Fate of atmospherically deposited polycyclic aromatic hydrocarbons (PAHs) in Chesapeake Bay.

Abstract

Factors controlling polycyclic aromatic hydrocarbon (PAH) distributions in southern Chesapeake Bay surface sediments were investigated with samples collected seasonally from five sites. Principal components analysis (PCA) suggests unique sources (combustion vs petroleum) and partitioning differences (volatile vs particle reactive) among PAHs, but a common mode of entry for these contaminants to Chesapeake Bay sediments. The fractional concentrations of all PAHs in Bay sediments, with the exception of perylene, were positively correlated with their atmospheric dry deposition fluxes (Fdry) to the Bay indicating that atmospheric deposition of aerosol-bound PAHs to the watershed controls their influx to Bay sediments. Overall, PAH concentrations in Chesapeake Bay sediments were well explained by a multiple-regression model (r2 = 0.88, p = 0.0001) with Fdry and sediment total organic carbon (TOC) content explaining most of the variance (57% and 43%, respectively). However, for many PAHs gas exchange across the air-water interface is of similar or greater magnitude even when Fdry is scaled to the watershed surface area. The fate of PAHs input to the Bay from gas deposition was determined to be uptake and metabolism within the aquatic food web rather than deposition to sediments.