A sedimentary record of the deposition of heavy metals and magnetic oxides in the Loch Dee basin, Galloway, Scotland, since c. AD 1500

Abstract

Geochemical analyses of a 210Pb dated piston core from Loch Dee have highlighted trends of increased Pb and Cu deposition within the catchment as early as AD 1500, probably as a consequence of local mining and smelting activity. More marked atmospheric pollutant deposition appears to have occurred in association with European industrialization after c. 1840, causing a conspicuous enhancement of Pb, Zn, Cu and magnetically detectable Fe oxide concentrations in the uppermost 8 cm of sediment. The co-variability of these contaminants through the surficial sediment suggests that they emanate from a common industrial process and the presence of magnetic oxides in cenospheric particulates implicates thermal power generation plant as a principal pollutant source. This interpretation is further supported by the temporal comparability of trace metal/magnetic oxide influxes at Loch Dee and documented records regarding European fossil fuel combustion levels over the past 150 years. The reduced heavy metal concentrations recorded in sediments deposited during the last decade may accurately chronicle falling deposition during this period, but could also reflect an increase in the efficiency with which metals have been leached from the surficial sediment as the surface waters have acidified. The accordance between the post-industrial record of sedimentary pollutant incorpora tion at Loch Dee and temporal adjustments to the diatom flora of several Galloway lochs is consistent with claims that recent acidification in the region has been a direct response to hydrocarbon-derived atmospheric deposition.