Source apportionment and risk assessment for available occurrence forms of heavy metals in Dongdahe Wetland sediments, southwest of China

An insight into sediment fractionation analysis: from sampling to visualisation of results

This review is focused on the importance of operational conditions for metal fractionation and their influence on the results obtained, using both sequential and single step extractions. The discussion is about the different pathways by which metals are incorporated into aquatic systems and the relationship between the nature of sediments and their interaction with metals. In addition, the relevance of the so-called metal extraction methods, either sequential or single-step extractions, to obtain information about the bioavailability and mobility of metals in sediments is considered. Several aspects, such as sampling and sample storage, sediment processing (drying and sieving), sediment mass/extractant volume ratio and operational time, are reviewed since they can significantly affect the recoveries of metals associated with each geochemical phase. Finally, chemometric techniques are addressed as useful tools to visualise and interpret the data obtained and transform them into relevant information. Although a variety of reagents and operating conditions have been used with satisfactory results, there are no standardised protocols, with the exception of the BCR, which has undergone successive modifications. This shows that even the best combination of extractants can have advantages and limitations, and the use of one protocol or another will depend on the type of information required. In this sense, the experimental conditions play a relevant role in obtaining reliable information on the mobility and availability of metals.

Study of biological indicators of heavy metal pollution in sediments and plants of Hoor-Al-Azim wetland

Wetland ecosystems are vulnerable to various environmental pollutants. In southwest Iran, the presence of significant wetlands alongside multiple oil facilities has led to serious biological issues for these ecosystems. This study was conducted in 2022 to investigate biological indicators of heavy metal pollution in the sediments and plants of the Hoor-al-Azim wetland. A total of 10 samples of sediments and the plant species Typha latifolia were collected. Heavy metals consist of Pb, Hg, Ni, Cu, and Cd were measured. The contamination level of sediments was assessed using contamination factor (CF) and ecological risk (ER) indices, while the transfer of pollution to native plant species was evaluated through transfer factor (TF) and bioaccumulation factor (BCF) indices. Results indicated that in sediment samples, Cd had the lowest average concentration (0.052 mg/kg) and Ni had the highest (147 mg/kg). In plant samples, Cd also showed the lowest concentration (0.086 mg/kg), while Hg had the highest (43.6 mg/kg). Pb and Ni levels were significantly elevated compared to other metals. The CF and ER indices revealed that Ni and Pb posed the greatest pollution levels and ecological risks. The TF index indicated that lead had the highest biological pollution potential (1.06). The average BCF values for lead, nickel, and copper were 0.05, 0.053, and 0.12, respectively. Overall, sediment pollution levels in the wetlands near oil facilities are concerning. Therefore, implementing environmental management strategies, including bioremediation, is crucial to mitigate pollution impacts.

Source-oriented health risk assessment of soil potentially toxic elements based on Monte Carlo simulation in the upper reaches of Wei River Basin, China

The natural environment and public health are gravely threatened by the enrichment of soil potentially toxic elements (PTEs). To explore the contamination level, sources and human health risks posed by PTEs, high-density soil sampling was carried out in the upper Wei River region (UWRR). The results demonstrated that the pollution risk and ecological risk in UWRR as a whole were at a low level, but there were moderate or higher ecological risks of Hg and Cd in some areas. Source analysis of soil PTEs was conducted via absolute principal component score multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) receptor models. APCS-MLR identified three potential sources, while the source division of PMF model was more detailed, which identified four potential sources: mining, coal combustion, machinery manufacturing and agricultural sources, with contribution percentages of 31%, 3%, 37% and 29% respectively. According to the probabilistic human health risk assessment (HHRA), the non-carcinogenic risk for adults was negligible, while that for children cannot be negligible. There were total carcinogenic risks for all populations, but the risk level was acceptable. The total cancer risk for children surpassed 1E-04 by 31.29%, implying a significant carcinogenic risk. Machinery manufacturing was found to be the most significant anthropogenic source of health concerns. This study offers an illustration of probabilistic risk assessment based on sources. The results of the study are favorable to provide new perspectives and scientific reference for soil PTE risk assessment and pollution control.

Potentially toxic elements in surface sediments of the Beibu Gulf, South Sea, China: Occurrence, bioavailability and probabilistic risk assessment

At present, pollution of gulf sediments with potentially toxic elements (PTEs) has become a prominent marine environmental problem. This study thoroughly investigated the occurrence, bioavailability, and probabilistic risk of PTEs in the surface sediments of the Beibu Gulf. The average total concentrations (mg/kg) were 8.03 for As, 0.06 for Cd, 52.73 for Cr, 9.86 for Cu, 0.04 for Hg, 18.70 for Ni, 27.77 for Pb and 59.80 for Zn, respectively. The positive matrix factorization model revealed that the PTE enrichment was primarily due to composite sources from aquaculture and fisheries activities, industrial and agricultural sources. Risk assessment code and correlation analysis indicated that Cd had the highest bioavailability, influenced by TOC and TP. The probabilistic risk assessment model estimated a 60.83 % probability that the mixed PTEs in the Beibu Gulf's surface sediments could have toxic effects on aquatic life. These findings underscore the impact of intensive human activities on PTE pollution and highlight the need for further research on PTE ecotoxicology and pollution control strategies.

A comprehensive study of source apportionment, spatial distribution, and health risks assessment of heavy metal(loid)s in the surface soils of a semi-arid mining region in Matehuala, Mexico

BACKGROUND

This study investigates the contamination level, spatial distribution, pollution sources, potential ecological risks, and human health risks associated with heavy metal(loid)s (i.e., arsenic (As), copper (Cu), iron (Fe), manganese (Mn), lead (Pb), and zinc (Zn)) in surface soils within the mining region of Matehuala, located in central Mexico.

OBJECTIVES

The primary objectives are to estimate the contamination level of heavy metal(loid)s, identify pollution sources, assess potential ecological risks, and evaluate human health risks associated with heavy metal(loid) contamination.

METHODS

Soil samples from the study area were analysed using various indices including Igeo, Cf, PLI, mCd, EF, and PERI to evaluate contamination levels. Source apportionment of heavy metal(loid)s was conducted using the APCS-MLR and PMF receptor models. Spatial distribution patterns were determined using the most efficient interpolation technique among five different approaches. The total carcinogenic risk index (TCR) and total non-carcinogenic index (THI) were used in this study to assess the potential carcinogenic and non-carcinogenic hazards posed by heavy metal(loid)s in surface soil to human health.

RESULTS

The study reveals a high contamination level of heavy metal(loid)s in the surface soil, posing considerable ecological risks. As was identified as a priority metal for regulatory control measures. Mining and smelting activities were identified as the primary factors influencing heavy metal(loid) distributions. Based on spatial distribution mapping, concentrations were higher in the northern, western, and central regions of the study area. As and Fe were found to pose considerable and moderate ecological risks, respectively. Health risk evaluation indicated significant levels of carcinogenic risks for both adults and children, with higher risks for children.

