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

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