22
January 2004
Biogeochemistry: Doing the rounds
Black carbon is a significant contributor to the global carbon budget. It is produced by combustion and most of it is ultimately deposited in marine sediments. Or at least that has been the assumption. A new study of pre-industrial marine and terrestrial sediments paints a rather different picture. Isotopic analysis reveals a graphitic carbon fraction with almost no radiocarbon remaining, suggesting that it is graphite weathered from rocks. This 'fossil' carbon is captured in a semipermanent loop in the carbon cycle and its presence in marine sediments has probably led to significant overestimates of burial of combustion-derived black carbon and biased dating of sedimentary organic carbon.
Reburial of fossil organic carbon in marine
sediments
ANGELA F. DICKENS, YVES G�LINAS, CAROLINE A. MASIELLO,
STUART WAKEHAM & JOHN I. HEDGES
Nature 427, 336–339 (2004); doi:10.1038/nature02299
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Biogeochemistry: Carbon budget in the black
MICHAEL W. I. SCHMIDT
A significant fraction of a common organic component of marine sediments
has an unexpected source, providing a fresh context for studies of the
global carbon cycle in oceanic and terrestrial settings.
Nature 427, 305–307 (2004); doi:10.1038/427305a
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