A spatial relationship between carbonaceous particles in lake sediments and sulphur deposition

Abstract

Spheroidal carbonaceous particles (SCPs) produced by high temperature combustion of coal and oil are found in significant concentrations in the surface sediments of lakes in 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. The surface sediments from 146 lakes in Scotland, U.K., were analysed for SCPs. The results show a pattern very similar to that of modelled sulphur deposition. However, within a region particle concentrations can vary quite considerably and this is generally assumed to be due to lake and catchment factors. A data set containing SCP concentration, sulphur deposition, lake altitude, area, maximum depth, volume, catchment area, catchment area: lake area ratio, residence time, and annual rainfall for the 146 lakes was compiled. Exploratory analysis of the data set using principal components analysis (PCA) indicated that sulphur deposition, lake size, altitude and annual rainfall were important in explaining SCP concentrations. Stepwise multiple regression confirmed this showing that sulphur deposition explained 32.6% of the variance in the SCP data and altitude, lake area and rainfall, selected sequentially, explained a further 9.8, 3.6 and 2.1%, respectively. We conclude that although there is a clear spatial correlation between SCP deposition and sulphur deposition, the relationship is not sufficiently strong for SCP concentration to be used quantitatively as a predictor of sulphur deposition at a lake site.