Risk management of chemicals and contaminated land – from planning to verification - Environmental Deterioration and Contamination: Problems and their Management - page 272

with a wider contextual ecosystem should also be investigated and taken into
consideration.
Indicator species should be selected and characterized because it is impossible
to assess all ecosystem components. The selection of the indicator species requires
good general and site-specific knowledge of the composition of the local ecosystem
and on the interaction between the species. Properly selected indicators represent the
ecosystem truly, and can serve as a basis for extrapolation.
Further simplification of the ecosystem may be a mesocosm or a microcosm or just
a few species from three different trophic levels. Better controllability of the artificial
setups may compensate for the disadvantages of the reduction in size and simplification
of the system.
4.5 Environmental risk assessment tools
Exposure assessment in a generic RA procedure is carried out by modeling the trans-
port and fate of chemicals in an environment characterized by default environmental
characteristics. Site-specific exposure can also be the result of a model calculation, but
in this case site assessment results are the input data of the model. The starting point of
the transport model is the amount of chemicals produced or used and the real amount
of contaminants (e.g., waste) emitted into the environment.
Environmental risk of chemicals can be calculated in a prospective way in the
design phase before the start of their production. RA of contaminated sites may be
retrospective (the chemical substance has already been discharged into the environ-
ment and has reached the receptors), or prospective (risk posed by the contaminated
site as a source of future contamination). Based on these considerations, models and
measured data or their combination can be applied for risk assessment of chemicals
and contaminated sites.
Modeling transport and fate of chemicals indicates the changes in quantity and
quality of contaminants between the source and the site where the risk is measured
(Chapter 2 in Volume 2). Exposure can be measured directly in the environmental
compartments and phases, and tissues of exposed organisms by physico-chemical ana-
lytical methods (Chapter 8 in Volume 2). As an alternative, the adverse effects of
the contaminants in the environment, or rather the adverse effect of the contami-
nated environmental medium can also be measured directly. The following tools are
used: monitoring and assessing abnormal/unhealthy diversity of aquatic, benthic or
soil ecosystems (a valid evaluation reference is needed), missing vegetation or habi-
tation, and certain organisms' disappearance in the area. To characterize the scale of
risk, direct toxicity can be measured by in situ or laboratory bioassays, microcosms
and mesocosms (Chapters 3-5 in Volume 2).
The environment is a complex of living and nonliving systems in a multimedia
and multiphase system with an infinite number of interactions. Modeling all the char-
acteristics and interactions is impossible. Direct fate and effect testing has proved to
be more efficient in many contamination cases. Fully model-based retrospective ERA
should be validated in both site-specific and generic risk management cases.
ERA plays a priority role in risk management and ERR of contaminated sites. The
risk value determines whether or not RR is necessary, and how urgent the intervention
is. Technology monitoring and ERA during the remediation of contaminated water,