Assessment of metals in PM10 filters and Araucaria heterophylla needles in two areas of Quito, Ecuador

The reliability of Araucaria heterophylla needles as a biomonitor was evaluated by analyzing the concentration of metals in PM₁₀ filters and in Araucaria heterophylla needles. The sampling campaign was carried out at two sites in the city of Quito, Ecuador, in 2017–2019. Concentrations of Cr, Cu, K, Mn, Pb, Zn, Ca, Fe, Al and Mg were determined in PM₁₀ filters and in Araucaria heterophylla needles using an Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES). The annual mean concentrations of PM₁₀ ranged between 24.9 and 26.3 μg m⁻³, exceeding the limit established by the World Health Organization (20 μg m⁻³). Statistical analyses, performed for the PM₁₀ filters, showed that dust resuspension and anthropogenic activities were important sources for PM₁₀ emissions in the city. Metals related to natural emissions (Ca, Mg, K, Al and Fe) dominated in both types of samples, while the minor metals were those related to anthropogenic emissions (Zn, Cu, Cr and Pb). The former were positively associated with the needle samples, while the latter were associated with PM₁₀ filters. This work not only improved scientific knowledge on the concentrations of PM₁₀ and metals in the Andean city of Quito, but also greatly contributed to the progress of research on the use of Araucaria heterophylla needles as a biomonitor.

Considerations and Influencing Parameters in EDS Microanalysis of Biogenic Hydroxyapatite

Calcium phosphates (CPs) used as biomaterials have been intensively studied in recent years. In most studies, the determination of the chemical composition is mandatory. Due to the versatility and possibilities of performing qualitative and quantitative compositional analyses, energy dispersive spectrometry (EDS) is a widely used technique in this regard. The range of calcium phosphates is very diverse, the first method of approximating the type of compound being EDS microanalysis, by assessing the atomic Ca/P ratio. The value of this ratio can be influenced by several factors correlated with instrumental parameters and analysed samples. This article highlights the influence of the electron beam acceleration voltage (1 kV-30 kV) and of the particle size of calcium phosphate powders on the EDS analysis results. The characterised powders were obtained from bovine bones heat-treated at 1200 °C for 2 h, which have been ground and granulometrically sorted by mechanical vibration. The granulometric sorting generated three types of samples, with particle sizes < 20 μm, < 40 μm and < 100 μm, respectively. These were morphologically and dimensionally analysed by scanning electron microscopy (SEM) and compositionally by EDS, after the spectrometer was calibrated with a standard reference material (SRM) from NIST (National Institute of Standards and Technology). The results showed that the adjusting of acceleration voltage and of the powder particle size significantly influences the spectrum profile and the results of EDS analyses, which can lead to an erroneous primary identification of the analysed calcium phosphate type.

PM10 spatial distribution and metals speciation study in the Bilbao metropolitan area during the 2017-2018 period

Speciation of respirable particles is becoming increasingly important from an epidemiological and analytical point of view to determine the potential effects of air pollution on human health. For this reason, current laws and analytical sampling methods focus on particle size, as it turns out to be the main factor for the greater or lesser penetration into the airways. In this sense, particles of less than 10 μm in diameter (<10 μm), referred to as PM₁₀, are the particles that have a higher capacity for access to the respiratory tract and, therefore, more significant effect on them. In this sense, one of the most important factors that have a key role in the PM₁₀ atmospheric pollution effect is the dispersion effect with the direct influence of natural effects such as wind, rain, topography apart from others. In this work, PM₁₀ data extracted from the Basque Government environmental stations (19 sampling points) in the Biscay province (Basque Country, north of Spain) were combined with the results obtained from the use of self-made passive samplers (SMPS) in the same sampling points areas and subsequently, the sample analysis with a non-invasive elemental technique (Scanning Electron Microscope coupled to Energy Dispersive X-ray Spectrometry) was carried out. Thanks to this methodology, it was possible to determine a wide variety of metals in PM₁₀ such as Al, Fe, Cr, Ni, Pb, Zn, Ti, etc. Most of them present as oxides and others as part of natural aggregations such as quartz, aluminosilicates, phosphates etc.

