Why can recycling scrap metal reduce environmental pollution?
Heavy metal pollution is different from the pollution of other organic compounds. Many organic compounds can be purified through physical, chemical, or biological processes in nature to reduce or eliminate their harmful effects. However, heavy metals have enrichment properties and are difficult to degrade in the environment. At present, due to the mining, smelting, and processing of heavy metals in China, many heavy metals such as lead, mercury, cadmium, cobalt, etc. have entered the atmosphere, water, and soil, causing serious environmental pollution. Even if the concentration of heavy metals discharged with wastewater is small, they can accumulate in algae and sediment, be adsorbed on the surface of fish and shellfish, produce food chain concentration, and cause pollution. Whether metals are beneficial or harmful in water depends not only on the type and physicochemical properties of the metals, but also on their concentration, valence state, and form. Even if the concentration of beneficial metal elements exceeds a certain value, they can have severe toxicity, causing poisoning and even death of animals and plants. Metal organic compounds (such as organic mercury, organic lead, organic arsenic, organic tin, etc.) are much more toxic than corresponding metal inorganic compounds; Soluble metals are more toxic than particulate metals; Hexavalent chromium is more toxic than trivalent chromium, and so on.
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