Black carbon in marine particulate organic carbon: Inputs and cycling of highly recalcitrant organic carbon in the Gulf of Maine |
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Authors: | D Xanat Flores-Cervantes Desiree L Plata John K MacFarlane Christopher M Reddy Philip M Gschwend |
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Institution: | aR.M. Parsons Laboratory, MIT 48-413, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;bDepartment of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02543, USA |
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Abstract: | To increase our understanding of the roles of black carbon (BC), a highly sorptive and recalcitrant material, we measured BC concentrations and fluxes in marine particulate organic carbon (POC) out of the water column in the Gulf of Maine (GoM), a representative coastal area downwind of important BC sources of the Northeastern United States. Concentrations ranged from < 0.1 to 16 μg/L in the spring and late summer, typically contributing between 1 and 20% of the POC. Water-column export fluxes were near 10 gBC/m2∙yr. These observations suggest that (a) up to 50% of the “molecularly uncharacterized” POC in this region's seawater is combustion-derived BC, and (b) the “bioavailabilities” of hydrophobic pollutants like polycyclic aromatic hydrocarbons (PAHs) would be influenced substantially by sorption to BC. The observed BC spatial distributions imply that a large part of the BC was carried offshore by wind and that much of it is accumulated in the coastal sediments. On a global scale, these results suggest the GoM and other coastal areas with similar BC loadings accumulate significant amounts of highly recalcitrant organic carbon that remineralizes on geological time scales in the world's oceans. |
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Keywords: | Black carbon Particulate organic carbon Seawater Gulf of Maine Carbon cycle |
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