Brief Introduction of Soil Pollution in China

The increasingly serious soil pollution reduces the quality of a large number of crops, and even contains substances harmful to human health, which poses a great threat to human health. There are many reasons for soil pollution, mainly in the following aspects:

1, irrational use of chemical fertilizers and pesticides

According to statistics, China's annual consumption of chemical fertilizers has exceeded 4 1 10,000 tons, making it the largest consumer of chemical fertilizers in the world [2]. In order to increase the income of agricultural products, fertilizers containing phosphorus and nitrogen are widely used. Long-term use of these fertilizers will destroy soil structure, disturb the balance of nutrients in soil, cause soil agglomeration, deteriorate soil quality and reduce water storage function. The quantity of agricultural products has been greatly improved, but the quality is worrying. Because excessive use of chemical fertilizers will cause some crops to absorb too much nitrate during their growth, animals or humans will affect the transport of oxygen in their bodies after eating these crops containing nitrate, making them sick and even dead in serious cases.

Similarly, the use of a large number of pesticides has also caused great harm to the soil. Most pesticides are organic pesticides and contain many harmful chemicals, such as phenoxyalkanoate pesticides, polycyclic aromatic hydrocarbons, dioxins, phthalates and so on. Nearly 65,438+0/2 of these harmful chemicals will remain in the soil. With the passage of time, under the interaction of biological, abiotic and sunlight, harmful chemicals will become the components of soil. Crops planted in the soil will absorb harmful substances from the soil, accumulate in plant roots, stems, leaves, fruits and seeds, and cause various diseases after being eaten by people and animals.

2. Soil pollution caused by heavy metal elements

Excessive use of agricultural chemicals and the intensification of industrial pollution make heavy metal pollution increasingly serious. There are three main sources of heavy metals in soil: heavy metals entering the soil with solid waste, heavy metals entering the soil with sewage irrigation and heavy metals entering the soil with atmospheric deposition. There are many kinds of solid waste with complex structure, among which the solid waste produced by industry and mining is the most serious pollution. Solid waste contains a lot of heavy metals, which will be absorbed and diffused by soil through the action of sunlight and rain. Domestic sewage, petrochemical sewage, industrial and mining sewage and urban mixed sewage are the four major sources of sewage. Sewage contains a lot of heavy metals such as lead, chromium, mercury and copper. Unreasonable discharge or treatment of sewage will lead to the transfer of heavy metal elements in sewage to soil, thus affecting the deterioration of soil quality. After all these heavy metal pollutants enter the soil, most microorganisms are difficult to decompose because of poor fluidity and long retention time, and finally they can harm human beings through water, plants and other media.

3. Soil pollution caused by livestock manure and biological residues.

Livestock and human feces and wastes from slaughter are often directly discharged into the soil without effective treatment. Among them, parasites and viruses will pollute soil and water, sometimes poison soil and change the original normal state of soil, and harmful soil will eventually harm human beings through water and crops.

4. Soil pollution caused by sewage irrigation

China is a big agricultural country, which needs a lot of water to irrigate crops. However, the water veins are all connected. Once domestic sewage and industrial wastewater are discharged without scientific treatment, a large amount of sewage flows to farmland, and crops irrigated by sewage will carry a variety of harmful substances, which will make people and animals sick after eating.

5, air pollution on soil pollution

Harmful substances in the atmosphere, such as sulfur oxides, nitrogen oxides, particulate matter, etc., form acid rain through various chemical and physical reactions and enter the soil to acidify the soil. Metal oxide dust discharged from metallurgical industry enters the soil in the form of dust reduction under the action of gravity, forming point pollution with a radius of 2 ~ 3 km around the sewage plant [3]. This will change the soil composition, affect the soil properties, and is not conducive to plant growth.

6. Soil erosion

Soil erosion mainly includes desertification, sandstorm and desertification. Earth ulcer is an image description of land desertification. Water erosion, salinization and rocky desertification in the natural environment make the earth ulcer more and more serious. For example, the loess high slope in China is mainly composed of silt, which has poor adhesion and is easily dissolved by water. In case of torrential rain, it will be washed away by water, which is not conducive to the growth of vegetation and the survival of organisms, and will also cause siltation in the river bed and reduce the flood storage and drainage capacity of rivers and lakes. In recent years, the incidence of sandstorms in many cities in China has soared, which is closely related to soil wind erosion caused by excessive grassland reclamation and excessive tree felling. Wind erosion and soil erosion are serious, and vegetation growth is difficult, which makes most of the land unusable.