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Microbial oxidation of lithospheric organic carbon in rapidly eroding tropical mountain soils

2018; American Association for the Advancement of Science; Volume: 360; Issue: 6385 Linguagem: Inglês

10.1126/science.aao6463

1095-9203

Jordon Hemingway, Robert Hilton, Niels Hovius, Timothy I. Eglinton, Negar Haghipour, Lukas Wacker, Meng-Chiang Chen, Valier Galy,

Hydrocarbon exploration and reservoir analysis

Lithospheric organic carbon ("petrogenic"; OCpetro) is oxidized during exhumation and subsequent erosion of mountain ranges. This process is a considerable source of carbon dioxide (CO2) to the atmosphere over geologic time scales, but the mechanisms that govern oxidation rates in mountain landscapes are poorly constrained. We demonstrate that, on average, 67 ± 11% of the OCpetro initially present in bedrock exhumed from the tropical, rapidly eroding Central Range of Taiwan is oxidized in soils, leading to CO2 emissions of 6.1 to 18.6 metric tons of carbon per square kilometer per year. The molecular and isotopic evolution of bulk OC and lipid biomarkers during soil formation reveals that OCpetro remineralization is microbially mediated. Rapid oxidation in mountain soils drives CO2 emission fluxes that increase with erosion rate, thereby counteracting CO2 drawdown by silicate weathering and biospheric OC burial.