(3) Soil Pollution:

Soil pollution or soil contamination, is a condition that occurs when soil loses its structure, biological and chemical properties due to the use of various synthetic chemicals and other natural changes in the soil environment. Factors often believed to contribute to soil pollution include the use of chemicals such as acid rain, fertilizers, the salinity of the soil and environmental changes. Some of the most common factors causing soil pollution are elucidated and discussed at length below:

1. Oil Spills:

The accidental oil spills and leakage from cargo oil tankers, tanker trucks and pipelines pollute soil in the sense that the fertility status of the land becomes greatly compromised after an oil spill.

2. Use of salty water:

The use of water with a high salinity i.e. water that contains higher amounts of salts such as sodium chloride [NaCl], adversely affects the soil as well as the crop growth. The salts present in the water accumulate in the top layer of the soil, resulting in decreased growth of crops and decreased yields, and ultimately making the soil and the land unfit for crop yielding and other agricultural practices.

3. Heavy Metal

Soil pollution by heavy metals is most often the result of mining, manufacturing and improper disposal of man-made products, including paint, batteries and pesticides. Exposure is most often chronic, occurring over an extended period of time. Nickel, copper, chromium and manganese are also widespread contaminants, each with its own list of health effects. Additionally, most heavy metals have carcinogenic effects.

4. Polychlorinated Biphenyls:

Polychlorinated biphenyls (PCBs) are completely man-made products common in manufacturing processes and equipment, including coolants, transformers, capacitors and motors. In the 1970s Congress banned them as a persistent organic pollutant, the cause of numerous environmental contamination sites now considered unlivable, including Superfund sites in Massachusetts, New York, Indiana and the Great Lakes.

5. Poor agricultural practices:

Soil erosion--a result of poor agricultural practices--removes rich humus topsoil developed over many years through vegetative decay and microbial degradation and thus strips the land of valuable nutrients for crop growth.

6. Use of chemicals on soil and agricultural crops:

Excessive use of chemicals such as pesticides, insecticides and fertilizers is one of the prime factors causing soil pollution. These chemicals adversely affect the soil by increasing its salinity and making it imperfect for crop bearing. It also affects the microorganisms present in the soil, causing the soil to lose its fertility and resulting in the loss of minerals present in the soil, thus causing soil pollution.

7. Mineral exploitation:

Environmentally unfriendly mineral exploitation practices and srip mining for minerals, gas and coal reserves lays waste thousands of acres of land each year, denuding the Earth and subjecting the mined area to widespread erosion problems. Soil erosion not only despoils the Earth for farming and other uses, but also increases the suspended-solids load of the waterway. This increase interferes with the ecological habitat and poses silting problems in navigation channels, inhibiting the commercial use of these waters.

8. Solid waste:

Among the most significant environmental problems, one is the enormous volume of solid waste which is being produced every day but not be disposed properly. The mismanagement of the solid waste, particularly the polythene shopping bag has caused serious threat to the soil. The most common and convenient method of disposing of municipal solid wastes is in the sanitary landfill present greater environmental hazards. In the landfills, non-biodegradable materials like plastic bottles, Styrofoam and cans can remain buried and intact for thousands of years, leaching chemicals into the ground over the years. Groundwater infiltration and contamination of soil with toxic chemicals is the result.

9. Urbanization and Industrialization:

The increase in urbanization due to population pressure presents additional soil-erosion problems. The industrial runoff has also contributed a lot in polluting topsoil and regular disposal of waste effluent leaches to soil and degrades it not only making land barren but also pollutes groundwater.