Regional geochemical baseline concentration of potentially toxic trace metals in the mineralized Lom Basin, East Cameroon: a tool for contamination assessment

Evaluation of surface water contamination and its impacts on health in the mining districts of Kambélé and Bétaré-Oya (Eastern-Cameroon)

This study aimed to assess water contamination and associated health risks for populations residing in the mining areas of Kambélé and Bétaré-Oya. Key parameters, including pH, EC, TDS, TSS, and concentrations of metallic elements (Cd, Cr, Fe, Pb and Mn), were measured using established water analysis techniques. The analysis included multivariate statistical assessments, calculation of metal pollution and water quality indices, and health risk determinations, including daily intake (DI) and hazard quotient (HQ). Findings indicate a diverse pH range (5.26 < pH < 8.72), low mineralization (33.22 < EC (μS/cm) < 179.64), and elevated TSS content (22.53 < TSS (in mg/l) < 271.51). Metallic elements were observed in the descending order of Fe > Mn > Pb > Cr > Cd. Water quality assessments using the Water Quality Index (WQI) categorized sites as displaying doubtful to very poor quality, notably Woupy (WQI = 719.14) in Kambélé and Mali (WQI = 794.24) in Bétaré-Oya, with Heavy metal Pollution Index (HPI) values exceeding 100. These outcomes highlight consistent chemical degradation of surface water, posing potential risks to local populations' health and well-being. The study emphasizes the critical need for proactive environmental protection measures in mining areas, recommending the adoption of healthy mining practices and effective site reclamation strategies. Furthermore, future studies should consider exposure duration's potential impact on residents' health problems in these areas. Overall, this study contributes significantly to understanding and addressing the intricate interplay between mining activities, water quality, and public health in the Cameroon countryside.

Environmental Impacts of Coal Nanoparticles from Rehabilitated Mine Areas in Colombia

With the possible increase in mining activities and recently projected population growth in Colombia, large quantities of nanoparticles (NPs) and potentially hazardous elements (PHEs) will be of major concern to mine workers, indigenous residents, and surrounding communities. This study highlights the need to regulate the pollution from Colombian mining activities that comply with regional regulations and global strategies. Colombian coal rejects (CRs) from the Cesar Basin, Colombia, were studied primarily by advanced electron microscopic and analytical procedures. Therefore, the goal of this research is to evaluate the role of NPs in the alteration of CRs’ structure in a renewed zone at Cerrejón coal area (La Guajira, Colombia) through advanced electron microscopic (AEMs) methods. The objective of the analysis is to evaluate the incidence mode of nanoparticles, which contain potentially hazardous elements. The bulk crystallography (X-ray diffraction), chemical structure, and morphologies of NPs were studied by high-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), micro-beam diffraction (MBD), selected area electron diffraction (SAED), and energy-dispersive X-ray spectroscopy (EDX) procedures. The AEMs provided comprehensive insights into the geochemical evolution of CRs. Consequently, the AEMs can be used as essential tools for CR management in coal mining areas. The regular dimension of detected NPs was found to be above 2 nm. Ultrafine particles of quartz were identified by the advanced electron microscopy. Furthermore, the findings also revealed aluminium, calcium, potassium, titanium, iron oxides, and PHEs in the CRs. The extensive water practice in the coal extraction process combined with atmospheric oxygen supports oxidations of iron sulphide, thus releasing PHEs to the surrounding environment. Dehydration of sulphate salts fluctuate at consistent humidity in the coal mine environments. The study demonstrates the great influence of coal mining activities on the environment and human health.

Heavy Metals in Sapropel of Lakes in Suburban Territories of Vilnius (Lithuania): Reflections of Paleoenvironmental Conditions and Anthropogenic Influence

Geochemical and lithological parameters of sapropel in lakes, combined with pollen data and radiocarbon 14C dating, contain a wide spectrum of environmental information. This includes records of fluctuations of water level and changes of conditions of sedimentation, accumulation of organic matter and chemical elements due to climate change, human impacts and other environmental changes. Rising concentrations of hazardous substances in the natural sediments are likely to be a high risk to the natural environment. At the same time, they can greatly reduce opportunities for environmental engineering of lakes. Four lakes with different trophic states and anthropogenic pressures were chosen for this study in Lithuania. Higher concentrations of elements like Cr, Cu and Zn were not only detected in the top most layers of sapropel but also in deeper layers and are attributed to lithogenic association of trace elements in such deep layers. Concentrations of Pb were detected only in upper layers of sapropel which indicates the impact of anthropogenic activity. The main source of heavy metals was multidimensional anthropogenic pollution leading to a biogenic–anthropogenic association of elements. Sapropel with low concentrations of heavy metals exhibits a different inter-association matrix because most of the elements tend to form lithogenic–clastogenic associations.

Source and background threshold values of potentially toxic elements in soils by multivariate statistics and GIS-based mapping: a high density sampling survey in the Parauapebas basin, Brazilian Amazon

