Source Assessment and Sedimentary Record of Pyrolytic Polycyclic Aromatic Hydrocarbons in Lake Bled (NW Slovenia)

Gregor Muri1,2,* and Stuart G. Wakeham2

1 Environmental Agency of the Republic of Slovenia, Vojkova 1b, 1000 Ljubljana, Slovenia
2 Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, USA
* Corresponding author: E-mail:
Tel: +386 1 478 4556; fax: +386 1 478 4050

Polycyclic aromatic hydrocarbons (PAH) were determined in two sediment cores in urban Lake Bled (NW Slovenia). In
surface sediments of the deep western basin, the total PAH concentration was 1150 ng g–1 dry weight (dw), whereas in
shallower, nearshore Zaka Bay the PAH concentration was 1900 ng g–1 dw. Four- to six-ring PAH were the most abundant
compounds, suggesting that most PAH in Lake Bled sediments are pyrogenic, probably of coal combustion origin
as inferred by several PAH ratios. Uniform compositions for pyrogenic PAH were observed downcore in both cores. The
highest concentrations of PAH in Lake Bled sediments occurred in sediments deposited in mid 20th Century (ca. 1945),
leading to organic carbon (OC) normalized concentrations of 120 μg PAH g–1 OC, compared to contemporary concentrations
of 21 and 30 μg g–1 OC in the western basin and Zaka Bay, respectively. Using PAH concentrations and sedimentation
rates, we estimate that present-day PAH fluxes are 630 and 1800 μg m–2 yr–1, respectively. These contemporary
PAH fluxes to Lake Bled were still 3–4 fold higher than in nearby but remote alpine Lake Planina, confirming elevated
PAH contamination in the urban setting.

Keywords: PAH; black carbon; combustion; Pollution