Assessment of heavy metals, pollution indices, and physicochemical characteristics of borehole water from abattoir sites in Kaduna Metropolis, Kaduna State, Nigeria

Abstract

Borehole water contamination from abattoir operations is an emerging environmental and public health concern in developing urban centers like Kaduna Metropolis. This study evaluated the pollution status of borehole water sources located around abattoirs within Kaduna Metropolis, Nigeria, focusing on heavy metals and physicochemical parameters to assess compliance with international and national water quality standards. Borehole water samples were collected from selected abattoir and control sites. Heavy metal concentrations were determined using Atomic Absorption Spectrophotometry (AAS), while physicochemical parameters were analyzed following APHA Standard Methods (2017). Data were subjected to one-way analysis of variance (ANOVA) to evaluate spatial variation, and pollution indices such as the Contamination Factor (CF) and Pollution Load Index (PLI) were applied to assess the degree of metal contamination. Concentrations of zinc (Zn) and copper (Cu) were within the World Health Organization (WHO, 2017) guideline limits, suggesting no immediate health risk. In contrast, cadmium (Cd) and lead (Pb) exceeded permissible limits at both abattoir and control locations, whereas nickel (Ni) met WHO standards but slightly surpassed the Nigerian Standard for Drinking Water Quality (NSDWQ) threshold. ANOVA results (p > 0.05) indicated no significant variation among sampling sites, suggesting uniform contamination from both abattoir and non-abattoir sources. CF and PLI values identified Tudun Wada abattoir as the most contaminated site, particularly for Cu. Most physicochemical parameters, including pH, potassium, biochemical oxygen demand (BOD), and chemical oxygen demand (COD), were within acceptable limits, though nitrate (72 mg/L) and total dissolved solids (738 mg/L) exceeded WHO standards at Tudun Wada, indicating localized pollution. The study concludes that while groundwater around Kaduna abattoirs generally meets quality standards for most indicators, the elevated levels of Pb and Cd highlight potential public health and ecological risks. Continuous monitoring, improved effluent management, and enforcement of environmental protection regulations are recommended to prevent long-term groundwater contamination.