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European Experience on Application of Site-Specific Ecological Risk Assessment in Terrestrial Ecosystems

Posted on: Wednesday, 15 March 2006, 12:00 CST

By Faber, Jack H

ABSTRACT

This article describes the current state of the development toward a common European framework for site-specific ecological risk assessment (SS-ERA) Although common progression has been slow in the past two years, earlier activities were very promising. Results are presented of a 2001 workshop to discuss the scientific development and policy needs in preparation of such a common framework. The framework was recommended to follow a tiered approach. Other important elements for a common European framework for SS-ERA were identified to be the use of generic values in the first tier and bioassays in later tiers, to address bioavailability in the assessment, to differentiate for land use. Also, the framework should allow for negotiation between stakeholders specific to the site. These aspects are present in the Dutch approach to SS-ERA, and this article further presents some experience with the application of this framework in a large case of SS-ERA in The Netherlands. The derivation of suitable ecological parameters and assessment criteria in view of land use in a tiered approach risk assessment is focused on, and the interactive process between stakeholders and ongoing discussions concerning references and criteria for assessment are illustrated.

Key Words: soil contamination, ecosystem services, land use, decision support.

INTRODUCTION

This article describes the European experience on application of ecological risk assessment (ERA) in terrestrial ecosystems. Not unlike the case in Australia, in Europe, too, an urgent need is felt to bring together the existing knowledge in this area. A questionnaire held among all country representatives of CLARINET1 in order to list the use and needs for ecological risk assessment (ERA) within the European Union (EU) indicated that most respondents use or intend to use ecological reasoning in generic guidelines or site- specific assessments. It was concluded that a common European site- specific approach for ERA (SS-ERA) was needed for, given several uncertainties, such as extrapolation from "lab to field," non- homogeneity among test conditions, unreliability of models, controversies between opinions of experts, and lack of basic knowledge on soil biota. The EU has not yet developed quality standards for the terrestrial environment, contrary to the aquatic environment. Recent proposals in diis area include a EU workshop on classification of criteria (European Chemicals Bureau 1999), proposals from the Organisation for Economical Co-operation and Development(OECD 1994, 1995), Society for Environmental Toxicology and Chemistry (SETAC) workshops, and U.S. Environmental Protection Agency (USEPA) guidelines for ERA. There are more than 60 tools and protocols available for effect assessment. The relevance of these should be assessed, establishing programs for the comparison of results from laboratory and field studies. A workshop on ERA was therefore organized by the Ecology working group of CLARINET in preparation of a proposal for a European framework for site- specific risk assessment. This article will provide a short summary of the results of that workshop, it still being the most recent activity toward such a common framework that was undertaken in Europe. Further, I will present the basic approach for SS-ERA in The Netherlands against the background of recent changes in the Dutch policy for contaminated land and soil quality protection and management. The article will then illustrate a case study, focusing on the derivation of suitable ecological parameters and assessment criteria in view of land use in a tiered approach risk assessment.

CLARINET WORKSHOP ON ERA, ECORISK 2001

The workshop on Ecological Risk Assessment was convened by the Ecology working group of CLARINET in Nunspeet, The Netherlands, in spring 2001. The aim of the workshop was to recognize and discuss scientific developments, available tools, and policy needs regarding site-specific ecological risk assessment, and to combine these aspects in a proposal for a European framework for SS-ERA. Another goal was to identify gaps and needs for future development in this area.

The outcome of the 2001 EcoRisk workshop is reported in the proceedings (Schelwald 2001). Participants agreed that a framework is required to structure the process of risk assessment. A procedural framework will give guidance to uniformly perform ERA, so that quality is assured. A common European framework should be flexible, to facilitate the building in of specific details on a national basis. The approach should be tiered and decision oriented. It was recommended to keep things simple and to develop a management tool (framework) that can be used for a comprehensive ecological risk assessment. All stresses should be assessable, and ecological requirements for various land uses and functions should be addressed (ecological aspects in a suitability-for-use approach).

