Soil Potentially Toxic Elements Concentrations Research Articles

Assessing soil contamination by potentially toxic elements in artisanal and small-scale gold mining sites of the Adamawa Region, Cameroon

Gold mining is acknowledged as a principal source of environmental contamination, primarily due to the release of potentially toxic elements (PTEs) through tailings dispersion into adjacent soils. Such contamination leads to land degradation, pollution, biodiversity loss, and soil contamination, and subsequently impacts the food chain, human health, and soil ecosystems. This study evaluates the extent of PTE contamination in soils at artisanal and small-scale gold mining (ASGM) sites within the Meiganga area of the Adamawa-Yade Domain, Cameroon. ASGM extraction processes from quartz veins in this area involve the removal of topsoil to access the ore. Comparative analysis of soil samples from three profiles within the mining zone were conducted to determine contamination levels using pollution indices: enrichment factor, geoaccumulation index, contamination factor and pollution load index. Results indicate higher concentrations of PTEs in soils from the mining area compared to the control profile, with notable contamination in the bottom slope profiles and B horizons, reflecting considerable metal accumulation. The contamination levels of PTEs substantially exceed background levels in the upper continental crust. The study attributes the elevated concentrations of PTEs not only to local mineralization but also to anthropic activities, particularly ASGM, which contributes to their enrichment, distribution, and mobility. This pronounced contamination necessitates immediate intervention, advocating for pollution control measures to address potential ecosystem and human health risks. It highlights the environmental toll of ASGM and underscores the imperative for sustainable mining practices and effective soil remediation techniques, including phytoremediation and soil replacement, to alleviate the adverse effects. Supplementary material: https://doi.org/10.6084/m9.figshare.c.7195773

Effect of parent material and atmospheric deposition on the potential pollution of urban soils close to mining areas

The aim of this study is to analyse the concentration and determine the sources of potentially toxic elements (PTEs) in urban soils under the influence of mining activities. To this end, topsoil samples were collected in the public parks and green areas in Minas de Riotinto (a town next to one of the largest open pit mines in the world) and Aracena (a nearby town outside the area of influence of the mine). After determining the concentrations of elements of interest Cr, Co, Ni, Cu, Zn, As, and Pb— the values were compared in terms of the soil location and origin (in-situ or ex-situ), and with the background and regulatory levels for the region. The elemental concentrations in the fine fraction of the soils (particles <50 μm) were also measured. The concentrations of some PTEs (Cu, As and Pb), also found in the dust from nearby mines, were higher in the in-situ soils of Minas de Riotinto than in those of Aracena. The concentrations of PTEs in ex-situ soils of both towns were much lower than in in-situ soils, and similar between the two locations, revealing the influence of the parent material as a primary source of PTEs. However, the concentrations of As and Cu in the ex-situ soils of Minas de Riotinto were significantly higher than in those of Aracena, while a significant increase of these elements in the fine fraction was seen for both in-situ and ex-situ soils. These two elements are directly related to mining activity, implying that atmospheric deposition of dust from the mines contributes to the greater concentration of PTEs in the soils of Minas de Riotinto. Because these sources lead to soils with potentially dangerous concentrations of pollutants, they should be further studied in relation to their long-term influence on human health.

Assessment of potential exposure to As, Cd, Pb and Zn in vegetable garden soils and vegetables in a mining region

Mining and smelting activities can contaminate soils and affect farming due to high emissions and input of potentially toxic elements (PTE) into the environment. Soils (sampled from two depths) and market vegetables from vegetable gardens located within the vicinity of unconfined slag deposits from decades of mining and smelting activities in Kutná Hora, Czechia were assessed to determine to what extent they pose a health hazard to communities that use these gardens. Pseudo-total As concentrations in the soils exceeded background levels (4.5 mg kg−1) 1.9–93 times, with higher concentrations in the deeper layer. The pseudo-total concentrations of PTE in soils ranked in the order As > Zn > Cd > Pb. Phyto-available concentrations of PTE in soils were relatively low, compared to pseudo-total concentrations. Concentration of As, Cd, Pb and Zn in the vegetables exceeded guideline values, with the highest concentrations found in the fruits of cucumber, peppers, and zucchini. Despite low phyto-available PTE concentrations in soils, all the PTE concentrations in the vegetables surpassed the guidelines set by the Czech Ministry of Health and EU directive, indicating a health hazard to consumers.

