Does anoxic processing of dissolved organic matter affect organic–mineral interactions in paddy soils?
Does anoxic processing of dissolved organic matter affect organic–mineral interactions in paddy soils?
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DOI：
10.1016/j.geoderma.2013.12.006
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发表时间：
2014-09
期刊：
影响因子：
6.1
通讯作者：
A. Hanke;M. Sauerwein;K. Kaiser;K. Kalbitz
中科院分区：
文献类型：
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作者：
A. Hanke;M. Sauerwein;K. Kaiser;K. Kalbitz
土壤中溶解性有机质（DOM）的吸附与含水铁氧化物密切相关，是最重要的吸附剂之一。在水稻土中，水合氧化铁的还原溶解可能会降低表土保留有机质的能力。因此，在表层土壤缺氧条件下产生和处理的溶解有机物被沥滤到仍含有大量含水氧化铁的深层土壤中。然而，缺氧处理对好氧底土层中沥滤DOM吸附的影响尚不清楚。我们测试了从好氧和缺氧溶液中的DOM的吸附典型的水稻底土（针铁矿，水铁矿，含铁蒙皂石）的矿物。吸附的有机碳（OC）含水铁氧化物是五倍以上的好氧比缺氧的解决方案。含铁蒙皂石吸附的含水铁氧化物和氧化和缺氧的解决方案之间的差异比含水铁氧化物的OC不太明显。DOM测试溶液中所含的磷酸盐强烈吸附到氧化铁表面，而蒙皂石几乎不吸附磷酸盐。磷酸盐吸附含水铁氧化物不受氧化还原条件。这一发现与基本不变的平衡pH值一致，表明水合氧化物表面吸附位点的数量和反应性没有变化。此外，我们发现在实验过程中没有矿物还原溶解的迹象。DOM吸附的减少，因此，似乎是由于缺氧过程中DOM的组成变化。
Adsorption of dissolved organic matter (DOM) in soil relates closely to hydrous Fe oxides, being one of the most important adsorbents. In paddy soils, reductive dissolution of hydrous Fe oxides may reduce the capacity of topsoils to retain organic matter. Dissolved organic matter produced and processed under anoxic conditions in the topsoils, thus, is leached into deeper soil horizons that still have considerable amounts of hydrous Fe oxides. Yet, the effect of the anoxic processing on adsorption of the leached DOM in oxic subsoil horizons is not known. We tested the adsorption of DOM from oxic and anoxic solution to minerals typical for paddy subsoils (goethite, ferrihydrite, ferruginous smectite). Adsorption of organic carbon (OC) to hydrous Fe oxides was up to five times larger for oxic than anoxic solutions. Ferruginous smectite adsorbed less OC than hydrous Fe oxides and differences between oxic and anoxic solutions were less pronounced than for the hydrous Fe oxides. Phosphate contained in the DOM test solution adsorbed strongly to the Fe oxide surfaces, while little to no phosphate was adsorbed by the smectite. Phosphate adsorption to hydrous Fe oxides was not affected by redox conditions. That finding is in line with the largely invariable equilibrium pH, suggesting no changes in number and reactivity of sorption sites at the hydrous oxides' surfaces. Also, we found no indications of reductive dissolution of minerals during the experiments. The reduction in DOM sorption, thus, seems to be due to compositional changes of DOM during anoxic processing.