PAHs biodegradation in soil by inoculation of isolated microorganisms.

The rate and extent of polycyclic aromatic hydrocarbons(PAHs)biodegradation in soil are affected by various factors,mainly including contact toxicity,soil-PAHs contact time,microbial population and environmental parameters.In this paper,the biodegradation efficiency of PAHs mixtures(consisting of phenanthrene,pyrene,benz(a)anthracene,benzo(b)fluoranthene,benzo(k)fluoranthene and indeno(1,2,3-cd)pyrene)with the inoculation of mixed microbial consortia was studied.The mixed microbial consortia were isolated from PAHs contaminated soil,mainly including Sphingomonas,Methylobacterium,Burkholderia,Rhodobacterium,Bradyrhizobium,Phyllobacterium,Chryseobacterium and Microbacterium.The results indicated that the isolated mixed microbial consortia were capable of mineralizing PAHs,and the half life of phenanthrene,pyrene,benz(a)anthracene,benzo(b)fluoranthene,benzo(k)fluoranthene and indeno(1,2,3-cd)pyrene in soil was 6.12,8.25,8.74,19.31,20.06 and 22.28 days,respectively.The initial biodegradation rates of these PAHs were faster at the beginning states,then became slower after the incubation of 17 days.The average biodegradation efficiency of phenanthrene,pyrene,benz(a)anthracene,benzo(b)fluoranthene,benzo(k)fluoranthene and indeno(1,2,3-cd)pyrene after 27 days was 98.14%,89.97%,88.47%,63.55%,65.24% and 60.49%,respectively.More than 93% of phenanthrene was degraded within the incubation of 5 days.The initial biodegradation rate of pyrene,benz(a)anthracene,benzo(b)fluoranthene,benzo(k)fluoranthene and indeno(1,2,3-cd)pyrene in soil contaminated for 210 days was 0.847 5,0.898 5,0.302 8,0.197 6 and 0.137 8 mg·kg-1·d-1,respectively.However,the initial biodegradation rate of these PAHs in soil contaminated for 50 days was 0.451 6,0.662 8,0.196 4,0.165 3 and 0.093 6 mg·kg-1·d-1,respectively.The lag phase of degradation was shorter with increasing soil-PAHs contact time.