“Effect of giant rat’s tail grass (<i>Sporobolus pyramidalis p.beauv</i>) on Total Petroleum Hydrocarbon (TPH) and Heavy metals content of crude oil polluted soils”

Abstract

Soil contamination by crude oil has been an issue within the oil producing areas of the Niger Delta Nigeria and so, many remediation methods; including  phytoremediation, the use of plants, have been adopted for the remediation of the affected soils. Such plants are expected to be safe and effective in the clean-up of hydrocarbons and heavy metals from oil polluted sites. Giant rat’s tail grass (Sporobolus pyramidalis p.beauv) is among the plants being proposed. This study therefore investigated in eight-weeks, the effects of giant rat’s tail grass (Sporobolus pyramidalis p.beauv) on the total petroleum hydrocarbon (TPH) and heavy metals content of contaminated soils. Residual TPH and heavy metals (chromium, Cr and lead, Pb) were quantified as an index for assessing the post-phytoremediated crude oil contaminated soils. Crude oil pollution levels of 25ml/kg, 50ml/kg and 100ml/kg on soils were respectively done alongside the unpolluted control. Remediation treatments of the test soils and the control with the plant were done after two weeks of pollution using three young seedlings of giant rat’s tail grass. Results from eight weeks remediation period showed that TPH (mg/kg) reduced from 496.55 to 257.90, 578.09 to 241.37, 602.61 to 198.80 and 21.27 to 6.22 on the test soils and the control respectively; Cr (mg/kg) from 5.86 to 1.23, 7.96 to 1.38, 9.76 to 1.65 and 4.26 to 0.63 on the test soils and the control respectively; and Pb (mg/kg) from 4.25 to 1.21, 5.26 to 2.31, 5.12 to 3.93 and 1.96 to 0.43 on the test soils and the control respectively. Soil analysis results from the study indicated that giant rat’s tail grass (Sporobolus pyramidalis p.beauv) has the potential to ameliorate crude oil toxicity at different crude oil contamination levels because of its ability to significantly (p>0.05) decrease the TPH and heavy metals content of the soil.

Keywords: Total Petroleum Hydrocarbon, Heavy Metals, Phytoremediation, giant rat’s tail, crude oil contamination