CONCLUSION

This study highlights the urgent need for monitoring heavy metal(loid) contamination in Matehuala's soils, particularly in regions experiencing strong economic growth, to mitigate potential human health and ecological risks associated with heavy metal(loid) pollution.

Assessment of water quality and source apportionment of pollution in a tropical river in eastern India: A study utilizing multivariate statistical tools and the APCS-MLR receptor model

The Mundeswari River, an ecologically distressed river in eastern India, has been subjected to water quality deterioration largely due to anthropogenic activities in its vicinity. This study aimed to comprehensively evaluate the current state of pollution in the river and assess the appropriateness of river water for irrigation, given its extensive use for agricultural purposes. Monthly water quality monitoring was undertaken at four distinct sampling sites (SP1-SP4) over a two-year period (2020-2022), considering seventeen water quality parameters. This research employed principal component analysis/factor analysis (PCA/FA) and absolute principal component score-multiple linear regression (APCS-MLR) receptor modelling. These methodologies were used to discern and quantify potential sources of pollution influencing the water quality of the Mundeswari River. The study revealed that the water quality of the Mundeswari River was most degraded during the pre-monsoon season. Among the four sampling sites, SP3 exhibited the highest level of pollution with mean biochemical oxygen demand (BOD) and chemical oxygen demand (COD) values of 5.36 mg/L and 44.72 mg/L, respectively. According to the one-way analysis of variance (ANOVA), there was considerable spatial and seasonal disparities (P < 0.05) in most water quality parameters. The PCA/FA extracted four latent pollution sources, accounting for 81.5% of the total variance. The primary factors influencing the quality of river water are natural weathering processes, discharge of domestic effluent and waste, and agricultural runoff. The APCS-MLR receptor model further revealed that agricultural drainage factors and the discharge of domestic effluent and waste had a greater impact on the Mundeswari River. The investigation concluded that the mean values of all indicators for irrigation suitability were below the defined threshold limits, indicating that the water of the studied river appears suitable for irrigation. The outcomes of this study may significantly contribute to the formulation of sustainable strategies for the ecological rejuvenation of the Mundeswari River.

Pollution, cumulative ecological risk and source apportionment of heavy metals in water bodies and river sediments near the Luanchuan molybdenum mining area in the Xiaoqinling Mountains, China

The water and sediment samples were collected from the Yu River and Taowanbei River during periods of summer and winter. The NCPI, EWQI, Igeoand PERI were used to evaluate the pollution degree and cumulative ecological risk of HMs in the water and sediments. The PMF model was used to analyze the sources of HMs in river sediments. The pollution degree of Cd, Hg and Zn in the water reached the severe pollution level, in the rank of Hg > Zn > Cd. Cd and Zn in sediments are heavily polluted, Cu is lightly polluted, Pb and As are within the warning range, and the pollution rank is Cd > Zn > Cu > Pb > As. The cumulative ecological risk of HMs in sediments reached extremely strong level, mainly Cd and Hg. The main sources of HMs in sediments are mining sources, mixed agricultural and transport sources, and natural sources, which contributed 42.1 %, 34.1 % and 23.8 %, respectively.

High-density sampling of soil heavy metals in the upper Bailang River basin: contamination characteristics, sources, and source-oriented health risk assessment

Heavy metals (HMs) seriously harm soil environment and threaten crop quality and human health. The aim of the study was to investigate the characteristics, quantify the sources and assess the risks of HMs in soil of upper Bailang River Basin (UBRB). The results indicated that the soils in UBRB were at a non-polluted level and posed a low ecological risk to the environment as a whole. The main pollutants were Ni and Cr obtained by indices Pi and Igeo. Based on the consideration of toxicity, the fuzzy comprehensive evaluation model and Ei index revealed that Hg and Cd were dominating pollutants and ecological risk factors of soil in UBRB. The positive matrix factorization model ascertained five potential sources of soil HMs, namely, plastic processing, energy activities, parent material, transportation and agriculture mixed source and industrial manufacturing, with contribution rates of 17%, 7%, 15%, 29% and 32%, respectively. Natural source primarily determined the non-carcinogenic risk for all populations, accounting for about 43% of the total risk. Industrial manufacturing mainly determined the carcinogenic risk, accounting for about 45%. For adults, the risk was acceptable for most of the sample points. For children, potential non-carcinogenic risks were present in 13.19% of the sample sites, which were mainly located in the west, and unacceptable carcinogenic risks were present in 57.21% of the sample sites, which were mainly concentrated in the western and central parts.

Distribution, mobilization, risk assessment and source identification of heavy metals and nutrients in surface sediments of three urban-rural rivers after long-term water pollution treatment

Sediments are critical pollution carriers in urban-rural rivers, which can threaten the water quality of the river and downstream lakes for a long time. However, it is still not clear whether conventional water pollution treatments could abate sediment pollution or not. In this study, heavy metals (HMs) and nutrient salts in the surface sediments and overlying water were investigated after decades' water pollution treatment in three urban-rural rivers. HM speciation was determined by the sequential extraction; diffusion fluxes were estimated using Fick's first law; HM ecological risk and nutrient pollution were evaluated; and pollution sources were identified by statistical analysis and GIS. The results showed that the HMs and nutrients were extremely serious in the urban regions. The accumulation level of Pb, Cu and Cd in the sediments of the three rivers were all much higher than the soil background value, and the labile fractions accounted for high proportions (57 % for Pb, 55 % for Cu and 43 % for Cd), which could be easily eluate from the sediments and caused hazards to the aquatic environment. The sediment diffusion fluxes of HMs and ammonia nitrogen were mostly positive, which indicated these sites currently released these pollutants from sediment to overlying water. Cd, Pb, Cu and Cr may mainly originate from industrial discharge and domestic sewage, while Cr was also greatly affected by crustal weathering; nutrient pollution may originate from agricultural activities and domestic sewage. Our study demonstrated that after decades' conventional water treatment in these rivers, the sediment pollution was still in a serious level with high ecological risk, and Cd was the dominant pollutant. At present, the external point source pollution has been effectively controlled, thus, the in-depth understanding of the sediment pollution characteristics after long-term water treatment could provide a scientific basis for the accurate elimination of river pollution.

The hidden threat of heavy metal leaching in urban runoff: Investigating the long-term consequences of land use changes on human health risk exposure

This study evaluated the potential effects of long-term land use and climate change on the quality of surface runoff and the health risks associated with it. The land use change projection 2030 was derived from the main changes in land use from 2009 to 2019, and rainfall data was obtained from the Long Ashton Research Station Weather Generator (LARS-WG) model. The Long-Term Hydrological Impact Assessment (L-THIA) model was then utilized to calculate the rate of runoff heavy metal (HM) pollutant loading from the urban catchment. It was found that areas with heavy development posed a significantly greater public health risk associated with runoff, with higher risks observed in high-development and traffic areas compared to industrial, residential, and commercial areas. Additionally, exposure to Lead (Pb), Mercury (Hg), and Arsenic (As) was found to contribute significantly to overall non-carcinogenic health risks for possible consumers of runoff. Carcinogenic risk values of As, Cadmium (Cd), and Pb were also observed to increase, particularly in high-development and traffic areas, by 2030. This investigation offers important insight into the health risks posed by metals present in surface runoff in urban catchment areas under different land use and climate change scenarios.

