One question per week: What are the prevention and control measures against heavy metal pollution, and what are its hazards?

Heavy metal pollution mainly originates from these heavy metals: lead, copper, mercury, bismuth, cadmium, arsenic, chromium, fluorine, and nickel. Lead causes damage to various systems such as the nervous system, blood, digestive system, cardiovascular and cerebrovascular systems, as well as the urinary system; it severely disrupts metabolism in the body, leading to low levels of calcium, zinc, and iron. It takes 20 years for half of the lead in the bones to be eliminated. Whitening cosmetics containing mercury can cause contact dermatitis, erythematous papules, and blisters, and lead to increased pigmentation on the face after recovery. Cosmetics containing lead can easily cause acne, erythema, peeling, allergic dermatitis, skin cancer, disfigurement, etc. Long-term accidental ingestion of bismuth in lipsticks can cause damage to the liver and kidneys. Chromium is irritating and sensitizing to the skin, causing redness, swelling, and ulcers ； Its smoke and dust cause significant damage to the respiratory tract, potentially leading to ulcers of the nasal mucosa, pharyngitis, pneumonia, and gastrointestinal ulcers. Fluorosis is a chronic disease characterized by dental fluorosis and skeletal fluorosis ； Excessive levels of chromium and nickel are harmful to the internal organs and the nervous system, and they are difficult to degrade. Governance methods and characteristics: include engineering governance, biological governance, chemical governance, and agricultural governance methods. Engineering treatment provides thorough and stable results, but it is complex to implement, costly, and can lead to a decline in soil fertility ； Biological treatment is easy to implement, requires low investment, and causes minimal environmental damage, but its treatment effects are not ideal ； The effectiveness and cost of chemical treatment methods are moderate; however, they are prone to re-activation ； Agricultural governance methods are easy to implement and low-cost, but they have a long cycle time and modest results. In summary, depending on the characteristics of different pollution types and the requirements regarding treatment effectiveness, duration, and costs, the most suitable treatment method should be chosen. Chemical stabilization methods often fail to ensure long-term stability in treatment effectiveness, but the molecular bonding repair technology, which has received considerable attention recently, can effectively address this issue; it will thus become an optimal treatment method that combines good effectiveness, low costs, and a short treatment period.

1. Major sources of toxic metals: The main sources of toxic metal contamination in aquatic animals can be divided into exogenous and endogenous (biomagnification) sources. Exogenous sources of contamination include feed, water quality, sediment, air, drugs, etc. 1.1 Contamination of feed with toxic chemicals In modern large-scale intensive aquaculture, the feed used in high-quality farming systems generally contains pharmaceutical additives designed to promote animal growth and prevent diseases; however, excessive use leads to drug residues that are toxic and have adverse effects on the farmed aquatic animals. Furthermore, certain amounts of pesticides are inevitably applied during the cultivation of plant-based feed ingredients, resulting in pesticide residues in the crops; as a result, the grains used as fish feed, along with their skins and shells, necessarily contain certain levels of residual pesticides. 1.2 Pollution by toxic chemicals in water bodies: Water is subject not only to biological pollution, but also to serious chemical pollution problems. The main sources of heavy metal pollution in water bodies are untreated industrial wastewater and domestic sewage ； Oil spills from tankers, as well as pesticides washed into rivers by rainwater, can cause heavy metals such as mercury to accumulate in the sediment at the bottom of water bodies. Heavy metal pollution of water quality is extremely complex. Commonly found inorganic substances include heavy metals such as mercury, lead, copper, zinc, arsenic, aluminum, and barium, as well as cyanides and fluorides. Fish live in water throughout their lives; the water they inhale while breathing contains certain heavy metals, which enter the systemic circulation via the mouth. Moreover, heavy metals can easily adhere to the fish’s surface and enter their bodies as well. 1.3 Pollution by toxic chemicals in soil Toxic chemicals in soil mainly include heavy metal elements such as mercury, lead, cadmium, copper, manganese, zinc, and arsenic. The toxic chemicals that contaminate the soil mainly originate from industrial waste, pesticides, fertilizers, garbage and sewage, as well as manure that has not been properly treated. Due to rainwater erosion, large amounts of heavy metal pollutants enter the soil, thereby indirectly causing heavy metal contamination in aquatic products. 1.4 Pollution by toxic chemical substances in the air due to human production. In daily activities, exhaust gases emitted from fuel combustion, and industrial production releases heavy metals such as mercury, lead, cadmium, zinc, and arsenic. Industrial waste gases such as those containing alum and barium are released into the air, where they gradually spread outward. They either settle naturally or are deposited into soil and water bodies along with raindrops, causing pollution. Pollution of feed, air, water, and soil is not isolated; rather, these elements are interconnected and influence one another. Pollutants transform and migrate among these four elements, creating a cyclic pollution in the environment, which in turn leads to direct or indirect contamination of aquatic products by toxic chemicals. 　　 2 Hazards of heavy metal pollution: Lead causes damage to various systems such as the nervous system, blood, digestive system, cardiovascular and cerebrovascular systems, as well as the urinary system; it severely affects metabolism in the body, leading to low levels of calcium, zinc, and iron. It takes 20 years for half of the lead in the bones to be eliminated. Whitening cosmetics containing mercury can cause contact dermatitis, erythematous papules, and blisters, and lead to increased pigmentation on the face after recovery. Cosmetics containing lead can easily cause acne, erythema, peeling, allergic dermatitis, skin cancer, disfigurement, etc. Long-term accidental ingestion of bismuth in lipsticks can cause damage to the liver and kidneys. Chromium is irritating and sensitizing to the skin, causing redness, swelling, and ulcers ； Its smoke and dust cause significant damage to the respiratory tract, potentially leading to ulcers of the nasal mucosa, pharyngitis, pneumonia, and gastrointestinal ulcers. Fluorosis is a chronic disease characterized by dental fluorosis and skeletal fluorosis ； Excessive levels of chromium and nickel are harmful to the internal organs and the nervous system, and they are difficult to degrade. 3 Methods for preventing and controlling heavy metal pollution. Since the use of pesticides, antibiotics, sulfonamides, and other chemicals remains one of the important measures for preventing and controlling pests and diseases in animals and plants, as well as for promoting the growth of livestock, poultry, and crops, the continued use of such chemicals in agriculture, animal husbandry, and fisheries is inevitable; moreover, the types and quantities of these chemicals used are constantly increasing. The pollution of the environment by industrial waste, wastewater, and waste gas remains a serious problem. Therefore, to protect the environment and prevent contamination of animal-based foods, preventive and control measures are necessary. The main measures can be summarized as follows: 3.1 Actively manage industrial waste streams to eliminate the contamination of animal-based foods by toxic chemicals; relevant industrial enterprises should actively reform their production processes. Eliminate industrial waste, emissions, and pollutants during the production process. At the same time, it is necessary to actively carry out environmental analysis and food hygiene testing. 3.2 Strengthen the regulation of the production and use of highly toxic pesticides, and stop using pesticides containing mercury and arsenic. Actively develop new varieties of pesticides that are highly effective, low-toxicity, and have low residues, in order to reduce the amount of drug residues in aquatic products. 3.3 Strengthen the use and management of fish medicines by establishing necessary regulations regarding the types of drugs used, the target species, methods of application, dosages, and usage conditions, in order to prevent abuse. The use of antibiotics that easily lead to resistance should be prohibited. A withdrawal period must be stipulated; there should be a certain withdrawal period before aquatic products can be harvested. 3.4 Prohibition of the abuse of food additives: When additives must be used in food production, toxicity, harmlessness, and nutritional safety must be given top priority. Food additives should be used as little as possible or not at all. When using additives, it is necessary to strictly adhere to the **established hygiene standards for food additives, and excessive or improper use is strictly prohibited. 3.5 Actively carry out testing for contamination and residual toxins in animal-based foods, and strictly comply with the regulations set forth in China’s food hygiene standards regarding the allowable levels of toxic chemicals; these levels must not be exceeded. Strengthen the testing of heavy metal levels in fish and shellfish; if severe pollution of such organisms is detected in a particular water area, fishing, selling, and consumption should be prohibited.

