Collaborative Research: Combining complex systems tools, process-based modelling and experiments to bridge scales in low temperature geochemistry

研究人员将联合收割机结合新的建模方法和实验，以了解溪流沃茨中有机碳增加的机制。碳是水生食物网的重要组成部分，对水质起着重要作用。这项研究是新颖的，因为不是从当地观察到的现象开始，并建立基于过程的模型，将这些机制扩展到更大的规模，研究人员团队将挖掘大型观测数据集，以获得更多的全球模式，然后调查较小规模的过程。该项目为多名研究生和本科生提供建模，实验室和现场方法的跨学科培训。此外，该小组将与少数民族服务，K-5小学开发和管理佛蒙特州的K-5教师的专业发展讲习班。因为森林水源集水区覆盖大的地理区域，他们有不成比例的影响溶解部分的有机碳（DOC），并密切监测整个地球仪。大量研究已经证明了北方森林溪流DOC通量的显著增加，并对气候变化、土地利用或降水组成（即从酸化中恢复）等潜在原因进行了辩论。缺乏对潜在驱动DOC释放的具体机制的关注，使得未来DOC通量的预测几乎不可能。研究人员建议通过建模和实验相结合来解决这一差距，以测试以下假设：1）溪流DOC通量的增加是由区域观察到的酸化恢复驱动的（即湿沉降和干沉降的pH增加和离子强度降低），2）DOC从在这些变化条件下变得不稳定的土壤团聚体中释放，团聚体稳定性和DOC释放是土壤组成和矿物学的函数，导致不同的响应（DOC增加的存在或不存在），尽管潜在的相似区域强迫。使用新的数据驱动建模技术的大数据分析将使用USGS和临界区观测数据集来探测区域尺度数据（100公里）并确定一般模式（测试假设1）。这一步骤的结果将为选择地点提供信息，以便使用反应传输模型和实验（测试假设2-3）在集水区（公里）到土壤团聚体尺度（微米）进行更详细的基于过程的调查。这项研究解决了一个备受争议的主题在C动力学（即增加DOC通量），并进一步努力在低温地球化学的尺度，学科和方法的整合框架。将统计和基于过程的建模与实验相结合，以弥合10个数量级的尺度变化，这对低温地球化学领域来说是新颖的，可能具有变革性。这项研究的影响扩大了跨学科的培训提供了三个研究生和多个本科生。此外，调查人员将与教育学院和一所少数民族服务的K-5学校合作，为佛蒙特州的K-5教师开发和管理一个专业发展讲习班。本次研讨会的目标是：i）为K-5教育工作者提供关于关键区的专业发展，作为可持续性学习的框架; ii）开始与参与的教育工作者一起为适当的K-5水平开发教学模块。

Investigators will combine new modelling approaches and experiments to understand the mechanisms by which organic carbon in stream waters increases. Carbon is an important constituent in the aquatic food web and plays an important role in water quality. This research is novel because, instead of beginning with locally-observed phenomena and build process-based models that scale those mechanisms up to a larger scale, the investigator team will mine large observatory datasets for more global patterns followed by the investigation of smaller scale processes. The project provides interdisciplinary training in modeling, lab and field approaches for multiple graduate and undergraduate students. Furthermore, the team will collaborate with a minority-serving, K-5 elementary school to develop and administer a professional development workshop for Vermont's K-5 teachers.Because forested headwater catchments cover large geographical areas, they have disproportionate effects on the dissolved fraction of organic carbon (DOC) and are closely monitored across the globe. Significant increases in DOC fluxes from forested streams across the northern hemisphere have been documented by numerous studies and potential causes such as changes in climate, land use or precipitation composition (i.e. recovery from acidification) are debated. The lack of focus on the specific mechanisms potentially driving the DOC release makes the prediction of future DOC fluxes nearly impossible. The investigators propose to address this gap with a combination of modelling and experiments to test the hypotheses that 1) an increase in stream water DOC flux is driven by the regionally observed recovery from acidification (i.e. the increase in pH and decrease in ionic strength of wet and dry deposition), 2) DOC is released from soil aggregates that become unstable under these changing conditions, and 3) aggregate stability and DOC release is a function of soil composition and mineralogy, leading to the varied responses (presence or absence of DOC increase) despite potentially similar regional forcings. Big Data analysis using novel data-driven modelling techniques will use USGS and Critical Zone Observatory datasets to probe regional-scale data (100 km) and identify general patterns (test hypotheses 1). Results from this step will inform selection of sites for more detailed process-based investigation at the catchment (km) to soil aggregate scale (micrometer) using Reactive Transport Modelling and experiments (test hypotheses 2-3). This research addresses a highly debated topic in C dynamics (i.e. increase DOC fluxes) and furthermore works toward a framework for the integration of scales, disciplines and approaches in low temperature geochemistry. The combination of statistical and process-based modelling with experiments to bridge scales varying 10 orders of magnitude is novel and potentially transformative for the field of low temperature geochemistry. The impact of this research is broadened by the interdisciplinary training provided for three graduate students and multiple undergraduate students. Furthermore, the investigators will collaborate with the College of Education and a minority-serving, K-5 school to develop and administer a professional development workshop for Vermont's K-5 teachers. Goals for this workshop are to i) provide professional development for K-5 educators on the Critical Zone as a framework for sustainability learning and ii) to begin to develop teaching modules with participating educators for the appropriate K-5 level.