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Soil microorganisms would reproduce rapidly and migrate directionally under the applied electric field. In this study, tetradecane-degrading bacteria were added at different locations in soil, and 1 V·cm -1 unidirectional DC electric field was applied to investigate the migration, distribution, and degradation characteristics of target bacteria in soil. The results showed that microorga-nisms migrated to the cathode and anode by electrodialysis and electrophoresis, respectively. The number of microorganisms migrated by electrodialysis was 3.5 times of that by electrophoresis. The application of electric field could make the soil environment spatially heterogeneous to affect the growth of microorganisms. The average number of soil microorganisms under electric field was 1.16×10 8 CFU·g -1 (6 days), which was 2.3 times of that without electric field. S 2 to S 4 were the efficient growth areas of microorganisms, with the average number after 30-day electric treatment being 2.8-3.5 times of that on the anode and cathode, and 2.1 times of that in the control. There was a significant positive correlation between the tetradecane degradation rate and the number of microorganisms (r=0.895, P＜0.05). The optimal tetradecane degradation region was near the cathode (S 4 ), where its degradation rate reached 94.6%. Based on these results, a model modified by environmental factors was established to simulate the spatial distribution of microorganisms under the combined effect of electrokinetic stimulation and transportation. According to the model, the number distribution of microorganisms could be deduced when exogenous bacteria were added in a fixed section. The results provide a theoretical basis for the efficient import of exogenous functional bacteria in electrokinetic-bioremediation of organic contaminated soil.

Biomarkers are applied worldwide in marine environmental assessment due to their "early warning" function to chemical pollutants. Several integrative index approaches such as multi-marker pollution index (MPI), integrated biomarker response (IBR), bioeffect assessment index (BAI), biomarker response index (BRI), and health assessment index (HIS), have been developed based on biomarkers. By transforming the complex alterations of biomarkers into a single class or value, these approaches have been so far the useful tools for assessing the environmental quality. This review summarized the establishment of evaluation indicator system, the calculation of integrative index, the grading of pollution status, and the practical applications of each approach, and discussed the existing problems in marine environmental assessment based on biomarker index. Some improving suggestions were also proposed.