Comparative Physicochemical and Heavy Metal Assessment of Water Sources in Bularafa, Gulani LGA, Yobe State, Nigeria

Abstract

This study evaluated the physicochemical properties and heavy metal concentrations of the major drinking water sources in Bularafa, Gulani Local Government Area, Yobe State, Nigeria, to determine their suitability for domestic consumption. Nine water samples, including tap, well, and borehole water, were collected from Tsangayan Gabas, Unguwar Sarki, and Unguwar Yamma. Standard APHA analytical methods were used for physicochemical analysis, while heavy metals were determined using Atomic Absorption Spectrophotometry (AAS). The physicochemical analysis revealed substantial deviations from World Health Organization (WHO) drinking water standards. Turbidity values ranged from 45.6–51.9 NTU, exceeding the WHO permissible limit of 5.0 NTU by approximately 9–10 fold. Electrical conductivity ranged from 600 to 710 µS/cm, with most samples exceeding the WHO-recommended range of 50–500 µS/cm. Total dissolved solids (TDS) ranged from 610–680 mg/L, indicating elevated dissolved mineral content above the acceptable limit of 600 mg/L in several samples. Total hardness ranged from 15–110 mg/L, with sample B2 exceeding the WHO limit of 100 mg/L. The pH values ranged from 7.4 to 9.3, with sample C3 exceeding the recommended upper limit of 8.5, indicating strong alkalinity. Heavy metal analysis demonstrated alarming contamination levels in several water sources. Lead (Pb) concentrations ranged from 0.3 to 0.8 mg/L, with 55.6% of the samples exceeding the WHO limit of 0.5 mg/L. Cadmium (Cd) concentrations ranged from 0.004 to 0.042 mg/L, with 88.9% of samples exceeding the WHO guideline value of 0.003 mg/L by up to 14-fold. Chromium (Cr) concentrations ranged from 0.1–0.7 mg/L, exceeding the WHO permissible limit of 0.05 mg/L in all samples, with maximum values approximately 14 times higher than the recommended standard. Iron (Fe) and copper (Cu) concentrations remained within WHO permissible limits, ranging from 0.045–0.111 mg/L and 0.18–0.78 mg/L, respectively. The elevated concentrations of Pb, Cd, and Cr may be associated with artisanal mining activities, agricultural runoff, and poor waste disposal practices within the study area. These contaminants pose significant health risks, including kidney damage, neurological disorders, anemia, and carcinogenic effects. The study concludes that most of the analyzed water sources are unsuitable for direct consumption without proper treatment and recommends urgent water-quality monitoring, environmental controls, and public health interventions.