Concentration of Heavy Metals and Determination of Bioremediation Potential of Some Species of Oyster Mushrooms (Pleurotus Spp) in the soil of Gold Mining Site

Intensive environmental exploitation by Man has led to the emergence of a key sector – mining sector which, to a very great extent has been undertaken for its economic benefits. Inspite of the beneficial aspect of the sector, it produces hazardous wastes, causing various degrees of damages and threats to plant and animals in an ecosystem. This research was aimed at evaluating bioremediation potential of 2 species of oyster mushrooms (Pleurotus ostreatus and Pleurotus polmonarius) in the degradation of heavy metals contained in the soil of gold mining site located at Paiko, Niger State of Nigeria. Concentrations of the heavy metals detected in the soil samples were determined. Media were prepared with appropriate substrates and later inoculated with pure cultured spawns of the 2 species within 3, 6 and 9 weeks treatment intervals for determination of growth factors and concentrations of the heavy metals in the Pleurutus species. The Bioaccumulation Factor (BAF) for each of the 2 species was determined and compared. Results obtained showed different mean concentrations for the metals detected (4.851mg/kg, 51.826mg/kg and 121mg/kg) for cadmium, chromium and zinc respectively. Also detected were nickel (23.245mg/kg) and lead (10.925mg/kg). Results of the growth parameters indicated that Pleurotus ostreatus was higher in height (7.42cm) than Pleurotus polmonarius (5.68cm). For the stipe length, Pleurotus ostreatus was longer (4.7cm) than Pleurotus polmonarius (3.4cm). In diameter of Pileus, Pleurotus ostreatus had higher fruiting bodies of 25 than Pleurotus polmonarius which has 22. The total yield measured after harvest were 42.31g and 39.56g for Pleurotus ostreatus and Pleurotus polmonarius respectively. The dry matter contents were 6.39g and 6.06g respectively for Pleurotus ostreatus and Pleurotus polmonarius. Also the biological efficiencies for the 2 species were 42.31% and 39.56% respectively. The results indicated higher concentrations of metals in the mycelia of the species than Pleurotus ostreatus which had 0.573mg/kg of cadmium, 0.813mg/kg of chromium and 0.231mg/kg lead all after 9 weeks of inoculation. While Pleurotus polmonarius had higher concentrations of 0.253mg/kg and 0.549mg/kg of nickel and zinc respectively after 9 weeks of inoculation. For the BAF of the 2 species, Pleurotus ostreatus had higher potential (0.150) for cadmium in 6 weeks treatment and 0.026 for lead after 9 weeks, while Pleurotus polmonarius had higher BAF of 0.08 for nickel and 0.006 for zinc after 9 weeks of treatment. Finally it was concluded that the species showed significant bioremediation potential.