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

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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.