University of Cambridge > > Department of Earth Sciences Seminars (downtown) > Chasing waterfalls: constraining the global sulfur isotopic budget in rivers

Chasing waterfalls: constraining the global sulfur isotopic budget in rivers

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The sulfur cycle has an important influence on global climate, for instance through weathering and aerosols, and is intricately linked to both the carbon and oxygen cycles. However, many aspects of the modern sulfur budget are not well understood. We present new d34S measurements on aqueous sulfate from more than 50 rivers from different geographical and climatic regions. These data were measured by a new MC-ICP-MS method that requires only 10 nmol of sulfate [Paris et al., 2013], with typical isotopic uncertainties of only 0.1‰. Combined with previously published sulfur isotope data, more than 50% of the world’s freshwater flux to the ocean is involved in this estimate of the global riverine sulfur isotopic budget. Combined with major anion and cation data, the sulfur isotope data allows us to tease apart the relative contributions of different processes to the modern sulfur budget, including the oxidative weathering of pyrites, the weathering of sedimentary sulfates, and anthropogenic influences. These data yield important insights into the modern sulfur cycle and the weathering of sulfur bearing minerals, and are first order terms in balancing the modern sulfur isotopic budget. The large range of sulfur isotopic ratios in modern rivers has implications for our intepretation of the past changes in the sulfur isotopic composition of seawater. Secular changes in the lithologies exposed to weathering through time could play a major role in driving the variations in d34S in seawater over the Phanerozoic.

Paris, G., A. L. Sessions, A. V. Subhas, and J. F. Adkins (2013), Chemical Geology, Chemical Geology, 345©, 1–12, doi:10.1016/j.chemgeo.2013.02.022.

Calmels, D., J. Gaillardet, A. Brenot, and C. France-Lanord (2007), Sustained sulfide oxidation by physical erosion processes in the Mackenzie River basin: Climatic perspectives, Geology, 35(11), 1003, doi:10.1130/G24132A.1.

Halevy, I., S. E. Peters, and W. W. Fischer (2012), Sulfate Burial Constraints on the Phanerozoic Sulfur Cycle, Science, 337(6092), 331–334, doi:10.1126/science.1220224.

Turchyn, A.V., E. T. Tipper, A. Galy, J.-K. Lo, M. J. Bickle, Isotope evidence for secondary sulfide precipitation along the Marsyandi River, Nepal, Himalayas, Earth and Planetary Science Letters, Volume 374, 15 July 2013, Pages 36-46, ISSN 0012 -821X,

This talk is part of the Department of Earth Sciences Seminars (downtown) series.

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