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Sulfur isotopes in rivers: Insights into global weathering budgets, pyrite oxidation, and the modern sulfur cycle

Burke, Andrea and Present, Theodore M. and Paris, Guillaume and Rae, Emily C. M. and Sandilands, Brodie H. and Gaillardet, Jérôme and Peucker-Ehrenbrink, Bernhard and Fischer, Woodward W. and McClelland, James W. and Spencer, Robert G. M. and Voss, Britta M. and Adkins, Jess F. (2018) Sulfur isotopes in rivers: Insights into global weathering budgets, pyrite oxidation, and the modern sulfur cycle. Earth and Planetary Science Letters, 496 . pp. 168-177. ISSN 0012-821X.

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The biogeochemical sulfur cycle is intimately linked to the cycles of carbon, iron, and oxygen, and plays an important role in global climate via weathering reactions and aerosols. However, many aspects of the modern budget of the global sulfur cycle are not fully understood. We present new δ^(34)S measurements on sulfate from more than 160 river samples from different geographical and climatic regions—more than 46% of the world's freshwater flux to the ocean is accounted for in this estimate of the global riverine sulfur isotope budget. These measurements include major rivers and their tributaries, as well as time series, and are combined with previously published data to estimate the modern flux-weighted global riverine δ^(34)S as 4.4 ± 4.5‰ (V-CDT), and 4.8 ± 4.9‰ when the most polluted rivers are excluded. The sulfur isotope data, when combined with major anion and cation concentrations, allow us to tease apart the relative contributions of different processes to the modern riverine sulfur budget, resulting in new estimates of the flux of riverine sulfate due to the oxidative weathering of pyrites (1.3 ± 0.2 Tmol S/y) and the weathering of sedimentary sulfate minerals (1.5 ± 0.2 Tmol S/y). These data indicate that previous estimates of the global oxidative weathering of pyrite have been too low by a factor of two. As pyrite oxidation coupled to carbonate weathering can act as a source of CO_2 to the atmosphere, this global pyrite weathering budget implies that the global CO_2 weathering sink is overestimated. Furthermore, the large range of sulfur isotope ratios in modern rivers indicates that secular changes in the lithologies exposed to weathering through time could play a major role in driving past variations in the δ^(34)S value of seawater.

Item Type:Article
Related URLs:
URLURL TypeDescription
Burke, Andrea0000-0002-3754-1498
Paris, Guillaume0000-0001-8368-1224
Peucker-Ehrenbrink, Bernhard0000-0002-3819-992X
Fischer, Woodward W.0000-0002-8836-3054
Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2018 Elsevier B.V. Received 6 November 2017, Revised 13 May 2018, Accepted 14 May 2018, Available online 6 June 2018. This research was funded by a Foster and Coco Stanback postdoctoral fellowship and a Marie Curie Career Integration Grant (CIG14-631752) to AB. JFA acknowledges the support of NSF-OCE grant 1340174 and NSF-EAR grant 1349858. WF acknowledges the support of a grant from the David and Lucile Packard Foundation.
Funding AgencyGrant Number
Foster and Coco Stanback Postdoctoral FellowshipUNSPECIFIED
Marie Curie FellowshipCIG14-631752
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:sulfur; rivers; weathering; pyrite
Record Number:CaltechAUTHORS:20180620-110745106
Persistent URL:
Official Citation:Andrea Burke, Theodore M. Present, Guillaume Paris, Emily C.M. Rae, Brodie H. Sandilands, Jérôme Gaillardet, Bernhard Peucker-Ehrenbrink, Woodward W. Fischer, James W. McClelland, Robert G.M. Spencer, Britta M. Voss, Jess F. Adkins, Sulfur isotopes in rivers: Insights into global weathering budgets, pyrite oxidation, and the modern sulfur cycle, Earth and Planetary Science Letters, Volume 496, 2018, Pages 168-177, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87259
Deposited By: Tony Diaz
Deposited On:20 Jun 2018 18:49
Last Modified:09 Mar 2020 13:19

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