Assessment of Groundwater Contamination by Iron and Manganese from Mining Activities in Zamfara State

This study assesses the contamination of groundwater sources by iron and manganese leaching from artisanal gold mining activities in Zamfara State, North West Nigeria. Artisanal and small-scale gold mining in Zamfara has expanded considerably in the past decade, raising serious environmental and public health concerns about the mobilisation of heavy metals from mine tailings into water supplies used by surrounding communities. Water samples are collected from twelve wells and boreholes within 2 km of mining sites in Anka, Maru, and Gusau Local Government Areas, together with control samples from unaffected locations. Samples are analysed for iron, manganese, arsenic, lead, and total dissolved solids by atomic absorption spectroscopy and ICP-OES. Sediment and tailings samples are collected and characterised by XRF and sequential extraction to assess metal speciation and bioavailability. Mine drainage pH is measured in situ. Results reveal iron concentrations exceeding the WHO drinking water guideline of 0.3 mg/L in 9 of 12 affected samples, and manganese exceeding 0.4 mg/L in 7 samples. Lead is detected above guidelines in 4 samples proximate to active tailings piles. Sequential extraction reveals that iron and manganese are predominantly in exchangeable and reducible fractions, indicating high environmental mobility. The study recommends tailing containment and mine drainage treatment interventions in Zamfara artisanal mining zones. Keywords: groundwater contamination, iron, manganese, artisanal mining, Zamfara State.