The mobility of different types of soil organic matter (SOM), including dissolved organic matter (DOM) and mineral associated organic matter (MAOM), along the soil profile in response to infiltration flow can significantly affect the carbon pools in subsoil. In addition, the soil heterogeneity on the pore-scale, comprising pore spaces within the intra-aggregate matrix and preferential pathways within inter-aggregate zones, can also affect the mobility of SOM. This is especially the case for clay-sized MAOM. However, the quantitative understanding of the clay-sized MAOM mobility in presence of pore-scale heterogeneity remains elusive. This study designed a novel microfluidic device to track the pore-scale distribution and mobility of fluorescence labeled clay-sized MAOM in heterogeneous soil pore structures. Results showed that the MAOM mobility was significantly lower in the intra-aggregate zones compared with in the inter-aggregate zones. Only 4.8 % to 47.9 % of MAOM in the intra-aggregate region was mobilized at high leaching flow rates of 81 to 163 mm/d. Moreover, colloid mobilization induced by shearing rather than solute desorption followed by solute dilution is expected to be the major factor facilitating the mobilization of clay-sized MAOM. This study demonstrated a new experimental protocol allowing the in-situ visualization and quantification of OMs mobility in presence of pore-scale heterogeneity. Moreover, our findings also highlighted the potential importance of heterogeneous mobility of clay-sized MAOMs that facilitated by the colloid transport on the SOM turnover and distribution.

中文翻译：

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基于微流体的异质土壤团聚结构中矿物相关有机物的流动性的原位可视化


不同类型的土壤有机质 (SOM)，包括溶解有机质 (DOM) 和矿物伴生有机质 (MAOM)，响应入渗流而沿土壤剖面移动，可显着影响底土中的碳库。此外，孔隙尺度上的土壤异质性（包括骨料内基质内的孔隙空间和骨料间区域内的优先通道）也会影响 SOM 的流动性。对于粘土大小的 MAOM 来说尤其如此。然而，在存在孔隙尺度异质性的情况下，对粘土大小的 MAOM 迁移率的定量理解仍然难以捉摸。本研究设计了一种新型微流体装置，用于跟踪异质土壤孔隙结构中荧光标记的粘土尺寸 MAOM 的孔隙尺度分布和迁移率。结果表明，与骨料间区域相比，骨料内区域的 MAOM 迁移率明显较低。在 81 至 163 毫米/天的高浸出流量下，骨料内区域中仅 4.8% 至 47.9% 的 MAOM 被动员。此外，剪切诱导的胶体流动而不是溶质解吸随后溶质稀释预计是促进粘土尺寸 MAOM 流动的主要因素。这项研究展示了一种新的实验方案，允许在存在孔隙尺度异质性的情况下对 OM 迁移率进行原位可视化和量化。此外，我们的研究结果还强调了粘土大小的 MAOM 的异质流动性的潜在重要性，这种流动性是由胶体运输对 SOM 周转和分布所促进的。