73 Soil Texture Effects on Rhizodegradation of Crude Oil Contaminated Soil FARHANA MAQBOOL 1,2 , YING XU 3 , DONGMEI GAO 1 , ZULFIQAR AHMAD BHATTI 4 and ZHENYU WANG 1, * 1 College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China 2 Department of Microbiology, Hazara University Garden Campus, Mansehra, 21300, KPK, Pakistan 3 College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, 266109, China 4 Department of Environmental Science, COMSATS Institute of Information Technology, Abbottabad, 22010, KPK, Pakistan ABSTRACT: The effect of soil texture on the rhizodegradation of crude oil by the Ses- bania cannabina plant was evaluated. Soil texture amendment was difficult to carry out in the field of polluted soil so the soil was used in its original clay-like texture and bioaug- mented with a microbial consortium. After 120 days of plant growth, crude concentration decreased non-significantly from 3,000 ppm to 2,200 ppm. Root morphological charac- teristics and microbial biomass was checked and did not show a pronounced difference. It was concluded that the Sesbania cannabina has a fibrous root structure not strong enough to support constricting and stretching forces of clayey textured soil. Therefore, texture amendment is indispensible for optimizing rhizodegradation of crude oil in soil. INTRODUCTION S OILS contamination from organic pollutants’ ac- cumulation is a widespread issue. Contaminated soils are found on all continents. Accidental spills oc- cur mainly in areas near oil refineries, storage areas, and significant manufacturing activities. Specific tech- niques aimed at remediating these areas consume con- siderable industry and government resources [1]. A combination of two approaches using rhizoreme- diation and bioaugmentation both resulted in rhizodeg- radation. During rhizodegradation, exudates derived from the plant may help to stimulate survival and ac- tion of bacteria. The root system of a plant helps to spread bacteria through the soil and helps penetration into impermeable soil layers [2]. Soil texture, compact- ness, and drainage are the main soil characteristics re- lated to plant growth. Compact soil layers limit root growth and effect properties related to water and air movement. According to Gerhardt [3] in spiked soils, chemicals tend to be bioavailable. Whereas, contami- nants in naturally weathered soils are often not readily bioavailable due to hard soil structure. Hydrophobic characteristics of crude oil retard mass transfer of air, water, and contaminants from particles to microorgan- isms in soil, which limits rate of uptake and metabo- lism of contaminants by hydrocarbon-degrading of the bacteria [4, 5]. Moisture content and aeration were de- termined to be key factors associated with polyaromat- ic hydrocarbons (PAH) bioremediation [6] and these factors are related to soil texture. The specificity of the plant–bacteria interaction is dependent upon soil con- ditions that may alter contaminant bioavailability, root exudates composition, and nutrient levels [7]. Many studies have been carried out to check effects of nutrient addition and bioaugmentation on biodeg- radation of petroleum polluted soil [8, 9, 10] but very few literatures demonstrated the effect of soil physi- cal texture in rhizodegradation experiments. Crude oil contamination is a very much serious problem in the Yellow River Delta in Dongying, Shandong due to its exploitation, manufacturing, and transportation. The size of a contaminated site is very long so the need for a cost effective technique able to remediate such large area is necessary. In the present study soil was bioaug- mented without any other structural amendments to make the technique applicable for the large field area. MATERIALS AND METHODS Physicochemical Analysis of Soil Soil texture was analyzed using the modified meth- *Author to whom correspondence should be addressed. E-mail: fairy_es@yahoo.com Journal of Residuals Science & Technology, Vol. 9, No. 2—April 2012 1544-8053/12/02 073-07 © 2012 DEStech Publications, Inc.