Sources, causes and control of soil pollution
Soil pollution:- It refers to the contamination of soil with anomalous concentrations of toxic substances.
Sources of soil pollution:-
1. Agricultural sources:- Agricultural practices such as the use of non-organic products in crop and livestock production lead to soil pollution. These substances include artificial chemical pesticides, herbicides, fungicides, and fertilizers, as discussed below:
a. Pesticides, herbicides, and insecticides:-
> The introduction of modern pesticides, herbicides, and insecticides has resulted in an increase in the use of agricultural chemicals. These chemicals are used to control the pests, insects, weeds, fungi, and diseases that attack crops.
> Most of these chemicals are non-biodegradable, while others decompose to products that are toxic to soil. These products seep into the ground and act on the soil, thereby changing its structure, composition, and pH.
b. Improper use of fertilizer:-
> Fertilizers are mostly used to correct the deficiency of soil nutrients. A soil that is deficient of potassium, calcium, nitrogen, and sulfur, among other important macro-nutrients, should be treated with the right fertilizer and at the right amount.
> However, some farmers use fertilizers indiscriminately, leading to soil pollution. What is more, the materials used to manufacture fertilizers contain impurities that add to soil toxicity. For instance, the rock phosphates mineral used for the manufacture of mixed fertilizers contain traces of Asbestos, Cadmium, and Lead, which are transferred to the fertilizer during production. These metals are non-biodegradable and, with time, accumulate to toxic levels.
2. Industrial sources:-
> Industrial wastes or byproducts are among the leading causes of soil pollution. They can be in the form of gas, liquid, or solid substances. Carbon dioxide, nitrogen dioxide, sulfur dioxide, and carbon monoxide are some of the gases produced from industrial activities that cause considerable pollution to soil indirectly.
> These byproducts combine with the rainwater causing the production of acidic rain, which changes the soil pH and, after that, affects the overall crop production. Industries also dump their solid and liquid effluents into the soil.
3. Urban waste:-
> Most developing countries have a problem controlling the disposal of municipal garbage. The garbage is dumped anyhow and contains wastes such as food waste, plastics, industrial wastes, e-waste, and general household wastes.
> It appears as if the urban administrators do not know that most of the non-biodegradable waste materials could be recycled and the organic materials disposed of in areas designated for natural decomposition.
4. Sewer sludge:-
> Sewage plants also contribute to soil pollution owing to how they dispose of sewage sludge from domestic and commercial waste. The sewage sludge is usually treated before being disposed of into land or water bodies.
> When disposed of on land, the sludge can release high amounts of nutrients depending on the source that may surpass the natural soil nutrient requirement, thus posing a risk to human health and/or the ecosystem at large. Sewer sludge may also contain high levels of metals, further polluting the soil.
5. Mining and Smelting sources:-
> Mining activities cause soil pollution on a large scale. The operations cause a change of the landscape and expose the previously undisturbed soils to the elements of weather.
> Erosion of the soil containing some traces of mineral ores and fine materials around the mining areas results in sediment loading in the water sources and drainage ways. They end up in the soil through irrigation and flowing stormwater.
> There are also other hazardous materials that leak from mining activities, including harmful dust particles that are deposited on the surrounding soils. In developing countries, the pollution levels are even higher because activities such as gold mining are done using traditional methods, which lead to the release of mercury and other heavy metals into rivers and neighboring lands.
> Some of the polluted rivers are also used for irrigation, further leading to the pollution of the irrigated soils.
6. Nuclear sources:-
> Every living organism is continuously exposed to background radiation. If the levels of these radiations exceed a given limit, they lead to disastrous effects. Radiation pollution results from two sources, that is, the natural and anthropogenic actions.
> In nature, there are radioactive minerals that contribute to soil pollution such as radionuclides of radon-222 and Radium -226, Thorium, Uranium, isotopes of Potassium (K-40) and Carbon (C-14) are commonly found in soil, rock, water and air. All the radionuclides deposited on the soil emit gamma radiations.
> The explosion of hydrogen weapons and cosmic radiations include neutron, proton reactions by which Nitrogen (N-15) produces C-14. This C-14 participates in Carbon metabolism of plants, which is then transmitted into animals and human beings.
> Radioactive waste contains several radionuclides such as Strontium90, Iodine129, Cesium-137 and isotopes of Iron, which are most injurious. Strontium gets deposited in bones and tissues instead of calcium.
