Soil pollution is defined as the presence of toxic chemicals (pollutants or contaminants) in soil, in high enough concentrations to pose a risk to human health and/or the ecosystem. In the case of contaminants which occur naturally in soil, even when their levels are not high enough to pose a risk, soil pollution is still said to occur if the levels of the contaminants in soil exceed the levels that should naturally be present.

Causes of soil pollution

All soils, whether polluted or unpolluted, contain a variety of compounds (contaminants) which are naturally present. Such contaminants include metals, inorganic ions and salts (e.g. phosphates, carbonates, sulfates, nitrates), and many organic compounds (such as lipids, proteins, DNA, fatty acids, hydrocarbons, PAHs, alcohols, etc.). There are two main causes through which soil pollution is generated: anthropogenic (man-made) causes and natural 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;
• 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.

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).

The Effects of Soil Pollution

Soil pollution affects plants, animals and humans alike. While anyone is susceptible to soil pollution, soil pollution effects may vary based on age, general health status and other factors, such as the type of pollutant or contaminant inhaled or ingested. However, children are usually more susceptible to exposure to contaminants, because they come in close contact with the soil by playing in the ground; combined with lower thresholds for disease, this triggers higher risks than for adults. Therefore, it is always important to test the soil before allowing your kids to play there, especially if you live in a highly industrialized area.

Diseases Caused by Soil Pollution

Humans can be affected by soil pollution through the inhalation of gases emitted from soils moving upward, or through the inhalation of matter that is disturbed and transported by the wind because of the various human activities on the ground. Soil pollution may cause a variety of health problems, starting with headaches, nausea, fatigue, skin rash, eye irritation and potentially resulting in more serious conditions like neuromuscular blockage, kidney and liver damage and various forms of cancer.

Soil Pollution Facts

Soil acts as a natural sink for contaminants, by accumulating and sometimes concentrating contaminants which end up in soil from various sources. Tiny amounts of contaminants accumulate in the soil and - depending on the environmental conditions (including soil types) and the degradability of the released contaminant - can reach high levels and pollute the soil. If the soil is contaminated, home-grown vegetables and fruits may become polluted too. This happens because most of the soil pollutants present in the soil are extracted by the plants along with water every time they feed. Thus, it is always prudent to test the soil before starting to grow anything edible. This is especially important if your garden is located near an industrial or mining area, or within 1 mile of a main airport, harbor, landfill, or foundry.

References

1.     https://www.environmentalpollutioncenters.org/soil/#:~:text=Soil%20pollution%20is%20defined%20as,health%20and%2For%20the%20ecosystem.

2.     https://en.wikipedia.org/wiki/Soil_contamination

3.     https://www.soils.org/about-soils/contaminants

4.     https://www.conserve-energy-future.com/causes-and-effects-of-soil-pollution.php