Soil Pollution – Sources and Effects

Posted on Oct 9 2019 - 7:59pm by Preeti

Soil Pollution

Soil Pollution
Unfavourable alteration of soil by addition or removal of substances and factors which decrease soil productivity, quality of plants and ground water is called soil pollution.

Sources of Soil Pollution

Soil pollution mainly results from the following sources
1. Industrial Wastes
2. Urban Wastes
3. Radioactive Pollutants
4. Agricultural Practices
5. Chemical and Metallic Pollutants

1. Industrial Wastes
Disposal of industrial waste is the major problem responsible for soil pollution. These industrial pollutants are mainly discharged from pulp and paper mills, chemical industries, oil refineries, sugar factories, tanneries, textiles, steel, distilleries, fertilizers, pesticide industries, coal and mineral mining industries, metal processing industries, drugs, glass, cement , petroleum and engineering industries etc.

Hazardous wastes generated from chemical industries which find their way into the soil environment.

Industry Wastes
i.  Fertilizers Arsenic, ammonia, fluoride,heavy metals, acids, tar, phenolics, cyanide, polyaromatic hydrocarbons (PAH)

ii. Caustic Soda Mercury, chlorinated hydrocarbons, lead carbonate, asbestos.

iii. Pesticides Chlorinated aromatics, chlorobenzene, organophosphorus derivatives, solid residues of pesticides, chlorophenols, dioxins.

iv. Organic chemicals Chloro, nitro and phenolic substances

v. Organic solvents Organic liquid and semi solid residues

vi. Fibre Zinc, polysulphides ,lead salts, manganese

2. Soil Pollution by Urban Wastes
Urban wastes comprises both commercial and domestic wastes consisting of dried sludge of sewage. All the urban solid wastes are Commonly referred to as ‘refuse’: Solid wastes and refuse, particularly in urban areas contribute to soil pollution. This refuse contains garbage and rubbish materials like plastics, glasses, metallic cans, fibres, paper, rubbles, street sweepings, fuel residues, leaves, containers, abandoned vehicles and other discarded manufactured products.

3. Radioactive Pollutants
Radioactive substances resulting from explosions of nuclear de- vices, atmospheric fall out from nuclear dust and radioactive wastes (produced by nuclear testing laboratories and industries) penetrate the ‘soil and accumulate there creating land pollution. Radio nuclides of radium, thorium, uranium, isotopes of potassium (K-40) and carbon (C-14) are very common in soil, rock, water and air. Explosion of hydrogen weapons and cosmic radiations induce neutron-proton reactions by which nitrogen (N-IS) produces
C-14. This C14 participates in the carbon metabolism of plants which is then introduced into animals and man.

4. Agricultural Practices

Modern agricultural practices pollute the soil to a large extent. Today with the advancing agro-technology, huge quantities of fertilizers, pesticides, herbicides, weedicides and soil conditioning agents are employed to increase the crop yield. Many agricultural lands have now excessive amounts of plants and animals wastes which are posing soil pollution problems. Apart from these farm wastes, manure slurry, debris, soil erosion containing mostly inorganic chemicals are reported to cause soil pollution. USA
alone produces about 18 million tonnes of agricultural wastes every year. Some of the agents responsible for this pollution are as follows.
(a) Fertilizers
Now-a-days agricultural practices rely heavily on artificial fertilizers, which generally contain one or more of the plant nutrients i.e. nitrogen, phosphorous and potassium. Critical pollution problems arise mainly from their excessive application rates. Although the fertilizers are used to fortify the soil, yet they also contaminate the soil with their impurities, when the fertilizers are contaminated with other synthetic organic pollutants, the water present in the soil may also get polluted.
(b) Pesticides
Among pesticides the most important are the chlorinated hydrocarbons e.g. D.D.T., B.H.C., aldrin, endrin, dieldrin, lindane, chlordane, heptachlor and endosulphan. Organo-phosphates include-malathion, parathion, ethion, fenthion, trithioin, dursban, dimethoate, phosdrin and metasystox etc. The remnants of these pesticides may get absorbed by soil particles which may contaminate root crops grown in soils.
(c) Soil Conditioners, Fumigants and Other Chemical Agents
In addition to the fertiliz- ers, pesticides and biocides, soil conditioners and fumigants are also employed to the land system to increase and protect the soil fertility as well as to kill the hazardous insects. These chemical agents are reported tocause alterations in both agricultural and horticultural soil areas. They contain several toxic metals lead, arsenic, cadmium, mercury and cobalt etc. which when applied to a land will accumulate on the soil permanently thereby introducing these chemical compoens into growing crops.
(d) Farm Wastes
Increasing population of cows, cattle, pigs and poulterers have resulted in considerable soil pollution. Buildings in which grazing animals are housed can be cleaned using water but the manure is also washed out and deposited as wet slurry on the land. This slurry deposited on soil may seep into ground water and pollute it. When these farm wastes are dumped into heeps, they may become a good breeding ground for insects and nuisance arise.
5.Chemical and Metallic Pollutants
A number of industries including textiles, pesticides, paints, dyes, soap and synthetic detergents, tanneries, drugs, batteries, cement, asbestos, rubber, petroleum, paper and pulp, sugar, steel, glass, electroplating and metal industries pour their hazardous effluents in soil and water creating disastrous effects on living organisms.

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B.Tech Biotechnology,MBA(HR and Marketing), UGC/CBSE NET Qualified

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