Introduction to Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 616

(bacterial population density and composition and structure) diversity of the soil
bacterial community as indicator of Soil Health. The indicators that optimally dif-
ferentiated the extent of soil remediation for a former gas works site in the UK were
biomass-C, respiration, dehydrogenase activity, earthworm toxicity and mustard
seed germination (Dawson et al. 2007 ). The authors also concluded that once robust
and sensitive biological indicators were incorporated into a quantitative soil quality
index, although they had different endpoints, they gave a clearer representation of
Ecological Health than chemical data alone by their integration of contamination
effects at a number of trophic levels. Hankard et al. ( 2004 ) investigated the perfor-
mance of two earthworm biomarkers, these are, lysosomal membrane stability and
the total immune activity (TIA), with the purpose to assess the impact of a range of
metals and organic contaminants in soils in three industrial sites in the UK. More
examples are given in Breure et al. ( 2005 ) and Rutgers et al. ( 2008 ).
Bioindicators can also be used for other purposes than assessing the impact of soil
contamination. Ötvös et al. ( 2003 ), for example, used moss species as bioindicators
for the impact of atmospheric deposition of several metals, in Hungary.
13.9.2 Significance of Monitoring the Soil Ecosystem Quality
When 'sustainable Ecosystem Services' is earmarked as a policy goal, monitoring
becomes increasingly important in assessing ecological quality and in determining
the effectiveness of the measures taken. Ecosystem monitoring should consist of
the integrated measurement of the chemical, physical and biological characteristics
of the soil. It has been applied in agriculture, for instance, in order to determine
the necessity of the application of fertilizer or to determine the presence of pest
organisms such as plant predatory nematodes of the fungus Phytophtera infestans .
Monitoring is also useful for assessing the impact of soil contamination and other
stress factors on the soil ecosystem (see also Section 13.5.5 ). In the era of sustain-
ability, the need for ecological soil indicators has gained enormously in terms of
interest.
Determination of the actual ecological quality of a soil is also necessary, for
example, in site-specific Ecological Risk Assessment, where not only the extent of
contamination, but also the effects of contaminants on the ecosystem are taken into
account in making the decision on how to manage a site.
The Spanish regulations for assessing and managing contaminated sites, released
in 2005, include direct ecological toxicity testing for the purpose of assessing the
ecological effects of soil contamination (Tarazona et al. 2005 ). For this purpose,
specific soil microcosms are in development (Fernández et al. 2005 ).
13.9.3 Possibilities for Monitoring
As mentioned earlier, many biological measurements are possible based on the
determination of the presence or absence of organisms, or on the measurement