Bioassays and biological field data were considered important additional tools in ERA. Some OECD and International Standards Organisation (ISO) bioassay standards already have been developed that can be used in ERA (Rmbke, this issue). Depending on site and ecological targets, many other tests are available that are currently not under OECD and ISO regime, but are still considered useful in ERA. Promising methods with a potentially wide range for application should be validated with urgency.

It was recognized that the convincing of landowners to use ERA is a bigger problem than ERA itself. Public communication is considered important because the public perception of risk is crucial to the final approval of ERA. A scheme for interpretation of results from the various tools in terms of ecological impact was considered important but is currently lacking.

Common Points of View

* There is a (possible) need for SS-ERA in society,

* A common framework is needed, but it should be flexible,

* A framework should be cost-effective,

* Present or future land use is important,

* Historical data on past land use should be used,

* A framework should follow a tiered approach,

* Checklists are needed in the different tiers, for example, to check for relevant exposure routes and bioassays,

* A conceptual model should be part of the ERA in each tier,

* Generic values should be used in a first tier,

* Bioavailability is an important issue that requires attention in SS-ERA,

* Bioassays were recognized as valuable tools to be used in different tiers,

* Negotiation between all stakeholding parties is important in order to come to broadly accepted conclusions on the results of the risk assessment and the subsequent actions to be taken in risk management,

* There is urgent need for biological reference values (specific to soils and regions) . Proper references for SS-ERA are often lacking, whereas natural ranges for biological parameters are needed for criteria setting in the assessment of risks.

Divergent Views

* Nature of flexibility in the approach; should flexibility be found, for example, in site-specific refinements, in which tools to apply, and so on?

* Generic targets for soil quality are to be used in Tier 1, but perhaps other tools can be used as well, as long as these are cost- effective. How generic should these targets be; for example, should soil organic matter be considered, and should generic values be worst case or realistic?

* Conceptual model: in which tier should it be defined, and to what detail?

* Bioavailability is an important issue, but when and in which tier should it be taken into account, and to what detail? On the basis of reviews, experiments, or extrapolation of results?

* Bioassays: when to apply, in what detail, how can results be interpreted?

* Should groundwater be considered? Very little is known on this topic.

* What should be the targets for protection?

* Should other stressors be taken into account?

* When, and in which tier, should stakeholder negotiations be started?

* How to convince the public/stakeholders to continue into a next tier or not?

* Validation: how and when?

FINAL CONCLUSIONS FROM THE CLARINET WORKSHOP

On the one hand there was agreement on the outline of a EU- framework on site-specific ecological risk assessment. On the other hand many details were not yet filled in or had not even been discussed at all. From these two facts it can be concluded that there is a good basis for filling in the ERA details in future and ongoing discussion was recommended. The participants agreed that the tiered approach resulting from the CLARINET workshop should be developed further. The American Society for Testing and Materials' Standard Guide for Risk-Based Corrective Action (RBCA, "Rebecca") (ASTM 1995) is advocated by the USEPA as a good starting point for the development of a risk-based process for implementing agencies. RBCA, originally developed for petroleum storage tanks, is in its current form a three-tiered approach for the development of cleanup objectives that are protective of human health and the environment, while taking into account site-specific conditions that include future land use, institutional controls, engineering controls, and other factors. Workshop participants considered it a good tool\, and reinvention of the wheel may be largely avoided by adopting and reshaping to the European taste. The scale of the contaminated area obviously is important, and focus should be put first on the most serious problems; analysis effort should be adjusted to the scale of the site. At the beginning of ERA, historical research should be carried out (which pollutants, land use history, comparable accidents, etc.). After that, a tiered approach may be followed (Figure 1 ). The first screening assessment should include all priority chemicals.

The interpretation of results from bioassays was considered very important in the development of a European framework for SS-ERA. The development of bioassays and interpretation of results can be taken up by existing networks and organizations such as the ISO. The current guidance document (ISO/DIS 15799) on the use of test methods for ecotoxicological investigations of contaminated sites does not give guidance for interpretation of results, nor to the choice of specific test methods in specific situations. The discussion in Europe has been focused on multifunctionality (nature). Ecological requirements for other types of land use than nature should be defined.

