Friedrich Schiller University Jena, Institute of Geosciences, Department of Hydrogeology, Burgweg 11, D-07749 Jena, Germany.
Friedrich Schiller University Jena, Institute of Geosciences, Department of Hydrogeology, Burgweg 11, D-07749 Jena, Germany.
Sci Total Environ. 2021 Feb 20;756:143774. doi: 10.1016/j.scitotenv.2020.143774. Epub 2020 Nov 14.
Considerable portions of the total mobile inventory of soil seepage are the diverse colloidal and larger suspended materials that essentially contribute to pedogenesis, soil functioning, and nutritional supply of subsurface ecosystems. However, the size- and material-spectra of the total mobile inventory, and field-scale factors controlling its long-term seasonal and episodic dynamics in undisturbed soil, are scarcely investigated so far. In a 4.5-year field-scale study, we utilized automated tension-controlled lysimeters optimized for in situ-sampling of total mobile inventory. Covering different land uses in a low-mountain groundwater recharge area in central Germany, seepage of top- and subsoil was collected at least biweekly and analyzed by hydrochemical and spectromicroscopic techniques (SEM/EDX, nanoparticle tracking analysis). In undisturbed soil, diverse mineral-, mineral-organic, organic, and bioparticles (microbial cells, biotic detritus) up to 75 μm was mobile. Atmospheric forcing was the major factor that governed transport of the total mobile inventory, causing considerable seasonality in seepage pH and certain solutes (e.g. sulphate), as well as episodic fluctuation of particulates. Especially episodic high-flow events, like those following snow melts and lasting rainstorms, primarily contributed to the export of inorganic/organic matter beyond the subsoil-regolith boundary. Individual infiltration events during winter accounted for up to 80% of annual fluxes of particulate organic carbon. On average, a significant proportion of 21% of the mobile organic carbon belonged to the >0.45 μm fraction. The pedological setting and land use mostly impacted the solute signature but were of minor importance for the particle load. Our ongoing monitoring provides evidence of significant episodic nutrient fluxes and unveiled pronounced temporal patterns of field-scale pH fluctuations. We conclude that dynamics of the total mobile inventory, including particulates >0.45 μm must be considered in approaches that budget carbon and elemental fluxes, but also in concepts and models on nutrient cycles and subsurface ecosystem functioning.
土壤渗流的总移动库存中相当大的部分是不同的胶体和较大的悬浮物质，这些物质主要促成了成土作用、土壤功能和地下生态系统的营养供应。然而，迄今为止，总移动库存的大小和物质谱以及控制其在未扰动土壤中长季节和偶发性动态的田间尺度因素还很少被研究。在一项为期 4.5 年的田间尺度研究中，我们利用了优化的自动张力控制渗滤计，用于原位采样总移动库存。该渗滤计涵盖了德国中部低山区地下水补给区的不同土地利用方式，至少每两周收集一次表土和底土的渗流，并通过水化学和光谱显微镜技术（SEM/EDX、纳米颗粒跟踪分析）进行分析。在未扰动的土壤中，不同的矿物、矿物-有机、有机和生物颗粒（微生物细胞、生物碎屑）可达 75μm 是可移动的。大气强迫是控制总移动库存运输的主要因素，导致渗流 pH 值和某些溶质（如硫酸盐）的季节性差异，以及颗粒物质的偶发性波动。特别是像融雪和持续暴雨之后的高流量事件，主要导致无机/有机物质超出亚土壤-风化壳边界的输出。冬季的个别渗透事件占颗粒有机碳年通量的高达 80%。平均而言，移动有机碳中有相当大的比例（21%）属于>0.45μm 级分。土壤学背景和土地利用主要影响溶质特征，但对颗粒负荷的影响较小。我们正在进行的监测提供了显著的偶发性养分通量的证据，并揭示了明显的田间尺度 pH 波动的时间模式。我们的结论是，包括>0.45μm 颗粒在内的总移动库存的动态必须在预算碳和元素通量的方法中考虑，也必须在营养循环和地下生态系统功能的概念和模型中考虑。
