Exploring dissolved organic carbon cycling at the stream–groundwater interface across a third-order, lowland stream network
Exploring dissolved organic carbon cycling at the stream–groundwater interface across a third-order, lowland stream network
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DOI：
10.1007/s10533-017-0404-z
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发表时间：
2017
期刊：
影响因子：
4
通讯作者：
S. S. Ruhala-S.;J. Zarnetske;D. T. Long;J. Lee-Cullin;S. Plont;Evan R. Wiewiora
中科院分区：
文献类型：
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作者：
S. S. Ruhala-S.;J. Zarnetske;D. T. Long;J. Lee-Cullin;S. Plont;Evan R. Wiewiora
河流-地下水界面（SGI）被认为是河流网络中溶解有机碳（DOC）处理的重要位置（例如，降解、去除），因为它被认为是微生物活性和生物化学反应的热点。这项研究是第一次尝试收集和评估DOC的条件在SGI整个流网络，整个三级，低地流域在美国密歇根州。我们提出了这个独特的数据集的初步探索，并强调在这些规模的工作时的一些挑战。总体而言，我们的研究结果表明，SGI DOC条件是复杂的网络规模，不符合预测的基础上，以前的点和小规模的研究。我们发现没有强有力的模式，DOC去除SGI内的网络规模，即使使用氯化物和温度作为天然示踪剂，以区分水文过程和影响DOC循环的地球化学反应。相反，DOC数量和分子质量的趋势表明，潜在的生物反应，包括好氧微生物呼吸，DOC浓度的影响，只有在一些网站，而地面和流表面沃茨的物理混合似乎解释了大多数DOC浓度在其他网站的观察到的变化。此外，结果表明，无论是SGI网站指示DOC去除，也DOC分子质量的变化与流的顺序。它确实揭示了DOC的变化在地表水，地下水，和SGI的位置始终是最大的SGI的浅层沉积物，表明SGI是一个系统的不同位置的DOC条件在流域。我们的经验流网络规模的SGI数据是第一批与最近开发的基于过程的网络规模SGI模型兼容的数据。我们的研究结果表明，这些过程为基础的模型可能无法准确地代表SGI交换的低地，地下水排放为主的河流一样，在这项研究中。最后，这项研究表明，需要新的方法来实现的目标，使SGI观测和网络规模的地球化学过程和理论。为了帮助开发这些方法，我们提供了我们使用的方法的讨论（即，“经验教训”），这可能成为SGI孔隙水的系统数据分析的基础，在未来的网络范围内的SGI地球化学研究。
The stream–groundwater interface (SGI) is thought to be an important location within stream networks for dissolved organic carbon (DOC) processing (e.g., degradation, removal), since it is considered a hotspot for microbial activity and biogeochemical reactions. This research is one of the first attempts to collect and assess DOC conditions at the SGI across a stream network—an entire third-order, lowland watershed in Michigan, USA. We present an initial exploration of this unique data set and highlight some of the challenges when working at these scales. Overall, our results show that SGI DOC conditions are complex at the network scale and do not conform to predictions based upon previous point- and small-scale studies. We found no strong pattern of DOC removal within the SGI at the network scale even after using chloride and temperature as natural tracers to differentiate between hydrological processes and biogeochemical reactions influencing DOC cycling. Instead, trends in DOC quantity and molecular qualities suggest that potential biotic reactions, including aerobic microbial respiration, had an influence on DOC concentrations at only some of the sites, while physical mixing of ground and stream surface waters appears to explain the majority of the observed changes in DOC concentrations at other sites. In addition, results show that neither SGI sites indicating DOC removal nor DOC molecular quality shifts measured correlated with stream order. It did reveal that DOC variability across surface water, groundwater, and the SGI locations was consistently greatest in the shallow sediments of the SGI, demonstrating that the SGI is a systematically distinct location for DOC conditions in the watershed. Our empirical stream network-scale SGI data are some of the first that are compatible with recently developed process-based, network-scale, SGI models. Our results indicate that these process-based models may not accurately represent SGI exchange of lowland, groundwater discharge-dominated streams like the one in this study. Lastly, this study shows that new methods are needed to achieve the goal of making and linking SGI observations to network-scale biogeochemical processes and theory. To help develop these methods we provide a discussion of the approach we used (i.e., “lessons-learned”) that might become the basis for systematic data analysis of SGI porewaters in future, network-wide biogeochemical studies of the SGI.