Glacial and periglacial floodplain sediments regulate hydrologic transfer of reactive iron to a high arctic fjord
Glacial and periglacial floodplain sediments regulate hydrologic transfer of reactive iron to a high arctic fjord
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DOI：
10.1002/hyp.10701
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发表时间：
2016-04
影响因子：
3.2
通讯作者：
A. Hodson;A. Nowak;H. Christiansen
中科院分区：
文献类型：
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作者：
A. Hodson;A. Nowak;H. Christiansen
描述了在北极高海拔的斯瓦尔巴群岛上，由冰川补给的河流系统排出高海拔冰川周围景观的活性铁（即胶体铁和溶解铁）的运输。在流量和铁浓度之间发现了负的非线性关系，表明沿基流途径铁获取增加。由于冰川是冷基的，并且没有永久冻土内或永久冻土下的地下水泉，因此基流主要由活跃层和下游河谷的崩积和冲积沉积物提供。总的来说，这些环境使河流中的铁通量在仅8公里长的洪泛区中增加了40%，从而为20%的冰川流域带来了6千克铁的输出。研究表明，洪泛区浅层地下水流道中的黄铁矿氧化是活性铁的最重要来源，尽管它在集水区上部的影响要小得多，而其他来源（包括铁石和二次氧化物涂层）也很重要。黄铁矿氧化的微生物催化作用发生在洪泛区，实现了快速、低密度的水交换，提高了高流量下的铁通量，并导致流量与活性铁浓度之间的非线性关系。此外，由于黄铁矿氧化与碳酸盐和硅酸盐矿物风化紧密耦合，其他营养物质如碱阳离子和二氧化硅也被释放到溪流系统中。因此，我们的工作表明，高纬度的北极洪泛平原应该被视为从冰川和冰缘来源向沿海生态系统输送陆地养分的至关重要的调节器。版权所有©2015 John Wiley & Sons， Ltd
The transport of reactive iron (i.e. colloidal and dissolved) by a glacier‐fed stream system draining a high relief periglacial landscape in the high Arctic archipelago of Svalbard is described. A negative, non‐linear relationship between discharge and iron concentration is found, indicative of increased iron acquisition along baseflow pathways. Because the glaciers are cold‐based and there are no intra‐ or sub‐permafrost groundwater springs, baseflow is principally supplied by the active layer and the colluvial and alluvial sediments in the lower valley. Collectively, these environments increase the flux of iron in the stream by 40% over a floodplain length of just 8 km, resulting in 6 kg Fe km−2a−1 of reactive iron export for a 20% glacierized watershed. We show that pyrite oxidation in shallow‐groundwater flowpaths of the floodplain is the most important source of reactive iron, although it is far less influential in the upper parts of the catchment where other sources are significant (including ironstone and secondary oxide coatings). Microbial catalysis of the pyrite oxidation occurs in the floodplain, enabling rapid, hyporheic water exchange to enhance the iron fluxes at high discharge and cause the non‐linear relationship between discharge and reactive iron concentrations. Furthermore, because the pyrite oxidation is tightly coupled to carbonate and silicate mineral weathering, other nutrients such as base cations and silica are also released to the stream system. Our work therefore shows that high Arctic floodplains should be regarded as critically important regulators of terrestrial nutrient fluxes to coastal ecosystems from glacial and periglacial sources. Copyright © 2015 John Wiley & Sons, Ltd.