RedoxPhos: How do physical and biogeochemical conditions in pelagic boundaries control vertical transport and generation of phosphorus species?

气候变化的情景产生后，热力层结的持续时间和稳定性将会增加。之前关于湖泊生产力影响的研究报告了相互矛盾的结果。人们通常认为，厌氧过程将导致沉积物中磷(P)的释放增加。海洋研究的新结果表明，由于矿物相的形成，远洋氧化还原跃层起到了P圈闭的作用。我们的项目旨在观察有机和无机磷形态的转化及其向沉积物的迁移，使用具有不同远洋氧化还原跃层的完全不同的湖泊。从而认为生物磷的时空变化与铁硫锰循环密切相关。这一假设将得到验证，即长时间的层化是否可以通过形成固相来额外去除水体中的磷。为此，将使用天然氧化还原跃层上下的圆柱形沉积圈闭，对沉降物进行采样和结构分析。在长期的现场试验中，暴露出“分体柱”，将抑制沉积物的完全混合，并在沉积物上方的水体中诱导出强烈的梯度。通过化学分析、现代物理结构测定和热力学计算，可以量化远洋边界对沉积物对磷的汇作用的影响。

Scenarios of climate change emanate, that the duration and stability of thermal stratification will increase. Previous studies on the consequences for the productivity of lakes reported contradicting results. It is often assumed that anaerobic processes will lead to an enhanced release of phosphorus (P) from the sediments. New results from marine research show that pelagic redoxclines act as P traps due to the formation of mineral phases. Our project aims at the observation of transformation of organic and inorganic P species and their transport towards the sediment using geochemically quite different lakes with distinct pelagic redoxclines. Thereby the temporal and spatial changes of biogenic phosphorus are considered in close connection with the iron-sulfurand manganese cycle. The hypothesis will be verified whether a prolonged stratification can additionally remove phosphorus from the water body via the formation of solid phases. For this purpose, using cylindrical sedimentation traps above and below of natural redoxclines, settling matter will be sampled and structurally analyzed. In a long-term in situ experiment, exposing ’meromixis columns’, the complete mixing will be suppressed and strong gradients will be induced in the water body above the sediment. By means of chemical analyses, modern physical structure determination and thermodynamic calculations the influence of pelagic boundaries onto the sink function of sediments for phosphorus will be quantified.