Environmental contamination and health risk assessment of potentially toxic trace metal elements in soils near gold mines - A global meta-analysis

Effectiveness of cork and pine bark powders as biosorbents for potentially toxic elements present in aqueous solution

Cork oak and pine bark, two of the most prolific byproducts of the European forestry sector, were assessed as biosorbents for eliminating potentially toxic elements (PTEs) from water-based solutions. Our research suggests that bioadsorption stands out as a viable and environmental eco-friendly technology, presenting a sustainable method for the extraction of PTEs from polluted water sources. This study aimed to evaluate and compare the efficiency of cork powder and pine bark powder as biosorbents. Specifically, the adsorption of Fe, Cu, Zn, Cd, Ni, Pb and Sn at equilibrium were studied through batch experiments by varying PTEs concentrations, pH, and ionic strength. Results from adsorption-desorption experiments demonstrate the remarkable capacity of both materials to retain the studied PTE. Cork powder and pine bark powder exhibited the maximum retention capacity for Fe and Cd, while they performed poorly for Pb and Sn, respectively. Nevertheless, pine bark showed a slightly lower retention capacity than cork. Increasing the pH resulted in cork showing the highest adsorption for Zn and the lowest for Sn, while for pine bark, Cd was the most adsorbed, and Sn was the least adsorbed, respectively. The highest adsorption of both materials occurred at pH 3.5-5, depending on the PTE tested. The ionic strength also influenced the adsorption of the various PTEs for both materials, with decreased adsorption as ionic strength increased. The findings suggest that both materials could be effective for capturing and eliminating the examined PTEs, albeit with different efficiencies. Remarkably, pine bark demonstrated superior adsorption capabilities, which were observed to vary based on the specific element and the experimental conditions. These findings contribute to elucidating the bio-adsorption potential of these natural materials, specifically their suitability in mitigating PTEs pollution, and favoring the recycling and revalorization of byproducts that might otherwise be considered residue.

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.

Determining priority control toxic metal for different protection targets based on source-oriented ecological and human health risk assessment around gold smelting area

Determining the priority control source and pollutant is the key for the eco-health protection and risk management around gold smelting area. To this end, a case study was conducted to explore the pollution characteristics, source apportionment, ecological risk and human health risk of toxic metals (TMs) in agricultural soils surrounding a gold smelting enterprise. Three effective receptor models, including positive matrix factorization model (PMF), ecological risk assessment (ERA), and probabilistic risk assessment (PRA) have been combined to apportion eco-human risks for different targets. More than 95.0% of samples had a Nemerow pollution index (NPI) > 2 (NPImean=4.27), indicating moderately or highly soil TMs contamination. Four pollution sources including gold smelting activity, mining source, agricultural activity and atmosphere deposition were identified as the major sources, with the contribution rate of 17.52%, 44.16%, 13.91%, and 24.41%, respectively. For ecological risk, atmosphere deposition accounting for 30.8% was the greatest contributor, which was mainly loaded on Hg of 51.35%. The probabilistic health risk assessment revealed that Carcinogenic risks and Non-carcinogenic risks of all population were unacceptable, and children suffered from a greater health risk than adults. Gold smelting activity (69.2%) and mining source (42.0%) were the largest contributors to Carcinogenic risks and Non-carcinogenic risks, respectively, corresponding to As and Cr as the target pollutants. The priority pollution sources and target pollutants were different for the eco-health protection. This work put forward a new perspective for soil risk control and management, which is very beneficial for appropriate soil remediation under limited resources and costs.

Pollution levels and probability risk assessment of potential toxic elements in soil of Pb-Zn smelting areas

Soil pollution around Pb-Zn smelters has attracted widespread attention around the world. In this study, we compiled a database of eight potentially toxic elements (PTEs) Pb, Zn, Cd, As, Cr, Ni, Cu, and Mn in the soil of Pb-Zn smelting areas by screening the published research papers from 2000 to 2023. The pollution assessment and risk screening of eight PTEs were carried out by geo-accumulation index (Igeo), potential ecological risk index (PERI) and health risk assessment model, and Monte Carlo simulation employed to further evaluate the probabilistic health risks. The results suggested that the mean values of the eight PTEs all exceeded the corresponding values in the upper crust, and more than 60% of the study sites had serious Pb and Cd pollution (Igeo > 4), with Brazil, Belgium, China, France and Slovenia having higher levels of pollution than other regions. Besides, PTEs in smelting area caused serious ecological risk (PERI = 10912.12), in which Cd was the main contributor to PREI (86.02%). The average hazard index (HI) of the eight PTEs for adults and children was 7.19 and 9.73, respectively, and the average value of total carcinogenic risk (TCR) was 4.20 × 10-3 and 8.05 × 10-4, respectively. Pb and As are the main contributors to non-carcinogenic risk, while Cu and As are the main contributors to carcinogenic risk. The probability of non-carcinogenic risk in adults and children was 84.05% and 97.57%, while carcinogenic risk was 92.56% and 79.73%, respectively. In summary, there are high ecological and health risks of PTEs in the soil of Pb-Zn smelting areas, and Pb, Cd, As and Cu are the key elements that cause contamination and risk, which need to be paid attention to and controlled. This study is expected to provide guidance for soil remediation in Pb-Zn smelting areas.

