Spatial distribution, source identification, and risk assessment of heavy metals in riparian soils of the Tibetan plateau

An integrated evaluation of potentially toxic elements and microplastics in the highland soils of the northeastern Qinghai-Tibetan Plateau

As gateways to the scenic Qinghai-Tibetan Plateau (QTP), some underexplored five grassland (GLs) and three farmland (FLs) soil locations of northeastern counties were investigated. Preliminary detection showed that in the grazing and agricultural soils, elemental concentrations (Fe>Zn>Cr>Cu>Pb>Co>As>Cd) were up to 37 and 10 mg/g, but within the China soil standards, except Cd, while microplastics (MPs) abundances were 200-3640 and 280-973 particles/kg, respectively. Polypropylene (PP: 40-55 %) dominated in GLs mostly as fragments, whereas polyethylene (PE: 72-92 %) in FLs as films. Adsorption results demonstrated that potentially toxic elements (PTEs)-MPs' interaction may chiefly depend on their types and speciation in soils, the physiochemical structure of MPs, and surrounding conditions. The integrated two-dimensional risk assessment categorized three of five GLs under Risk Level VI (high pollution), whereas one of three FLs displayed Risk Level III (moderate pollution). Correlation analysis revealed that altitude, organic matter, soil clay content, and precipitation significantly affected PTEs (p ≤ 0.01), whereas MPs were influenced by altitude, soil clay content, precipitation (p ≤ 0.001), and population density (p ≤ 0.05). Comparison with low-land soils globally designated QTP as a vulnerable region to MPs due to the expanding development. Overall, our study provides a data set to understand the pollution scenario of highlands for its targeted management.

Pollution and ecological risk of heavy metals and arsenic in in road-deposited sediment and rainfall runoff of a coal port in Northern China

Coastal ports are important areas for national economic growth. However, due to human activity and ongoing port development, heavy metals (HMs) and arsenic (As) have increased in the road-deposited sediment (RDS) and runoff of port roads, posing a threat to the environment and ecology. This study focused on a representative coal port in northern China to assess the characterization on occurrence and ecological risk of HMs (Zn, Ni, Cr, Cu, Pb, Cd, and Hg) and As in RDS and runoff in three typical functional areas, including office, storage yard, and dock. Particulate and dissolved HMs and As were determined, and the Zn of RDS was particularly prominent, as well as loading of up to 0.47-2.85 mg/m2. The largest loading of Zn, Ni, Cr, Cu, Pb, Cd and As were all found in the particle size range of 0.001-0.075 mm among different particle size fractions. The results of Potential Ecological Risk Index (RI) showed that the storage yard area showed the highest ecological risk of HMs, including Zn (14.03), Cd (205.07), As (88.1) and Hg (84.48). In addition, it was confirmed that Zn, Cr and Cu were the primarily polluted HMs in port runoff, while the runoff had the greatest mass load of HMs and As in the dock area with the highest Nemerow index method of 4.77. The obtained findings provided a significant scientific basis to understand the non-point source of HMs and As in RDS and rainfall runoff in different typical functional areas of a coal port.

Assessment of health risk and identification of pollution sources of heavy metals in water in Chongqing's wastewater treatment plants based on ICP-MS

Chongqing is located upstream of the Yangtze River and within the Three Gorges Reservoir Area. Boasting a dense hydrological network comprising interconnected rivers, tributaries, and reservoirs, the condition of the natural environment in Chongqing is intrinsically linked to drinking water safety. To evaluate the regional distribution, pollution levels, health risks, and sources of 12 heavy metals, a total of 90 water samples (30 influent sewage, 30 effluent sewage, and 30 tap water samples) were systematically collected from 30 wastewater treatment plants (WWTPs) across Chongqing. Heavy metal pollution index (HPI), heavy metal evaluation index (HEI), degree of contamination (CD), and health risk assessment were utilized in this study to present the findings of a thorough assessment of heavy metal contamination in the region. Meanwhile positive matrices factorization (PMF) was applied to ascertain sources of heavy metals in influent sewage. The results showed that sewage treatment diminished pollutant concentrations. After treatment, Zn, Hg, Pb, and Cr were the primary contaminants in the effluent sewage, significantly surpassing the Class I standard limit for surface water in China. The primary sources of sewage contamination were anthropogenic activities, including agriculture, industry, and transportation. The cumulative health risk from carcinogenic heavy metals surpassed the permissible danger threshold. Cr was responsible for majority of health hazards. These findings indicate the priority control requirements for various heavy metals and establish a scientific foundation for the hierarchical management strategy of heavy metals, optimization of wastewater treatment processes, and the assurance system for drinking water safety.

