Soil contamination or soil pollution as 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.

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.

Man-made contaminants are the main causes of soil pollution and consist of a large variety of contaminants or chemicals, both organic and inorganic. They can pollute the soil either alone or combined with several natural soil contaminants. Man-made soil pollution is usually caused by the improper disposal of waste coming from industrial or urban sources, industrial activities, and agricultural pesticides.

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 the possible dispersion of contaminants in the environment;

3. Mining activities involving the crushing and processing of raw materials, for instance, heavy metals, emitting toxic substances;

4. Construction activities

5. Agricultural activities involving the diffusion of herbicides, pesticides and/or insecticides and fertilizers;

6. Transportation activities, releasing toxic vehicle emissions.

7. Chemical waste dumping, whether accidental or deliberate – such as illegal dumping;

8. The storage of waste in landfills, as the waste products may leak into groundwater or generate polluted vapors.

9. Cracked paint chips falling from building walls, especially lead-based paint.

1. 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)

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 trihalomethanes such as chloroform).

Soil Composition

While a nearly infinite variety of substances may be found in soils, they are categorized into four basic components: minerals, organic matter, air and water. Most introductory soil textbooks describe the ideal soil (ideal for the growth of most plants) as being composed of 45% minerals, 25% water, 25% air, and 5% organic matter. In reality, these percentages of the four components vary tremendously. Soil air and water are found in the pore spaces between the solid soil particles. The ratio of air-filled pore space to water-filled pore space often changes seasonally, weekly, and even daily, depending on water additions through precipitation, throughflow, groundwater discharge, and flooding. The volume of the pore space itself can be altered, one way or the other, by several processes. Organic matter content is usually much lower than 5% in South Carolina (typically 1% or less). Some wetland soils, however, have considerably more organic matter in them (greater than 50% of the solid portion of the soil in some cases).

soil testing in india

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thank you very much providing the information about soil pollution, testing, soil type etc.But sir i need the regulatory parameters, excess limit of heavy metal and metal that contaminate the soil. As well as many environmental agency define the water quality criteria. There is no one Indian agency which defines the soil quality criteria?

Oh my dear Dr Prem Baboo very satisfactory answer and also in detail. I fully agree with you, Sir

the soil quality criteria define base on soil function

sir what is that @Hamid reza Matinfer

Soil quality is the capacity of a specific kind of soil to function to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation. The ideal soil as being composed of 45% minerals, 25% water, 25% air, and 5% organic matter. soil parameters stable as soil depth or granularity, relatively stable the salt content, the content of organic mass in soil, heavy metal contamination, relatively dynamic pH, the content of nutrients, and dynamic soil humidity and temperature, microbial activity, etc. The most popular indicators used to assess soil quality are soil organic carbon, total nitrogen and soil acidity. SOC is fundamental to soil fertility and is a strong indicator of a soil's biological health. Soil fertility tests can indicate the health of a soil for the chemical component. If nutrient levels and pH are adequate for the crops grown in the field then the chemical indicators are good. Soil organic matter level, often included in a soil fertility test, is a reasonable soil biological indicator.