Ecohydrological Controls on Carbon Drainage Fluxes in Natural and Human-Impacted Watersheds

碳通过碳排放通量由水从陆地生态系统输送到淡水水生生态系统。碳排放通量的研究还包括考虑随后的下游碳运输，以及通过从水面排放二氧化碳（CO2）或甲烷（CH4）向大气中的碳损失。提高我们对生物圈、水圈和大气之间碳排放通量的认识，对于识别人类对水和碳循环以及气候系统的影响是必要的。我的研究项目主要集中在温带和热带环境中地表水和地下水的原位碳测量。它还研究了控制这些通量的物理过程。我们将研究碳排放通量的关键组成部分，这对解决流域尺度上的碳平衡很重要，并有助于我们基于过程的碳和水相互作用知识。在此过程中，我们还将开发几种分析工具和技术，我们预计这些工具和技术将高度转移到本项目之外，这将大大推进生态水文学领域。我们的中心假设是，水运输碳的形式和通量的变化可以用来评估气候和土地利用变化造成的影响。我们提出了四项研究来解决这一假设，并将其与我们评估自然和人类影响的流域中碳和水的相互作用的长期目标联系起来。[A]评价与流域尺度控制二氧化碳生产和运输有关的地下水溶解二氧化碳通量；[B]土壤、地下水和地表水中溶解有机碳（DOC）的浓度和特征；[C]利用两种新方法评估地表水中CO2和CH4排放的物理控制：一种用于源头溪流中的流动水，另一种用于湿地环境中的静水；[D]研究从干扰中恢复的流域碳排放通量随时间的变化。在我们的研究中，将评估碳排放通量的生物地球化学特征，以评估碳是否可能通过逃避水面而向下游输送或释放到大气中。我们对河流附近地下水中溶解二氧化碳浓度动态的分析代表了一种评估流域生态水文特性的新方法，而对DOC化学特征（称为DOC质量）的研究将允许通过跟踪风暴事件期间的DOC质量来评估流域的生态水文功能。我们将根据其反应性和生物利用度来描述DOC的质量，以便(i)描述陆地DOC对水生生态系统的输入，以及（ii）评估DOC在市政供水中形成消毒副产物如三卤甲烷（THMs）的潜力。THMs是水处理过程中某些形式的DOC与氯或溴发生反应而产生的环境污染物。THM对人类健康构成威胁，本研究项目研究的生态水文过程在DOC的转运中发挥关键作用，THM形成潜力高。拟议的研究项目包括培养理学士、理学硕士、博士和PDF级别的高素质人才，并为适应新兴“大数据”时代的科学创新提供机会。培训将涉及(i)环境传感器的新使用、数据管理和时间序列分析，以及（ii）指导和科学传播方面的专业发展。

Carbon is transported by water from terrestrial ecosystems to freshwater aquatic ecosystems through carbon drainage fluxes. The study of carbon drainage fluxes also involves consideration of subsequent downstream transport of carbon, as well as the loss of carbon to the atmosphere via emissions of carbon dioxide (CO2) or methane (CH4) from the water surface. Improving our understanding of carbon drainage fluxes between the biosphere, hydrosphere and the atmosphere is necessary to discern anthropogenic impacts on the water and carbon cycles, as well as the climate system. My research program focuses on in situ carbon measurements in surface water and groundwater in temperate and tropical environments. It also examines the physical processes that control these fluxes. We will investigate key components of carbon drainage fluxes that are important to resolving the carbon balance at a watershed scale, and which contribute to our process-based knowledge of carbon and water interactions. In doing so, we will also develop several analytical tools and techniques that we anticipate to be highly transferable beyond this program that will significantly advance the field of ecohydrology. Our central hypothesis is that changes in the forms and fluxes of carbon transported by water can be used to evaluate impacts resulting from climatic and land use change. Four studies are proposed to address this hypothesis in relation to our long-term objective of assessing carbon and water interactions in natural and human-impacted watersheds. [A] Evaluate groundwater fluxes of dissolved CO2 in relation to watershed-scale controls on CO2 production and transport; [B] Characterize dissolved organic carbon (DOC) in terms of DOC concentration and characteristics in soils, groundwater and surface water;[C] Assess physical controls on emissions of CO2 and CH4 from surface water using two novel approaches: one for flowing water in headwater streams, and one for standing water in a wetland environment; [D] Investigate changes in carbon drainage fluxes over time in a watershed recovering from disturbance. In our studies, the biogeochemical characteristics of carbon drainage fluxes will be evaluated to assess if the carbon is likely to be transported downstream or released to the atmosphere via evasion from the water surface. Our analysis of dissolved CO2 concentration dynamics in groundwater adjacent to streams represents a novel approach for assessing the ecohydrological properties of a watershed, while research on DOC chemical characteristics (termed DOC quality) will allow for an assessment of the ecohydrological functioning of a watershed by tracking DOC quality during storm events. We will characterize DOC quality in terms of its reactivity and bioavailability in order to (i) characterize terrestrial DOC inputs to aquatic ecosystems, and (ii) evaluate the potential for DOC to form disinfection byproducts such as trihalomethanes (THMs) in municipal water supplies. THMs are environmental pollutants resulting from reactions between some forms of DOC and chlorine or bromine during water treatment. THMs pose risks to human health, and the ecohydrological processes to be studied in this program of research appear to play a key role in the transport of DOC with a high THM formation potential.The proposed program of study incorporates training of highly qualified personnel at BSc, MSc, PhD and PDF levels, and provides opportunities for scientific innovation appropriate for the emerging era of “big data”. Training will involve (i) novel use of environmental sensors, data management and time series analysis, and (ii) professional development in mentoring and science communication.