Assessment of BTEX Concentration in Soils and Earthworm (Aporrectodea Longa) From Two Automobile Workshops in Benin City, Southern Nigeria

Abstract

Automobile workshops are known to be sources of release of hydrocarbons from spent engine oil and gasoline into the terrestrial environment where they may be accumulated by soil in fauna such as earthworms. These hydrocarbon wastes often contain benzene, toluene, ethylbenzene and xylene. This study was carried out to determine the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) in soil and earthworm from selected auto mechanic workshops from Isihor and Agbor Park areas in Benin City. Soil and earthworm samples were collected for three months and the samples were prepared and analysed to determine the concentrations of BTEX. The soil and earthworm extraction were carried out using the EPA 5021 Method. Some physical and chemical properties of soil were analysed using standard procedures while BTEX was analysed using Gas Chromatograph Agilent 6890 Series, with an FID detector. The results showed that only benzene was detected in the soil at the end of the study. Toluene, ethylbenzene and xylene were below detection limits probably due to volatilization. Mean concentrations for benzene throughout the study period for soil and earthworm were 9.03±4.34 and 6.10±2.95 µg/kg respectively for site A, while the mean concentrations for benzene for soil and earthworm were 13.42±5.35 and 15.02±3.44 µg/kg respectively for site B. The percentage concentration of Benzene compound analysed in the soil and earthworm was at 52% for soil while 48% was recorded for earthworms. An inverse correlation was observed between the concentration of BTEX and pH, EC, Fe, Mn, Zn, Cu, Cr, THC, clay and silt content of the soil. Currently, there are no standards/limits available for BTEX concentrations in soil and earthworm for comparison.