Geochemical modelling and ecological risk of heavy metals in industrial agricultural soils: a Python-driven approach from southwestern Nigeria

The Integrated Spatial Ecological Risk Assessment of Heavy-Metal Contamination in Arid Mining-Influenced Region in Central Asia

The spatial distributions of the potential ecological risk index (RI) and the geoaccumulation index (Igeo) in soils of the Zhetysu region (Kazakhstan) were examined. The enrichment factor ranged from 39.4 for cadmium to 21,481 for nickel. There are few non-ferrous metal enterprises and mineral deposits located in the region. Soil sampling was conducted at 54 locations across the region. The contamination indices were calculated based on the concentrations of four heavy metals in the soil in 2025: copper (Cu), lead (Pb), cadmium (Cd), and nickel (Ni). The RI index varied across the study area within range of 53–353, with an average value of 129. The main points of high environmental risk are the Balkhash Lake’s eastern coast (RI = 318) and industrial city Tekeli (RI = 353). The Igeo values were as follows: Cu −0.61–3.82 (mean: 2.07); Pb −0.58–3.35 (mean: 0.49); Cd −2.91–2.15 (mean: −0.11); and Ni −4.23–4.17 (mean: 0.43). The transport of contaminants occurs under the influence of the wind regime and water erosion processes. Lead, cadmium, and nickel have a variation coefficient greater than 50, indicating metal particle transport from adjacent areas. Wind patterns in certain areas of the region determine the distribution of foci of high heavy-metal concentrations in the soil.

Spatial distribution and ecological risk of heavy metals in agricultural surface soil around brick kilns, Natore, Bangladesh

Ecological Risk Assessment of Heavy Metals in Soils and Surface Waters of Oil-Producing Areas in Akwa Ibom State, Nigeria

Aim: This study assessed the ecological risk posed by six heavy metals [lead (Pb), zinc (Zn), nickel (Ni), copper (Cu), chromium (Cr), and cadmium (Cd)] in soils and surface waters. Study Design: Soil samples were collected at two depths (0–15 and 15–30 cm) from 12 stations across Onna, Mkpat Enin, Eastern Obolo, and Uyo in Akwa Ibom State. Surface-water samples were also collected, and Uyo served as the reference location. Methodology: Composite soil samples were collected using a stainless-steel soil auger. Following acid digestion, metal concentrations were determined by atomic absorption spectrophotometry (AAS). The contamination factor (CF), degree of contamination (C-deg), geoaccumulation index (Igeo), single-metal ecological risk factor, and comprehensive potential ecological risk index (RI) were calculated using average-shale background values and the methods of Müller and Hakanson. Results: Except for nickel at Onna Station 3 (57.5 mg/kg), which exceeded the adopted agricultural and residential soil guideline values, soil-metal concentrations were below the relevant limits. In surface water, lead and nickel exceeded the adopted WHO guideline values at all four locations, whereas chromium and cadmium exceeded the guidelines at two locations. Most CF and Igeo values indicated low contamination, although cadmium showed the greatest relative enrichment at several stations. Conclusion: Although several stations, including the reference location, showed moderate-to-considerable single-metal risk from cadmium, RI remained below 150 at all soil stations, indicating low overall potential ecological risk. The results provide baseline information for environmental monitoring and remediation prioritisation in the studied oil-producing areas.

Assessment of heavy metals and radionuclides pollution in an agro-mining river system: implications for environmental and human health

