Sedimentary Records of Spheroidal Carbonaceous Particles from Fossil-Fuel Combustion in Western Lake Ontario

Abstract

Spheroidal carbonaceous particles (SCPs) were quantified in three sediment cores collected from depositional areas in the western basin of Lake Ontario to examine the impact of fossil-fuel combustion on sediment metal concentrations. SCP profiles were similar for the three cores showing the initiation of the SCP record deep in the core, followed by a rapid increase to a sub-surface maximum, and a subsequent decrease towards the sediment surface. Subsurface maximum SCP concentrations ranged from 1.97 to 5.61 × 105 per gram dry matter/gDM. For 210Pb dated cores, dates for the initiation of the SCP record (1850 ± 10 years), the initiation of the rapid rise in SCPs (1880 ± 13 years), and the SCP subsurface maximum (1961 ± 3 years) agree well. The rapid increase in sediment SCPs also agrees well with the US bituminous coal consumption during this same period (1880 to 1980). SCPs in surface sediments decreased between 55 to 83% from the subsurface maximum (1961 to 1996) in these cores while U.S. coal usage continued to increase. SCP decreases were attributed to the increased use and efficiency of particle collection devices by utilities and industry. Lead, Cr, Cu, and Zn showed significant correlations (r2 = 0.63 to 0.94) with SCPs within each respective sediment core. Calculations show that although SCPs are not the major source of anthropogenic metals in Lake Ontario sediments, they may account for between 4 to 55% of the Zn, 1 to 12% of the Cu, 2 to 22% of the Pb and 1 to 18% of the Cr in these sediments.