Vol. 1, Issue 12, Part J (2015)

Abstract
Soil contamination or soil pollution or it can be also said "Land Pollution" is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. Phytoremediation is a promising technology for the cleanup of polycyclic aromatic hydrocarbon contaminated soil. In the present work the rhizosphere of Acacia nilotica (L.). Ex. Del. plants were tested for their abilities to stimulate the microbial degradation of soil pollutants in desert soil contaminated with 2.1-2.7% polycyclic aromatic hydrocarbons. The results showed that the roots of the different plants were density associated with total bacteria, fungi and PAH (polycyclic aromatic hydrocarbon)-degrading microorganisms, this is confirmed from the (R⁺/S⁺) ratios which ranged from 55.6-258.2 (for total bacteria), 20-125.1 (for fungi) and 95.7-348.2 (for PAH degraders). Percentages of PAH-degraders were higher in the rhizosphere soil of A. nilotica 25.1-25.9 % respectively. The results of the biodegradation of PAH-I, II & III and its fractions showed that great reduction (25.4%) of total polycyclic aromatic hydrocarbons (TPAHs) was observed in the rhizosphere soil of A. nilotica respectively. It was observed also that in the polluted non-cultivated soil the PAHs were reduced by 8.1 -10.5 % as a result of bio stimulation process only (addition of nutrients). The results also showed that A. nilotica rhizosphere was able to reduce more of the saturated (25-25.9%) and more of the aromatics (3.5-3.8%) fractions. It is of interest to find that 5.2 % of the hardly degradable fraction resins were degraded in rhizosphere soil of A. nilotica. The present results clearly demonstrated that A. nilotica provided successful phytoremediation process of a contaminated desert soil.