A method for using polyethylene passive samplers to measure polycyclic aromatic hydrocarbon chemical activity in sediments

Abstract

In order to aid in the determination of the hazards posed by hydrophobic organic compounds (HOCs) in sediment beds, a method for the use of polyethylene (PE) sheets as passive sampling devices for measuring chemical activities was explored. A model which depends on a concentration gradient and two mass transfer limiting zones in series was used. Internal tracer chemicals within the polyethylene devices (PEDs) were used to calibrate the mass transfer model which can have different mass transfer coefficients depending on the site and target chemicals being investigated. The model allowed for the measurement of HOC chemical activities by measuring the change of mass of tracer and target chemical within the PED, and knowing the PE-water partitioning coefficient, ..., and the liquid solubility, ..., of the target chemical. The method was tested using PEDs impregnated with dlO-phenanthrene and dlO-pyrene. First, PEDs were used to measure known concentrations of phenanthrene and fluoranthene in stirred seawaters. Seeing that the PEDs performed well, returning results which were within 25% of the known chemical activities, PEDs were then tested for measuring phenanthrene, fluoranthene, and pyrene in Boston Harbor sediments.

(cont.) Porewaters of Boston Harbor sediments were extracted as a benchmark against which to assess the performance of three methods for measuring sediment chemical activities: (1) PEDs using impregnated tracers exposed for 52 and 92 days to simulated sediment beds, (2) sediment extractions and an equilibrium partitioning model as recommended by EPA for determining sediment benchmarks, and (3) PE samplers brought to equilibrium with sediment slurries. The results of this study showed that the two methods using PE passive samplers produced measurements which were within a factor of 2 of the porewater extraction results. The equilibrium partitioning model, however, produced results which were at least an order of magnitude different from the measurements of the other methods. Future work on PEDs is needed to develop faster response times and internal standards which will allow for the measurement of a more diverse set of HOCs.