Urbanisation of Benin City Metropolis and Impacts on the Quality of Soil and Borehole Water around Selected Dumpsites in Edo State, Nigeria

Benin City has witnessed an unprecedented population growth, increased urban activities and consumption, all of which have exacerbated the existing problem of poor solid waste disposal and management in the City. Thus, the present study aims to examine the impact of Municipal Solid Waste (MSW) dumpsite on the levels of heavy metals in soils and private bore wells in private residences in parts of Benin City. Soil, borehole and information on solid waste components were collected from the archives of the National Centre for Energy and Environment, University of Benin, Edo State, Nigeria. Soil and water samples were tested for iron (Fe), Zinc (Zn), Copper (Cu), Chromium (Cr), Cadmium (Cd), and Lead (Pb). Landsat 8 satellite imagery for Benin City spanning the years 2010 to 2022 was acquired from the U.S Geological Survey Earth Explorer platform. This imagery was used to provide a comprehensive view of the city's landscape over twelve years, allowing for a detailed analysis of land cover changes. The study revealed increasing urbanisation within the areas of interest over time, with 2010 having the lowest urban land use of 23.97%. Urban land use activities continued to increase through 2014 and 2018, reaching their highest point in 2022. High concentrations of heavy metals in soils at both dumpsites were observed, with Fe having the highest mean concentration of 232.73 mg/L recorded at Oluko dump site. This was higher than the mean concentration of Fe (123.1 mg/L) recorded at the Ikhueniro dump site. More so, except for iron, which was above the maximum permissible limit for drinking water according to the World Health Organization standard, other heavy metals investigated were within the WHO permissible limits. The study shows the following sequence of MSW components from highest to least: organic waste>paper>plastic>wood>glass>ceramic>metal. The frequency of organic waste for Oluku and Ikhueniro dump sites was 47kg (31.3%) and 51kg (27.9%), respectively. There is therefore a need for more sensitisation and awareness creation programmes to enlighten the public on the importance of solid waste sorting. Schools should also develop a curriculum on MSW sorting as a way of promoting early awareness and standard practices.