HYDRUS Model Data From 2022 Finkenbiner Study On Soil Isotope Separation

Brief Summary:
Soil physics simulations showed water isotope ratios can differ among drainage, mobile and immobile storages due to transport processes alone, but effects were smaller than field data implying unrepresented processes underly ecohydrologic separation.

Manuscript Abstract:
Field measurements of hydrologic tracers indicate varying magnitudes of geochemical separation between subsurface pore waters. The potential for conventional soil physics alone to explain isotopic differences between preferential flow and tightly-bound water remains unclear. Here, we explored physical drivers of isotopic separations using 650 different model configurations of soil, climate, and mobile/immobile soil-water domain characteristics, without confounding fractionation or plant uptake effects. We find simulations with coarser soils and less precipitation led to reduced separation between pore spaces and drainage. Amplified separations were found with larger immobile domains and, to a lesser extent, higher mobile-immobile transfer rates. Nonetheless, isotopic separations remained small (<4‰ for d2H) across simulations, indicating that contrasting transport dynamics generate limited geochemical differences. Therefore, conventional soil physics alone are unlikely to explain large ecohydrological separations observed elsewhere, and further efforts aimed at reducing methodological artifacts, refining understanding of fractionation processes, and investigating new physiochemical mechanisms are needed.

Dataset Information:
This dataset contains HYDRUS model output used to create four figures in a study by C. Finkenbiner of the ability of soil physics models to represent isotopic separation. Within the four provided folders are model output files with filenames describing their contents. Simulations were ran for 300 days, with the last 100 days used for analysis provided here. Output files are csv files that contain H2 isotope ratios, soil moisture, or soil drainage values across 10 simulations, denoted pv1 - pv10. Simulations were configured to have high, low or zero fractions of immobile soil pore space, denoted as Hf, Lf, and 0f respectively in filenames. Simulations with immobile pore spaces were also configured to have high and low transfer coefficients, denoted as Hw and Lw in file names. For more information please see Finkenbiner et. al. 2022 in Nature Communications (DOI: 10.1038/s41467-022-34215-7) or contact Stephen Good at Oregon State University.

Brief Summary:
土壤物理模拟结果显示，仅通过运移过程，排水储库、可动（mobile）储库与不动（immobile）储库中的水同位素比值即可产生差异，但该效应弱于野外实测数据，这表明未被表征的过程是生态水文分离的潜在成因。

Manuscript Abstract:
水文示踪剂野外实测结果显示，地下孔隙水之间存在程度各异的地球化学分离现象。仅依靠传统土壤物理学理论能否解释优先流与束缚水之间的同位素差异，目前尚无定论。本研究通过650组不同的土壤、气候及可动/不动（mobile/immobile）土壤水区域特征的模型配置，探究了同位素分离的物理驱动机制，且未引入分馏或植物吸收效应作为混淆变量。研究发现，采用粗质地土壤与低降水条件的模拟场景中，孔隙空间与排水储库之间的分离程度会降低；而不动水区域更大的场景中，同位素分离程度会升高，在较小程度上，可动-不动水迁移速率更高的场景也会出现类似效应。尽管如此，所有模拟场景中的同位素分离程度仍较低（氘同位素d2H的差异小于4‰），这表明不同的运移动力学仅能产生有限的地球化学差异。因此，仅依靠传统土壤物理学理论，难以解释其他研究中观测到的大规模生态水文分离现象，未来仍需开展相关工作以减少方法学伪影、深化对分馏过程的认知，并探索新的物理化学机制。

Dataset Information:
本数据集包含HYDRUS模型的输出结果，用于支撑C. Finkenbiner开展的一项关于土壤物理模型表征同位素分离能力的研究中的4幅图表。本次提供的4个文件夹内均包含模型输出文件，其文件名可反映文件内容。所有模拟时长均为300天，本文所用分析数据取自模拟的最后100天。输出文件为CSV（Comma-Separated Values，逗号分隔值）文件，包含10组模拟（标记为pv1至pv10）的氢同位素（H2）比值、土壤含水量或土壤排水量数据。模拟场景被配置为具有高、低或零占比的不动土壤孔隙空间，文件名中分别以Hf、Lf和0f指代此类场景。带有不动孔隙空间的模拟场景还被配置为具有高或低迁移系数，文件名中以Hw和Lw指代此类设置。如需更多信息，请参阅Finkenbiner等人2022年发表于《自然-通讯》（Nature Communications）的论文（DOI: 10.1038/s41467-022-34215-7），或联系俄勒冈州立大学的Stephen Good。