SGER: Preferential and Stable Sorption of N- vs. C-rich Soil Organic Matter on Mineral Surfaces

尽管人们普遍认识到土壤有机质（SOM）对土壤化学、土壤水文和土壤结构的重要性，但对影响土壤有机质形成和稳定性的因素的详细机制理解尚未出现。这项探索性研究工作的智力价值在于在土壤微团粒尺度上对SOM的形成和稳定性进行检查和探索。具体来说，通过粒度-密度分选、SOM放射性碳定年和氮含量测定，该研究将验证一个新的假设，即最靠近矿物表面的土壤有机化合物是最稳定的，随着有机物与矿物表面距离的增加，稳定性降低。第二种假设认为，靠近矿物表面的土壤有机化合物特别富氮，它们的含氮成分（胺基）是它们与矿物表面特别稳定结合的原因。这项研究的广泛影响有许多方面。土壤有机质对全球福祉和安全至关重要，因为土壤有机质在很大程度上提供维持农业和森林生产力所需的氮、其他养分和土壤结构。在全球范围内，SOM形成和/或稳定性的变化可能对大气二氧化碳浓度产生影响，从而影响全球气候。更好地了解土壤有机质形成和流失的控制机制将大大提高我们有效管理土壤有机质的能力，以促进商品生产和侵蚀控制，并减少土壤二氧化碳向大气的通量。

Despite the generally acknowledged importance of soil organic matter (SOM) to soil chemistry, soil hydrology, and soil structure, a detailed mechanistic understanding of the factors that influence SOM formation and stability has yet to emerge. The intellectual merit of this exploratory research effort lies in the examination and exploration of SOM formation and stability at the scale of the soil microaggregate. Specifically, using size-density-fractionation, radiocarbon dating of SOM, and nitrogen content determinations, the research will test a novel hypothesis that soil organic compounds nearest to mineral surfaces are the most stabilized, with stability decreasing with increasing distance of the organics from the mineral surfaces. A second hypothesis posits that soil organic compounds near mineral surfaces are especially nitrogen-rich, and that their nitrogen-containing components (amine groups) are responsible for their especially stable binding to mineral surfaces. There are many facets to the broader impacts of this research. Soil organic matter is critical to global well-being and security in that SOM supplies in large part the nitrogen, other nutrients, and soil structure needed to sustain agricultural and forest productivity. Changes in SOM formation and/or stability on a global scale may have consequences for atmospheric carbon dioxide concentrations and thus global climate. A better understanding of the mechanisms controlling SOM formation and loss will greatly improve our ability to efficiently manage SOM for commodity production and erosion control, and to mitigate soil carbon dioxide flux to the atmosphere.