Environmental Engineering Reference
In-Depth Information
Monitoring ecological response to pollution
If we are to determine the impacts of pollutants upon ecosystems and their
recovery following remediation, it is absolutely essential that we have a robust
method of monitoring. There have been significant advances in the methods
of monitoring freshwater systems, details of which are provided in Jones et al.
(
Chapter 6
); however, it is clear that there are several challenges to be met.
The first of these is to define what is meant by the term 'reference condition'.
It is a term used in many key pieces of legislation (including the WFD) to assess
an ecological community in relation to the community that is expected to be
present based on 'reference conditions'. However, due to the extent of human
impact both on a temporal and spatial scale it is difficult to find a 'real'
example of this, or to model one. It is the general consensus that, when
tackling pollution within the environment, the aim is not to attain a reference
condition that reflects pre-industrial conditions (
Chapter 6
) but rather to
achieve high quality and sustainable water resources. However, as Gell points
out (
Chapter 8
), it may be preferable to have pre-industrial baseline targets due
to future risks from pollutants (in the form of sediments) on the longevity of
a system (current evaluation of status shows little divergence from a standard
reference condition). The relative value of monitoring against some ideal
ecological community is a concept that is clearly questionable.
There has been far less progress in the ecological monitoring of either land or
marine environments in terms of ecological impacts. It is suggested that, rather
than using a similar system used for freshwaters where the physical environ-
ment is very different, for marine environments sediment toxicity testing to
monitor lethal and more importantly sub-lethal effects would be more benefi-
cial (
Chapter 7
). This idea that sub-lethal effects may be of critical importance
is also highlighted in other systems where there is a need for new toxicity tests
for emerging contaminants due to the inappropriate nature of existing tests
that lack subtle endpoints (
Chapter 5
). The assessment of land contamination
is notoriously difficult due to the extremely heterogeneous nature of soils
which strongly control the bioavailability of contaminants. There has been some
attempt to assess contamination using chemical approaches (production of Soil
Guideline Values for a number of contaminants), but the limitations of these are
extensive, and there is little if any link to the ecology of the area. Recent work
has made progress in providing a much clearer link between land contami-
nation and associated communities using a risk-based approach (
Chapter 9
),
and the success of this approach will be monitored in forthcoming years.
Remediation and ecological recovery
We now return to the previous question of 'reference conditions'. Whenever
the remediation of a contaminated site and its associated ecological recovery is
considered, a 'target' must be defined by which the remediation activity can be
