Changes in metals and polyaromatic hydrocarbon contents of a spent lubrication oil-polluted soil after exposure to sodium azide and hydroxlamine hydrochloride solutions: implications for intrinsic bioremediation

Abstract

The study investigated the changes in heavy metals and polyaromatic hydrocarbon contents of an oil-polluted soil as a result of exposure to sodium azide and hydroxylamine hydrochloride. Measured 5kg of Oil-polluted soils (5%w/w), placed in experimental buckets, were saturated with solutions of sodium azide and hydroxylamine hydrochloride in 3 different concentrations (0.0625, 0.0312 and 0.0156 %v/w) respectively. The entire set up was observed in a well-ventilated Screen House for 3 months. Results showed that experimental concentrations of both mutagenic agents had no significant effect (p>0.05) on Fe concentration of soil (998.8 – 1106.2 mg/kg). Although soil levels of Fe exceeded permissible levels by over 5 times, concentrations of Mn, Cd, Ni, and V were below detection limits (<0.001 mg/kg) after application of chemical agents. Hydroxylamine HCl-moistened soil presented enhanced remediative capabilities for chromium (Cr = <0.001 mg/kg) than with sodium azide (Cr = 8.29 - 13.11 mg/kg). Sodium azide did not significantly enhance Cr remediation, compared to the control. Reductions in PAH fractions in the treated soils were better than in the control soils. Efficiency of PAH reduction in the control was 60.47%. application of mutagenic agents to polluted soils at lower to moderate concentrations significantly enhanced remediation efficiency to 80.95 -89.27%. Generally, however, hydroxylamine HCl showed better prospects in the enhancement of remediation (at lower to moderate levels) than did sodium azide.