ABSTRACT
Soil is a complex mixture of organic matter, minerals, air, water, and living organisms that serves as a physical anchor for plants, holds nutrients and water, and facilitates gas exchange for root respiration. Land is define as the terrestrial surface of the earth, including the soil, the subsoil, the air space above (up to a certain height), and the ground below, irrespective of ownership This definition highlights the physical components of land and its broad scope. land refers to the surface of the earth, extending downwards to the center and upwards indefinitely into the sky. It includes all things permanently attached to the land, such as buildings, trees, and minerals. Land use refers to the human utilization of land for various purposes such as residential, commercial, industrial, agricultural, recreational, or conservation purposes. Heavy metal accumulation and its influential factors were studied in the different land use soils, which would provide a theoretical basis for controlling the content of heavy metals in soils. The study was conducted in the University of Benin, Benin City to determined heavy metal status on four different land use types (Arable, Commercial, and Forest and Residential land) in the University of Benin, Benin City. The experiment was carried out with two variables (Land use and depth). The soil samples were collected at depth 0-15 cm and 15-30 cm from twelve spots, three from four land use with the use of soil auger, then air-dried for laboratory analysis which was done using standard procedures. Some of the parameters analyzed for were Particle Size Distribution, Total Organic Carbon (TOC), Concentration of Lead(Pb), Cadmium (Cd), Chromium (Cr), Arsenic (As), Copper (Cu), Zinc (Zn), Iron (Fe), Manganese (Mn) and Molybdenum (Mo). Data obtained were subjected to Analysis of Variance (ANOVA) while Duncan’s New Multiple range test was used to separate means at 5% level of significance. The results reveal significant variations in heavy metal levels among the different land uses. Results in the textural class of the various land uses were generally loamy sand at both depths of 0-15 cm and 15-30 cm. The pH was slightly acidic across the various Land uses as follows; arable land (6.89), Commercial land (6.48), the fallow land (5.67) and sport land (5.20). TOC decreased with depths, At 0-15 cm, the values read (18.30 g/kg, 9.52 g/kg, 13.53 g/kg and 9.52 g/kg) for arable land , commercial land , fallow land and sport land, respectively, then at 15- 30 cm depth, the values decreased to (8.80 gkg-¹, 7.20 gkg-¹, 10.07 gkg-¹ and 5.98gkg-¹). All heavy metals (Pb, Cd, Cr, As, Cu, Zn, Fe, Mn and Mo) concentrations decreases with increase in soil depth. The Non-Essential Heavy Metals (Pb, Cr, Cd and As) recorded their highest values in fallow land, Commercial Land , arable and sport respectively (0.107 mg/kg, 0.094 mg/kg, 0.09 mg.kg and 0.053 mg/kg respectively). The Essential Heavy Metals ( Cu, Fe, Mn, Mo and Mn) recorded their highest values in Arable land (32.16 mg/kg, 74.33 mg/kg, 10.41 mg/kg and 0.67 mg/kg respectively) all these at depth 0-15 cm. Fe contains the highest concentration while As has the lowest concentration at both depths except in Arable at depth 0-15 cm where Cd has the lowest value (0.05 mg/kg). Some of the heavy metals were above Permissible limits which can be remedied by Bioremediation, Phytoremediation and Liming.
