Ambient air quality in the holy city of Makkah: A source apportionment with elemental enrichment factors (EFs) and factor analysis (PMF)

Air pollution we breathe: Assessing the air quality and human health impact in a megacity of Southeast Asia

With 24 million inhabitants and 6.6 million vehicles on the roads, Karachi, Pakistan ranks among the world's most polluted cities due to high levels of fine particulate matter (PM2.5). This study aims to investigate PM2.5 mass, seasonal and temporal variability, chemical characterization, source apportionment, and health risk assessment at two urban sites in Karachi. Samples were analyzed using ion chromatography and dual-wavelength optical transmissometer for various inorganic components (anions, cations, and trace elements) and black carbon (BC). Several PM2.5 pollution episodes were frequently observed, with annual mean concentrations at Kemari (140 ± 179 μg/m3) and Malir (95 ± 40.9 μg/m3) being significantly above the World Health Organization's guidelines of 5 μg/m3. Chemical composition at both sites exhibited seasonal variability, with higher pollution levels in winter and fall and lower concentrations in summer. The annual average BC concentrations were 4.86 ± 5.29 μg/m3 and 4.52 ± 3.68 μg/m3, respectively. A Positive Matrix Factorization (PMF) analysis identified 5 factors, crustal, sea salt, vehicular exhaust, fossil-fuel combustion, and industrial emission. The health risk assessment indicated a higher number of deaths in colder seasons (fall and winter) at the Kemari (328,794 and 287,814) and Malir (228,406 and 165,737) sites and potential non-carcinogenic and carcinogenic risks to children from metals. The non-carcinogenic risk of PM2.5 bound Pb, Fe, Zn, Mn, Cr, Cu and Ni via inhalation exposure were within the acceptable level (<1) for adults. However, potential non-carcinogenic and carcinogenic health risk posed by Pb and Cr through inhalation were observed for children. The findings exhibit critical levels of air pollution that exceed the safe limits in Karachi, posing significant health risks to children and sensitive groups. Our study underscores the urgent need for effective emission control strategies and policy interventions to mitigate these air pollution risks.

Pollution characteristics, source apportionment, and health risk assessment of PM10 and PM2.5 in rooftop and kerbside environment of Lanzhou, NW China

To investigate air pollution in the kerbside environment and its associated human health risks, a study was conducted in Lanzhou during December 2018, as well as in April, June, and September 2019. The research aimed to characterize the composition of PM10 and PM2.5, including elements, ions, and carbonaceous components, at both rooftop and kerbside locations. Additionally, source apportionment and health risk assessment were conducted. The results showed that the average mass concentrations of PM10 on the rooftop were 176.01 ± 83.23 μg/m3, and for PM2.5, it was 94.07 ± 64.89 μg/m3. The PM10 and PM2.5 levels at the kerbside are 2.21 times and 1.79 times, respectively, greater than those on the rooftop. Moreover, the concentrations of elements, ions, and carbonaceous components in kerbside PM were higher than those at the rooftop location. Chemical mass closure analysis identified various sources, including organic matter, mineral dust, secondary ions, other ions, elements, and other components. In comparison to rooftop particulate matter (PM), mineral dust makes a more substantial contribution to kerbside PM. Secondary ions show an opposite trend, making a greater contribution to rooftop PM. The contribution of organic components within PM of the same particle size remains relatively consistent. The outcome of the health risk assessment indicates that Co, Cd, and As in PM within the kerbside and rooftop environments do not pose a notable carcinogenic risk. However, Al and Mn do present specific non-carcinogenic risks, particularly in the kerbside environment. Furthermore, children experience elevated non-carcinogenic risk compared to adults. These findings can serve as a scientific foundation for formulating policies within the local health department.

Long-term quantification of springtime aerosols over Saudi Arabia using multi-satellite remotely sensed data

A comprehensive analysis of aerosol characteristics over Saudi Arabia from 2005 to 2022, utilizing high-resolution satellite-based observations and reanalysis datasets, examining the distribution of aerosols and their subtypes across the three dimensions (temporal, spatial, and altitude based) for March, April, and May. This study focuses on the analysis of parameters such as aerosol optical depth (AOD), angstrom exponent (AE), absorption aerosol optical depth (AAOD), and Ultraviolet Aerosol Index (UVAI), revealing significant spatial disparities, with elevated aerosol concentrations in the central and eastern regions and comparatively lower concentrations along the western coastal areas. In this study, the spatial patterns and temporal trends are analyzed through trajectory modeling. The study also investigates the composition of aerosols in various Saudi cities. Aerosols prevailing in a dozen Saudi Arabian cities were systematically categorized into six sub-types, considering their particle size and UV-absorbing properties. Notably, two major aerosol sub-types, absorbing coarse (AC) aerosols (UVAI > 0.25, AE < 0.70) treated as mineral dust and absorbing mixed (AM) aerosols (0.70 < AE < 1.25) along with neutral fine (NF) particles (- 0.5 < UVAI < 0.25, AE > 1.25) treated as urban, predominate across the Kingdom of Saudi Arabia.

