Polycyclic aromatic hydrocarbon distribution within lower Hudson River estuarine sediments: Physical mixing vs sediment geochemistry

Sediments and porewaters from two cores, one from the East River, New York and one from Newark Bay, New Jersey, were sampled for polycyclic aromatic hydrocarbons (PAHs) and other geochemical markers including Pb-210 specific activities. Despite what appears to be similar sources of PAHs to sediments within each core as inferred by ratios of alkylated to non-alkylated PAHs and PAH isomer ratios, sediments and associated PAHs have undergone distinctly different depositional processes at each site. Sediments from the core in the East River appear to have been subject to intense physically driven resuspension, resulting in selective depletion of low molecular weight PAHs within the core presumably due to processes such as enhanced desorption and scouring of particle surfaces. Although sediment PAH concentrations were higher in the East River core compared to the Newark Bay core, porewaters were depleted of the majority of PAHs analysed in the East River core relative to the Newark Bay core, precluding quantifying sediment porewater PAH distribution coefficients in this core. Sedimentary variables such as CM ratio, particle surface area, and sedimentary soot carbon were not related to organic carbon normalized PAH distribution coefficients (K-OC)(obs). Rather in the core from the Newark Bay site, (K-OC)(obs) were influenced by sediment mixing and porewater dissolved organic carbon (DOC). Results indicate that in urban coastal areas, the physical factors influencing time scales of sediment resuspension and deposition may be of primary importance over particle geochemistry in determining whether PAHs will likely equilibrate between sediments and pore waters. (C) 1999 Academic Press.