Effects Of Arbuscular Mycorrhizal Fungi On Plant Uptake And Degradation Of PAHs In Soils

At present, the soil organic contamination has become more general in China and overseas. Polycyclic aromatic hydrocarbons (PAHs) are belong to the persistent organic pollutants, which can be a serious threat to the quality of agricultural products, human health and ecological safety. Having advantages of economy, safety, efficiency and does not produce secondary pollution, the arbuscular mycorrhizal bioremediation (AMBR) has aroused the public concerns. In recent years, many researchers have used arbuscular mycorrhizal fungi (AMF) to remediate PAHs-contaminated soil and have achieved remarkable results. But the main ways by which AMF influence the degradation of PAHs in soil and plant uptake and are still unclear, while these need to be further studied.This work aimed to discussion on the contribution of AMF hyphae and glomalin to the remediation of PAHs in contaminated soil. AMBR for soil contaminated by phenanthrene and pyrene was investigated in a pot experiment. During the experimental period, the changes of the biological characters of AMF under PAHs stress were systematically detected, and the effects of inoculated plants uptake of PAHs on the degradation of PAHs in soil were evaluated.(1) The changes of the biological characters of AMF under PAHs stress were evaluated. When the concentrations of phenanthrene and pyrene in soil were 41.87 and 42.80 mg·kg-1, the mycorrhizal colonization rate, arbuscule rate, mycorrhizal root length, vesicule and spore numbers of AMFs enlarged with cultivation time in 35～65 d after inoculation; However, the previous three parameters of AMFs decreased in 65～75 d. The contamination of phenanthrene and pyrene clearly influenced the biological characteristics of AMFs. The mycorrhizal colonization rate, arbuscule rate, and mycorrhizal root length of test AMFs after 65 d decreased with the increase of the PAHs concentrations in soils. The spore production of AMFs reduced when PAHs presented at the higher contamination levels, while lower concentrations of PAHs promoted the spore production. The vesicule amounts of AMFs changed little under the stress of PAHs contamination at test levels.(2) The effect of inoculated plant uptake of PAHs on the degradation of PAHs in soils was studied. AMF-inoculated plant could increase the accumulation amount of phenanthrene and promote the contribution rate of plant uptake on the degradation of PAHs in soils. After 80 d inoculation, compared to the plant treatment, the amount of phenanthrene accumulation in plants inoculated Ge or Gm increased by 149.04% and 118.33% respectively. Meanwhile, the contribution rate increased 138.46% and 111.54% respectively. But the plant accumulation of PAHs is not the main way of the remediation for polluted soil, the contribution ratio of plant accumulation on the degradation of phenanthrene in soils is far less than 1%.(3) The contribution of AMF hyphae and glomalin on the remediation of PAHs in contaminated soil is discussed. During 35-75 d, the inoculation of AMF could increase the amount of hyphal density、easily extractable glomalin and total glomalin. Correspondingly, the phenanthrene and pyrene removal rates in AMF-inoculated treatment were significantly higher than those for plant treatments. During 45～75 d inoculation, the generated amount of hyphal density and total glomalin in Gm treatment have increased by 21.90%,14.98% and by 14.07%,4.37% compared to the treatments of Ge and Gla. Correspondingly, the remediation efficiencies for phenanthrene, pyrene in soils in Gm treatment groups have increased by 1.45%,5.88% and by 1.03%,7.37% compared to the treatments of Ge and Gla.