Susanne Heise

Historical Contaminated Sediments and Soils at the River Basin Scale

Background, Aims, and ScopeData from the Elbe River and its tributaries indicate, despite extensive improvement in water quality during the last 15 years, that the respective sediment situation of many priority pollutants has not reached an acceptable level. For the coming decades, risks for downstream sites and stakeholders will persist, mainly due to secondary sources originating from historical pollution of soils and sediments in the catchment area. In practice, a catchment-wide assessment of historical contaminated soil and sediment should apply a three-step approach: (i) Identification of substances of concern (s.o.c.) and their classification into ’hazard classes of compounds’; (ii) identification of areas of concern (a.o.c.) and their classification into ‘hazard classes of sites’; (iii) identification of areas of risk (a.o.r.) and their assessment relative to each other with regard to the probability of polluting the sediments in the downstream reaches. The conversion of this concept has to consider the underlying philosophy of the EU Water Framework Directive, particularly with respect to the analysis and monitoring of priority substances in solid matrices. However, major deficiencies are still in the assessment and prognosis of resuspension processes, and potential approaches to fill this gap are described both in theory and from examples of the Elbe River.MethodsThe sediment stability testing facilities consist of a unique triple set developed by innovative experimental laboratory and field research. The instrumental facilities consisting of a tube corer and a pressurized channel allow one to measure not only the onset of erosion (critical bed shear stress), but also the erosion rate for different sediment layers. Undisturbed sediment samples were taken from contaminated sites, e.g. in near-bank groyne fields and floodplains, using (i) core sampler (diameter 14 cm, length 150 cm) for sediment erodibility depth profiling and (ii) box sampler (30*70 cm2 top view area, 28 cm depth) for comparing and upscaling the results from the laboratory to the field. Sediment properties such as grain size spectrum (laser beam attenuation), water and gas content were analyzed by a non-intrusive, high frequency, capacity measurement method and bulk density by γ-ray.Results and DiscussionSediment core samples from flooded areas in the Middle Elbe indicate, that, except from the uppermost 5 cm and at a depth of from 47 to 48 cm, where the critical shear stress is very low (0.5 Pa), the critical bottom shear stress is between 1.2 Pa and 3.4 Pa, i.e. at a moderate level. Major reasons for the distinct heterogeneity of the erosion stability are differences in consolidation processes, grain size distribution and in the composition of stabilizing exudates in the individual sediment layers. Similar to the erosion stability depth profile, the metal data exhibit short-range heterogeneities; the variations in the individual layers can be explained by different proportions of fine grained components and by an improvement of suspended matter quality in the course of time. A comparison of the metal contents of embanked alluvial soils and unembanked alluvial areas suggests the following causal chain: Recent floodplain areas at low mean water levels exhibiting high concentrations of organic carbon represent the most highly contaminated sites. On the other hand, insignificant pollution has occurred on alluvial areas, which were embanked already at pre-industrial times. In the case of flood events, due to the combination of flooding probability and flow conditions, the most favorable conditions for the deposition of nutrient- and contaminant-rich suspended particulate matter are found in the low level depressions with low current. Within a typical river section of 1 km length in the lower middle Elbe, the groyne fields are recognized as dominant, slack-water zones containing the following nutrient and trace metal loads (reference year 2001, anthropogenic proportions): 287 t organic carbon, 17.6 t phosphorous, 17.4 t nitrogen, and 16.7 t sulfur; 8.6 t zinc, 1.1 t copper, 0.9 t lead, 0.4 t chromium, and 0.2 t nickel, respectively. The estimated nutrient and pollutant loads, deposited on the floodplains and in the river course, clearly demonstrate the specific sink function of both sites. At the same time, however, the results suggest, in contrast to the deposits in the floodplains, that sediments within the river course may partly be remobilized. This means that the longterm sink function can at least temporarily become a significant source character, involving the hazard of a substantial deterioration of the downstream sections of the river basin.Conclusions and OutlookIn view of the findings of relative low erosion stabilities of groyne field sediments and, in particular, after the extreme Elbe flood from August 2002, a prime question relates to the remobilization risks of these sediments typically enriched in contaminants and nutrients. The combined view on substances, areas and processes of concern in the Elbe catchment - with special emphasis on historical contamination of floodplain soils and sediments, as well as on groyne field sediments, as significant secondary sources of pollution - is a typical example for the holistic river basin approach of the European Water Framework Directive (WFD), both with respect to assessment of ecological risks and the development of remediation measures. In the latter respect, recent developments in ‘soft’ (geochemical and biological) techniques on contaminated soils and sediments, both with respect to policy aspects as well as to technical developments have led to a stimulation of in-situ remediation options, such as sub-aqueous depots, active capping, and application of natural attenuation processes. Limited financial resources require a direction of investments to those sites with the highest efficiencies in risk reduction. Establishing a rough sediment dynamic model, building on tributary/Elbe dilution factors, sedimentation data, suspended particulate matter monitoring data as well as calculations of long-term costs and benefits, based on risk management, could be essential steps in a basin wide river management.

