In recent years, the problem of soil pollution in the world has become increasingly prominent, especially in developing countries, posing a serious threat to the ecological environment, food safety and human health. Among them, soil pollution caused by heavy metal pollutants such as mercury, cadmium, lead, chromium and arsenic is particularly prominent. Analyze the main technology and development direction of soil remediation in foreign contaminated sites, look for the technical gap between China and Europe and the United States, and provide ideas and direction for the development of soil remediation technology in contaminated sites in China. 1, foreign soil repair technology research and development process The remediation industry of contaminated sites in developed countries in Europe and the United States accounts for more than 50% of the total environmental protection industry. The research and development of soil remediation technology in Europe and the United States are divided into three stages: (1) Before the 1980s, the soil remediation method was physical and chemical remediation. The remediation technologies mainly used excavation and landfill, soil-based method, solidification / stabilization, soil gas Extraction, chemical extraction; (2) From the 1980s to the beginning of the 21st century, soil treatment methods were physical, chemical and bioremediation. Remediation techniques mainly used IMC (isolation, maintenance and control), leaching, chemical extraction and chemical redox , Glass curing and thermal desorption. (3) Since the 21st century, soil treatment has been carried out in physical, chemical and biological ways. However, extensive attention has been paid to efficient and low-cost methods of restoration, with emphasis on phytoremediation and natural transfer and attenuation. 2, the status of the application of soil repair technology abroad There are about 294,000 contaminated sites in the United States. In 2007 alone, the U.S. Superfund project spent $ 380 million on soil remediation projects. It is estimated that the completion of the restoration of all polluted soils in the United States will require 208.9 billion yuan investment, with most of the repairs taking 30-35 years. The United States conducted extensive soil remediation projects after the 1980s. The soil remediation technology implemented by the US Superfund Fund Program has become an important window for all countries in the world to understand the latest changes in soil remediation technologies. Figure 1 shows the statistical results of soil remediation technology in the United States, where the light-colored part represents the in-situ repair technique and the dark part represents the ectopic repair technique. It is estimated that in Europe about 21.1 billion euros each year for the repair and management of polluted soil. Figure 2 shows the current status of different soil remediation technologies in some European countries and throughout Europe from 1978 to 2007. As can be seen from Figure 2, all the countries in Europe have significantly different soil remediation technologies according to their national conditions. In situ and ectopic thermal desorption, in situ and ectopic biological treatment, in situ and ectopic physicochemical treatment of contaminated sites accounted for 69.17% of all the statistical projects in Europe, including in situ thermal desorption, in situ biology Treatment and in situ physicochemical repair technology accounted for 35%, ectopic thermal desorption, ectopic bioprocessing and ectopic physicochemical repair technology accounted for 34.17%, both the proportion of the same, the other repair technology accounted for 30.83%. In practical engineering, the biological treatment technology is the most widely used, reaching 35%, of which 18.33% were in situ biological treatment and 16.67% in biological treatment. In addition, projects that treat contaminated soil as waste instead of renewable resources (including excavation techniques, pollution control, etc.) still account for a large proportion in Europe, reaching 37%. 3, soil repair technology trends Four major development directions: (1) In the decision-making direction, from the control based on the total amount of pollutants to risk assessment based on pollution; (2) technically, from a single repair technology to multi-technology joint repair technology in situ, Integrated and integrated engineering repair technology; (3) in equipment, from the ectopic repair of fixed equipment to mobile equipment in situ repair; (4) in the application, the development of a variety of pollutants compound or mixed contaminated soil Of the combined repair technology; from a single site to large venues venue; from single repair technology to the simultaneous monitoring of the atmosphere, water, multi-technology and equipment coordinated ground soil - groundwater remediation. Six major directions of development: (1) green, environmentally friendly bioremediation technology; (2) from a single integrated / hybrid repair techniques; (3) from ectopic to in situ repair techniques; (4) based on environmental functions (5) equipment-based rapid site restoration technology; (6) soil remediation decision support system and post-repair assessment techniques. 4, China and Europe and the United States gap Compared with the developed countries, China lags behind more than 20 years, mainly in the following six aspects: (1) The technology is single and lack of systems, especially in-situ, rapid and applicable to the physical and chemical technologies of site soil (including groundwater); (2) Lack of technology and equipment, lack of industry; (3) the lack of technical standards, lack of rules and regulations, technology is difficult to apply; (4) few cases of engineering repair, lack of market; (5) lack of experience in their own practice, (6) The key is less investment, the lack of practical technology. Remediation of contaminated sites in China contains a huge market demand, but for the contaminated site soil remediation technology, engineering application and equipment development started late. We should take into consideration the mature repair technology and advanced equipment from abroad, and consider comprehensively the selection and development direction of restoration technologies from the aspects of the pollution characteristics of our country, the national economic and social development, the level of national scientific research and the technical reserves at the present stage. Chlorinated Polyethylene(CPE) 1. CPE is a kind of saturated rubber, which has excellent heat-resistant oxygen aging, ozone aging, acid and alkali resistance, and chemical resistance.
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