A Monte Carlo simulation-based health risk assessment of heavy metals in soils of the tropical region in southern China

The disturbance of ecological stability may take place in tropical regions due to the elevated biomass density resulting from heavy metal and other contaminant pollution. In this study, 62 valid soil samples were collected from Sanya. Source analysis of heavy metals in the area was carried out using absolute principal component-multiple linear regression receptor modelling (APCS-MLR); the comprehensive ecological risk of the study area was assessed based on pollution sources; the Monte-Carlo model was used to accurately predict the health risk of pollution sources in the study area. The results showed that: The average contents of soil heavy metals Cu, Ni and Cd in Sanya were 5.53, 6.56 and 11.66 times higher than the background values of heavy metals. The results of soil geo-accumulation index (Igeo) showed that Cr, Mo, Mn and Zn were unpolluted to moderately polluted, Cu and Ni were moderately polluted, and Cd was moderately polluted to strongly polluted. The main sources of heavy metal pollution were natural sources (57.99%), agricultural sources (38.44%) and traffic sources (3.57%). Natural and agricultural sources were jointly identified as priority control pollution sources and Cd was the priority control pollution element for soil ecological risk. Heavy metal content in Sanya did not pose a non-carcinogenic risk to the population, but there was a carcinogenic risk to children. The element Zn had a high carcinogenic risk to children, and was a priority controlling pollutant element for the risk of human health, with agricultural sources as the priority controlling pollutant source.

Comprehensive assessment of exposure and environmental risk of potentially toxic elements in surface water and sediment across China: A synthesis study

China faces a serious challenge with water pollution posed by potentially toxic elements (PTEs). Comprehensive and reliable environmental risk assessment is paramount for precise pollution prevention and control. Previous studies generally focused on a single environmental compartment within small regions, and the uncertainty in risk calculation is not fully considered. This study revealed the current exposure status of 11 PTEs in surface water and sediment across China using previously reported concentration data in 301 well-screened articles. Ecological and human health risks were evaluated and the uncertainty related to calculation parameters and exposure dataset were quantified. PTEs of high concern were further identified. Results showed Mn and Zn had the highest concentration levels, while Hg and Cd had the lowest concentrations in both surface water and sediment. Risk assessment of individual PTE showed that high-risk PTEs varied by risk receptors and environmental compartments. Nationwide, the probability of aquatic organisms being affected by Mn, Zn, Cu, and As in surface water exceeded 10 %. In sediment, Cd and Hg exhibited high and considerable risk, respectively. As was identified as the major PTE threatening human health as its carcinogenic risk was 1.45 × 10-4 through direct ingestion. Combined risk assessment showed the PTE mixture in surface water and sediment posed medium and high ecological risk with the risk quotient and potential ecological risk index of 1.76 and 558.36, respectively. Adverse health effects through incidental ingestion and dermal contact during swimming were negligible. This study provides a nationwide risk assessment of PTEs in China's aquatic environment and the robustness is verified, which can serve as a practical basis for policymakers to guide the early warning and precise management of water pollution.

Integrated assessment of potentially toxic elements in soil of the Kangdian metallogenic province: A two-point machine learning approach

The accumulation of potentially toxic elements in soil poses significant risks to ecosystems and human well-being due to their inherent toxicity, widespread presence, and persistence. The Kangdian metallogenic province, famous for its iron-copper deposits, faces soil pollution challenges due to various potentially toxic elements. This study explored a comprehensive approach that combinescombines the spatial prediction by the two-point machine learning method and ecological-health risk assessment to quantitatively assess the comprehensive potential ecological risk index (PERI), the total hazard index (THI) and the total carcinogenic risk (TCR). The proportions of copper (Cu), cadmium (Cd), manganese (Mn), lead (Pb), zinc (Zn), and arsenic (As) concentrations exceeding the risk screening values (RSVs) were 15.03%, 5.1%, 3.72%, 1.24%, 1.1%, and 0.13%, respectively, across the 725 collected samples. Spatial prediction revealed elevated levels of As, Cd, Cu, Pb, Zn, mercury (Hg), and Mn near the mining sites. Potentially toxic elements exert a slight impact on soil, some regions exhibit moderate to significant ecological risk, particularly in the southwest. Children face higher non-carcinogenic and carcinogenic health risks compared to adults. Mercury poses the highest ecological risk, while chromium (Cr) poses the greatest health hazard for all populations. Oral ingestion represents the highest non-oncogenic and oncogenic risks in all age groups. Adults faced acceptable non-carcinogenic risks. Children in the southwest region confront higher health risks, both non-carcinogenic and carcinogenic, from mining activities. Urgent measures are vital to mitigate Hg and Cr contamination while promoting handwashing practices is essential to minimize health risks.

Chemical speciation and comprehensive risk assessment of metals in sediments from Nabq protectorate, the Red Sea using individual and synergistic indices

The study evaluates metal concentrations, distributions, contamination, risk, sources, fractionation, and mobility in Nabq Protectorate sediments, revealing a metal content order of Fe, Mn, Pb, Ni, and Cd. Metals are dominated by residual fractions, with Cd (83.70 %) > Ni (82.98 %) > Pb (80.96 %) > Fe (80.31 %) > Mn (76.65 %) reflecting the natural sources of investigated metals. Mn (23.35 %) was the most abundant mobile metal, and the sediments of the protectorate had low toxicity and moderate risk according to the synergistic indices (1 ≤ mRAC<10 and ERM; 5-10). The results from the proposed individual indices showed that Mn, Fe, and Pb are the most bioavailable (BIM 0.1-0.4), Cd, Mn, Ni, Fe, and Pb are of moderate mobility (MIM 0.1-0.4), and Cd is the most available (ARIM 5-10), with Cd posing the most ecological risk. The total hazard quotient (THQ) for child was greater than one, exposure to manganese through ingestion and skin contact while swimming may endanger human health.

Influence of environmental factors on changes in the speciation of Pb and Cr in sediments of Wuliangsuhai Lake, during the ice-covered period

Ecological pollution caused by heavy metals released from sediments is a worldwide concern. However, the effect of changes in sediment speciation on their release of heavy metals has not been adequately reported. In this study, the research focused on Pb and Cr in the ice period of Wuliangsuhai. This study analyzed changes in the sediment speciation of Pb and Cr before and after a release experiment using four risk assessment methods while varying the temperature, pH, and salinity of the water column. The results indicated that the total concentration of Pb ranged from 11.17 to 24.25 mg/kg, while for Cr it ranged from 42.26 to 69.68 mg/kg. Both elements exhibited mild contamination. The release of Pb and Cr from sediments increases with increasing water temperature, mainly due to the conversion of the residual fraction of Pb to the Fe-Mn oxide fraction and Cr converting more residual fraction to the organic matter and sulfide fraction. The release of sediment Pb and Cr decreased with increasing pH, with Pb converting more acid extractable fraction to the residual fraction and Cr converting more organic matter and sulfide fraction to the residual fraction. In contrast, the release of Pb and Cr increased and then decreased with increasing salinity. For Pb, the acid extractable fraction was more susceptible to conversion to the residual fraction by environmental influences, whereas for Cr, the organic matter and sulfide fraction were susceptible to conversion to the residual fraction.