Application of a Sediment Quality Triad and Different Statistical Approaches (Hasse Diagrams and Fuzzy Logic) for the Comparative Evaluation of Small Streams

In order to evaluate the ecotoxicological contamination of 12 aquatic sites in streams within the catch ment area of the Neckar River, a sediment quality triad (SQT) approach was applied. In contrast to Chapmans original triad approach, not only sediments, but also surface waters were examined. In brief, to obtain a com prehensive insight into the potential ecotoxicological hazard, both acute toxicity and more specific effects such as mutagenic, genotoxic, teratogenic, dioxin- and estrogen-like responses were recorded. Different statistical methods (ranking, cluster analyses, Hasse diagram techniques, and fuzzy logic) for the evaluation and presentation of the SQT data were compared with respect to the needs of environmental decision-making. Results document advan tages and disadvantages of the methods applied for the evaluation and classification of data within the complex data matrixes. The ranking procedure presented as well as the Hasse diagram technique seem to be suitable tools to elucidate the pattern of the ecotoxicological load. However, these classification methods require expert knowledge to interpret the ranking results with respect to decision-making in environmental sciences and policy. In contrast, fuzzy logic allows both to develop site-specific expert systems in order to assess the ecotoxicological burden and to give insight into the pattern of the contamination.

The need for new concepts in risk management of sediments historical developments, future perspectives and new approaches

Being part of a highly dynamic system, contaminated sediments are especially in need of an integrated management approach. Due to change in importance from source to diffuse pollution and the variety of chemical substances in the environ-ment, different scientific fields need to cooperate and incorpo-rate their data in a common risk assessment scheme. Public perception of risk that is associated with sediments and with chemical data is low while the acceptance of ecotoxico-logical data with decision makers is often missing. A growing demand of the public to be involved in decision processes and informed about environmental problems demands a change of methods and concepts in the future. Necessity of an integration of risk assessment and management procedures has been suggested in order to increase the efficiency of the process and the early involvement of public concern. As the confidence in experts’ opinions decreases, a strong need for communication with and transparency for all involved parties arises.

Impact of particle size and light exposure on the effects of TiO2 nanoparticles on Caenorhabditis elegans

The increasing use of engineered nanoparticles in industrial and consumer products leads to a release of the anthropogenic contaminants to the aquatic environment. To obtain a better understanding of the environmental effects of these particles, the nematode Caenorhabditis elegans was used to investigate the organism-level effects and in vivo molecular responses. Toxicity of bulk-scale (∼160 nm) and nanoscale (21 nm) titanium dioxide (TiO2 ) was tested under dark and light conditions, following ISO 10872. The expression of sod-3, a mitochondrial superoxide dismutase, was quantified as an indicator for oxidative stress induced by the photocatalytically active material. Particle sizes were estimated using dynamic light scattering and scanning electron microscopy. Although both materials agglomerated to a comparable secondary particle size of 300 nm to 1500 nm and were ingested into the intestine, only nanoscale-TiO2 significantly inhibited reproduction (lowest-observed-effect-concentration [LOEC]: 10 mg/L). Light exposure induced the production of reactive oxygen species (ROS) by nanoscale-TiO2 and increased toxicity of the nanomaterial from a median effect concentration of more than 100 mg/L to 53 mg/L. No evidence was found for inner cellular photocatalytic activity of nanoscale-TiO2 . Therefore, oxidative damage of the membranes of intestinal cells is suggested as a potential mode of action. Results highlight the importance of primary particle size and environmental parameters on the toxicity of TiO2 .

Sediment Management Objectives and Risk Indicators

Publisher Summary This chapter discusses different aspects of social and societal driving forces and objectives in sediment risk management and introduces indicators as triggers for selecting management options on a site-specific basis, as well as on a larger scale. The guiding risk management objective is to reduce risk posed by contaminated sediments to humans and ecological receptors to a level deemed tolerable by society and to control and monitor sediment quality and ensure public communication, with the final aim of complying with the European Water Framework Directive (WFD) and Habitats Directive. This comprehensive statement implies a number of factors: (1) The principal issue of the management objective is risk reduction. (2) Controlling and monitoring are part of risk management. (3) Desirable levels of risk are determined by society – this implies that, e.g. environmental protection limits may not be enforced if the stakeholders opt against it. (4) Public communication and involvement is an essential part of risk management strategies, because not only this is legally required by various European Conventions, but also because experience shows that risk tolerance decreases with limited access to information and with the feeling of being powerless and controlled by external forces. Therefore, meeting regulatory criteria is one of four specific objectives relevant to sediment risk management, in addition to maintaining economic viability, ensuring environmental quality and development of the natural environment, and securing quality of human life.

