Source apportionment of PM10 and PM2.5 in major urban Greek agglomerations using a hybrid source-receptor modeling process

Insights about the Sources of PM2.5 in an Urban Area from Measurements of a Low-Cost Sensor Network

PM2.5 measurements using a network of lost-cost sensors were conducted during 2017–2019 in the greater area of Patras, Greece. The average PM2.5 concentration in all sites during the study period was 9.4 μg m−3, varying from 6.2 μg m−3 in the background areas to 12.8 μg m−3 at the city center. The site with the peak PM2.5 levels was not located in an area with high traffic density but rather in a square with pedestrian-only zones and a high restaurant density. The highest PM2.5 concentrations were observed during the colder period (November–March) due to high emissions from residential wood burning for heating purposes. The measurements of the sensors were used to estimate the importance of regional and local PM2.5 sources. During the warm period, regional transport dominated, contributing approximately 80–85% of the PM2.5 in the city center; however, during the colder period, the local sources were responsible for approximately half the PM2.5. The network operated reliably during this multiyear study. Such measurements provide, at a very low cost, valuable insights not only about the temporal and spatial variability of PM2.5 in a city but also about its sources, including the role of regional transport.

Multi-city comparative PM2.5 source apportionment for fifteen sites in Europe: The ICARUS project

PM_2.5 is an air pollution metric widely used to assess air quality, with the European Union having set targets for reduction in PM_2.5 levels and population exposure. A major challenge for the scientific community is to identify, quantify and characterize the sources of atmospheric particles in the aspect of proposing effective control strategies. In the frame of ICARUS EU2020 project, a comprehensive database including PM_2.5 concentration and chemical composition (ions, metals, organic/elemental carbon, Polycyclic Aromatic Hydrocarbons) from three sites (traffic, urban background, rural) of five European cities (Athens, Brno, Ljubljana, Madrid, Thessaloniki) was created. The common and synchronous sampling (two seasons involved) and analysis procedure offered the prospect of a harmonized Positive Matrix Factorization model approach, with the scope of identifying the similarities and differences of PM_2.5 key-source chemical fingerprints across the sampling sites. The results indicated that the average contribution of traffic exhausts to PM_2.5 concentration was 23.3% (traffic sites), 13.3% (urban background sites) and 8.8% (rural sites). The average contribution of traffic non-exhausts was 12.6% (traffic), 13.5% (urban background) and 6.1% (rural sites). The contribution of fuel oil combustion was 3.8% at traffic, 11.6% at urban background and 18.7% at rural sites. Biomass burning contribution was 22% at traffic sites, 30% at urban background sites and 28% at rural sites. Regarding soil dust, the average contribution was 5% and 8% at traffic and urban background sites respectively and 16% at rural sites. Sea salt contribution was low (1-4%) while secondary aerosols corresponded to the 16-34% of PM_2.5. The homogeneity of the chemical profiles as well as their relationship with prevailing meteorological parameters were investigated. The results showed that fuel oil combustion, traffic non-exhausts and soil dust profiles are considered as dissimilar while biomass burning, sea salt and traffic exhaust can be characterized as relatively homogenous among the sites.

Characterization of PM2.5 sources in a Belgrade suburban area: a multi-scale receptor-oriented approach

Designated as the most harmful for health, PM_2.5 aerosol fraction was a subject of our study. It was collected for all four seasons during 2014/15 in the suburban area of Belgrade (Serbia) and analysed for Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, As, Ba and Pb elements and for NH₄⁺, NO₃^- and SO₄^2- ions by particle-induced X-ray emission and ion chromatography techniques, respectively. Obtained concentrations have been treated by a combination of several receptor-oriented models to reveal source contributions to the suburban PM_2.5 at different spatial scales. Applied positive matrix factorization analysis indicated five main groups of emission sources: biomass burning (14.5%), traffic (3.9%), regional combustion/secondary sulphates (28.8%), local combustion/secondary nitrates (29.7%) and soil (5.4%). Local heating units had been pointed out as dominant contributors by long-range transport and ground-wind circulation analyses. Air masses circulating over the Balkan Peninsula denoted regional emissions as responsible for the high concentrations of secondary sulphates. Local and long-range transport analyses combined suggested that the BB and the LC/NO₃ originated from the wider urban area. Several Saharan dust episodes were detected as well. Presented results might be a basis for the development of air pollution mitigation strategies in the continental Balkan area, considered one of the most polluted and under-investigated European regions.

