How do heavy metals harm human health when they pollute soil?

Heavy metals are defined as about 60 elements with a density above or 45 elements with a density of more than 45. Arsenic and selenium are non-metals, but their toxicity and some properties are similar to those of heavy metals, so arsenic and selenium are included in the scope of heavy metal pollutants. In terms of environmental pollution, the heavy metals mainly refer to mercury, cadmium, lead, chromium and arsenic, which are biologically toxic, and also include toxic heavy metals such as zinc, copper, cobalt, nickel, tin, vanadium and other pollutants.

With the rapid development of the global economy, pollutants containing heavy metals enter the soil through various ways, causing serious soil pollution. Soil heavy metal pollution can affect the decline of crop yield and quality, and can endanger human health through the food chain, and can also lead to further deterioration of air and water environmental quality. Therefore, it has attracted wide attention from all countries in the world.

At present, there are different degrees of heavy metal pollution in the soils of all countries in the world, with an average annual emission of about 10,000 tons of HG, 3.4 million tons of Cu, 5 million tons of PB, 15 million tons of Mn, and 1 million tons of Ni [1]. There are also varying degrees of heavy metal pollution in vegetable bases and some commercial grain bases in large cities in northern China, such as Beijing, Tianjin, Xi'an, Shenyang, Jinan, Changchun, Zhengzhou and other places.

The south is relatively light, such as Fuzhou, Ningbo, Shanghai, Wuhan, Chengdu and other places. Heavy metal pollution in the soil will cause serious damage to the ecosystem. From the perspective of China's soil resources, by the end of 2000, the per capita arable land of Chinese was only hm2, and with the future economic and social development of China, such as ecological return of farmland, agricultural restructuring and natural disaster damage, soil resources will be further reduced.

Therefore, how to effectively control and control the pollution of heavy metals in the soil and improve the quality of the soil will become a very important part of the ecological and environmental protection work.

Soil heavy metal pollution refers to the excessive content of trace metal elements in the soil due to human activities, which exceeds the background value and excessive deposition, which is collectively referred to as soil heavy metal pollution. Soil heavy metals refer to the phenomenon that the heavy metals in the soil are significantly higher than the original content and cause the deterioration of the quality of the ecological environment due to the addition of metals to the soil by human activities.

Soil heavy metal hazards are:

Affects the development of plant roots and leaves; Damage to the human nervous system, immune system, skeletal system, etc., such as Minamata disease, etc.; Contaminated drinking water.

Heavy metals are metal elements that have a high density and atomic weight compared to other metals. Although heavy metals are a long-lasting element in nature, the impact of human activities such as industry and mining has led to the release of heavy metals into the soil environment, which has seriously affected soil quality and ecological health. The following analyzes the impact of heavy metals on the soil environment from the following aspects:

1. Toxic effect.

Heavy metals are easy to accumulate in the soil environment and are not easy to decompose, and if they reach a certain concentration, they are easy to cause toxic effects on the Kunchang first insects, pests, microorganisms and other ecosystems, thereby disturbing the ecological balance and not conducive to the recycling and transformation of substrates.

2. Toxic transformation.

Heavy metals are prone to highly toxic mineral transformation in the soil environment, resulting in soil pollution. For example, chromium is considered a toxic substance to most bacteria and plants, while lead is also a highly harmful metal to humans.

3. Seed germination and root growth are affected.

Heavy metals will affect the physical and chemical properties of the soil, thereby affecting the air permeability of the soil, which can easily lead to the decline of seed germination rate and the inability of roots to grow normally, thereby affecting the growth and development of plants.

4. Destruction of soil micro-ecosystems.

Soil microecosystem is an important part of the soil, and the bacteria and fungi present in the soil play an important role in the life activities of many living organisms. However, heavy metal pollution will destroy the habitat and life form of these microorganisms, thus affecting the survival and reproduction of microorganisms.

5. The cumulative effect of heavy metals.

Heavy metals are often absorbed by organisms in the soil in the form of accumulation, which will produce the phenomenon of "genetically modified", resulting in an increasing concentration of heavy metals in the soil, and then gradually migrating in the environment, which will eventually form large-scale environmental pollution.

In summary, the heavy gold rotation has a great impact on the soil environment, which also seriously affects the quality and ecological health of the soil. If it is not effectively prevented and controlled, it will have a negative impact on human society and the ecological environment. Therefore, targeted measures need to be taken to improve the soil environment and reduce the potential danger of heavy metals and other harmful substances to soil, ecosystems and humans.

Soil refers to the loose surface layer of the land surface that is fertile and capable of growing plants, and its thickness is generally about 2 m. Soil not only provides mechanical support for plant growth, but also provides water, fertilizer, gas, heat and other fertility elements required for plant growth and development. In recent years, due to the rapid growth of population and the rapid development of industry, solid waste has been piled up and dumped on the soil surface, harmful wastewater has been infiltrating into the soil, and harmful gases and dust in the atmosphere have also been falling into the soil with rain, resulting in soil pollution.

Any substance that hinders the normal function of the soil, reduces the yield and quality of crops, and indirectly affects human health through grains, vegetables, fruits, etc., is called soil pollutants. There are many types of soil pollutants, which can be roughly divided into two categories: inorganic pollutants and organic pollutants. Inorganic pollutants mainly include acids, alkalis, heavy metals (copper, mercury, chromium, cadmium, nickel, lead, etc.), salts, radioactive elements cesium, strontium compounds, arsenic, selenium, fluorine compounds, etc.

Organic pollutants mainly include organic pesticides, phenols, cyanide, petroleum, synthetic detergents, 3,4-benzo, and harmful microorganisms brought by municipal sewage, sludge and manure. When the soil contains too many harmful substances, exceeding the self-purification ability of the soil, it will cause changes in the composition, structure and function of the soil, microbial activities are inhibited, and harmful substances or their decomposition products gradually accumulate in the soil, and are indirectly absorbed by the human body through "soil, plants, and human body", or through "soil, water, and human body", reaching the degree of endangering human health, which is soil pollution. In order to control and eliminate soil pollution, it is first necessary to control and eliminate soil pollution sources, strengthen the management of industrial "three wastes", and rationally apply chemical fertilizers and pesticides.

At the same time, control measures should be taken, such as planting plants with strong absorption capacity for the types of soil pollutants and reducing the content of toxic substances (for example, plants of the genus Iron Horn Fern can absorb heavy metals in the soil); or purify the soil through biodegradation (for example, earthworms can degrade pesticides, heavy metals, etc.); or apply inhibitors to change the migration and transformation direction of pollutants in the soil, reduce the absorption of crops (such as applying lime), increase the pH of the soil, and promote the formation of hydroxide precipitation of cadmium, mercury, copper, zinc, etc. In addition, soil pollution can also be controlled by increasing organic fertilizer, changing the farming system, changing the soil, and deep ploughing.