CONTAMINANTS
The major soil contaminants are petroleum products, polyaromatic hydrocarbons (PAH´s), heavy metals, halogenated hydrocarbons and old pesticides and fungicides. The contaminats encountered may also be old chemicals, such as PCB and DDT, whose use was banned years ago.
CONTAMINATED SITES
Contaminated sites are usually those in which certain chemicals have been used over a number of years, or sites where major accidents have happened, leading to pollution of the soil.
Sites contaminated by petroleum compounds range from leaking household oil tanks to areas polluted by oil tanker spills, e.g., old and new petrol stations as well as areas surrounding oil storage facilities, pipelines, terminals and refineries. Old military bases represent a special problem group.
Polyaromatic hydrocarbons (PAH´s), many of which are carcinogenic, also contribute greatly to soil contamination. They are usually found as creosotes, linked to old industrial sites and gas plants.
Heavy metals also tend to be found mainly in sites which have been used for industrial purposes, such as smelters or electroplating plants. Chlorinated hydrocarbons have mainly been used as solvents at laundries, and often vast amounts have ended up in the surrounding environment. Old pesticides and fungicides can still be found in storage facilities in rural areas, and their large-scale use in agriculture and the forest industry has left its mark on the soil as well.
REMEDIATION TECHNIQUES
The remediation techniques used can be divided into contaminant and remediation methods. Contaminant techniques aim at preventing the further spread of the pollutant in the soil and those of remediation remove the contaminant from the soil. Remediation methods include, e.g., air sparging as well as chemical, thermal and microbiological treatment. The question of which method is to be used depends on what use the land will be put to, what kind of a risk the contamination poses, the chemical, physical and biological properties of both the contaminant and the soil and the financial resources available.
These issues will be discussed in detail at the Seminar on Treatment of Contaminated Soils in Vilnius, Lithuania 20 - 22 February 1998. The seminar is being organized by the UBC and ECAT Lithuania, and it has received financial support from the Nordic Council of Ministers.
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