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Coal fly ash is a major carbon flux in the Chang Jiang (Yangtze River) basin.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2021 May 25; Vol. 118 (21). - Publication Year :
- 2021
-
Abstract
- Fly ash-the residuum of coal burning-contains a considerable amount of fossilized particulate organic carbon (FOC <subscript>ash</subscript> ) that remains after high-temperature combustion. Fly ash leaks into natural environments and participates in the contemporary carbon cycle, but its reactivity and flux remained poorly understood. We characterized FOC <subscript>ash</subscript> in the Chang Jiang (Yangtze River) basin, China, and quantified the riverine FOC <subscript>ash</subscript> fluxes. Using Raman spectral analysis, ramped pyrolysis oxidation, and chemical oxidation, we found that FOC <subscript>ash</subscript> is highly recalcitrant and unreactive, whereas shale-derived FOC (FOC <subscript>rock</subscript> ) was much more labile and easily oxidized. By combining mass balance calculations and other estimates of fly ash input to rivers, we estimated that the flux of FOC <subscript>ash</subscript> carried by the Chang Jiang was 0.21 to 0.42 Mt C⋅y <superscript>-1</superscript> in 2007 to 2008-an amount equivalent to 37 to 72% of the total riverine FOC export. We attributed such high flux to the combination of increasing coal combustion that enhances FOC <subscript>ash</subscript> production and the massive construction of dams in the basin that reduces the flux of FOC <subscript>rock</subscript> eroded from upstream mountainous areas. Using global ash data, a first-order estimate suggests that FOC <subscript>ash</subscript> makes up to 16% of the present-day global riverine FOC flux to the oceans. This reflects a substantial impact of anthropogenic activities on the fluxes and burial of fossil organic carbon that has been made less reactive than the rocks from which it was derived.<br />Competing Interests: The authors declare no competing interest.
Details
- Language :
- English
- ISSN :
- 1091-6490
- Volume :
- 118
- Issue :
- 21
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 34001595
- Full Text :
- https://doi.org/10.1073/pnas.1921544118