Seasonal variations in PM10 inorganic composition in the Andean city

Particulate matter (PM) is one of the key pollutants causing health risks worldwide. While the preoccupation for increased concentrations of these particles mainly depends on their sources and thus chemical composition, some regions are yet not well investigated. In this work the composition of chemical elements of atmospheric PM₁₀ (particles with aerodynamic diameters ≤ 10 µm), collected at the urban and suburban sites in high elevation tropical city, were chemically analysed during the dry and wet seasons of 2017-2018. A large fraction (~ 68%) of PM₁₀ composition in Quito, Ecuador is accounted for by water-soluble ions and 16 elements analysed using UV/VIS spectrophotometer and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). Hierarchical clustering analysis was performed to study a correlation between the chemical composition of urban pollution and meteorological parameters. The suburban area displays an increase in PM₁₀ concentrations and natural elemental markers during the dry (increased wind intensity, resuspension of soil dust) season. Meanwhile, densely urbanized area shows increased total PM₁₀ concentrations and anthropogenic elemental markers during the wet season, which may point to the worsened combustion and traffic conditions. This might indicate the prevalence of cardiovascular and respiratory problems in motorized areas of the cities in the developing world.

Spatial and Temporal Distribution of PM2.5 Pollution over Northeastern Mexico: Application of MERRA-2 Reanalysis Datasets

Aerosol and meteorological remote sensing data could be used to assess the distribution of urban and regional fine particulate matter (PM2.5), especially in locations where there are few or no ground-based observations, such as Latin America. The objective of this study is to evaluate the ability of Modern-Era Retrospective Analysis for Research and Application, version 2 (MERRA-2) aerosol components to represent PM2.5 ground concentrations and to develop and validate an ensemble neural network (ENN) model that uses MERRA-2 aerosol and meteorology products to estimate the monthly average of PM2.5 ground concentrations in the Monterrey Metropolitan Area (MMA), which is the main urban area in Northeastern Mexico (NEM). The project involves the application of the ENN model to a regional domain that includes not only the MMA but also other municipalities in NEM in the period from January 2010 to December 2014. Aerosol optical depth (AOD), temperature, relative humidity, dust PM2.5, sea salt PM2.5, black carbon (BC), organic carbon (OC), and sulfate (SO42−) reanalysis data were identified as factors that significantly influenced PM2.5 concentrations. The ENN estimated a PM2.5 monthly mean of 25.62 μg m−3 during the entire period. The results of the comparison between the ENN and ground measurements were as follows: correlation coefficient R ~ 0.90; root mean square error = 1.81 μg m−3; mean absolute error = 1.31 μg m−3. Overall, the PM2.5 levels were higher in winter and spring. The highest PM2.5 levels were located in the MMA, which is the major source of air pollution throughout this area. The estimated data indicated that PM2.5 was not distributed uniformly throughout the region but varied both spatially and temporally. These results led to the conclusion that the magnitude of air pollution varies among seasons and regions, and it is correlated with meteorological factors. The methodology developed in this study could be used to identify new monitoring sites and address information gaps.

Environmental Levels, Sources, and Cancer Risk Assessment of PAHs Associated with PM2.5 and TSP in Monterrey Metropolitan Area

In this work, the content of polycyclic aromatic hydrocarbons (PAHs) in total suspended particles and particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM_2.5) was analyzed using gas chromatography-mass spectrometry. In addition, a sequential chemical analysis of C-rich particles was performed through the parallel coupling of micro-Raman spectroscopy and scanning electron microscopy with X-ray scattering detection. Samples were collected at four sites in the Monterrey metropolitan area, Mexico. A total of 13 PAHs were quantified; indeno(1,2,3-cd)pyrene, chrysene, and benzo(a)anthracene were the most abundant. The total PAH concentrations at the four sampling sites ranged from 1.34 to 8.76 μg/m³. The diagnostic relation of the PAHs indicates that these compounds were emitted by the burning of gasoline and diesel and by the burning of charcoal and biomass. The sequential analysis correlated the morphology and the elemental/molecular composition of the C-rich particles, associated with the PAHs, with their possible emission sources. The estimated lifetime excess cancer risk for inhalation was higher than that established by the World Health Organization, which clearly makes this a potential health risk for the population.

