Heavy metals

Heavy metals are naturally occurring metallic elements with high atomic weights and densities at least five times greater than water which due to their persistence, toxicity, and bio-accumulative nature, they pose significant environmental and health risks (Ali et al., 2020). Lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As) are toxic even at low concentrations (Tchounwou
et al., 2020). Heavy metal bioaccumulation refers to the progressive increase in concentration of toxic metals (e.g., Pb, Cd, Hg, As) in living organisms over time, primarily through uptake from contaminated water, soil, or food, exceeding environmental levels due to slow excretion rates (Ali et al., 2023). This process involves the absorption and retention of heavy metals in tissues of organisms, leading to higher internal concentrations than their surroundings, with potential transfer across food chains (biomagnification) (Javed et al., 2022).

A groundwater quality assessment was conducted in Ikpoba Okha Local Government Area, Edo State, to evaluate the levels of physicochemical parameters within the region. Fifteen (15) borehole water samples were randomly collected and analyzed to determine their physicochemical characteristics. Both statistical and cluster analyses were applied to interpret the data. The dendrogram, a key output of the cluster analysis, illustrated the Euclidean distance at which different elements and clusters merged. Four distinct clusters were identified, with Cluster 1comprising mainly heavy metalsshowing strong correlations and similarities among related parameters. The study examined parameters such as pH, turbidity, total dissolved solids (TDS), electrical conductivity, salinity, and total suspended solids (TSS). Anions including sulfate, phosphate, nitrate, and carbonate were also analyzed, while heavy metals and cations such as sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) were determined using a flame atomic absorption spectrometer. Results indicated that the pH of the groundwater samples ranged between 5.28 and 5.98, suggesting slight acidity. TDS values varied from 5.34 to 6.22 mg/L, while nitrate concentrations ranged from 1.54 to 2.12 mg/Lall within the World Health Organization (WHO) permissible limit of 10 mg/L. Copper concentrations were found between 0.039 mg/L and 0.086 mg/L, with borehole BH9 recording the highest value and BH15 the lowest. Manganese levels ranged from 0.05 mg/L to 0.35 mg/L, exceeding the WHO guideline of 0.1 mg/L in only one sample (BH8). Overall, the findings suggest that while some boreholes meet WHO standards, othersespecially wellsexceed acceptable limits for certain parameters, rendering them unsuitable for human consumption. The deterioration of groundwater quality in the area is likely attributed to
anthropogenic activities such as improper waste disposal and sewage discharge.