Comparative effects of pretreatment of stem cuttings of Chromolaena odorata (Siam weed) with sodium azide and hydroxylamide on the survival and phyoremediative performance in an oil-polluted soil

B Ikhajiagbe,A Akindolor

doi:10.4314/njb.v31i1.5

Abstract

The method of phytoremediation was applied to clean up heavy metals and polyaromatic hydrocarbon contents of a waste engine oil (WEO)-polluted soil, using Chromolaena odorata exposed to sodium azide (NaN3) and hydroxylamine hydrochloride (NH2OH.HCl) solutions respectively. WEO was poured into sun-dried top soil, and thoroughly mixed to obtain 5% w/w concentration in soil. After one month, soil was sown with sodium azide and hydroxylamine hydrochloride pretreated stem cuttings of C. Odorata. Concentrations of either of the mutagenic agents were 0.016%, 0.064%, and 0.25% respectively. Results showed that there was significant decrease in heavy metal and polyaromatic hydrocarbon (PAH) components of soil. Remediation of Cu and Pb by C. Odorata was best at 0.25% NH2OH.HCl treatment. Remediation efficiencies for PAH and heavy metals were better enhanced with the pretreatment of Chromolaena odorata with mutagenic agents. Results also showed that with the increase in concentration of mutagenic solutions required for presoaking, total heavy metal concentration in soil decreased. PAH remediation efficiency was highest (89.88 - 90.99%) when soils were remediated with sodium azide-treated plants than their hydroxylamine hydrochloride counterparts (72.54 - 81.14%). Similar observations were made in heavy metal reduction rates.Keywords: phytoremediation, sodium azide, hydroxylamine hydrochloride, heavy metals, aromatic hydrocarbon

Highlights

The world is one global village with industrialization the building block or backbone of most nations’ economy
Total heavy metal was least in PS3 (16.17 mg/kg), compared to 21.04 mg/kg as total in PS1, 28.43 mg/kg in PX1 and
Reseults of this study showed that pollution of soil by waste engine oil (WEO) brought about increased concentration of heavy metals in the soil

Summary

Introduction

The world is one global village with industrialization the building block or backbone of most nations’ economy. One of the major products of petroleum is engine oil or lubricating oil. Engine oil helps to reduce friction between moving parts of auto machines and engines, prevents corrosion of these auto machines parts. It contains additive chemical substance such as amines, benzene, phenols, barium, lead, zinc, sulphur, magnesium and phosphorus and polyaromatic hydrocarbons and synthetic poly-chlorinated biphenyls. According to Wang et al (2002), engine oil got from automobile (covering up to 3,000km) contains significantly higher concentrations of polyaromatic hydrocarbon (PAH), compared to new lubricating oil which contains only low concentration of polyaromatic hydrocarbon. A major source of oil pollution in the environment is as a result of disposal or discharge of used engine oil from vehicles. Extintion or total death of soil ecosystem and its habitat of living organism is an effect of oil pollution on soil (Akoachere et al.,2008)

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