The following are the main mechanisms that generate soil pollution:
A. Antropogenic – through human activity including:
1. Accidental spills and leaks during storage, transport or use of chemicals (e.g., leaks and spills of gasoline and diesel at gas stations);
2. Foundry activities and manufacturing processes that involve furnaces or other processes resulting in possible dispersion of contaminants in environment;
3. Mining activities involving crushing and processing of raw materials (such as mining activity);
4. Construction activities
5. Agricultural activities involving the spread of herbicides/pesticides/insecticides and fertilizers;
6. Transportation activities (e.g., vehicle emissions)
7. Dumping of chemicals (accidental or intended – such as illegal dumping);
Storage of wastes in landfills (which may leak to groundwater or generate polluted vapours)
8. Cracked paint chips falling from building walls, especially lead-based paint;
B. Natural causes:
1. Natural accumulation of compounds in soil due to imbalances between atmospheric deposition and leaching away with precipitation water (e.g., concentration and accumulation of perchlorate in soils in arid environments).
2. Natural production in soil under certain environmental conditions (e.g., natural formation of perchlorate in soil in the presence of a chlorine source, metallic object and using the energy generated by a thunderstorm).
3. Leaks from sewer lines into subsurface (e.g., adding chlorine which could generate trihalometanes such as chloroform).