Soil contamination, soil pollution, or land pollution as a part of land degradation is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste. The most common chemicals involved are petroleum hydrocarbons, polynuclear aromatic hydrocarbons (such as naphthalene and benzo(a)pyrene), solvents, pesticides, lead, and other heavy metals. Contamination is correlated with the degree of industrialization and intensity of chemical substance. The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapour from the contaminants, or from secondary contamination of water supplies within and underlying the soil. Mapping of contaminated soil sites and the resulting cleanups are time-consuming and expensive tasks, and require expertise in geology, hydrology, chemistry, computer modeling, and GIS in Environmental Contamination, as well as an appreciation of the history of industrial chemistry.
In North America and Western Europe the extent of contaminated land is best known, with many of countries in these areas having a legal framework to identify and deal with this environmental problem. Developing countries tend to be less tightly regulated despite some of them having undergone significant industrialization.
Soil pollution can be caused by the following (non-exhaustive list) :
Microplastics
Oil spills
Mining and activities by other heavy industries
Accidental spills may happen during activities, etc.
Corrosion of underground storage tanks (including piping used to transmit the contents)
Acid rain
Intensive farming
Agrochemicals, such as pesticides, herbicides and fertilizers
Petrochemicals
Industrial accidents
Road debris
Construction activities
Exterior lead-based paints
Drainage of contaminated surface water into the soil
Ammunitions, chemical agents, and other agents of war
Waste disposal
Oil and fuel dumping
Nuclear wastes
Direct discharge of industrial wastes to the soil
Discharge of sewage
Landfill and illegal dumping
Coal ash
Electronic waste
Contaminated by rocks containing large amounts of toxic elements.