Environmental Engineering Reference
In-Depth Information
It is not easy to incorporate ecological insight into routine Risk Assessment,
but research on that subject is on its way. This research is now focussing on food
web modelling based on monitoring data, which in the future should lead to Risk
Assessment tools based on these ecological insights (e.g., Breure et al. 2008 ; Mulder
et al. 2005 ).
A way to account with uncertainties in Ecological Risk Assessment is following
a probabilistic approach. An example is given in Jager et al. ( 2001 ), who calculated
probability density distributions of the PEC/PNEC (Predicted Effect Concentration,
representing exposure divided by Predicted Non-Effect Concentration, represent-
ing effects) ratios for dibutylphthalate. The authors concluded that the deterministic
PEC/PNEC ratios are worst case, generally higher than the 95th percentile. The dis-
advantage of a probabilistic approach is that a policy choice needs to be made for
the level of acceptability, in terms of a specific percentile of the probability density
function of the PEC/PNEC ratio. Although this offers a more sophisticated way of
dealing with acceptable risks, there are no objective criteria to underpin this choice.
13.6.2 Soil Quality Standards
Statistical relationships between the soil concentration of contaminants and the frac-
tion of species potentially affected in a contaminated soil are available ( Species
Sensitivity Distributions; SSDs ). Analogously, relationships between soil concentra-
tion and the fraction of Ecosystem Services potentially affected in a contaminated
soil are available ( Functions Sensitivity Distributions; FSDs ). Based on these rela-
tionships, soil concentrations can be derived which relate to a specified percentage
of the fraction that is (potentially) affected and which can be selected as Soil Quality
Standards.
It is the task of decision-makers to define the protection level, that is, the percent-
age of the affected fraction that is acceptable. However, since it is difficult to arrive
at any insight into the consequences of the loss of a specific fraction of the organ-
isms, or Ecosystem Services, this decision must be made in close cooperation with
eco(toxico)logical experts. Examples of ecologically-based Soil Quality Standards
are given in Verbruggen et al. ( 2001 ) for the Netherlands and in Fishwick ( 2004 )
for the UK. In the United States, there are several bodies that derived ecological
Soil Quality Standards within a time span of seven years, doing this around the year
2000 (Barron and Wharton 2005 ), for example:
the Oakridge National Laboratory (Efroymson et al. 1997 ; 54 contaminants);
the New York State Department of Environmental Conservatism (NYSDEC
1998 ; three contaminants);
the USEPA Region 5 (US Environmental Protection Agency ( 1999 ); 215
contaminants);
the Oregon Department of Environmental Quality (Oregon Department of
Environmental Quality ( 2001 ); 137 contaminants);
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