Distribution and relationship of heavy metals, microbial communities and antibiotic resistance genes in the riparian soils of Daye Lake, China

Heavy metals pose ecological and resistome risks to aquatic systems. To comprehensively assess the health status of aquatic ecosystems, it is necessary to quantify the ecological risks of heavy metals in riparian soils and their associations with microbial communities and antibiotic resistance genes (ARGs), yet related evidence was scarce. This study evaluated the potential ecological risk of heavy metal-contaminated riparian soils of Daye Lake, revealed the distribution of bacterial communities and ARGs by high-throughput sequencing techniques, and explored the association between heavy metals and bacterial communities and ARGs. The results showed that As, Cd, Cu, Pb, and Se were the primary polluting metals in the riparian soils of Daye Lake. Microbial community analysis presented that Proteobacteria (31.5%), Actinobacteria (30.3%), and Acidobacteria (14.1%) appeared to be the top three prevalent phylums, and seven pathogenic genera were identified based on VFDB. Correlation analysis showed that 17 bacterial communities among the top 50 bacterial genera had significant negative associations with heavy metals (r < -0.5; P < 0.05), and 10 bacterial communities had significant positive associations with heavy metals (r > 0.5; P < 0.05), indicating that heavy metals could exert co-selection forces on the microbial community. ARGs analysis presented that vancomycin, multidrug, and aminoglycoside resistance genes were the dominant ARGs. The co-occurrence of ARGs, virulence factor genes (VFGs), and mobile genetic elements (MGEs) (r > 0.8; P < 0.05) suggested high transmission risk of ARGs in environments. The significant correlations of heavy metals and ARGs (P < 0.05), co-occurrence of the resistance genes (MRGs) and ARGs (r > 0.8; P < 0.05), and significant associations between the geochemical enrichment of heavy metals and ARGs (P < 0.05) consistently indicated important impacts of heavy metals on environmental resistome risks. This research firstly revealed the associations between heavy metals and microbial communities and ARGs in riparian soils, which offers valuable insights into risk prevention and pollution control of heavy metals in the environment.

Identification of the pollution sources and hidden clustering patterns for potentially toxic elements in typical peri-urban agricultural soils in southern China

Peri-urban agricultural soils are often contaminated by potentially toxic elements (PTEs) due to rapid urbanization, industrial activities, and agricultural practices. In this study, two advanced analytical methods including positive matrix factorization (PMF) model and K-means clustering algorithm were integrated to explore the potential sources and concealed contamination patterns of 8 PTEs in peri-urban soils in county Gaoming, China. Descriptive statistics showed average concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn) as 19.11, 0.18, 35.69, 20.31, 18.26, 151.7, 67.75, and 0.29 mg/kg, respectively. The PMF model identified three primary sources: geogenic (Cr, Ni), industrial and traffic-related (Pb, Hg, Zn), and agricultural (As, Cd and Cu). The contribution of each source was quantified: geogenic sources contributed 55.6% to Cr and 52.3% to Ni, industrial sources accounted for 41.8% of Pb, 58.4% of Hg, and 41.9% of Zn, while agricultural practices contributed 88.1% of As, 77.9% of Cu, and 70.7% of Cd. Subsequently, K-means clustering classified the soil samples into three distinct clusters based on the derived factor contribution from PMF model, reflecting their clear spatial associations with different types of land use: large-scale agricultural areas (Cluster 1), natural vegetation (Cluster 2), and urbanized zones (Cluster 3). Furthermore, boxplots showed that the highest PTE concentrations were found in the third cluster, confirming the significant impact of human activities, while the lower concentrations in the second cluster indicated more natural conditions. These results underscored the dual influences of agriculture and urbanization on PTE contamination, which highlighted the need for targeted soil management strategies. Moreover, the integration of PMF and K-means clustering effectively reveals potential sources and concealed pollution patterns, providing insights for managing pollution and safeguarding environmental health in rapidly urbanized areas.

