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

碳由水从陆地生态系统通过碳排放通量输送到淡水水生生态系统。碳排放通量的研究还涉及考虑碳随后向下游的输送，以及通过从水面排放二氧化碳(CO2)或甲烷(CH4)向大气中损失的碳。加强我们对生物圈、水圈和大气之间的碳排放通量的了解，对于辨别人类活动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。它还考察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，这些通量对解决流域规模的碳平衡非常重要，并有助于我们对碳和水相互作用的基于过程的知识。在这样做的同时，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可移植到该计划之外，从而显著推动生态水文学领域的发展。我们的中心假设是，通过水运输的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。针对我们评估天然和人类影响流域中碳和水相互作用的长期目标，提出了四项研究来解决这一假说。[A]评估地下水中溶解二氧化碳的通量与流域尺度对二氧化碳产生和传输的控制的关系；[B]根据土壤、地下水和地表水中溶解有机碳(DOC)的浓度和特征来表征溶解有机碳(DOC)；[C]使用两种新的方法评估对地表水二氧化碳和CH4排放的物理控制：一种是针对源流中的流动水，另一种是针对湿地环境中的静止水；[D]调查从干扰中恢复的流域中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，以评估碳是否可能向下游输送或通过逃避水面释放到大气中。我们对河流附近地下水中溶解的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DOC的反应性和生物利用度来表征DOC的质量，以便(I)表征陆生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与氯或溴反应产生的环境污染物。THMS对人类健康构成威胁，本研究中将要研究的生态水文过程似乎在DOC的传输中起着关键作用，具有很高的THM形成潜力。拟议的学习计划包括在理科、硕士、博士和PDF级别对高素质人才的培训，并为适应新兴的“大数据”时代的科学创新提供机会。培训将涉及(1)环境传感器的新用途、数据管理和时间序列分析，以及(2)指导和科学交流方面的专业发展。

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.