1. Major sources of toxic metals: The main sources of toxic metal contamination in aquatic animals can be divided into exogenous and endogenous (biomagnification) sources. Exogenous sources of contamination include feed, water quality, sediment, air, drugs, etc. 1.1 Contamination of feed with toxic chemicals In modern large-scale intensive aquaculture, the feed used in high-quality farming systems generally contains pharmaceutical additives designed to promote animal growth and prevent diseases; however, excessive use leads to drug residues that are toxic and have adverse effects on the farmed aquatic animals. Furthermore, certain amounts of pesticides are inevitably applied during the cultivation of plant-based feed ingredients, resulting in pesticide residues in the crops; as a result, the grains used as fish feed, along with their skins and shells, necessarily contain certain levels of residual pesticides. 1.2 Pollution by toxic chemicals in water bodies: Water is subject not only to biological pollution, but also to serious chemical pollution problems. The main sources of heavy metal pollution in water bodies are untreated industrial wastewater and domestic sewage ； Oil spills from tankers, as well as pesticides washed into rivers by rainwater, can cause heavy metals such as mercury to accumulate in the sediment at the bottom of water bodies. Heavy metal pollution of water quality is extremely complex. Commonly found inorganic substances include heavy metals such as mercury, lead, copper, zinc, arsenic, aluminum, and barium, as well as cyanides and fluorides. Fish live in water throughout their lives; the water they inhale while breathing contains certain heavy metals, which enter the systemic circulation via the mouth. Moreover, heavy metals can easily adhere to the fish’s surface and enter their bodies as well. 1.3 Pollution by toxic chemicals in soil Toxic chemicals in soil mainly include heavy metal elements such as mercury, lead, cadmium, copper, manganese, zinc, and arsenic. The toxic chemicals that contaminate the soil mainly originate from industrial waste, pesticides, fertilizers, garbage and sewage, as well as manure that has not been properly treated. Due to rainwater erosion, large amounts of heavy metal pollutants enter the soil, thereby indirectly causing heavy metal contamination in aquatic products. 1.4 Pollution by toxic chemical substances in the air due to human production. In daily activities, exhaust gases emitted from fuel combustion, and industrial production releases heavy metals such as mercury, lead, cadmium, zinc, and arsenic. Industrial waste gases such as those containing alum and barium are released into the air, where they gradually spread outward. They either settle naturally or are deposited into soil and water bodies along with raindrops, causing pollution. Pollution of feed, air, water, and soil is not isolated; rather, these elements are interconnected and influence one another. Pollutants transform and migrate among these four elements, creating a cyclic pollution in the environment, which in turn leads to direct or indirect contamination of aquatic products by toxic chemicals. 　　 2 Hazards of heavy metal pollution: Lead causes damage to various systems such as the nervous system, blood, digestive system, cardiovascular and cerebrovascular systems, as well as the urinary system; it severely affects metabolism in the body, leading to low levels of calcium, zinc, and iron. It takes 20 years for half of the lead in the bones to be eliminated. Whitening cosmetics containing mercury can cause contact dermatitis, erythematous papules, and blisters, and lead to increased pigmentation on the face after recovery. Cosmetics containing lead can easily cause acne, erythema, peeling, allergic dermatitis, skin cancer, disfigurement, etc. Long-term accidental ingestion of bismuth in lipsticks can cause damage to the liver and kidneys. Chromium is irritating and sensitizing to the skin, causing redness, swelling, and ulcers ； Its smoke and dust cause significant damage to the respiratory tract, potentially leading to ulcers of the nasal mucosa, pharyngitis, pneumonia, and gastrointestinal ulcers. Fluorosis is a chronic disease characterized by dental fluorosis and skeletal fluorosis ； Excessive levels of chromium and nickel are harmful to the internal organs and the nervous system, and they are difficult to degrade. 3 Methods for preventing and controlling heavy metal pollution. Since the use of pesticides, antibiotics, sulfonamides, and other chemicals remains one of the important measures for preventing and controlling pests and diseases in animals and plants, as well as for promoting the growth of livestock, poultry, and crops, the continued use of such chemicals in agriculture, animal husbandry, and fisheries is inevitable; moreover, the types and quantities of these chemicals used are constantly increasing. The pollution of the environment by industrial waste, wastewater, and waste gas remains a serious problem. Therefore, to protect the environment and prevent contamination of animal-based foods, preventive and control measures are necessary. The main measures can be summarized as follows: 3.1 Actively manage industrial waste streams to eliminate the contamination of animal-based foods by toxic chemicals; relevant industrial enterprises should actively reform their production processes. Eliminate industrial waste, emissions, and pollutants during the production process. At the same time, it is necessary to actively carry out environmental analysis and food hygiene testing. 3.2 Strengthen the regulation of the production and use of highly toxic pesticides, and stop using pesticides containing mercury and arsenic. Actively develop new varieties of pesticides that are highly effective, low-toxicity, and have low residues, in order to reduce the amount of drug residues in aquatic products. 3.3 Strengthen the use and management of fish medicines by establishing necessary regulations regarding the types of drugs used, the target species, methods of application, dosages, and usage conditions, in order to prevent abuse. The use of antibiotics that easily lead to resistance should be prohibited. A withdrawal period must be stipulated; there should be a certain withdrawal period before aquatic products can be harvested. 3.4 Prohibition of the abuse of food additives: When additives must be used in food production, toxicity, harmlessness, and nutritional safety must be given top priority. Food additives should be used as little as possible or not at all. When using additives, it is necessary to strictly adhere to the **established hygiene standards for food additives, and excessive or improper use is strictly prohibited. 3.5 Actively carry out testing for contamination and residual toxins in animal-based foods, and strictly comply with the regulations set forth in China’s food hygiene standards regarding the allowable levels of toxic chemicals; these levels must not be exceeded. Strengthen the testing of heavy metal levels in fish and shellfish; if severe pollution of such organisms is detected in a particular water area, fishing, selling, and consumption should be prohibited.

