LEAD AND MERCURY CONTAMINATION ASSOCIATED WITH ARTISANAL GOLD MINING IN ANKA, ZAMFARA STATE, NORTH WESTERN NIGERIA: A CONTINUING SERIES OF ENVIRONMENTAL AND HUMAN HEALTH DISASTERS

Widespread artisanal gold mining has continued unabated in the Anka area of Zamfara State of Nigeria despite its adverse environmental consequences and associated human tragedy. An epidemic of lead poisoning was reported in the area in 2010 which caused the death of more than 400 children and more than 4000 under age of five years at risk of death or of serious short and long-term irreversible health effects. The source of the Pb outbreak was from sulfides ore associated with artisanal gold mining and ore processing. The gold and associated Pb-Zn sulfide ore is mined from the nearby villages and processed locally in residential areas. It is crushed and pulverized using mortar and pestle in some cases. Mercury is then used for the amalgamation of the gold. Pb and Hg are released into the immediate environment with serious environmental and human health consequences. This study therefore seeks to understand the extent by which these elements contaminate surrounding soils and their possible effects on human health and how it can be mitigated. A total of 24 soil samples were collected and analyzed for Pb, Hg, and other heavy metals such as As, Cd, Co, Cr, Fe, Ni, U, V and Zn. Soil samples collected in areas around the mines and processing sites showed that the concentrations of Pb and Hg are very high exceeding the established thresholds. Their level of contamination decreases away from mining and processing sites. The assessment of the contamination of the soils based on the index of geoaccumulation (Igeo) and Enrichment Factor (EF), revealed that the soils from mining and mineral processing sites are extremely contaminated essentially originating from the anthropogenic activities. Lead and Mercury are toxic and naturally occurring substances with documented neurotoxin, toxic, and long-lasting adverse health effects globally. The long persistence of these toxic elements in the environment exacerbates their threat to human health. This calls for efficient bioremediation measures for the removal of Pb and Hg from the contaminated soils.