River discharge influences on particulate organic carbon age structure in the Mississippi/Atchafalaya River System

摘要: [1] Applying ramped pyrolysis radiocarbon analysis to suspended river sediments, we generate (14C) age spectra for particulate organic carbon (POC) from the lower Mississippi-Atchafalaya River system (MARS) better understand a major system's role in transport. Ramped 14C generates distributions of bulk based on thermochemical stability different components. Our results indicate higher proportions older material POC during discharge. Ages increase throughout high-discharge spectra, indicating that no single component is responsible overall increases observed. Instead, contributed across spectrum and unrelated increased bedload suspension. In this comparison 2 spring discharges, less than half transported discharge 1000 years age, constraining MARS as flux atmospheric CO2 toward longer-term sedimentary sinks Mississippi delta Gulf Mexico. The suggest delta-building processes benefit disproportionately high events carrying larger amounts sediment because these involve both proportion millennially-aged floodplain exchange potentially petrogenic (30-530% increase). Overall, an internally consistent picture PO14C emerges, differences space time are small compared range ages sources such large basin.