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Spheroidal Carbonaceous Particles in a Virginia Mill Pond Provide a Record of Local and Regional Coal Combustion
Cahoon, Kayla
Cahoon, Kayla
Abstract
Spheroidal carbonaceous particles (SCP), a constituent of coal fly ash, are a sensitive indicator of local and regional coal combustion archived in lake sediments. Their unique morphology and chemical composition are not replicated by any naturally occurring substance on Earth. SCP accumulation in sediments has also been correlated to accumulation of heavy metals such as Mn, Fe, Ti, and Pb. We reconstructed SCP accumulation in a former mill pond in Williamsburg, VA, Lake Matoaka, and find a bimodal distribution with peaks c. 1790 and c. 1953. We believe that our study is the first to identify SCPs in sediments prior to the early 1800s, making this record unique. Grain size analysis shows a statistically significant difference in grains from the two peaks indicating different fly-ash provenance. The particles first appear in Lake Matoaka in 1734 and steadily increase from 15-300 SCP/gDM peaking in 1790. SCP concentration remains constant at ~100-200 SCP/gDM from c. 1800-1860, when a rapid increase in particle accumulation resumes, increasing abruptly from 500 SCP/gDM in 1860 to >8000 SCP/gDM in 1953. Modern accumulation rates have decreased in response to emission restricting legislation in 1970 but continue to accumulate 1000 SCP/gDM in surface sediments. Trends in SCP accumulation mirror major historical events including prominent socio-political wars and economic depressions.
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Date
2019-05-01
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Geology