This study assessed heavy metal (Cu, Ni, Pb, Zn and Cd) and radionuclide (²²⁶Ra, ²³²Th and ⁴⁰K) pollution and associated risks in the Likuyu River system, Tanzania. Surface water and sediments were collected from five sites along a 22.7 km river stretch, while soils and leafy vegetables were sampled from adjacent farms. Heavy metals were analysed by atomic absorption spectrometry and radionuclides by high-purity germanium gamma spectrometry. Risk assessment used contamination factor (CF), geoaccumulation index (Igeo), pollution load index (PLI), bioaccumulation factor (BAF), non-carcinogenic risk, carcinogenic risk (CR), annual effective dose (AED), radium equivalent activity (Raeq), annual ingestion dose (Ding) and excess lifetime cancer risk (ELCR). Heavy metals in river water were below detection limits and complied with WHO drinking-water limits: The Zn, 3–5 mg L⁻¹; Cd, 0.003 mg L⁻¹; Ni, 0.07 mg L⁻¹; Cu, 2.0 mg L⁻¹; and Pb, 0.0135 mg L⁻¹. The Ni in sediments at Sites A and E reached 32.1 ± 26.90 and 35.97 ± 6.51 mg kg⁻¹, respectively, exceeding the threshold effect concentration of 22.7 mg kg⁻¹ but remaining below the probable effect concentration of 48.6 mg kg⁻¹. Pollution indices indicated generally low sediment contamination, with CF values mostly below 1, Igeo values from −5.49 to −0.40, and PLI values from 0.077 to 0.251, although slight Zn enrichment occurred at Site A (CF = 1.14). Soils were weakly polluted, with PLI values of 0.078–0.105; however, Site SOD showed localized Ni enrichment, with CF = 1.577 and Igeo = +0.07, reaching 107.2 ± 1.40 mg kg⁻¹, exceeding the TBS limit of 50 mg kg⁻¹. Bioaccumulation results showed strong Zn uptake in napa cabbage (BAF >12), cowpea (BAF ~8) and okra (BAF ~6), and Pb accumulation in okra (BAF ~6) and cowpea (BAF ~5), whereas Ni and Cd had BAF

Source–Sink Relationships and Environmental Risks of Surface Soil Heavy Metals and Metalloids: Multi-Media Monitoring in a Southwest China County

The pollution of soil by potentially toxic elements in industrial–agricultural transition zones threatens global food security and public health owing to their persistence and bioaccumulation. This study focused on Miyi County, Sichuan (China), a typical region with intensive vanadium–titanium magnetite mining and modern agriculture, and systematically analyzed eight heavy metals and metalloids (Cd, Hg, As, Pb, Cr, Cu, Zn, and Ni) across the categories of atmospheric deposition, irrigation water, agricultural inputs, and soil–crop systems. A rigorous four-stage full-chain diagnosis (concentration–load–ecology–health) was executed to evaluate pollution levels and pathways. The single-factor pollution index identified cadmium (Cd) as the primary pollutant, exhibiting a maximum index of 32.63. The Håkanson potential ecological risk index (RI) demonstrated that Cd was the absolute dominant contributor, reaching a catastrophic single-element risk factor (Ei) of 2191.8 and contributing over 70% to the comprehensive ecological risk. Spatially, soils displayed a distinct point-source cluster diffusion pattern: the northern metallurgical zone was dominated by a Cr-Zn-Cu-Ni industrial assemblage, while the southern zone was enriched in Cd, Pb, As, and Hg. Positive matrix factorization (PMF) source apportionment quantitatively demonstrated that industrial emissions via atmospheric deposition were the primary driver, contributing 55–75% of the total soil exogenous inputs, while agricultural sources (livestock manure and legacy arsenic pesticides) exacerbated localized accumulation. While overlying irrigation water remained safe, channel sediments acted as historical pollution sinks. The human health risk model revealed that children in industrial core areas faced unacceptable carcinogenic hazards, with a lifetime carcinogenic risk (LCR) reaching 5.6 × 10−4. These highly specific multi-media findings support a macro spatial risk zoning and source interception strategy to decouple economic growth from regional food safety degradation in global transition economies.

Environmental monitoring of soil and vegetation in uranium mining areas

Abstract Uranium mining activities in southern Kazakhstan pose ecological risks due to the accumulation of radionuclides and heavy metals in soil and vegetation. This study aimed to assess the radiological and chemical status of ecosystems near uranium mining sites using radiometric analysis, X-ray spectrometry, and bioindication methods. A total of 78 soil and 37 plant samples were collected in 2021–2023 from sites near settlements labeled N, B, and S. Results showed that seven soil samples exceeded the maximum permissible concentration (MPC) for background radiation, with values reaching up to 1.25× MPC. 40K was the most prominent radionuclide in vegetation, averaging 680 Bq/kg, while U-238 was not detected in plant tissues. Heavy metals such as Pb exceeded safety thresholds in plants, with an average of 19.6 mg/kg (3.9× MPC). Zn and P showed variable uptake depending on species and location. Floristic analysis revealed 32 species in experimental sites, including endemic taxa. However, no significant structural anomalies were observed in plant tissues. The study concludes that while large-scale contamination is absent, localized zones of elevated radioactivity and heavy metal accumulation warrant continuous environmental monitoring.