Soil may be broadly defined as the weathered layer of the earth’s crust with living organisms and their products of decay. The word Soil is derived from a Latin word Solum. it means earthy material in which the growth of plants takes place. Soil is a complex physio-biological system. it contains water, mineral salts, nutrients, and dissolved oxygen. It provides anchorage to plants. The study of soil science is called pedology.
About 99% by weight of earth’s crust is constituted by about 12 elements only, wheres elements exist in traces. Earth’s crust comprises rocks and the loose material derived from these rocks. These rocks disintegrate and form gravel sand and clay. The composition of the earth’s crust is shown in Fig (1.1).
Fig 1.1 Elementary Composition of the earth’s Crust
Types of Rocks in Earth’s Crust.
The earth’s crust basically consists of the following three types of rock.
Igneous rocks are formed by cooling and solidification of molten rock material called Magma.
Sedimentary rocks are developed as a result of gradual accumulation, consolidation, and hardening of products of weathering of mineral materials. These things are brought about by wind or waters. These rocks are characterized by the presence of distinct sedimentary layers.
These rocks are formed as a result of the metamorphosis of igneous and sedimentary rocks under the influence of high pressure and intense heat.
The modification of the earth’s crust as a result of Its interaction with atmosphere and hydrosphere is called weathering. Due to constant battering of the earth’s crust by wind, rains, and changes in temperature, the constituent rocks are deposited into small fragments. The final products of weathering are sand, silt, gravel, and clays.
Causes of Soil Pollution.
Like air and water pollution, soil pollution is of considerable importance.
Soil pollution was originally defined as the contamination of the soil system by considerable quantities of chemicals or other substances. This results in the reduction of its fertility or productivity with respect to the qualitative and quantitative yield of the crops.
Pollutants remain in direct contact with the soil for relatively long periods in soil pollution. These pollutants change the chemical and biological properties of the soil. The harmful chemicals enter the human food chain from soil or water plants.
The main aspects of soil pollution are smelting, sludge, fertilizers, pesticides, etc.
The dumping of industrial wastes and municipal wastes leads to the leaching seepage of toxic substances into the soil. This pollutes the groundwater.
Due to some modern agricultural practices, obnoxious pesticides, fungicides, insecticides, biocides, bactericides, the land is contaminated.
There can be direct pollution of soil by dangerous pathogenic organisms.
Fly ash generated from thermal power plants adds to the soil.
Industrial waste discharged into streams or dumped into the surrounding land causes soil pollution.
Mining wastes, non-biodegradable organic pollutants, industrial sludges, heavy metal sludges, etc. cause serious water and soil pollution.
Farm wastes, radioactive wastes, human and animal exereta, soil conditioners, soil fumigants also cause soil pollution.
Garbage and rubbish materials such as plastics, metal cans, glasses, street sweepings, waste paper, fibers, rubber, etc. contribute to soil pollution.
Control of Soil Pollution.
The various approaches to control soil pollution are as follows:
The use of highly toxic and resistant synthetic chemical pesticides should be banned.
We should encourage the use of bio-pesticides in place of toxic chemical pesticides.
Suitable biological and chemical methods may be employed for effective treatment of
domestic sewage and adopting modern methods of sludge disposal.
Recycling and reuse of materials should be done wherever possible, For example, recycling of glass, plastics, paper, and production of biogas.
Industrial wastes have to be properly treated at the source, by segregation of wastes.
For permanent disposal of hazardous industrial wastes, security land-fills have tobe constructed.
The excessive use of chemical fertilizers and insecticides should be avoided. We should provide more organic manure to the fields and thereby maintaining healthy biota. A soil rich in organic matter also decrease soil erosion.
Govt should implement a stringent and pro-active population control programs,
Strict rules should be implements for deforestation.
There should be informal and formal public awareness programs to educate people at large. It should be regarding the health hazards and undesirable effect due to environmental pollution, Mass media, educational institutions, and voluntary agencies should be involved fo do that.