Analysis of Heavy Metal Contamination in Soils of Artisanal Gold Mining Areas in Zamfara State

This study analyses heavy metal contamination in agricultural and residential soils adjacent to artisanal gold mining operations in Zamfara State, North West Nigeria. Zamfara State has experienced significant artisanal and small-scale gold mining activity using mercury amalgamation techniques, which have been associated with severe lead and mercury contamination resulting in documented child fatalities and morbidity from acute heavy metal poisoning. Soil samples were collected from forty-two locations across three active mining communities and two control villages at depths of zero to fifteen centimetres and fifteen to thirty centimetres. Samples were digested using aqua regia and analysed for lead, mercury, arsenic, cadmium, and zinc concentrations using atomic absorption spectrophotometry. Results confirm extreme lead contamination, with concentrations exceeding 10,000 milligrams per kilogram in ore processing areas, far above the Dutch target value of 85 milligrams per kilogram. Mercury concentrations at amalgamation sites reach 1,200 milligrams per kilogram. Agricultural soils adjacent to processing areas show lead concentrations between 300 and 800 milligrams per kilogram, substantially above phytotoxicity thresholds. Arsenic and cadmium elevations are also detected in soils near mineralised ore stockpiles. Vertical distribution profiles confirm surface enrichment with limited but detectable downward migration. These findings characterise the contamination footprint to guide remediation design, which should prioritise soil capping, stabilisation, and removal from residential play areas. Keywords: heavy metal contamination, artisanal mining, lead pollution, mercury, Zamfara State.