Polycyclic aromatic hydrocarbons in Massachusetts Bay sediment: Diagnostics, accumulation, and source apportionment

The aim of this research was to discretely characterize sources of environmental polycyclic aromatic hydrocarbons (PAH) and to quantitatively describe the origins of PAH measured in sediment. Increases in PAH accumulation to Massachusetts Bay sediment since the mid-1800's were determined a direct function of the increased petroleum consumption. Temporally, significant increases (p < 0.001) in the MP/P ratio and decreases (p < 0.01) in the fractional abundance of benzofluoranthenes (&phis;_BFs) support an increase in petroleum combustion input. Recent sediments showed a significant increase in coronene (p < 0.001) and decreased &phis;_IDP (p < 0.05), following increased motor vehicle use. Focus correction reduced the spatial variability in accumulation (35 to 7440 ng*cm−2*y−1 ) to yield regional groupings. These results corresponded to a principal components analysis (PCA) model composed of sediment PAH diagnostic ratios and argues that differential accumulation is source related. Additional PAH measurements were made in three sources: Boston Harbor, Merrimack River, and atmospheric deposition. Reconstructed sediment PAH distributions were comparable to those measured (R2 = 0.56 to 0.96). PAH input to Western, Southern Massachusetts, and Cape Cod Bays was dominated by Boston Harbor (55% to 96%) and minimal for the Merrimack River (1% to 16%). A gradual increase in the contribution from atmospheric deposition followed increased distance from the harbor using a model composed of the PAH diagnostic ratios (18% to 36%). The Gulf of Maine location was clearly dominated by input through atmospheric deposition (59%), with lesser contribution from the harbor (36%). Linear alkylbenzenes (LAB) were also used to apportion sewage derived PAH to sediment. Total PAH contribution was <3% at each sediment. Comparisons with a more conservative sewage tracer, Clostridium perfringens, indicated losses of LAB occurred during transport. Internal/external (I/E) ratios determined that microbial degradation accounted for between 10% and 20% of the loss. PCA revealed a component that indicated preferential changes in homologue distribution were based on the alkyl chain length, mainly through desorption of all LAB homologues, most notably the shorter alkyl chains.