Department of Earth System Science

Small mountainous rivers (SMR) export globally significant quantities of particulate organic carbon (POC) to the oceans, the composition of which may be distinct from POC delivered by major world rivers. To better constrain the controls on the Δ¹⁴C signatures of POC suspended in SMR, we examined the temporal variability of Δ¹⁴C and δ¹³C of POC suspended in the Santa Clara River, a SMR in California, USA. Our data suggest mixing of bedrock and contemporary soil, which can be applied to other SMR in contrasting climate zones and with varying land cover. The data also suggest that chemical denudation is incomplete, but effective to the point that only the most recalcitrant moieties of the parent POC are exported. We further propose sediment yield as a potentially useful proxy for the Δ¹⁴C of riverine POC. A preliminary analysis of the existing data for a spectrum of rivers supports this hypothesis.