FlowSOM clustering - A novel pattern recognition approach for water research: Application to a hyper-arid coastal aquifer system

Monitoring and understanding of water resources have become essential in designing effective and sustainable management strategies to overcome the growing water quality challenges. In this context, the utilization of unsupervised learning techniques for evaluating environmental tracers has facilitated the exploration of sources and dynamics of groundwater systems through pattern recognition. However, conventional techniques may overlook spatial and temporal non-linearities present in water research data. This paper introduces the adaptation of FlowSOM, a pioneering approach that combines self-organizing maps (SOM) and minimal spanning trees (MST), with the fast-greedy network clustering algorithm to unravel intricate relationships within multivariate water quality datasets. By capturing connections within the data, this ensemble tool enhances clustering and pattern recognition. Applied to the complex water quality context of the hyper-arid transboundary Caplina/Concordia coastal aquifer system (Peru/Chile), the FlowSOM network and clustering yielded compelling results in pattern recognition of the aquifer salinization. Analyzing 143 groundwater samples across eight variables, including major ions, the approach supports the identification of distinct clusters and connections between them. Three primary sources of salinization were identified: river percolation, slow lateral aquitard recharge, and seawater intrusion. The analysis demonstrated the superiority of FlowSOM clustering over traditional techniques in the case study, producing clusters that align more closely with the actual hydrogeochemical pattern. The outcomes broaden the utilization of multivariate analysis in water research, presenting a comprehensive approach to support the understanding of groundwater systems.

The leaching behavior of heavy metal from contaminated mining soil: The effect of rainfall conditions and the impact on surrounding agricultural lands

Contaminated mining soils could lead to heavy metal pollution of surrounding farmlands under rainfall conditions. With the aids of sequential extraction, batch leaching, and dynamic leaching experiments, this study was carried out to investigate the characteristics of heavy metals in contaminated mining soils, understand their leaching behavior under different rainfall conditions, and evaluate the potential effects on surrounding farmlands. The results indicated that the concentrations of heavy metals (Cr, Ni, Cu, Zn, As, Cd, and Pb) in the contaminated mining soils were several or even twenty times higher than their corresponding background values, and Cd, Zn, Cu and Pb had considerable proportions (>50 %) in mobile forms. The leaching amounts of heavy metals from the contaminated mining soils had positive correlation with their contents in acid soluble form, and showed strong dependence on rainfall pH conditions. Acid rainfalls (pH = 4.32) can greatly increase the average annual release of Cd, Zn, Cu and Pb from mine soils in the study area, with increments ranging from 72.4 % (Pb) to 85.9 % (Cd) compared to those under alkaline conditions (pH = 7.42). The leaching of heavy metals was well fitted by two-constant, pseudo second-order and parabolic equations, indicating that their multi-layer sorption/desorption behavior on soil surface was dominated by chemical processes and their release was controlled by the diffusion within the soil pore channels. The two-column leaching experiment showed that the metal-rich leachate can lead to obvious increments of heavy metals in non-residual fractions (in particular Cd in acid soluble form) in surrounding farmlands, which would significantly raise the potential ecological risk associated with heavy metals. These findings indicate the importance of contaminated mining soils as a long-term source of heavy metals and the needs for mitigating the releases of toxic elements, especially in areas with heavy acid precipitation.

Risk assessment and source apportionment of available atmospheric heavy metal in a typical sandy area reservoir in Inner Mongolia, China

This study evaluated dry and wet deposition of atmospheric heavy metals (HMs) in a sandy area of Inner Mongolia, China, with the Dahekou Reservoir, Xilin Gol League, adopted as the study area. Monthly monitoring of atmospheric HM dry and wet deposition was conducted over one year (2021 to 2022) at 12 monitoring points, producing 144 dry and wet deposition samples, respectively. The sample contents of eight HMs (Cr, Ni, Pb, Cu, Zn, Mn, As, and Cd) were determined to estimate the fluxes of available forms of heavy metal (AHM) in dry and wet deposition. The potential ecological index (Eri), risk assessment coding (RAC), and ratio of secondary phase to primary phase (RSP) were used to evaluate the impact of atmospheric HM dry deposition on ecological security. Correlation analysis, principal component analysis, and the absolute principal component scores-multiple linear regression (APCS-MLR) receptor model were used to quantitatively analyze the sources of AHMs in atmospheric dry and wet deposition. The results showed that the study area experienced annual dry and wet deposition fluxes of AHMs of 1712.59 kg and 534.97 kg, respectively. Atmospheric heavy metal dry deposition over the entire year presented a strong ecological risk, with Cd contributing most to this risk. Risk assessment of HM speciation showed that the greatest risks of migration and transformation were for Cd and Pb. The APCS-MLR receptor model identified five and three sources of dry and wet deposition, respectively, in order of proportion of total contribution of: natural wind and sand > road traffic and coal combustion > mineral mining > other human activities > industrial soot.

Risk assessment of heavy metals in agricultural soil based on the coupling model of Monte Carlo simulation-triangular fuzzy number

Soils in areas wherein agriculture and mining coexist are experiencing serious heavy metal contamination, posing a great threat to the ecological environment and human health. In this study, heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) in agricultural soil samples from mining areas were analyzed to explore pollution status, bioavailability, potential sources, and ecological/health risks. Particularly, the coupling model of Monte Carlo simulation-triangular fuzzy number (MCS-TFN) was established to quantify ecological/health risks accurately. Results showed that Cd was heavily enriched in soil and had the highest bioavailability based on both geo-accumulation index (Igeo) and chemical speciation analysis. Pollution sources apportioned with the absolute principal component score-multiple linear regression (APCS-MLR) model demonstrated that heavy metals were mainly derived from agricultural activities, followed by mining activities and natural sources. The MCS-TFN ecological risk assessment classified Cd into the high-risk category with a probability of 40.96%, whereas other heavy metals were categorized as the low risk. Cd was regarded as the major pollutant for the ecosystem. Moreover, the MCS-TFN health risk assessment indicated that As showed high noncarcinogenic risk (0.07% probability) and moderate carcinogenic risk (1.87% probability), and Cd presented low carcinogenic risk (80.19% probability). As and Cd were identified as the main heavy metals that pose a threat to human health. The MCS-TFN risk assessment is superior to the traditional deterministic risk assessment since it can obtain the risk level and the corresponding probability, and significantly reduce the uncertainty in risk assessment.

