| PAHs are the most common persistent oganic pollutants (POPs) in the coking industrial sites. These pollutants are usually absorbed in soil particles and hard to degradate due to their low water-solubility and high heat-stability. Remediation of PAHs contaminated soils has become an important issue in current times. In this study, based on the distribution characteristics of both PAHs and microorganisms in the soil of a coking industrial site, laboratory experiments and in-situ pilot experiments were carried out to study the degradation efficiency of the PAHs by using PAHs degradation microorganisms from the soil of the coking industrial site in order to provide technical support for the microorganism triggered remediation of PAHs contaminated soils especially for the coking industrial site. The results are as follows:1. Method for PAHs and BTEX determination on the field of the coking industrial site was established. The results showed that method of ultrasonic extraction-GC/MS could be well used for determination of PAHs on field of the coking plant, which was proved to be satisfactory in recovery test, easy for operation and high efficient in extraction of anthracene and Fle in soil. Static headspace-GC was suitable for determination of high concentrated-BTEX contaminated soils, and purge and trap-GC was suitable for the low concentrated-BTEX contaminated soils.2. Distribution characteristics of PAHs and microorganism in the soils of a typical contaminated coking plant was illustrated. The results showed that soils of the coking plant was seriously contaminated by PAHs, with the highest concentration of 666.74 mg/kg, and the contamination depth reached to 12 m below the surface.2-3 ring PAHs was found to be the main PAHs forms in the contaminated soils. The highest concentration was detected in 2-20μm soil particles in various depths of soil. The amounts of 20-200μm soil particle accounted for more than 70% of the soil mass in 0-7.5 m soil, and the soil particles over 200μm accounted for 85.93% of the total soil mass in 10.5～12.0 m soil. The results showed that large amount of local microorganism existed in the contaminated soil. 3. Bacterium reagent for PAHs degradation was developed and the effects on PAHs degradation was investigated. The result showed that the concentrations of PAH decreased to 2215.85μg/kg,2353.83μg/kg,2314.91μg/kg from the original concentration of 5031.75μg/kg by bacterium reagent A, B and C, respectively. Bacterium reagent A was more effective in PAHs degradation under the solution system, especially for Nap, Ane, Fle, Phe and Fla. Efficiency of PAHs degradation was the greatest when the ratio of bacterium and the carrier was 1:1 for Microbacterium under the soil system, and the efficiency was highest when the ratio was 0.5:1 for bacterium reagent B. The efficiencies of bacterium reagent A were stable in both situations, with little variation.4. Effect of microorganisms selected on in-situ PAHs degradation on industry contaminated field was evaluated. The results showed that Bordetella reagent was very efficient in in-situ application. The degradation ratios of TPAH were 95.25% and 63.46% under 0-20 cm and 20-40 cm soil, respectively. The degradation ratios of TPAH by reagent A were 92.60% and 52.52%, respectively... |
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