Morphological and geochemical characterization of the particulate deposits and the black crust from the Triumphal Arch of Galerius in Thessaloniki, Greece: Implications for deterioration assessment

In the present study, 12 particulate deposits and one black crust sample were collected from the Triumphal Arch of Galerius in Thessaloniki, Greece and characterized by employing a multi-analytical approach including chemical analysis of trace elements and ionic species, as well as scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDS) to gain information about the micromorphology and the chemical composition in terms of major elements. In addition, one unaltered marble sample, e.g. the marble directly beneath the black crust, was examined by microscopic and isotopic methods to characterize its texture and origin. The particulate deposits consist mainly of calcite, quartz, aluminosilicate mineral phases, several metal oxides of Fe, Ti and FeCr with Mn and Cu. They also include bird droppings enriched in P and S, and plant residuals. The black crust has a similar mineral composition and is dominated by calcite with traces of quartz and halite, whereas P- and S-enriched particles are common. In both cases a coating on calcite crystals with a thin crust rich in Ca, Ba and S is commonly observed and is attributed to the previous conservation works. Concentrations of As, Zn, Pb, Cu, nitrate, sulfate, chloride and acetate were significantly higher in particle deposits than in the black crust as opposed to Fe, Co, Ni and formates that were at the same level. The traffic-related trace elements Pb, Zn and Cu and most ions were significantly higher in low-altitude deposition samples. The current marble deterioration is induced by a combination of factors, including mechanical, physico-chemical and biological processes.

Metal(loid) and isotopic tracing of Pb in soils, road and house dusts from the industrial area of Volos (central Greece)

This study examines the metal(loid) contents (As, Cd, Cr, Cu, Mn, Ni, Pb, Sb, Tl and Zn) and Pb isotopes in different environmental compartments (soil, road dust, house dust) from the industrial vicinity of Volos, central Greece. The area surrounding two steel factories, a cement plant, an industrial area and the city core were considered as potential hot spots of metal(loid) contamination. Significant anthropogenic enrichments of Cd, Pb and Zn in relation to local baseline were identified for the soil (median Enrichment Factors of 7, 15 and 8, respectively) and road dusts around the steel factory located at Velestino area. The high contents of As, Sb and Tl in the soil and road dust around the cement plant are attributed to natural sources of contamination associated with adjacent mineralization. The soil samples in the city core exhibited moderate enrichments with respect to typical tracers (Pb, Zn) of anthropogenic contamination in urban areas. Anthropogenic influences in terms of metal(loid) concentrations were more pronounced for the road and house dust material. The Pb isotopic ratios of soil (²⁰⁶Pb/²⁰⁷Pb = 1.154 to 1.194), road dust (²⁰⁶Pb/²⁰⁷Pb = 1.144 to 1.174) and house dust (²⁰⁶Pb/²⁰⁷Pb = 1.129 to 1.171) were between those of the local bedrock and anthropogenic Pb sources. Industrial Pb from the steel plant was the predominant anthropogenic Pb source with relative contributions of ~49% for the soil, ~42% for the road dust and ~44% for the house dust samples. For the road and house dust material, the geochemical signature obtained from Pb isotopic compositions and elemental ratios suggests additional contributors from vehicular emissions. The results of this study demonstrate the suitability of soil to trace natural and anthropogenic impacts in industrial areas and the sensitivity of the road and house dust material to record anthropogenic (industrial and vehicular-derived) contamination in such environments.

Estimated health impacts from maritime transport in the Mediterranean region and benefits from the use of cleaner fuels

