Sediment assessment, management, and regulation in the 21st century

Abstract

Nearly 20 years ago, SETAC published the results of a Pellston Workshop on methods for assessing and setting sediment quality guidelines (SQGs) and associated tools (Wenning et al., 2004). This was done to compile the state of science describing the harmful effects of chemical contaminants in sediments on freshwater and marine aquatic life. Since then, there have been significant advances in sediment ecotoxicology, monitoring methods, and risk assessment practices, as well as management strategies. The definition of “sediment quality” has also evolved and now encompasses more than just toxicity. It considers the chemical and physical characteristics of sediment that contribute to the health of aquatic ecosystems, including the quality of overlying waters and aquatic food chains. Advances have been made in the interpretation of the ecosystem services both provided and affected by sediments (Apitz, 2012), as well as environmental baseline values used to identify the nature and extent of environmental changes outside the range of natural variability (Brown et al., 2022).

While sediment sampling methods have changed little over the years, the methods for analyzing and interpreting various biological, chemical, and physical parameters used to evaluate sediment risk have advanced considerably (Bruce et al., 2021). Broader and smarter sediment screening methods and advanced analytical chemistry and assessment methodologies capable of providing insights into the drivers of sediment toxicity offer some relief to traditional limitations of sediment quality investigations (Brennan et al., 2021; de Baat et al., 2019; Feiler et al., 2013). Nanosensors and new analytical methods are available for assessing biological contamination, nanopollution, and new and/or emerging chemical substances in sediments and surface waters to support management activities that protect aquatic life and human health (Hairom et al., 2021). Passive sampling, toxicity identification evaluation methods, and omics-based eco-surveillance tools have matured considerably and provide data that inform sediment assessment, regulation, and management (Heise et al., 2020; Li et al., 2018; Shah et al., 2019). New methods involving measurements of e-DNA and e-RNA and other molecular biomonitoring tools, less intrusive passive samplers to measure contaminants in sediment porewater, and the determination of metrics of biotic and ecological integrity (e.g., taxonomic richness, composition, and tolerance and/or intolerance indices) provide indispensable information for managing aquatic ecosystems more effectively (Anaisce et al., 2023; Giroux et al., 2022).

At the same time, climate change and a relatively new suite of “emerging” contaminants, such as microplastics, nanoparticles, substances in personal care and pharmaceutical products, and perfluorochemicals, have gained increasing attention. Whether standard investigation methods and management approaches sufficiently address these new concerns requires careful consideration. Studies from monitoring networks such as the NORMAN network advocate effects-based measures covering specific bioassay batteries that can identify specific modes of action of chemical pollutants in the aquatic ecosystem to evaluate the real threats of contaminant mixtures and other stressors on aquatic life (Dulio et al., 2018; Yusuf et al., 2021). New or improved statistical methods are available to evaluate ecotoxicological data and large environmental data sets, and to identify habitat features that may be indicative of changes to the structure and function of the ecosystem or the viability of benthic invertebrate communities (Kienzler et al., 2019; Popovic et al., 2024).

It is increasingly important to understand how data are aggregated to inform risk decisions. Different types of investigations, from chemical to ecotoxicological and ecological analyses, are performed in sediment assessment. Advances in weight-of-evidence (WOE) analysis aggregate information from different investigation tools used in sediment assessment to reach conclusions about the probability and magnitude of hazards. New WOE frameworks aim to overcome the limitations of conventional interpretations of traditional sediment chemistry measurements, bioassays examining biological responses and biomarkers in sentinel species, and reliance on worst-case scenarios when interpreting separately chemical or ecotoxicological results (Bates et al., 2018).

Sediment is not, however, only managed to address quality issues. The role of sediments in aquatic ecosystems and supporting various ecosystem services desired by society depends not only on quality but also on sediment quantity, location, and transport potential. In recent years, there has been an increasing focus on “circular” sediment management, emphasizing the importance of the beneficial reuse of dredged materials and nature-based solutions to restore, protect, and enhance aquatic environments. This new attention depends on a broader understanding of ecosystem-specific sediment quality. For example, sediments as a source of material for beach and shoreline protection and for creating and sustaining wetlands and coastal habitats must be of suitable quality, that is, the sediment must be free of potentially harmful concentrations of contaminants. Regional and national coastal and river basin strategies also require a deeper consideration of the role of baseline sediment quantity and quality conditions when devising sustainable and long-term management plans and decision-making. Commercial ports worldwide face challenges surrounding the inevitable trade-offs between preserving and protecting the environment and balancing economic development and social needs in catchments and coastal regions.

Global mandates for sustainable environmental practices are a certainty in the years ahead. Environmental assessments of aquatic ecosystems typically include evaluation and measurement of sediments, focused on land and water use, management on the landscape scale, and the consequences for biodiversity and the provision and resilience of ecosystem functions and services. These views and forecasts of our future clearly show that understanding and managing the dynamic interactions of sediment on a diverse range of endpoints at the watershed scale will be vital in the years ahead for effective sediment management.

The future of sediment management, including strategies for handling dredged materials and beneficial reuse of sediments, as well as for adaptation to global change, will need to adapt quickly by emphasizing nature and nature-based solutions that preserve sediment quality and protect aquatic ecosystems. Sediment management strategies that embrace the concept of co-valorization, which involves economic and ecological considerations for preventing contaminants from entering the environment and preserving natural resources such as sediments, are well underway in the European Union and elsewhere.

Today—20 years later—we find strong demand among resource management professionals in business and government for guidance on practical state-of-the-science information on assessing and managing contaminated sediments. Sediments play an important role in surface water quality and the food chain. Historically, insufficient attention has been given to how investigation and assessment approaches inform sediment management and protect aquatic resources and human use of the aquatic environment. Furthermore, uniform technical guidelines worldwide do not currently exist. This has spurred an ongoing debate among regulatory agencies and stakeholders about managing coastal, freshwater, and marine ecosystems, particularly in situations involving the transboundary management of fisheries, pollution, and water quality. Insights are needed on the underlying scientific principles and utility of different tools for diagnosing a sediment ecosystem's specific biological, chemical, and geophysical properties. Without these insights, stakeholders may be uncertain which approaches and tools work best.

While much of the science underpinning the derivation of SQGs remains unchanged from the 1990s, stakeholders should be reminded of the strengths, limitations, and methodological uncertainties associated with different methods for deriving chemical-specific or waterbody-specific sediment quality benchmarks and guideline values often used by regulatory agencies. Hence, we feel it is time for a new generation of scientists and professionals to review the chemical, physical, and biological attributes that influence contaminant risk and behavior in sediment. A fresh examination, as well, of tools and practices that inform decision-making for remediation, ecological restoration, and sustainable sediment management is called for. A reexamination will raise awareness and provide a technical primer for environmental managers engaged in coastal, river basin, and surface water management, contaminated sediment cleanup, and sediment quality issues.

Working with an international team of experts, we have begun collating these developments in a new book that discusses sediment assessment for 21st-century management. We aim to share this knowledge in 2025. For researchers, we hope this book inspires the development of new and better approaches and tools that integrate investigation, assessment, and remediation of contaminated sediments with future sediment management practices. For sediment managers and regulatory agencies, we hope to further inspire the long-term and sustainable management of aquatic ecosystems.

Richard J. Wenning: Writing—original draft; writing—review and editing. Sabine E. Apitz: Writing—original draft; writing—review and editing.