Quantitative risk analysis of sediment heavy metals using the positive matrix factorization-based ecological risk index method: a case of the Kuye River, China

Identifying the sources of heavy metals (HMs) in river sediments is crucial to effectively mitigate sediment HM pollution and control its associated ecological risks in coal-mining areas. In this study, ecological risks resulting from different pollution sources were evaluated using an integrated method combining the positive matrix factorization (PMF) and the potential ecological risk index (RI) model. A total of 59 sediment samples were collected from the Kuye River and analyzed for eight HMs (Zn, Cr, Ni, Cu, Pb, As, Cd, and Hg). The obtained results showed that the sediment HM contents were higher than the corresponding soil background values in Shaanxi Province. The average sediment Hg content was 3.42 times higher than the corresponding background value. The PMF results indicated that HMs in the sediments were mainly derived from industrial, traffic, agricultural, and coal-mining sources. The RI values ranged from 26.15 to 483.70. Hg was the major contributor (75%) to the ecological risk in the vicinity of the Yanjiata Industrial Park. According to the PMF-based RI model, coal-mining activities exhibited the strongest impact on the river ecosystem (48.79%), followed, respectively, by traffic (34.41%), industrial (12.70%), and agricultural (4.10%) activities. These results indicated that the major anthropogenic sources contributing to the HM contents in the sediments are not necessarily those posing the greatest ecological risks. The proposed integrated approach in this study was useful in evaluating the ecological risks associated with different anthropogenic sources in the Kuye River, providing valuable suggestions for reducing sediment HM pollution and effectively protecting river ecosystems.

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

Riparian soils in the lower sections of the Lhasa River were chosen as the research focus, to examine the characteristics and sources of heavy metals in riparian soils of high-cold regions. To investigate the influence of various factors on the geographical distribution of heavy metals, three horizontal and one vertical profiles were considered. The geoaccumulation index, prospective ecological risk index, and enrichment factor were used to evaluate the extent of soil contamination. Correlation analysis and the positive-matrix-analysis receptor model were used to quantitatively examine the sources of the elements. According to the soil-evaluation, the topsoil was more polluted than the deep soil. Overall, the soil was slightly degraded and posed minor ecological concern. Cd was the primary contributor to the overall contamination, with moderate and considerable risk levels at certain locations. Five sources were identified for the six heavy metals. Transportation and agricultural production were the principal sources of Cd. Ni and Cr were mostly connected to agricultural practices and weathering of parent-soil materials. Pb and Zn were mostly related to geological history, geothermal development, and traffic pollution. Mineral resource development has had a major impact on Cu. Non-carcinogenic risk index of each heavy metal and their total value were <1, indicating they are not harmful to human health. The riparian soil of the Lhasa River Basin contains heavy metals from various sources; therefore, it is important to monitor these heavy metals. This study provides a scientific foundation for the safe utilization and classification of soils in high cold regions.

Quantitative source apportionment of heavy metals in sediments from the Bohai Sea, China

In this study, the sources of nine heavy metals (Cd, As, Hg, Cu, Pb, Ni, Cr, Zn, and Co) in the sediments of the Bohai Sea were quantitatively identified through a positive factor matrix to provide better advice for marine and coastal management. In Bohai Sea sediments, most metals fell below detectable contamination levels, including As, Cu, Pb, Ni, Cr, Zn, and Co. Unfortunately, Bohai Sea sediments were moderately to significantly enrich with Cd and Hg, posing potentially adverse ecological risks to aquatic ecosystems. Our modeled results showed three factors representing natural, anthropogenic, and atmospheric deposition sources. Enriched Cd and Hg were likely derived from anthropogenic activities through river runoff and atmospheric deposition due to adjacent Zn smelting and chlor-alkali production, respectively. The other metals were mainly derived from natural sources.

An integrated overview of metals contamination, source-specific risks investigation in coal mining vicinity soils

Heavy metals in soil are harmful to natural biodiversity and human health, and it is difficult to estimate the effects accurately. To reduce pollution and manage risk in coal-mining regions, it is essential to evaluate risks for heavy metals in soil. The present study reviews the levels of 21 metals (Nb, Zr, Ag, Ni, Na, K, Mg, Rb, Zn, Ca, Sr, As, Cr, Fe, Pb, Cd, Co, Hg, Cu, Mn and Ti) in soils around Barapukuria coal-mining vicinity, Bangladesh which were reported in literature. An integrated approach for risk assessments with the positive matrix factorization (PMF) model, source-oriented ecological and health hazards were applied for the study. The contents of Rb, Ca, Zn, Pb, As, Ti, Mn, Co, Ag, Zr, and Nb were 1.63, 1.10, 1.97, 14.12, 1.20, 3.13, 1.22, 3.05, 3.85, 5.48, and 7.21 times greater than shale value. About 37%, 67%, 12%, and 85% of sampling sites posed higher risks according to the modified contamination factor, Nemerow pollution index, Nemerow integrated risk index, and mean effect range median quotient, respectively. Five probable metal sources were computed, including industrial activities to coal mining (17%), agricultural activities (33%), atmospheric deposition (19%), traffic emission (16%), and natural sources (15%). Modified Nemerow integrated risk index reported that agricultural activities, industrial coal mining activities, and atmospheric deposition showed moderate risk. Health hazards revealed that cancer risk values computed by the PMF-HHR model with identified sources were higher than the standard value (1.0E-04) for children, adult male, and female. Agricultural activities showed higher cancer risks to adult male (39%) and children (32%) whereas traffic emission contributed to female (25%). These findings highlight the ecological and health issues connected to potential sources of metal contamination and provide useful information to policymakers on how to reduce such risks.

Heavy metals pollution of soil in central plains urban agglomeration (CPUA), China: human health risk assessment based on Monte Carlo simulation

The present study conducted the concentration evaluation, pollution assessment, source analysis, and risk assessment of heavy metals in the soil of the CPUA, China, to contribute to the smooth construction of urban agglomeration. Elevated levels of mean concentrations of cadmium (Cd), chromium (Cr), and copper (Cu) in the soils were shown compared to background values. Cu and zinc (Zn) and also lead (Pb) and Cd exhibited spatial similarity. Manganese (Mn) and Cr exhibited point source characteristics such as the concentrations at a point much higher than the surrounding area. The potential ecological risk in the northern region belonged to the moderate risk level category. Cd contributed over 90% to the potential ecological risk. The health risk among children was higher than that among adults. The major exposure pathways were different for adults and children. Exposure, as shown using Hazard Index (HI), to adults was mainly through the skin contact route, while to children was through both the skin contact and ingestion route. The primary CR (carcinogenic risk) to adults was through the inhalation route, while that to children was through the ingestion route. In both children and adults, Cr was the main contributor to HI and CR. According to the Monte Carlo simulation results, the cumulative probability of exceeding the critical value of HI for children was approximately 2.8-3.0 times that for adults. According to the sensitivity analysis results, non-carcinogenic risk prevention should begin mainly by reducing exposure duration and skin contact. The cancer risk may be reduced primarily by decreasing the exposure duration and controlling ingestion. The PMF (Positive Matrix Factorization) source analysis revealed that Pb mainly came from transportation sources. In addition, Cu, Pb, and Mn were derived mainly from agricultural sources. Cr was derived mostly from a natural source, and Cd originated mainly from an industrial source.

