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 h ydrocarbons (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 distinc tly 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 an d scouring of particle surfaces. Although sediment PAH concentrations were higher in the East River core compared to the Newark Bay core, porewaters w ere depleted of the majority of PAHs analysed in the East River core relati ve to the Newark Bay core, precluding quantifying sediment porewater PAH di stribution coefficients in this core. Sedimentary variables such as CM rati o, particle surface area, and sedimentary soot carbon were not related to o rganic carbon normalized PAH distribution coefficients (K-OC)(obs). Rather in the core from the Newark Bay site, (K-OC)(obs) were influenced by sedime nt mixing and porewater dissolved organic carbon (DOC). Results indicate th at in urban coastal areas, the physical factors influencing time scales of sediment resuspension and deposition may be of primary importance over part icle geochemistry in determining whether PAHs will likely equilibrate betwe en sediments and pore waters. (C) 1999 Academic Press.