Levels And Forms of Potentially Harmful Elements in Mine Pond Waters of the Jos, Bukuru and Barkin Ladi Area, Northcentral Nigeria

Abstract

Legacy tin mining across the Jos Plateau has resulted in numerous abandoned mine ponds 
that are widely utilized for domestic and agricultural purposes, raising concerns 
regarding contamination by potentially harmful elements (PHEs). This study evaluated 
the concentrations, spatial distribution, and aqueous speciation of selected trace metals 
in 37 mine pond waters from Jos North, Jos South, and Barkin Ladi, north-central 
Nigeria. Field physicochemical parameters indicate predominantly fresh, weakly 
mineralized waters, with pH ranging from 6.51 to 8.27 (mean = 7.49), total dissolved 
solids (TDS) between 4.00 and 100.00 mg/L (mean = 32.76 mg/L), electrical conductivity 
(EC) from 11 to 253 µS/cm (mean = 67.46 µS/cm), and dissolved oxygen (DO) between 
3.99 and 8.36 mg/L (mean = 5.99 mg/L), reflecting generally oxic to mildly reducing 
conditions. Trace element concentrations exhibit pronounced spatial heterogeneity. Zinc 
(Zn) shows extreme enrichment, reaching 10,000.7 ppb (WRID7), with additional 
elevated values at WRID10 (3,836.8 ppb) and WRID34 (3,009.7 ppb). Manganese (Mn) 
peaks at 681.95 ppb (WRID28) and 517.38 ppb (WRID36), while barium (Ba) and 
strontium (Sr) attain maximum concentrations of 180.77 ppb and 152.82 ppb, 
respectively. Lead (Pb) reaches 11.2 ppb, whereas cadmium (Cd) remains largely below 
detection limits. Multivariate statistical analysis indicates that Zn constitutes the 
principal contamination signature, forming a distinct cluster, while Ba and Sr reflect 
lithogenic contributions from Younger Granite host rocks. Principal Component Analysis 
identifies a dominant pollution gradient separating contaminated ponds from background 
waters. Geochemical speciation modeling (WateQ4F) demonstrates the predominance of 
bioavailable divalent species, including Zn²⁺, Mn²⁺, Ba²⁺, Cd²⁺, and Pb²⁺, indicating high 
mobility and ecological risk, whereas chromium occurs mainly as Cr³⁺, reflecting lower 
immediate toxicity. These findings confirm spatially structured, mining-derived metal 
enrichment, controlled by lithology and redox conditions, with significant implications 
for environmental and public health where mine pond waters are actively utilized.