Black carbon in deep-sea sediments

Black carbon (BC) enters the ocean through aerosol and river deposition. BC makes up 12 to 31 percent of the sedimentary organic carbon (SOC) at two deep ocean sites, and it is 2400 to 13,900 carbon-14 years older than non-BC SOC deposited concurrently. BC is likely older because it is stored in an intermediate reservoir before sedimentary deposition. Possible intermediate pools are oceanic dissolved organic carbon (DOC) and terrestrial soils. If DOC is the intermediate reservoir, then BC is 4 to 22 percent of the DOC pool. If soils are the intermediate reservoir, then the importance of riverine carbon in the ocean carbon cycle has been underestimated. Black carbon is a chemically heteroge-neous, biologically refractory class of carbon compounds produced during biomass burn-ing and fossil fuel combustion. Estimates of modern BC production are 50 to 260 tera-grams of carbon per year (Tg C/year) from biomass burning (1) and 12 to 24 Tg C/yea