Spatial distribution characteristics and risk assessment of heavy metals in soils of Southern Xinjiang oases

The oasis is the most important territorial system of human-earth relationships in the hyper-arid zone. With the socioeconomic development, increasingly serious environmental problems have occurred in the oases. But current research major focus on the soil water balance of oases while ignore the spatial characteristics and risks of heavy metals in soils. Therefore, taking Southern Xinjiang, a typical hyper-arid zone, as a case study site, we collected soil samples from 15 major oases in the region and analyzed the spatial characteristics and risks of eight heavy metals (Cr, Ni, Cu, Zn, As, Cd, Pb, Hg). Through spatial autocorrelation analysis, the contamination index method, the geoaccumulation index method, and risk assessment methods, the analysis results show that (1) the overall concentration of soil heavy metals in the oases of Southern Xinjiang is low and relatively uniformly distributed, and there is a small-scale aggregation. (2) The eight heavy metals in the study area exhibit significant spatial distribution differences, with varying concentrations, but none exceed the risk screening values. The content of 8 heavy metals in the soil of the Southern Xinjiang oasis ranges from 0.01 to 62.73 mg/kg, in descending order of Zn > Cr > Ni > Cu > Pb > As > Cd > Hg. Among them, Zn, Cr, and Ni have the highest concentrations, while Cd, As, and Pb show significant deviations from background values. (3) Except for Cd and Hg, there is no overall ecological risk from soil heavy metals in the soils of most Southern Xinjiang oases. (4) None of the oasis soils in the study area have shown non-carcinogenic risks from heavy metals, but there are some carcinogenic risks for children, which are related to the accumulation of heavy metals and the specificity of the children's population. This study fills a key gap in soil heavy metal research in oasis areas, offering valuable data for future research and policy. Future work should focus on remediation technologies like phytoremediation and microbial treatments, along with targeted policies to reduce pollution risks, especially for vulnerable populations.

Assessment of ecological risks and spatiotemporal monitoring of heavy metal contamination in cultivated soils of the Liaohe River Basin, Jilin Province, China

Ensuring the quality and safety of soil is crucial for achieving ecological sustainability. This study systematically analyzed and evaluated the ecological risks, early warning mechanisms, and mitigation strategies for heavy metals in the Liaohe River Basin of Jilin Province, employing methods such as multiple index models, environmental capacity prediction models, and spatiotemporal cube models. The results indicate that local soil heavy metals range from non-polluted to moderately polluted (0.5-1), with Cr, Cd, and Ni exhibiting relatively high risks. Early warning results reveal that Cr is in a state of low capacity (capacity index = 0.67), and the environmental capacity of soil heavy metals is projected to decline over the next 15 years. Notably, after 15 years, the environmental capacities of As and Cd are expected to decrease to 4.579 kg/hm2 and 0.198 kg/hm2, respectively. Based on the findings, systematic mitigation recommendations, including graded management and land-use optimization, were proposed. This not only provides insights into heavy metal research but also establishes a theoretical foundation for soil pollution management.

Contamination and source-specific health risk assessment of soil heavy metals in the middle and upper reaches of the Heihe River Basin of China

Anthropogenic activities drive heavy metal contamination in soil, making source-specific apportionment essential for managing health risks in rapidly urbanizing areas. This study focuses on the novel task of quantifying health risks from specific sources of heavy metal contamination and visualizing the spatial patterns of human activities' impact on heavy metal contamination and health risks. It combined multiple analytical techniques, including pollution indices, health risk assessments, and bivariate local indicators of spatial association analysis. Additionally, the absolute principal component score-multiple linear regression model, integrated with a human health risk assessment, was employed to quantify health risks and evaluate the contributions of specific sources. Results revealed that Cd and As were at moderate contamination levels, while Zn, Cu, and Ni showed low contamination. Despite generally low contamination levels, moderately to heavily contaminated areas were identified in the southern region correlated with human activities. Although both non-carcinogenic and carcinogenic risks were low for both children and adults, Cr and As were still the main contributors to health risks, primarily through ingestion, with children being at a greater risk compared to adults. The health risks were primarily linked to four sources: traffic and mining, natural sources, agricultural activities, and industrial sources. Industrial (children: 27.47%; adults: 31.96%) and agricultural activities (children: 27.11%; adults: 24.01%) were the primary contributors to non-carcinogenic risks, while the carcinogenic risks were mainly contributed by agricultural activities (children: 40.21%; adults: 40.14%). Therefore, controlling industrial and agricultural activities is crucial to safeguarding public health during sustainable regional development.

