Introduction to Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 585

is an important criterion for the functioning of the soil ecosystem, or in other words,
is an indicator of the quality of Ecosystem Services.
13.4.3 Ecosystem Services
13.4.3.1 The Significance of Ecosystem Services
As described in Section 13.1.2 ,theterm Ecosystem Services refers to the benefits
of ecological functions for the life of humans. Obviously, although the focus in this
Section is on human benefits, organisms perform Ecosystem Services for their own
well-being. They perform these tasks for feeding and, hence, for their energy supply,
growth and reproduction. Generally speaking, huge numbers of organisms feed on
large numbers of other organisms, their waste products, and the substances they
release such as vitamins, amino acids and sugars.
In soil ecosystems, processes take place including the exchange of energy and
chemical compounds between organisms and their environment. These processes
lead to environmental circumstances that enable the existence of plants, bushes and
trees. The overall Ecosystem Service related to these processes is the provision of
agriculture and hence food, a prerequisite for human survival. Moreover, soil organ-
isms are thus responsible for the existence of nature and green elements in urban
areas. Organisms regulate the cycling of many important components. They are
engaged in the element cycles and produce nutrients for plant growth in the carbon,
nitrogen, and sulphur cycles, such as ammonia, nitrate, sulphate, and carbon diox-
ide. In aerobic soils, one important process is oxidation, and its main products are
carbon dioxide and water. In anaerobic soils, microorganisms cannot use oxygen as
an electron acceptor and instead use nitrate, sulphate or even organic contaminants,
producing nitrogen, sulphide, carbon dioxide and methane. Although all these pro-
cesses are performed by these organisms in their own interest, they are of invaluable
importance to human life.
The significance of the processes performed by soil ecosystems can best be
understood by investigating the performance of 'natural soils', that is, soils that
have not been touched by human hands or machines, such as forest soils or prairie
soils. Often these soils harbour a healthy ecosystem, since these soils are tilled and
fertilized solely by the soil organisms.
In the Millennium Ecosystem Assessment ( 2005 ) a wide range of Ecosystem
Services is listed, including provisioning services (e.g., the provision of medicines),
regulating services (e.g., climate regulation), cultural services (e.g., recreation) and
supporting services (e.g., soil formation). The value of several novel Ecosystem
Services is under investigation, such as the ability of some soil fungi to produce
iron chelators capable of extracting iron from crocidolite (blue asbestos), signifi-
cantly reducing the potential to generate radicals and to damage DNA in the human
body (Martino et al. 2004 ). Another example of an emerging Ecosystem Service
focuses on the physical ground improvement methods with regard to the bearing
power. Van Paassen ( 2009 ), for example, developed a novel ground improvement
method, based on precipitation of calcium carbonate crystals (MICP) induced by