Soil Pollution Causes

There are numerous causes of soil pollution that occur every day or even every minute. For ease of reference, they are generally split into two: man-made (anthropogenic) causes and naturally occurring causes.

Man-Made Pollutants

Anthropogenic (man-made) soil pollution originates in several types of processes, some deliberate (industrial) and some accidental. Human-caused soil pollution can work in conjunction with natural processes to increase the toxic contamination levels in the soil.

  • Accidental spills and leaks during storage, transport or use of chemicals (e.g. leaks and spills of gasoline and diesel at gas stations);
  • Foundry activities and manufacturing processes that involve furnaces or other processes resulting in the possible dispersion of contaminants in the environment;
  • Mining activities involving the crushing and processing of raw materials, for instance, heavy metals, emitting toxic substances;
  • Construction activities (see below)
  • Agricultural activities involving the diffusion of herbicides, pesticides and/or insecticides and fertilizers;
  • Transportation activities, releasing toxic vehicle emissions
  • Chemical waste dumping, whether accidental or deliberate – such as illegal dumping;
  • The storage of waste in landfills, as the waste products may leak into groundwater or generate polluted vapors
  • Cracked paint chips falling from building walls, especially lead-based paint.

Construction sites are the most important triggers of soil pollution in urban areas, due to their almost ubiquitous nature. Almost any chemical substance handled at construction sites may pollute the soil. However, the higher risk comes from those chemicals that can travel more easily through the air as fine particulate matter. The chemicals that travel as particulate matter are more resistant to degradation and bioaccumulate in living organisms, such as PAHs.

Additionally, construction dust may easily spread around through the air and is especially dangerous because of its lower particle size (less than 10 microns). Such construction dust can trigger respiratory illnesses such as asthma and bronchitis, and even cancer. Moreover, the sites that involve the demolition of older buildings can release asbestos, a toxic mineral that can act as a poison in soil. Asbestos particles can be redistributed by the wind.

Natural Pollutants

Apart from the rare cases when a natural accumulation of chemicals leads to soil pollution, natural processes may also have an influence on the human released toxic chemicals into the soil, overall decreasing or increasing the pollutant toxicity and/or the level of contamination of the soil. This is possible due to the complex soil environment, involving the presence of other chemicals and natural conditions which may interact with the released pollutants.

Natural processes leading to soil pollution:

  • Natural accumulation of compounds in soil due to imbalances between atmospheric deposition and leaking away with precipitation water (e.g., concentration and accumulation of perchlorate in soils in arid environments)
  • 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)
  • Leaks from sewer lines into subsurface (e.g., adding chlorine which could generate trihalomethanes such as chloroform).