Heavy metal pollution refers to environmental pollution caused by heavy metals or their compounds. It is mainly caused by human factors such as mining, exhaust gas emissions, wastewater irrigation, and the use of heavy metal products. Human activities have led to an increase in heavy metal concentrations in the environment, exceeding normal levels and resulting in a deterioration of environmental quality. The main source of heavy metal pollution is industrial pollution, followed by traffic pollution and household waste pollution. Industrial pollution is mostly released into the environment through waste residues, wastewater, and exhaust gases; it accumulates in humans, animals, and plants, thereby causing significant harm to the environment and human health. The control of industrial pollution can be achieved through various technical methods and management measures to reduce its levels, ultimately meeting the established standards for pollutant discharge and preventing heavy metal contamination in tea ； Traffic pollution is mainly caused by vehicle exhaust emissions; **a range of control measures have been established, such as using ethanol-blended gasoline and installing exhaust purification systems in vehicles** ； Domestic pollution mainly stems from household waste, such as used batteries, broken light bulbs, unused cosmetics, and glazed dishes. As for heavy metal pollution, we can more or less reduce it by controlling its sources. 　　 Experts analyze that the relatively backward processes, equipment, and technological research and development in China’s plastic manufacturing enterprises are the main causes of severe pollution. Poor management, local protectionism, and low environmental awareness among people further exacerbate this pollution, making it urgent to strengthen pollution control measures. Manufacturing enterprises should look to the future, advocate environmental protection, and use eco-friendly additives in order to ensure the healthy and sustainable development of the PVC industry. Controlling and eliminating sources of soil pollution are the fundamental measures to prevent pollution. The soil’s ability to purify pollutants is equivalent to a certain capacity for treatment. Control soil pollution sources, that is, control the amount and rate of pollutants entering the soil, so as to prevent soil pollution through its natural purification processes. 1) Control and eliminate the emission of industrial ’three wastes’. 2) Strengthen the monitoring and management of soil areas contaminated by pollutants. 3) Apply fertilizers and pesticides in a rational manner. 4) Increase soil capacity and enhance its purification ability. 5) Establish a monitoring system network to regularly inspect the soil environmental quality in the relevant areas, and create systematic records. Priority should be given to identifying the soil pollutants that need to be monitored as well as the standard methods for testing them. In this regard, objectives for addressing soil environmental pollution can be formulated by referring to the recommendations of relevant international organizations and China’s national conditions, with investigations, research, and implementation of countermeasures carried out in order of priority.

Heavy metal pollution refers to environmental pollution caused by heavy metals or their compounds. It is mainly caused by human factors such as mining, exhaust gas emissions, wastewater irrigation, and the use of heavy metal products. Human activities have led to an increase in heavy metal concentrations in the environment, exceeding normal levels and resulting in a deterioration of environmental quality. The degree of harm depends on the concentration and chemical forms of heavy metals present in the environment, food, and organisms. Heavy metal pollution is mainly manifested in water pollution, with some also present in the atmosphere and solid waste. In early April 2011, China’s first special plan for the 12th Five-Year Plan period – the \"12th Five-Year Plan for the Comprehensive Control of Heavy Metal Pollution\" – was officially approved by the State Council; this control plan aimed to manage five types of heavy metals. Heavy metals in the human body can interact strongly with proteins and various enzymes, rendering them inactive. They may also accumulate in certain organs of the body; if this accumulation exceeds the limits that the body can tolerate, it can lead to acute, subacute, or chronic poisoning, causing serious harm to the body. For example, diseases such as Minamata disease (caused by mercury pollution) and Itai-Itai disease (caused by cadmium pollution) in Japan are both resulting from heavy metal contamination. 　　Heavy metals are widely distributed in the atmosphere, water bodies, soil, and organisms, while sediment often serves as a reservoir and ultimate destination for heavy metals. When the environment changes, the forms of heavy metals in the sediment undergo transformation and are released, causing pollution. Heavy metals cannot be biodegraded; however, they are bioaccumulative and can directly pose a threat to higher organisms, including humans. Experts point out that soil contamination by heavy metals is irreversible. Soil already contaminated by such metals has no remedial value; the only solution is to adjust the types of crops grown in order to avoid the problem. Primary hazard: Environmental pollution. In terms of environmental pollution, heavy metals refer to mercury, cadmium, lead, and \"metalloids\" such as arsenic, which are heavy metals with significant biological toxicity. The five most toxic to the human body are: lead, mercury, arsenic, and cadmium. These heavy metals cannot be broken down in water; when consumed by humans, their toxicity increases, and they combine with other toxins in water to form more toxic organic compounds. 　　Soil pollution can be remediated using plants that are resistant to heavy metals; such plants can also be used in amusement parks and other non-agricultural areas. The United States has examples of this, and in Tongling, Anhui, copper tailings have been treated through phytoremediation in collaboration with Australia, and initial results have already been seen. 　　Heavy metals are generally present in nature at natural concentrations, but as human activities such as mining, smelting, processing, and commercial production of heavy metals increase, many of these metals—including lead, mercury, cadmium, and cobalt—end up in the atmosphere, water, and soil, causing severe environmental pollution. Human injury: Heavy metals existing in various chemical states or forms, once they enter the environment or ecosystems, remain there, accumulate, and migrate, thereby causing harm. Heavy metals discharged with wastewater, even at low concentrations, can accumulate in algae and sediment, and be adsorbed onto the surfaces of fish and shellfish, leading to biomagnification through the food chain and thereby causing environmental pollution. As in Minamata disease in Japan, it was caused by mercury contained in the wastewater discharged from the caustic soda manufacturing industry, which was then converted into organic mercury through biological processes ； Another example is itai-itai disease, which is caused by cadmium emitted from the zinc smelting industry and the cadmium plating industry. Lead emitted from vehicle exhaust enters the environment through processes such as atmospheric dispersion, resulting in a significant increase in lead concentrations in the soil. This has led to human bodies absorbing about 100 times more lead in recent times compared to ancient humans, thereby harming human health. Heavy metals cause great harm to the human body. Common examples include: Mercury: After ingestion, it settles directly in the liver and causes severe damage to the brain, nerves, and vision. In natural water, 0.01 milligrams per liter can cause poisoning in humans. 　　Cadmium: Causes high blood pressure and leads to cardiovascular and cerebrovascular diseases ； It damages bones as well as the liver and kidneys, and can cause kidney failure. Lead: It is one of the most toxic heavy metals; once it enters the body, it is difficult to eliminate. It can directly damage human brain cells, especially the nervous system of fetuses, leading to congenital intellectual disability. Cobalt: It can cause radioactive damage to the skin. 　　