Characterization and childhood exposure assessment of toxic heavy metals in household dust under true living conditions from 10 China cities

Health hazards caused by metal exposure in household dust are concerning environmental health problems. Exposure to toxic metals in household dust imposes unclear but solid health risks, especially for children. In this multicenter cross-sectional study, a total of 250 household dust samples were collected from ten stratified cities in China (Panjin, Shijiazhuang, Qingdao, Lanzhou, Luoyang, Ningbo, Xi'an, Wuxi, Mianyang, Shenzhen) between April 2018 and March 2019. Questionnaire was conducted to gather information on individuals' living environment and health status in real-life situations. Multivariate logistic regression and principal component analysis were conducted to identify risk factors and determine the sources of metals in household dust. The median concentration of five metals in household dust from 10 cities ranged from 0.03 to 73.18 μg/g. Among the five heavy metals, only chromium in household dust of Mianyang was observed significantly both higher in the cold season and from the downwind households. Mercury, cadmium, and chromium were higher in the third-tier cities, with levels of 0.08, 0.30 and 97.28 μg/g, respectively. There were two sources with a contribution rate of 38.3 % and 25.8 %, respectively. Potential risk factors for increased metal concentration include long residence time, close to the motorway, decoration within five years, and purchase of new furniture within one year. Under both moderate and high exposure scenarios, chromium showed the highest level of exposure with 6.77 × 10-4 and 2.28 × 10-3 mg·kg-1·d-1, and arsenic imposed the highest lifetime carcinogenic risk at 1.67 × 10-4 and 3.17 × 10-4, respectively. The finding highlighted the priority to minimize childhood exposure of arsenic from household dust.

Sustainable Plasma Gasification Treatment of Plastic Waste: Evaluating Environmental, Economic, and Strategic Dimensions

The conversion of waste to energy is an essential process in the Middle East, especially in Saudi Arabia, where it plays a crucial role in waste management. The annual analysis of the decomposition hazards of the landfills in the city of Makkah showed that they ranged from 168,000 Mg in 1994 to 297,000 Mg in 2022. The emission costs of pollution ranged from 4 million in 1994 to 7 million in 2022. The number of gas emissions of plastic waste accumulating in the analyzed landfill has increased from 128,000 Mg in 1994 to 227,000 Mg in 2022. The thermal plasmas used were produced by air plasma torches, which are an essential part of plasma reactors. The operational characteristics of air plasma torches were investigated at a flow rate of 10-30 g/s, including current-voltage characteristics, applied power, applied flow rate, average temperatures of the exiting plasma jet ranging from 15,000 to 19,000 K, average velocity of the exiting plasma jet (1677.3-2763.2) m/s, wavelength of the emitted radiation ranging from 153 to 193 nm, and the corresponding beam lengths ranging from 400 to 450 mm. The proposed plasma gasification is the greenest method for processing plastic waste in the light of ecological, economic, and strategic visions with an amount of recovered pyrolysis oil in the year 2022 of 3.17 × 105 tons with an equivalent energy of 12.55 × 109 MJ, with an output efficiency value equal to 81%. A roadmap for the economic and environmental visions was introduced, where the economic return on investment (ROR%) was 80%, the payback period (PBP) was 1.2 years, and the gross profit reached 129%.

Temporal and Spatial Variations of Potentially Toxic Elements in PM10 Collected in Jeddah City, Saudi Arabia

Air pollution causes environmental and health problems around the world. In this study, ambient particulate matter with an aerodynamic diameter equal to or less than 10 microns (PM10) has been collected at three different locations in Jeddah city, Saudi Arabia. The locations are characterized by differences in terms of traffic, residential intensity, industrial, and non-road mobile machinery activities. The monthly and annual mass concentration of the PM10 exceeds the recommended annual limit of the World Health Organization (15 µg/m3) and the European air quality standard (40 µg/m3) at the three locations. The collected PM10 samples as well as a certified reference material of atmospheric particulates (NIST 1678a) were digested in aqua regia using microwave digestion. The quantitative elemental analysis was carried out using inductively coupled plasma mass spectrometry. The variations of the elemental concentration in terms of workdays, weekends, seasons, and annual were determined at the three locations. The spatial and temporal elemental variations were found to be different between the three sites, pointing to local influences that should be further evaluated. The concentration of Cd was found to be high and may cause health problems.

Spatial distributions of PM10-bound metal elements in the central part of western Taiwan and their potential emission sources and the carcinogenic health risks

This study aimed to investigate the spatial distribution of metal elements in PM10 and their potential sources and associated health risks over a period of two years in eight locations in the central part of western Taiwan. The study revealed that the mass concentration of PM10 and the total mass concentration of 20 metal elements in PM10 were 39.0 μg m-3 and 4.74 μg m-3, respectively, with total metal elements accounting for approximately 13.0% of PM10. Of the total metal elements, 95.6% were crustal elements (Al, Ca, Fe, K, Mg, and Na), with trace elements (As, Ba, Cd, Cr, Co, Cu, Ga, Mn, Ni, Pb, Sb, Se, V, and Zn) contributing only 4.4%. Spatially, the inland areas exhibited higher PM10 concentrations due to lee-side topography and low wind speeds. In contrast, the coastal regions exhibited higher total metal concentrations because of the dominance of crustal elements from sea salt and crustal soil. Four primary sources of metal elements in PM10 were identified as sea salt (58%), re-suspended dust (32%), vehicle emissions and waste incineration (8%), and industrial emissions and power plants (2%). The positive matrix factorization (PMF) analysis results indicated that natural sources like sea salt and road dust contributed up to 90% of the total metal elements in PM10, while only 10% was attributed to human activities. The excess cancer risks (ECRs) associated with As, Co, and Cr(VI) were greater than 1 × 10-6, and the total ECR was 6.42 × 10-5. Although only 10% of total metal elements in PM10 came from human activities, they contributed to 82% of the total ECR.

