T267 Innovations in Research of Springs and Other Features at the Groundwater–Surface Water Interface (Posters)

Wednesday, 25 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

USING 13C/12C OF DISSOLVED INORGANIC CARBON AND DISSOLVED ORGANIC CARBON AS TRACERS TO CHARACTERIZE KARST SPRING SYSTEMS OF THE SHIVWITS PLATEAU AT GRAND CANYON NATIONAL PARK, ARIZONA, USA

Paper number: T267-10
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Isotopic analyses for δ13C of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) can provide insight into the carbon cycling of a groundwater system. Dissolved organic carbon in groundwater is sourced from the leeching of organic acids from terrestrial vegetation and humic matter in soil during infiltration of precipitation. The resulting δ13C-DOC of the groundwater retains its terrestrial signature which will vary depending on metabolic pathways in the vegetative cover (C3, C4, or CAM) which can comprise a range in δ13C from ca. -33 to -10 ‰. DIC can be sourced from vegetation and humic matter as well although it can be altered in groundwater systems by processes such as microbial activity and carbonate dissolution. Thus, the δ13C-DIC of a groundwater system can be used as a tracer in order to characterize spring systems as springs that share a groundwater system will show similar fractionation trends in δ13C-DIC resulting from a given flow systems unique microbial biome and preferential dissolution of carbonate strata.

The Shivwits Plateau in western Grand Canyon National Park (GRCA) is relatively unstudied due to difficulty of access and wilderness designation, resulting in difficulty of completing traditional groundwater studies and thus requires a variety of tracer studies to characterize flow patterns. Utilizing δ13C of DIC and DOC in a remote karstic system such as the Shivwits Plateau can provide useful parameters for characterizing springs in either low- or high-resolution sampling. δ13C-DIC analyses have been completed for samples collected during high flow conditions from 14 springs across the Shivwits Plateau showing variation in δ13C-DIC from -13.8 to -6.4 ‰. δ13C-DOC results will be compared with δ13C-DIC and existing vegetation maps to help characterize water sources and flow paths. These methods could be employed in future studies to improve understanding of flow paths and enhance water management practices in Grand Canyon and elsewhere.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-340334

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