Sedimentary Accumulation of Black Carbon on the East Coast of The United States

Abstract The occurrence, trends and sources of soot black carbon (BC) in coastal sediments are poorly understood, particularly during the Anthropocene. Two sediment cores, covering the last ∼100 years from the US East Coast, off North Carolina and in the Florida Straits, were analyzed for organic carbon (OC), BC fluxes and BC sources. BC fluxes were 0.1 g cm−2 year−1 at both sites and accounted for 8%–22% of total OC. Carbon stable isotope values indicated OC to be of marine origin, while the BC was mostly terrestrially derived, C3‐plant material. Radiocarbon values revealed BC originating mostly from fossil fuels or pre‐aged carbon (fraction modern of 14%–31%) at North Carolina, while in the Florida Strait the BC was mostly derived from biomass burning (fraction modern of 70%–74%), in‐line with continental (NC) or marine (FS) air mass origins. Ratios of polycyclic aromatic hydrocarbons broadly supported different BC sources at the two sites.