| 其他摘要 | Fungi play a role which can not be ignored in the process of rocks and minerals weathering, and rock-inhabiting fungi have been increasingly received concern in the microbial weathering study. In this study, A strain of fungi isolated from the surface of carbonate rocks was chosen to carry on the study of the microbial weathering of carbonate rocks experimentally, we have studied the weathering effect and process of different carbonate rock by the fungi, and analyzed the metabolites of the fungi, the calcite saturation index of the culture and the behavior of rare earth elements during weathering process, and discussed the weathering mechanism of the fungi.
According to the morphological characteristics and molecular identification results which based sequence ITS, the strain GZKM01 was identified as Aschersonia, belonging to Kingdom fungi, Deuteromycotina, Coelomycetes, Sphaeropsidales, Nectrioidaceae.
The results showed that the fungi can weather the carbonate rocks effectively under the experimental conditions, it can greatly enhance the dissolution of Ca2+, and the Ca2+concentration of supernatant of fermentation broth is much higher than the medium control and deionized water control groups; take the cultures with limestone powder for example, the Ca2+ concentrations of supernatant of the weathering medium is 3.98 and 13.73 times respectively compared with dead fungi control and deionized water control groups.
It can produce metabolites such as organic acids and alcohol with the growth of fungi; it can form the mycelium-mineral complex or aggregate between the fungi and the mineral powders in the process of weathering, and the fungi extracellular secretion formed a biofilm on the surface of mineral poeders; the saturation index of calcite (SIc) increasing all the time because of microbial weathering of carbonate rocks, and the solutions are supersaturation for calcite. Fungi can weathering carbonate rocks by chemical degradation of organic acids and other small molecules, mechanical damage the catalysis of carbonic-anhydrase, the absorption of mineral elements by the cell and secondary mineralization.
The concentrations of REE in the fermentation broth are higher than the solution leached by K2HPO4. Compared with that haehed with K2HPO4，the fractionation of the REE leached with fungi is characterized by higher δCe, lower δEu, rich in Ce and lack in Eu, this characteristic is more obviously in the fungal cells,and the fungal cells can enrichment Ce strongly. The combination of metabolites, regulating of pH by fungal metabolites, cell direct absorption and adsorption, adsorption of organic matter, and oxidation-reduction is the main reason which caused the dissolution, migration and enrichment of rare earth elements.
It is concluded that the microbial weathering of carbonate rocks includes a series of complex biochemical and biophysical processes, these two processes are interdependent, mutual promotion and cooperated with each other, fungi play an important role in the weathering of carbonate rocks. Fungi play an important role in the dissolution, migration and enrichment of the REE in the minerals. It can provide basis for the assess the role of micro-organisms in the weathering of rocks through a comprehensive analysis of weathering intensity of the weathering crust, characteristics of rare earth elements, microbial activity and so on. We have deepened the understanding of the weathering process mechanism of the carbonate rocks by rock-inhabiting fungi, and provide reference for the further study. |
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