5 Environmental Geochemistry and Health Impacts (Posters)

This session welcomes research on contaminant occurrence, fate and transport, and impacts on human and environmental health. Interdisciplinary contributions with implications for environmental remediation and natural resources management are encouraged.

Monday, 18 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Controls on the Spatial and Temporal Patterns of Organic Carbon Delivery and Burial within an Arid River Reservoir

Paper number: 5-5
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The carbon cycle is a prominent climate driver, but the role of Earth surface processes in this cycle remain poorly constrained, particularly in arid regions. In dry regions, rivers are perhaps the most dynamic components of the landscape, transporting organic carbon (OC) from forested uplands through dry lowlands. Because arid river systems are heavily managed by humans, the fate of this OC is highly dependent on the carbon cycling dynamics within floodplains and in reservoirs behind dams. While past research has worked to resolve the magnitude of OC export from large river systems to the global oceans, few studies have worked to understand and quantify the cycling of carbon that does not reach the ocean, such as the material trapped behind dams. The fate of carbon behind dams remains a key knowledge gap that limits our ability to accurately quantify carbon fluxes in managed river systems. We aim to understand how dams impact the transport, storage, and cycling of OC in arid river systems through a detailed study of Elephant Butte Reservoir (EBR) in southern New Mexico, where the Rio Grande has delivered large volumes of sediment for more than a century. We collected and analyzed a time-series of suspended sediment samples from the Rio Grande to constrain the temporal variations in the flux and composition of particulate organic carbon (POC) delivered to EBR. We collected sediment cores from locations across subaqueous and exposed reservoir bed during a period of reservoir drawdown to quantify the POC burial efficiency and identify whether fluvial POC is preserved or oxidized within the reservoir sediments. We employ elemental and stable isotope analysis in combination with laser diffraction particle size analyses to determine the efficiency of POC burial in reservoir sediments. Preliminary results suggest that autochthonous production of OC within the reservoir, combined with storm-driven pulses of fluvial sediment deposition during the North American Monsoon season drive efficient POC burial in the subaqueous reservoir. Comparatively, we find very little POC in the exposed reservoir bed, suggesting that drawdown during the ongoing drought period drives POC oxidation. The results of this work will improve our understanding of the role of arid river systems and dams in the global carbon cycle. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410524

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