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The effects of railway operation on soil environments are an important topic. In this research, soil samples were collected from two diesel-driven railways and two electric railways in Japan. A positive matrix factorization (PMF) model was applied to investigate the sources of eight heavy metals in the soil near the railways. The results showed that railway operation was the dominant anthropogenic source of heavy metals in the soil in the study areas among five potential sources, with contributions ranging from 11.73% to 42.55%. Compared with that of electricity-driven railways, the effect of diesel-driven railways was larger. The environmental risk-assessment analysis suggested that the soils near the selected railways fall within the weak-to-extremely strong contamination category, and experienced moderate-to-extremely strong ecological risk. A health risk assessment revealed that the soil presented both noncarcinogenic and carcinogenic risks for children, with ingestion as the principal exposure pathway. The PMF-Environment Risk Assessment and PMF-Human Health Risk Assessment models were developed to obtain the ecological and human health risks for every source category. Railway operation was regarded as the major factor influencing ecology and human health at the diesel-driven railway sampling sites. However, at electricity-driven railway sampling sites, natural sources were dominant.

Soil pollution due to toxic elements (TEs) has been a core environmental concern globally, particularly in areas with developed industries. In this study, we sampled 300 surface (0–0.2 m) soil samples from Yuyao City in eastern China. Initially, the geo-accumulation index, potential ecological risk index, single pollution index, and Nemerow composite pollution index were used to evaluate the soil contamination status in Yuyao City. Ordinary kriging was then deployed to map the distribution of the soil TEs. Subsequently, indicator kriging was utilized to identify regions with high risk of TE pollution. Finally, the positive matrix factorization model was used to apportion the sources of the different TEs. Our results indicated that the mean content of different TEs kept the order: Zn > Cr > Pb > Cu > Ni > As > Hg ≈ Cd. Soil pollution was mainly caused by Cd and Hg in the soil of Yuyao City, while the content of other TEs was maintained at a safe level. Regions with high TE content and high pollution risk of TEs are mainly located in the central part of Yuyao City. Four sources of soil TEs were apportioned in Yuyao City. The Pb, Hg, and Zn contents in soil were mainly derived from traffic activities, coal combustion, and smelting. Meanwhile, Cu was mainly sourced from industrial emissions and atmospheric deposition, Cr and Ni mainly originated from soil parental materials, and Cd and As were produced by industrial and agricultural activities. Our study provides important implications for improving the soil environment and contributes to the development of efficient strategies for TE pollution control and remediation.

To understand the influence of trans-boundary air pollution on the air quality of Fukuoka, the mass concentration and chemical composition of fine particulate matter (PM) were observed at urban (Fukuoka) and rural (Fukue Island) sites in the northern Kyushu area in Japan. Chemical composition was measured using an aerosol mass spectrometer. Organic aerosol (OA) data were analyzed by the positive matrix factorization (PMF) method. Sulfate and low-volatile oxygenated OA (LV-OOA) were dominant for all of the PM2.5 mass variations on Fukue Island, where the trans-boundary air pollution is dominant in the winter-spring season. In Fukuoka, however, sulfate accounted for the largest fraction of total chemical species under high PM2.5 mass concentrations (>35 µg·m−3), while organics and nitrate made up a large fraction under low PM2.5 (<10 µg·m−3). Under the high PM2.5 condition, LV-OOA was also dominant. This indicates that high PM2.5 mass concentrations were attributed to the long-range transport of air pollution. Although the trans-boundary air pollution prevails in the winter-spring season, high sulfate concentrations were observed in the summer of 2012. In addition to the volcanic activities and photochemical reactions, long-range, trans-boundary air pollutions are influential factors not only in winter-spring but also in summer.

Air pollution is a growing global concern due to harmful constituents like potentially toxic metals (PTMs), which can attach to particles such as dust, soot, and secondary aerosols, increasing their toxicity. This study assessed the seasonal variation, source apportionment, meteorological patterns, and health risks associated with PTMs (V, Mn, Cd, Cr, Fe, Zn, Ni, As, Co, Cu, Pb) in PM₂.₅ over Ilorin, Nigeria. PM 2.5 data for 2019 were obtained from the SPARTAN network at the University of Ilorin and processed for analysis. Results showed that PTM concentrations—particularly Fe, Zn, Cr, Pb, and Co, were significantly higher during the dry season. Cu and Cd also contributed to observed seasonal variations. PMF showed that the sources of pollutant were crustal, industrial sources, secondary inorganic, and biomass burning. EF showed that Cu, Pb, As had values that were between 10 and 100 indicating that they were from both crustal and anthropogenic sources. Cd and Zn had values of 953.27 and 217.87 respectively, which were greater than 100 indicating that they were from industrial sources. Finally, V, Cr, Mn, Fe, Co, had values of 6.05, 1.97, 2.47, 1.00, and 5.28 respectively, which indicates that they were majorly from crustal sources. The Health risk assessment (non-cancer risk) via inhalation revealed a high hazard index (HI = 99.12), mainly from Fe (66.48) and Zn (31.76). Monte Carlo simulation for cancer risk (CR) indicated Cr and As as the highest contributors via inhalation (7.06E-05 and 2.84E-06), while Ni posed the greatest risk via dermal exposure (3.20E-05). These findings highlight significant health concerns associated with airborne PTMs and the need for targeted air quality management, particularly during the dry season.

