Organic contaminated soils have become a widespread environmental problem, which may lead to a geart threat to quality of agriculture production and human health. Physical, chemical, and biological technologies have been employed for the mitigation and remediation of organic contaminated soils/sites. Mitigation is suggested for slightly-contaminated agricultural soils, and remediation is recommended for heavily-contaminated soils/sites. Consequently, the mitigation and remediation techniques for organic contaminated soils have been developed by regulating the interfacial behavior and bioavailability of organic pollutants.<br/>For assuring the safety of agriculture production in slightly-contaminated soils, transfer and accumulation of organic pollutants need to be mitigated, where the bioavailability of organic pollutants plays a critical role. A speciation scheme for the fractionation of organic pollutants in soils has been designed to conveniently quantify the bioavailable concentrations. In practice, a sequential ultrasonic extraction method is suggested to differentiate organic pollutants into four fractions, including water soluble-, organic acid-soluble-, organically bound-, and residual fractions. The combination of water soluble- and organic acid-soluble fractions corresponds to the bioavailable portions. Furthermore, a new mitigation technique has been developed by utilizing the surfactants or biochar to enhance sorption and fixation ability for organic pollutants to soils. An experiment shows that with this new technique the concentration of polycyclic aromatic hydrocarbons (PAHs) accumulated in plants decreased by two thirds.<br/>For heavily-contaminated soils/sites, surfactant-enhanced bioremediation (SEBR) have been developed. When surfactants are applied to the soils, organic pollutants sorbed on the soils are washed off to the soil solutions, with increased bioavailability. To reveal the remediation mechanism, a pathway linking the gene expression with the physiological phenomena is delineated. Surfactants elevate the expression levels of Δ9 fatty acid desaturase, RHDase and 1H2Nase, then to promote the partition and transmembrane transport and to accelerate the intracellular biodegradation of organic pollutants. To date the SEBR technique has been applied in several remediation projects. The removal rates of PAHs in soils by rhamnolipid-enhanced phytomicrobial remediation increased from ~45% to &gt;70%.

Mitigation and remediation of organic contaminated soils

252nd National Meeting (2016)

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