Fine particulate matter and its chemical constituents' levels: A troubling environmental and human health situation in Karachi, Pakistan

Like many urban centers in developing countries, the effect of air pollution in Karachi is understudied. The goal of this study was to determine the chemical characterization, temporal and seasonal variability, sources, and health impacts of fine particulate matter (PM_2.5) in Karachi, Pakistan. Daily samples of PM_2.5 were collected using a low-volume air sampler at two different sites (Makro and Karachi University) over the four seasons between October 2009 and August 2010. Samples were analyzed for black carbon (BC), trace metals, and water-soluble ions. Results showed that the annual average concentrations of PM_2.5 at Makro and Karachi University were 114 ± 115 and 71.7 ± 56.4 μg m^-3, respectively, about 22.8 and 14.3-fold higher than the World Health Organization annual guideline of 5 μg m^-3. BC concentrations were 3.39 ± 1.97 and 2.70 ± 2.06 μg m^-3, respectively. The concentrations of PM_2.5, BC, trace metals, and ions at the two sites showed clear seasonal trends, with higher concentrations in winter and lower concentrations in summer. The trace metals and ionic species with the highest concentrations were Pb, S, Zn, Ca, Si, Cl, Fe, and SO₄^2-. The air quality index in the fall and winter at both sites was about 68 %, which is "unhealthy" for the general population. Positive Matrix Factorization revealed the overall contribution to PM_2.5 at the Makro site came from three major sources - industrial emissions (13.3 %), vehicular emissions (59.1 %), and oil combustion (23.3 %). The estimates of expected number of deaths due to short-term exposure to PM_2.5 were high in the fall and winter at both sites, with an annual mean estimate of 3592 expected number of deaths at the Makro site. Attention should be paid to the reduction of inorganic pollutants from industrial facilities, vehicular traffic, and fossil fuel combustion, due to their extremely high contribution to PM_2.5 mass and health risks.

Phytoremediation capability of Typha latifolia L. to uptake sediment toxic elements in the largest coastal wetland of the Persian Gulf

The present study evaluated the status of sediment toxicity and pollution, and the phytoremediation capability of Typha latifolia L. (TlL) within the largest coastal wetland in the southwest of Iran, the Shadegan International Wetland. In eight sampling sites, covering the entire wetland, the concentration of six toxic elements (As, Cr, Cu, Ni, Pb, and Zn) in the surface sediment, root, and stem of TlL were measured. The results indicated that mean concentrations of Cr, Cu, Pb, and Zn were found to be higher than those in the local background, which likely indicates anthropogenic sources of these elements. Due to the presence of a nearby landfill, the results of modified pollution index (MPI) and aggregate toxicity index (ATI) indicated a moderately-heavily polluted level and moderate to high toxic degree, respectively. However, the medium-low level of toxicity toward living of organisms (21 % probability) was detected based on the assessment of the Sediment Quality Guidelines (SGQ). The results of our study indicate that the root and stem tissues of TlL are capable of acting as an indicator of Cu/Pb/Zn and Zn pollution in sediment, respectively. Considering the potential of phytoremediation, TlL represented both phytostabilization and phytoextraction capabilities for Pb and Zn and a significant increase was observed in the phytoremediation capability by increasing the distance from the landfill area. According to the results of the metal accumulation index (MAI) and comprehensive bioconcentration index (CBCI), TlL grown in the study area showed an acceptable performance in the accumulation of multiple toxic elements compared to that in Turkey, India, and Poland. Overall, TlL is a good candidate for the phytoremediation of sediments contaminated by Pb and Zn.

Aerosol Oxidative Potential in the Greater Los Angeles Area: Source Apportionment and Associations with Socioeconomic Position

Oxidative potential (OP) has been proposed as a possible integrated metric for particles smaller than 2.5 μm in diameter (PM_2.5) to evaluate adverse health outcomes associated with particulate air pollution exposure. Here, we investigate how OP depends on sources and chemical composition and how OP varies by land use type and neighborhood socioeconomic position in the Los Angeles area. We measured OH formation (OP^OH), dithiothreitol loss (OP^DTT), black carbon, and 52 metals and elements for 54 total PM_2.5 samples collected in September 2019 and February 2020. The Positive Matrix Factorization source apportionment model identified four sources contributing to volume-normalized OP^OH: vehicular exhaust, brake and tire wear, soil and road dust, and mixed secondary and marine. Exhaust emissions contributed 42% of OP^OH, followed by 21% from brake and tire wear. Similar results were observed for the OP^DTT source apportionment. Furthermore, by linking measured PM_2.5 and OP with census tract level socioeconomic and health outcome data provided by CalEnviroScreen, we found that the most disadvantaged neighborhoods were exposed to both the most toxic particles and the highest particle concentrations. OP^OH exhibited the largest inverse social gradients, followed by OP^DTT and PM_2.5 mass. Finally, OP^OH was the metric most strongly correlated with adverse health outcome indicators.

