Characterization of carbonaceous particles from lake sediments

Abstract

Spheroidal carbonaceous particles produced by high temperature combustion of coal and oil are found in high concentrations in lake sediments from areas of high acid deposition. The sediment record of these particles showing the onset of industrialisation correlates well with the record of acidification as indicated by diatom analysis.

To find sources of the atmospheric deposition affecting a lake and its catchment, characterisation of the carbonaceous particles is necessary. A reference data set of particle chemistries from coal and oil power stations was produced using EDS generated data of 17 elements. Using multivariate statistical techniques, the most important elements for the coal/oil separation were identified and incorporated into a linear discriminant function which allocated fuel type with > 97% accuracy.

Application of this technique to surface sediments in Scotland shows the influence of oil burning from outside the region, higher areas located on the east coast and in the south-west of the country. When applied to a full sediment core, the history of coal and oil combustion affecting the lake is seen and correlates well with known coal and oil consumption figures. Consequently this method could be used to add extra dating levels to sediment cores.

The technique has been extended to include peat particles and could potentially be used on those from brown coal, lignite and oil shale combustion.