Formation of mineral-mineral and organo-mineral composite building units from microaggregate-forming materials including microbially produced extracellular polymeric substances
Formation of mineral-mineral and organo-mineral composite building units from microaggregate-forming materials including microbially produced extracellular polymeric substances
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DOI：
10.1111/ejss.12774
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发表时间：
2019-05-01
影响因子：
4.2
通讯作者：
Totsche, Kai Uwe
中科院分区：
文献类型：
--
作者：
Guhra, Tom;Ritschel, Thomas;Totsche, Kai Uwe
土壤中胶体化合物的结构，包括有机-矿物和矿物-矿物组合，被认为是复合建筑单元（CBU），可以联合收割机组合成土壤微团聚体。尽管CBU的普遍存在，主要的形成机制是相当模糊的，很少有人知道他们是否形成主要是在风化的母岩或聚集过程中从土壤悬浮液。我们研究了CBU的形成从悬浮液组成的矿物和有机物典型的温带土壤（即石英，针铁矿，伊利石和胞外聚合物[EPS]）。没有EPS，我们发现CBU形成的矿物-矿物协会的伊利石和石英，是由针铁矿桥接的异凝聚。相反，EPS的存在下，导致形成一个稳定的悬浮液粘土大小的CBU没有涉及石英。我们解释了这一点的快速形成的有机-无机CBU的EPS相关的针铁矿和EPS相关的伊利石。EPS在针铁矿表面的吸附屏蔽了针铁矿的表面电荷，从而降低了针铁矿与伊利石之间的静电引力。这种相互作用有效地阻碍了矿物-矿物CBU的形成。此外，EPS与针铁矿的相互作用导致悬浮液中的磷/碳比显着降低。这表明一个优选的吸附含磷的EPS成分针铁矿和反过来的EPS成分之间的固体和液体相的组成分馏所示的傅里叶变换红外光谱与衰减全反射（FTIR-ATR）。激光衍射测量显示，从细粉砂部分的细沙，也支持EPS作为一个“粘合剂”的作用的转变。亮点复合建筑单元（CBU）在悬浮液中形成，含有不同的矿物和有机成分。形成了杂矿物-矿物和有机-矿物两种CBU。悬浮液的初始组成控制所得CBU的类型和性质。根据矿物表面的不同，EPS可用作分离剂或粘合剂。
Structures of colloidal compounds in soil, including organo-mineral and mineral-mineral associations, are considered as composite building units (CBUs) that may combine into soil microaggregates. Despite the ubiquitous occurrence of CBUs, the major formation mechanisms are rather obscure and little is known about whether they form primarily during weathering of the parent rocks or by aggregation processes from the soil suspension. We studied the formation of CBUs from suspensions composed of minerals and organic matter typical for temperate soils (i.e. quartz, goethite, illite and extracellular polymeric substances [EPS]). Without EPS, we found CBUs formed as mineral-mineral associations by hetero coagulation of illite and quartz that is bridged by goethite. The presence of EPS, in contrast, led to the formation of a stable suspension of clay-sized CBUs with no involvement of quartz. We explained this by the rapid formation of organo-mineral CBUs made of EPS-associated goethite and EPS-associated illite. The sorption of EPS to goethite screened its surface charge, thereby reducing the electrostatic attraction between goethite and illite. This interaction effectively impeded the formation of mineral-mineral CBUs. Moreover, interactions of EPS with goethite resulted in a marked decrease of the phosphorus/carbon ratio in the suspension. This suggested a preferred adsorption of phosphorus-containing EPS constituents to goethite and in turn to a compositional fractionation of EPS constituents between the solid and liquid phase as shown by Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR). Laser light diffraction measurements revealed a shift from the fine silt fraction to that of the fine sand that also supports the role of EPS as a 'binding' agent. HighlightsComposite building units (CBUs) form in suspensions with different mineral and organic components. Both, hetero mineral-mineral and organo-mineral CBUs were formed. The initial composition of the suspension controls type and properties of resulting CBUs. Depending on the mineral surfaces, EPS may serve as a separation or binding agent.