THE DUTCH APPROACH TO SS-ERA

Subsequent to the 2001 CLARINET workshop, few activities have been initiated to further a common European framework for ERA, although a special session was devoted to this topic during the 2003 International Conference on Contaminated Soil (Van Wensem 2003). The attention of ecological risk assessment in different EU-countries is focused on further development of techniques for SS-ERA. With respect to gaps in knowledge that were pointed out earlier, scientific progression is being made since. For example, the usefulness and ecological relevance of measures of bioavailability is being evaluated by correlation to ecotoxicological studies with soil and water organisms and with changes in ecosystem structure observed at field sites with mixed pollution. This should contribute to a scientific basis for adequately using bioavailability in ERA (Jensen 2003). Also, the feasibility of bioassays in SS-ERA has been improved as new techniques continuously become available, and others have been further developed and standardized (Rmbke and Weeks 2003). Further, experience is being accumulated on stakeholder negotiations before and during the actual risk assessment as to what to investigate and measure, and how to assess the results (Faber 2003). In addition, the implementation of SS-ERA as a regulatory tool is gaining insight with respect to the use of existing techniques for decision-making, and of the translation of science into policy in general (Crommentuijn 2003). In the remaining part of this article the Dutch approach to SS-ERA will be presented in short, to be followed by a case study of implementation, emphasizing the interactive process between stakeholders and the attitude toward site-specific references and criteria for assessment.

Figure 1. Framework for site-specific ecological risk assessment, as designed by participants to the CLARINET workshop. The conceptual model refers to the recognition site-specific speciation of contaminants, exposure routes, and relevant ecological receptors (after Crommentuijn etal 2002).

As a result of recent changes in the Dutch soil protection policy (Minister of Housing, Spatial Planning and the Environment 1999), the need for site-specific risk assessment has increased through a number of options. Soil clean-up and remediation projects may be prioritized over various polluted sites by the use of site-specific risk assessment techniques, and soil remediation and management measures at polluted sites can be adjusted in view of land use on the basis of such techniques. Also, land use can be adjusted according to soil quality on the basis of site-specific risk assessment. A procedure for SS-ERA was developed in the late nineties (Rutgers et al. 2001). This basic approach focuses on effects rather than risks, and includes multidisciplinary parameters from environmental chemistry, toxicology, and ecology to provide multiple weight of evidence (Figure 2). The type of land use largely affects the selection of parameters, as a particular use may demand specific services from the ecosystem, which requires relevant testing methods. Moreover, the approach is characterized by repetitive interactions between stakeholders and researching consultants, in particular with respect to the choice of risk parameters and criteria to assess the results. As a result of these interactions, site-specific risk assessments and the decisions based on them may become more acceptable to these stakeholders and the public.

Figure 2. Basic approach to site-specific ecological risk assessment. The derivation of ecological assessment tools is developed in three stages in interaction between risk assessor and stakeholding parties (after Rutgers et al. 2001).

There is no such thing as "the ecological risk" of soil pollution. From a society point of view specific ecological risks may be recognized in relation to land use at the site and in the immediate surroundings. The functioning of the local ecosystem may be threatened in such a way that the quality or quantity of ecosystem services to society (if not ecosystem values per se) is reduced (Technical Committee on Soil Protection 2003). As a result, damage would be experienced by the stakeholding parties to a particularly affected ecosystem service, either in terms of economic losses, or risks to health and well-being of the individual. It would therefore make sense in ecological risk assessments to make use of study parameters with direct interpretability to ecosystems services of relevance. Land use may therefore be a key factor for the type of tests and inventories to be selected for risk assessment.

Given a particular use of a polluted site (either in the present or in the future), ecological aspects of the local ecosystem can be derived that are conditional to the particular targets of land use, as desired by the stakeholder. Such ecological aspects usually comprise soil processes or the presence and interactions between particular species, as these may largely determine the life support functions of the soil ecosystem. The recognition of relevant ecological aspects is a recommended step of interaction between the risk assessor and the stakeholder (Figure 2).

