Soil pollution and its effects - class-VII

It is not true that soil $pH$ is in the range $6$ to $8$, the soil fertility is diminished

Development of such pesticides should be encouraged, which may save crops from pests and rodents but should not contaminate soil with toxic chemicals.
It is a measure to control soil pollution.

Most industries are dependent on extracting minerals from the Earth.the industrial waste lingers in the soil surface for a long time and makes it unsuitable for use.
Pesticides and herbicides are used in agricultural practices and these chemicals penetrate into soil and damages them.
Cutting of trees leads to soil erosion.

Radioactive substances resulting from explosions of nuclear testing laboratories and industries giving rise to nuclear dust radioactive wastes, penetrate the soil and accumulate giving rise to land/soil pollution.
Pesticides and herbicides are added in soil in agriculture practices to remove unwanted plants. these chemicals penetrate into soil and damages the soil.

Applying bio-fertilizers and manures can reduce chemical fertilizer and pesticide use. Biological methods of pest control can also reduce the use of pesticides and thereby minimize soil pollution.

Pesticides are substances meant for attracting, seducing, and then destroying any pest. 
Herbicides are substances that is toxic to plants, used to destroy unwanted vegetation.
Insecticides are substances used for killing insects.
All the are used in agriculture and harmful to soil.

There should be sufficient duration between the harvesting of crops and time of last spray of pesticides.
It is a measure to control soil pollution.
This will help in reducing contamination of pesticides, directly to the crop. It will also cause less contamination of chloride and other chemicals to the soil.

Pesticides and fertilizers should be applied on croplands only in recommended dose, prescribed by Indian Standard Institution experts. It will help in reducing the level of water and soil pollution caused through these chemicals.

Soil erosion is controlled by: 
Using geotextiles is an effective method because it also stabilizes soil
The simplest and most natural way to prevent erosion is through planting vegetation.
Reducing deforestation and substituting chemical manures by animal wastes also helps arrest soil erosion in the long term.

The direct discharge of industrial waste into the soil causes the soil to erode and becomes useless for agriculture and any other purpose.

Waste water from industries should not be used for irrigation without eliminating toxic chemicals from the effluent.
It is a measure to control soil pollution.
This will also reduce the concentration of unwanted substances in the soil.

Industrial pollutants affect and alter the chemical and biological properties of soil.
With the advancing agro-technology, huge quantities of fertilizers, pesticides, herbicides and weedicides are added to increase the crop yield. 
Urban wastes comprise of both commercial and domestic wastes consisting of dried sludge and sewage.
all of them causes soil pollution.

Now-a-days, herbicides are frequently used in the place of pesticides. these are also chemical compounds such as $NaClO _3, Na _3AsO _3$ etc., has become more frequent but they are also toxic to mammals.

DDT is a pesticides which is used for pest control in agricultural production but not only pesticides decrease the fertility of the soil but also penetrate into crops and produce health hazards.

Pesticides are chemical compounds which are water insoluble and non-biodegradable.

Fertilizers are the chemical compound which is used in agricultural land to increase the fertility of soil. The use of fertilizers for long time makes the upper layer harder and renders the soil infertile.

A large number of heavy metal such as radium and thorium gets accumulated in the soil in the areas having metal smelting industries. These heavy metals decrease the fertility of soil.

Soil erosion is a phenomenon in which soil of an area eroded due to deforestation, over-grazing, unplanned irrigation, etc., decrease the fertility of soil.

Domestic waste particularly non-biodegradable substances such as polyethene which is used in regular household activities. and dumped.

Bio-pesticides should be used in place of toxic chemical pesticides. Organic fertilizers should be used in place of synthesized chemical fertilizers.
Ex: Organic wastes in animal dung may be used to prepare compost manure instead of throwing them wastefully and polluting the soil.

Pesticides are synthetic toxic chemicals such as DDT, Alderin, Dieldrin etc. and their repeated use makes pests resistant to that group of pesticides, thus making pesticides ineffective.

High water holding capacity is in clayey soil due to the small size of the particles; they have a much larger area.

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 can be caused by the following (non-exhaustive list):

1. Oil drilling
2. Mining and activities by other heavy industries
3. Thermal power plant
4. Accidental spills as may happen during activities, etc.
5. Corrosion of underground storage tanks (including piping used to transmit the contents)
6. Acid rain (in turn caused by air pollution)
7. Intensive farming
8. Agroindustries and chemicals, such as pesticides, herbicides and fertilizers
9. Industrial accidents
10. Road debris
11. Drainage of contaminated surface water into the soil
12. Waste disposal

Soil erosion is a naturally occurring process that affects all landforms. In agriculture, soil erosion refers to the wearing away of a field's topsoil by the natural physical forces of water and wind or through forces associated with farming activities such as tillage. It reduces the quality of soil.