Prioritisation at River Basin Scale, Risk Assessment at Site-Specific Scale: Suggested Approaches

Publisher Summary With regard to sediment management, there is a need for classification methods at two different spatial scales, the river basin scale and the local, site-specific scale. Decision-making at the river basin scale involves setting priorities for sediment units throughout the basin that account for several kinds of risk and management objectives, and prioritizing these sediment units for both socioeconomic and ecological management actions. This chapter discusses approaches for the prioritization at river basin scale and risk assessment at site-specific scale. The best management option can be selected using comparative risk assessments. Sediment risk assessment is categorized in two methods: (1) in situ , corresponding to site-specific risk assessments and (2) ex situ , corresponding to comparative risk assessment for dredged material disposal options. Sediments as well as the organizations and regulatory criteria that affect them are affected by actions at both the site-specific and river basin scale. These scales are constantly interacting through time; and the interactions are not only the consequences of the respective institutional positions and responsibilities, they also result from stakeholder (public) involvement. Risk assessment frameworks include four basic elements: problem definition, analysis of effects and exposure, characterization, and a synthesis of this information to estimate risk.

Effects of Phenanthrene on Lemna minor in a Sediment–Water Systemand the Impacts of UVB

The objective of this study was to evaluate if the Lemna -bioassay is appropriate to test contaminated sediments. A mixture of sand was spiked with phenanthrene to investigate whether sediment-bound pollutants can affect the plants via direct contact of the roots or the underside of the leaves. After 24 h of equilibration for sorption/desorption processes, the test was carried out in the sediment–water mixture, and another test was performed with the aqueous phase which was separated from the sediment. The growth inhibition of Lemna was nearly the same in both tests. Hence it follows that the toxicant is adsorbed from the aqueous phase via the underside of the leaves and sediment bound phenanthrene is not bioavailable. Polycyclic aromatic hydrocarbons are known to show photoinduced toxicity to plants in the presence of UV which is a result of photosensitization reactions in the plant and photomodification to more toxic and better soluble photoproducts. Photoinduced toxicity could be observed in the water phase during UVB treatment, whereas the presence of suspended sediment probably lowered the UV intensity, resulting in a lower growth inhibition.

The Role of Risk Management and Communication in Sustainable Sediment Management

Publisher Summary This chapter discusses the role of risk management and communication in sustainable sediment management. The excerpts are from the regulations made and implemented in European Union. Scientific risk assessment is an integral part of risk management; this tool helps determine the probability and degree of risk and provides the scientific basis for decision making on management options. Such risk is generally defined as the product of the magnitude of a hazard and its probability—for example, the implementation of the Water Framework Directive (WFD, 2000/60/EC) is changing the scope of water management from the local scale to basin (watershed or catchment) scale (often transboundary). It aims to establish a framework for the protection of inland surface, transitional, and coastal waters and groundwaters to prevent further deterioration and protect and enhance the status of aquatic ecosystems and the water uses, as well as the terrestrial ecosystems and wetlands linked to them. The WFD approach encompasses measures of ecological, hydrological, and hydrogeological systems including targets reflecting the ecological integrity of the water body.

The Way Forward for Sediment Risk Management and Communication — A Summary

Publisher Summary This chapter summarizes sediment risk management and communication techniques. The objective for sediment risk management, as defined by European Demand Driven Sediment Research Network (SedNet) Working Group on “Risk Management and Communication,” is to reduce risk posed by contaminated sediments to humans and ecological receptors to a level deemed tolerable by society and to control and monitor sediment quality and ensure public communication with the final aim of complying with the EU WFD and Habitats Directive. As the term “society” comprises scientists as well as lay people in the field of risk assessment, the level—that is, deemed tolerable—can only be the outcome of a balance of different risk perceptions and priorities. This comprehensive objective has a number of implications, such as risk assessment, risk reduction, and determination of the probability of risk and the ecological or human health effects.

Sediment Toxicity Data

The overall goal of a well-designed and well-implemented sampling and analysis program is to measure accurately what is really the status of the area studied. Environmental decisions are made on the assumption that analytical results are, within known limits of accuracy and precision, representative of site conditions. Many sources of error exist that could affect the analytical results. These sources of error may include sample collection methods, sample handling, preservation, and transport; personnel training; analytical methods; data reporting; and record keeping. Therefore, a quality assurance program has to be designed for each sediment quality evaluation to minimize these sources of error and to control all phases of the monitoring process.