Heavy metals discharged from water, even if the concentration is very small, can accumulate in algae and sediments and be adsorbed by fish and shellfish, resulting in food chain concentration, thus causing public hazards. Whether the metal in water is beneficial or harmful depends not only on the kind and physical and chemical properties of the metal, but also on the concentration of the metal and its valence and form. Even if the concentration of beneficial metal elements exceeds a certain value, it will produce serious toxicity, poisoning animals and plants, and even death. Metal organic compounds (such as organic mercury, organic lead, organic arsenic, organic tin, etc.). ) is much more toxic than the corresponding metal-inorganic compounds; Soluble metals are more toxic than granular metals; Hexavalent chromium is more toxic than trivalent chromium and so on. Heavy metals can interact strongly with protein and various enzymes in human body, making them inactive, and may also be enriched in some organs of human body. If it exceeds the tolerance limit of human body, it will cause acute poisoning, subacute poisoning and chronic poisoning. , will cause great harm to the human body. For example, Minamata disease (mercury pollution) and osteopathy (cadmium pollution) in Japan are all public hazards. Heavy metals are widely distributed in the atmosphere, water, soil and organisms, and sediments are often the repository and final destination of heavy metals. When the environment changes, the forms of heavy metals in sediments will be transformed and released to cause pollution. Heavy metals are not biodegradable, but they are bioaccumulative and can directly threaten higher organisms, including humans. Experts pointed out that the pollution of heavy metals to soil is irreversible, and the polluted soil has no treatment value, which can only be avoided by adjusting the planting varieties. Therefore, the problem of heavy metal pollution in sediments has attracted more and more attention.
Heavy metal pollution mainly comes from industrial pollution, followed by traffic pollution and domestic garbage pollution. Most industrial pollution is discharged into the environment through waste residue, waste water and waste gas, which is enriched in people, animals and plants, thus causing great harm to the environment and human health. The treatment of industrial pollution can reduce its pollution through some technical methods and management measures, and finally achieve national pollutant discharge to prevent heavy metal pollution of tea.
Put the standard; Traffic pollution is mainly the emission of automobile exhaust, and the state has formulated a series of management measures, such as: using ethanol gasoline and installing automobile exhaust purifier; Domestic pollution is mainly caused by some domestic garbage, such as waste batteries, broken lamps, unused cosmetics, glazed plates and so on. As long as the heavy metal pollution is controlled from the source, it can be reduced more or less. Experts pointed out that the backward research and development of technology, equipment and technology of plastic production enterprises in China is the main cause of serious pollution, and poor management, local protection and people's weak awareness of environmental protection have aggravated the pollution, which needs to be strengthened urgently. Production enterprises should look to the future, advocate environmental protection and use environmental additives to make the PVC industry develop healthily and long-term.