The presence of heavy metals in soil has gained considerable attention due to their potential risks to ecosystems and human health. In this study, a thorough soil investigation was performed in the hilly region of central Hainan, which was formerly regarded as an area with the highest ecological environmental quality. A total of 7094 soil samples were systematically collected with high density over a large area. Simultaneously, a detailed investigation was conducted on the surrounding environment of each sampling point, including environmental factors such as soil, land use and crop types. The soil samples were analysed for heavy metals, pH, organic matter, and other parameters. The soil heavy metal pollution level, ecological risk and health risk were evaluated using the geo-accumulation index and the potential ecological risk index. The findings showed that the average contents of the heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil were 1.68, 0.042, 24.2, 6.49, 0.0319, 7.06, 29.6 and 49.8 mg·kg −1 respectively. Except for Hg, the mean values of the other heavy metals were either lower than or similar to the background values of Hainan. Also, only a few localised areas showed contamination by heavy metals. The primary sources of heavy metals, identified by a positive matrix factorisation model, could be categorised into four types: natural sources related to the soil formation process from acidic intrusive rocks (such as granite); natural sources primarily influenced by atmospheric deposition; anthropogenic sources associated with agricultural activities; and natural sources related to the soil formation process from middle-mafic intrusive rocks and black shales. The correlation analysis and variance analysis findings suggested that the content of heavy metals in the soil was primarily associated with the parent rock. The study area generally had low heavy metal levels and was not significantly polluted. However, agricultural activities still affected the enrichment of heavy metals. Therefore, it is imperative to remain vigilant about the ecological risks linked to soil heavy metals while continuing land development and expanding agricultural activities in the future. These findings indicate that conducting high-density soil surveys can enhance our understanding of regional soil heavy metals and enable reliable recommendations for agricultural planning. Whether in areas with low pollution risk or potential pollution risk, it is recommended that high-density soil surveys be conducted provide scientific guidance for further agricultural development.

Volatile organic compounds (VOCs) were measured online at an urban site in Beijing in August–September 2010. Diurnal variations of various VOC species indicate that VOCs concentrations were influenced by photochemical removal with OH radicals for reactive species and secondary formation for oxygenated VOCs (OVOCs). A photochemical age‐based parameterization method was applied to characterize VOCs chemistry. A large part of the variability in concentrations of both hydrocarbons and OVOCs was explained by this method. The determined emission ratios of hydrocarbons to acetylene agreed within a factor of two between 2005 and 2010 measurements. However, large differences were found for emission ratios of some alkanes and C8 aromatics between Beijing and northeastern United States secondary formation from anthropogenic VOCs generally contributed higher percentages to concentrations of reactive aldehydes than those of inert ketones and alcohols. Anthropogenic primary emissions accounted for the majority of ketones and alcohols concentrations. Positive matrix factorization (PMF) was also used to identify emission sources from this VOCs data set. The four resolved factors were three anthropogenic factors and a biogenic factor. However, the anthropogenic factors are attributed here to a common source at different stages of photochemical processing rather than three independent sources. Anthropogenic and biogenic sources of VOCs concentrations were not separated completely in PMF. This study indicates that photochemistry of VOCs in the atmosphere complicates the information about separated sources that can be extracted from PMF and the influence of photochemical processing must be carefully considered in the interpretation of source apportionment studies based upon PMF. Key Points Photochemistry significantly influenced VOC concentrations VOC emission ratios and source allocations of OVOCs are determined PMF factors represent different degrees of photochemical processing of VOCs

