Characteristics of Natural and Urban Soils - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 104

close to the main urban centres anthropogenic contamination is superimposed on the
natural system.
Figure 2.6 illustrates the ranges of trace elements that can be found in min-
eral soils. It is probably based on data obtained in North America, and takes no
account of the particular soil (weathering) environments from which the samples
were collected.
In many countries methods and criteria for assessing impacts on human health,
ecology and groundwater have developed. Thus, Soil Quality Standards based
mainly on total concentration were carried out.
It should also be noted that the entire focus is always on the known contami-
nant metals or metalloids and takes no account of other elements or soil properties
that play a major role in immobilising the contaminant elements. Likewise, the role
of substances like chloride, which can render metals such as lead much more sol-
uble and mobile by complexation, or soil pH which also affects speciation and
mobility, is ignored in these criteria. All soils are, as it were, regarded as being
a “standard soil” in Dutch practice. The exclusive focus on those elements that
are known or suspected to be of public health and ecological significance resulted
in establishment of companies that carry out contamination assessments and site
remediation, determining only those elements in laboratory analyses. Therefore
intelligent assessment is deprived of relevant information.
Figure 2.6 was taken from Mitchell ( 1965 ). The stippled sections indicate
more unusual concentration values. Certain extremely high values from localities
Fig. 2.6 The ranges of trace elements that can be found in mineral soils (Mitchell 1965 )