SW-7 :: Management of contaminated land, groundwater and sediments

Contaminated land, groundwater and sediments relate to several of the EU-challenges. Contaminated soil and sediment pose a particular problem since most pollutants (metals and organic contaminants) do adsorb to organic and mineral particles, contaminants accumulate and reach concentrations often several orders of magnitude higher than in water. The contaminants are often also less biodegradable when they are adsorbed to particles and the polluted sediments and soils will constitute a new chronic source of contaminants, years and decades after the emissions have stopped. Traditional remediation generally consists in excavation or dredging and landfill disposal, which is both highly disruptive to the environment (e.g. destroys habitats and cause re-suspension of contaminated particles) often expensive and it is questioned whether it is a sustainable solution. There is often also a long time-lag between when the emissions took place and when the sites are remediated. Climate and geological changes can accelerate these problems. E.g. the northern coastline of the Baltic Sea is subject to a post-glacial land uplift, which is revealing large amounts of deposited and highly contaminated fibre residues from the paper- and pulp industry and “sediment slides” cause a release en masse of sediment-bound contaminants. The fibre masses contain extreme concentrations of e.g. PCBs, dioxins and mercury and contaminant concentrations in eagle eggs are rising again. Ecosystem and ecosystem services are threatened at several levels, resulting in human health and ecological effects as well as economic and social effects.

New solutions are needed in order to on one hand reduce new emissions, i.e. prevent them from accumulating in the environment and on the other hand to remediate already polluted soils and sediments.

Several international and national research agendas deal with contaminated land . It is stressed that “solutions oriented” research on environmental pollution is needed in general and specifically for risk assessment and remediation of contaminated land and sediments.

Specific research topics:
• Research related to the “risk concept”: Probability and consequences; what are acceptable levels of risk? How can we “live” with risks? Individual or societal level views in risk assessment. What is the intrinsic value of the environment?
• What environmental ethics aspects are relevant in contaminated land management and how can we take long term responsibility for “new” solutions – in the light of history and related to the use of ecosystem services
• How can we re-use excavated soil and minimize excavation of “clean” soil. How can we make use of contaminated sites as such (fit-for-purpose).

Why? Risk based decisions usually include various kinds of valuations, although the grounds for these are not always clear. How can and do we value nature in sparsely populated areas (today) in comparison to densely populated areas, or value nature for today’s population versus future generations?
Natural Capital
• How can we better understand, address and describe contaminant behaviour in the land-water-sediment system including; effects from secondary sources; sediment processes in situ (such as natural attenuation, compound transformation, and natural capping/burial) and “new”/emerging contaminants and their interaction with the soil-water-sediment system (research on toxicity, bioavailability, physicochemical properties, fate and transport, analytical methods (low detection limits))?
• Innovative strategies, methods and tools to sample/characterise and assess contaminants in bedrock, soil and sediment need to be developed. This includes assessment and modelling of contaminant “source to sea” and in situ transfer (flux) between and within (including bioavailability) compartments (sediment, biota, water). Also, biomimetic methods (for bioavailability and effect assessments) that can be used at early Tiers (Tier 1 or 2) methods (i.e. quick and inexpensive) need to be developed.
• We need to find or define indicators and descriptors of effects of contaminants on organisms (e.g. biomarkers) and on ecosystem services (e.g. mineralization of organic matter, plant production, healthy fish populations, and safe fish for consumption).
Why? We tend to focus on one medium at a time in research and fail to provide knowledge on the S-S-W-system needed in order to efficiently manage contamination in practice. We need a holistic view on the distribution, bioavailability and effects of environmental contaminants and an understanding of the interaction between compartments (soil-water-sediment-biota). Also, as primary sources, i.e. new emissions are dealt with, secondary sources become more important. Further, current risk assessment procedures for contaminated sites rely on guidelines that were developed for land sites and there is an urgent need to develop guidance, tools and methods suitable for contaminated sediment sites. With REACH and national restrictions we have become better at reducing our contaminant emissions. Still, however, “new” contaminants such as PFAS-substances are encountered in soil, groundwater and sediment and have to be dealt with.
Land Management:
Development of tools and methods for sustainable management and planning:
• How can we best prioritize between contaminated sediment areas with respect to protection of the water recipient (lake, sea) at a regional and national scale or prioritize between remediation options at a site?
• How can we assess climate related risks and “geotechnical risks”, e.g. contaminated sites at locations vulnerable to flooding or land slides?
• Innovative and cost effective methods need to be developed (in situ or on-site remediation, more efficient “dig-and-dump” measures, remediation methods for contaminants in the bedrock in general.) Also, long term monitoring is needed to provide feedback, and improve remediation techniques.
• Statistical and modelling approaches need to be developed, or adapted to the purpose, for determining so called “representative concentrations” (with respect to heterogeneity, variability) to minimize risk of over- och underestimate need for remediation. We also need to evaluate how information technology could be more efficiently used in contaminated land and sediment applications (e.g. new monitoring techniques, GIS techniques for mapping etc.).
Why? More sustainable remediation methods are needed than traditional excavation and landfilling. Also, in order to take on societal challenges new solutions and techniques should benefit from the advances in information technology. In general, environmental practices are still traditional and e.g. costs/measurements are high, resulting in few data. Continuous or long term measurement could provide e.g. a basis for research and for evaluating measures taken. Better/faster sensors as well as interfaces for data collection (apps) and presentations are needed.
Net Impacts
• What are the effects from diffuse contaminant sources or sum of contribution from many ”small” sources, from contaminant mixtures and what is the impact of contaminant sinks (such as sediments, fibre banks etc.) on ecosystem services in the light of land uprising and climate change?
• What are the risks from “new”/emerging contaminants? We need research on toxicity, bioavailability, physicochemical properties, fate and transport, analytical methods (low detection limits), especially PFAS-substances, fertilizers, pharmaceuticals, “unknowns”).
• How do approaches aiming at integrating social, economic and ecological dimensions in decision making succeed in meeting the original goals in real applications?
• Assessments of the net effect of remediation measures - what risks are actually reduced and to what extent are risks elevated by the remediation measures, e.g. spread of contaminated sediment due to excavation? In what time perspective?
• Research on long term efficiency, effectiveness and sustainability of remediation alternatives. This should include long-term monitoring to verify assessments and sustainability in solutions (e.g. long term performance of mitigation measures for vapour intrusion in buildings from volatile contaminants, of stabilized and solidified contaminated soil or sediments, of capping of sediments).
Why? Contaminated land management, strategies, tools etc. are to a great extent focused on the most hazardous point sources/single contaminants and questions arise whether we underestimate the threat from the many sites that have not individually been ranked as the worst contaminated ones, or from secondary sources. Decision support tools and approaches are generally intended to support informed decisions that are aiming at sustainable solutions. Transparency is a key component. Tools need to be easily accessible and user-friendly, in order to be used in practice. However, tools tend to be based on underlying (often complex) theories, equations as well as assumptions and simplifications or even judgment of values that may, or may not, be agreed but are “built in” in the methodology. In order to manage contaminated sites more sustainably we also need to learn from measures already taken.