In The Netherlands, Stage 2 is usually the first stage at which a risk assessor becomes involved. Government parties and other stakeholders have already taken the decisions on land uses and their specific objectives at an earlier stage. Ideally however, risk- assessing consultants would be involved earlier in the process. From Stage 2 a further step is then taken toward the definition of a set of tools appropriate for the ecological aspects, which will enable the evaluation of the risks to ecological functioning in view of the desired ecosystem services. A tool set will ideally consist of several measurable or calculable indicators and parameters for soil quality, in order to establish present and future effects through site-specific assessment studies (rather than use of non-specific data). The results of the site-specific studies will then be assessed on the basis of previously determined criteria, thus facilitating clear-cut policy and management decisions whether to accept any demonstrated extent of effects in view of the intended land use.

A case STUDY

In practice this basic approach was followed for the first time in an ecological risk assessment against a background of testing the assumptions underlying a soil management plan for a rural area polluted at large scale. The area in question is called Krimpenerwaard, and comprises 13,500 ha of a polder area in the Dutch province Zuid-Holland (South Holland), forming a substantial part of the "Green Heart" of Holland. Land use is predominantly agriculture (85%, mostly dairy farming) and nature (2% at present, 20% in future), intermitted with roads, waterways, and settlements. In this peat meadow polder landscape some 5000 ditches have been filled with an array of wastes in the 1950s to late 1980s. The sources of these wastes range from local households and waterway sludge to industrial wastes and car shredders. Some of these wastes have been shown to contain excessive concentrations of heavy metals, cyanides, PAH, or chlorinated hydrocarbons, and according to law several sites must be qualified as seriously polluted and requiring remediation or clean-up. However, the distribution of these waste types in the individual ditches over the entire area is mostly unknown, and the Krimpenerwaard as a whole is treated as a single case of serious soil pollution.

Two rural redevelopment planning programs aimed at conservation and reinforcement of green functions, such as nature, agriculture, and recreation, were largely obstructed as a result of soil pollution, as were private land and soil transactions. As much as 13 stakeholding parties constructed a soil management plan, and a foundation was formed to facilitate its implementation. The soil management plan aims at a "functional clean-up" in view of land use, by means of covering "suspected" categories of wastes with a 30-cm layer of local type soil ( "capping"). In support of this management, extensive studies were conducted to verify the assumptions in the soil management plan regarding the existence of possible undesirable effects induced by the various waste categories and cover materials. These studies addressed effects to agriculture, "ecology," and environmental transport of contaminants, and were made up of three consecutive phases and a monitoring phase.

The ecological risk assessment itself followed a tiered approach, including a screening for bioavailable contaminants, a testing for general effects by use of standardized bioassays and field \inventories, and a survey of specific effects on natural and agricultural ecosystem services. Further, site-specific effects, if demonstrated in lower tiers, were scaled up to the entire region in higher tiers. Contaminants were shown to be present in bioavailable concentrations in all suspected categories of waste, and consecutively effects were demonstrated in standard bioassay tests. This article does not discuss these lower tier results, however, but briefly focuses on the process of defining these higher tier studies and the iterative discussions with stakeholding parties that are involved. It discusses how research goals were set in view of land use, and how suitable parameters in the consecutive tiers were derived. Also, some experiences are presented with respect to the determination of agreeable criteria to assess forthcoming results in a multistakeholder situation.

In the case of the Krimpenerwaard, the aforementioned generic approach was applied to test the suitability of the intentional measure for soil management; that is, coverage of suspected waste categories by 30 cm soil. It was questioned whether this measure would be sufficient to acceptably reduce harmful effects to the ecosystem in terms of ecological aspects for nature and agricultural and recreational land use. It was diought that two mechanisms could potentially cause a renewed exposure of the aboveground ecosystem after soil management measures would have been taken:

a. Uptake by deep rooting plants and allocation to aboveground parts,

b. Bioturbation and mixing of contaminants into the cover layer.

