pdf 4,3 MB - Naturvårdsverket

HÅLLBAR SANERING
Rapport 5663 - Klorerade lösningsmedel
Another major exposure pathway, besides groundwater transport, is through gas
migration because chlorinated aliphatic compounds generally have a very high
vapor pressure. Gaseous transport of magnitude may not only occur from the
source area but also from the contaminated groundwater.
There are a number of pathways through which human beings can be exposed
to chlorinated solvents and their degradation products. Chlorinated solvents are
most commonly found at such depths in the soil that direct exposure through
contact with soil does not constitute a major risk. Instead, exposure through inhalation
is generally considered to be the most prevalent exposure pathway. Evaporation
and gaseous transport do not exclusively occur in the source area, but also
above a contaminated groundwater from which chlorinated solvent vapors can be
transported through the soil layers and into overlying buildings. Exposure through
contaminated drinking water may also constitute an important exposure pathway.
There is a high variability between different chlorinated solvent compounds
regarding their human health hazards. The hazards range from moderate to very
high. Vinyl chloride is a known carcinogen while others are potentially carcinogenic.
Ecotoxicological hazards also have a high variability within this group of
compounds.
Even though chlorinated solvents have been handled at numerous sites across
the country, with a high probability of soil and groundwater contamination as a
result, there is very limited knowledge regarding the scope of the problem in
Sweden. Thorough and systematic on site investigations and remedial actions
focusing on chlorinated solvents has only been performed at a very limited number
of sites. This stands in contrast to the situation in several European countries and
North America where the problem of chlorinated solvent contamination has
received more attention and higher priority when planning remedial actions.
Site investigations and remedial actions used for these contaminants involve
bigger challenges compared to e.g. petroleum hydrocarbons. One of the major
challenges during the investigation phase is to localize and delineate the con-
taminant source and migration pathways. During remediation, the extensive coverage
of contamination and the distribution between different environmental media
has the consequence that no single method is usually sufficient to reach predetermined
remedial action objectives. The usage of one method within the source area
and another within the plume is not unusual. Furthermore, complementary remedial
actions may have to be considered that prevent or limit groundwater migration so
that an acceptable risk reduction level can be achieved.
There is an abundance of technologies to choose from when considering the
most appropriate remedial technology for a given site. Some methods that are
commonly used to treat fuel hydrocarbons and other organic contaminants are also
applicable to chlorinated solvents remediation, while a number of other methods
are more specifically designed for chlorinated solvents. There has been significant
research and development of chlorinated solvent remediation technologies since
the late 1980’s. The knowledge base regarding the fate and behavior of chlorinated
solvents in soil and groundwater has also been considerably expanded. This is
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