PARENT SESSION

PW13 Sediment Chemistry
Exhibit Hall
8:00 AM - Wednesday, 12 November 2003

(PW197) Composition and Stable Carbon Isotope Ratio of PAHs in Sediments from the Lake Union, Seattle, WA.

Kim, M¹, Qian, Y¹, Kennicutt II, M¹, Donnelly, K², Barbee, G², ¹ Geochemical and Environmental Research Group, Texas A&M University, College Station, TX, USA² Texas A&M University, College Station, TX, USA

ABSTRACT- Sixty sediment samples of three different years (2000, 2001, and 2002) from the Lake Union in Seattle were analyzed for molecular and stable carbon isotopic compositions of polycyclic aromatic hydrocarbons (PAHs) to characterize their possible sources. Total PAH concentrations ranged from 67.0 to 16,500 g / g of dry sediment with fluoranthene and pyrene being the most abundant PAH components in most of the samples. The spatial distribution of PAHs showed that sediments close to the Gas Works Park, which is the site of a retired coal gasification plant, are highly contaminated with PAHs up to a percent level. Analysis of PAH concentration data and molecular ratios indicated that the PAHs are mostly pyrogenic. Comparison of the data with that from reference sites (Eagle Harbor and Hylebos Waterway) demonstrated that the PAHs in the Lake Union sediments have quite different sources from that of the reference sites. Compound specific isotope analysis using GC/C/IRMS (Gas Chromatography / Combustion / Isotope Ratio Mass Spectrometry) provided clear evidences for the unique source of the PAHs and suggested that the PAHs were likely produced during the coal gasification processes, that lasted for 50 years until 1956.

Key words: polycyclic aromatic hydrocarbons, stable carbon isotope ratio, sediment, source assessment