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The Causes and Consequences of Soil Pollution

Soil pollution means that the pollutants generated by human activities enter the soil through various paths. The quantity and speed of the pollutants exceed the soil's containment and purification ability, so that the nature, composition and properties of the soil will change, and the accumulation process of pollutants gradually takes advantage. Soil pollution destroys the natural ecological balance of the soil, and causes the natural function of the soil to be imbalanced and soil quality deteriorates.

What are the main causes of soil pollution?

  1. Pesticides

Pesticides can prevent and control diseases, insects, and weeds. If used properly, they can increase crop yields. However, they are a very harmful soil pollutant. Improper application can cause soil contamination. Only half of the pesticides (powders, liquids, emulsions, etc.) sprayed on crops are partially absorbed by plants or escaped into the atmosphere. Kinds of disinfectants, underground pest fumigants and pesticides, etc. constitute the basic source of pesticides in farmland soil. Crops absorb pesticides from the soil, accumulate in roots, stems, leaves, fruits and seeds, and endanger the health of humans and livestock through food and feed. At present, there are about 50 kinds of chemical pesticides in use. Among them, the main packages are rich in organophosphorus pesticides, organochlorine pesticides, carbamates, phenoxycarboxylic acids, phenols, and amines. In addition, petroleum, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, methane, and harmful microorganisms are also common organic pollutants in the soil. Organophosphorus pesticides account for 70% of pesticides, and 70% of organophosphorus pesticides are highly toxic species, resulting in many pesticide residues and serious soil pollution.

  1. Chemical fertilizer

The application of chemical fertilizers is an important measure to increase agricultural production, but unreasonable use can also cause soil pollution. Long-term large-scale use of nitrogen fertilizer will destroy the soil structure, cause soil compaction, deterioration of biological properties, and affect the yield and quality of crops.

  1. Heavy metals

The use of heavy metal-rich wastewater for irrigation is an important pathway for heavy metals to enter the soil. Another path is to fall into the soil with atmospheric deposition. The main heavy metals are mercury, copper, zinc, chromium, nickel, cobalt, etc. For example, industrial wastewater from smelting, electroplating, fuel and mercury compounds can cause heavy metal pollution such as cadmium, mercury, chromium and copper; industrial wastewater from petrochemicals, fertilizers and pesticides can cause organic pollution such as phenol, trichloroacetaldehyde and pesticides. Because heavy metals cannot be differentiated by microorganisms, and can be enriched by microorganisms, once the soil is contaminated by heavy metals, its natural purification process and artificial management are very difficult. If the wastewater is used directly for irrigation without necessary treatment, the toxic and harmful substances in the wastewater will be brought to the farmland and pollute the soil.

4、Radioactive element

Radioactive elements are mainly derived from the fallout from atmospheric nuclear experiments, as well as from various exhaust gases, wastewater and sludge emitted during the peaceful use of atomic energy. Radioactive element-rich materials inevitably contaminate the soil with natural sedimentation, rain water and waste accumulation. Once the soil is contaminated by radioactive substances, it is difficult to eliminate itself, and can only decay naturally into stable elements, and eliminate its radioactivity. Radioactive elements can enter the human body through the food chain.

5、Pathogenic microorganism

The pathogenic microorganisms in the soil contain, first and foremost, pathogenic bacteria and viruses. They come from human and animal manure and sewage used for irrigation (untreated daily sewage, especially hospital sewage). If people work with soil rich in pathogenic microorganisms or eat vegetables and fruits contaminated by soil, they will be directly harmed.

6、Solid contamination

Industrial waste and municipal waste are solid pollutants of soil. For example, various agricultural plastic films are widely used as greenhouses and mulch, and if they are not well managed and recycled, a large amount of residual film fragments will be scattered in the fields, causing "white pollution" on farmland. Such solid pollutants are not easy to evaporate and volatilize, nor are they easily decomposed by soil microorganisms, which is a kind of pollutant that stays in the soil for a long time.