Environmental contextCarbonaceous components in PM2.5 have a negative effect on the environment, human health and climate. We explored the pollution characteristic, potential sources and interaction of carbonous aerosols in two adjacent areas in Shanxi, China. The concentration levels of organic carbon and elemental carbon were of a moderate level of all those measured between 2009 and 2020. Vehicle exhaust and coal combustion were the two main sources, and Yuci may be affected by the regional transport of Taiyuan in winter.RationaleCarbonaceous aerosols seriously affect people’s health and have a strong scattering effect on visible light. Pollution cuased by carbonaceous components in Taiyuan is serious. Numerous universities in Taiyuan have been moving to Yuci college town since 2013, and the amount of organic pollutants has increased gradually with the growing population. It is necessary to study the characteristics and relationship of carbonaceous aerosols in these two adjacent areas.MethodologyPM2.5 samples were collected in Taiyuan and Yuci college town in 2017 and 2018, and eight carbonaceous components were analysed using a Sunset Laboratory analyser. Pollution characteristic, potential sources and interaction of carbonous aerosols in the two adjacent areas were investigated.ResultsThe average organic carbon (OC) and elemental carbon (EC) concentrations were 12.6 and 6.8 µg m−3 in Taiyuan and 11.7 and 6.9 µg m−3 in Yuci. The OC and EC concentrations in Taiyuan can be approximately divided into three levels between 2009 and 2020, and the OC and EC levels in Taiyuan studied here (2017 and 2018) were in the middle level. The OC and EC concentrations were higher when the temperature was lower.DiscussionThe OC concentration in December was the highest among three winter periods, which may be caused by secondary organic carbon formation related to the lower temperature and an inversion layer. Four source categories were identified using positive matrix factorisation, namely secondary source (25.0%), dust source (16.6%), vehicle exhaust (27.0%) and coal combustion (31.4%). In Taiyuan and Yuci, the trajectory clusters were mainly from north-west and west in winter, whereas the air masses not only originated from north-west, but also north and south in autumn. Yuci may be affected by Taiyuan's regional transport in winter. The results clarify the characteristics of carbon aerosols in the two adjacent areas, and provide fundamental data for the prevention and control of regional air pollutants.

Understanding pollution levels, ecological health risks, and sources of potentially toxic metals (PTMs) in the soil from university campuses is critical for assessing environmental safety. Soil samples were collected from 12 locations across urban parks and green areas at Sohag University in Egypt. The samples were processed and analysed for heavy metals, including iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), chromium (Cr), lead (Pb), zinc (Zn), copper (Cu), and cadmium (Cd). Pollution levels were evaluated using indices such as the pollution index (PI), pollution load index (PLI), geo-accumulation index (Igeo), and enrichment factors (EFs). Among the pollution indices, the EFs showed the highest sensitivity in detecting anthropogenic contributions, particularly for Cd, Pb, and Cr. Spatial distribution maps and multivariate statistical analyses, including correlation matrix (CM), principal component analysis (PCA), and cluster analysis (CA), were applied to identify the relationships between PTMs and soil properties, and source apportionment was performed using positive matrix factorisation (PMF). The results indicated that Mn, Ni, and Co were primarily geogenic, whereas Pb, Zn, Cr, and Cd showed higher concentrations, suggesting moderate-to-significant anthropogenic pollution. Pb and Cd pose considerable ecological risks, whereas other metals such as Cr and Cu exhibit moderate ecological threats. The non-carcinogenic and carcinogenic risks to the students were within safe limits, as defined by United States Environmental Protection Agency (USEPA) threshold values. Source apportionment using PMF identified five main sources of PTMs: industrial and anthropogenic activities (30.0%), traffic emissions (25.0%), natural soil processes (20.0%), agricultural practices (15.0%), and mixed industrial traffic sources (10.0%). These findings emphasise the importance of controlling anthropogenic activities to ensure a safer campus environment.

The aim of this study is to determine the level and source of pollution by potentially toxic elements (PTEs) due to torrential floods in the catchment area of the Drina River under complex geological conditions. The degree of soil and sediment pollution by PTEs was estimated by calculating the Pollution Index (PI) and the Geo‐accumulation index (Igeo). Sources of PTEs were determined using Principal component analysis (PCA) for soil and sediment and the Positive Matrix Factorisation (PMF) model for sediment. To fully include the spatial component when determining the source of PTEs, Bivariate Local Moran's I analysis was also applied. By comparing the applied methods, it was determined that PCA is suitable for determining the sources of PTEs in soil and for investigating the sedimentation process in sediment, while the PMF model is more suitable for determining the sources of PTEs in sediment. It was also determined that when the geological substrate is rich and after high‐intensity flooding, there is an increase in As, Cd, Co, Cu and Fe content in sediment compared with soil. Arsenic was partially impacted by anthropogenic factors, with Igeo values for soil (16.21%) and sediment (21.76%) at the polluted level.