Environmental Engineering Reference
In-Depth Information
respective site. However, it is important to involve a wide range of stakeholders
early in the process, in order to reach a mutual understanding and acceptance of the
conceptual site model for the terrestrial ecosystem, including the target of protection
and means of successful risk mitigation prior to initiating any actual investiga-
tions. Stakeholder involvement should therefore include contaminated-site experts
from authorities, land users and land managers/owners. The team of risk asses-
sors should include people from academia and consultancies, capable of performing
ERA, covering various field of expertise.
The Steering committee should then, in alliance with the risk assessors, deter-
mine the land use as the
4th step
in the ERA. Subsequently, the actual site-specific
Risk Assessment is initiated as the
5th step
of the ERA by identifying the ecolog-
ical requirements related to the specific land use (5a). In the subsequent steps (5b,
5c and 5d), a listing of relevant assessment endpoints for each of the identified eco-
logical requirements needs to be identified and agreed upon, i.e. if nutrient cycles
and plant biodiversity are considered important in relation to this specific land use,
a suite of tools, bioassays or monitoring end-points should address the related end-
points. Examples of relevant assessment endpoints, like sensitive crops, key species,
decomposition and nutrient cycles for various land uses can be found in Jensen and
Mesman (
2006
).
15.2 Working Hypotheses, Definition of Conceptual Models
and ERA Frameworks
Contributions from and interactions by risk assessors and risk managers are essential
in the definition of the conceptual model and working hypotheses. In the concep-
tual model a simplification of the real system is obtained in order to frame the
results of the Risk Assessment. The conceptual model contains two key elements
(US-EPA
1998
): (i) a set of working hypotheses and (ii) a diagram representing
the links between the working hypotheses. Consequently, the conceptual model
sets the limits of the ERA. Terrestrial ecosystems are complex and dynamic sys-
tems. It therefore requires a well elaborated conceptual model to reduce complexity
and integrate system attributes in order to develop clear solutions and management
decisions. A unifying ecosystem theory is lacking, for example, making the selec-
tion of assessment end-points difficult. ERA can focus on specific endpoints, like
the protection of particular species (e.g. endangered species, wild life) or the per-
formance of Ecosystem Services of the soil system (e.g. nutrient cycling, Natural
Attenuation, water retention, etc). However, ERA can in principle also cover risks
derived from a more ethical perspective of environmental protection. Consequently,
all biotic elements will be potentially useful to some extent.
Working hypotheses are specific assumptions about potential risk to assessment
endpoints (US-EPA
1998
). They are formulated on the basis of one or more infor-
mation sources like contamination history and data, professional judgments and
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