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Calcareous organic matter coatings sequester siderophores in alkaline soils.
Science of the Total Environment ( IF 8.2 ) Pub Date : 2020-03-26 , DOI: 10.1016/j.scitotenv.2020.138250 Rene M Boiteau 1 , Ravi Kukkadapu 2 , John B Cliff 2 , Chuck R Smallwood 3 , Libor Kovarik 2 , Mark G Wirth 2 , Mark H Engelhard 2 , Tamas Varga 2 , Alice Dohnalkova 2 , Daniel E Perea 2 , Thomas Wietsma 2 , James J Moran 2 , Kirsten S Hofmockel 4
Science of the Total Environment ( IF 8.2 ) Pub Date : 2020-03-26 , DOI: 10.1016/j.scitotenv.2020.138250 Rene M Boiteau 1 , Ravi Kukkadapu 2 , John B Cliff 2 , Chuck R Smallwood 3 , Libor Kovarik 2 , Mark G Wirth 2 , Mark H Engelhard 2 , Tamas Varga 2 , Alice Dohnalkova 2 , Daniel E Perea 2 , Thomas Wietsma 2 , James J Moran 2 , Kirsten S Hofmockel 4
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Although most studies of organic matter (OM) stabilization in soils have focused on adsorption to aluminosilicate and iron-oxide minerals due to their strong interactions with organic nucleophiles, stabilization within alkaline soils has been empirically correlated with exchangeable Ca. Yet the extent of competing processes within natural soils remains unclear because of inadequate characterization of soil mineralogy and OM distribution within the soil in relation to minerals, particularly in C poor alkaline soils. In this study, we employed bulk and surface-sensitive spectroscopic methods including X-ray diffraction, 57Fe-Mössbauer, and X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM) methods to investigate the minerology and soil organic C and N distribution on individual fine particles within an alkaline soil. Microscopy and XPS analyses demonstrated preferential sorption of Ca-containing OM onto surfaces of Fe-oxides and calcite. This result was unexpected given that the bulk combined amounts of quartz and Fe-containing feldspars of the soil constitute ~90% of total minerals and the surface atomic composition was largely Fe and Al (>10% combined) compared to Ca (4.2%). Soil sorption experiments were conducted with two siderophores, pyoverdine and enterobactin, to evaluate the adsorption of organic molecules with functional groups that strongly and preferentially bind Fe. A greater fraction of pyoverdine was adsorbed compared to enterobactin, which is smaller, less polar, and has a lower aqueous solubility. Using NanoSIMS to map the distribution of isotopically-labeled siderophores, we observed correlations with Ca and Fe, along with strong isotopic dilution with native C, indicating associations with OM coatings rather than with bare mineral surfaces. We propose a mechanism of adsorption by which organics aggregate within alkaline soils via cation bridging, favoring the stabilization of larger molecules with a greater number of nucleophilic functional groups.
中文翻译：
钙质有机物质涂层隔离碱性土壤中的铁载体。
尽管大多数土壤中有机质（OM）稳定化的研究都集中在铝硅酸盐和氧化铁矿物质的吸附上，因为它们与有机亲核试剂有很强的相互作用，但是碱性土壤中的稳定化在经验上与可交换的Ca相关。然而，由于土壤矿物学特征和土壤中与矿物质有关的土壤有机质分布不充分，特别是在碳贫乏的碱性土壤中，天然土壤中竞争过程的程度仍不清楚。在这项研究中，我们采用了体积敏感和表面敏感的光谱方法，包括X射线衍射，57Fe-Mössbauer和X射线光发射光谱（XPS）以及透射电子显微镜（TEM）方法来研究矿物学和土壤有机碳和N在碱性土壤中单个细颗粒上的分布。显微镜和XPS分析表明，含Ca的OM优先吸附在Fe-氧化物和方解石的表面上。考虑到土壤中石英和含铁长石的总含量占总矿物质的90％，并且与Ca（4.2％）相比，表面原子组成主要是Fe和Al（总含量> 10％），因此该结果是出乎意料的。土壤吸附实验是用泛铁定和肠杆菌素这两种铁载体进行的，以评估有机分子与牢固并优先结合铁的官能团的吸附。与肠杆菌素相比，更多的吡over定被吸附，后者更小，极性更小且水溶性更低。使用NanoSIMS绘制同位素标记的铁载体的分布图，我们观察到了与Ca和Fe的相关性，以及天然C的强烈同位素稀释，表明与OM涂层有关，而不是与裸露的矿物表面有关。我们提出了一种吸附机制，通过该机制有机物通过阳离子桥接在碱性土壤中聚集，有利于稳定具有较大数量亲核官能团的较大分子。
更新日期：2020-03-27
中文翻译：
钙质有机物质涂层隔离碱性土壤中的铁载体。
尽管大多数土壤中有机质（OM）稳定化的研究都集中在铝硅酸盐和氧化铁矿物质的吸附上，因为它们与有机亲核试剂有很强的相互作用，但是碱性土壤中的稳定化在经验上与可交换的Ca相关。然而，由于土壤矿物学特征和土壤中与矿物质有关的土壤有机质分布不充分，特别是在碳贫乏的碱性土壤中，天然土壤中竞争过程的程度仍不清楚。在这项研究中，我们采用了体积敏感和表面敏感的光谱方法，包括X射线衍射，57Fe-Mössbauer和X射线光发射光谱（XPS）以及透射电子显微镜（TEM）方法来研究矿物学和土壤有机碳和N在碱性土壤中单个细颗粒上的分布。显微镜和XPS分析表明，含Ca的OM优先吸附在Fe-氧化物和方解石的表面上。考虑到土壤中石英和含铁长石的总含量占总矿物质的90％，并且与Ca（4.2％）相比，表面原子组成主要是Fe和Al（总含量> 10％），因此该结果是出乎意料的。土壤吸附实验是用泛铁定和肠杆菌素这两种铁载体进行的，以评估有机分子与牢固并优先结合铁的官能团的吸附。与肠杆菌素相比，更多的吡over定被吸附，后者更小，极性更小且水溶性更低。使用NanoSIMS绘制同位素标记的铁载体的分布图，我们观察到了与Ca和Fe的相关性，以及天然C的强烈同位素稀释，表明与OM涂层有关，而不是与裸露的矿物表面有关。我们提出了一种吸附机制，通过该机制有机物通过阳离子桥接在碱性土壤中聚集，有利于稳定具有较大数量亲核官能团的较大分子。
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