Vanadium: Damages the heart and lungs, leading to abnormal cholesterol metabolism. 　　Antimony: Along with arsenic, it can turn silver jewelry a brick red color and cause radioactive damage to the skin. 　　Thallium: It can cause polyneuritis. 　　Manganese: Excessive amounts can cause hyperthyroidism. It can also damage vital organs. 　　Arsenic: It is one of the components of arsenic trioxide; it is highly toxic and can cause rapid death. Long-term exposure to small amounts can lead to chronic poisoning. Additionally, there is carcinogenicity. 　　Any of these heavy metals can cause headaches, dizziness, insomnia, forgetfulness, mental confusion, joint pain, kidney stones, and cancer. 　　In recent years, cases of heavy metal pollution have become increasingly common – from the issue of elevated lead levels in children’s blood in Hunan, to hundreds of children in Fengxiang, Shaanxi, having excessive lead levels in their blood, as well as problems related to heavy metals in food products. Recently, Southern Weekend reported that heavy metal contamination also exists in water dispensers, indicating that heavy metal pollution has affected our living environment. The plastic doors and windows we commonly see are also contaminated with the heavy metal lead. Plastic doors and windows belong to PVC profiles, and the main heat stabilizer systems used for PVC profiles include lead salts, organotin compounds, calcium-zinc stabilizers, and their composite stabilizers. Due to its excellent stabilizing effect, lead salt stabilizers are currently the most widely used stabilizers in the production of plastic doors and windows in China. However, because of the toxicity of lead, they pose a threat to the environment and human health, even though they do not come into direct contact with the human body. Lead stabilizers are not allowed in rigid PVC doors and windows in North America. These are clearly stipulated in Health Canada’s Document 1996-48, as well as in the U.S. Consumer Product Safety Commission’s Documents 96-150 and 4426. However, the pollution problem caused by lead salt stabilizers has not yet received sufficient attention in our country. Control methods: Controlling and eliminating soil pollution sources. Controlling and eliminating soil pollution sources is the fundamental measure to prevent pollution. The soil’s ability to purify pollutants is equivalent to a certain capacity for treatment. Control soil pollution sources, that is, control the amount and rate of pollutants entering the soil, so as to prevent soil pollution through its natural purification processes. 　　1) Controlling and eliminating the emission of industrial \"three wastes\" 　　Vigorously promote closed-loop systems and non-toxic processes to reduce or eliminate the emission of pollutants. Recycle industrial waste, turning harm into benefit. The emitted \"three wastes\" must be purified, and the amounts and concentrations of pollutants must be strictly controlled to meet the emission standards. 　　2) Strengthen the monitoring and management of soil irrigation areas. In areas where sewage is used for irrigation, it is necessary to enhance the monitoring of the water quality of this irrigation water, in order to determine the composition and concentration of pollutants present in it as well as their dynamics. This helps to prevent pollutants that are difficult to degrade and leave high residues from entering the soil through the water, thereby avoiding soil contamination. 　　3) Rational use of chemical fertilizers and pesticides
The use of highly toxic and persistent pesticides should be prohibited or restricted. Efforts should be made to develop highly effective, low-toxicity, and low-residue pesticides, as well as biological control measures. For example, it is prohibited to use pesticides that, although have low residues, possess high acute toxicity. The use of organochlorine pesticides with high residue levels is prohibited. Based on the characteristics of pesticides, they should be applied appropriately, and safe intervals for their use should be established. Integrated pest management measures should be adopted to both prevent the threats posed by pests and diseases to crops and to minimize the harm caused by pesticides to the environment and human health. 　　4) Increase soil capacity and enhance its purification ability
Increasing the content of soil organic matter and mixing sand with clay to improve soil quality helps to increase and diversify the types and quantities of soil colloids. This, in turn, enhances the soil’s ability and capacity to adsorb harmful substances, thereby reducing the activity of pollutants in the soil. Discovering, isolating, and culturing new microbial strains to enhance biodegradation is a crucial step in improving the soil’s purification capacity. 　　5) Establish a monitoring system network to regularly inspect the soil environmental quality within the jurisdiction and create systematic archival records. It is necessary to specify the soil pollutants to be prioritized for detection as well as the standard detection methods. In this regard, reference can be made to recommendations from relevant international organizations and China’s national conditions to set targets for soil environmental pollution control; investigations, research, and implementation of countermeasures should then be carried out in accordance with these priorities. 　　Measures for preventing and controlling soil pollution
1) Application of soil amendments
The main purpose of applying soil amendments is to accelerate the decomposition of organic matter and to immobilize heavy metals in the soil. For example, adding organic matter can speed up the degradation of pesticides in the soil, thereby reducing their residual amounts. 　　 The application of heavy metal absorption inhibitors (amendments) involves adding amendments such as lime, phosphates, and calcium silicate to the soil. These substances react with heavy metal pollutants to form insoluble compounds, thereby reducing the mobility of heavy metals in the soil and within plants growing in it. This method has a temporary inhibitory effect; however, if used for too long, it can lead to the accumulation of pollutants. Moreover, under changing conditions, heavy metals become soluble again. Therefore, it can only be applied in areas with relatively low levels of pollution. 　　2) Controlling the soil redox conditions
Controlling the soil’s redox conditions is also an important measure to mitigate the harmful effects of heavy metal pollution. Research shows that from the heading to the maturity stage of rice, inorganic components are largely transferred to the panicles. Flooding significantly inhibits cadmium uptake by rice, while drying promotes it. 　　Heavy metal elements can all react with hydrogen sulfide in the soil to form sulfide precipitates. Therefore, strengthening slurry management can effectively reduce the hazards of heavy metals. Conversely, for arsenic, its toxicity increases as the soil oxidation-reduction potential decreases. 　　3) Change the farming system
Altering soil environmental conditions through soil tillage can eliminate the harmful effects of certain pollutants. Conversion of dry land to paddy fields: The degradation rates of DDT and BHC in dry land are slow, leading to significant accumulation ； In paddy fields, the degradation rate of DDT accelerates; utilizing this property to implement crop rotation between wet and dry seasons is an effective measure to reduce or eliminate agricultural pollution. 　　4) Deep plowing with imported soil The removal of contaminated soil; in particular, heavy metal pollution in the soil leads to accumulation, which hinders the growth and development of crops. The fundamental solution for prevention and control is the soil removal and replacement method, which involves completely excavating the contaminated soil and replacing it with fresh soil, in order to eradicate pollutants. However, in the case of regional pollution, it is impractical to actually employ the soil replacement method. 　　Plowing the soil layer, that is, performing deep plowing to mix the upper and lower soil layers, thereby reducing the content of pollutants in the topsoil. This method involves less earthwork, but is not suitable for heavily polluted areas. 　　5) Apply agro-ecological engineering measures. Grow non-edible seeds, cash crops, or plant species on contaminated soil, thereby reducing the pathways by which pollutants enter the food chain. Or, certain specific plants, animals, and microorganisms can be utilized to rapidly absorb or degrade pollutants in the soil, thereby achieving the purpose of soil purification. 　　6) Engineering remediation
