Soil Quality Evaluation and Characterization of the Attendant Non-Carcinogenic and Carcinogenic Risks Around a Carbonate Rock Quarry Region in Ebonyi State Southeastern Nigeria

Soil contamination with toxic elements leads to soil pollution that can compromise the soil quality for agricultural practice, including non-carcinogenic and carcinogenic human health risks. Soil samples were analyzed for acidity (pH) and redox potential (Eh) using a pH meter and redox pH meter, respectively. Toxic trace elements such as arsenic (As), chromium (Cr), iron (Fe), cadmium (Cd), lead (Pb), nickel (Ni), and zinc (Zn) were analyzed using atomic absorption spectrophotometry (AAS). The pH values ranged from 4.69 to 7.95 showing moderately acidic and neutral to weakly alkaline soils. The Eh values ranged from 177 to 367 mv, which is evidence of an oxidizing environment. Values of geo accumulation index (I-geo) showed a dominance of practically uncontaminated (I-geo ≤ 1) soils. As and Cd obtained considerable contamination (3 ≤ Cf < 6) and very high Cf (Cf > 6) at Nkalagu dam and quarry pit at locations 6, 7, 8, 9 and 10. Other elements showed low contamination (Cf < 1). The enrichment factor (Ef) of Ni, Cr, and Cd showed minor enrichments. Pollution index, modified pollution index and Numerow index reflect unpolluted, severely polluted and heavily polluted soils, respectively. Non-carcinogenic risk indicators such as hazard index, average daily intake (ADI) and hazard risk exist only through dermal contact in children with respect to Cr. There is the possibility of 1 in 2725 adults contracting cancer in a lifetime. Cr and Ni showed that in children 1 in 5882 individuals can contract cancer through dermal contact. Cr is the main pollutant causing non-carcinogenic risk in children through dermal contact while Cr and Ni has the potential of causing cancinogenic risk in children and adults through ingestion and dermal contact.