Nanoparticles and colloids as vectors of P-losses and -redistribution during forest ecosystem development

天然纳米颗粒和胶体具有较大的比表面积和反应活性，是磷的主要吸附剂，因此在很大程度上控制着土壤中磷的移动性和生物有效性。我们计划继续和扩大SPP 1685第一阶段关于土壤、土壤渗滤液和径流中天然纳米颗粒和胶体在森林生态系统中磷的储存、转移和损失中的作用的富有成效的研究。在第一个项目阶段确定的不同的天然纳米颗粒和胶体类型将在协作柱、蒸渗仪和新的田间实验中进一步表征。这些实验的新方面是纳入了一个含有碳酸盐土壤的森林生态系统，并探索了P-、Corg-和N-循环之间的化学计量联系。为此，SPP 1685第一阶段建立的场流动分馏与电感耦合等离子体质谱仪和有机碳检测器(OCD)结合纳米颗粒、胶体和溶解相的铁、铝、锰、钙、硅测定磷和碳的新联用，将扩展到对有机氮的额外检测(ON)。这些扩展的分析可能性将被使用，并有助于战略规划方案1685第二阶段的中心项目。因此，首次能够阐明胶体在营养限制和N、P和N+P添加下与森林生态系统P(再)循环的相关性(WP 2.1)。此外，我们将通过量化峰值流动事件(WP2.3)期间不同空间尺度上结合到纳米颗粒和胶体上的P的横向和垂直转移来促进联合通量簇活动。此外，为了判断这些磷损失在磷循环中的作用，将对不同磷状况(WP2.2)的山毛榉幼苗和土壤胶体进行根际试验。为了更好地表征磷与纳米颗粒和胶体的结合，将对无机和有机磷化合物(WP 2.4)进行特定吸附实验，并对天然纳米颗粒和胶体进行31P-核磁共振测量。总体而言，拟议的实验结果将改善我们目前对磷通量和循环的理解，不仅是森林生态系统，而且是其他陆地生态系统。

Natural nanoparticles and colloids with their large specific surface area and reactivity are primary sorbents of P and thus largely control phosphorus mobility and bioavailability in soils. We plan to continue and expand the fruitful research of phase I of SPP 1685 on the role of natural nanoparticles and colloids in soils, soil leachates and runoff for the phosphorus storage, transfer and losses in forest ecosystems. The different natural nanoparticle and colloid types identified in the first project phase will be further characterised in collaborative column, lysimeter and new field experiments. New aspects in these experiments are the inclusion of a forest ecosystem with a carbonate-containing soil and the exploration stoichiometric linkages between P-, Corg- and N-cycles. To this end, the novel coupling of field-flow-fractionation with ICP-MS and organic carbon detector (OCD) established in the first phase of SPP 1685 for determining concentrations of P and C in combination with Fe, Al, Mn, Ca, Si of nanoparticles, colloids and of the dissolved phase, shall be extended to pioneering the additional detection of organic nitrogen (ON). These extended analytical possibilities will be employed and contribute to the central project of the second phase of SPP 1685. Thereby for the first time, enabling the elucidation of the relevance of colloids for P (re)cycling in forest ecosystems under nutrient limitation and N, P and N+P addition (WP 2.1). Moreover, we will contribute to the joint flux cluster activities by quantifying the lateral and vertical transfer of P bound to nanoparticles and colloids on different spatial scales during peak flow events (WP 2.3). Furthermore, in order to judge the role of these P losses for P recycling, rhizotrone experiments will be conducted with beech seedlings and soil colloids of different P status (WP 2.2). To better characterize the binding of P to nanoparticles and colloids, specific sorption experiments with inorganic and organic P compounds (WP 2.4) and 31P-NMR measurements on natural nanoparticles and colloids will be undertaken. Overall, the outcome of the proposed experiments shall improve our current understanding of P fluxes and cycling not only of forest ecosystems but also of other terrestrial ecosystems.