This involves using physical (mechanical) and physico-chemical principles to remediate contaminated soil. Common methods include isolation, washing, thermal treatment, and electrochemistry. It is the most thorough, stable, and fundamental measure for remediation. However, the investment is high; it is suitable for small-area areas with severe pollution. 　　In recent years, the application of technologies from other industrial fields, particularly those used in wastewater and air pollution control, to soil remediation has opened up new avenues for research in this area; examples include magnetic separation technology, cation-anion membrane exchange methods, and bioreactors. Although most of them are still in the experimental and exploratory phase, actively absorbing and applying new technologies and materials to reduce treatment costs while ensuring treatment effectiveness and enhancing the practicality of projects holds great practical significance. 　　7) Determining the permissible residue levels of pesticides
This is done by multiplying the pesticide’s “maximum acceptable daily intake” (permitted intake per kg of body weight per day; expressed as the ADI value) by a safety factor (usually set at 1/100). 　　Residue tolerance = ADI × body weight (kg) / food factor

Main characteristics of heavy metal pollution: wide scope of contamination, long duration, hidden nature of the pollution, inability to be biodegraded. It can continuously accumulate in organisms through the food chain; it may even be converted into more toxic methylated compounds. This poses a threat to certain organisms in the food chain and can ultimately accumulate in the human body, thereby harming health. Governance methods and characteristics: include engineering governance, biological governance, chemical governance, and agricultural governance methods. Engineering treatment provides thorough and stable results, but it is complex to implement, costly, and can lead to a decline in soil fertility ； Biological treatment is easy to implement, requires low investment, and causes minimal environmental damage, but its treatment effects are not ideal ； The effectiveness and cost of chemical treatment methods are moderate; however, they are prone to re-activation ； Agricultural governance methods are easy to implement and low-cost, but they have a long cycle time and modest results. In summary, depending on the characteristics of different pollutants and the requirements regarding treatment effectiveness, duration, and cost, the most suitable treatment method should be selected. The chemical stabilization method often fails to ensure long-term stability of the treatment results; however, the currently much-discussed molecular bonding remediation technology can effectively address this issue. It is expected to become a preferred treatment method that combines good treatment effectiveness, low costs, and a short treatment duration

Are there really no good measures to prevent and control heavy metal pollution? Use it sparingly, very sparingly; preferably not at all.

The sources of heavy metals are very diverse; traditionally, they can be divided into industrial and agricultural sources. With the accelerating pace of urbanization in China, some new sources of pollution unique to cities have emerged, differing from those in the past. Sources of heavy metals are as follows: Industrial sources: Industrial energy primarily comes from coal and petroleum; these are the main sources of heavy metal pollution in the environment, including mercury, lead, cadmium, chromium, and arsenic. A large amount of heavy metal pollution is generated during industrial processes such as mining, mineral processing, smelting, forging, processing, and transportation. Discharged wastewater, waste residues, etc. directly enter water bodies and soil; heavy metals contained in exhaust gases also settle into the environment, including the soil. As a result, the concentration of heavy metals in the environment far exceeds permissible limits. Agricultural sources: In agricultural production, the improper use of wastewater for irrigation, pesticides, and low-quality fertilizers is a major pathway for heavy metal pollution. Take phosphate fertilizers as an example. The phosphate rock used in their production has a complex composition and contains relatively high amounts of heavy metals such as zinc, chromium, nickel, copper, cadmium, and lead. Therefore, if not used properly, the heavy metal impurities in low-quality fertilizers can directly lead to soil pollution. Urban sources: Cities are increasingly becoming one of the major sources of heavy metal pollution. The pollution processes mainly include the disposal of sludge generated during wastewater treatment, leakage of landfill leachate, the use of leaded gasoline, and automobile traffic. The sludge generated by wastewater treatment plants contains large amounts of heavy metals; if discharged or used for irrigation without proper treatment, it can cause secondary pollution to the soil environment. The heavy metals in the fly ash generated during the incineration of municipal waste, as well as in the leachate produced during waste storage and landfilling, also often exceed permissible limits significantly. The combustion of leaded gasoline is a major source of urban lead pollution; zinc used in additives for automobile tires also contributes to zinc pollution in urban soils. Environmental accident pollution: In recent years, there has been a sharp increase in sudden environmental pollution incidents, among which cases of heavy metal pollution account for a large proportion. Sudden environmental events can cause heavy metals to enter the environment at high concentrations in a short period of time, resulting in severe pollution. Chemically, metals are classified into heavy metals and light metals based on their density. Metals with a density greater than 5 g/cm³ are generally referred to as heavy metals; examples include gold, silver, copper, lead, zinc, nickel, cobalt, chromium, mercury, cadmium, and about 45 other types in total. Among them, there are 5 types that are most harmful to the human body: such as lead, mercury, chromium, arsenic, and cadmium. These heavy metals cannot be broken down in water; they combine with other toxins in water to form organic compounds that are even more toxic. Other substances harmful to the human body include: aluminum, cobalt, vanadium, antimony, manganese, tin, thallium, etc. Common harms of heavy metals to the human body include: Lead: damages brain cells, causes cancer and mutations, etc. Mercury: After ingestion, it settles directly in the liver; it causes significant damage to the brain, nerves, and vision. In natural water, a concentration of 0.01 milligrams per liter can cause severe poisoning. Chromium: Can cause numbness in the limbs and mental abnormalities. Arsenic: It can cause skin pigmentation and lead to abnormal keratinization. Cadmium: Causes high blood pressure and leads to cardiovascular and cerebrovascular diseases ； It destroys bone calcium, leading to kidney dysfunction. Aluminum: Prolonged accumulation can cause intellectual disability in children ； It causes memory loss in middle-aged people ； It causes dementia and other conditions in the elderly. Cobalt: Can cause radioactive damage to the skin. Vanadium: Damages the heart and lungs, leading to abnormal cholesterol metabolism. Antimony: Along with arsenic, it can turn silver jewelry a brick red color and cause radioactive damage to the skin. Selenium: Excessive amounts can cause ataxia in humans. Thallium: Can cause polyneuritis in humans. Manganese: Excessive amounts can cause hyperthyroidism. Tin: Along with lead, it was an important component of ancient poisons; once ingested, it would solidify into lumps that caused death by suffocation.

