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Porewater Concentrations and Bioavailability: How You Can Measure Them and Why They Influence Contaminated Sediment Remediation

Superfund Research Program

NARPM Presents and Risk e-Learning offered a four-part webinar series to help you understand why, how, and when to measure porewater concentrations and bioavailability as part of contaminated sediment assessment and management. Hosted jointly by the EPA Contaminated Sediments Forum and the National Institute of Environmental Health Science's Superfund Research Program, this webinar series also focused on the use of passive sampling devices (PSDs) and what they tell us about contaminant bioavailability. Previously held as a course at the National Association for Remedial Project Managers (NARPM) Training Program meeting, the webinar series featured experts in the field of porewater and bioavailability and included lectures and case studies, including practical tips to maximize the utility of porewater and bioavailability measurements.

Presenters explained the basics of chemical fate, transport, and uptake, with a focus on porewater as a key route of exposure and a strong indicator of bioavailability. PSDs are a promising technology for measuring porewater concentrations and assessing bioavailability, particularly for common sediment contaminants, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), chlorinated pesticides, and dioxin-like compounds. The webinar series included information about direct measurements of porewater, such as centrifuging sediment samples or Henry Samplers, which may also be used and are particularly useful for measuring metals.

Session I – Introduction to Porewater, Bioavailability, and PSDs
October 6, 2014, 12:30-2:30 p.m. EDT
An archive of this webinar is available on EPA's Clu-in Training & Events Web page.

This was the first session of the four-part webinar series to help you understand why, how, and when to measure porewater concentrations and bioavailability as part of contaminated sediment assessment and management. It provided an introduction to porewater concentrations, the use of passive sampling devices (PSDs), and what they tell us about contaminant bioavailability.

Presenters explained the basics of porewater and bioavailability at contaminated sediment sites, including chemical fate, transport, and uptake, with a focus on porewater as a key route of exposure and a strong indicator of bioavailability. The webinar highlighted the application of PSDs to measure freely dissolved contaminants at Superfund sites. An emphasis was placed on how sampling methods can be used to assess, monitor, and manage risk at these sites, an important part of the cleanup process.

  • Introduction and Moderation: Heather Henry, Superfund Research Program
  • Presenter 1: Karl Gustavson, U.S. Army Corps of Engineers
    Presentation Title: Porewater and Bioavailability at Contaminated Sediment Sites
  • Presenter 2: Marc Greenberg, EPA Environmental Response Team
    Presentation Title: Passive Sampling Methods for Managing Contaminated Sediments: Risk Assessment & Management

Session II – PSDs for Organic Contaminants
November 19, 2014, 2:00-4:00 p.m. EST
An archive of this webinar is available on EPA's Clu-in Training & Events Web page.

Contaminated sediments pose an on-going, pervasive, global challenge to environmental managers as sediments can reflect a legacy of pollution that can impair the beneficial uses of water bodies. A formidable challenge in assessing the risks of contaminated sediments has been elucidation and measurement of contaminant bioavailability, expressed as the freely dissolved concentration (Cfree) in interstitial water, which serves as a surrogate measure of the substances' chemical activity. Recent advances in passive sampling methods (PSMs) enable Cfree of sediment-associated organic contaminants to be quantified at trace levels, thereby overcoming current limitations of predictive models. As a result, PSMs afford the opportunity for a paradigm shift from traditional practice that can effectively reduce the uncertainty in risk assessment and bolster confidence in the available science to support sound management of contaminated sediments. The first presentation provided a brief overview of the state of the science and the challenges we face in applying PSMs for more informed decision making.

The second presentation focused on four aspects of passive sampling: (1) the kinds of information passive sampling provides; (2) the different types of passive samplers and how they work; (3) the preparation, deployment, recovery, and storage of passive samplers; and (4) the analysis of passive sampler data. Objectives of this presentation were to demonstrate that passive sampling operates on the well-understood principles of equilibrium partitioning and sampling and that the application of passive sampling is no more complicated than current contaminant sampling methods.

