真菌-玄武岩相互作用过程中真菌属种差异对元素释放行为的影响

真菌在矿物、岩石风化和元素溶解过程中发挥着重要作用。土壤中分布和生长着多种真菌,这些不同真菌在矿物和岩石风化,以及元素溶解过程中发挥的作用可能存在显著差异。为限定此差异,本研究从玄武岩风化土壤中分离获取了4种真菌(Aspergillus pesudofelis、Aspergillus viridinutans、Aspergillus undagawae和Aspergillus clavatus),设计批式溶解实验,探究了实验室条件下(28℃、30天内)4种真菌对玄武岩的风化作用,主要通过分析元素(包括Mg、Al、Si、Ca、Ti、Mn、Fe、Ni和Sr)的溶解速率和机制揭示不同属种真菌造成的玄武岩风化差异,并选取其中两种典型真菌所在的体系进行分析。实验结果显示不同属种真菌对玄武岩的风化和元素溶解的作用确实存在显著差异:1)与无机对照组相比,真菌A.pseudofelis的生长使得溶液pH值发生显著变化,元素的线性释放速率(Ril)显著升高;2)不同种真菌对体系pH值和Ril的影响差别巨大,且并非所有真菌均能加快玄武岩风化,如经过30天反应,含真菌A.pseudofelis体系溶液pH值上升了2.1,元素Mg的线性释放速率是无机对照组的22.5倍;而含真菌A.viridinutans体系溶液pH值仅上升了0.1,Mg的线性释放速率与无机对照组近似相等;3)Mg、Al、Ca、Ti元素的线性释放速率Ril最大值均出现在溶液最低pH值条件下,表明这4种元素的释放行为很大程度上受控于质子交换作用,而Fe和Ni的释放则由真菌代谢的草酸主导。由此可知,不同种真菌对有机酸代谢水平的差异影响了玄武岩中元素的释放行为。这也可能表明,在岩石早期风化过程中,具有较强有机酸(如草酸)代谢能力的真菌在Fe和Mg等生命必需元素的释放过程中起着重要作用。

The effect of species difference of fungi on elemental release behavior during fungal-basalt interactions

Fungi play an important role in minerals and rocks weathering and elements release.A variety of fungi are distributed and grown in the soil.However,different fungi species may have different function in the minerals and rocks weathering,as well as elements release process.In order to limit this difference,four fungi(Aspergillus pesudofelis,Aspergillus viridinutans,Aspergillus undagawae and Aspergillus clavatus)were isolated from the basaltic weathered soil,and batch dissolution experiments were designed.The weathering effects of four fungi on basalt under laboratory conditions(28℃,30 d)were investigated.The dissolution rates and mechanisms of the analytical elements(including Mg,Al,Si,Ca,Ti,Mn,Fe,Ni,and Sr)revealed the differences in basalt weathering caused by the interactions with different species of fungi.The results showed that there were significant differences in the effects of different species on the weathering and elemental dissolution of basalt.Specifically,compared with the inorganic control groups,the growth of A.pseudofelis caused an obvious change in the solution pH,and increased the elemental linear release rate(Ril)significantly.The effects of different fungi species on solution pH and Ril varied greatly,and not all fungi could accelerated basal weathering.For example,after 30 days of reaction,the solution pH of the system with the fungus A.pseudofelis increased by 2.1,and the linear release rate of Mg was 22.5 times that of the inorganic control group.While the solution pH of the system with the fungus A.viridinutans was only increased by 0.1,and the linear release rate of Mg was approximately equal to that of the inorganic control group.The Ril for Mg,Al,Ca and Ti in the solution interacted with A.pseudofelis had the maximum values when the solution pH was the lowest,which indicated that the release behavior of these four elements were controlled by the proton exchange process,whereas the release of Ni and Fe was dominated by fungal metabolized oxalic acid.Our study showed that different fungi species had various capacity to metabolize organic acids and thus affected the release behavior of the elements in basalt.This suggests that those fungi with stronger capacity of metabolizing organic acids(such as oxalic acid)might play a significant role in enhancing the release rate of essential elements to life,such as Fe and Mg during the early stage of rock weathering.