Passive sampling methods for contaminated sediments: State of the science for metals

“Dissolved” concentrations of contaminants in sediment porewater (C(free)) provide a more relevant exposure metric for risk assessment than do total concentrations. Passive sampling methods (PSMs) for estimating C(free) offer the potential for cost-efficient and accurate in situ characterization of C(free) for inorganic sediment contaminants. In contrast to the PSMs validated and applied for organic contaminants, the various passive sampling devices developed for metals, metalloids, and some nonmetals (collectively termed “metals”) have been exploited to a limited extent, despite recognized advantages that include low detection limits, detection of time-averaged trends, high spatial resolution, information about dissolved metal speciation, and the ability to capture episodic events and cyclic changes that may be missed by occasional grab sampling. We summarize the PSM approaches for assessing metal toxicity to, and bioaccumulation by, sediment-dwelling biota, including the recognized advantages and limitations of each approach, the need for standardization, and further work needed to facilitate broader acceptance and application of PSM-derived information by decision makers. Integr Environ Assess Manag 2014;10:179–196. © 2014 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of SETAC. KEY POINTS: 1. Passive sampling methods (PSMs) offer the potential for cost-efficient and accurate in situ characterization of the dissolved concentrations for inorganic sediment contaminants. 2. PSMs are useful for evaluating the geochemical behavior of metals in surficial sediments, including determination of fluxes across the sediment-water interface, and post-depositional changes in metal speciation. 3. Few studies have tried to link PSM responses in sediments to metal uptake and toxicity responses in benthic organisms. There is a clear need for further studies. 4. Future PSMs could be designed to mimic saturable kinetics, which would fill the gap between the kinetic and the equilibrium regime samplers currently used, and may improve prediction of metals accumulation by benthic organisms.