Enhanced bioaugmentation of petroleum- and salt-contaminated soil using wheat straw

A new bioaugmentation method for petroleum- and salt-contaminated soil was presented, in which wheat straw was used to enhance salt leaching and subsequent petroleum degradation by a bacteria-fungi consortium of Enterobacter cloacae and Cunninghamella echinulata. The effectiveness of a coarse wheat straw layer in inhibiting capillary-induced upward salt movement and in enhancing growth of E. cloacae and C. echinulata was shown in the laboratory and a 7000-m² field study in Henan Province, China. In the field study, the Na⁺ concentration in remediated soil at 1-25 cm depth decreased from 1597 ± 394 to 543 ± 217 mg kg^-1, while Cl^- decreased from 1520 ± 922 to 421 ± 253 mg kg^-1. The wheat straw increased bacterial biomass by 170-fold and fungi 11-fold compared to control soil without wheat straw. The concentration of total petroleum hydrocarbons decreased from 6320 ± 1180 to 2260 ± 420 mg kg^-1 after 45 d of treatment. Wheat was cultivated on remediated soil and grain yield reached 72% of that obtained in normal farmland adjacent to the study site. The results demonstrated the effectiveness of wheat straw in enhancing bioaugmentation of the petroleum- and salt-contaminated soil and indicated a high application potential.