Heavy Metal Accumulation by Oyster Mushroom (Pleurotus Ostreatus) Cultivated on Agricultural Land Irrigated by Akaki River
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Date
2015-10
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Addis Ababa University
Abstract
The accumulation of heavy metals in agricultural soils is of increasing concern due to the food safety issue and potential health risks. Sources of these elements in soils mainly include industries and human activities. International and national regulations on food quality have lowered the maximum permissible levels of toxic metals in the food items due to an increased awareness of the risk these metals pose to food chain contamination. Remediation of soil contaminated with heavy metals has received considerable attention in recent years. So, looking to the severity of problem due to heavy metals contamination and there need of remediation, the present study was conducted on experimental site soil situated near Aba Samuel dam build on Akaki river followed by control. The study was conducted on the effects of heavy metal contamination accumulated in selected commonly available edible mushroom (Pleurotus ostreatus) along with bioaccumulation potential of selected mushroom species for heavy metals (Cd, Cr, Cu, Pb, Ni & Zn). The effects of waste water on selected site soil samples were conducted by means of first and second cultivation of mushroom. Positive affect of mushroom cultivation were found on waste water irrigated soil properties due to improvement in soil pH, EC followed by reduced concentration of heavy metals. The results of soil analysis indicate that the selected mushroom species is able to bio-remediate the high heavy metals (Cr, Cu, Pb and Zn) concentration from contaminated soil. Results also indicated the need of further cultivation of mushroom to bioremediate the heavy metals (Cr, Pb & Zn) up to safe level in contaminated site soil. The highly significant negative correlations was found between pH and Cr, Pb & Zn; Significant positive correlation was between organic matter and Cu, Pb & Zn; Electrical conductivity (EC) and Cr. Bioaccumulation of heavy metals in mushroom has significantly decreased the yield parameters (color, total numbers of buds, average height, pileus diameter, stem thickness, total mass and ash content) and biochemical values (protein) in mushroom during the both first and second cultivation. Significantly higher nutrient contents (Ca, Fe, K, NO3- & PO42-) were found in comparison to control indicated the presence of high nutrient content in soil due to wastewater irrigation. Cr, Cu, Pb and Zn were significantly bioaccumulated in both first and second cultivated mushroom in comparison to control indicating the better bioaccumulation potential of selected species mushrooms. Cr and Pb metal levels were found higher than maximum permissible limit (FAO/WHO, 2001) for mushroom sample cultivated on experimental site soil for both first and second cultivation indicating the possible heavy metals related health hazards upon consumption of contaminated mushroom as well as further pollution after their improper disposal. Other heavy metals will also be future health hazard at selected site if the current practice of mushroom or any agricultural crop and vegetable production will be continued in long run without proper heavy metal remediation.
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Keywords
Aba Samuel Dam, Bioaccumulation, Edible Mushroom, Heavy Metals, Waste Water Irrigated Soil