Phytoremediation of crude oil-contaminated soil employing Crotalaria pallida Aiton

The purpose of the study was to evaluate the phytoremediation potentiality of a herb named Crotalaria pallida which are abundantly grown on crude oil-contaminated soil of oil field situated at upper Assam, India, so that this plant could be used to remediate hydrocarbon from contaminated soil. To evaluate the potentiality of the plant, a pot culture experiment was conducted taking 3 kg of rice field soil mixed with crude oil at a concentration of 10,000 (10 g/kg), 20,000 (20 g/kg), 30,000 (30 g/kg), 40,000 (40 g/kg), 50,000 (50 g/kg), 60,000 (60 g/kg), 70,000 (70 g/kg), 80,000 (80 g/kg), 90,000 (90 g/kg), and 100,000 (100 g/kg) ppm. Ten numbers of healthy seeds of C. pallida were sown in three pots of each concentration for germination, and after 15 days of germination, single healthy seedling in each pot was kept for the study. A control setup was also maintained without adding crude oil. The duration of the experiment was fixed for 6 months. The results showed that uptake of hydrocarbon by the plants was increased with increasing the concentration of crude oil in the soil up to 60,000 ppm. After that, uptake of hydrocarbon by the plants was found to be lower with increasing doses of crude oil concentration. Uptake of hydrocarbon by the shoot was found to be maximum, i.e., 35,018 ppm in 60,000 ppm concentration. Dissipation of total petroleum hydrocarbon (TPH) from the soil was also gradually increased with increasing concentration of crude oil in the soil up to 60,000 ppm. Maximum dissipation, i.e., 78.66 %, occurred in 60,000 ppm concentration of crude oil-mixed soil. The plant could not survive in 100,000 ppm concentration of crude oil-mixed soil. The results also demonstrated that there was a reduction in plant shoot and root biomass with an increase of crude oil concentration. Furthermore, results revealed that the shoot biomass was higher than root biomass in all the treatments.