Passive sampling methods for contaminated sediments: Risk assessment and management

This paper details how activity-based passive sampling methods (PSMs), which provide information on bioavailability in terms of freely dissolved contaminant concentrations (Cfree), can be used to better inform risk management decision making at multiple points in the process of assessing and managing contaminated sediment sites. PSMs can increase certainty in site investigation and management, because Cfree is a better predictor of bioavailability than total bulk sediment concentration (Ctotal) for 4 key endpoints included in conceptual site models (benthic organism toxicity, bioaccumulation, sediment flux, and water column exposures). The use of passive sampling devices (PSDs) presents challenges with respect to representative sampling for estimating average concentrations and other metrics relevant for exposure and risk assessment. These challenges can be addressed by designing studies that account for sources of variation associated with PSMs and considering appropriate spatial scales to meet study objectives. Possible applications of PSMs include: quantifying spatial and temporal trends in bioavailable contaminants, identifying and evaluating contaminant source contributions, calibrating site-specific models, and, improving weight-of-evidence based decision frameworks. PSM data can be used to assist in delineating sediment management zones based on likelihood of exposure effects, monitor remedy effectiveness, and, evaluate risk reduction after sediment treatment, disposal, or beneficial reuse after management actions. Examples are provided illustrating why PSMs and freely dissolved contaminant concentrations (Cfree) should be incorporated into contaminated sediment investigations and study designs to better focus on and understand contaminant bioavailability, more accurately estimate exposure to sediment-associated contaminants, and better inform risk management decisions. Research and communication needs for encouraging broader use are discussed. Integr Environ Assess Manag 2014;10:224–236. © 2014 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of SETAC

Streamlining contaminated sediment management: the use of advanced sediment characterization — preliminary results

Simply knowing the geographic extent of sediment contamination within a bay or estuary does not provide sufficient insight to help a site manager or stakeholder begin to assess how to manage sediments deemed either an ecological risk or regulatory violation. A better approach is to assess contaminant distribution and behavior at a micro-scale in parallel with macro-scale site assessments. In such an approach, a site investigation includes an assessment of contaminant/sediment biogeochemistry, as it will impact bioavailability, risk, and potential management options. This paper reviews some approaches for assessing contaminant bioavailability, distribution and degradability, and presents preliminary results from some biogeochemical sediment assays. Some of the potential uses and limitations of such assays are discussed. Selective leaches, using alcohol or digestive juices to determine bioavailable contaminant fractions still require some validation. Assessments of contaminant distribution as a function of grain size can lend insight into both contaminant mobility and management strategies. Biodegradation studies in real sediments are complicated by analytical and heterogeneity difficulties, but can, if carried out carefully, provide useful information.</jats:p