On the Current Theoretical Status and Prevention Measures for Heavy Metal Pollution as a Form of Environmental Pollution 【Abstract】 With the rapid economic development in China and the increasing population, the area of polluted soil is gradually expanding. According to incomplete statistics, from 1980 to 1998, the area of polluted soil increased to account for about 1/5 of the total arable land area. It is worth noting that the pollution caused by the discharge of \"three wastes\" from industrial enterprises in rural areas of our country poses a threat to the soil environment; in regions where such industry is well-developed, local soil pollution is quite severe. According to investigations, among the soil pollution issues in our country, the most severe hazards are caused by the heavy metals copper and mercury; in some areas, residents have exhibited symptoms of \"bone pain syndrome\". Furthermore, the agricultural use of sludge in urban wastewater, as well as the storage and disposal of municipal waste, industrial slag, and toxic waste; the excessive use of chemical fertilizers, pesticides, and agricultural plastic films; and the contamination of soil along roadsides by polycyclic aromatic hydrocarbons and lead, all pose a serious threat to the soil environment. Therefore, it is a complex and arduous task to conduct in-depth research on the migration, transformation, degradation, and retention behaviors and patterns of various environmental pollutants in soil environments, to seek economically viable and effective comprehensive control measures, to strengthen legislation and management, and to protect soil resources. 【Keywords】 Soil environmental pollution; Heavy metal pollution and its remediation and prevention. With the rapid economic development in China and the increasing population, the area of polluted soil is gradually expanding. According to incomplete statistics, from 1980 to 1998, the area of polluted soil across the country increased year by year, reaching about 1/5 of the total arable land area by 1998. It is worth noting the pollution problem caused to the soil environment by the emissions of ’three wastes’ from the industrial enterprises in rural areas of our country. In areas with developed township industries, local soil environmental pollution is extremely severe. According to investigations, among the soil pollution issues in our country, the most severe hazards are caused by the heavy metals copper and mercury; in some areas, residents have exhibited symptoms of \"bone pain syndrome\". Furthermore, the agricultural use of sludge in urban wastewater, as well as the storage and disposal of municipal waste, industrial slag, and toxic waste; the extensive use of fertilizers, pesticides, and agricultural plastic films; and the contamination of soil along roadsides by polycyclic aromatic hydrocarbons and lead, all pose a serious threat to the soil environment. Therefore, it is a complex and arduous task to conduct in-depth research on the migration, transformation, degradation, and retention behaviors and patterns of various environmental pollutants in soil environments, to seek economically viable and effective comprehensive control measures, to strengthen legislation and management, and to protect soil resources. The soil environment is one of the important components of the Earth’s environmental system, holding a special spatial position; its upper surface is in contact with the atmosphere and biosphere, while its lower surface is in contact with the lithosphere and groundwater. Therefore, the soil environment becomes the area where various physical, chemical, and biological processes, interfacial reactions, as well as processes of substance and energy exchange and migration occur most complexly and frequently. It is also a sub-environmental system that is highly sensitive to and rich in information regarding environmental changes, playing an important role in stabilizing and buffering the entire surface system. It is precisely due to the complexity of the soil environment that soil pollution is not as easy to detect as air pollution and water pollution. Sometimes, soil pollution is only identified when the pollutants in the soil enter animals and humans through the food chain and cause harm to them; by that time, the soil pollution is often already quite severe. As early as 1877, the Ashio Copper Mine pollution incident occurred in Tochigi Prefecture, Japan. The copper-containing wastewater discharged from the mine contaminated the nearby farmlands, damaging thousands of hectares of soil and crops and resulting in severe yield losses. This is a typical case of early soil environmental pollution. The soil environment also plays an important role in purification, stabilization, and buffering. The soil environment possesses strong purification capabilities and a large environmental capacity; humans have long used it as a natural site for treating animal manure, organic waste, and garbage. Modern land treatment systems such as wastewater irrigation and the application of sludge in agriculture further make use of the environmental functions and capacity of the soil in a deliberate and purposeful manner. However, the capacity of the soil environment to purify itself, stabilize itself, and act as a buffer is limited. If the amount and rate at which pollutants are introduced into the soil environment exceed its self-purification capacity and carrying capacity, the soil environment will be severely damaged ； Once the soil environment becomes contaminated, not only is it difficult and time-consuming to remediate the soil itself, but the pollutants also migrate through various pathways into the atmosphere, water, and biological environments, resulting in “secondary pollution”. Since the biogeochemical cycling of various elements in soil environments includes not only the cycling of nutrient elements but also that of pollutants such as heavy metals and chemical pesticides, the biogeochemical cycling of elements in soil environments has both positive and negative impacts on the entire Earth’s ecosystem and humanity. The biogeochemical cycling of heavy metal elements and chemical pesticides in soil has always been a key area of research in soil environmental science. As an important buffer zone in the terrestrial environmental system, soil can absorb and retain pollutants from the atmosphere and hydrosphere. However, if the amount of pollutants that enter the soil exceeds its self-purification capacity, the pollution that results from long-term accumulation can be very severe. For example, heavy metals generally do not leach away with water in soil, nor can they be broken down by soil microorganisms; as a result, they tend to accumulate in the soil environment. Some heavy metal elements can even transform into more toxic forms in the soil, before entering plants, animals, and ultimately humans through pathways such as the food chain. In the early stages of pollutant accumulation in the soil environment, there are usually no obvious signs, making it difficult for people to detect and become alert. Once the pollution reaches a level that poses a threat, it becomes very hard to eliminate. The soil heavy metal pollution that occurred in Japan during the 1950s and 1960s still lacks an effective solution to date. Pesticides in the soil environment can cause air pollution by volatilizing, diffusing, and migrating into the atmosphere, or cause water pollution by migrating and diffusing with water (including leaching and soil erosion), thereby leading to the spread of chemical pesticides worldwide. Residues of the long-banned DDT pesticide have even been found in the ice sheets of the Arctic Circle, indicating that pollutants transported through soil biogeochemical cycles have already spread to every corner of the globe. Harmful substances such as these heavy metals and chemical pesticides can easily accumulate in organisms through the food chain, causing harm to animals, plants, and humans. It is thus evident that we should fully recognize the dual nature of the biogeochemical cycles in the soil environment regarding their impact on humans, make use of their beneficial aspects, and prevent their adverse effects. Leverage the environmental capacity and self-purification ability of soil to mitigate and address some of the current pollution problems, while also being aware of the potential hazards of soil pollution. In