Floodplains can perform nutrient buffering functions and therefore influence the riverine nutrient dynamics depending on the extent of the hydrological connectivity. This work focused on quantifying the adsorption/desorption potential of a degraded floodplain of the Danube River (Lower Lobau) based on sediment characterization (grain size distribution, organic content, and P-fractions) and sediment type-specific P-adsorption via batch experiments. We established an adsorption/desorption budget model with a high temporal and spatial resolution. With this model, we identified spatial patterns related to hydrology and calculated the phosphorus-buffering capacity of permanent and temporary floodplain water bodies. Sediment characteristics were defined by the distance to the inflow area and the hydrological connectivity of the floodplain water bodies. The main factor for the concentration of total phosphorus (Ptot) in the sediments was the grain size distribution. Ptot was 10 times higher in silt-dominated sediments compared with gravel-dominated sediments. Inorganic phosphorus (Pinorg) ranged between 36 and 90%, depending on the organic content of the sediments. Both the adsorption and the desorption potential of soluble reactive phosphorus (SRP) were highest in large, frequently connected water bodies and were strongly controlled by hydrology. The total adsorption potential of the floodplain was up to 40 times higher in wet years (e.g., 2002) than in dry years (e.g., 2003), when floodplain water bodies were connected less frequently to the main channel of the Danube. Up to 75% of the adsorbed SRP was desorbed and released into the water column after periods of connection. Consequently, SRP adsorption directly reduced the P-load in the Danube River main channel. The adsorption/desorption mechanisms worked as a buffering system by taking up the SRP imported during floods and releasing it over a longer period after the floods. This stimulated high primary production in the floodplain water bodies and impacted the overall P-retention of the floodplain.

中文翻译：

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水文连通性对城市洪泛区磷缓冲能力的影响

洪泛区可以发挥养分缓冲功能，因此根据水文连通性的程度影响河流养分动态。这项工作的重点是基于沉积物特征（粒度分布、有机物含量和 P 分数）和通过批量实验的沉积物类型特定 P 吸附来量化多瑙河（Lower Lobau）退化洪泛区的吸附/解吸潜力. 我们建立了具有高时间和空间分辨率的吸附/解吸预算模型。使用该模型，我们确定了与水文相关的空间模式，并计算了永久性和临时性漫滩水体的磷缓冲能力。沉积物特征由到流入区的距离和漫滩水体的水文连通性来定义。沉积物中总磷（Ptot）浓度的主要影响因素是粒度分布。与砾石为主的沉积物相比，粉砂为主的沉积物中的 Ptot 高 10 倍。无机磷 (Pinorg) 的范围在 36% 到 90% 之间，具体取决于沉积物的有机含量。可溶性活性磷 (SRP) 的吸附和解吸潜力在大型、频繁连接的水体中最高，并且受到水文的强烈控制。洪泛区的总吸附潜力在湿润年份（例如 2002 年）比干旱年份（例如 2003 年）高 40 倍，当时洪泛区水体与多瑙河主河道的连接频率较低。在连接一段时间后，高达 75% 的吸附 SRP 被解吸并释放到水柱中。最后，SRP吸附直接降低了多瑙河主河道的P负荷。吸附/解吸机制通过吸收洪水期间输入的 SRP 并在洪水后的较长时间内释放它，起到缓冲系统的作用。这刺激了泛滥平原水体的高初级生产力，并影响了泛滥平原的整体保磷量。