In situ, high-resolution evidence for iron-coupled mobilization of phosphorus in sediments.
In situ, high-resolution evidence for iron-coupled mobilization of phosphorus in sediments.
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沉积物中铁耦合磷迁移的原位高分辨率证据
DOI：
10.1038/srep24341
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发表时间：
2016-04-18
影响因子：
4.6
通讯作者：
Zhang C
中科院分区：
文献类型：
--
作者：
Ding S;Wang Y;Wang D;Li YY;Gong M;Zhang C
70多年来，含磷铁(铁)(氧)氧化物的还原溶解被认为是沉积物中磷(P)的主要活化机制。然而，到目前为止，几乎没有现场证据支持这一假设。本研究选取了大型富营养化太湖的16个样点进行调查。利用新研制的薄膜扩散梯度(ZrO-Cherex DGT)探针，以毫米级空间分辨率同时测量沉积物中主要释放出的不稳定铁和磷。DGT不稳定的Fe和P在14个点上呈显著正相关，这意味着在Fe(羟基)氧化物的还原溶解后P的释放。沉积物中Fe(II)和P的补给对DGT扰动的释放起到了缓冲作用，进一步验证了Fe偶联活化P的机理。DGT不稳定的Fe/P与易还原(含氧)氧化物Fe/P的比值呈正相关，表明该固相在释放P之前应保留P。这些结果为沉积物中Fe和P之间的耦合提供了直接证据，并进一步确定了参与耦合过程的易还原的Fe(羟基)氧化物物种。
Reductive dissolution of phosphorus-bearing iron (Fe) (oxyhydr)oxides has been regarded as a primary mechanism responsible for the mobilization of phosphorus (P) in sediments for over 70 years. However, to date there is little in situ evidence to support this hypothesis. In this study, a total of 16 sites in the large eutrophic Lake Taihu were selected for investigation. Newly-developed diffusive gradients in thin films (ZrO-Chelex DGT) probes were deployed to simultaneously measure labile Fe and P mainly released from sediment solids at millimeter spatial resolution. Significantly positive correlations were observed between DGT-labile Fe and P at 14 sites, implying a release of P following reductive dissolution of Fe (oxyhydr)oxides. A coincident resupply of Fe(II) and P was observed from sediment solids to buffer their releases from DGT perturbance, further verifying the mechanism of Fe-coupled mobilization of P. The ratio of DGT-labile Fe/P was found to be positively correlated with the ratio of easily reducible (oxyhydr)oxide Fe to its associated P, indicating that this solid phase should retain P prior to its release. The results provide direct evidence for the coupling between Fe and P in sediments and further identify the easily reducible Fe (oxyhydr)oxide species involved in the coupling process.