20. Floors

Unlike air and water, soil is not a homogeneous medium. Material flows are generally slow in the absence of infiltrating water. Soil contamination is most often the result of airborne deposits, liquid spills, abandoned solids or runoff.

In northern France, for example, mining has generated huge quantities of solid waste and effluents. Around half of all polluted soils in France have been contaminated by hydrocarbons, and 10-20% contain heavy metals.

Polluted soils can become hazardous to living organisms and plants when they release dust or gases, and when they are leached by rainwater or runoff. In the latter case, the water table may be affected.

When toxic waste is released, some of it is deposited on the ground after having migrated over greater or lesser distances. This is particularly true of serious nuclear...