Assessment of Surface Water Quality and Soil Heavy Metal Contamination from Bleulen Dumpsite, Ile-Oluji Municipal, Ondo State, Nigeria

Abstract

This study assessed the effects of a municipal solid waste dumpsite on surface water quality, heavy metals in soil and  ecological risks in Ile-Oluji, Ondo State, Nigeria. Water samples and topsoil (5 - 15 cm) were collected bi-monthly for six months from four stations (upstream, mid-stream, downstream, and recovery sites, respectively) and analysed using standard methods. Soil samples were air-dried, digested and examined for cadmium, lead, arsenic, manganese, and iron using the AAS PG 990 model. Average water temperature of 27.97 ± 0.71°C was recorded at mid-stream station, while pH ranges from 6.0 - 7.3 with peak mean value of 7.08 ± 0.11 observed at upstream. Higher mean values of conductivity, total dissolved solids, chemical oxygen demands, calcium and organic matter occurred at downstream, while highest metal concentration for Cd (4.55 ± 1.00 mg/kg), Pb (7.29 ± 0.56 mg/kg), As (1.39 ± 0.58 mg/kg) and Fe (9981.52 ± 5371.03 mg/kg) occurred at the recovery site. Seasonally, pH, TS, OM and COD were higher in dry season compared to wet season. The ecological risk assessment showed that PLI is >1 at mid-stream, downstream and recovery sites. Also, RI value for the stations after the upstream indicated extreme pollution. Water quality deterioration is closely linked to increase in anthropogenic activities and could have contributed to the high heavy metal concentrations recorded in soils across the sampling stations. There is critical need for better waste management procedures to mitigate the level of metal pollution in order to protect freshwater resources and soil health.