Environmental Impact Assessment of Mining Activities Around Rimin-Zayam, Toro LGA, Bauchi State

Abstract

Mining environment is known for a high level of heavy metals due to the activities which cause adverse alteration of the ecological system. This research study the partitioning of heavy metals in artisanal mining sites in RiminZayan, Toro Local Government Area Bauchi state, Nigeria. The concentration of heavy metals like lead, Cadmium, Iron, Zinc, Cobalt (Co), Copper , Chromium, Manganes and Nickel, were determined using the sequential extraction method recommended by Community Bureau of Reference (BCR) and physic-chemical properties such as the pH, cation exchange capacity, total organic carbon, total organic matter, electrical conductivity and soil particle size. The result show that the soil in the area has a clayey texture with the percentage of clay, slit and sand ranging from 9.29–27.10, 6.31–13.41 and 59.32–84.39 %, respectively. The pH levels of the soil ranged from 6.04 to 6.45 indicating that the soil in thee study is slightly acidic in nature. The observed electrical conductivity (EC) obtained in this study for the samples of soil sediments taken from around the mining site were 26.76, 31,30 and 42.66 µs/cm respectively. The percentages of organic matter of the soil in the same location are 0.423, 0.061 and 0.452 %. Cation exchange capacity (CEC) of the soil in the same vanity were respectively found to be 4.003, 7.385 and 3.994 cmol/kg. The metals were fractionated into six fractions and determined using Atomic Absorption Spectrophotometric techniques (AAS). The results of the soil analysed indicated that there was high abundance of heavy metals such as cadmium, chromium, copper, iron, lead, nickel, and zinc in the residual fraction, pointing to their lithogenic origins, and therefore primarily inherited from the parent material. Cobalt and manganese are bound to other fractions (exchangeable, carbonate, manganese oxide, iron-manganes oxide, organic matter-sulphide, and residual metals which shows their anthropogenic origin. The ratio of bioavailability factor (BF) ranged from 27.47 to 89.66, Contamination factor showed values ranging from 0.001 to 16.299 which suggests that some soils were not contaminated while some were moderately contaminated metals investigated. The degree of contamination (DC) showed that the highest recorded were from non -mining area (19.517) while active mining sites and abandoned mining sites values are: 5.985 and 3.843, respectively. This trend could be owing to the bioavailability and mobility of the metals from the mining sites to non-mining locations. The data generated were subjected to one-way ANOVA. The least significant difference test (p ≤ 0.05).