Environmental Engineering Reference
In-Depth Information
be made using electrical methods to map the most conductive non-organic
contaminants. Direct detection of shallow organic products, such as hydrocarbons,
can sometimes be achieved by seeking a low conductivity associated with organic
products [BEN 93]. A summary of different approaches is given in Table 12.4.
Other applications include mapping of areas contaminated by jet fuel using
induced polarization techniques [MOR 99] and the combination of radar (GPR) and
tomographic techniques to develop sectional data of water content in the unsaturated
zone [PAP 99]. This same technique can be used to develop a detailed picture of
DNAPL saturation in areas where there was a spill.
Products to be identified
Comments
When non-organic products are present in sufficient
concentrations or organic products are part of the
contaminated area, they can be detected by electrical
methods and sometimes by the radar (GPR). The higher
specific conductivity of pore fluid acts as a marker by
which the contaminated area can be mapped
Non-organic products or
mixtures of inorganic and
organic products
When hydrocarbons were present in the soil or float on
shallow water long enough, they can sometimes be
detected by electrical methods or by radar (GPR).
Because of their low conductivity, they can sometimes
be detected by electrical methods.
Due to changes in the dielectric constant or withdrawal
of the capillary zone, they can sometimes be detected by
radar (occasionally when hydrocarbon degradation
occurs, the conductivity may increase). These
applications are limited and should be treated with
caution. A more reliable approach is to map the natural
permeable channels
Hydrocarbons
Table 12.4.
Surface geophysical methods to map areas of contamination [BEN 93]
12.4. Conclusions
The problem of contaminated land has been the object of intensive research in
recent years. The focus of this chapter has been on both the technical and
methodological aspects. Technical aspects include methods of identification and
characterization
in situ
and off-site, including the implementation of a number of
techniques for identification of solid, liquid and gaseous pollution. Methodological
aspects focused on the development of guidelines that currently offer the possibility
of optimizing the investigation and identification of pollutants, and provide decision