Monitoring human genotoxicity risk associated to urban and industrial Buenos Aires air pollution exposure

The quality of life in large megacities is directly affected by its air quality. In urban environments, suspended particles from anthropogenic origin is one of the main air contaminants identified as highly genotoxic, mutagenic, or carcinogenic. Atmospheric monitoring is therefore imperative, and bioassays to detect the effects of genotoxic agents give usually excellent results. Analysis of micronucleus (MN) in exfoliated oral mucosa cells is a sensitive non-invasive method for monitoring genetic damage in human populations. The first aim of this study was to analyze and characterize levels of volatile organic compounds (VOCs), particulate matter (PM), and polycyclic aromatic hydrocarbons (PAHs) in two areas from Buenos Aires: La Plata city, an urban (U) area and Ensenada, an industrial (I) area. Secondly, we evaluated the possible health risk of its inhabitants through a simple genotoxic assay on exfoliated oral mucosa cells. Whole blood cell count and nuclear abnormalities frequencies were evaluated in the exfoliated oral mucosa cells from urban and industrial inhabitants. Smoking habit represented a significant factor increasing MN percentage while, age did not increase the production of any of the nuclear aberrations assayed (micronuclei, binucleated, karyorrhexis) when the inhabitants from the urban and the industrial areas were compared. In addition, changes in MN and binucleated cell percentages in males and females were found to be area-dependent. We suggest that regardless PM concentration, PM-specific characteristics (size, shape, chemical elements, etc.) and VOCs levels could be responsible for the different harmful genotoxic effects seen in the two areas. Although this is a preliminary study, our results allowed to recognize that individuals living in both the urban and the industrial areas could be considered susceptible groups and should periodically undergo biological monitoring and appropriate care.

Characterization of atmospheric aerosol (PM10 and PM2.5) from a medium sized city in São Paulo state, Brazil

Air pollution causes deleterious effects on human health with aerosols being among the most polluting agents. The objective of this work is the characterization of the PM_2.5 and PM₁₀ aerosol mass in the atmosphere. The methods of analysis include WD-XRF and EDS. Data were correlated with meteorological information and air mass trajectories (model HYSPLIT) by multivariate analysis. A morphological structural analysis was also carried out to identify the probable sources of atmospheric aerosols in the city of São José do Rio Preto, Brazil. The mean mass concentration values obtained were 24.54 μg/m³ for PM₁₀, above the WHO annual standard value of 20 μg/m³ and 10.88 μg/m³ for PM_2.5 whose WHO recommended limit is 10 μg/m³. WD-XRF analysis of the samples revealed Si and Al as major components of the coarse fraction. In the fine fraction, the major elements were Al and S. The SEM-FEG characterization allowed identifying the morphology of the particles in agglomerates, ellipsoids and filaments in the PM₁₀, besides spherical in the PM_2.5. The analysis by EDS corroborated WD-XRF results, identifying the crustal elements, aluminosilicates and elements of anthropogenic origin in the coarse fraction. For the fine fraction crustal elements were also identified; aluminosilicates, black carbon and spherical particles (C and O) originating from combustion processes were predominant. The use of multivariate analysis to correlate air mass trajectories with the results of the morpho-structural characterization of the particulate matter allowed confirmation of the complex composition of the particles resulting from the combination of both local and long-distance sources.

