SSF NOVEL TRACERS - Exploration of biogeochemical tracers (environmental and artificial DNA, organic carbon) for tracing subsurface stormflow

地下水流路径、水源和地下水文连通性的推断受到各种假设和稀疏的直接测量机会的限制。为了响应对新示踪剂的需求，以检测地下暴雨流（SSF）的源区域，微生物群落组成推断通过环境DNA（eDNA）元编码以及空间差异的水溶性有机物的光学特性（WSOM;吸光度和荧光）在土壤中提供了迄今为止很少考虑的可能性。根据地形和土壤性质，形成特定的栖息地土壤微生物和大型社区，这可以映射为空间eDNA模式，并用于精确定位和区域化的SSF的源区。eDNA的组成是土壤有机碳组成的函数，这表明它们之间有密切的联系。人工示踪剂DNA的应用提供了进行多个示踪剂实验的可能性，低技术工作量和高信息含量的地下流动路径。然而，这些新的示踪剂的适用性，也在组合，相对于SSF尚未进行严格的评估。因此，我们建议评估潜在的eDNA从自然群落以及人工应用的示踪剂DNA和光学特性的WSOM作为非保守的示踪剂SSF和地下连接在四个对比流域在低和高的山脉（绍尔兰，矿石山，黑森林，阿尔卑斯山）。我们将在这些集水区的12个山坡进行土壤采样，每个山坡有10个土壤剖面，以检测eDNA和WSOM的空间和深度分布。为了研究eDNA和WSOM的深度依赖性的时间变异性，我们将采取地下径流在不同的土壤深度在一个挖沟的山坡在每个集水区在自然降雨径流事件的水样。在人工灌溉试验中，利用自行设计和应用的人工DNA示踪技术，对两个沟坡（低山和高山）的SSF产生和流动路径进行了详细的研究。为了在实验室中分析eDNA和WSOM，我们将使用一系列最先进的实验室设备和方法（TOC分析仪，荧光光谱法，高通量扩增子测序和定量PCR）。多变量统计技术的使用（例如，PCA，CCA，PARAFAC，WGCNA））将有助于识别SSF的时空格局，以确定SSF的源区，并检测SSF的生化特征作为SSF的示踪剂。在对比景观的山坡尺度上系统地调查eDNA和WSOM将允许评估这些不同的生化示踪剂来追踪SSF。此外，这些调查将建立一个独特的综合数据库，用于推导地球化学特征，以确定SSF的源区和流动路径。

Inferences of subsurface flow paths, sources and subsurface hydrological connectivity are limited by the various assumptions and sparse direct measurement opportunities. In response to the need for new tracers to detect source areas of subsurface stormflow (SSF), microbial community composition inferred via environmental DNA (eDNA) metabarcoding as well as the spatial differences of optical characteristics of water-soluble organic matter (WSOM; absorbance and fluorescence) in soils offers a so far little considered possibility. Depending on topographic and soil properties, specific habitats for soil microbial and macro-communities are formed, which can be mapped as spatial eDNA patterns and used to precisely locate and regionalize the source areas of SSF. Composition of eDNA is a found to be function of soil organic carbon composition which suggests a close connection of these. The application of artificial tracer DNA offers the possibility to carry out multiple tracer experiments with low technical effort and high information content with respect to subsurface flow paths. However, a rigorous assessment of the applicability of these novel tracers, also in combination, with respect to SSF has not yet been carried out. Thus, we propose to evaluate the potential of eDNA from natural communities as well as artificially applied tracer DNA and optical characteristics of WSOM as non-conservative tracers for SSF and subsurface connectivity in four contrasting catchments in the low and high mountain ranges (Sauerland, Ore Mountains, Black Forest, Alps). We will carry out soil sampling on 12 hillslopes in these catchments each with 10 soil profiles to detect spatial and dept-related distribution of eDNA and WSOM. In order to investigate the dept-dependent temporal variability of eDNA and WSOM we will take water samples of the subsurface runoff in different soil depths at one trenched hillslope in every catchment during natural rainfall-runoff events. During artificial irrigation experiments at two trenched hillslopes (low and high mountain) the SSF generation and flow paths will be studied in detail using self-designed and applied artificial DNA tracers. To analyze eDNA and WSOM in the lab we will use an array of state-of-the-art laboratory equipment and methods (TOC-Analyzer, Fluorescence Spectrometry, High-throughput amplicon sequencing and quantitative PCR). The use of multivariate statistical techniques (e.g., PCA, CCA, PARAFAC, Clusteranalysis, WGCNA)) will help to identify temporal and spatial patterns to identify source areas of SSF and to detect biochemical signatures of SSF as tracer for SSF.This systematically investigation of eDNA and WSOM at the hillslope scale in contrasting landscape will allow to assess these different biochemical tracers to trace SSF. Moreover, these investigations will create a unique comprehensive database for the derivation of biogeochemical signatures to identify source areas and flow pathways of SSF.