Fluxes of soot black carbon to South Atlantic sediments

• Published in: Global biogeochemical cycles Vol. 23; no. 1; pp. GB1015 - n/a
• Main Authors: Lohmann, Rainer, Bollinger, Kevyn, Cantwell, Mark, Feichter, Johann, Fischer-Bruns, Irene, Zabel, Matthias
• Format: Journal Article
• Language: English
• Published: Washington, DC American Geophysical Union 01-03-2009; Blackwell Publishing Ltd
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biogeochemical cycles, processes, and modeling; Biogeosciences; Biological and medical sciences; Biosphere/atmosphere interactions; black carbon; Earth sciences; Earth, ocean, space; Exact sciences and technology; flux; Fundamental and applied biological sciences. Psychology; General aspects; Geochemistry; Marine; sediment; Sedimentary geochemistry; Stable isotope geochemistry; Synecology; South America; Congo River; Atlantic Ocean; Africa; South Atlantic; Amazon River; Central Africa; Brazil, Amazon R. basin; AS, South Atlantic; Africa, Congo R; flux; black carbon; sediment; atmosphere; Burned ground; Terrestrial environment; models; mass balance; isotope ratios; aerosols; simulation; concentration; global; Atmospheric deposition; climate; Deep water; Polycyclic aromatic compound; polycyclic aromatic hydrocarbons; sedimentation rates; atmospheric deposits; wood; charcoal; Ratio; organic carbon; sediments
• ISSN: 0886-6236; 1944-9224
• DOI: 10.1029/2008GB003253

Deep sea sediment samples from the South Atlantic Ocean were analyzed for soot black carbon (BC), total organic carbon (TOC), stable carbon isotope ratios (δ13C), and polycyclic aromatic hydrocarbons (PAHs). Soot BC was present at low concentrations (0.04–0.17% dry weight), but accounted for 3–35% of TOC. Fluxes of soot BC were calculated on the basis of known sedimentation rates and ranged from 0.5 to 7.8 μg cm−2 a−1, with higher fluxes near Africa compared to South America. Values of δ13C indicated a marine origin for the organic carbon but terrestrial sources for the soot BC. PAH ratios implied a pyrogenic origin for most samples and possibly a predominance of traffic emissions over wood burning off the African coast. A coupled ocean‐atmosphere‐aerosol‐climate model was used to determine fluxes of BC from 1860 to 2000 to the South Atlantic. Model simulation and measurements both yielded higher soot BC fluxes off the African coast and lower fluxes off the South American coast; however, measured sedimentary soot BC fluxes exceeded simulated values by ∼1 μg cm−2 a−1 on average (within a factor of 2–4). For the sediments off the African coast, soot BC delivery from the Congo River could possibly explain the higher flux rates, but no elevated soot BC fluxes were detected in the Amazon River basin. In total, fluxes of soot BC to the South Atlantic were ∼480–700 Gg a−1 in deep sea sediments. Our results suggest that attempts to construct a global mass balance of BC should include estimates of the atmospheric deposition of BC.