Seasonal Variations and Health Risk Assessments of Heavy Metals in Soils around Metal Scrap Recycling Industrial Areas of Ogijo, Ogun State, SW Nigeria

Abstract

This chapter aimed to assess the levels of heavy metals in soils from metal recycling facilities that converts scrap materials into steel products in Ogijo, Ogun State, Nigeria. Shortage of iron ore in Nigeria has led to the proliferation of metal recycling in urban centres and suburbs, where waste and scavenged metals are rolled to steel. This constitutes a major source of environmental pollution that contaminates the country's environment. The soil samples were randomly collected in dry and wet seasons (5th to 7th March and 24th to 25th September 2020 respectively) within the industries and communities in the vicinity of the scrap metal recycling industries (SMRI). The physico-chemical properties of the soil revealed that the soils range from slightly acidic to slightly alkaline, mostly sandy and loam and of moderate fertility. The concentrations of the analyzed heavy metals in the soils were found to exceed the WHO permissible limits of heavy metals. Pollution assessment models are indicators used to assess the presence and intensity of anthropogenic contaminant deposition on soils. In this study, the following pollution assessment models were employed: Contamination Index (CI), Pollution Load Index (PLI), Contamination Degree (CD), Geo-accumulation Index (Igeo), ecological factors, risk index and Nemerow Index.

Heavy metal enrichment during both dry and wet seasons ranged from background rank (EF \(\le\) 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, the health index (HI) for ingestion and dermal for soil during the dry season were all above 1 indicating non - carcinogenic health concern 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 wet season and S2 and S9 during the dry season have probability of contracting cancer through ingestion within the life time of 70 years. Scrapyards  are  haphazardly  sited  in  the areas  where  all  kinds  of  scraps  from  abandoned automobiles,  machineries,  and  electrical  appliances  are disassembled and recycled for further uses. Many of these scrap  materials  are  made  up  of  materials that  are toxic and  adversely  affect  the environment  after improper management.  According to the pollution index data, the soil quality in the study completely declined as compared to the DPR background. This suggests that the soil cannot be utilised for home or agricultural purposes.