| Soil is a primary natural resource for human beings. Nowdays, the soil contamination is worldwide problems. Organic pollutants can find their ways into the soil environment. How to remediate the contaminated soils is of worldwide concerns. The arbuscular mycorrhizal bioremediation (AMBR) is being recognized as an important, economyic, safe, and available technique for organic contaminated sites. However, as to persitent organic pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs), the process and mechanisms of AMBR are still under well elucidation.In this work, the AMBR for contaminated soils by PAHs, phenanthrene, pyrene, and acenaphthene as representatives was investigated. The effect of arbuscular mycorrhiza (AM) on the growth of plant and microbes in soil was studied. The residues of PAHs in soil in the presence of AM were fractionated. The approach the mechanisms of AMBR for PAH-contaminated soils were discussed. Main results of this work are as follows:(1) The influence of AM on the growth of plant and microbe was studied. Plant biomass with AMF inoculation was larger than those controls without AMF. Contrast with no-AMF controls, The amounts of fungus and actinomycete in soils with AM were 72%～329% and 92% higher than those in control soil treatments without AM, respectively. In addition, AMF1(Glomus mosseae), AMF2(Glomus etunicatum) and AMF3(Glomus versiforme) were observed to be most effective in stimulation of the growth of plants and microorganisms. The amounts of bacteria, fungus and actinomycete in soils with AMF1 were 48%, 271%, and 46%, larger than those with no fungus inoculation controls. Similarly, the amounts of bacteria, fungus and actinomycete in soils with AMF2 increased the AMF2 were increased by 10%,329% and 92% than no fungus control, and the amounts of fungus and actinomycete with AMF3 increased 230% and 67%, respectively. (2) AMBR for PAH-contaminated soils was systematically investigated. The initial concentrations of phenanthrene and pyrene were 0～170.6 and 0～74.0 mg·kg-1 . In 20～70 days, about 91% and 54%～89% of added respective phenanthrene and pyrene were disappeared from soils with five AM fungus. Contrast with no AMF controls, the residual concentrations of phenanthrene and pyrene in soil degraded obviously, and more significant degradation was observed in soils with AMF1, AMF3 and AMF4 (Glomus constrictum). The presence of co-pollutant (pyrene) inhibited the degradation of phenanthrene in soils. About 98% and 89% of added respective phenanthrene and pyrene were disappeared from soils with multiple-AMF fungus, indicating that the AMBR for PAH-contaminated soils were more effective with multiple AMF fungus.(3) The residues of PAHs in soil in the presence of AM were fractionated into different forms. The effects of AM on the distribution and transformation of PAHs in soils is evident. Acenaphthene was degraded obviously in soil environment. In soil 1 and soil 2, AM benefited the transformation of acenaphthene into bound residue. The concentrations of the extractable fractions of acenaphthene in soils with inoculation of AMF1 and AMF2 were 11～16% and 18～15% lower than non-AMF controls. The concentrations of bound acenaphthene residue in soils with AMF2 were 90% and 44% higher than controls. Moreover, the concentrations of bound residual PAHs were observed to be positively correlated to soil organic matters.(4) The mechanisms of AMBR for PAH-contaminated soils were elucidated. The remediation mechanisms for PAH contaminated soils by AMBR technique mainly included plant accumulation and transformation, degradation by soil microorganisms, degradation by AM fungus themselves, and transform into bound PAH residue. It was observed that alfalfa off-take only accounted for less than 1.15% and 5.21% of the dissipation enhancement for phenanthrene and pyrene in soils with present AMFs. The inoculation of AMFs in soils significantly enhanced microbial activity, and thus promoted the biodegradation of PAHs in soils, which was the predominant mechanism of AMBR for PAH-contaminated soil. |
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