Modeling and Assessing the Spatial and Vertical Distributions of Potentially Toxic Elements in Soil and How the Concentrations Differ.

A healthy soil is a healthy ecosystem because humans, animals, plants, and water highly depend upon it. Soil pollution by potentially toxic elements (PTEs) is a serious concern for humankind. The study is aimed at (i) assessing the concentrations of PTEs in soils under a long-term heavily industrialized region for coal and textiles, (ii) modeling and mapping the spatial and vertical distributions of PTEs using a GIS-based ordinary kriging technique, and (iii) identifying the possible sources of these PTEs in the Jizerské Mountains (Jizera Mts.) using a positive matrix factorization (PMF) model. Four hundred and forty-two (442) soil samples were analyzed by applying the aqua regia method. To assess the PTE contents, the level of pollution, and the distribution pattern in soil, the contamination factor (CF) and the pollution load index load (PLI) were applied. ArcGIS-based ordinary kriging interpolation was used for the spatial analysis of PTEs. The results of the analysis revealed that the variation in the coefficient (CV) of PTEs in the organic soil was highest in Cr (96.36%), followed by Cu (54.94%) and Pb (49.40%). On the other hand, the mineral soil had Cu (96.88%), Cr (66.70%), and Pb (64.48%) as the highest in CV. The PTEs in both the organic soil and the mineral soil revealed a high heterogeneous variability. Though the study area lies within the “Black Triangle”, which is a historic industrial site in Central Europe, this result did not show a substantial influence of the contamination of PTEs in the area. In spite of the rate of pollution in this area being very low based on the findings, there may be a need for intermittent assessment of the soil. This helps to curtail any excessive accumulation and escalation in future. The results may serve as baseline information for pollution assessment. It might support policy-developers in sustainable farming and forestry for the health of an ecosystem towards food security, forest safety, as well as animal and human welfare.

Background concentrations and quality reference values for potentially toxic elements in soils of Piauí state, Brazil.

The background concentration of potentially toxic elements (PTE) in soils is influenced by the parent material composition and soil forming processes. The soil natural concentration of PTE is a first step to establish regulatory levels for the monitoring of these elements in soils suspected of contamination. In the present study, we performed a natural background concentration survey of PTE in soils of the Piauí state, Brazil. The study provides the basis for establishing soil quality reference values (QRVs) for a large area (over 251,000km2) with different pedological features. A total of 262 geo-referenced soil samples (0.0-0.2m) were collected in areas relatively undisturbed by human activity. The concentrations of Ba, Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb, Sb, V, and Zn were determined by ICP-OES. Univariate statistical methods and multivariate exploratory techniques were used to understand the relationship between soil characteristics, geological features, and PTE concentrations in soils. The mean background concentrations of PTE in the soils were generally lower than those reported in other countries and/or other Brazilian states, and followed the order: Fe > Ba > V > Cr > Cu > Pb > Zn > Ni > Pb > Co > Mo > Sb > Cd. The main factors governing the concentrations of PTE in soils were the parent material and the soil texture. The different geological features in the study area influenced the spatial distribution of PTE and divided the state into three regions presenting low, high, and intermediate values. Given this geological and pedological complexity, we proposed establishing three sets of QRV rather than a single QRV for the whole state to avoid misinterpretation regarding the investigation of areas suspected of contamination. This background concentration survey contains a wealth of information that provides the basis for the soil guideline values in the state and supports future research on the impact of anthropogenic activities in soil contamination.

Distribution of potentially toxic soil elements along a transect across Kazakhstan

The present study aims to investigate the distribution of selected potentially toxic elements (PTEs) in Kazakhstan's topsoils. Soil samples collected across a north-south gradient (n = 40) near main highways connecting major residential/industrial areas were characterized for their As, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn content as well as for soil physio-chemical properties. The majority of the soils had neutral pH (no significant relationship between pH and PTE concentrations). The soil organic carbon was higher at the northern and farther southern parts of the transect (along with higher concentrations of PTEs in soils). As, Mn, and Ni concentrations in soils were elevated in comparison to relevant background concentrations. Critical concentrations of As, Cd, Co, Mn, and Ni (with respect to regulatory limits) were found at multiple locations, with As being particularly of potential concern (range: 8.7–42 mg × kg−1). The distance from the nearest settlement seems to influence the soil PTE concentrations, however the relationship is not statistically significant. In total, eight locations had statistically outlier PTE concentrations for Cd, Mn, Ni, and Zn. The overall results were comparable to similar studies across the world except that the Pb content of the study soils was less elevated. Studies on site characterization and human health risk assessment covering identified hotspots and PTEs are recommended.

