Assessment of Heavy Metals and Polycyclic Aromatic Hydrocarbons in Soil and Water in Selected Mining Areas of Ebonyi State, Nigeria

Abstract

Mining activities frequently introduce hazardous compounds, including heavy metals and polycyclic aromatic hydrocarbons (PAHs), into soil and water systems, resulting in significant environmental contamination. This study assessed the levels of heavy metals and PAHs in soil and water samples collected from five mining sites in Ebonyi State: Okposi, Amasiri, Akpuoha, Isiagu, and Uburu while Afikpo served as a control site due to little or no mining activities. Using standard analytical techniques, the concentrations of heavy metals were determined using Atomic Absorption Spectrophotometer, the concentration of Polycyclic Aromatic Hydrocarbons were determined using Gas Chromatography coupled with Flame Ionization Detector and the physicochemical properties of the samples such as pH, Organic matter, total dissolved solids etc. were determined. The results revealed that soil samples contained heavy metal levels exceeding NESREA (National Environmental Standards and Regulations Enforcement Agency) regulatory limits, with arsenic ranging from 145.90 to 600 mg/kg, cadmium from 3.64 to 7.68 mg/kg, and lead from 167.44 to 252.71 mg/kg and were all above the permissible limit. Similarly, water samples from the mining sites showed elevated concentrations of manganese (0.07–0.54 mg/L) and lead (0.71–1.44 mg/L), surpassing the Nigerian Industrial Standard (NIS) limits of 0.2 mg/L and 0.01 mg/L, respectively. PAH concentrations in soil ranged from 0.091 to 1.518 µg/kg, while water samples exhibited values between 0.006 and 1.780 µg/L, with naphthalene identified as the most prevalent compound. These findings indicate that mining operations have significantly contaminated the environment especially in Akpuoha and Okposi sites, posing potential risks to both ecosystems and human health. To mitigate these hazards, pre-treatment of water, soil remediation, and enhanced community awareness are permissible.