Sorption thermodymamics and aggregation as controls of substrate use and mineralization

有机分子对矿物质的吸附强度和保护有机基质的团聚体的稳定性是土壤系统微生物群落“塑造能量和物质使用渠道”的边界条件（SPP 2223的总体假设C）。虽然土壤中有机物对微生物利用和矿化的稳定与吸附有关，但其与吸附过程热力学的关系迄今尚未量化。此外，土壤团聚体和土壤微生物多样性对这一关系的影响尚不清楚。为了分析形成能量和物质使用通道的边界条件，我们将测试以下假设：（H I）吸附和解吸能随山梨酸盐极性和氧化程度的增加以及吸附剂表面羟基数量的增加而增加；（H II）微生物底物的利用随deltaG的减小而减少，热力学吸附滞后和解吸活化能随吸附底物使用的热力学阈值的增加而增加；（H III）微生物利用吸附底物的热力学阈值随着土壤微生物群落功能多样性的增加而增加；（H IV）团聚体中对底物的高度物理保护削弱了吸附热力学对微生物底物利用的重要性。我们将在四个相应的工作包中检验这些假设。在WP1中，我们将通过不同温度、Arrhenius图和微热量下的吸附-脱附实验，确定6种模型底物和3种模型矿物的吸附反应的吉布斯自由能（δ）、吸附焓（δ）和熵（δ）、脱附反应的活化能（Ea）和因吸附滞后而损失的摩尔自由能（Tii）。WP2将使用SPP土壤样品的小型培养实验来确定14C标记的模型基质吸附到混合在4 SPP土壤中的模型矿物上的使用和矿化。功能多样性在矿化中的作用将在WP3中进行第二次培养实验，在SPP土壤中加入提取的微生物，以利用生态板进行酶分析来操纵微生物多样性或营养物质。最后，在WP 4中，将测量在形态和物理上表征的分散和团聚土壤系统中吸附的选定13c标记模型物质的矿化。结合预期结果，我们的项目将为将吸附过程和聚集整合到土壤生态系统功能和发展的热力学概念中提供重要的见解。

Sorption strength of organic molecules to minerals and the stability of aggregates protecting organic substrates are among the boundary conditions that “shape the channel for energy and matter use” by the microbial community of soil systems (overall Hypothesis C of SPP 2223). Although the stabilization of organic matter against microbial use and mineralization in soil has been linked to sorption, its relationship to the thermodynamics of sorption processes has not been quantified so far. Furthermore, the impact of soil aggregation and soil microbial diversity on this relationship is unknown. To analyze the boundary conditions shaping the channel for energy and matter use, we will test the following hypotheses: (H I) sorption and desorption energies increase with increasing polarity and degree of oxidation of the sorbate and increasing number of surface hydroxyl groups of the sorbent, (H II) microbial substrate use decreases with decreasing deltaG, increasing thermodynamic sorption hysteresis and activation energy of desorption with thermodynamic thresholds for the use of sorbed substrates, (H III) thermodynamic thresholds for microbial use of sorbed substrates increases with increasing functional diversity of the soil microbial community and (H IV) high physical protection of substrates within aggregates undermines the importance of sorption thermodynamics for microbial substrate use. We will test these hypotheses in four corresponding workpackages. In WP1 we will be determine Gibbs free energies deltaG of sorption reactions, sorption enthalpies (deltaH) and entropies (deltaS), activation energies Ea of desorption reactions and losses of molar free energy due to sorption hysteresis (Tii) for 6 model substrates and three model minerals via sorption-desorption experiments at different temperatures, Arrhenius plots and microcalorimety. WP2 will use miniaturized incubation experiments with SPP soil samples to determine use and mineralization of 14C labelled model substrates adsorbed to model mineral mixed into 4 SPP soils. The role of functional diversity in mineralization will be studied in WP3 by a second incubation experiment with SPP soils spiked with extracted microbes to manipulate microbial diversity or nutrients based on enzymatic analyses using ecoplates. Finally, in WP 4, the mineralization of selected 13C-labelled model substances adsorbed to dispersed and aggregated soil systems that were characterized morphologically and physically will be measured. Combining the expected results, our project will deliver essential insights for the integration of sorption processes and aggregation into thermodynamic concepts of soil ecosystem functioning and development.