7、Exhaust gas

The harmful gases in the atmosphere are mainly toxic exhaust gases emitted from industries, which have a large pollution surface and can cause serious pollution to the soil. Industrial waste gas pollution is broadly divided into two categories: the first category is gas pollution, such as sulfur dioxide, fluoride, ozone, nitrogen oxides, hydrocarbons, etc.; the second category is aerosol pollution, such as dust, soot and other solid particles and smoke, fog and other liquid particles, which enter the soil through precipitation. The exhaust gas from non-ferrous metal smelters contains heavy metals such as chromium, lead, copper and cadmium, which cause pollution to the nearby soil. factories producing phosphate fertilizer and fluoride can cause dust pollution and fluorine pollution to the nearby soil. SO2, NO and other harmful gases emitted by industries react in the atmosphere and form acid rain, which enters the soil in the form of natural precipitation and causes soil acidification. Metallurgical industry chimney emissions of metal oxide dust, then under the action of gravity in the form of dustfall into the soil, the formation of sewage plants as the center, the radius of 2 to 3 km range of point pollution. The explosion-proof agent tetraethyl lead added in gasoline is discharged with exhaust gas to pollute the soil, and obvious lead pollution zones are often formed on both sides of roads with high traffic frequency.

What are the harms of soil pollution?

Soil pollution has brought about serious consequences.

1、Soil pollution is cutting off the already limited arable land.

2、Soil pollution poses a great threat to people's health. Soil pollution will accumulate pollutants in plant (crop) objects and enrich into human and animal bodies through the food chain, endangering human and animal health and causing cancer and other diseases.

3、 It has a great adverse impact on agricultural development. Soil pollution leads to serious direct economic losses such as decline in soil quality, crop yield and quality.

4、 Soil pollution is also an important cause of other environmental pollution. After the land is polluted, the contaminated topsoil containing high concentrations of heavy metals is easy to enter the atmosphere and water bodies under the action of wind and water forces respectively, leading to atmospheric pollution, surface water pollution, groundwater pollution and ecosystem degradation and other secondary ecological and environmental problems.

5、Pollutants in soil pollution are migratory and retention, and may continue to cause new land pollution.

6、Soil pollution is not conducive to the sustainable development of the rural economy and seriously endangers the interests of future generations.

What are the measures to control soil pollution?

  1. Scientific use of wastewater. There are many kinds of wastewater, some may be non-toxic, but after mixing with other wastewater, it becomes toxic. Therefore, when using wastewater to irrigate farmland, it must be treated to meet the standard requirements before it can be used to irrigate farmland.
  2. Rational use of pesticides, and actively develop high-efficiency and low residue pesticides. The scientific use of pesticides can effectively eliminate crop pests and play a positive role in pesticides. The staff using pesticides must understand the relevant knowledge of pesticides in order to reasonably choose the scope of use of different pesticides, the number of spraying, application time and dosage, etc., so as to minimize the pollution of soil by pesticides. Prohibit the use of pesticides with long residual timeand develop pesticides that arehighly efficient and less residual, such as pyrethroid pesticides, which will help reduce the pollution of soil by pesticides.
  3. Actively promote biological control of pests and diseases. In order to both effectively prevent and control agricultural pests and diseases and reduce the pollution of chemical pesticides, it is necessary to actively promote biological control methods, the use of beneficial birds, beneficial insects and certain pathogenic microorganisms to prevent and control agricultural and forestry pests and diseases. For example, the protection of a variety of insect-feeding beneficial birds; the use of red-eyed wasps, ladybugs, spiders and other beneficial insects to prevent and control a variety of grain, cotton, vegetables, oil crops and forestry pests; the use of stem borer bacteria, cyanobacteria and other microorganisms to prevent and control corn borers, pine caterpillars, etc.. The use of biological methods to prevent agricultural and forestry pests and diseases is economic, safe, effective and non-polluting.
  4. Application of chemical improvers. The application of inhibitors in soils lightly contaminated by heavy metals can convert heavy metals into insoluble compounds and reduce the uptake by crops. Commonly used inhibitors include lime, alkaline phosphate, carbonate and sulfide. For example, the application of lime or alkaline furnace ash, etc. in acidic and slightly acidic soils contaminated with cadmium can convert active cadmium into insoluble compounds such as carbonates or hydroxides, with significant improvement effects. Because most of the heavy metals are pro-sulfur elements, the application of green manure and rice straw in paddy fields and the application of appropriate amounts of sodium sulfide and lithosulfur compound on dry land are conducive to the generation of insoluble sulfides from heavy metals.
  5. Raise the public awareness of soil protection. Soil protection consciousness refers to the thoughts, views, knowledge and psychology of a specific subject on soil protection, including a specific subject's view on the nature, role and value of soil, the evaluation and understanding of soil, the understanding and measurement of using soil, the awareness of their rights and obligations on soil protection, and the concept of a specific subject. When developing and utilizing soil, public opinion and propaganda work should be further strengthened so that all cadres and people know that the soil issue is a major matter of national security. Let farmers and grassroots cadres fully understand the current serious soil situation and arouse their sense of worry, urgency and historical mission.