Jul 2026· Asian Journal of Physical and Chemical Sciences· 0 citations
Abstract
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.
Heavy metal pollution in wetland ecosystems poses serious threats to aquatic biodiversity and human health, particularly in agricultural regions with limited environmental monitoring. This study assesses the distribution, sources, and health risks of eight trace metals: lead (Pb), cadmium (Cd), chromium (Cr), manganese (Mn), nickel (Ni), mercury (Hg), copper (Cu), and zinc (Zn) in the Khaliajury haor, a critical wetland in Netrokona, Bangladesh. From June to December 2024, samples of surface water, sediment, and ten commonly consumed fish species were collected across five sampling stations following standard QA/QC procedures. Metal concentrations were compared with national and international guidelines, and source identification was performed along with pollution indices (Igeo, PLI, PER) and health risks (THQ, HI, CR). In surface water, Mn and Cu exceeded permissible limits at all stations. Cr and Hg in sediment surpassed the toxicity reference value (TRV) at every site, while Cd, Ni, and Cu were elevated at multiple locations. However, negative Igeo values and PLI scores below 1 indicated uncontaminated sediment status with low potential ecological risk (PER). In fish tissues, Mn exceeded maximum allowable concentrations (MAC) in seven of ten species, followed by Pb in five species, and Cr and Cd each in two species. Although THQ and HI values remained below 1, suggesting negligible non-carcinogenic risk, cancer risk (CR) values for Pb, Cd, Cr, and Ni exceeded the USEPA upper acceptable threshold of 10⁻4 across all species, implying potential lifetime carcinogenic risk to consumers. Multivariate analysis (correlation matrix and PCA) displayed that bioaccumulation of heavy metals sourced from agricultural runoffs, anthropogenic activities, wastewaters and environmental processes, that travel through different trophic levels in the wetland system. These findings underscore the need for systematic biomonitoring, source identification, and risk communication for communities dependent on haor fisheries.
Dulon Roy, Smita Sarker, Wasim Khan et al.· Journal of Food Protection· 0 citations
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
Uncontrolled disposal of municipal solid waste is a growing environmental concern in developing countries, contributing to heavy metal accumulation in surrounding soils and water. This study assessed the concentrations, spatial distribution, and ecological risks of heavy metals around the Mzedi municipal dumpsite in Blantyre, Malawi. Composite soil samples were collected at 0 m, 50 m, 250 m, 400 m, and 650 m from the dumpsite, while surface water samples were taken from a nearby stream receiving runoff. Samples were analyzed for cadmium (Cd), zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), lead (Pb), and cobalt (Co) using atomic absorption spectrophotometry. Contamination and risk levels were evaluated using the Contamination Factor (CF), Geo-accumulation Index (Igeo), Enrichment Factor (EF), and Potential Ecological Risk Index (PERI). Soil metal concentrations decreased with distance from the dumpsite in the order Fe > Mn > Zn > Cu > Pb > Cd > Co. Cadmium exhibited the highest contamination levels, with CF (70.00), Igeo (5.54), and EF (19.17) at 0 m indicating extremely polluted conditions and severe anthropogenic enrichment. PERI values ranged from 2,181 at 0 m to 117 at 650 m, shifting from very high to low ecological risk. Cadmium contributed > 96% of the total ecological risk, confirming it the dominant contributor to ecological risk. In surface water, Cd (0.006–0.008 mg/L) and Pb (0.025–0.030 mg/L) exceeded WHO drinking water guidelines, confirming leachate-driven contamination of the adjacent stream. While crop metal concentrations were not directly measured, the elevated soil cadmium levels indicate potential for plant uptake and possible human exposure. However, without direct crop analysis, we cannot confirm the extent of food chain transfer, quantify dietary exposure, or assess compliance with food safety standards. This highlights the critical need for targeted crop monitoring studies to validate the inferred human health risks. This study provides the first comprehensive quantitative assessment of ecological risk at the Mzedi dumpsite using multiple contamination indices and robust statistical analysis. The findings support precautionary management measures, including restrictions on farming directly on the dumpsite, upgrading of waste disposal infrastructure, and community awareness programs.
Vincent Gwengwe, E. Vunain· Resources Environment and In...· 0 citations
This study investigated the accumulation and ecological risk of heavy metals in soils surrounding a major open dumpsite adjacent to the New Abattoir in Akerebiata Harmony Estate, Ilorin, Southwestern Nigeria. Ten representative soil samples were collected at 9 m by 45 m intervals and analyzed using Atomic Absorption Spectroscopy (AAS) to determine concentrations of Copper (Cu), Zinc (Zn), Chromium (Cr), Iron (Fe), Cadmium (Cd), Cobalt (Co), Arsenic (As), Lead (Pb), Silver (Ag), and Mercury (Hg). Environmental impact was evaluated through the calculation of the Geo-accumulation Index (Igeo), Contamination Factor (CF), Pollution Index (PI), Enrichment Factor (EF), Hazard Quotient (HQ), Hazard Index (HI), and Cancer Risk (CR). Results indicated that while absolute concentrations remained below current regulatory limits, the site is moderately to strongly polluted (PI = 3.37) due to significant anthropogenic inputs. Igeo values showed that the area is uncontaminated regarding Cr, Hg, and Cd, but moderately contaminated with Co and As. The HQ and HI values for all metals were below 1.0 for both children (HI = 0.0016) and adults (HI = 0.0002), indicating no immediate non-carcinogenic risk via soil ingestion. Total cancer risk (CR = 2.08 × 10⁻8 for children) fell within the acceptable range (< 10⁻⁶). However, trends in As, Co, and Hg contamination factors warrant precautionary monitoring. Principal Component Analysis (PCA) attributed PC1 (34.73% variance) primarily to geogenic Fe–Cr inputs and PC2 (24.52%) to anthropogenic Cu-As loading. These findings suggest that the current open dumping system poses a growing risk to the local ecosystem and public health. The study recommends the implementation of engineered sanitary landfills, regular environmental monitoring, and remediation strategies to mitigate future heavy metal accumulation.
