Fractionation of Organic Matter Due to Reaction with Ferrihydrite: Coprecipitation versus Adsorption
Fractionation of Organic Matter Due to Reaction with Ferrihydrite: Coprecipitation versus Adsorption
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DOI：
10.1021/es1023898
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发表时间：
2011-01-15
影响因子：
11.4
通讯作者：
Schwertmann, Udo
中科院分区：
文献类型：
--
作者：
Eusterhues, Karin;Rennert, Thilo;Schwertmann, Udo
在土壤和水中，经常在溶解的有机物存在的情况下形成亚铁水合物。这会扰乱晶体的生长，并导致亚铁水合物和有机物的共沉淀。为了比较共沉淀过程中有机物的化学分级与原始亚铁水合物表面吸附的分级，我们使用(I)森林地面提取物或(Ii)磺化木质素，通过吸附和共沉淀制备了亚铁氢石有机质组合。对反应产物进行了C-13CPMAS核磁共振、傅立叶变换红外光谱和可水解性中性多糖的分析。与原始林地浸出物相比，高铁水合物伴生的有机质富含多糖，尤其是在发生吸附时。此外，甘露糖和葡萄糖优先与亚铁水合物结合，岩藻糖、阿拉伯糖、木糖和半乳糖积累在上清液中。糖单体的这种分级在共沉淀过程中更加明显，并导致(半乳糖+甘露糖)/(阿拉伯糖+木糖)比值增加。用木质素进行的实验表明，与原始木质素相比，高铁水合物伴生物质的芳香族成分含量丰富，但酚醛C/芳香族C的比例较低。由于共沉淀物中甲氧基C的贡献较高，吸附木质素和共沉淀物之间的组成有明显的差异。因此，共沉淀的有机物在数量和组成上可能与吸附的有机物不同。
In soil and water, ferrihydrite frequently forms in the presence of dissolved organic matter. This disturbs crystal growth and gives rise to coprecipitation of ferrihydrite and organic matter. To compare the chemical fractionation of organic matter during coprecipitation with the fractionation involved in adsorption onto pristine ferrihydrite surfaces we prepared ferrihydrite organic matter associations by adsorption and coprecipitation using (i) a forest-floor extract or (ii) a sulfonated lignin. The reaction products were studied by C-13 CPMAS NMR, FTIR, and analysis of hydrolyzable neutral polysaccharides. Relative to the original forest-floor extract, the ferrihydrite-associated organic matter was enriched in polysaccharides, especially when adsorption took place. Moreover, mannose and glucose were bound preferentially to ferrihydrite, while fucose, arabinose, xylose, and galactose accumulated in the supernatant. This fractionation of sugar monomers was more pronounced during coprecipitation and led to an enhanced ratio of (galactose + mannose)/(arabinose + xylose). Experiments with lignin revealed that the ferrihydrite-associated material was enriched in its aromatic components but had a lower ratio of phenolic C to aromatic C than the original lignin. A compositional difference between the adsorbed and coprecipitated lignin is obvious from a higher contribution of methoxy C in the coprecipitated material. Coprecipitated organic matter may thus differ in amount and composition from adsorbed organic matter.