Department of Environmental Geosciences, Centre for Microbiology and Environmental Systems Science, University of Vienna, Josef-Holaubek-Platz 2, UZA II, 1090 Vienna, Austria.
Water Res. 2022 Jul 15;220:118655. doi: 10.1016/j.watres.2022.118655. Epub 2022 May 24.
Freshwater suspended particulate matter (SPM) plays an important role in many biogeochemical cycles and serves multiple ecosystem functions. Most SPM is present as complex floc-like aggregate structures composed of various minerals and organic matter from the molecular to the organism level. Flocs provide habitat for microbes and feed for larger organisms. They constitute microbial bioreactors, with prominent roles in carbon and inorganic nutrient cycles, and transport nutrients as well as pollutants, affecting sediments, inundation zones, and the ocean. Composition, structure, size, and concentration of SPM flocs are subject to high spatiotemporal variability. Floc formation processes and compositional or morphological dynamics can be established around three functional components: phyllosilicates, iron oxides/(oxy)hydroxides (FeOx), and microbial extracellular polymeric substances (EPS). These components and their interactions increase heterogeneity in surface properties, enhancing flocculation. Phyllosilicates exhibit intrinsic heterogeneities in surface charge and hydrophobicity. They are preferential substrates for precipitation or attachment of reactive FeOx. FeOx form patchy coatings on minerals, especially on phyllosilicates, which increase surface charge heterogeneities. Both, phyllosilicates and FeOx strongly adsorb natural organic matter (NOM), preferentially certain EPS. EPS comprise various substances with heterogeneous properties that make them a sticky mixture, enhancing flocculation. Microbial metabolism, and thus EPS release, is supported by the high adsorption capacity and favorable nutrient composition of phyllosilicates, and FeOx supply essential Fe.
淡水悬浮颗粒物（SPM）在许多生物地球化学循环中起着重要作用，并具有多种生态系统功能。大多数 SPM 以复杂的絮状聚合体结构存在，由从分子到生物体水平的各种矿物质和有机物组成。絮体为微生物提供栖息地，为较大的生物体提供食物。它们构成微生物生物反应器，在碳和无机养分循环中发挥突出作用，并作为营养物质以及污染物的载体，影响沉积物、淹没区和海洋。SPM 絮体的组成、结构、大小和浓度受到高度时空变异性的影响。絮体形成过程和组成或形态动力学可以围绕三个功能组件建立：层状硅酸盐、铁氧化物/（氢）氧化物（FeOx）和微生物细胞外聚合物物质（EPS）。这些成分及其相互作用增加了表面性质的异质性，增强了絮体的形成。层状硅酸盐在表面电荷和疏水性方面表现出固有异质性。它们是反应性 FeOx 沉淀或附着的优先底物。FeOx 在矿物上形成斑片状涂层，特别是在层状硅酸盐上，这增加了表面电荷的异质性。层状硅酸盐和 FeOx 都强烈吸附天然有机物（NOM），优先吸附某些 EPS。EPS 由具有不同性质的各种物质组成，使其成为粘性混合物，增强了絮体的形成。微生物代谢，从而 EPS 释放，得到了层状硅酸盐和 FeOx 的高吸附能力和有利的养分组成的支持，它们提供了必需的 Fe。