the prevention and control of environmental pollution, only by carrying out comprehensive management of the entire surface environment system, including the soil environment, can a sustainable approach be adopted to address various environmental problems. The identification of soil pollution pollutants and the analysis of their sources are important bases for implementing soil pollution control. Through the analysis of soil environmental pollutants and pollution sources, it is possible to determine the type of soil pollution, its degree of contamination, the incidents of pollution, and the main pollutants involved; this serves as the foundation for the scientific management and control of soil pollution. Based on the properties of soil environmental pollutants, they can be classified into organic pollutants, inorganic pollutants, radioactive pollutants, and pathogenic microorganism pollutants. The main inorganic pollutants in the soil environment fall into three categories: heavy metal pollutants, acid-base pollutants, and chemical fertilizers. Among them, heavy metal pollutants are the most difficult to manage in soil, entering it primarily through processes such as irrigation with wastewater from farmlands and the deposition of exhaust gases from heavy metal smelting plants. Heavy metals have stable forms, do not decompose, and tend to accumulate; addressing them is costly and causes damage to the soil itself. Cadmium, mercury, lead, copper, etc. are several common pollutants. Soil environmental pollution sources are mainly caused by human activities. Based on the nature of these sources, they can be classified into industrial pollution sources, agricultural pollution sources, biological pollution sources, traffic pollution sources, radioactive pollution sources, and domestic pollution sources. Due to the complexity of pollutants, the diversity of pollution sources, the special structure of soil, the complex mechanisms of soil pollution, the variety of occurrence types, as well as the prominent characteristics exhibited, there are multiple types of soil pollution. Based on the types of pollutants, soil environmental pollution can be classified into organic pollution, heavy metal pollution, radioactive element pollution, and pathogenic microorganism pollution. Heavy metals generally enter the soil through precipitation in water bodies and the atmosphere. Industrial waste is an important source of heavy metals, which mainly include mercury, cadmium, copper, zinc, chromium, nickel, cobalt, and others. Heavy metals cannot be broken down by microorganisms, and they can accumulate in living organisms; therefore, once soil is contaminated with heavy metals, both its natural purification process and artificial remediation become very difficult. Furthermore, heavy metals can be bioaccumulated, thus posing a significant potential hazard to humans. Heavy metal pollution has now become a hot topic in soil pollution research. Based on the sources of pollution, soil environmental pollution can be classified into water pollution type, air pollution type, agricultural pollution type, and solid waste pollution type. Solid waste generally refers to solid and muddy substances discarded in production and daily life, including industrial waste residues, municipal garbage, and solid particles separated from wastewater and exhaust gases. Pollutants in the large amounts of solid waste piled on the soil surface can leach into the soil with rainwater, causing contamination. Solid waste contains heavy metals, toxic chemicals, oils, bacteria, etc. The characteristic of solid waste pollution is point-source pollution in which contaminants spread radially from the site where they are piled up or landfilled. Soil environmental pollution has the following two harms: (1) The harm of soil pollution to agriculture. Soil is the most important means of production in agriculture and a source of food for humans. Farmland pollution directly affects plant growth as well as human health and quality of life; therefore, it has always been a type of soil pollution that receives considerable attention. When pollutant concentrations reach a certain level, crops suffer damage, resulting in significant yield reductions or even death of the crops. For example, heavy metals such as copper are absorbed by plants and accumulate in their roots, with little transfer to the above-ground parts of the plant. This results in high concentrations of heavy metals in the plant roots, causing the plant to be poisoned, wither, or even die before it has reached maturity. If the pollutants are still within acceptable levels for the plants at the time of harvest, the plants can still mature, but their cell tissues or certain organs have already been poisoned. Consuming such crops can directly cause poisoning in the human body. (II) Soil environmental pollution and human health: Once soil environmental pollution occurs, it has a significant impact on human health. On the one hand, the decomposition of organic pollutants in the soil can produce extremely unpleasant-smelling gases, and the degradation of certain organic substances can yield toxic gases that are harmful to animals, plants, and humans ； On the other hand, heavy metals and certain organic substances in the soil can also accumulate in plants, affecting the health of animals and humans through the food chain. Metal elements are widely present in nature, and metals are particularly important for the survival of organisms and humans. For example, iron is an essential element for synthesizing hemoglobin; too low a concentration of iron in the blood can lead to iron-deficiency anemia. Zinc can enhance appetite and promote growth and development; it has important physiological functions, including enhancing the regenerative capacity of damaged tissues and accelerating tissue healing. A zinc deficiency in the human body leads to reduced zinc acid activity, resulting in malnutrition, loss of smell and taste, decreased vision, anemia, enlargement of the liver and spleen, underdeveloped reproductive organs, and it can also cause cardiovascular diseases. Metal elements are among the first elements utilized by human ancestors; however, due to the limited scale of ancient metallurgy, they rarely caused widespread heavy metal pollution. With the development of human mining and smelting technologies as well as modern industry, heavy metal pollution has become one of the severe and extremely difficult-to-address types of pollution. Among the “Eight Major Public Health Hazards” that occurred around the 1950s, Minamata disease in Kyushu, Japan, itai-itai disease in Toyama, and respiratory diseases in Yotsuya were all caused by heavy metal pollution. In the soil environment, sources of heavy metal pollution mainly come from industries such as mining, industry, agriculture, and transportation: (1) Mining sources of pollution: During the extraction of heavy metal ores, if the tailings are not treated or are treated inadequately, it can lead to heavy metal contamination of the soil. Additionally, wastewater used in ore washing, if discharged without treatment, can also cause heavy metal contamination in the soil. Moreover, dust generated during mining can settle in the atmosphere and contribute to heavy metal contamination in the soil. The characteristic of mining pollution sources is that they are distributed starting from the mining site, in the direction of ore transportation, downstream along water flow, and downwind, resulting in a large polluted area. (II) Industrial pollution sources: Generally speaking, various industries in the manufacturing sector emit heavy metal waste; among them, the metallurgical industry, electroplating industry, processing industry, chemical industry, and other industries that make extensive use of metals as raw materials or production inputs are those with relatively severe heavy metal pollution. The main characteristics of industrial pollution sources are high pollution emission concentrations, complex compositions, and difficulty in treatment. The pollutants emitted by most industrial pollution sources can directly affect the local residents, and improper handling of the \"three wastes\" can lead to pollution incidents in the soil environment. (III) Agricultural pollution sources: Heavy metal pollution from agricultural sources mainly comes from pesticides and fertilizers, as well as irrigation