Addressing a significant knowledge gap in fluvial system atmospheric CO2 efflux: the contribution from karst landscapes

解决河流系统大气二氧化碳流出方面的重大知识差距：喀斯特景观的贡献

• 批准号: NE/N002806/1
• 负责人: Susan Waldron
• 金额: $ 44.75万
• 依托单位: University of Glasgow
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN002806%2F1
• 关键词: Addressing; significant; knowledge; gap; fluvial

Karst landscapes cover a large proportion of the Earth's land surface: ~ 12% They represent an important C store on land, and also are considered to play an important role in climate regulation by consuming atmospheric CO2 during chemical weathering. However, we cannot be certain how effective this sink is if we do not know how efficiently the rivers draining karst landscapes remobilise weathered C to the atmosphere as CO2. Further, although there is a large body of research on how much C is carried away from weathered karst systems, researchers have not yet quantified by direct measurement the C return to the atmosphere from rivers. We propose to measure this CO2 degassing from rivers in karst systems and using chemical tracers that can distinguish between different source of carbon in the rivers, quantify how much C comes from the different sources and how these contributions change with different land use change, or as season and river flow change. We will do this by undertaking measurements in a karst catchment in China. This field location is key to the research as there is much known about C loss by weathering and how different land use in the catchment (e.g. bare rock vs. paddy soils) affects the weathering process. In the first year of the research we will undertake fieldwork to measure CO2 efflux from springs and surface waters, ensuring we capture natural variation in efflux due to differences in river flow and seasonal temperature. In year 2 based on our detailed understanding of the catchment controls on CO2 efflux, we will use specialised tracers of the source of the C (isotopes) to quantify how much C in the CO2 degassed comes from the different sources. With this knowledge we will produce a quantitative process-based model to estimate CO2 efflux, that relies on descriptors of catchment and river characteristics. Finally we will test this model in other catchments to assess how well it describes more widely CO2 efflux from karst drainage systems, and from this testing refine the model / identify how it can be improved.The model is important as it will support up-scaling of CO2 efflux from karst drainage systems and this information is valuable to those modelling the global C cycle and trying to understand how changes in atmospheric CO2 concentration are affected by fluxes to the atmosphere from the Earth's surface.

岩溶景观覆盖了地球陆地表面的很大一部分：约12%，它们代表了陆地上重要的C储存，也被认为在化学风化过程中通过消耗大气CO2在气候调节中发挥重要作用。然而，如果我们不知道排出喀斯特地貌的河流如何有效地将风化的C以CO2的形式重新释放到大气中，我们就无法确定这个汇的有效性。此外，尽管有大量研究表明风化喀斯特系统中带走了多少碳，但研究人员尚未通过直接测量来量化从河流返回大气的碳。我们建议测量岩溶系统中河流的CO2脱气，并使用化学示踪剂，可以区分河流中不同的碳源，量化有多少C来自不同的来源，以及这些贡献如何随着不同的土地利用变化而变化，或者随着季节和河流流量的变化。我们将在中国的一个喀斯特流域进行测量。这个实地位置是研究的关键，因为人们对风化造成的碳损失以及集水区不同的土地利用方式（例如裸岩与水稻土）如何影响风化过程有很多了解。在研究的第一年，我们将进行实地考察，以测量泉水和地表沃茨的二氧化碳排放量，确保我们捕捉到由于河流流量和季节性温度差异造成的排放量的自然变化。在第2年，基于我们对CO2排放的集水控制的详细了解，我们将使用C（同位素）来源的专门示踪剂来量化脱气CO2中有多少C来自不同来源。有了这些知识，我们将产生一个定量的基于过程的模型来估计CO2排放量，依赖于集水区和河流特征的描述符。最后，我们将在其他集水区测试该模型，以评估它如何更广泛地描述岩溶排水系统的CO2排放，并从该测试中完善模型/确定如何改进模型。模型很重要，因为它将支持-岩溶排水系统中CO2排放量的缩放，这一信息对那些模拟全球C循环和试图了解大气CO2变化的人很有价值。浓度受从地球表面到大气的通量的影响。