Identification of Heavy Metals Tolerant Fungi from Mining Sites at Anka Local Government Area of Zamfara State, Nigeria

Abstract

The indiscriminate release of heavy metals into the soil is a major health concern worldwide, as most of these heavy metals cannot be broken down into non-toxic forms. Soil samples were collected from mining and non-mining sites (as control) at Anka Local Government Area of Zamfara State, Nigeria. The soil samples analyzed had a pH ranging from 6.17 to 6.65, and the moisture content ranged from 1.8939 to 9.995%. Various elements, including carbon, potassium, phosphorus, nitrogen, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, and stannum, were detected in the soil samples contaminated with heavy metals. The study investigated the tolerance levels of fungi isolated from mine site soil to iron (Fe), arsenic (Ar), and chromium (Cr). The highest fungal occurrence was Aspergillus niger (38%), followed by Rhizopus sp (24%) and Penicillium sp (11%). Aspergillus fumigatus, Aspergillus flavus, and Fusarium sp each had a 9% frequency of occurrence. The tolerance index (TI) of A. niger, Fusarium sp, and A. fumigatus were tested against Cr, Ar, and Fe at concentrations of 50, 100, and 200 parts per million (ppm). It was discovered that A. niger exhibited the highest tolerance against Fe, with TI values of 0.95 (high tolerance) at 50 ppm, 0.87 (high tolerance) at 100 ppm, and 0.82 (high tolerance) at 200 ppm. For arsenic (Ar), A. niger showed TI values of 0.85 (high tolerance), 0.69 (medium tolerance), and 0.54 (low tolerance), while for chromium (Cr), the TI values were 0.47 (low tolerance), 0.39 (very low tolerance), and 0.34 (very low tolerance). The study also found that A. fumigatus exhibited high tolerance to arsenic and chromium, with TI values of 0.93 (high tolerance), 0.88 (high tolerance), and 0.83 (high tolerance) at 50, 100, and 200 ppm for arsenic, and 0.95 (high tolerance), 0.87 (high tolerance), and 0.82 (high tolerance) for chromium at the same concentrations. Fusarium sp showed a similar pattern, with TI values of 0.96 (high tolerance), 0.85 (high tolerance), and 0.48 (low tolerance) against iron; 0.93 (high tolerance), 0.91 (high tolerance), and 0.84 (high tolerance) against arsenic; and 0.94 (high tolerance), 0.90 (high tolerance), and 0.86 (high tolerance) against chromium at 50, 100, and 200 ppm, respectively. The findings of the study indicate that the fungal isolates were tolerant to Fe, Ar, and Cr, with A. fumigatus displaying the highest tolerance, suggesting that these fungi could be potential candidates for the bioremediation of heavy metal-contaminated soil.