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Riverine Export of Aged Carbon Driven by Flow Path Depth and Residence Time
Rebecca T Barnes1, David E Butman2, Henry F Wilson3
1Environmental Program, Colorado College , Colorado Springs, Colorado 80903, United States.
Environmental Science & Technology
|January 10, 2018
Summary
Increased terrestrial carbon flux to rivers includes aged dissolved organic carbon (DOC). Deeper soil and water flow paths, influenced by landscape changes, elevate aged DOC export, impacting riverine carbon processing.
Area of Science:
- Environmental Chemistry
- Geochemistry
- Hydrology
Background:
- Terrestrial carbon flux to rivers has increased, with a portion being aged dissolved organic carbon (DOC).
- Rivers process carbon through storage, export to oceans, or release as CO2.
- Land disturbances alter land cover and hydrology, affecting DOC sources and processing.
Purpose of the Study:
- To investigate the sources of aged DOC in riverine exports.
- To understand the relationship between DOC properties and hydrological/geochemical factors.
Main Methods:
- Analysis of radiocarbon ages, chemical, and spectral properties of DOC.
- Measurement of major ions in rivers across the coterminous U.S. and Arctic.
- Correlation of DOC characteristics with basin hydrology and mineral weathering.
Main Results:
- Aged DOC comprises smaller, microbial degradation products, contrasting with modern DOC's aromatic, high molecular weight nature.
- Aged DOC exports are prevalent in arid basins and during base flow in Arctic rivers.
- Higher proportions of mineral weathering products correlate with aged DOC, suggesting deeper flow paths.
Conclusions:
- Deeper flow paths and longer residence times in soils and water promote the aging of DOC.
- Hydrological changes due to landscape alteration or climate shifts can increase aged DOC export.
- Understanding aged DOC sources is crucial for predicting riverine carbon cycling under environmental change.
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