Introduction to Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 606

• the USEPA Region 4 (US Environmental Protection Agency ( 2001 ); 132

contaminants);

• the Texas Natural Resource Conservation Commission (Texas Natural Resource

Conservation Commission ( 2001 ); 63 contaminants);

• the USEPA Office of Emergency and Remedial Response (US Environmental

Protection Agency ( 2003 ); nine contaminants).

In Posthuma and Suter ( Chapter 14 of this topic) a detailed overview is given of
the position of Species Sensitivity Distributions (SSDs) and Functions Sensitivity
Distributions (FSDs) with regard to the derivation and use of Soil Quality Standards.

13.6.3 Site-Specific Risk Assessment

Site-specific Ecological Risk Assessment has undergone extensive development in
a few countries in Europe, in the USA and Canada, ever since it was targeted as an
important gap in Ecological Risk Assessment at the end of the 1990s. Today, a few
promising methodologies exist that can rely on a few years of using and testing. One
of the pitfalls, however, is that many site-specific ecological procedures focus on a
single species (the single-species approach).
In the most appropriate and efficient approach for site-specific Ecological Risk
Assessment, these tools are used in a tiered approach as for any other protection
target. In a tiered approach the assessment becomes more site-specific and less
conservative, and hence more complex, tier by tier. The motto is: simple when
possible and complex when needed. An elegant procedure concerns the so-called
TRIAD approach (Jensen and Mesman 2006 ). In this approach, the status of three
different elements that relate to ecological damage, namely, of the soil chemistry,
toxicology and ecology, is investigated ( multiple weight of evidence ). In Rutgers
and Jensen ( Chapter 15 of this topic) the TRIAD approach is described in detail.
Moreover, Chapter 15 includes a detailed overview of the theory and procedures for
site-specific Ecological Risk Assessment, in general.

13.7 A Closer Look into Ecological Risk Assessment

13.7.1 Resilience and Recovery

Recovery often refers to the ability to return to a previous condition, that is, the con-
dition before exposure to contaminants in the soil took place, when this condition
has weakened or at least seriously has been deteriorated. Resilience can be defined
as the speed of return to this previous condition or as the magnitude of disturbance
that the ecosystem can absorb. Resilience and recovery are often, but not always,
related to each other. Since both capabilities support the functioning of the ecosys-
tem as a whole, including the Ecosystem Services and, hence, indirectly support