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Decadal carbon discharge by a mountain stream is dominated by coarse organic matter

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Turowski, Jens M 
Hilton, Robert G 
Sparkes, Robert 


Rapid erosion in mountain forests results in high rates of biospheric particulate organic carbon (POC) export by rivers, which can contribute to atmospheric carbon dioxide drawdown. However, coarse POC (CPOC) carried by particles larger than ~1 mm is rarely quantified. In a forested pre-Alpine catchment, we measured CPOC transport rates and found that they increase more rapidly with water discharge than fine POC (<1mm) and dissolved organic carbon (DOC). As a result, decadal estimates of CPOC yield of 12.3±1.9 tC km⁻²yr⁻¹ are higher than for fine POC and DOC, even when excluding 4 extreme flood events. When including these floods, CPOC dominates organic carbon discharge (~80%). Most CPOC (69%) was water-logged and denser than water, suggesting CPOC has the potential to contribute to long-term sedimentary burial. Global fluxes remain poorly constrained, but if the transport behavior of CPOC shown here is common to other mountain streams and rivers then neglecting CPOC discharge could lead to a large underestimation of the global transfer of biospheric POC from land to ocean.


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37 Earth Sciences, 3709 Physical Geography and Environmental Geoscience, 3701 Atmospheric Sciences, 3703 Geochemistry, 15 Life on Land

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Geological Society of America
This study was supported by SNF grant 200021_124634/1, EPSRC grants EP/P502365/1 and EP/P504120/1, and WSL.