Source apportionment of heavy metal(loid)s in sediments of a typical karst mountain drinking-water reservoir and the associated risk assessment based on chemical speciations

As important place for water storage and supply, drinking-water reservoirs in karst mountain areas play a key role in ensuring human well-being, and its water quality safety has attracted much attention. Source apportionment and ecological risks of heavy metal(loid)s in sediments of drinking-water reservoir are important for water security, public health, and regional water resources management, especially in karst mountain areas where water resources are scarce. To expound the accumulation, potential ecological risks, and sources of heavy metal(loid)s in a drinking-water reservoir in Northwest Guizhou, China, the surface sediments were collected and analyzed based on the combined use of the geo-accumulation index (Igeo), sequential extraction (BCR), ratios of secondary phase and primary phase (RSP), risk assessment code (RAC), modified potential ecological risk index (MRI), as well as the positive matrix factorization methods. The results indicated that the accumulation of Cd in sediments was obvious, with approximately 61.9% of the samples showing moderate to high accumulation levels, followed by Pb, Cu, Ni, and Zn, whereas the As and Cr were at low levels. A large proportion of BCR-extracted acid extractable and reducible fraction were found in Cd (72.5%) and Pb (40.3%), suggesting high bioavailability. The combined results of RSP, RAC, and MRI showed that Cd was the major pollutant in sediments with high potential ecological risk, while the risk of other elements was low. Source apportionment results of heavy metal(loid)s indicated that Cd (75.76%) and Zn (23.1%) mainly originated from agricultural activities; As (69.82%), Cr (50.05%), Cu (33.47%), and Ni (31.87%) were associated with domestic sources related to residents' lives; Cu (52.36%), Ni (44.57%), Cr (34.33%), As (26.51%), Pb (24.77%), and Zn (23.80%) primarily came from natural geological sources; and Pb (47.56%), Zn (22.46%) and Cr (13.92%) might be introduced by mixed sources of traffic and domestic. The contribution ratios of the four sources were 18.41%, 36.67%, 29.48%, and 15.44%, respectively. Overall, priority control factors for pollution in relation to agricultural sources included Cd, while domestic sources are primarily associated with As. It is crucial to place special emphasis on the impacts of human activities when formulating pollution prevention and control measures. The results of this study can provide valuable reference and insights for water resources management and pollution prevention and control strategies in karst mountainous areas.

Source identification and health risk assessment of heavy metals with mineralogy: the case of soils from a Chinese industrial and mining city

Understanding the precise sources of heavy metals (HMs) in soil and the contribution of these sources to health risks has positive effects in terms of risk management. This study focused on the HMs in the soil of five land uses in an industrial and mining city. The sources of HMs in soils were identified, and the soil mineralogical characteristics and health risks of HMs were discussed. The results showed that the HMs (Cu, Zn, Ni, Cd, Pb) found in the soil of the five land uses were affected by human activities. For example, the Cu in grassland, gobi beach, woodland, green belt, and farmland is 22.3, 3.5, 22.5, 16.7, and 21.3 times higher than the soil background values in Gansu Province, respectively. The Positive Matrix Factorization model (PMF) results revealed that traffic emissions and industrial and agricultural activities were the primary sources of HMs in the soil, with industrial sources accounting for the largest share at 55.79%. Furthermore, various characteristics proved that the studied HMs were closely related to smelting products. Concentration-oriented health risk assessments showed that HMs in the different soil types held non-carcinogenic and carcinogenic risks for children and adults. Contamination source-oriented health risk assessments of children and adults found that industrial activities controlled non-carcinogenic and carcinogenic risks. This study highlighted the critical effects of smelting on urban soil and the contribution of pollution sources to health risks. Furthermore, this work is significant in respect of the risk control of HMs in urban soils.

Source-oriented risks apportionment of toxic metals in river sediments of Bangladesh: a national wide application of PMF model and pollution indices

Intense human activities, particularly industrial and agricultural output, has enriched metal(loid)s in riverine sediment and endangered aquatic ecosystems and human health. Promoting proper river management requires an assessment of the possible ecological hazards and pollution posed by metal(loid)s in sediments. However, there are limited large-scale risk assessments of metal(loid)s contamination in riverine sediment in heavily populated nations like Bangladesh. This study compiled data on sediment metal(loid)s, for example, Cd, As, Cu, Ni, Cr, Pb, Mn, and Zn, from 24 major rivers located across Bangladesh between 2011 and 2022 and applied positive matrix factorization (PMF) to identify the critical metal(loid)s sources and PMF model-based ecological risks. Based on studied metal(loid)s, 12-78% of rivers posed higher contents than the upper continental crust and 8% of the river sediments for Cr and Ni, whereas 4% for Cd and As exceeded probable effect concentration. Cr and Ni in the sum of toxic units (STU), whereas Mn, As and Cd in potential ecological risk (PER) posed the highest contribution to contaminate sediments. In the studied rivers, sediment contaminant Mn derived from natural sources; Zn and Ni originated from mixed sources; Cr and Cu were released from the tannery and industrial emissions and Cd originated from agricultural practices. Source-based PER and NIRI indicated that mixed source (4% rivers) and tannery and industrial emission (4% rivers) posed very high risks in sediments. For the creation of macroscale policies and the restoration of contaminated rivers, our national-scale comprehensive study offers helpful references.

Geochemical fractionation, mobility of elements and environmental significance of surface sediments in a Tropical River, Borneo

Miri River is a tropical river in Borneo that drains on flat terrain and urbanised area and debauches into the South China Sea. This paper documents the environmental status of this river, and provides an insight into the provenance using bulk chemistry of the sediments, and brings out the geochemical mobility, bioavailability, and potential toxicity of some critical elements based on BCR sequential extraction. The sediments are intense to moderately weathered and recycled products of Neogene sedimentary rocks. The hydrodynamic characteristics of the river favoured an upstream section dominated by fine sand, while the downstream sediments are medium silt. Based on the bulk geochemistry, the Miri River sediments are moderate to considerably contaminated by Cu, Mo, and As in the upstream and by Sb, As and Cu in the downstream. The potential ecological risk values are low except Cu and a significant biological impact is expected in downstream due to Cu, As, Zn and Cr. The mobility, bioavailability and Risk Assessment Code values for Zn and Mn are higher and thus may pose moderate to very high risk to aquatic organisms. Though a high bulk concentration of Cu is observed, the association of Cu with the bioavailable fraction is low.

New insight into the geochemical mechanism and behavior of heavy metals in soil and dust fall of a typical copper smelter

The desorption mechanism of heavy metals (HMs) in soil around the mining region are complex and affected by multiple pollution sources, including sewage discharge and atmospheric deposition. Meanwhile, pollution sources would change soil physical and chemical properties (mineralogy and organic matter), thus affecting the bioavailability of HMs. This study aimed to investigate the pollution source of HMs (Cd, Co, Cu, Cr, Mn, Ni, Pb, and Zn) in soil near mining, and further evaluate influence mechanism of dust fall on HMs pollution in soil by desorption dynamics processes and pH-dependence leaching test. Result presented that dust fall is the primary pollution source to HMs accumulation in soil. Additionally, the result of mineralogical analysis in dust fall revealed that quartz, kaolinite, calcite, chalcopyrite, and magnetite are the major mineralogical phases by XRD and SEM-EDS. Meanwhile, the abundance of kaolinite and calcite in dust fall is higher than in soil, which is the primary reason of higher acid-base buffer capacity of dust fall. Correspondingly, the weakened or disappeared of hydroxyl after the adding acid extraction (0-0.4 mmol· g-1) demonstrated that hydroxyl is the main participants of HMs absorption in soil and dust fall. These combined findings suggested that atmospheric deposition not only increases the pollution loading of HMs in soil, but also changes the mineral phase composition of soil, which would increase the adsorption capacity and bioavailability of HMs in soil. This is very remarkable that heavy metals in soil influenced by dust fall pollution could be released preferentially when soil pH is changed. The present results of this study would provide efficient and scientific targeted strategies for pollution control of HMs in soil near mining areas.

