Management of abandoned and contaminated land - Environmental Deterioration and Contamination: Problems and their Management - page 182

The identification of the source is relatively easy at sites contaminated from point
sources, but multiple point sources or diffuse sources make the risk assessment and
management more complex (see also Chapter 9). Even the identification of one source
may cause problems at an inherited abandoned site as information is often missing on
the original situation and the undocumented changes while the site was not in use.
The source is not identical with the contaminant itself. One source may be respon-
sible for dozens of contaminants, but the same contaminant may derive from different
sources.
The problem of illegal or improper disposal of chemical waste, for example, caus-
ing a chemical spill which infiltrated into the soil and reached the groundwater can
be defined with an increasing level of detail, starting with the emitted amount and
the identification of the components of the mixture, continuing with the possible
degradation products and the environmental fate and behavior of may be dozens or
hundreds of chemicals with different volatility, water solubility, sorbability, toxicity,
mutagenicity, etc.
The presence of contaminant mixtures is one of the unsolved problems in con-
taminated land management: the identification, the differences in transport and
environmental fate, the endless combinations of interactions between contaminants,
contaminants and soil phases (air, water and solid), contaminants and matrix compo-
nents, as well as with the biota, make the situation and its evaluation very complicated.
Microcosm models and direct toxicity assessment may help in these complex scenarios.
The mobility and transport of single chemicals and mixtures of chemicals in the
three-phase medium may be a problem which should be understood and characterized.
The characteristics of the environment are also part of the problem defini-
tion because topography, the surface water system, ecosystem sensitivity, the soil's
loadability and buffering capacity are highly responsible for the potential scale of
damage.
The medium, where the transport and the physical, chemical and biological trans-
formations of chemical contaminants take place, should be known and understood.
Thorough information about the underground situation is rarely available. Usually
hydrogeological and geochemical explorations are needed to be able to model trans-
port and fate of chemicals at the site in question. There are roughly homogeneous sites
and heterogeneous ones with cracks and fractures, irregular geological and soil layers
and other surprises. The worst are the technogenic soils (formed or altered by industry,
mining or urbanization), occurring many at industrially contaminated sites, because
they are heterogeneous, with alien basic rock (barren, tailings, demolition waste, etc.)
buried or used for replenishment. Assessment and modeling contaminant transport in
such soils need great efforts.
Land uses and the potentially exposed human and ecological receptors should
be identified as main determinants of the “problem''; local habits and consumption
patterns can modify the “problem'' in a large scale.
Risk depends on present and future land uses (residential, agricultural, recre-
ational) and on the sensibility of land users: residents of settlements, including children,
farmers, holiday makers or athletes. Not only the human land uses but also the habitat
function of the contaminated land and soil should be considered. Habitat of endan-
gered or other species under protection is being increasingly taken into account mainly
on civil groups' pressure and recently established laws on natural conservation. Soil as