Impact of Pb-Zn Mining on Heavy Metal Levels in Soil from Arufu Mine Field, Wukari, Nigeria

Analysis of soil around the vicinity of Arufu mine field was conducted in order to ascertain the impact of mining on the environment. Concentrations of trace metals associated with Pb – Zn – barite mineralization were determine in soils using atomic absorption spectrophotometer (AAS) Varian AA 240, after acid digestion with a mixture of 1:1 hydrofluoric acid and aqua regia. Mean concentrations (µg/g) of metals ranged from 5.72 (As) – 451.44 (Pb) in dry season and 1.32 (Cd) – 504.61 (Pb) in wet season. Index of geoaccumulation were in the following order of increasing magnitude: Cu < Zn < As < Pb < Ag for dry season and Cu < As < Zn < Cd < Pb for wet season. On the other hand, soil enrichment ratio ranged from Cu (1.06) – Ag (126.18) and Cu (1.35) – Pb (34.10) in dry and wet season respectively. Levels of metals measured were higher than their corresponding values reported for soil in the upper continental crusts. Toxic metal (Pb) has its mean concentration above maximum tolerance level while Zn and As levels were below the maximum tolerable levels. The presence of Pb above maximum tolerance level may render the soil unsuitable for agricultural practices, hence high impacts of Pb – Zn mining in the study area.