| With the rapid development of the petroleum and chemical industry, contamination oforganic pollutant especially polycyclic aromatic hydrocarbons in soil has become a seriousproblem of our environment. Phytoremediation is one of the most promising methods to dealwith this problem and has turned attention towards new research into developing it,because itis an efficient, economical and environment-friendly way and don’t cause secondary pollution.Pot experiments were conducted to evaluate the phytoremediation effects of mung bean,peanut, alfalfa and ryegrass. The removal effect of pyrene from soil by mung bean, mungbean-rhizobium association and raw mung bean return was further explored. This work aimedto obtain the best recovery system, and provide a theoretical basis for the in situ remediation.The results of the screening experiment showed that removal capacity of pyrene wasimproved in the presence of roots of four species than in unplanted soil. Compare withplant-free system, the removal capacities of pyrene by mung bean system with or withoutrhizobium increased by21.63%and23.65%, respectively. And the capacity by peanut with orwithout rhizobium system were35.1~63.9%and11.5~24.6%, respectively. Due to thetemperature, alfalfa and ryegrass couldn’t grow very well, and can not form symbiosis withrhizobium,so the removal capacity increased by only8%and10%respectively. But mungbean can thrive in this condition and form a symbiosis with rhizobium well and it also couldalleviate soil acidification and keep the acidity of soil stayable, while the other three speciescouldn’t. Dehydrogenase activity in contaminated soil followed an order as mung bean>peanut> alfalfa> ryegrass, which indicated that mung bean was the most effective plant toalleviate the toxicity of pyrene in soil. The data suggested that mung bean could be useful forphytoremediation of soils contaminated with PAHs, as it was adaptable with developed rootsystem.The pot experiments were conducted during60days, and the results showed that theremoval capacities of pyrene(the range of concentration is10-100ppm) by mung bean with orwithout rhizobium were76.8~89.2%and85.6~90.4%respectively, compared to them those inunsterile and sterile soil without mung bean were35.1~63.9%and11.5~24.6%, respectively.The number of pyrene-degrading microbes positively associated with the concentration ofpyrene, but it showed no correlation with mung bean. These results indicated that the removalof pyrene seems to be promoted by mung bean by providing the substrate for symbioticorganisms. Furthermore, during the simulation experiment of raw mung bean return, theremoval capacity of pyrene increased by13.84%compared to control in25days. This paper found that the association mung bean-rhizobium could effectively removepyrene in soil, and the application of raw mung bean return can also be an efficient way toremove pyrene. |
