International Journal of scientific research and management (IJSRM) ||Volume||3||Issue||3||Pages|| 2211-2217||2015|| \ Website: www.ijsrm.in ISSN (e): 2321-3418 Sallau, A.K 1 IJSRM volume 3 issue 3 March 2015 [www.ijsrm.in] Page 2211 Assessment of Some Potentially Toxic Inorganic Contaminants in Soil of the Obi Coalfield, Middle Benue Trough, Nigeria Sallau, A.K 1 , Adamu M.S 2 , Mangs A.D 2 , Lar U.A 2 1 The Carter Center Nigeria 73 Tudun Wada Ring Road,Jos - Plateau, Nigeria adamusallau@yahoo.com 2 Department of Geology, University of Jos 241 Bauchi Road, Jos - Plateau, Nigeria murtalasule@yahoo.com mangsdanmangu@gmail.com ualexanderlar@yahoo.co.uk Abstract:The study area has occurrences of coal, limestone and sulphide minerals, with ubiquitous artisanal mining activities. This research assesses heavy metal accumulation in soil of the area, using pollution indices such as geo-accumulation index (I geo ), enrichment factor (EF), contamination factor (CF) and pollution load index (PLI). A total of 13 soil samples were analyzed for As, Ba, Co, Cr, Cu, Mo, Ni, Pb, Sc, Sr and Zn, using ICP-OES geochemical technique. Results show that soil in the area are extremely polluted by Ni, Cr and Zn, having I geo values of 5.88, 3.56 and 2.43 respectively, going by geo-accumulation index. I geo levels of Pb, Cr and Ba indicate moderate to no pollution. Enrichment factor analysis, again show that Ni and Cr have EF of 147.17 and 79.66 respectively, indicating the two are extremely severely enriched in the environment, while Zn, Co and Sr with EF between 6 and 15, indicate moderate enrichment. Cu, Mo and As levels in soil remain very low, indicating the media are not contaminated by these elements. Most of the locations showed a PLI less than one (1) in the ranking, indicating no serious pollution occurring. The high I geo and EF values recorded for some heavy metals are related to mining, mineral processing as well as the sub-standard practice dumping of mine wastes and tailings, in addition to natural weathering, releasing these elements into the environment. The nature and source of enrichment of these elements can therefore be said to be anthropogenic. Pathways of exposure of the human population to the heavy metals were found to be through dust inhalation, from the mouth through the ingestion of food and water as well as through the skin, resulting from the close association of the population to the land/soil due to farming and water used for drinking and other domestic uses. These can result to varied human health risks if the population is continually exposed. High doses of Ni and Cr can cause lung, nasal and possible stomach cancer may develop. Also, elements such as Pb and As, are known to be toxic even at very low exposure, also, with carcinogenic effects. It is recommended here that the quality of drinking and irrigation water as well as some crops grown from the area be investigated and quality determined, with regards to the levels of heavy metals in such media, thereby determining whether the population is safe or not. This should include massive awareness campaign for the miners and the mining communities, so as to forestall any negative eventuality. Keywords:Environment, Heavy metals, Contamination, Health 1. Introduction Environmental issues such as soil contamination have become a serious concern in many advanced societies with high industrial activities and high population density as well as developing countries where the population is mostly rural and land is intensely used for subsistent agricultural activities. Soil is regarded as polluted when trace metals are present above normal abundances or when other alterations have been made to its natural environment [1],[2]. The presence of the different mineral occurrences in the area and the subsequent natural and human activities, have generally affected the baseline levels of the inorganic contaminants, leading to the very high concentration (of elements such as Ni, Zn, Cr) recorded in the study area. Soil pollution is usually caused by accidental releases of chemicals (pesticides, etc) or the indiscriminate/improper disposal of hazardous mine wastes and tailings, as well as natural processes trough weathering activities, practically releasing potentially toxic trace elements into agricultural soils, sediments and natural waters, coupled with inadequate environmental management practices. These chemical elements in the terrestrial environment may become absorbed by plants and subsequently into human body through the food chain, thereby posing a significant risk to the environment, human and animal health [3]-[8]. It has been established that trace elements such as Cu, Zn, I and Se are essential for normal plant and human growth and well-being but are however toxic in high concentrations. Also, concentrations of some heavy metals such as Pb, As and Cd above permissible limits are known to be toxic and deleterious to living organisms. Soluble metal compounds and metals held in metal exchange complexes are considered to be available for vegetation uptake and the bio-availability itself is influenced by physico-chemical characteristics such as pH, temperature, redox potential, cation-exchange potential of the solid phase, competition with other metal ions, composition and quality of the soil solution [9]. This study has been necessitated by the many years of exposure of the rural population living in the mining areas of Obi and also in view of the dearth of information (data) on trace elements levels in soil, sediments and water as the people continue to depend on these basic life support media for their survival. The main objective of this study is therefore to assess the level of soil contamination (of elements such as Se, I, Pb, As, Zn, Cd, and Cr) and to identify possible sources of contamination in the area. It is clear from the study that the proliferation of mining activities characterized by indiscriminate dumping of mine