Seasonal changes and respiratory deposition flux of PM2.5 and PM10 bound metals in Dhaka, Bangladesh

Due to rapid urbanization and fast economic development, aerosol pollution is a serious environmental issue, especially in Bangladesh. Based on bioaccessibility and respiratory deposition doses (RDD), health risks of PM_2.5 and PM₁₀ bound 15 (fifteen) metals were investigated at fourteen urban sites (roadside, marketplace, industrial, and commercial areas). Sampling campaigns were conducted over four seasons (winter, summer, rainy, and autumn) from December 2020 to November 2021. A beta attenuation mass analyzer measured particulate matter concentrations in ambient air. The metals in PM fractions were analyzed by X-ray fluorescence spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS). The airborne trace metals (Cd, As, Zn, Pb, Cr, Cu, Ni) with high enrichment factors indicate anthropogenic sources. The positive matrix factorization (PMF) categorized these elements as originating from automobile exhaust, industrial emissions, and solid waste/coal combustion, whereas the geologic elements came from earth crust/soil dust. During the winter, most of the air mass trajectories arrived from India across the land (82%) and Indo Gangetic Plain (IGP) region to the sampling sites, which may have aided in the transport of pollutants. The deposition flux of metals illustrated that compared to PM_2.5, PM₁₀ deposited a higher amount of metals in the upper airways (81.96%). In comparison, PM_2.5 accumulates more elevated amounts of metals in alveolar regions (11.77%), due to the ability of fine particles to penetrate deeper into the lower pulmonary region. Among age groups, an adult inhales a higher amount of metals than a child, on average 0.103 mg and 0.08 mg of metals per day via PM_2.5, respectively. Acute health impacts are caused by the deposited cancer-causing metals in alveolar tissue, which circulates through the bloodstream and affects several organs. Prolonged exposure to these carcinogenic metals poses significant health risks.

Source apportionment, identification and characterization, and emission inventory of ambient particulate matter in 22 Eastern Mediterranean Region countries: A systematic review and recommendations for good practice

Little is known about the main sources of ambient particulate matter (PM) in the 22 Eastern Mediterranean Region (EMR) countries. We designed this study to systematically review all published and unpublished source apportionment (SA), identification and characterization studies as well as emission inventories in the EMR. Of 440 articles identified, 82 (11 emission inventory ones) met our inclusion criteria for final analyses. Of 22 EMR countries, Iran with 30 articles had the highest number of studies on source specific PM followed by Pakistan (n = 15 articles) and Saudi Arabia (n = 8 papers). By contrast, there were no studies in Afghanistan, Bahrain, Djibouti, Libya, Somalia, Sudan, Syria, Tunisia, United Arab Emirates and Yemen. Approximately 72% of studies (51) were published within a span of 2015-2021.48 studies identified the sources of PM_2.5 and its constituents. Positive matrix factorization (PMF), principal component analysis (PCA) and chemical mass balance (CMB) were the most common approaches to identify the source contributions of ambient PM. Both secondary aerosols and dust, with 12-51% and 8-80% (33% and 30% for all EMR countries, on average) had the greatest contributions in ambient PM_2.5. The remaining sources for ambient PM_2.5, including mixed sources (traffic, industry and residential (TIR)), traffic, industries, biomass burning, and sea salt were in the range of approximately 4-69%, 4-49%, 1-53%, 7-25% and 3-29%, respectively. For PM₁₀, the most dominant source was dust with 7-95% (49% for all EMR countries, on average). The limited number of SA studies in the EMR countries (one study per approximately 9.6 million people) in comparison to Europe and North America (1 study per 4.3 and 2.1 million people respectively) can be augmented by future studies that will provide a better understanding of emission sources in the urban environment.

Mass concentrations and elemental analysis of PM2.5 and PM10 in a coastal Mediterranean site: A holistic approach to identify contributing sources and varying factors

PM₁₀ and PM_2.5 were measured at a suburban coastal Mediterranean site. Daily mass concentrations were generally lower than the WHO air quality limits but showed significant diurnal and seasonal variations, with intensive African dust events and residential heating emissions during wintertime causing the higher % increase of ambient concentrations (32% and 59% respectively). However, analysis of the elemental content revealed intrinsic characteristics. Statistically significant seasonal variability was found for S with higher concentrations during warm seasons directly associated with the formation of secondary sulfates. Increased S was the driving reason for the significant depletion of both Cl and Br. On the other hand, elevated K during wintertime was attributed to biomass burning. Analysis of the mineral content of airborne particles showed that typical soil-derived particles were significantly increased during dust events (Mg, Al, Si, K, Ca, Ti, Mn, Fe) although the corresponding mass concentrations preserved relative low levels (<30 μg m^-3). It was also found that dust events contributed to P, S, V, Zn, Sr and Pb with elemental ratios including Si (Si/Al, Si/Fe, Si/Ca) and Ca/Al serving as good markers for African dust. Heavy metals were found to have both direct and indirect influence on PM_2.5 and PM₁₀. PM_2.5 were primarily enriched with metals produced from motor vehicles (Cu, Zn, Pb) and ships (V, Ni), whilst, PM₁₀ enriched indirectly with Cr, Zn, Br and Pb due to road dust. At the end, source appointment has shown that the dominant contributing factor was mineral dust for both metrics (>30%) but significant contributions arose from secondary sulfates and traffic, (aged) sea salt, biomass burning (only for PM_2.5) and road dust (only for PM₁₀). Overall, this work provides a novel insight on the characteristics and chemical profile of atmospheric particles in a suburban environment largely affected by local, regional and long-range sources.