> Improper disposal of wastes from nuclear reactors containing Ruthenium-106, Iodine-131, Barium140, Cesium-144 and Lanthanum-140 along with primary nuclides Sr-90 with a half-life 28 years and Cs-137 with a half-life 30 years can, therefore, result in soil pollution and contamination.
> Rainwater carries Sr-90 and Cs-137 to be deposited on the soil, where they are held firmly with the soil particles by electrostatic forces.
7. Deforestation:- Though not a direct contributing factor to soil pollution, deforestation leads to the removal of the shield that protects the soil against the agents of erosion. The exposed soil is easily eroded and exposed to artificial chemical pollutants from the air, wind, and rain.
8. Biological agents:- Soil gets a large amount of human, animal and bird excreta, which constitute a major source of land pollution by biological agents.
9. Acid rain:- When pollutants in the air such as sulfur dioxide and nitrogen oxide mix with rain acid rain occurs, which has been found to impact soil negatively by dissolving important nutrients and even changing the soil’s structure.
Causes of soil pollution:-
1. Industrial Pollution:- The discharge of industrial waste into soils can result in soil pollution. In India, as mining and manufacturing activities are increasing rapidly, soil degradation is also increasing. The extraction of minerals from the earth is responsible for affecting soil fertility. Whether it is iron ore or coal, the by-products are contaminated, and they are disposed of in a manner that is not considered safe. As a result, the industrial waste stays on the soil surface for a long duration and makes it unsuitable for further use.
2. Agricultural Activities:- The use of insecticides and pesticides for a long period can cause soil pollution. Repetitive use can cause insects and pests to become resistant to it. Instead of killing pests and insects, it degrades the soil quality. They are full of chemicals that are not produced in nature and cannot be broken down by them. As a result, they seep into the ground after they mix with water and slowly reduce the fertility of the soil. Plants absorb many of these pesticides, and after decomposition cause soil pollution.
3. Waste Disposal:- Disposal of plastics and other solid waste is a serious issue that causes soil pollution, disposal of electrical items such as batteries causes an adverse effect on the soil due to the presence of harmful chemicals. Eg: lithium present in batteries can cause the leaching of soil. Human waste such as urine, faeces, diapers, etc is dumped directly in the land. It causes both soil and water pollution.
4. Acid Rain:- It is caused when pollutants present in the air mix with the rain and fall back on the ground. The polluted water could dissolve away some of the essential nutrients found in soil and change the structure of the soil thus making it unsuitable for agriculture.
5. Heavy Metals:- The presence of heavy metals (such as lead and mercury) in very high concentrations present in soils can cause them to become highly toxic for human beings.
6. Nuclear Waste:- It can also lead to soil degradation.
7. Oil Spills:- Oil leaks can happen during the storage or transport of chemicals, the chemicals present in the fuel deteriorates the quality of soil and make them unsuitable for further cultivation, chemicals can also enter into the groundwater through the soil, and hence it will make water undrinkable.
Control of soil pollution:- Soil pollution is a complex issue that must be addressed. It is important that we all understand the importance of soil to our survival. The earlier we recognize the problem, the simpler it will be to solve the problem of soil pollution. It's a complicated problem that requires everyone's participation, from individuals to the government.
A few methods for reducing soil pollution are listed below.
1. Reduced Use of Chemical Fertilizers:- Chemical fertilizers are more damaging than helpful. While the right quantity can help the soil become more fertile, too much might potentially poison it. Chemical fertilizers in excess could harm the soil in a variety of ways. It has the ability to affect the soil's pH values.
2. Reforestation and Afforestation Should be Promoted:- Soil erosion, which is produced by deforestation, is one of the major sources of soil pollution. With an ever-increasing population, it is only logical that mankind requires more and more room to expand their civilization. It is frequently accomplished at the expense of soil health. Reforestation of a deforested area should be encouraged to prevent this from happening.
3. Recycle and Reuse Products:- These measures not only reduce waste output, but they also reduce soil pollution. Plastic now makes up a significant portion of the waste flow. The great majority of these wastes are buried in landfills.
4. Promote Use of Natural Manure:- One of the best sources of nutrients for the soil is natural manure. It's 100% natural and safe. It restores the soil's critical nutrients and improves its overall health. It doesn't produce any toxic by-products that could harm the soil or the environment.