Risk assessment and source apportionment for metals in sediments of Kaptai Lake in Bangladesh using individual and synergistic indices and a receptor model

Metal enrichment in lake sediments originating from multiple sources can threaten both the aquatic ecosystem and human health. Therefore, assessment of the eco-environmental risks and potential sources of metals in the sediments is essential for effective lake management. Here, we analyzed the sediment metal contents of Kaptai Lake, the largest lake in Bangladesh for the first time with this study. The results indicated that only Cr and Ni contents among the metals studied exceeded the probable effect concentrations (PEC) at 25.42 % and 55.93 % of the sampling stations, respectively. All metals at most sampling stations showed low contamination and low ecological risk based on the individual indices (geoaccumulation index, contamination factor, ecological risk factor, enrichment factor and modified hazard quotient). There was no significant risk from the combined metals in the sediments of the lake according to the synergistic indices (toxic risk index, Nemerow risk index, ecological risk index, Nemerow pollution index and pollution load index). Organic matter and silt were significant sediment parameters that favored the accumulation of Cr, Fe, Cu, Pb and Mn. In the absolute principle component scores-multiple linear regression model (APCS-MLR), five potential sources of metals were identified in the sediments: Zn, Mn, Co and Cd mainly from natural sources and to a lesser extent from agricultural and aquacultural activities, Ni, Cr and Fe from parent materials, Pb and Cu mainly from natural sources and to a lesser extent from vehicle emissions, Hg and U from lithogenic sources, and As from natural sources. This study will improve our knowledge of the sedimentary metal contents of Kaptai Lake and provide helpful information for developing effective lake management and pollution control strategies.

A novel pollution index to assess the metal bioavailability and ecological risks in sediments

The chemical forms of metals in sediments of ports around Taiwan were investigated using sequential extraction. Based on the availability of different chemical forms, novel indices such as bioavailability, mobility, availability, and availability risk of metals in sediments were developed. The results showed that Co, Zn, Pb, Mn, and Cu were mainly present in available forms (49-84 %), and the proportion of oxidative or reductive fractionation was the highest. This suggests that the redox potential is a major factor for metal mobility in the sediments. The results from the proposed indexes showed that metals in sediments have low bioavailability but high to very high mobility and availability. Primarily, the proposed index is more appropriate, as the current index for assessing total metal content may overestimate the level of risk. The indexes established can comprehensively evaluate the bioavailability, mobility, availability, and ecological risk of metals in sediments.

Ecological and health risk assessment and quantitative source apportionment of dissolved metals in ponds used for drinking and irrigation purposes

In this study, dissolved metal levels of 10 different ponds used as irrigation and drinking water sources in the north of Saros Bay (Türkiye) were evaluated using multivariate statistical methods, contamination and ecological risk indices, and absolute principal component score-multiple linear regression (APCS-MLR). The mean levels of metals in the ponds ranged from 0.045 µg/L (Cd) to 127 µg/L (Mn). Pond 7 used for drinking water source had the lowest total metal level. Only Mn levels in two ponds (P1 and P2) slightly exceeded the critical value set by EU Drinking Water Directive. However, the levels of all metals in all ponds were lower than the critical values set for irrigation water and aquatic life. According to the heavy metal pollution index (HPI), five ponds showed low metal pollution in terms of drinking water quality, four ponds showed moderate metal pollution, and one pond (P1) showed moderate to heavy pollution. According to the Nemerow pollution index (NPI) values (0.26-1.82), ponds P1 and P2 showed slight metal pollution, while other ponds showed insignificant metal pollution. Contamination degree (CD) values of ponds varied between 0.95 and 3.33, indicating that all ponds showed low pollution. In terms of irrigation water quality, all ponds showed low or insignificant metal pollution according to the HPI, NPI, and CD values. According to the ecological risk index (ERI) values, metals in all ponds posed low ecological risks for both drinking and irrigation purposes. Factor analysis identified two potential sources: mixed sources and natural sources. The APCS-MLR model results revealed that mixed sources and natural sources contributed 78.99% and 21.01% to dissolved metals in the ponds, respectively. Health risk assessment results indicated that both individual and combined metals in the ponds would not cause non-carcinogenic risks to both adults and children. Similarly, it was found that Cr and As would not cause carcinogenic risks to the residents of the region.

Metal-mining-induced sediment pollution presents a potential ecological risk and threat to human health across China: A meta-analysis

Aquatic sediment polluted by potentially toxic elements (PTEs) from mining activities represents a potential health "time bomb" for humans and the local ecology, but the integrated analysis of pollution and hazards of PTEs in sediment around typical metal mines in China is limited. Presently, the associated pollution status, spatial distribution, and ecological and health hazards of Cd, Cu, Zn, Pb, Cr, and As were investigated through index evaluation, spatial analysis, health risk assessment models, and Monte Carlo simulation. Overall, the sediment exhibited varying degrees of PTE contamination; notably, the level of Cd was 104.85 times higher than its background value, and it became the most enriched element in the surveyed sediment, followed in descending order by Cu, As, Zn, Pb, and Cr. Nationally, over 64.5% of metal-mining-affected sediment presented a very high ecological risk, contributed mostly by Cd (43.2%-98.7%) followed by As, Pb, and Cu; the risk contributed by both Cr and Zn was found to be negligible. The adverse health risk posed to children by most sediment was 1.72 and 6.46 times higher than that posed to adults for cancerous and noncancerous risks, respectively. The potential noncarcinogenic risks were mainly caused by As, which contributed over 78.9% of the Hazard Index values, then followed by Pb (>9.3%). For both children and adults, the carcinogenic risk of PTEs decreased in the following order: As > Cd > Cr > Pb. The investigated sediment was found seriously affected by nearby metal mines, especially those in regions with long-term and large-scale nonferrous-metal-mining activities. This study could provide a reference for policymakers to develop control strategies for PTE pollution in sediment around mining areas.

