Inefficient burial of terrestrial organic carbon in deltas

The world’s deltas are estimated to store ~58 Tg of terrestrial organic carbon (OCterr) annually, indicating their significant role in the global carbon cycle and atmospheric CO2. However, previous studies simply used a proto burial efficiency in the top layer of delta sediments to represent the OCterr burial efficiency in the whole delta, thus neglecting the effects of OCterr degradation after initial burial on the long-term OCterr burial efficiency in deltas.
Here, we used a novel method to quantify sediment budgets and ages from the subaqueous Yellow River Delta. We demonstrate that different sediment pathways together with OCterr degradation result in a substantially, at least 50%, lower multi-decadal net OCterr burial efficiency than previous estimates. These novel results shed insights into the influence of sediment dynamics and OCterr degradation on the long-term OCterr burial. We propose considering time-scale and sediment pathway-dependent heterogeneity of OCterr burial in future studies. We therefore believe that the budget of OCterr buried in global deltas is currently overestimated and call for a re-visit to these budgets.
Our data include ages, physical and chemical characteristics of surface and core sediments collected from the subaqueous Yellow River delta. Also included are the budgets of sediment delivery by the Yellow River, sediment deposition and removal in the subaqueous delta over the past decades.