Assessment of Some Heavy Metal Contamination and analysis of Physicochemical Parameters of Surface Soil within the Vicinity of Minna Railway Station, Niger State, Nigeria

The main aim of this study is to determine the levels of soil pollution with heavy metals in the vicinity of a railway station in Minna, Niger state, Nigeria. In this study, 15 soil samples were collected at a depth of 0-15 cm from the vicinity of Minna railway station, Niger State, Nigeria, and analyzed at the chemistry department, Federal University of Technology Minna, Nigeria between May 2009 and November, 2009. The soil samples were acid digested using a mixture of three acids namely, perchloric acid, nitric acid and sulphuric acid in the ratio 2:10:1. The heavy metal (Cu, Zn, Pb) levels in the digested soils were analysed using Atomic Absorption Spectrophotometer. The soil pH was determined by glass electrode pH meter using soil water suspension (1:1). Particle size distribution was determined using hydrometer method. The pH of the soil samples generally ranged from moderately acidic pH (5.54) to neutral pH (7.01). The particles size distribution ranged from 3.04% to 12.48%, 5.28% to 38.56% and 54.40% to 88.40% for clay, silt and sand respectively. The concentrations of the investigated heavy metals ranged from 18.01 mg/kg to 467.50 mg/kg, 54.47 mg/kg to 417.14 mg/kg, and 3.85 mg/kg to106.78 mg/kg for copper, zinc and lead respectively. There is a significant correlation among the analyzed heavy metals; hence the metals may have the same or similar source of input. Heavy metals pollution indices reveal that various sites within the railway station are moderately polluted with copper, zinc and lead according to USEPA and Nigeria DRP guideline for soil quality. Furthermore, I-geo index reveals that the sites are either unpolluted (grade 0) or moderately polluted (grade 1) by copper, zinc and lead. Similarly contamination factor indicates that the sites are moderately contaminated. However, the PLI result reveals that sites R1, R4, R5, R6 and R9 are polluted with copper, zinc and lead, while the other sites are not polluted. Although railway operation has not been previously reported as a major source of heavy metals pollution, this study however suggests that railway operation could be responsible for moderate heavy metal contamination of soil in railway stations or immediate vicinity.