Soil heavy metals assessment of the Zhoukou riparian zone base of Shaying river basin, China: spatial distribution, source analysis and ecological risk

The riparian zone serves as an ecological transition area between aquatic and terrestrial environments. Understanding the spatial distribution and origins of heavy metals within this zone is crucial for studying riverine ecosystems. In this research, we assessed the occurrence forms and spatial patterns of heavy metals in the riparian zone of the Shaying River Basin in Zhoukou City. Environmental risks were preliminarily evaluated using indices such as Igeo, RI, and PLI, and the sources of heavy metals were identified through PMF. The results revealed that the overall ecological risk associated with eight analyzed heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn) in this region was low. However, Cd is marked enriched and represents a significant factor contributing to the potential ecological risk within the riparian zone of the basin. The high bioavailability of Cd and Mn in the soils of nine more contaminated sites showed moderate to very high ecological risk. The PMF model identified four pollution primary sources in this region: agricultural and industrial activities (29.4%), upstream water pollution (21.1%), natural sources (26.5%), and transport-related source (23.1%). These findings establish a scientific foundation for the conservation and management of the ecological environment in the riparian zone of the Shaying River Basin in Zhoukou City. Additionally, they will serve as a reference for future research on soil heavy metal migration and sources within the Huaihe River Basin, China.

Evaluation of an aquatic liverwort and terrestrial moss as biomonitors of heavy metals associated with particulate matter

In this study, the capacity of the aquatic liverwort Ricciocarpus natans L. and the terrestrial moss Entodon serrulatus Mitt. as biomonitors of heavy metals associated with particulate matter from a highly polluted urban area was evaluated, and concentrations in moss tissues were correlated with concentrations of PM10 and PM2.5 present in the atmosphere. The two species were exposed by the moss bag technique to the pollution of the Toluca Valley Metropolitan Area (TVMA) for two periods of 6 months, using the sites of the Automatic Atmospheric Monitoring Network of the Government of the State of Mexico, and were subsequently analyzed using elemental and structural characterization techniques. The results show that mainly the functional groups -OH and -NH, N-H and C-O on the surface of the liverwort and moss participate in the adsorption of heavy elements. The average enrichment factors of Cd and Pb show to be highly enriched (> 10) in the study area while chromium is not enriched (< 2). The statistical results indicate a temporary variation in the concentration of metals and particles in the atmosphere, where there is a lower concentration of these pollutants in the rainy and dry-cold season and a higher concentration in the dry-hot season and a possible association of Cr and Cd with PM10 and PM2.5. In addition, except for Cr, both species accumulate the metals associated with airborne particulate matter at equivalent levels. There is strong association between PM2.5 and PM10 particles and between the metals Cr-Pb-Fe in R. natans and between PM2.5-PM10 and Fe and between Cd-Cr-Pb in E. serrulatus and these pollutants are mainly associated with sampling sites with the highest concentrations of metals in the TVMA. Although terrestrial moss showed slightly better characteristics than aquatic liverwort as a biomonitor of heavy metals associated with atmospheric particles, these differences were not statistically significant for all metals, so both species could be useful for heavy metal biomonitoring in highly polluted urban areas.