Every human produces a certain amount of personal waste products by way or urine and feces. While much of it moves into the sewer the system, there is also a large amount that is dumped directly into landfills in the form of diapers. Even the sewer system ends at the landfill, where the biological waste pollutes the soil.

Radioactive wastes discharged from research centers, hospitals and industries involving uranium refining, etc., also cause soil pollution.

Growing same crop in the same land reduces soil fertility as the same crop planted repeatedly in the same area keeps draining the land of same nutrients needed for the plant's growth.

Humus refers to the fraction of soil organic matter that is amorphous and without the cellular cake structure characteristic of plants, micro-organisms or animals. Humus has a characteristic black or dark brown color and is organic due to an accumulation of organic carbon found in Horizon - A. The three major horizons are: (A) surface horizon, (B) subsoil and (C) substratum. Some soils have an organic horizon (O) on the surface. Hard bedrock, which is not soil, uses the letter R.

Afforestation is the process of planting trees, or sowing seeds, in a barren land devoid of any trees to create a forest. The benefits of this practice, which is called agroforestry, are:

1. It provides a supply of timber, fruit, and fodder for cattle apart from crop production
2. It prevents soil erosion and thus conserves soil.
3. It enables better retention of water
4. It shields crops from excessive wind and sun damage

In terms of the environmental benefits, planting trees is always beneficial whether it takes place in a barren land or is used as a method to regenerate a depleted forest. Trees help check atmospheric carbon dioxide; large scale afforestation can curb the problems caused due to burning of fossil fuels, industrialization and so forth.

When the rain droplets gets mixed with nitrogen and sulfur oxide it causes acid rain. this acid rain when fall on earth react with soil because of chemicals present in acid rain, the fertility of particular area gets affected.

Pesticides are compounds that destroy insects (pests). By the 15th century, toxic chemicals such as arsenic, mercury, and lead were being applied to crops to kill pests.

The industrial effluents passing through the field add toxic substances to the soil and decrease the soil fertility and its water-absorbing capacity.

Negative soil pollution occurs due to the overuse of soil & its erosion hence there will be a decrease in soil productivity. 

Afforestation is the establishment of a forest or stand of trees in an area where there was no previous tree cover.
Reforestation is the reestablishment of forest cover, either naturally (by natural seeding, coppice, or root suckers) or artificially (by direct seeding or planting).

Deforestation
is a major cause which leads to the change in soil properties. It
affects the nutrient content (which cannot be replenished in the soil), texture and fertility of soil (due to erosion).

Plant twigs are biodegradable. Rest of them are non-biodegradable.

Vehicles do not directly cause soil pollution. Deforestation, excessive use of fertilizers and solid wastes may cause soil pollution

Forests and grasslands are an excellent binding material that keeps the soil intact and healthy. They support many habitats and ecosystems, which provide innumerable feeding pathways or food chains to all species. Their loss would threaten food chains and the survival of many species.

DDT  is a colorless, crystalline, tasteless organochlorine compound having insecticidal impacts.

The portion of solid waste that is hazardous are oils, battery metals, heavy metals from smelting industries and organic solvents. These can in the long run, get deposited to the soils of the surrounding area and pollute them by altering their chemical and biological properties. They also contaminate drinking water aquifer sources. More than 90% of hazardous waste is produced by chemical, petroleum and metal-related industries and small 
businesses such as dry cleaners and gas stations contribute as well.

The over use of NPK fertilizers reduce quantity of vegetables and crops grown on soil over the years. It also reduces the protein content of wheat, maize, grams, etc., grown on that soil. The carbohydrate quality of such crops also gets degraded. Excess potassium content in soil decreases 
Vitamin C and carotene content in vegetables and fruits. The vegetables and fruits grown on overfertilized soil are more prone to attacks by insects and disease. 

Soil erosion occurs when the weathered soil particles are dislodged and carried away by wind or water. Deforestation, agricultural development, temperature extremes, precipitation including acid rain, and human activities contribute to this erosion. Humans speed up this process by construction, mining, cutting of timber, over cropping and overgrazing. It results in floods and cause soil erosion.

Animal wastes, papers, leaves are biodegradable. Glass pieces are non-biodegradable.

Deforestation, clearance or clearing is the removal of a forest or stand of trees where the land is thereafter converted to a non-forest use. The less the soil is covered with vegetation, mulches, crop residues, etc., the more the soil is exposed to the impact of raindrops. When a raindrop hits bare soil, the energy of the velocity detaches individual soil particles from soil clods. Thus Deforestation would decrease the water holding capacity of the soil, so statement is false and Option B is correct.

Underground soil in cities is likely to be polluted by Chemicals released by industrial wastes and industrial wastes Decomposed and partially decomposed materials of sanitary wastes Many dangerous chemicals like cadmium, chromium, lead, arsenic, selenium  products are likely to be deposited in underground soil. Similarly underground soil polluted by sanitary wastes generate many harmful chemicals.These can damage the normal activities and ecological balance in the underground soil.