Introduction to Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 604

'weight of evidence' approach (Weeks and Comber 2005 ). This includes the impact
on ecological soil functions (Römbke et al. 2005 ). In Europe, 11 countries con-
sider the protection of ecological receptors, although only in a few of them formal
ecological Soil Quality Standards have been adopted (Carlon and Swartjes 2007 ).
In Canada, federal ecological Soil Quality Standards for 87 contaminants
were launched in 1999 (Canadian Council of Ministers of the Environment
1999 ). Australia established ecological Soil Quality Standards in 2003 (National
Environmental Protection Council 2003 ).

13.6 Ecological Risk Assessment in Practice

13.6.1 Soil Quality Assessment

Ecological Risk Assessment is an important process in dealing with contaminated
sites. Like all other Risk Assessment tools, Ecological Risk Assessment tools can
be used for Risk Characterisation (risk appraisal for existing contaminated sites;
see Section 1.5.3 ) and for Risk Management (recovery of soil quality). Although
Ecological Risk Assessment tools do not have a long history when compared to
Human Health Risk Assessment tools, there are many sophisticated Ecological Risk
Assessment tools available today, worldwide (see, e.g., Carlon and Swartjes ( 2007 )
for an overview of ecological risk tools in the European Union). Many of these
tools have been intensively used, tested and validated. Ecological Risk Assessment
tools share several characteristics with Human Health Risk Assessment tools, for
example:

• They have a limited reliability, since soil ecology is characterized by a huge

temporal and spatial variability and the quantitative extent of many ecological
processes are largely unknown.

• Worldwide, many different tools exist for similar purposes.

In spite of the limited reliability, Ecological Risk Assessment is an extremely
useful process for understanding the threats to the soil ecosystem from soil con-
tamination and supporting decisions on contaminated sites. However, a meaningful
Risk Assessment requires that risk assessors be aware of the limitations. They must
strive after a smart balance between relatively unreliable outcomes, and concrete
and practical conclusions. Therefore, risk assessors have an important responsibil-
ity in communicating the outcomes of Ecological Risk Assessments, both in terms
of scientific meaning and as restrictions.
So far, Ecological Risk Assessment has been based on statistical techniques that
do not take into account the interactions between organisms and the relative impor-
tance of specific organisms for the realisation of soil processes. In the majority of
the present models, organisms do not interact and they all have the same ecological
importance.