Human Risk on Heavy Metal Pollution and Bioaccumulation Factor in Soil and Some Edible Vegetables around Active Auto-Mechanic Workshop in Chanchaga Minna Niger State, Nigeria

Abstract

Heavy metal contamination arises from the disposal of used engine oil which is one of the environmental problems in Nigeria and is more widespread than crude oil pollution. The aim of this research is to evaluate the human risk of heavy metal and its bioaccumulation factor in soil and some edible vegetables around active auto-mechanic workshop in Chanchaga Minna Niger State, Nigeria. Soil samples were collected at 15-20 cm depth with the aid of soil auger and a control sample was also collected (generally about 100 m away from each cluster) where neither car repairs, industrial nor commercial activities are carried out. All vegetable Fluted pumpkin (Telfairia occidentalis), Jute mallow (Corchorus olitorius), water leaf (Talinum triangulare), Roselle (Hibiscus sabdariffa) and African spinach (Amaranthus cruentus) samples were collected from farms close to the workshop. The soil samples were collected at random and physicochemical parameters such as pH, total nitrogen, total phosphorus, organic matter and exchangeable cations (i.e., K+, Mg2+ and Na+) using a standard method and concentrations of the heavy metals in soils and vegetables, As, Cd, Hg and Pb were analyze using Flame Atomic Absorption Spectrometer (FAAS). The bioaccumulation factor and the risk health risk assessment from the consumption of these vegetables was calculated using standard methods and formulas. The physicochemical properties shows a significant (P<0.05) different in the auto mechanic soil and the control soil. The soil samples from auto-mechanic workshops in Chanchaga revealed elevated levels of heavy metals than the control. The concentration of all heavy metal in vegetables exceeded the permissible limits of 0.5, 0.2, 0.1 and 0.3 mg/kg for As, Cd, Hg and Pb respectively as prescribed by FAO/WHO. The Bioaccumulation factor shows that metals are transferred from the contaminated soil to the vegetable with Hg in Talinum triangulare greater than one. The estimated health risk shows that children are more prone to toxic elements from the consumption of these vegetables grown around auto mechanic site. The research conclude that these auto mechanic workshops accumulate potentially toxic elements in the soil and do have a negative impact on the plants, human and surrounding environment, which calls for stricter regulation on their location within cities.