Analysis and Modeling of Air Pollution in Extreme Meteorological Conditions: A Case Study of Jeddah, the Kingdom of Saudi Arabia

Air pollution has serious environmental and human health-related consequences; however, little work seems to be undertaken to address the harms in Middle Eastern countries, including Saudi Arabia. We installed a continuous air quality monitoring station in Jeddah, Saudi Arabia and monitored several air pollutants and meteorological parameters over a 2-year period (2018–2019). Here, we developed two supervised machine learning models, known as quantile regression models, to analyze the whole distribution of the modeled pollutants, not only the mean values. Two pollutants, namely NO₂ and O₃, were modeled by dividing their concentrations into several quantiles (0.05, 0.25, 0.50, 0.75, and 0.95) and the effect of several pollutants and meteorological variables was analyzed on each quantile. The effect of the explanatory variables changed at different segments of the distribution of NO₂ and O₃ concentrations. For instance, for the modeling of O₃, the coefficients of wind speed at quantiles 0.05, 0.25, 0.5, 0.75, and 0.95 were 1.40, 2.15, 2.34, 2.31, and 1.56, respectively. Correlation coefficients of 0.91 and 0.92 and RMSE values of 14.41 and 8.96, which are calculated for the cross-validated models of NO₂ and O₃, showed an acceptable model performance. Quantile analysis aids in better understanding the behavior of air pollution and how it interacts with the influencing factors.

Particulate Matter (PM2.5) Characterization, Air Quality Level and Origin of Air Masses in an Urban Background in Pretoria

Several sources have been identified as contributing to the concentration of ambient fine particulate matter, which has been associated to a variety of health issues. The chemical characteristics and sources of trace elements in PM_2.5, as well as the air quality index, were investigated in this study. Twenty four-hour fine aerosol particles were collected in an urban area in Pretoria, South Africa, from April 2017 to April 2018. Eighteen trace elements were determined using an XEPOS 5 energy-dispersive X-ray fluorescence (EDXRF) spectrometer, while black and organic carbon were estimated using an optical transmissometer from the samples collected. The HYPLIT model (version 4.9) was used to estimate air mass trajectories. Health risk was calculated by comparing it to the World Health Organization's air quality index (AQI). The overall mean PM_2.5 concentration of the collected sample equals 21 µg/m³. Majority of PM_2.5 exceedances were reported during mid-autumn and winter seasons, as compared to daily WHO guidelines and South African standards. S had the highest concentrations, greater than 1 µg/m³. Ni, Se, Br and Sb showed they were extremely enriched, (EF > 10) and suggestive of anthropogenic or non crustal origin The 24-h PM, soot, BC and OC were significantly different by the geographical origin of air masses (p < 0.05). The AQI showed that 70% of the samples showed levels above the AQI range of good and healthy air. The findings include details on the concentration, composition, and potential sources of fine PM_2.5, which is essential for policy formulation and mitigation strategies in South Africa's fight against air pollution.

Source Apportionment of Atmospheric PM10 in Makkah Saudi Arabia by Modelling Its Ion and Trace Element Contents with Positive Matrix Factorization and Generalised Additive Model

In this paper, the emission sources of PM10 are characterised by analysing its trace elements (TE) and ions contents. PM10 samples were collected for a year (2019−2020) at five sites and analysed. PM10 speciated data were analysed using graphical visualization, correlation analysis, generalised additive model (GAM), and positive matrix factorization (PMF). Annual average PM10 concentrations (µg/m3) were 304.68 ± 155.56 at Aziziyah, 219.59 ± 87.29 at Misfalah, 173.90 ± 103.08 at Abdeyah, 168.81 ± 82.50 at Askan, and 157.60 ± 80.10 at Sanaiyah in Makkah, which exceeded WHO (15 µg/m3), USEPA (50 µg/m3), and the Saudi Arabia national (80 µg/m3) annual air quality standards. A GAM model was developed using PM10 as a response and ions and TEs as predictors. Among the predictors Mg, Ca, Cr, Al, and Pb were highly significant (p < 0.01), Se, Cl, and NO2 were significant (p < 0.05), and PO4 and SO4 were significant (p < 0.1). The model showed R-squared (adj) 0.85 and deviance explained 88.1%. PMF identified four main emission sources of PM10 in Makkah: (1) Road traffic emissions (explained 51% variance); (2) Industrial emissions and mineral dust (explained 27.5% variance); (3) Restaurant and dwelling emissions (explained 13.6% variance); and (4) Fossil fuel combustion (explained 7.9% variance).

Source identification of exhaust and non-exhaust traffic emissions through the elemental carbon fractions and Positive Matrix Factorization method

Our study implies the importance of exhaust and non-exhaust emissions in a highway road tunnel, which is crucial to assess their impacts on air quality, human health, climate and developing functional methods for controlling. The total suspended particulates (TSP) and road dust (RD) samples were collected by PUF samplers and manually sweeping, respectively. Campaigns were performed in the summer and winter of 2014 in a highway road tunnel in Bolu, Turkey. Chemical analyses were presented to characterize the contents of organic carbon (OC) fractions (OC1,2,3,4), elemental carbon (EC) fractions (EC1,2,3,4,5,6), polycyclic aromatic hydrocarbons (PAHs) and metals (Al, Ba, Ca, Cu, Mg, Mn, Pb, Sr, Cr and Fe) in the collected TSP and RD samples. Positive matrix factorization (PMF) and orthogonal (Deming) regression analysis were applied to find out the exhaust and non-exhaust vehicle emissions of metal and carbonaceous species in the tunnel. The results showed that the identified source profiles included resuspended road dust (43%), non-exhaust emissions (37%), diesel exhaust emissions (13%), and gasoline exhaust emissions (7%). The relationship between emission markers of metal species and EC carbon fractions was supported by correlation studies. Among these EC fractions, EC4 and EC2 were the most abundant fractions in aerosol and RD samples, respectively and so they highly represented the diesel and non-exhaust emissions. Besides, the EC1 fraction was the indicator of gasoline-fueled emissions. Lower EC1 and higher soot-EC contribution obtained in tunnel aerosol (AS) samples showed the dominance of diesel-fueled vehicles in the tunnel. The data represented herein would help to identify the characteristic of vehicle emissions.