Durga Ruth Panchalingam, M. Adisa· Discover Environment· 0 citations
Petroleum exploration and production can introduce potentially toxic metals into the soils and water bodies of host communities, with consequences for both ecosystem integrity and human exposure. This study assessed the concentrations and distribution of ten heavy metals: Ni, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn in soil and water from two oil-field communities, Apkai (Ndokwa East Local Government Area) and Umusedege (Ndokwa West Local Government Area), Delta State, Nigeria. A total of 63 soil samples and 11 water samples were collected across the two communities and a nearby control site (Obetim). Soil metals were determined by atomic absorption spectrophotometry (AAS) and, for Zn, Fe and Cu, cross-checked by X-ray fluorescence (XRF); water metals were determined by AAS alone. Overall mean soil concentrations were 148.58, 254.41, 53.15, 0.16, 229.98, 21.85, 2905.61, 1228.55, 0.58 and 175.87 mg kg⁻¹ for Ni, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn, respectively, with Fe as the dominant element throughout. Relative to the control, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn were all elevated in soil, while Ni was slightly lower; the largest soil enrichment ratios were recorded for Mn (2.10×), As (1.81×) and Cr (1.76×). In water, mean concentrations were 0.14, 0.04, 0.13, 0.35, 0.03, 6.91, 1.25 and 0.30 mg L⁻¹ for Ni, Cr, Cu, Pb, Cd, Fe, Mn and Zn, respectively (Co and As were not detected), with Pb (10.77×) and Zn (10.17×) showing by far the largest enrichment relative to the control. The AAS–XRF comparison showed statistically significant differences for Zn, Fe and Cu (p < 0.05 in all cases); XRF consistently returned higher values than AAS. Measured against the soil guideline values reproduced in the underlying study, Ni, Cr, Cu, Pb, Cd, Fe and Mn all exceeded their respective thresholds, most markedly Mn, Fe, Cd, Cr and Pb; in water, Fe, Pb, Cd, Ni and Mn were flagged as being of particular concern against U.S. EPA, WHO and SON reference values. Taken together, the results indicate substantial, spatially uneven alteration of soil and water metal concentrations in this oil-field environment relative to the surrounding background, consistent with a combination of lithogenic and anthropogenic contributions, and establish a concentration baseline for the pollution-index, fractionation and health-risk assessments that build on this dataset.
Sanda Yusuf Sadau, Ishaya Iliyasu, M. Alpha et al.· Physical Science Internation...· 0 citations
Heavy metal contamination in tidal river systems is an increasing environmental concern in rapidly urbanizing regions of South Asia. This study presents an integrated assessment of heavy metal pollution and ecological risk in the Bhairab–Rupsha River basin, Bangladesh. Concentrations of six priority metals—chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb)—were determined in water and surface sediments collected during the pre‐ and post‐monsoon seasons using inductively coupled plasma–mass spectrometry (ICP–MS). Data quality was ensured through strict QA/QC procedures. Pollution and ecological risks were evaluated using the heavy metal pollution index (HPI), heavy metal evaluation index (HEI), water–sediment concentration factor (
K
d
), contamination factor (
C
f
), degree of contamination (
C
d
), pollution load index (PLI), geo‐accumulation index (
I
geo
), ecological risk factor (
E
r
), potential ecological risk index (PER), spatial mapping, and principal component analysis (PCA). Water samples showed the concentration order as follows: Cu > Cr > Ni > Pb > Zn > Cd, with Cr, Cd, and Pb exceeding the Bangladesh Environmental Conservation Rules and the relevant United States Environmental Protection Agency (USEPA) and CCME aquatic life guidelines. HPI values exceeded the critical limit (>100) at all stations, indicating severe water quality deterioration, particularly downstream. In contrast, sediment metal concentrations remained below guideline thresholds, with
C
f
< 1,
C
d
< 8, PLI < 1,
I
geo
< 0, and PER indicating low ecological risk. Spatial analysis revealed increasing downstream enrichment associated with industrial discharges, municipal wastewater, and port activities. PCA explained 98.8% of the total variance, suggesting a dominant anthropogenic source of contamination.
Tamzid Ahmed, Q. H. Bari, Md. Mahamudur Rahman et al.· CLEAN - Soil, Air, Water· 0 citations
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