ASSESSMENT OF PLANT RESIDUES (DICHONDRA REPENS) AND NUTRIENTS AMENDMENTS FOR THE REMEDIATION OF COPPER-PHENANTHRENE CO-CONTAMINATED SOIL

The clean-up of soils co-contaminated with heavy metals and organic compounds is a contemporary issue of remediation efforts. In this study, the purpose is to investigate the effect of plant residues and nutrients on soil enzymatic activity, number of hydrocarbon degrading bacteria and microbial community through pyrosequencing of 16S rRNA gene amplicons, to enhance the simultaneous removal of phenanthrene and copper from the co-contaminated soil. The experiment was divided into five groups (S0-S4) by adding various nutrients and 0, 1, 3, 5, 7% of plant residue (dichondra repens) for the survival of microorganisms. The results showed that the degradation rate of phenanthrene in the simulated soil reached 32.69%, 65.25%, 78.89%, 81.59%, 92.84% and the conversion rate of soluble copper reached 13.31%, 44.72%, 50.33%, 55.95%, 60.11% in S0 to S4, respectively. The enzyme activities of dehydrogenase and urease were transiently promoted by the presence of additive after 15 days, subsequently the number of hydrocarbon -degrading bacteria also increased, but the shift became weaker or disappeared as the exposure time increased to 61 days. Then we selected S4 which has the best degradation effect for sequencing analysis and it produced a change of species richness, the original bacterial flora of that was Actinobacteria (40.4%), then it gradually left a community dominated by members of Proteobacteria (50.4%) and Bacteroidetes (45.5%), with Arachidicoccus and Sphingobium as the most abundant genus. The results indicated that more plant residues and nutrients has potential for clean-up of heavy metals and polycyclic aromatic hydrocarbons (PAHs) from co-contaminated soils.