Bioremediation of PAHs contaminated soil and its impacts on soil enzyme activity

Polycyclic aromatic hydrocarbons(PAHs) are an important group of organic micropollutants(xenobiotics) which are widely distributed in the environment.This study aimed to compare the PAHs degradation effects by bioremediation using immobilized microbes,phytoremediation using ryegrass(Lolium perenne L.) and alfalfa(Medicago sativ L.),and combination of the above two approaches on the PAHs contaminated soil.Attention was paid on variation of the soil enzyme activity,as well as correlation between the PAHs removal rate and the enzyme activity during the bioremediation process.The experimental results showed that although phytoremediation,microbial remediation and integrated plant-microorganism bioremediation would all degrade PAHs effectively,the PAHs removal by ryegrass-(immobilized) microbe and alfalfa-(immobilized) microbe would reach up to 37.57% and 38.41%,respectively,which were 100% higher than either phytoremediation or microbial remediation method.It was found that bioremediation/phytoremediation of PAHs contaminated soil would increase the soil enzyme activity of dehydrogenase,polyphenol oxidase,urease,and decrease the enzyme activity of catalase.In particular,rhizosphere soil dehydrogenase and polyphenol oxidase activities were significantly correlated to concentration of PAHs.They might thus be taken as degradation indicators of soil PAHs during bioremediation process.