Bitumen Seepage: Impact and Interaction on Heavy Metal Concentrations in Surface Water
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Date
2019
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Abstract
The association and interaction among metals in bitumen polluted water may affect the availability of the
metals even at toxic levels to the surrounding environment and biota that are dependent on such water. The
study was carried out at Ode-Irele in Ondo State bitumen belt, Southwest of Nigeria, where there are bitumen
seepages, and Ebute-Irele where there are no records of seepages served as control. Composite samples of
surface water were collected to a depth of 30cm midstream on the sites. Heavy metals – Manganese, Iron,
copper, zinc, lead, chromium, cadmium, nickel, vanadium, arsenic, calcium, magnesium, potassium, and
sodium were determined using standard methods. Data on metals’ concentrations were analyzed using
descriptive statistics and t-test at p < 0.05. The associations that exist among metals of surface water were
analysed using regressive correlation to determine which metal increased or decreased with rise and fall in the
level of other metals. Values obtained were compared with Federal Environmental Protection (FEPA) and
World Health Organisation (WHO) Guidelines. Results of the study revealed that nickel, calcium, magnesium,
and sodium were higher in seepage site than that of control, but, nickel was significantly higher in surface
water of seepage site, 0.40 ± 0.00mgL-1 than that of control, 0.30 ± 0.00mgL-1. Manganese, iron, copper,
zinc, chromium, cadmium, nickel, vanadium, and arsenic, as well as calcium were higher than guideline levels.
Nickel, iron, manganese, vanadium, calcium and sodium which are elemental components of bitumen could
pose serious environmental problems. There were significant positive associations between iron and copper,
manganese and vanadium, iron and sodium, calcium and magnesium, as well as between magnesium and
sodium. The finding also revealed significant negative association between lead and zinc. The heavy metals in
surface water that were higher in seepage site and higher than guideline values in Ondo State bitumen belt
and especially those that are elemental components of bitumen could have toxic effects on the environment,
and so they should be closely monitored during the bitumen development phase.
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Keywords
Bitumen, Concentration, Heavy metal, Toxic, Water