Hydrogeochemical effects of oil shale on soil and water quality in Mbano Area, Southeast, Nigeria

Abstract

Environmental pollution from solid waste landfillings or exposure is of major concern to both the environmentalists and individual citizens. The necessity for studying contaminant generation and control is becoming more urgent in view of the risks associated with such sites. Oil shale and its tailing at Umuezeala Nsu and Umualumaku, were chosen as a case study. Soil samples, water samples and oil shale and its tailings were collected from the site and analyzed for their compositions. The analytical results revealed that the soil and groundwater were contaminated to various degrees by several chemicals or pollutants from the oil shale exposure and its tailings. The major environmental problems associated with the area were acidification of soil and groundwater, high content of heavy metals and sulphate in soil and groundwater and organic contamination of soil and in particular, carcinogenous benzo[a] pyrene and other polycyclic aromatic hydrocarbons (PAHs). Geochemical method was applied to reveal the sources of the contaminants. Soil and groundwater contamination show that the nearer the sampling area to the oil shale or its tailing, the heavier the soil and groundwater contamination. The different water sample compositions have same chemical characteristics. The soil and water samples were analyzed for 14 PAHs. The result shows that PAHs were retained mostly in the soil, which consisted of mainly naphthalene, fluorene, phenanthrene and anthracene. Analysis for PAHs source revealed that they were also from the oil shale and its tailing.

Keywords: oil shale waste, soil contamination, groundwater contamination, PAHs