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. Soil health refers to the capacity of soil to function effectively within the ecosystem and sustain biological productivity, maintain environmental quality, and promote plant, animal, and human health. 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. 10 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 moderately acidic across the various Land uses as follows; residential land (6.0), Commercial land (5.94), the Arable land (5.82) and Forest land (5.61). TOC decreased with depths, At 0-15 cm, the values read (19.67 g/kg, 18.30 g/kg, 11.65 g/kg and 9.52 g/kg) for forest land, arable land, residential lands and commercial land, respectively, then at 15-30 cm depth, the values decreased to (8.80 gkg-¹, 7.20 gkg-¹, 16.01 gkg-¹ and 7.37 gkg-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) all recorded their highest values in Commercial Land (0.15 mg/kg, 0.107 mg/kg, 0.09 mg.kg and 0.050 mg/kg respectively). The Essential Heavy Metals ( Cu, Fe, Mn, Mo and Mn) also recorded their highest values in Forest Land (33.34 mg/kg, 76.21 mg/kg, 10.49 mg/kg and 0.69 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.
