WP3 Contamination Source Identification and Apportionment
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(WAL-1117-805648) Seasonal variability in sources and distribution of organic contaminants in the Chesapeake Bay.

Walker, S¹, Boyd, T¹, ¹ Marine Biogeochemistry Section, US Naval Research Laboratory, Washington, DC, USA

ABSTRACT- Seasonal variations in sources of polycyclic aromatic hydrocarbons (PAHs) to the main stem and tributaries of the Chesapeake Bay were investigated during biannual sediment and water column sampling events. While previous investigations have determined general sources of PAHs to the sediments and water column of the mid and lower stem of Chesapeake Bay, seasonal variations have not been previously examined. The following hypotheses were proposed: during the early spring, surface water column PAH sources should be dominated by a combination of atmospheric deposition (combustion derived automotive sources) and runoff e.g. combustion and petrogenic sources, while bottom water will likely be dominated by combustion sources (coal from sediment resuspension and automotive from atmospheric deposition). In the late summer, surface water column PAH sources should be dominated by atmospheric automotive sources; bottom waters should also consist of an automotive atmospheric signal with potential contributions from a historic sediment signal. Based on previous investigations and given the integrative nature of sediments, coal sources should dominate sediment PAH signatures year-round. Sources of PAHs to the Chesapeake Bay will be examined through a combination of techniques, including isomer ratios and multivariate statistics (ie., principal component analysis). Preliminary results indicate that despite the increasing development of the Chesapeake Bay watershed, overall PAH concentrations in the Bay and the mouth of the tributaries are generally low relative to more impacted urban estuaries, ie., Baltimore Harbor, the Anacostia River, and the Elizabeth River. Additionally, biogenic PAHs, specifically perylene, consistently represent a significant component (15-∼50%) of the total resolved PAH concentrations in the main stem and the tributaries, irrespective of season.

Key words: PAHs, sources, Chesapeake Bay