Soil type data provide new methods and insights for heavy metal pollution assessment and driving factors analysis

Assessing heavy metal pollution and understanding the driving factors are crucial for monitoring and managing soil pollution. This study developed two modified assessment methods (NIPIt and NECI) based on soil type-specific background values and pollution indices, and combined them with the receptor model to evaluate pollution status. Additionally, a structural equation model was used to analyze the driving factors of soil heavy metal pollution. Results showed that the average NIPIt and NECI were 1.48 and 0.92, respectively, indicating a low pollution risk level. In some areas, Cd and Hg were the primary heavy metals contributing to pollution risk, with their highest average concentrations exceeding soil type-specific background values by 2.06 and 2.04 times, respectively. Additionally, in black soils, meadow soils, and chernozems, heavy metals primarily originated from natural sources, accounting for 48.92 %, 45.98 %, and 45.58 %, respectively. In aeolian soils, agricultural sources were predominant, contributing 43.38 %. Soil pH and organic matter were key soil properties affecting NECI and NIPIt, with direct effects of 0.36 and -0.19, respectively. This study aims to provide new methods and insights for the comprehensive assessment and driving factors analysis of soil heavy metal pollution, with the goal of enhancing pollution monitoring and reducing risk.

Risk assessment and source analysis of trace elements in soils around county landfills in Tibet

The ecology of the Qinghai‒Tibet Plateau is fragile, and the ecosystems in the region are difficult to remediate once damaged. Currently, landfilling is the mainstay of domestic waste disposal in China, and numerous, widely distributed county landfills exist. trace elements (TEs) in waste are gradually released with waste degradation and cannot be degraded in nature, affecting environmental quality and human health. To reduce the chance bias that exists in studies of individual landfills, we selected 11 representative county landfills in Tibet, total of 76 soil samples were collected, eight TEs (arsenic (As), mercury (Hg), chromium (Cr), copper (Cu), lead (Pb), cadmium (Cd), nickel (Ni), and zinc (Zn)) were determined, and analysed for the current status of pollution, risk to human health, and sources of TEs to explore the impact of the landfills. The results showed that only a few landfills had individual TEs exceeding the risk screening value of the Soil Environmental Quality Risk Control Standard for Soil Contamination (GB 15618-2018) (pH > 7.5). Most of the soils around the landfills had moderate levels of pollution, but some individual landfills had higher levels, mainly due to Cd and Hg concentrations. Source analysis showed that Hg originated mainly from atmospheric transport; the other TEs came mainly from the weathering of soil parent material and bedrock. The potential risk from TEs to human health was low, and the risk to children was greater than the risk to adults. Among the three exposure routes, oral ingestion resulted in the highest carcinogenic risk and noncarcinogenic risk, with a contribution rate of more than 95%. Among the TEs, Ni had the highest carcinogenic risk, followed by Cr and As, and As had the highest noncarcinogenic risk.

Anthropogenic effects on soils in the eastern Tibetan Plateau revealed by geochemical elemental characteristics

The Tibetan Plateau (TP) constitutes a fragile and sensitive ecological environment, which is vulnerable to global climate change and human activities. To investigate the anthropogenic effects on the TP's environmental system is valuable for guiding human responses and adaptations to future environmental changes. In this study, we detailedly analyzed the geochemical elements of four representative soil sections developed on loess from Ganzi, Jinchuan, Aba, and Chuanzhusi in the eastern TP. The chemical elemental profiles distinctly indicated the presence of typical anthropogenic elements (Cu, Zn, Ni, Cr, Pb, Mn, and Fe), underscoring the substantial influence of human activities on TP soil, and showing spatial variance. Our results indicate that anthropogenic impacts were relatively low at Aba and Ganzi, resulting in a deficit of anthropogenic elements at the surface layer. Whereas at Jinchuan and Chuanzhusi, relatively intense anthropogenic impacts have led to the enrichment of anthropogenic elements in the topsoil. We infer that agricultural activities, increased traffic, and expansion of tourism activities were the major factors affecting the anthropogenic elements of TP soils. Our study highlights the impact of human activities on soil geochemical processes in the Tibetan Plateau.