Two routes of exposure of the ecosystem were considered to reflect these mechanisms:

a. Soil-plant-insect herbivores-bird predators, and

b. Soil-burrowing earthworms-meadow birds.

Ecological aspects were then derived from land use targets in interaction with stakeholders in the Krimpenerwaard region (Table 1).

Table 1. Land use targets and ecological aspects, and outlines for potential indicators and parameters in the Krimpenerwaard case.

Aspects were preferred if they were representative of multiple targets and land use types to give meet constraints of time and budget. Therefore, not every aspect was chosen for assessment studies eventually, even if so proposed by a stakeholder. The table is focused on biological parameters in the higher tier risk assessment; chemical information (such as substance concentrations and "bioavailability") has been left out. These have been applied predominantly in earlier tiers for screening purposes.

Assessment Criteria

In interaction with Krimpenerwaard stakeholders, risk parameters were selected and criteria were developed for the interpretation of results. In relation to the development of assessment criteria, it was discussed what references were to be used. A site-specific definition and, if possible, measurement of reference values was preferred over the use of some generic values. This is related to the complexity of ecosystems in general and local variability in particular. Any framework for the level at which ecological processes have to be protected in relation to a particular land use is presently lacking. Research in this direction is still at an exploratory stage (Faber 1998; Van Hesteren et al. 1998). In the Krimpenerwaard case study, most stakeholders in nature development and agricultural land use showed preference for in situ field references sampled in meadow grassland adjacent to disposal sites or partial regions within the Krimpenerwaard region, rather than determining a region-specific reference value. Both these references were preferred over a value derived from some other peat meadow region. Furthermore, the stakeholders indicated that for decision, making on the basis of ERA only ecologically relevant aberrations from the reference would be taken in consideration, even when not statistically significant, whereas minor differences from a reference (ecologically irrelevant) would not be taken into account, however statistically significant. One stakeholder indicated that he was prepared to accept α = 0.10 for type I errors in statistical analyses.

Results for field tests and inventories should be assessed against their windows of natural variation. Reference and criteria- setting therefore require a thorough knowledge of these study parameters, particularly if these should be studied over a single season. Monitoring may then be desirable or even necessary for future feedback on the decision following the risk assessment (Figure 2).

Figure 3. Site-specific testing in the Krimpenerwaard case, using distinct critical percentiles in view of land use (only right-sided criteria are shown).

In summary, the assessment criteria were decided to be based on one-sided statistical testing for negative effects in risk parameters against in situ field references. Testing every category of suspect waste materials separately, a standard threshold was used for type I errors (α = 0.05) with respect to nature conservation land use, and a less sensitive threshold (α = 0.025) for agricultural land use. Because sampling numbers were low, site-specific values were further analyzed if no deviation from the reference was observed for the entire data. Twofold more sensitive thresholds were used in two-sided tests against critical percentiles of the reference (Figure 3). The percentiles reflected the desirable degree of protection for particular types of land use, as negotiated with stakeholders.2

CONCLUSIONS

1. A common European framework for ecological risk assessment seems desirable.

2. In ecological risk assessment a greater relevance of results and greater acceptability to the stakeholders can be achieved by deriving research parameters directly from land use objectives and underlying ecological aspects.

3. It seems possible to differentiate effect criteria in view of land use; in our case effect criteria for any particular test parameter were chosen less protective for agricultural land than for nature development and conservation areas. On a wider scale either type of land use may be considered relatively, sensitive.

4. In a multistakeholder situation the assessment can be complicated by divergent views on criteria for ecologically acceptable effect limits; negotiations should preferably be completed before data are collected.

5. Higher tier field studies may require special attention in setting references and criteria, given a relative high natural variability and a limited timeframe to establish results.

ACKNOWLEDGMENTS

Trudie Crommentuijn (Ministry of Housing, Spatial Planning, and the Environment, The Netherlands) and Joke van Wensem (Technical Committee on Soil Protection, The Netherlands) are gratefully acknowledged for their support for this article. The Krimpenerwaard study was financed by Stichting Kennisontwikkeling en Kennisoverdracht Bodem (SKLB), Stichting Bodembeheer Krimpenerwaard (SBK), and the Dutch Ministry of Agriculture, Nature Management and Fisheries through DWK program 396 Soil Quality and Management.