Ship traffic emissions degrade air quality in coastal areas and contribute to climate impacts globally. The estimated health burden of exposure to shipping emissions in coastal areas may inform policy makers as they seek to reduce exposure and associated potential health impacts. This work estimates the PM2.5-attributable impacts in the form of premature mortality and cardiovascular and respiratory hospital admissions, from long-term exposure to shipping emissions. Health impact assessment (HIA) was performed in 8 Mediterranean coastal cities, using a baseline conditions from the literature and a policy case accounting for the MARPOL Annex VI rules requiring cleaner fuels in 2020. Input data were (a) shipping contributions to ambient PM2.5 concentrations based on receptor modelling studies found in the literature, (b) population and health incidence data from national statistical registries, and (c) geographically-relevant concentration-response functions from the literature. Long-term exposure to ship-sourced PM2.5 accounted for 430 (95% CI: 220-650) premature deaths per year, in the 8 cities, distributed between groups of cities: Barcelona and Athens, with >100 premature deaths/year, and Nicosia, Brindisi, Genoa, Venice, Msida and Melilla, with tens of premature deaths/year. The more stringent standards in 2020 would reduce the number of PM2.5-attributable premature deaths by 15% on average. HIA provided a comparative assessment of the health burden of shipping emissions across Mediterranean coastal cities, which may provide decision support for urban planning with a special focus on harbour areas, and in view of the reduction in sulphur content of marine fuels due to MARPOL Annex VI in 2020.

Investigating the plausibility of a PMF source apportionment solution derived using a small dataset: A case study from a receptor in a rural site in Apulia - South East Italy

Results of a methodological study on the use of Positive Matrix Factorization (PMF) with smaller datasets are being reported in this work. This study is based on 29 PM₁₀ and 33 PM_2.5 samples from a receptor in a rural setup in Apulia (Southern Italy). Running PMF on the two size fractions separately resulted in the model not functioning correctly. We therefore, augmented the size of the dataset by aggregating the PM₁₀ and PM_2.5 data. The 5-factor solution obtained for the aggregated data was fairly rotationally stable, and was further refined by the rotational tools included in USEPA PMF version 5. These refinements include the imposition of constraints on the solution, based on our knowledge of the chemical composition of the aerosol sources affecting the receptor. Additionally, the uncertainties associated with this solution were fully characterised using the improved error estimation techniques in this version of PMF. Five factors in all, were isolated by PMF: ammonium sulfate, marine aerosol, mixed carbonaceous aerosol, crustal/Saharan dust and total traffic. The results obtained by PMF were further tested inter alia, by comparing them to those obtained by two other receptor modelling techniques: Constrained Weighted Non-negative Matrix Factorization (CW - NMF) and Chemical Mass Balance (CMB). The results of these tests suggest that the solution obtained by PMF, is valid, indicating that for this particular airshed PMF managed to extract most of the information about the aerosol sources affecting the receptor - even from a dataset with a limited number of samples.

Identification of diverse air pollution sources in a complex urban area of Croatia

Pinpointing the contribution of sources in complex urban areas, affected by large point sources such as oil refineries, is important for developing emission control strategies. Receptor models based on the chemical composition of particulate matter (PM), such as chemical mass balance (CMB) and positive matrix factorization (PMF), are useful means for source apportionment, but the inclusion of other gaseous pollutants need further consideration. The results of the multipollutant analyses using temporal variations in pollutant concentrations, chemical PM speciation and receptor modeling, PMF and conditional bivariate polar plots (CBPF), were used for determination of major pollutant sources of fine particulate matter (PM_2.5) and less represented pollutants - hydrogen sulfide (H₂S), nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) in an urban area in Slavonski Brod, Croatia influenced by a large point source (an oil refinery) in Brod, Bosnia and Herzegovina. It is found that the composition of PM_2.5 is dominated by carbonaceous combustion particles, mainly organic carbon (OC), with maximum values appearing during winter. Summer PM_2.5 levels were dominated by sulfate and ammonium, which can be related to the industrial activities i.e., oil refinery. According to PMF analysis, the majority of OC is coming from biomass burning with ∼50% contribution to observed species concentration followed by ∼30% from industry/refinery and ∼10% from traffic. CPBF model showed that urban and highway traffic was the main source of NO₂ concentrations while oil refinery was identified as the dominant source of SO₂ and H₂S. The CBPF receptor model combines concentrations of pollutants and meteorological parameters and emerged as a reliable complementary tool for the identification of sources for considered gaseous pollutants. Limitations of the CBPF method are in the application in stable atmospheric boundary layer conditions (SABL) as wind direction is not representative. Also, larger uncertainty is related to the representation of peak concentrations transported with higher wind speeds (>8  m/s) due to the lower number of events. This work uses various source apportionment methods in the assessment of PM but also for gaseous pollutants, such as NO₂, SO₂ and H₂S that are less represented in the source apportionment studies and can be used for future scientific applications to assure more efficient air quality management.

