Geochemical Distribution and Health Risk Assessment of Heavy Metals in Volcanic Soils of Abwor-dyis, Gu Volcanic Line, Jos Plateau, Nigeria.

Abstract

This study investigates the spatial distribution, contamination levels, and potential 
human-health risks associated with heavy metals in volcanic soils of Abwor-Dyis and its 
environs within the Pankshin Sheet 190 (NE), north-central Nigeria. Systematic soil 
sampling was carried out across representative sites, and the collected samples were 
analyzed for selected potentially toxic elements, including copper (Cu), cadmium (Cd), 
arsenic (As), chromium (Cr), nickel (Ni), manganese (Mn), cobalt (Co), and zinc (Zn), using 
standardized analytical procedures with appropriate quality control. Comprehensive 
geochemical characterization was achieved through major and trace element analyses 
integrated with multiple environmental assessment indices. The geo-accumulation index 
(Igeo), enrichment factor (EF), pollution index (PI), and Hakanson’s ecological risk index 
(ERI) were employed to evaluate contamination intensity, toxicity potential, and the 
relative contributions of geogenic versus anthropogenic sources. In addition, the 
pollution load index (PLI) was used to assess the overall degree of soil contamination, 
while the United States Environmental Protection Agency (US EPA) human-health risk 
assessment model was applied to estimate non-carcinogenic and carcinogenic risks 
through relevant exposure pathways. The results reveal that heavy metal distribution is 
largely controlled by the volcanic parent materials, reflecting natural geochemical 
enrichment. However, cadmium (Cd) and arsenic (As) exhibit pronounced enrichment and 
pose the highest ecological and health-related risks, dominating the overall 
contamination profile. Nickel (Ni) and chromium (Cr) constitute a secondary level of 
concern, whereas concentrations of most other metals generally fall within natural 
background or acceptable geochemical limits. Despite the predominance of natural 
controls, the elevated toxicity, mobility, and bioavailability of Cd and As underscore 
their environmental significance. The study highlights the need for proactive soil-quality 
management in volcanic terrains of the region. Continuous environmental monitoring, 
geospatial risk mapping, and targeted phytoremediation strategies are recommended to 
reduce long-term exposure risks. Furthermore, assessment of crop uptake—particularly 
in tuber and leafy vegetable species—is essential for evaluating food-chain transfer and 
for developing evidence-based guidelines to support sustainable agriculture and public
health protection in the study area.