Analysis and Sources Identification of Atmospheric PM10 and Its Cation and Anion Contents in Makkah, Saudi Arabia

In this paper, atmospheric water-soluble cation and anion contents of PM10 are analysed in Makkah, Saudi Arabia. PM10 samples were collected at five sites for a whole year. PM10 concentrations (µg/m3) ranged from 82.11 to 739.61 at Aziziyah, 65.37 to 421.71 at Sanaiyah, 25.20 to 466.60 at Misfalah, 52.56 to 507.23 at Abdeyah, and 40.91 to 471.99 at Askan. Both daily and annual averaged PM10 concentrations exceeded WHO and Saudi Arabia national air quality limits. Daily averaged PM10 concentration exceeded the national air quality limits of 340 µg/m3, 32% of the time at Aziziyah, 8% of the time at Sanaiyah, and 6% of the time at the other three sites. On average, the cations and anions made a 37.81% contribution to the PM10 concentrations. SO42−, NO3−, Ca2+, Na+, and Cl− contributed 50.25%, 16.43%, 12.11%, 11.12%, and 8.70% to the total ion concentrations, respectively. The minor ions (F−, Br−, Mg2+, NO2−, and PO43−) contributed just over 1% to the ion mass. Four principal components explained 89% variations in PM10 concentrations. Four major emission sources were identified: (a) Road traffic, including emission from the exhaust, wear-and-tear, and the resuspension of dust particles (F−, SO42−, NO3−, Ca2+, Na+, Mg+, Br−, Cl−, NO2−, PO43−); (b) Mineral dust (Cl−, F−, Na+, Ca2+, Mg2+, PO43−); (c) Industries and construction–demolition work (F−, SO42−, Ca2+, Mg2+); and (d) Seaspray and marine aerosols (Cl−, Br−, Mg2+, Na+). Future work would include an analysis of the metal contents of PM10 and their spatiotemporal variability in Makkah.

Characteristics of fine particulate matter (PM2.5) at Jinsha Site Museum, Chengdu, China

Air pollution is a serious threat to ancient sites and cultural relicts. In this study, we collected indoor and outdoor PM_2.5 samples and individual particles at the Exhibition Hall of Jinsha Site Museum in June 2020, and then the chemical components, sources, morphology, and mixing state of the fine particulate matter were analyzed. Our results show that the indoor and outdoor PM_2.5 concentrations at the Exhibition Hall were 33.3±6.6 and 39.4±11.4 μg m^-3, respectively. Although the indoor and outdoor concentrations of OC and EC were close, the proportion of secondary organic carbon in OC outdoor (33%) was higher than that indoor (27%). The PM_2.5 was alkaline both indoors and outdoors, and the outdoor alkalinity was stronger than the indoor alkalinity. SNA (SO₄^2-, NO₃^-, and NH₄⁺) was the dominant component in the water-soluble inorganic ions; Na⁺, Mg²⁺, and Ca²⁺ were well correlated (R²> 0.9), and Cl^- and K⁺ were also highly correlated (R²> 0.8). Enrichment factor analysis showed that Cu (indoor) and Cd were the main anthropogenic elements and that Cd was heavily enriched. Principal components analysis showed that the main sources of PM_2.5 at Jinsha Site Museum were motor vehicles, dust, secondary sources, and combustion sources. The individual particles were classified as organic matter, S-rich, soot, mineral, and fly ash/metal particles, and most of these particles were internally mixed with each other. At last, we proposed pollution control measures to improve the air quality of museums and the preservation of cultural relicts.

Air Quality Over Major Cities of Saudi Arabia During Hajj Periods of 2019 and 2020

Mecca and Madinah are two holy cities where millions of people in general, visit throughout the years, during Hajj (Muslim's pilgrimage) time number of people visit these holy cities from different parts of the world is very high. However, the Government of Saudi Arabia only allowed 1000 pilgrims during the 2020 Hajj especially when the world is suffering from COVID-19. In the present paper, a detailed analysis of air quality parameters available from ground measurements have been carried over major cities of Saudi Arabia, Mecca, Madinah, and Jeddah from June to September 2019 and 2020. At Mecca and Jeddah, PM₁₀, NO₂ and CO concentrations are found to be higher in comparison to stations located close to Madinah. In addition, meteorological parameters, temperature, relative humidity, and wind directions are also analysed to understand changes associated with the meteorological parameters. Our detailed analysis shows a reduction in concentrations of pollutants during the 2020 Hajj, when the lockdown was observed in Saudi Arabia due to COVID-19. During June-August 2020 lockdown period, no major changes in PM₁₀ concentration was observed since there were frequent dust events were observed. In contrast, our results show 44% reduction in NO₂ (8.77 ppbv in 2019 to 4.97 ppbv in 2020) and 16% reduction in CO (0.85 ppm in 2019 to 0.72 ppm in 2020) concentrations during COVID-19 restrictions. The concentrations of NO₂ and CO do not cause any issue for the air quality as NO₂ and CO Indices lie within the green band (Air quality index 0-50). In Mecca, Madinah and Jeddah, the air quality is generally affected during Hajj, but during 2020, the concentration of particulate matter was influenced by local weather conditions.

