Soil contamination, degradation, and pollution mean different things though we often use these terms to mean one thing. Here is the difference:

Soil pollution is when humans introduce harmful objects, chemicals or substances, directly or indirectly into the soil in a way that causes harm to other living things or destroys soil or water ecosystems. Soil pollution is considered a hidden danger because it is a kind that is not easily visible, although its effects can be catastrophic.

Soil contamination is when the concentration of chemicals, nutrients, or elements in the soil becomes more than it naturally is, as a result of human action. If this contamination goes on to harm living organisms, we can call it pollution.

Soil degradation is when the soil loses its value (in terms of nutrients, chemical make-up, etc) as a result of over-farming, over-grazing, or erosion. For example, if a bush fire wipes out the vegetation on a piece of land, thereby exposing the soils, and nutrients in the soil get dissolved by rainwater run-off, the ability of the soil to support plant life is reduced. We can call this soil degradation.

What causes contamination?

Pesticides and herbicides (and other farming chemicals) often end up contaminating soils. Direct discharge of wastewater by industries can also cause that. Leakages in sewage systems, underground storage tanks, and the leaching of soluble substances from landfills can also result in contamination. Rainwater or floods from other polluted lands and water bodies spread contaminants to soils in other locations.

The effects of soils contamination

Soil contamination can result in soil and land pollution, and affect the health of plants that depend on them. It can also harm living organisms in the soils and humans that come into contact with them by touching, breathing, or eating crops from contaminated soils. Contaminants in soils can also get infiltrated into groundwater and pollute them.

Depending on the extent and volume of soil contamination, it can be remedied by
1. Digging out the soils for treatment and disposal
2. Containing it to prevent it from spreading, by placing large plastic materials over the affected area.
3. Treating the soils with some safe chemicals to neutralize the contaminant.