The Department of Defense (DoD) is responsible for the management of hundreds of impacted sites that contain aquatic sediments. A key factor in appropriate management of chemicals in sediments is an accurate understanding of their distribution and bioavailability, along with appropriate models to predict their fate and transport, as well as associated changes in their bioavailability. In order to meet this need, high resolution data are required, including chemical distribution and bioavailability, biogeochemical conditions, and microbial activity. The overall objective of this project was to demonstrate a sediment High Resolution Passive Profiler (sHRPP) that is capable of evaluating the bioavailable distribution of chemicals (metals and organics) in sediments via passive sampling at centimeter vertical resolution, while simultaneously evaluating dominant redox processes at the same resolution, key gene/microbial densities, and pore water velocity.

sHRPP prepared to be driven into Abrahams Creek for evaluation of PCBs. Data produced from this deployment included information on spatial concentrations (2cm resolution), abundance of PCB dechlorinating cultures, geochemical indicators, and pore velocity.

The sHRPP, made of stainless steel or polycarbonate, is driven into the sediment and can sample depths as deep as ~80 cm. The sHRPP can evaluate the following parameters at fine-scale (~2 cm intervals):

1. Chemical types and concentrations using either equilibration cell water (e.g. metals, chlorinated volatile organic compounds, volatile organic compounds) or by incorporating solid-phase microextraction fibers for hydrophobic organic compounds (e.g., polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dichlorodiphenyltrichloroethane, dichlorodiphenyldichloroethylene, and dichlorodiphenyldichloroethane (DDX))
2. Biogeochemical species (e.g. dissolved organic carbon, chloride, nitrate, nitrite, ferrous iron, total iron, sulfate, sulfide, methane, etc.)
3. Porewater velocity
4. Composition of relevant microbial communities via quantitative polymerase chain reaction analysis of Bio-Sep beads

The ability of the sHRPP to improve the measurement of the occurrence, fate, and transport of chemicals in sediment was demonstrated at four sites including a fresh water tidal marsh (elevated metal concentrations), a PAH-impacted capped freshwater canal, a PCB-impacted freshwater pond, and a DDX-impacted capped river.

The sHRPP was able to measure concentrations of key chemicals at equal or greater sensitivity than comparable traditional technologies. It produced high resolution concentration profiles of geochemical species and measured pore water velocities with depth. It provided increased model resolution and reliability and increased statistical power to evaluate the impact of remedial efforts. The technology required less cost, time, and effort to evaluate sites and produced data not obtainable by other traditional methods or combination of methods.

Currently the sHRPP is not widely available commercially as a turnkey service similar to most passive sampling methods. It is available through Texas Tech University in cooperation with other consultants or a new company called Envirostatus, LLC, which specializes in passive sampling. The project team developed a standard operating procedure and informational voice over power point posted on the ESTCP website that covers the use, applications, and detailed instructions on how to prepare, deploy and sample the sHRPP. (Project Completion - 2023)