M5 PM Marine Environmental Chemistry of Organic Pollutants
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 321-323

(DUN-1117-738102) Historical Anthropogenic Inputs of Black Carbon and Polycyclic Aromatic Hydrocarbons to the Chesapeake Bay Watershed.

Dunn, J¹, Mitra, S², ¹ Binghamton University, Binghamton, NY, USA² Binghamton University, Binghamton, NY, USA

ABSTRACT- Since colonization, the Chesapeake Bay (C. Bay) has been subjected to a suite of anthropogenic impacts. One of the processes, combustion, stands to detrimentally impact C. Bay water quality. A byproduct of combustion is black carbon (BC), the residue remaining after incomplete combustion of biomass or fossil fuels. BC is important in that it co-associates with many organic contaminants, such as polycyclic aromatic hydrocarbons (PAH's). This study focuses on recent and historical BC deposition into the C. Bay, an important coastal ecosystem, using two complementary approaches. In this study, we estimate historical atmospheric emission of BC via development of a BC emissions inventory for the states that comprise the C. Bay watershed. Our model utilizes historical consumption data and BC emission factors derived from literature, both of which are specific to BC fuel source. Results indicate a marked increase of BC influx from 1900 until 1945, followed by an equally marked decline until 2000. Additionally, BC was chemically extracted from sediments throughout a 66 cm box core and a 4.5 m piston core taken from an anoxic deep water site in the mainstem of the C. Bay. BC concentrations were quantified in sequential depth intervals and taken together with sediment mass accumulation rates in order to calculate historical BC depositional flux in the core. Results from the sediment core show BC concentrations ranging from 0.15-0.75 grams BC gdw^-1. BC extracts were also analyzed for their stable carbon isotopic composition (¹³C). The range of ¹³C of the BC throughout the core is from -22.86 to -20.78 per mil, indicating historical variation in BC source. PAHs will be extracted from sediments at several depth intervals in order to delineate BC source.

Key words: Black carbon, Chesapeake Bay, Polycyclic Aromatic Hydrocarbons, emissions inventory