Source Apportionment of Ambient Black Carbon During the COVID-19 Lockdown

Black carbon (BC) particles being emitted from mobile and stationary emission sources as a result of combustion activities have significant impacts on human health and climate change. A lot of social activities have been halted during the COVID-19 lockdowns, which has evidently enhanced the ambient and indoor air quality. This paper investigates the possible emission sources and evaluates the meteorological conditions that may affect the dispersion and transport of BC locally and regionally. Ground-level equivalent BC (eBC) measurements were performed between January 2020 and July 2020 at a university campus located in Dammam city of the Kingdom of Saudi Arabia (KSA). The fossil fuel (eBCff) and biomass burning (eBCbb) fractions of total eBC (eBCt) concentrations were estimated as 84% and 16%, respectively, during the entire study period. The mean eBCbb, eBCff, and eBCt concentrations during the lockdown reduced by 14%, 24%, and 23%, respectively. The results of statistical analyses indicated that local fossil fuel burning emissions and atmospheric conditions apparently affected the observed eBC levels. Long-range potential source locations, including Iraq, Kuwait, Iran, distributed zones in the Arabian Gulf, and United Arab Emirates and regional source areas, such as the Arabian Gulf coastline of the KSA, Bahrain, and Qatar, were associated with moderate to high concentrations observed at the receptor site as a result of cluster analysis and concentration-weighted trajectory analysis methods.

Temporal variations and source apportionment of volatile organic compounds at an urban site in Shijiazhuang, China

Shijiazhuang, the city with the worst air quality in China, is suffering from severe ozone pollution in summer. As the key precursors of ozone generation, it is necessary to control the Volatile Organic Compounds (VOCs) pollution. To have a better understanding of the pollution status and source contribution, the concentrations of 117 ambient VOCs were analyzed from April to August 2018 in an urban site in Shijiazhuang. Results showed that the monthly average concentration of total VOCs was 66.27 ppbv, in which, the oxygenated VOCs (37.89%), alkanes (33.89%), and halogenated hydrocarbons (13.31%) were the main composite on. Eight major sources were identified using Positive Matrix Factorization modeling with an accurate VOCs emission inventory as inter-complementary methods revealed that the petrochemical industry (26.24%), other industrial sources (15.19%), and traffic source (12.24%) were the major sources for ambient VOCs in Shijiazhuang. The spatial distributions of major industrial activities emissions were identified by using geographic information statistics system, which illustrated the VOCs was mainly from the north and southeast of Shijiazhuang. The inverse trajectory analysis using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) and Potential Source Contribution Function (PSCF) clearly demonstrated the features of pollutant transport to Shijiazhuang. These findings can provide references for local governments regarding control strategies to reduce VOCs emissions.

Distribution characteristics and policy-related improvements of PM2.5 and its components in six Chinese cities

This study presents the distribution characteristics and possible sources of fine particulate matter (PM_2.5) and its components, as well as policy-related pollution reduction in the Chinese cities of Jinan, Shijiazhuang (SJZ), Chengdu, Wuxi, Wuhan, and Harbin (HRB). PM_2.5 samples were collected using mid-volume samplers during the autumn of 2017 in all six cities. The samples were analyzed to determine the ambient PM_2.5 compositions, including the concentrations of water-soluble inorganic ions (WSIIs), carbonaceous aerosols, and elements concentrations. The chemical ratios of organic carbon to elemental carbon and nitrate to sulfate as well as the enrichment factors of elements were calculated to establish the possible sources of PM_2.5 in all six cities. The highest PM_2.5 concentration was 152 μg/m³ in SJZ, while the lowest concentration was 47 μg/m³ in HRB. During the sampling period in these six cities, the PM_2.5 concentrations exceeded the World Health Organization recommended daily average air quality guidelines by 2.4-6.1 times, and WSIIs, carbonaceous aerosols, and elements accounted for 31.8%-61.6%, 9.8%-35.1%, and 0.9%-2.5% of the PM_2.5, respectively. In 2013, the Chinese government formulated the Air Pollution Prevention and Control Action Plan (APPCAP) for controlling air pollution, and effective measures have been implemented since then. Compared with previous studies conducted during 2009-2013 before the implementation of the APPCAP, the concentrations of PM_2.5 and most of its components decreased to varying degrees, and large changes in the chemical ratios of PM_2.5 components were observed. These results indicate that PM_2.5 sources vary among these six cities and that China has improved the ambient air quality in these cities through the implementation of air pollution control policies. The APPCAP have achieved considerable results in continuously reducing pollution concentrations, although the air pollution concentrations observed in this study remain high compared with those of other countries.

Chemical characteristics of road dust PM2.5 fraction in oasis cities at the margin of Tarim Basin

In order to understand the compositions characteristics of particulate matter with aerodynamic diameter less than 2.5 μm (PM_2.5) fraction in road dust (RD_2.5) of oasis cities on the edge of Tarim Basin, 30 road dust (RD) samples were collected in Kashi, Cele, and Yutian in the spring, 2018, and RD_2.5 was collected using the resuspension approach. Eight water-soluble ions, 39 trace elements and 8 fractions of carbon-containing species in PM_2.5 were analyzed. Ca²⁺ and Ca were the most abundant ions and elements in RD_2.5 (7.1% and 9.5%). Cl^- in RD_2.5 was affected not only by attributed to saline-alkali soils in oasis cities of the Tarim Basin and dust from Taklimakan Desert but also by human activities. Moreover, the organic carbon/elemental carbon (OC/EC) ratio indicated that carbon components in RD_2.5 in Cele town mainly come from fossil fuel combustion, while those in Yutian and Kashi mainly come from biomass combustion. It is noteworthy that high Ca in RD_2.5 was seriously affected by anthropogenic emissions, and high Na and K contents in RD_2.5 could be derived from soil and desert dust. It was estimated that Cd, Tl, Sn and Cr were emitted from anthropogenic emissions using the enrichment factor. The coefficients of divergence (COD) result indicated that the influence of local emission on road dust emission is greater than that of long-distance transmission. This study is the first time to comprehensively analyze the chemical characteristics of road dust in oasis cities, and the results provides the sources of road dust at the margin of Tarim Basin.

