Dieter Daniela, Herzog Christiane, Hupfer Michael
Department of Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587, Berlin, Germany.
Environ Sci Pollut Res Int. 2015 Nov;22(21):17065-81. doi: 10.1007/s11356-015-4904-x. Epub 2015 Jul 1.
Sediment drying associated with large water level fluctuations is an increasingly common feature of temporary streams and lakes worldwide. Drying-induced sediment aeration and re-flooding periodically alter redox conditions, and therefore stimulate redox-sensitive processes influencing phosphorus (P) binding forms. We experimentally tested the effects of drying on P binding forms, and the P sorption potential, by drying and re-flooding lake sediments in the laboratory. Wet and dried fine sediments were re-flooded in columns, and the overlying water was continuously re-stocked to a constant P concentration. We measured changes in P forms, P uptake rates, and the pore water dynamics in each column over 36 weeks. Drying decreased the fraction of stable P, stimulated the mineralization of organic P, and increased the proportion of labile and reductant-soluble forms. Drying of sediment furthermore reduced its P sorption affinity and capacity by up to 32% in batch equilibrium experiments, and led to a fourfold increase in sediment compaction which increased P uptake rates by a factor of 1.7 in sediment column experiments. Compaction due to drying also induced the development of a sharp gradient below which P was mobilized. These results indicate that in fine sediments, a single drying event can result in the transformation of P components into more labile forms which accumulate in the uppermost sediment layer, therefore raising the potential for a pulsed P release under reducing conditions.
与大幅度水位波动相关的沉积物干燥是全球范围内临时性溪流和湖泊日益常见的特征。干燥导致的沉积物曝气和再次淹没会周期性地改变氧化还原条件，从而刺激影响磷（P）结合形态的氧化还原敏感过程。我们在实验室中通过对湖泊沉积物进行干燥和再次淹没来实验测试干燥对P结合形态以及P吸附潜力的影响。将湿润和干燥的细粒沉积物重新置于柱中，并向上覆水体持续补充至恒定的P浓度。我们测量了36周内各柱中P形态、P吸收速率和孔隙水动态的变化。干燥降低了稳定P的比例，刺激了有机P的矿化，并增加了不稳定和可还原溶解形态的比例。此外，在批量平衡实验中，沉积物干燥使其P吸附亲和力和容量降低了32%，并导致沉积物压实度增加了四倍，这使得沉积物柱实验中的P吸收速率提高了1.7倍。干燥导致的压实还引发了一个陡峭梯度的形成，在此梯度以下P被释放出来。这些结果表明，在细粒沉积物中，单次干燥事件可导致P组分转化为更不稳定的形态，这些形态积聚在沉积物最上层，因此增加了在还原条件下P脉冲式释放的可能性。
