Bioremediation refers to the process of using biological metabolic activities to reduce or change the concentration of heavy metals in the soil so that the contaminated soil environment can partially or completely return to the original state. Rehabilitation measures include phytoremediation, microbial repair and animal repair. Because of its advantages of good effect, low investment, low cost, easy management and operation, no secondary pollution and so on, it attracts more and more people's attention and becomes a hot spot in the research and engineering application of remediation of contaminated soil. 1, plant restoration measures Phytoremediation is based on the theory of plant tolerance and over-accumulation of certain or certain chemical elements. Some heavy metal-contaminated areas exist for plants that are resistant to heavy metals that exclusion or local enrichment of heavy metals to Plant root cell wall sediment and "binding" its transmembrane absorption, or with some proteins, organic acids combined to produce non-biological forms of detoxification, thereby increasing the tolerance of heavy metal injury. The use of plants and their coexisting microbial systems to remove pollutants from the environment is a new technology for environmental applications. The key to plant control measures is to find suitable hyperaccumulation or heavy metal tolerant plants. Hyperaccumulators absorb large amounts of heavy metals, but phytoremediation has some limitations. For example, hyperaccumulator usually has low biomass, slow growth and no significant effect. 2, microbial repair measures Microbial treatment is the use of some microorganisms in the soil of heavy metals with absorption, precipitation, oxidation and reduction and other effects, thereby reducing the toxicity of heavy metals in the soil. Prokaryotes (bacteria, actinomycetes) are more sensitive to heavy metals than eukaryotes (fungi) and use this principle to grow mercury-enriched bacteria in the soil. After collecting these bacteria, the bacteria are contaminated with mercury by evaporation and activated carbon adsorption Soil. At present, the use of genetic, genetic engineering and other biotechnologies to cultivate microorganisms that have the ability to detoxify heavy metals and applied to pollution control are one of the more active fields in the study of heavy metal pollution in soils. Soil microbial remediation of heavy metals mainly include two aspects: the biological adsorption and biological oxidation - reduction. Biosorption is the adsorption of heavy metals by organisms, such as cyanobacteria, sulfate-reducing bacteria and some algae to produce a large number of cationic groups with extracellular polymers such as polysaccharides, glycoproteins and other complexes with heavy metals; and biological oxidation It is the action of microorganisms to oxidize, reduce, methylate and demethylate heavy metal ions and reduce the heavy metal content in the soil environment. 3, lower animal repair measures Some of the lower animals in the soil (such as earthworms) can absorb heavy metals in the soil, thus reducing the content of heavy metals in the contaminated soil to a certain extent. Some scientists in South Korea used the earthworm toxicology test to repair the tailings of three abandoned arsenic and heavy metal mines. The study shows that earthworms have a good enrichment effect on zinc and cadmium. Thus, in the heavy metal contaminated soil stocking earthworms, to be enriched in heavy metals, the use of electric shock, water and other methods drive out of earthworms concentrated treatment of heavy metal contaminated soils have a certain degree of control effect. At present, the main measure of soil heavy metal pollution control is "prevention, prevention and treatment combined." For non-contaminated soil to prevent the main cut off the source of pollution and improve soil environmental capacity; for contaminated soil is mainly to transform and control to eliminate pollution. The transfer and transformation of soil heavy metal pollutants is very complicated and the treatment is extremely difficult. Therefore, we must pay great attention to human beings to prevent heavy metal pollution of soil.
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liquids and slurries whilst submerged in sumps or pits.
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