Costus speciosus (J. Koenig) Sm., a suitable plant species for phytoremediation of crude oil and mercury contaminated soil

Abstract

The aim of this study was to evaluate the efficiency of Costus speciosus in the degradation of crude oil and mercury (Hg) from the contaminated soil in pot experiments in the net house for 180 days. C. speciosus was transplanted in soil containing 19150 mg kg− 1 crude oil and 3.2 mg kg− 1 Hg. The study includes the evaluation of plant height, root length, total petroleum hydrocarbon (TPH) and Hg degradation in soil, TPH and Hg accumulation in plants grown in fertilized and unfertilized pots, and rhizospheric most probable number (MPN) at 60 days interval. The average biomass production and heights of C. speciosus in contaminated treatments were significantly (p < 0.05) lower compared to the unvegetated control. Plants grown in contaminated soil showed relatively reduced root surface area compared to the uncontaminated treatments. TPH degradation in planted fertilized, unplanted and planted unfertilized pot was 63%, 0.8% and 38% respectively. However, compared to unvegetated treatments, TPH degradation was significantly higher (p < 0.05) in vegetated treatments. Comparison of fertilized and unfertilized soils showed that TPH accumulation in plant roots and shoots was relatively higher in fertilized soils. Hg degradation in soil was significantly (p < 0.05) more in planted treatment compared to unplanted treatments. The fertilized soil showed relatively more Hg degradation in soil and its accumulation in roots and shoots of plants in comparison to unfertilized soil. MPN in treatments with plants was significantly greater (p < 0.05) than in without plants. It was observed that C. speciosus accelerated the biodegradation of crude oil and Hg in soil and their accumulation in roots and shoots.