A high-density regional-scale soil geochemical survey comprising 727 samples (one sample per each 5 × 5 km grid) was carried out in the Parauapebas sub-basin of the Brazilian Amazonia, under the Itacaiúnas Basin Geochemical Mapping and Background Project. Samples were taken from two depths at each site: surface soil, 0-20 cm and deep soil, 30-50 cm. The ground and sieved (< 75 µm) fraction was digested using aqua regia and analyzed for 51 elements by inductively coupled plasma mass spectrometry (ICPMS). All data were used here, but the principal focus was on the potential toxic elements (PTEs) and Fe and Mn to evaluate the spatial distribution patterns and to establish their geochemical background concentrations in soils. Geochemical maps as well as principal component analysis (PCA) show that the distribution patterns of the elements are very similar between surface and deep soils. The PCA, applied on clr-transformed data, identified four major associations: Fe-Ti-V-Sc-Cu-Cr-Ni (Gp-1); Zr-Hf-U-Nb-Th-Al-P-Mo-Ga (Gp-2); K-Na-Ca-Mg-Ba-Rb-Sr (Gp-3); and La-Ce-Co-Mn-Y-Zn-Cd (Gp-4). Moreover, the distribution patterns of elements varied significantly among the three major geological domains. The whole data indicate a strong imprint of local geological setting in the geochemical associations and point to a dominant geogenic origin for the analyzed elements. Copper and Fe in Gp-1 were enriched in the Carajás basin and are associated with metavolcanic rocks and banded-iron formations, respectively. However, the spatial distribution of Cu is also highly influenced by two hydrothermal mineralized copper belts. Ni-Cr in Gp-1 are highly correlated and spatially associated with mafic and ultramafic units. The Gp-2 is partially composed of high field strength elements (Zr, Hf, Nb, U, Th) that could be linked to occurrences of A-type Neoarchean granites. The Gp-3 elements are mobile elements which are commonly found in feldspars and other rock-forming minerals being liberated by chemical weathering. The background threshold values (BTV) were estimated separately for surface and deep soils using different methods. The '75th percentile', which commonly used for the estimation of the quality reference values (QRVs) following the Brazilian regulation, gave more restrictive or conservative (low) BTVs, while the 'M_MAD' was more realistic to define high BTVs that can better represent the so-called mineralized/normal background. Compared with CONAMA Resolution (No. 420/2009), the conservative BTVs of most of the toxic elements were below the prevention limits (PV), except Cu, but when the high BTVs are considered, Cu, Co, Cr and Ni exceeded the PV limits. The degree of contamination (C_deg), based on the conservative BTVs, indicates low contamination, except in the Carajás basin, which shows many anomalies and had high contamination mainly from Cu, Cr and Ni, but this is similar between surface and deep soils indicating that the observed high anomalies are strictly related to geogenic control. This is supported when the C_deg is calculated using the high BTVs, which indicates low contamination. This suggests that the use of only conservative BTVs for the entire region might overestimate the significance of anthropogenic contamination; thus, we suggest the use of high BTVs for effective assessment of soil contamination in this region. The methodology and results of this study may help developing strategies for geochemical mapping in other Carajás soils or in other Amazonian soils with similar characteristics.

Contamination and risk assessment of heavy metals, and uranium of sediments in two watersheds in Abiete-Toko gold district, Southern Cameroon

In this investigation, the level of toxic metals (Cd, Pb, Hg, Cu, Ni, Al, Zn and U) was determined in sediment samples from two watersheds (Kienké and Tchangué) in the Abiete-Toko gold district, southern Cameroon. The potential contamination and toxicity of studied metals was determined by evaluating enrichment factor (EF), geo-accumulation index (Igeo) and ecological risk assessment (ERA). Considering the spatial distribution patterns, metal concentrations were lower than the average shale values, except for Cu and Ni of site 4 in the Kienké watershed and only Ni in the Tchangué watershed. In this study, the EF and Igeo values revealed that sediments were moderately polluted by Ni and Cu and unpolluted by other metals. The evaluation of the ERA based on ecological risk index (RI), ecological risk factor (Er), contamination factor (CF) and pollution load index (PLI) revealed that the sediments from the Abiete-Toko watersheds have significant to very high ecological risk assessment and are generally unpolluted by trace metals and U, except for Ni and Cu. Little quantities of heavy metals with low U levels and distribution were found at the sites close to the vicinity of artisanal mining and peri-urban areas. This proximity reveals that artisanal gold mining activities, agricultural runoff, and other anthropogenic inputs in the study area are probable sources of slight metal contamination. However, the non-use of toxic effluents for gold mining and pesticides for agriculture can be an advantage of the unpolluted status of the watersheds. The physical degradation of the ecosystem through excavations, wells and other stream diversion methods is expanding in the zone. Appropriate measures should be taken by artisans to rehabilitate the gold mining sites, to ensure appropriate treatment of wastewater and non-use of toxic effluents into nearby tributaries.

Occurrence and levels of potentially harmful elements (PHEs) in natural waters of the gold mining areas of the Kette-Batouri region of Eastern Cameroon

This study was designed to determine the extent to which alluvial and bedrock gold mining activities in the Kette-Batouri region of Eastern Cameroon are responsible for the discharge of potentially harmful elements (PHEs) into natural water bodies. This is considered to be of great public concern, since elevated levels of PHEs in these water bodies, which are widely used for domestic purposes, could have adverse health and environmental effects on the population and nearby ecosystems. The investigation into the levels of PHEs in natural water bodies of this area was conducted to ascertain the toxicity posed by mine waste stockpiles as data from the literature on this subject are scarce. Forty-two water samples from the region were analysed for some 60 PHEs by ICP-OES, of which 22 that were not below the detection limit were considered for further data analysis. Maximum total concentrations in water of As, Cr, Pb, and V and Zn are above the World Health Organization (WHO) maximum allowable concentration (MAC) levels and are as follows (μg l^-1): As (21.90-50.9); Cr (1.80-57.30); Pb (0.50-34.70); V (24.70-77.20) and Zn (3.10-481.70). This information is consistent with that of our recent research efforts which have indicated moderate pollution by heavy metals in the soils with a slight deterioration of site quality in this region. The data generated from this investigation is important in the formulation of water management strategies and recommendations for remediation of water bodies at abandoned mine sites for meeting water quality standards.