Cleaning up soil pollution

Soils have been badly damaged, particularly over the last 200 years, by soil pollution. This was brought about through ignorance of soil properties and often by lack of concern by the polluter who often just wanted somewhere to put unwanted waste. There has been a change in attitude in some countries particularly in the last 20 years and governments have brought in measures to protect the soil. Some badly damaged soils have also been subject to remediation, involving the removal, containment and degradation of would-be contaminants. There are a whole range of treatments available for remediation of soil, but many of them extremely expensive.

Methods of treatment can be quite drastic and require removal of the soil to where it can be safely stored or treated to remove the pollutants. This is an expensive option and in-situ treatment is normally preferred if it is appropriate. In situ treatment such as leaching with water, heating, injection of compounds that dissolve the organic contaminants, or treating to soil in a way that locks up the pollutants so that they can be pumped out of the system, is used to remove some of the problem elements. It is usually preferable to remediate the soils in situ but this will depend on the nature of the contamination, its cost, and the effect on the surrounding environment.

One method that has provided a lot of interest is that of phytoremediation, the removal of contaminants by growing plants. During the process plant roots take up the pollutant from the soil. In some cases, the pollutant accumulates in the above-ground parts of the plant. The plant can then be harvested and the would-be pollutants moved to a safe place. In other cases of phytoremediation soil microbes are stimulated to take up the polluting elements, such as polyaromatic hydrocarbons and convert them to forms that are less harmful. There are many possible way of carrying out remediation but most are very expensive to undertake and therefore considerable amounts of polluted land and soil remain around the world.