The third presentation presented the outcome of a recent SETAC Workshop on Passive Sampling, focusing on the practical guidance for implementation. It covered choice of polymer type, deployment methods, and corrections for non-equilibrium conditions, temperature, and salinity. A few examples of the use of passive sampling in assessing toxicity and bioaccumulation were also provided.

  • Introduction and Moderation: Matthew Lambert, Office of Superfund Remediation and Technology Innovation
  • Presenter 1: Keith Maruya, Southern California Coastal Water Research Project
    Presentation Title: Passive Sampling Methods for Managing Contaminated Sediments: State of the Science
  • Presenter 2: Rob Burgess, EPA Office of Research and Development
    Presentation Title: Passive Sampling for Measuring Freely Dissolved Contaminants in Sediments: Concepts and Principles
  • Presenter 3: Upal Ghosh, University of Maryland, Baltimore County
    Presentation Title: Passive Sampling for the Measurement of Freely Dissolved Contaminants in Water: Practical Guidance

Session III – Metals and PSDs
December 1, 2014, 12:30-2:30 p.m. EST
An archive of this webinar is available on EPA's Clu-in Training & Events Web page.

Dissolved metal concentrations of sediment porewaters provide important information that is useful for predicting bioavailability and toxicity at sites with metal contaminated sediments. Numerous methods are available to sample and measure porewater metals; however, it is critical that appropriate techniques are selected and employed based on factors including data needs and site characteristics. During the first presentation, methods and approaches to accurately measure metals in sediment porewater were discussed along with conditions that influence metal behavior and bioavailability in soils and sediments.

The second presentation of this session presented a case study of the Cottage Grove Reservoir, located approximately 15 km downstream of the historic Black Butte Mine Superfund Site. The reservoir contains fish that are elevated in methylmercury. Region 10 is working with the Office of Research & Development to identify sources of methylmercury production within the reservoir sediment. Sediment porewater samples have provided insights into areas where inorganic mercury is more bioavailable and methylation is enhanced.

  • Introduction and Moderation: Michael Adam, EPA Technology Integration and Information Branch
  • Presenter 1: Mark Cantwell, EPA Office of Research and Development
    Presentation Title: Methods for Measuring and Assessing Dissolved Metals in Sediment Porewaters
  • Presenter 2: Chris Eckley, EPA Region 10
    Presentation Title: Measurements of Mercury Methylation in Porewater: A Case Study from the Black Butte Mine Superfund Site, Oregon

Session IV – Case Studies: PSDs for Organic Contaminants
December 15, 2014, 12:30-2:30 p.m. EST
An archive of this webinar will be available on EPA's Clu-in Training & Events Web page.

This webinar helped Remedial Project Managers (RPMs) understand why, how, and when to measure porewater as part of contaminated sediment assessment. Participants learned how RPMs have used bioavailability and porewater measurements at two sediment sites contaminated with hydrophobic organic chemicals. The case studies also touched on the technical and logistical details of deploying and analyzing passive samplers, such as deployment times and analytical techniques, and provided tips for success.

  • Introduction and Moderation: Charles G. Maurice, Superfund & Technology Liaison, EPA Region 5
  • Presenter 1: Judy Huang, Remedial Project Manager, EPA Region 9
    Presentation Title: Case Study: Palos Verdes Shelf
  • Presenter 2: Rachelle Thompson, Remedial Project Manager, EPA Region 9
    Presentation Title: Passive Sampling Case Study: United Heckathorn Superfund Site

Special thanks to our webinar and NARPM course development team:

  • Matt Lambert, US EPA Office of Superfund Remediation and Technology Innovation (OSRTI)
  • Heather Henry, NIEHS Superfund Research Program
  • Helen Bottcher, US EPA Remedial Project Manager (RPM) Region 10
  • Jim Hahnenberg, US EPA RPM Region 5
  • Clint Sperry, US EPA RPM Region 7
  • Michael Adam, US EPA OSRTI
  • Gary Turner, US EPA Technology Innovation and Field Services Division (TIFSD)
  • Jean Balent, US EPA TIFSD
  • Justin Crane, MDB, Inc.
  • Austin Oelschlager, Tetra Tech, Inc.

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