Process fundamentals and field demonstration of wheat straw enhanced salt leaching of petroleum contaminated farmland

A new remediation method for petroleum-salt contaminated soil was proposed, in which wheat straw was applied to enhance salt leaching and meanwhile block salt upmovement along the soil capillary. It was shown that the existence of petroleum increased the surface hydrophobicity of soil and thus hindered the leaching process once the oil content was above 1.5% (mass fraction). The application of 5% (mass fraction) wheat straw into the soil increased the efficiency of salt leaching from 3% to 25%. The effectiveness of wheat straw layer in inhibiting the salt upmovement along the soil capillary was also proven. Field test of this method was carried out in an area of 6400 m², in which wheat straw layer of 5 cm was distributed in the depth of 25 cm. After 50 days, 80% of the testing area showed a normal soil electronic conductivity (soil EC < 5 mS·cm^-1) in contrast to 17% before leaching process. The concentrations of Na⁺ and Cl^- were decreased from 1642.5mg·kg ^-1 and 1301.2 mg·kg^-1 to 499.3 mg·kg^-1 and 433.8 mg·kg^-1, respectively. The remediated land upon the implementation of wheat straw gave a 72 % of the regular wheat production obtained from the normal farmland, while the control land without wheat straw gave 12%. These results demonstrated the effectiveness and the high potential of using wheat straw for the salt leaching in remediation of petroleum-salt contaminated soil.