Health Risk Assessment of Heavy Metals in Soil around Metal Scrap Recycling Areas during Wet and Dry Seasons in Ogijo, Ogun State, SW Nigeria

Abstract

Aim: The aim of the study is to investigate the levels and risks associated with heavy metals in the soil samples collected during the dry and wet seasons around metal scrap recycling areas in Ogijo, Ogun State.
 Study Design: The soil samples were collected randomly within the industries and communities in the vicinity of the scrap metal recycling industries (SMRI) and analyzed with XRF.
 Place and Duration of Study: The study was carried out in Ogijo in Sagamu Local Government Area, Ogun State, located within Southwestern Nigeria. The soil samples were collected in dry and wet seasons (5th to 7th March and 24th to 25th September 2020 respectively.
 Methodology: Soil samples within the industries and communities in the vicinity of the SMR were collected randomly, dried, and then sieved through a 2mm mesh stainless sieve. The sieved sample was analyzed for heavy metal concentration by using S2 Ranger, and Bruker UKX-Ray Fluorescence Spectroscopy techniques (XRF).
 Results: The results of the analyzed soil showed that the range of concentrations of heavy metals in the soil samples collected during dry season were: Fe (40100 - 87300 mg/kg); Mn (400 - 3500 mg/kg); Zn (600 -1300 mg/kg); Pb (400 - 1000 mg/kg) and during wet season: Fe (26100 -82700); Mn (500- 4200) mg/kg. Zn (600 – 1300) mg/kg; and Pb were only detected in S3 sample (600mg/kg). The results of the heavy metals were found to exceed the WHO permissible limits of heavy metals. Contamination index, degree of contamination, and pollution load indices indicated slight contamination to excessive pollution, very high risk of the degree of contamination, and extremely polluted soils respectively. The geo-accumulation index was uncontaminated to moderate contamination (0<Igeo≤1) with different metals at different locations that were not detected and with all the detected Zn concentrations (except at S1) to extreme contamination (Igeo≥5).Heavy metal enrichment during both dry and wet seasons ranged from background rank (EF ≤ 1) to moderate enrichment. Eri values ranged from low (Eri) <40) to moderate ecological risk (Eri > 80) with all the risk indices of the locations low (RI <150). The cumulative non-carcinogenic, health index (HI) for ingestion and dermal for soil during the dry season were all above 1 indicating non - carcinogenic health concerns for the residents of the study areas as they recorded higher values. The CRI was far above the acceptable limit indicating that residents in S3 during the wet season and S2 and S9 during the dry season have the probability of contracting cancer through ingestion within the life time of 70 years.
 Conclusion: The results of pollution indices show that the quality of soil in the study entirely deteriorated with respect to the DPR background. This indicates that the soil could not be used for any agricultural or domestic purposes.