WasserCluster Lunz GmbH, Dr. Carl Kupelwieser Promenade 5, 3293 Lunz am See, Austria.
Sci Total Environ. 2012 Aug 15;432(10):329-37. doi: 10.1016/j.scitotenv.2012.06.025. Epub 2012 Jun 29.
One of the consequences of human impacts on floodplains is a change in sedimentation leading to enhanced floodplain aggradation. Thus, accumulated sediments rich in nutrients might interfere with floodplain restoration. In this study we investigated the phosphorus release behavior of sediments from shallow backwaters of an isolated floodplain of the Danube River situated east of the city of Vienna with the aim to understand the effects of changes in dry/wet cycles on established floodplain sediments. In the light of restoration plans aiming at increased surface water exchange with the river main channel, the response of sediments to frequent alternations between desiccation and inundation periods is a key issue as changes of sediment properties are expected to affect phosphorus release. In order to determine the effect of changing hydrological conditions on internal phosphorus loading, we exposed sediments to different dry/wet treatments in a laboratory experiment. Total phosphorus (TP) release from sediments into the water column increased with increasing duration of dry periods prior to re-wetting. Partial correlation analysis showed significant positive correlations between ΔTP and ΔNH(4)(+) as well as between ΔTP and ΔFe(3+) concentrations (Δ refers to the difference between the final and initial concentration during the wetting period), indicating that enhanced mineralization rates leading to a concomitant release of NH(4)(+) and TP and the reduction of iron hydroxides leading to a concomitant release of Fe(3+) and TP are the mechanisms responsible for the rise in TP. Repeated drying and wetting resulted in elevated phosphorus release. This effect was more pronounced when drying periods led to an 80% reduction in water content, indicating that the degree of drying is a major determinant controlling phosphorus release upon re-wetting. The reconnection of isolated floodplains will favor fluctuating hydrologic conditions and is therefore expected to initially lead to high rates of phosphorus release from sediments.
人类活动对洪泛平原的影响之一是导致沉积作用发生变化，从而增强洪泛平原的淤积。因此，富含养分的堆积物可能会干扰洪泛平原的恢复。本研究调查了多瑙河东部孤立洪泛平原浅滩回水沉积物的磷释放行为，目的是了解干湿循环变化对已建立的洪泛平原沉积物的影响。鉴于旨在增加地表水与河流主河道交换的恢复计划，沉积物对频繁干湿交替的响应是一个关键问题，因为沉积物性质的变化预计会影响磷的释放。为了确定水文条件变化对内部磷负荷的影响，我们在实验室实验中使沉积物经历不同的干湿处理。在重新湿润之前，干燥期持续时间的增加导致沉积物向水柱中释放的总磷（TP）增加。偏相关分析表明，ΔTP 与 ΔNH4（+）以及 ΔTP 与 ΔFe（3+）浓度之间存在显著正相关（Δ表示在湿润期内最终和初始浓度之间的差异），表明增强的矿化速率导致同时释放 NH4（+）和 TP，以及铁氢氧化物的减少导致同时释放 Fe（3+）和 TP，是导致 TP 上升的机制。反复干燥和湿润导致磷释放增加。当干燥期导致含水量减少 80%时，这种效果更为明显，这表明干燥程度是控制再湿润时磷释放的主要决定因素。孤立洪泛平原的重新连接将有利于波动的水文条件，因此预计最初会导致沉积物中磷的释放率很高。
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