Using multi-site data to apportion PM-bound metal(loid)s: Impact of a manganese alloy plant in an urban area

The identification and quantification of the PM emission sources influencing a specific area is vital to better assess the potential health effects related to the PM exposure of the local population. In this work, a multi-site PM₁₀ sampling campaign was performed in seven sites located in the southern part of the Santander Bay (northern Spain), an urban area characterized by the proximity of some metal(loid) industrial sources (mainly a manganese alloy plant). The total content of V, Mn, Fe, Ni, Cu, Zn, As, Mo, Cd, Sb and Pb was determined by ICP-MS. This multi-site dataset was evaluated by positive matrix factorization (PMF) in order to identify the main anthropogenic metal(loid) sources impacting the studied area, and to quantify their contribution to the measured metal(loid) levels. The attribution of the sources was done by comparing the factor profiles obtained by the PMF analysis with representative profiles from known metal(loid) sources in the area, included in both the European database SPECIEUROPE (V2.0) and the US database EPA-SPECIATE (V4.5) or calculated from literature data. In addition, conditional bivariate probability functions (CBPF)s were used to assist in the identification of the sources. Four metal(loid) sources were identified: Fugitive and point source emissions from the manganese alloy plant (49.9% and 9.9%, respectively), non-exhaust traffic emissions (38.3%) and a minor source of mixed origin (1.8%). The PMF analysis was able to make a clear separation between two different sources from the manganese alloy plant, which represented almost 60% of the total measured metal(loid) levels, >80% of these emissions being assigned to fugitive emissions. These results will be useful for the assessment of the health risk associated with PM₁₀-bound metal(loid) exposure and for the design of efficient abatement strategies in areas impacted by similar industries.

PM2.5 source apportionment for the port city of Thessaloniki, Greece

This paper aims to identify the chemical fingerprints of potential PM2.5 sources and estimate their contribution to Thessaloniki port-city's air quality. For this scope, Positive Matrix Factorization model was applied on a comprehensive PM2.5 dataset collected over a one-year period, at two sampling sites: the port and the city center. The model indicated six and five (groups of) sources contributing to particle concentration at the two sites, respectively. Traffic and biomass burning (winter months) comprise the major local PM sources for Thessaloniki (their combined contribution can exceed 70%), revealing two of the major control-demanding problems of the city. Shipping and in-port emissions have a non-negligible impact (average contribution to PM2.5: 9-13%) on both primary and secondary particles. Road dust factor presents different profile and contribution at the two sites (19.7% at the port; 7.4% at the city center). The secondary-particle factor represents not only the aerosol transportation over relatively long distances, but also a part of traffic-related pollution (14% at the port; 34% at the city center). The study aims to contribute to the principal role of quantitative information on emission sources (source apportionment) in port-cities for the implementation of the air quality directives and guidelines for public health.

Chemical characteristics of airborne particles in Xi'an, inland China during dust storm episodes: Implications for heterogeneous formation of ammonium nitrate and enhancement of N-deposition

To identify the sources and heterogeneous reactions of sulfate and nitrate with dust in the atmosphere, airborne particles in Xi'an, inland China during the spring of 2017 were collected and measured for chemical compositions, along with a laboratory simulation of the heterogeneous formation of ammonium nitrate on the dust surface. Our results showed that concentrations of Ca²⁺, Na⁺ and Cl^- in the TSP samples were enhanced in the dust events, with the values of 41.8, 5.4 and 4.0 μg m^-3, respectively, while NO₃^- (7.1 μg m^-3) and NH₄⁺ (2.4 μg m^-3) remarkably decreased, compared to those in the non-dust periods. During the dust events, NH₄⁺ correlated only with NO₃^- (R² = 0.52) and abundantly occurred in the coarse mode (>2.1 μm), in contrast to that in the non-dust periods, which well correlated with sulfate and nitrate and enriched in the fine mode (<2.1 μm). SO₄^2- in Xi'an during the dust events existed mostly as gypsum (CaSO₄·2H₂O) and mirabilite (Na₂SO₄·10H₂O) and dominated in the coarse mode, suggesting that they were directly transported from the upwind Gobi Desert region. Our laboratory simulation results showed that during the long-range transport hygroscopic salts in the Gobi dust such as mirabilite can absorb water vapor and form a liquid phase on the particle surface, then gaseous NH₃ and HNO₃ partition into the aqueous phase and form NH₄NO₃, resulting in the strong correlation of NH₄⁺ with NO₃^- and their accumulation on dust particles. The dry deposition flux of total inorganic nitrogen (NH₄⁺ + NO₃^-) in Xi'an during the dust events was 0.97 mg-N m^-2 d^-1 and 37% higher than that in the non-dust periods. Such a significant enhanced N-deposition is ascribed to the heterogeneous formation of NH₄NO₃ on the dust particle surface, which has been ignored and should be included in future model simulations.