Different "nongrain" activities affect the accumulation of heavy metals and their source-oriented health risks on cultivated lands

"Nongrain" production on cultivated land is one of the primary environmental issues in China. Different "nongrain" activities may introduce different pollution sources to the local environment, leading to variations in heavy metal contents in soil, which can profoundly impact national food security. In this study, three typical "nongrain" regions (Nanxun (NX), Xiaoshan (XS) and Lin'an (LA)) with intensive aquaculture, tea planting and flower (seedling) growth on cultivated land around the Hangzhou metropolitan area were selected to address the spatial heterogeneity of accumulation levels, sources and source-oriented health risks of heavy metals in soil. The results showed that Hg was the main pollutant in NX and XS, while Cd and As were the major contaminants in LA. Aquiculture and sericultural industries (37.43%), natural sources (23.59%) and industrial activities (38.99%) were the major sources in NX; atmospheric deposition (37.73%), flower and seedling planting (23.49%) and metal-related industries (35.16%) were the major sources in XS; and atmospheric deposition (28.06%), excessive application of fertilizers and pesticides during tea planting (43.47%) and natural sources (28.47%) were the major sources in LA. The major risk population, area, exposure route and hazardous elements were children, LA, ingestion and As and Cr, respectively. From the perspective of source-based health risk assessment, in addition to natural sources that are difficult to intervene in, industrial activities, especially leather and wood process industries, metal-related industries and excessive fertilizer and pesticide application during tea planting contributed the most to the total health risk, which explained 67%, 41% and 42%, respectively, of the total risk in NX, XS and LA. High health risks are present in sources with heavy loadings of hazardous heavy metals (As and Cr); thus, to protect human health, the corresponding high-risk anthropogenic pollution sources in different "nongrain" areas need to be controlled.

Moss as a passive biomonitoring tool for the atmospheric deposition and spatial distribution pattern of toxic metals in an industrial city

Anthropogenic pollution impacts human and environmental health, climate change, and air quality. Karabük, an industrial area from the Black Sea Region in northern Türkiye, is vulnerable to environmental pollution, particularly soil and air. In this research on methodological aspects, we analyzed the concentrations of six potential toxic metals in the atmospheric deposition of the city using the passive method of moss biomonitoring. The ground-growing terrestrial moss, Hypnum cupressiforme Hedw., was collected during the dry season of August 2023 at 20 urban points. The concentrations of Cr, Cu, Cd, Ni, Pb, and Co were determined in mosses by the ICP-MS method. Descriptive statistical analysis was employed to evaluate the status and variance in the spatial distribution of the studied metals, and multivariate analysis, Pearson correlation, and cluster analysis were used to investigate the associations of elements and discuss the most probable sources of these elements in the study area. Cd and Co showed positive and significant inter-element correlations (r > 0.938), representing an anthropogenic association mostly present in the air particles emitted from several metal plants. The results showed substantial impacts from local industry, manufactured activity, and soil dust emissions. Steel and iron smelter plants and cement factories are the biggest emitters of trace metals in the Karabük area and the primary sources of Cr, Cd, Ni, and Co deposition.

Spatial distribution characteristics and source apportionment of heavy metal(loid)s in park dust in the Mianyang urban area, China

Park dust is a carrier of heavy metal pollutants and could potentially harm the health of urban residents. The concentrations of 10 heavy metal(loid)s (HMs) in park dust from the Mianyang urban area were analysed via X-ray fluorescence spectrometry. Based on ArcGIS spatial analysis, Spearman correlation analysis, spatial autocorrelation analysis, and the positive matrix factorization (PMF) model, the spatial distribution and sources of HMs in park dust were studied. The average contents of Zn, Co, Cu, Cr, Pb, and Ba in park dust were 185.0, 33.7, 38.7, 178.7, 51.0, and 662.1 mg/kg, respectively, which are higher than the reference values. The 10 HMs exhibited obvious spatial distribution and local spatial agglomeration patterns. High concentrations of As and Pb were primarily concentrated in the eastern part of the Mianyang urban area. High concentrations of Zn, Cr, and Cu were largely distributed in parks near the Changjiang River and Fujiang River. A high concentration of Co was concentrated in the northern region. The high-value areas of Mn, Ba, V, and Ni occurred far from the city centre and were located in the southwestern region. We found that Pb and As primarily originated from mixed traffic and natural sources; Zn, Cr, and Cu mainly originated from industrial activities; Co largely originated from building sources; and Ba, Ni, Mn, and V were mostly derived from natural sources. Mixed, industrial, building, and natural sources accounted for 24.5%, 24.8%, 24.7%, and 26.0%, respectively, of the HM sources. Co, Cu, Cr, and Zn in the Mianyang urban area were obviously influenced by human activities and should receive close attention.