Source apportionment of fine particulate matter in a Middle Eastern Metropolis, Tehran-Iran, using PMF with organic and inorganic markers

With over 8 million inhabitants and 4 million motor vehicles on the streets, Tehran is one of the most crowded and polluted cities in the Middle East. Frequent exceedances of national daily PM_2.5 limit have been reported in this city during the last decade, yet, the chemical composition and sources of fine particles are poorly determined. In the present study, 24-hour PM_2.5 samples were collected at two urban sites during two separate campaigns, a one-year period from 2014 to 2015 and another three-month period at the beginning of 2017. Concentrations of organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals and specific organic molecular markers were measured by chemical analysis of filter samples. The dominant mass components were organic matter (OM), sulfate and EC. With a 20% water-soluble organic carbon (WSOC) fraction, the predominance of primary anthropogenic sources (i.e. fossil fuel combustion) was anticipated. A positive matrix factorization (PMF) analysis using the ME-2 (Multilinear Engine-2) solver was then applied to this dataset. 5 factors were identified by Marker-PMF, named as traffic exhaust (TE), biomass burning (BB), industries (Ind.), nitrate-rich and sulfate-rich. Another 4 factors were identified by Metal-PMF, including, dust, vehicles (traffic non-exhaust, TNE), industries (Ind.) and heavy fuel combustion (HFC). Traffic exhaust was the dominant source with 44.5% contribution to total quantified PM_2.5 mass. Sulfate-rich (24.2%) and nitrate-rich (18.4%) factors were the next major contributing sources. Dust (4.4%) and biomass burning (6.7%) also had small contributions while the total share of all other factors was < 2%. Investigating the correlations of different factors between the two sampling sites showed that traffic emissions and biomass burning were local, whereas dust, heavy fuel combustion and industrial sources were regional. Results of this study indicate that gas- and particle-phase pollutants emitted from fossil fuel combustion (mobile and stationary) are the principal origin of both primary and secondary fine aerosols in Tehran.

Characterization of aerosol chemical composition and the reconstruction of light extinction coefficients during winter in Wuhan, China

To evaluate light extinction contributions of aerosol chemical constituents and their impacts on atmospheric visibility, the PM_2.5 and its chemical components, light scattering (b_sp) and absorption (b_ap) were continuously measured in Wuhan from January to February 2018. The average of PM_2.5 concentration, b_sp and b_ap were 96.5 ± 13.7 μg m^-3, 564 ± 124 Mm^-1 and 44 ± 8 Mm^-1 during polluted days, respectively, which was about 2.0, 2.1 and 1.6 times higher than those of clean days, respectively. Compared with the clean days, the increase of the mass concentrations of SNA (SO₄^2-, NO₃^-, NH₄⁺) during polluted days was higher than those of organic (OC) and elemental (EC) carbon, indicated the increase of SNA was the main cause of air pollution. The PM_2.5 concentration threshold was 66 μg m^-3, corresponding to the visibility lower than 10 km. The revised Interagency Monitoring of Protected Visual Environments (IMPROVE) algorithm was used to reconstruct the light extinction coefficient (b_ext) in Wuhan. The sum of light extinction coefficients of (NH₄)₂SO₄, NH₄NO₃ and organic matter (OM) accounted for 70.5% and 83.9% of b_ext during clean and polluted days, respectively. The backward trajectory and potential source contribution function (PSCF) analysis revealed that regional transport accounted for 55.6% of the total airflow, which originated from south, northwest and west of Wuhan. The increases of (NH₄)₂SO₄ and NH₄NO₃ concentrations, emitted from local vehicle exhaust and coal combustion, and their hygroscopic growth in ambient were the major causes of pollution in Wuhan.

Elemental Composition of PM2.5 Aerosol in a Residential-Industrial Area of a Mediterranean Megacity

Very little is known about the elemental composition and possible sources of fine aerosol particles from Mediterranean megacities. Fine aerosol particles were collected at a residential-industrial area in Greater Cairo, Egypt, during the period from October 2010 to May 2011. The elemental compositions of the collected samples were quantified by using a homemade energy dispersive x-ray fluorescence spectrometer, whereas black carbon was quantified by a black smoke detector. Fifteen elements have been quantified. Of these constituents, Ca, C, Cl, S, and Fe had the highest concentrations: greater than 1 µg m^-3. The overall mean mass concentration of the collected samples equals 70 µg m^-3; this value exceeds the European Union annual Air Quality Standard levels. The individual elemental concentrations of the fine particles were found to be dominated by elements linked to mineral dust. Most of the monthly variations of elemental concentrations can be attributed to seasonal meteorological conditions. Other possible sources were vehicle-exhaust and industrial activities. The results pinpoint the problem of identifying different sources when one source, in this case, the nearby deserts, is dominant. The results from this study contribute to the growing knowledge of concentrations, composition, and possible sources of ambient fine particulate matter.