Trace elements in surface sediments from Xinyanggang River of Jiangsu Province, China: Spatial distribution, risk assessment and source appointment

The Xinyanggang River in Yancheng City, one of the essential rivers entering the Yellow sea, has imported abundant pollutants to the coast of Jiangsu Province. Trace elements (Cr, Ni, Cu, Zn, As, Rb, Sr, Mo, Pb, Th, U, Sc, Ga, Se, Zr, Nb, and Sn) in surface sediments in the Xinyanggang River were measured to analyze the spatial distribution, risk assessment, and source appointment. The results showed that the parts of 17 trace elements presented high average values in river sediments, such as Zr (309.19 mg/kg), Sr (182.72 mg/kg), Zn (77.67 mg/kg), and Cr (70.63 mg/kg). Compared with some coastal rivers, the Xinyanggang River was polluted by certain trace elements, such as Cr, Zn, and As. Based on the analysis of the enrichment factor (EF), the contamination factor (CF), the pollution load index (PLI), and the geoaccumulation index (I_geo), trace elements in sediments showed unpolluted to moderate contamination and mild to moderate enrichment. Among them, Zn, Pb, and Sn were highly polluted. The multivariate analysis, the principal component analysis-multiple linear regression (APCS-MLR) model, and the Unmix model identified four contributing trace element sources. Cr, Th, U, Se, Zr, and Nb originated from manufacturing industries and hydrodynamic transport erosion. Ni, Rb, Sc, and Ga were attributed to natural source. Cu, Zn, Mo, Pb, and Sn were contributed from mixed sources including industrial wastewater and transportation emissions. As and Sr were associated mainly with mixed sources of agriculture and combustion. These four sources of metals accounted for 22.5 %, 5.7 %, 15.3 %, and 11.1 % by using the APCS-MLR model, whereas 22.9 %, 39.7 %, 17.5 %, and 19.9 % by using the Unmix model, respectively.

Construction of WO3 nanocubes@Loess for rapid photocatalytic degradation of organics in wastewater under sunlight

In nowadays, environmental pollution has been greatly improved, but the development of low-cost and environmentally friendly materials are still challenge in the field of water treatment. Herein, a cheap and eco-friendly natural loess particle (LoP) was used for in situ growth of tungsten trioxide nanocubes (WO3NCs) on its surface via a simple one-pot hydrothermal method, which afforded a stable loess-based photocatalyst (WO3NCs@LoP). It was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) analysis, UV-Vis diffuse reflectance spectra (UV-Vis DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic performances of WO3NCs@LoP were applied to photodegradation of organics under visible-light illumination. It was found that the removal rate of methylene blue (MB) got to 99% within 20 min, which was higher than that of materials, such as pure LoP and WO3NCs. Moreover, the photocatalytic activity of WO3NCs@LoP remained 85% after 9 cycling times, indicating its high stability and reusability. It was suggested that the synergy of the well narrowed band gap and effectual control of e--h+ recombination in WO3NCs@LoP improve its photodegradation efficiency. In summary, using natural minerals (LoP) as carrier, a novel eco-friendly photocatalyst could be explored for photodegradation of organic pollutions in wastewater treatment.

Contamination, Source Apportionment, and Health Risk Assessment of Heavy Metals in Farmland Soils Surrounding a Typical Copper Tailings Pond

Tailings resulting from mining and smelting activities may cause soil heavy-metal pollution and harm human health. To evaluate the environmental impact of heavy metals from tailings on farmland soils in the surrounding area, heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) in tailings and farmland soils in the vicinity of a typical copper tailings pond were analyzed. Contamination status, potential sources, and health risks for farmland soils were investigated. The results showed that the tailings contained a high concentration of Cu (1136.23 mg/kg). The concentrations of Cd and Cu in the farmland soils exceeded the soil quality standard. The geoaccumulation index (I_geo) indicated that the soils were moderately polluted by Cu and Cd, and slightly polluted by Ni, Cr, and Zn. The absolute principal component scores-multiple linear regression (APCS-MLR) model was applied for source apportionment. The results showed that tailings release is the main source of soil heavy-metals contamination, accounting for 35.81%, followed by agricultural activities (19.41%) and traffic emission (16.31%). The health risk assessment suggested that the children in the study region were exposed to non-carcinogenic risks caused by As, while the non-carcinogenic risk to adults and the carcinogenic risk to both adults and children were at acceptable levels. It is necessary to take effective measures to control heavy-metal contamination from tailings releases to protect humans, especially children, from adverse health risks.

The Predominant Sources of Heavy Metals in Different Types of Fugitive Dust Determined by Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) Modeling in Southeast Hubei: A Typical Mining and Metallurgy Area in Central China

To develop accurate air pollution control policies, it is necessary to determine the sources of different types of fugitive dust in mining and metallurgy areas. A method integrating principal component analysis and a positive matrix factorization model was used to identify the potential sources of heavy metals (HMs) in five different types of fugitive dust. The results showed accumulation of Mn, Fe, and Cu can be caused by natural geological processes, which contributed 38.55% of HMs. The Ni and Co can be released from multiple transport pathways and accumulated through local deposition, which contributed 29.27%. Mining-related activities contributed 20.11% of the HMs and showed a relatively high accumulation of As, Sn, Zn, and Cr, while traffic-related emissions contributed the rest of the HMs and were responsible for the enrichment in Pb and Cd. The co-applied source-identification models improved the precision of the identification of sources, which revealed that the local geological background and mining-related activities were mainly responsible for the accumulation of HMs in the area. The findings can help the government develop targeted control strategies for HM dispersion efficiency.

Hydrogeochemical and health risk assessment in and around a Ramsar-designated wetland, the Ganges River Basin, India: Implications for natural and human interactions

Wetlands are the most productive and dynamic ecosystems, which have continuously been influenced by social and economic development. As a result, the pollution of wetland surface water and groundwater in adjacent regions has become an emerging global issue that requires constant monitoring and assessment. The current study investigates the natural and anthropogenic processes that influence surface and groundwater chemistry in and around Saman wetland (a Ramsar site) in the Ganges River Basin, India. Various physicochemical parameters are analyzed, and different hydrochemical indices are utilized to evaluate surface and groundwater quality for domestic and irrigation purposes. It is observed that the waters are alkaline in nature and dominated by moderately hard to hard types. An increase in the concentration of nitrate (NO₃^-) in Saman wetland water is noted, which is possibly due to the leaching of nitrogen ions primarily from fertilizers, pesticides, animal and human waste, and wastewater drained from brick and other factories. The elevated fluoride (F^-) content in studied groundwater samples is mainly governed by geogenic processes. Furthermore, surface and groundwater chemistry are mainly controlled by weathering reaction (rock-water interaction), excluding a few wetland surface water samples that are placed outside the boomerang-shaped boundaries of Gibb's diagram, which suggests evaporated dominance. Water Quality Index (WQI) estimation suggests that around 57% of groundwater samples have poor groundwater quality for drinking purposes. Estimation of irrigation water quality indices suggests that surface water of Saman wetland is permissible for irrigation purposes; however, none of the samples have excellent and good class as per sodium (alkali) hazard. Furthermore, health risk assessment showed that NO₃^- and F^- levels in the groundwater pose noncarcinogenic health effects, preferably to children, and thus is unfit for drinking purposes. For long-term water resource management and conservation of the Saman wetland, this study suggests proper awareness, appropriate remedial measures, and regular monitoring of the surface as well as groundwater quality monitoring in the study region.