Ecological Evaluation Technical Guidance - State of New Jersey

Appendix F – Sediment Pore Water Sampling TechniquesThe following briefly describes some of the more recent tools and methods used for thecollection of sediment pore water samples. A detailed discussion of each method is beyondthe scope of this guidance. Rather, this section is intended to simply introduce thesemethods and provide references for their use and interpretation of data generated.Ultimately, the use of these methods should result in a more accurate measure of sitespecificcontaminant bioavailability or toxicity to sediment dwelling organisms.Diffusion Samplers:Diffusion-based samplers consist of a semipermeable membrane or dialysis tube filled withdistilled water, purified fish oil (triolein) or a gel, which rely on a solute gradient toestablish equilibrium between the pore water and the sampler. Diffusion samplers are oftenused in situ for measuring metals, phosphates, and sulfides. Some of the more commonsamplers for in situ diffusion include the following:• Peepers: A sampling device, also referred to as a dialysis cell, which consists of a rigidstructure that can hold volumes of distilled or deionized water separated from theenvironment by a porous membrane. Holes within the rigid structure allow pore waterand associated contaminants to pass through the membrane, allowing the cell to passivelyequilibrate with the surrounding pore water. These samplers are capable of monitoringmost compounds (inorganic and organic) present in dissolved phases (ITRC, 2005).• Semi-Permeable Membrane Devices (SPMD): SPMDs are fat- or lipid-filled membranesthat attempt to mimic uptake into benthos or fish in terms of HOC (hydrophobic organicchemical) absorption to lipids in aquatic organisms (Zimmerman, et al., 2000). SPMDsconsist of a high molecular weight lipid (typically triolein) that is placed into apolyethylene membrane tube. The device may be placed in a perforated stainless steeldeployment device to provide protection when placed in sediment (USEPA, n.d.).• Diffusive gradient in thin films (DGT): DGTs are another type of diffusion sampler, andrefers to two similar tools for collecting metals from sediment pore water (Davison et al.,2000). DGTs differ from other diffusive samplers in that they are typically casings filledwith gels that are specific to the target compound (e.g. a Chelex or acrylamide gel formetals, ferrous-oxide gel for phosphorus). The unique advantage of DGTs over otherdiffusive samplers is that after retrieval, the gel can be cut into segments for multipleanalyses.Equilibrium Samplers:Equilibrium samplers are used to measure the pore water concentrations of freely dissolvedhydrophobic organic compounds (e.g., PCBs, PAHs). These types of samplers can bedeployed in situ (e.g., directly into the sediment) where they accumulate contaminants fromthe pore water, while others are used to extract small quantities of contaminants fromextracted pore water.• Solid Phase Microextraction Devices (SPME): This technique, used to establish PAHpore water concentrations, involves using thin silica fibers coated with an organicpolymer. The fibers can be exposed to sediment pore water in situ or in a laboratorysetting. The freely dissolved hydrophobic organic contamination is sorbed onto theSMPE fiber, which is then injected into a GS/MS for analysis. The direct pore waterEcological Evaluation Technical Guidance Document 117Version 1.2 8/29/12