Potentially toxic elements in soil ofthe Khyber Pakhtunkhwa province and Tribal areas, Pakistan: evaluation for human and ecological risk assessment.

Potentially toxic elements (PTEs) contaminations in the soil ecosystem are considered as extremely hazardous due to toxicity, persistence and bioaccumulative nature. Therefore, this study was aimed to summarize the results of published PTEs in soil of Khyber Pakhtunkhwa and Tribal areas, Pakistan. Results were evaluated for the pollution quantification factors, including contamination factor (CF), pollution load index (PLI), ecological risk index (ERI) and human health risk assessment. The highest CF (797) and PLI (7.35) values were observed for Fe and ERI (857) values for Cd. Soil PTEs concentrations were used to calculate the human exposure for the risk assessment, including chronic or non-carcinogenic risks such as the hazard quotient (HQ) and carcinogenic or cancer risk (CR). The values of HQ were > 1 for the Cd, Co and Cr in Khyber Pakhtunkhwa and Tribal areas. Tribal areas showed higher values of ERI, HQ, and CR as compared to the Khyber Pakhtunkhwa that were attributed to the mining activities, weathering and erosion of mafic and ultramafic bedrocks hosting ophiolites. This study strongly recommends that best control measures need to be taken for soil PTEs with the intent to alleviate any continuing potential threat to the human health, property and environment, which otherwise could enter ecosystem and ultimately the living beings. Further studies are recommended to combat the soil PTEs concentrations and toxicity in the Tribal areas for a best picture of understanding the element effects on human, and environment can be achieved that will lead to a sustainable ecological harmony.

The relationship between historical development and potentially toxic element concentrations in urban soils

Increasing urbanisation has a direct impact on soil quality, resulting in elevated concentrations of potentially toxic elements (PTEs) in soils. This research aims to assess if soil PTE concentrations can be used as an ‘urbanisation tracer’ by investigating geogenic and anthropogenic source contributions and controls, and considering PTE enrichment across historical urban development zones. The UK cities of Belfast and Sheffield are chosen as study areas, where available shallow and deep concentrations of PTEs in soil are compared to identify geogenic and anthropogenic contributions to PTEs. Cluster analysis and principal component analysis are used to elucidate the main controls over PTE concentrations. Pollution indices indicate that different periods of historical development are linked to enrichment of different PTEs. Urban subdomains are identified and background values calculated using various methodologies and compared to generic site assessment criteria. Exceedances for a number of the PTEs considered suggest a potential human health risk could be posed across subdomains of both Belfast and Sheffield. This research suggests that airborne diffuse contamination from often historical sources such as traffic, domestic combustion and industrial processes contribute greatly to soil contamination within urban environments. The relationship between historical development and differing PTEs is a novel finding, suggesting that PTEs have the potential for use as ‘urbanisation tracers’. The investigative methodology employed has potential applications for decision makers, urban planners, regulators and developers of urban areas.

Occurrence and distribution of selected potentially toxic elements in soils of playing sites: a case study from Bratislava, the capital of Slovakia

This study investigates the occurrence and distribution of potentially toxic elements (PTEs) (As, Cd, Cu, Hg, Pb and Zn) in soils collected at playing sites in kindergartens and urban parks in Bratislava city. It was found that the history of urban development was an important factor influencing the occurrence of PTEs in soils. The mean concentrations of PTEs were two times higher (mean of 215 mg/kg for the sum of PTEs) in the oldest urban parts than in urban parts of the city with younger history (mean of 110 mg/kg). Significant positive correlations between the concentrations of Cu, Hg, Pb, Zn and total organic carbon content (Spearman r = 0.23–0.49; α < 0.05–0.001), as well as between the As, Cu, Pb, Zn concentrations and the total Fe content (Spearman r = 0.27–0.55; α < 0.05–0.001) indicated that soil characteristics had also influenced the distributions of PTEs in soils. The values of enrichment factor (EF) and contamination factor (CF) were higher than 1.5 and 1.0, respectively, confirming an anthropogenic contribution to the total concentrations of PTEs in soils. It is expected that there is no non-carcinogenic health risk to children due to exposure to PTEs in soils as the calculated values of hazard quotient (HQ) and hazard index (HI) did not exceed the threshold of 1.0.