1 CLARINET (Contaminated LAnd Rehabilitation Network for Environmental Technologies) was a Concerted Action within the Environment and Climate Programme of the European Commission DG Research, co-ordinated by the Austrian Environment Agency. The network ran as a EU-initiative for knowledge transfer between 1998 and 2001.

2 In the final decision-making no distinction was maintained between land uses, and all risks were assessed using criteria as established for nature.

REFERENCES

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Crommentuijn T. 2003. Implementation of SS-ERA as a regulatory tool; what to take into consideration. In: Conference Proceedings of 8th International FZK//TNO Conference on Contaminated Soil, pp 3500- 3601. Ghent, Belgium, 12-16 May

Crommentuijn T, Bierkens J, Herrchen M, et al. 2002. Ecological risk assessment for contaminated sites in Europe-ecorisk conclusions. In: Kasamas H, Kiss G, Moser B, et al. (eds), Proceedings of the CLARINET Final Conference Sustainable Management of Contaminated Land, pp 78-80. Vienna, Austria. 21-22 June 2001. Available at http://www.clarinet.at/ library/ proceedings_finalconf.pdf

European Chemicals Bureau. 1999. Proceedings of the international workshop on hazard identification systems and the development of classification criteria for the terrestrial environment. "Approaches for a hazard identification-classification system for the terrestrial environment." Ispra, Italy

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Minister of Housing, Spatial Planning and the Environment. 1999. Interdepartmental policy review: soil remediation. Letter from the minister containing the government statement relating to the function-oriented and cost effective approach to soil pollution. Parliamentary Proceedings 1999-2000, 25411, no. 7, Lower House. Available at http://www2.vrom.nl/ Docs/internationaal/ briefVTNZPronk.pdf

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Rmbke J and Weeks J. 2003. The feasibility of bioassays in site- specific ecological risk assessment (SS-ERA). In: \Proceedings of 8th International FZK//TNO Conference on Contaminated Soil, pp 3601- 5. Ghent, Belgium. 12-16 May

Rutgers M, Faber J, Postma J, et al. 2001. Site-Specific Ecological Risks-A Basic Approach to Function-Specific Assessment of Soil Pollution. Netherlands Integrated Soil Research Programme Reports, nr 16, English version nr 28. Wageningen, The Netherlands. Available at http://www.clarinet.at/library/nl-specif.ecol.pdf

Schelwald R. 2001. Proceedings of the CLARINET Workshop on Ecological Risk Assessment, S-TEC 2001. Nunspeet, The Netherlands. 17-19 April

Technical Committee on Soil Protection. 2003. Advice To a more ecologically sustainable land use. TCB A33(2003). Available at http:/ /www.tcbodem.nl/publicaties/categorien/pdL files/ A33-2003-eng.pdf

Van Hesteren S, Van de Leemkule MA, and Pruiksma MA. 1998. Minimum Soil Quality: A Use-Based Approach from an Ecological Perspective-Part 1: Metals. Technical Committee on Soil Protection. Report R08 (1998), The Hague, The Netherlands. Available at http:// www.clarinet.at/library/Joop-paper-WEBJ.pdf

Van Wensem J. 2003. Introduction to special session 5: site specific ecological risk assessment; where are we now? In: Proceedings of 8th International FZK//TNO Conference on Contaminated Soil, p 3589. Gent, Belgium, 12-16 May

Jack H. Faber

Alterra, Wageningen University and Research Centre, 6700 AA Wageningen, The Netherlands

Address correspondence to Jack H. Faber, Alterra, Wageningen University and Research Centre. P.O. Box 47. 6700 AA Waeenineren. The Netherlands. E-mail: lack.Faber@wur.nl

Copyright Taylor & Francis Ltd. Feb 2006

Source: Human and Ecological Risk Assessment

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