Environmental and health impact of potentially harmful elements distribution in the Panyam (Sura) volcanic province, Jos Plateau, Central Nigeria

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The Panyam volcanic province is a plateau covering a superficial area of about 1200 km2, dotted by a number of dormant volcanoes forming prominent landmarks above the host continental gneiss–migmatite–granite rocks and stretching for about 12 km. The volcanism is basaltic, characterized by alkaline–calc–alkaline compositions. Large population of pe ople live and depend on the volcanic environment for potable water and agriculture, most of whom display various forms of health problems ranging from dental caries, goitre, podoconiosis, etc. This study therefore seeks to evaluate the concentration levels of potentially harmful elements (PHEs) in the various components of the volcanic environment and their relationship with the inherent human health problems in the area. Volcanic soils and underground waters (springs/boreholes waters) were collected from within the volcanic province for the analysis of major cations and anions. Samples of the volcanic soils were analyzed for the following heavy elements; Be, Co, Cr, Cu, As, Cd, Pb, Sb, Se, V, and Zn. Water samples were analyzed for the major cations (Mg2+, Ca2+, Na+ and K+) and major anions (\({\text{NO}}_{3}^{2 - }\), \({\text{SO}}_{4}^{2 - }\), Cl−, \({\text{HCO}}_{3}^{ - }\) and F−) to determine their hydrogeochemical characteristics so as to identify the major sources of the cations and anions and factors controlling their distribution. The volcanic soils display mean values in Be, Co, Cr, Ni, Pb, Sb and Se above the baseline regional values with enrichment factors (EF) (2 ≤ EF ≤ 5) indicating moderate to strong enrichment in the volcanic soils. Contrarily, there is clear impoverishment of As, Cd, Cu, V and Zn in the volcanic soils relative to the baseline values (0 ≤ EF ≤ 2). Except for Ni and Se which seem to have contaminated the volcanic soils [pollution load index (PLI) > 1], these other elements As, Be, Cd, Cr, Cu, Pb, Sb, V and Zn with PLI < 1 did not, possibly suggesting little or no anthropogenic input. The rare earth elements (REEs) are equally enriched in the volcanic soils and like most of the other PHEs, they must have been scavenged and co-precipitated with Fe during the weathering of the parent basaltic rock. The significantly lower La/Ce ratios (0.30–0.57) in the volcanic soils attest to the moderate to slightly severe intensity of weathering the parent basaltic rock was subjected to. The waters are predominantly (80 %) of Ca–Mg–HCO3 type with the remaining 20 % of Na–K–HCO3 type suggesting a control by water–rock alteration process from the host granitic basement and the overlying basaltic rocks. The fluoride content in all the water sources is positively correlated with the contents of Mg2+, Na+, and K+ suggesting a similar source and geochemical process. Tooth decay, a common tooth disease conditions in the volcanic province, could be linked to the low F content in the waters.