Phytoremediation potential of some multipurpose tree species of Indian thar desert in oil contaminated soil.

The industrial revolution of the past century has resulted in significant damage to environmental resources such as air, water and soil. Phytoremediation is a promising technology for the cleanup of petroleum contaminated soil. This subject is emerging as a cutting edge area of research gaining commercial significance in the contemporary field of environmental biotechnology. Several microbes, including mycorrhizal and nonmycorrhizal fungi, agricultural and vegetable crops, ornamentals, and wild metal hyperaccumulating plants are being tested both in lab and field conditions for decontaminating the metalliferous substrates in the environment. As on todate about 400 plants that hyperaccumulate metals are reported. In the present work the rhizosphere of Terminalia arjuna (L.) Druce, Anogeissus latifolia (L.) Willd. and Tecomella undulata (L.) Willd. Ex. Del. plants were tested for their abilities to stimulate the microbial degradation of soil pollutants in desert soil contaminated with 2.5-2.6% crude petroleum oil. The results showed that the roots of the three different plants were density associated with total bacteria, fungi and oil-degrading microorganisms, this is confirmed from the (R/S) ratios which ranged from 55.2-250.8 (for total bacteria), 20-131.3 (for fungi) and 95.7-296.1 (for oil degraders). Percentages of oil-degraders were higher in the rhizosphere soil of T. arjuna (65.5%) as compared to the rhizosphere soil of A. latifolia and T. undulata plants (22.5 % and 20.2 % respectively). The results of the biodegradation of oil and its fractions showed that great reduction (26 %) of total petroleum hydrocarbons (TPHs) was observed in the rhizosphere soil of T. arjuna as compared to 15.6 % and 12.8 % reduction in rhizosphere soil of A. latifolia and T. undulata respectively. It was observed also that in the polluted non-cultivated soil the TPHs were reduced by 8.2 10.5 % as a result of biostimulation process only (addition of nutrients).The results also showed that T. arjuna rhizosphere was able to reduce more of the saturated (43.0 %) and more of the aromatics (25.7 %) fractions, compared to (35.2 % and 7.9 %) for A. latifolia and (31.2 % and 4.1 %) for T. undulata rhizospheres. It is of interest to find that 5.3 % of the hardly degradable fraction resins were degraded in rhizosphere soil of T. arjuna. The present results clearly demonstrated that T. arjuna provided successful phytoremediation process of a contaminated desert soil as compared to the other two trees.