| dc.description.abstract | Lake Botanisk, a small isolated body of water that was once a part of the moat that surrounded Copenhagen, Denmark, has remained relatively undisturbed for four centuries. Due to this long undisturbed record and restricted watershed, its sediments serve as an excellent historical archive. The concentrations of various polycyclic aromatic hydrocarbons (PAHs), black carbon (BC), mercury (Hg), and lignin were measured in a sediment core from Lake Botanisk to assist with reconstruction of historical events for that region, including combustion associated with changes in fuel sources and industrial activities. Source diagnostic ratios indicate that PAHs were primarily derived from pyrogenic rather than petrogenic sources throughout the core. Marked increases in PAH concentrations during the pre-industrial era (<1860) trace major geopolitical events of that period (e.g. the bombing of Copenhagen by British Navy in late 1700s, and two major fires). The ratio of retene/(retene+chrysene) demonstrates that until ~1860, Copenhagen’s combustion sources were dominated by wood burning. During these years, Hg and lignin concentrations in the lower core were strongly correlated, indicating that the primary vehicle for Hg input into the lake was via organic matter transport. After the lake was isolated from the moat in the early 1870’s, Hg became more strongly correlated with pyrogenic PAHs, indicating that combustion byproducts entering the lake did so via atmospheric deposition. A significant rise in combustion-derived PAHs and BC was observed with the start of the Industrial Revolution, which corresponds to the start of coal imports in Denmark (1860s). The shift to coal consumption starting in 1860 leads to simultaneous increases in pyrogenic PAHs and isomer ratios (benzo[b]fluoranthene/benzo[k]fluoranthene) typical of coal usage. | en |