with wastewater. Pesticides and fertilizers contain small amounts of heavy metals, which enter the soil environment in agricultural fields as a result of their application ； Irrigating farmland with wastewater containing heavy metals can also lead to soil contamination by heavy metals. Pollutants harm crop growth and affect yields. Crops enriched with heavy metals, when they enter the food chain, can affect human health. The main characteristic of agricultural pollution sources is that the primary soil environment affected by pollution is farmland, and the soil surrounding the farmland is also impacted, which has a direct effect on human health. (IV) Traffic pollution sources: Traffic pollution sources refer to the heavy metals contained in the exhaust gases emitted during transportation, especially road transport, which lead to contamination of the surrounding soil environment by these heavy metals. The gasoline used in cars generally contains the heavy metal lead, and as it is emitted through exhaust gases, it causes lead pollution on both sides of roads. The characteristics of traffic pollution are: it is distributed along both sides of roads, and the main pollutant is lead. In soil environments, the characteristics of heavy metal pollution can be divided into two parts: one is the inherent properties of the heavy metals themselves in the soil environment ； Second is the difference from the characteristics in media such as water bodies and the atmosphere: (1) The morphological changes are more complex ； (II) The toxicity of the organic form is greater than that of the inorganic form ； (III) Toxicity is related to the valence state and the type of compound ； (IV) Diverse forms of migration and transformation in the environment ； (V) The concentration at which biological toxic effects occur is relatively low ； (VI) Accumulation and enrichment in organisms ； (VII) Not easily detectable in the soil environment ； (VIII) Does not degrade or get eliminated in the environment ； (IX) Chronic toxic process in humans ； (10) The distribution of soil environments is regional. Common types of harmful heavy metal pollution include mercury pollution, cadmium pollution, lead pollution, chromium pollution, etc. Heavy metals are a type of pollutant that is extremely harmful to the ecological environment. Heavy metals remain in the soil for a long time; they are difficult to degrade by plants or microorganisms. Moreover, when heavy metals accumulate in excessive amounts in the edible parts of crops, they can easily be transferred to humans or animals through the food chain, posing serious threats to human health. How to remove heavy metal pollutants from the soil environment has become an international challenge. Currently, the main technologies for heavy metal pollution remediation include physical, chemical, and biological treatment methods; however, most of these methods are still in the experimental and simulation stage. The physical remediation methods suitable for heavy metal pollution mainly include: soil amendment, washing, electrokinetic remediation, thermal treatment, etc. These methods are suitable for treating soils with a small affected area and low levels of contamination. However, for soils with extensive and severe contamination, they require substantial human and financial resources, and can easily lead to soil structure damage, decreased soil fertility, and secondary pollution. The main chemical remediation methods suitable for heavy metal pollution include: redox potential method, chemical reagent method, solidification/stabilization method, etc. These methods have moderate costs and are suitable for the remediation of moderately polluted areas; however, if not properly implemented, they can cause secondary pollution. Phytoremediation technology is a newly developed remediation approach that has seen rapid growth in recent years. It offers advantages such as being cost-effective, green, and environmentally friendly; it is often referred to as green remediation. Phytoremediation generally refers to the technique of using heavy metal hyperaccumulating plants to absorb heavy metals from contaminated soil. There are few reports on microbial remediation of soil contaminated by heavy metals, and it has only gained widespread attention in recent years. Microbial remediation of heavy metal-contaminated soils mainly involves biological adsorption and biological redox methods. The former is a treatment method in which heavy metals are adsorbed by organisms, while the latter utilizes microorganisms to alter the redox state of heavy metal ions, thereby reducing their levels in the environment and water bodies. 【References】 Chen Jian, Environmental Biotechnology, China Light Industry Press. Dai Shugui, Environmental Chemistry, Higher Education Press. Huang Guoqiang, Li Ling, Li Xingang, In-situ Remediation of Soil Pollution, Environmental Science Trends. Liu Peitong, Chen Yiqiu, Introduction to Environmental Science, Water Resources and Electric Power Press. Wang Hongqi, Liu Xinhui, Li Guoxue, Soil Environmental Science, Higher Education Press. Zhang Zhongxian, Environment and Green Chemistry, Tsinghua University Press

Heavy metal pollution refers to environmental pollution caused by heavy metals or their compounds. It is mainly caused by human factors such as mining, exhaust gas emissions, wastewater irrigation, and the use of heavy metal products. Human activities have led to an increase in heavy metal concentrations in the environment, exceeding normal levels and resulting in a deterioration of environmental quality. The main source of heavy metal pollution is industrial pollution, followed by traffic pollution and household waste pollution. Industrial pollution is mostly released into the environment through waste residues, wastewater, and exhaust gases; it accumulates in humans, animals, and plants, thereby causing significant harm to the environment and human health. The control of industrial pollution can be achieved through various technical methods and management measures to reduce its levels, ultimately meeting the established standards for pollutant discharge and preventing heavy metal contamination in tea ； Traffic pollution is mainly caused by vehicle exhaust emissions; **a range of control measures have been established, such as using ethanol-blended gasoline and installing exhaust purification systems in vehicles** ； Domestic pollution mainly stems from household waste, such as used batteries, broken light bulbs, unused cosmetics, and glazed dishes. As for heavy metal pollution, we can more or less reduce it by controlling its sources. 　　 Experts analyze that the relatively backward processes, equipment, and technological research and development in China’s plastic manufacturing enterprises are the main causes of severe pollution. Poor management, local protectionism, and low environmental awareness among people further exacerbate this pollution, making it urgent to strengthen pollution control measures. Manufacturing enterprises should look to the future, advocate environmental protection, and use eco-friendly additives in order to ensure the healthy and sustainable development of the PVC industry. Controlling and eliminating sources of soil pollution are the fundamental measures to prevent pollution. The soil’s ability to purify pollutants is equivalent to a certain capacity for treatment. Control soil pollution sources, that is, control the amount and rate of pollutants entering the soil, so as to prevent soil pollution through its natural purification processes. 1) Control and eliminate the emission of industrial ’three wastes’. 2) Strengthen the monitoring and management of soil areas contaminated by pollutants. 3) Apply fertilizers and pesticides in a rational manner. 4) Increase soil capacity and enhance its purification ability. 5) Establish a monitoring system network to regularly inspect the soil environmental quality in the relevant areas, and create systematic records. Priority should be given to identifying the soil pollutants that need to be monitored as well as the standard methods for testing them. In this regard, objectives for addressing soil environmental pollution can be formulated by referring to the recommendations of relevant international organizations and China’s national conditions, with investigations, research, and implementation of countermeasures carried out in order of priority.