Trace Metal Content and Health Risk Assessment of PM10 in an Urban Environment of León, Mexico

Trace metal concentrations in PM10 were measured in an urban–industrial site in León, Mexico in three different seasons. PM10 were collected in quartz fiber filters of 47 mm diameter using low volume equipment operating with a controlled flow of 5 L min−1 over 24 h. Mass concentrations were gravimetrically determined and it was found that PM10 samples showed values in excess of the Mexican standard and the established values by WHO during cold dry and warm dry seasons. Morphology of selected particles was studied by SEM-EDS analysis, and the elemental composition was determined. Collected samples were analyzed by atomic absorption spectrometry in order to quantify ambient air concentrations of some trace metals (Cu, Co, Zn, Cd, Fe, Mg, and Mn). Median concentrations of trace metals showed the maximum value for iron (3.079 μgm−3) and the minimum value for Cd (0.050 μgm−3) over the entire period. From the meteorological analysis, it was found that sources located SW and ESE of the sampling site contributed to the levels of trace metals in PM10 in the studied site. The health risk assessment found that the population of León is at increased lifetime risk of experiencing cancer because of exposure to these concentrations of PM10 and their trace metal content.

Physicochemical and morphological characterization of atmospheric coarse particles by SEM/EDS in new urban central districts of a megacity

Physicochemical and morphological characteristics of atmospheric particles in new urban centers of fast-developing megacities are not well understood. In this study, atmospheric coarse particles (PM_2.5-10) were simultaneously collected in multiple stations (10) in new urban centers, namely Beylikduzu, Buyukcekmece, and Esenyurt, of Istanbul using a modified passive particulate sampling method. Scanning electron microscope and energy dispersive X-photon spectroscopy (SEM-EDS) was used to investigate the size distribution characteristics, chemical composition and their weight percent abundances, and morphological properties of the collected particles. The particle clusters were mainly dominated by Ca-rich Al silicates, Ca dominant, Ca- and S-rich, and NaCl particles, respectively. Their potential sources were assigned to the natural sources (e.g., wind erosion, soil resuspension, and sea sprays) and anthropogenic activities (construction, transportation, mining and crushing, and cement production). In addition to the major contributions (up to 47% of particle number abundance), the minor contribution clusters (less than 1%) with transitional metals rich particles (Fe, Zn, and Cu rich) mainly from anthropogenic sources (combustion, traffic, and vehicular emissions) were identified. The typical size range (> 0.65 to < 11.00 μm) distribution of the major particle clusters fits a left-skewed modal distribution with a peak at 1.10-2.30-μm size range. However, the number of particles decreases significantly with increasing distance to the source, and this justification is stronger for larger size fractions (> 2.3 μm). Particle numbers and varieties indicated significant spatial variations depending upon the identified sources, meteorological factors, and temporal conditions. In general, the results of this study suggest that the passive sampling of PM_2.5-10 coupled with SEM/EDS based single-particle analysis is an effective tool to understand the physicochemical characterization and spatial and temporal variations of atmospheric particles in urban environments.

Composition and origin of PM2.5 in Mediterranean Countryside

In this work PM_2.5 was collected during winter and summer in a Sardinian village (Gonnostramatza, Italy) highly affected by biomass burning emissions. A multi-technique approach was adopted for the complete PM chemical characterization. The bulk characterization was performed by IC (Ion Chromatography), HPAEC (High-Performance Anion-Exchange Chromatography), TOT (Thermal Optical Transmittance) and ED-XRF (Energy-Dispersive X-Ray Fluorescence) while XPS (X-ray Photoelectron Spectroscopy) was used for the surface characterization. Using levoglucosan as specific tracer of biomass burning emissions, the assessment of the impact of this source was carried out and it represent the major PM source at the investigate site during winter. In winter the average levoglucosan concentration is 2096 ± 324 ng/m³ while during summer its concentration is negligible (18 ± 7 ng/m³). Levoglucosan content in PM_2.5 during winter is on average 13.7%; it is estimated that 65% of PM_2.5 is due to wood burning. XPS has been exploited in this work aiming at highlighting possible differences between surface and bulk composition of PM_2.5. The surface of the particulate matter resulted enriched in carbon compared to the bulk. Among the components of XPS C1s signals recorded on the samples collected during winter, it was found that the signal at 286.5 eV, which is due to the presence of COH, reflects the bulk composition of levoglucosan.