Systematic review of alternative materials that improve retention of potentially toxic metals in soil/clay liners in waste disposal areas

When soils available for the construction of liners do not display the characteristics necessary for a good performance, mixtures with other materials can be employed for achieving the desired quality. Several researchers have addressed those mixtures from either a geotechnical or a gas diffusion perspective, emphasizing low hydraulic conductivity. However, in recent years, growing attention has been drawn to the ability of liners to mitigate contamination. The literature lacks studies on the use of amendments for soil liners or cover systems to retain potentially toxic metals, which are important inorganic contaminants. This paper provides a systematic review of the literature considering publications available on Web of Science and SpringerLink databases between January 1st, 2012, and December 5th, 2022. The aim of the review was to identify the types of soils and amendments studied as liners or cover systems for such retention of potentially toxic metals, the methodologies of application of the alternative materials in the soils, and the research gaps and perspectives in the field. Seventeen papers that addressed 31 materials as amendments were retrieved. The most studied amendment was coal fly ash, and 17 amendments were residues or by-products, which indicates concerns over waste destination and sustainability. Among the potentially toxic metals analyzed are Pb, Cu, and Cd. Gaps such as lack of pilot, field-scale, and long-term studies, as well as perspectives for future research (e.g., different liner configurations, concomitant mixtures of two or more materials in the soil, and focus on the sustainability of amendments), were identified.

Contamination and health risk assessment of heavy metals in soil surrounding an electroplating factory in JiaXing, China

A total of 30 samples from the downwind direction of a certain electroplating company in Jiaxing were collected in layers to analyze their heavy metal content. The soil risk assessment was conducted from the perspective of ecological and human health risks using the ground accumulation index method and human health risk assessment method. The results showed that in all samples, cadmium and arsenic far exceeded the soil background values, with an average exceeding multiple of 14.31 and 64.42, respectively, and a exceeding rate of 100%. After evaluation by the ground accumulation index, among these six heavy metals, arsenic and cadmium belong to extremely serious pollution levels. The human health risk assessment of electroplating plants found that in the exposure risk assessment, the ingestion value was much greater than the harm caused by breathing and skin, and the maximum exposure damage value of arsenic to children and adults was 4.17 × 10-3, among the carcinogenic risks, the risk brought by consumption is much greater than the respiratory and skin carcinogenic risk index, with the highest value score of 3.37 for cadmium, arsenic, and zinc carcinogenic risks 3.37 × 10-6, 2.42 × 10-3, 1.10 × 10-4.

Ecological and health risk assessment of heavy metals in agricultural soils from northern China

Soil pollution by heavy metals can cause continuing damage to ecosystems and the human body. In this study, we collected nine fresh topsoil samples and 18 maize samples (including nine leaf samples and nine corn samples) from agricultural soils in the Baiyin mining areas. The results showed that the order of heavy metal concentrations (mg/kg) in agricultural soils was as follows: Zn (377.40) > Pb (125.06) > Cu (75.06) > Ni (28.29) > Cd (5.46) > Hg (0.37). Cd, Cu, Zn, and Pb exceeded the Chinese risk limit for agricultural soil pollution. The average the pollution load index (4.39) was greater than 3, indicating a heavy contamination level. The element that contributed the most to contamination and high ecological risk in soil was Cd. Principal component analysis (PCA) and Pearson's correlation analysis indicated that the sources of Ni, Cd, Cu, and Zn in the soil were primarily mixed, involving both industrial and agricultural activities, whereas the sources of Hg and Pb included both industrial and transportation activities. Adults and children are not likely to experience non-carcinogenic impacts from the soil in this region. Nonetheless, it was important to be aware of the elevated cancer risk presented by Cd, Pb, and especially Ni. The exceedance rates of Cd and Pb in corn were 66.67% and 33.3%, respectively. The results of this research provide data to improve soil protection, human health monitoring, and crop management in the Baiyin district.

Association between mixed urinary metal exposure and liver function: analysis of NHANES data

Metals have been reported to affect liver functions; however, the association between mixed metal exposure in the urine and liver functions remains unclear. The present study analyzed data from the National Health and Nutrition Examination Survey (NHANES) program collected in 2005-2018. Weighted multiple linear regression and Bayesian kernel machine regression (BKMR) were used to explore the relationship between mixed urinary metal contents and liver function tests (LFTs). A total of 8158 participants were analyzed in this study. Multiple methods suggested that cadmium (Cd) was significantly positively related to LFTs, while cobalt (Co) was negatively related to LFTs. Meanwhile, some other metals showed a significant relationship with some indicators of LFTs. Urine metal is related to LFTs, with Cd and Co content changes being closely related to LFTs. The metal in urine may represent a marker for predicting liver dysfunction. Further studies are needed to verify this hypothesis.