Publication Date:
2022-05-25
Description:
Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 496 (2018): 168-177, doi:10.1016/j.epsl.2018.05.022.
Description:
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 δ34S
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 δ34S as 4.4 ± 4.5 ‰ (V-CDT),
and 4.8 ± 4.9 ‰ when the most polluted rivers are excluded. Combined with
major anion and cation concentrations, the sulfur isotope data 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 CO2 to the atmosphere, this global pyrite weathering budget
implies that the global CO2 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 δ34S of seawater.
Description:
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.
Keywords:
Sulfur
;
Rivers
;
Weathering
;
Pyrite
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
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