Demonstration and Evaluation of Solid Phase Microextraction for the Assessment of Bioavailability and Contaminant Mobility. ESTCP Cost and Performance Report.

摘要

The goal of the project was to develop and standardize a procedure using field deployable solid phase microextraction (SPME) for the measurement of freely dissolved porewater concentrations of hydrophobic organics and demonstrate the relationship of these measurements to contaminant flux, bioavailability, and bioaccumulation. In situ SPME is a passive sampling approach for measuring hydrophobic organic contaminants in porewater and involves the insertion of a polymer sorbent into the sediments for a specific period of time and measuring the contaminants sorbed to the polymer. The contaminant concentration on the polymer is directly proportional to the dissolved contaminant concentration in the porewater. The technology demonstrated here uses polydimethylsiloxane (PDMS) as a polymer sorbent as a thin coating on a glass core but is essentially equivalent to SPME using other sorbents. The primary advantages of PDMS are cylindrical geometry (for ease of insertion into sediments), somewhat lower sorption capacity than POM and PE (which aids the rapid achievement of equilibrium), and commercial availability in a variety of sizes and polymer coating thicknesses. Simple approaches to shield the PDMS fiber and to segment and analyze the fiber were developed as part of the demonstration. Conventional analyses are employed that require no special processing or analytical techniques so any lab that can conduct polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyl (PCB) analyses can support the technology. The work was conducted in sediments both in laboratory and field testing. Laboratory testing avoids problematic field deployments where placement and retrieval is too difficult or costly. This testing also allows coupling of availability measurements with laboratory bioassays under controlled conditions. The field testing allows determination of availability and cap performance under conditions that might not be reproducible in the laboratory.