Principal Investigator Philip Gschwend
It is hypothesized that combustion-derived soot is a significant sorbent in the soils and sediments at many contaminated sites. Further, it is proposed that polycyclic aromatic hydrocarbons (PAHs), present at the time of the soot's formation, sorb strongly within such soot, thereby limiting those compounds' environmental mobility and bioavailability. To investigate these hypotheses, sediment samples are being collected from sites known to be contaminated with PAHs and other organic pollutants: (a) a lake located adjacent to a nearby Superfund site and (b) Quincy Bay in Boston Harbor. Soot carbon (SC) is being isolated from those sediments and characterized for properties potentially relevant to its behavior as a sorbent (particle size, surface area, and pore volume.) Subsequently, these materials will be used in laboratory tests of sorption kinetics and equilibria with a set of PAHs exhibiting a range of hydrophobicities (naphthalene, phenanthrene, and pyrene) and a set of planar and nonplanar PCB congeners. To ascertain if the partitioning of organic pollutants in the field can be explained using these laboratory data, the porewater-sediment distributions of PAHs and PCBs will be measured to see if their in situ Kds require including soot sorption (i.e., Kd = focKoc + fscKsc). To assess the importance of desorption kinetics, these sediments with their pre-existing PAH loads will be used in oxic-slurry laboratory tests of PAH (phenanthrene) biodegradation to see if the sorption rates observed in the preceding laboratory observations can be used in a coupled desorption-biodegradation model to account for the biotransformation rates we will see.