Concentration-discharge relationships of dissolved rhenium in Alpine catchments reveal its use as a tracer of oxidative weathering
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Abstract
Oxidative weathering of sedimentary rocks plays an important role in the global carbon cycle. Rhenium (Re) has been proposed as a tracer of rock organic carbon (OCpetro) oxidation. However, the sources of Re and its mobilization by hydrological processes remain poorly constrained. Here we examine dissolved Re as a function of water discharge, using samples collected from three alpine catchments that drain sedimentary rocks in Switzerland (Erlenbach, Vogelbach) and Colorado, USA (East River). The Swiss catchments reveal a higher Re flux in the catchment with higher erosion rates, but have similar [Re]/[Na+] and [Re]/[SO42-] ratios, which indicate a dominance of Re from OCpetro. Despite differences in rock type and hydro-climatic setting, the three catchments have a positive correlation between river water [Re]/[Na+] and [Re]/[SO42-] and water discharge. We propose that this reflects preferential routing of Re from a near-surface, oxidative weathering zone. The observations support the use of Re as a proxy to trace rock-organic carbon oxidation, and suggest it may be a hydrological tracer of vadose zone processes. We apply the Re proxy, and estimate CO2 release by OCpetro oxidation of 5.7 +6.6/-2.0 tC km-2 yr-1 for the Erlenbach. The overall weathering intensity was ∼40%, meaning that the corresponding export of un-weathered OCpetro in river sediments is large, and the findings call for more measurements of OCpetro oxidation in mountains and rivers as thet cross floodplains.
Publication type | Article |
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Publication Subtype | Journal Article |
Title | Concentration-discharge relationships of dissolved rhenium in Alpine catchments reveal its use as a tracer of oxidative weathering |
Series title | Water Resources Research |
DOI | 10.1029/2021WR029844 |
Volume | 57 |
Issue | 11 |
Year Published | 2021 |
Language | English |
Publisher | American Geophysical Union |
Contributing office(s) | Geosciences and Environmental Change Science Center |
Description | e2021WR029844, 18 p. |
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