Aged black carbon in marine sediments and sinking particles

Abstract

We report measurements of oceanic black carbon (BC) to determine the sources of BC to abyssal marine sediments in the northeast Pacific Ocean. We find that the average 14C age of BC is older (by 6200 ± 2200 14C years) than that of the concurrently deposited non-BC sedimentary organic carbon. We investigate sources of aged BC to sediments by measuring a sample of sinking particulate organic carbon (POC) and find that POC may provide the main transport mechanism of BC to sediments. We suggest that aged BC is incorporated into POC from a combination of resuspended sediments and sorption of ancient dissolved organic carbon BC onto POC. Our BC flux estimate represents ~8–16% of the global burial flux of organic carbon to abyssal sediments and constitutes a minimum long-term removal estimate of 6–32% of biomass-derived BC using the present day emission flux.