Using aspergillus niger to bioremediate soils contaminated by heavy metals

Abstract A bioremediation process was developed using the fungus AspergiUus niger to produce weak organic acids for the leaching of heavy metals from contaminated soils. The fungus was cultivated on the surface of three contaminated soils (a clay loam, a loam, and a sandy clay loam) for 15 days at 30°C and at a pH <4 to favor the production of citric acid rather than oxalic acid which hinders Pb leaching. For the clay loam, Cr, Mn, Pb, and Hg were leached to levels of 37, 41, 85, and 91%, respectively. For the loam, the leaching of Cd and Pb was found to reach levels of 99.7 and 83%, respectively. For the sandy clay loam, Cd, Cu, Pb, and Zn were leached to levels of 99,94,58, and 99%, respectively. The three contaminated soils could have been remediated to the A category of the Province of Quebec standards for heavy metals after 20 to 25 days of leaching using this technique.