In vitro cellular toxicity induced by extractable organic fractions of particles exhausted from urban combustion sources - Role of PAHs

The bioactivity of the extractable organic matter (EOM) of particulate matter (PM) exhausted from major urban combustion sources, including residential heating installations (wood-burning fireplace and oil-fired boiler) and vehicular exhaust from gasoline and diesel cars), was investigated in vitro by employing multiple complementary cellular and bacterial assays. Cytotoxic responses were investigated by applying the MTT ((3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide)) bioassay and the lactate dehydrogenase (LDH) release bioassay on human lung cells (MRC-5). Sister Chromatids Exchange (SCE) genotoxicity was measured on human peripheral lymphocytes. Lipid peroxidation potential via reactive oxygen species (ROS) was evaluated on E. coli bacterial cells by measuring the malondialdehyde (MDA) end product. Furthermore, the DNA damage induced by the organic PM fractions was evaluated by the reporter (β-galactosidase) gene expression assay in the bacterial cells, and, by examining the fragmentation of chromosomal DNA on agarose gel electrophoresis. The correlations between the source PM-induced biological endpoints and the PM content in polycyclic aromatic hydrocarbons (PAHs), as typical molecular markers of combustion, were investigated. Fireplace wood smoke particles exhibited by far the highest content in total and carcinogenic PAHs followed by oil boilers, diesel and gasoline emissions. However, in all bioassays, the total EOM-induced toxicity, normalized to PM mass, was highest for diesel cars equipped with Diesel Particle Filter (DPF). No correlation between the toxicological endpoints and the PAHs content was observed suggesting that cytotoxicity and genotoxicity are probably driven by other extractable organic compounds than the commonly measured unsubstituted PAHs. Clearly, further research is needed to elucidate the role of PAHs in the biological effects induced by both, combustion emissions, and ambient air particles.

Chemical Characteristics and Sources of Submicron Particles in a City with Heavy Pollution in China

Submicron particle (PM1) pollution has received increased attention in recent years; however, few studies have focused on such pollution in the city of Shijiazhuang (SJZ), which is one of the most polluted cities in the world. In this study, we conducted an intensive simultaneous sampling of PM1 and PM2.5 in autumn 2016, in order to explore pollution characteristics and sources in SJZ. The results showed that the average mass concentrations of PM1 and PM2.5 were 70.51 μg/m3 and 91.68 μg/m3, respectively, and the average ratio of PM1/PM2.5 was 0.75. Secondary inorganic aerosol (SIA) was the dominant component in PM1 (35.9%) and PM2.5 (32.3%). An analysis of haze episodes found that SIA had a significant influence on PM1 pollution, NH4+ promoted the formation of pollution, and SO42− and NO3− presented different chemical mechanisms. Additionally, the results of source apportionment implied that secondary source, biomass burning and coal combustion, traffic, industry, and dust were the major pollution sources for SJZ, accounting for 45.4%, 18.9%, 15.7%, 10.3%, and 9.8% of PM1, respectively, and for 42.4%, 18.8%, 12.2%, 10.2%, and 16.4% of PM2.5, respectively. Southern Hebei, mid-eastern Shanxi, and northern Henan were the major contribution regions during the study period. Three transport pathways of pollutants were put forward, including airflows from Shanxi with secondary source, airflows from the central Beijng–Tianjin–Hebei region with fossil fuel burning source, and airflows from the southern North China Plain with biomass burning source. The systematic analysis of PM1 could provide scientific support for the creation of an air pollution mitigation policy in SJZ and similar regions.