According to the Report of the National General Survey of Soil Contamination released in China in 2014, the overall situation of the soil environment in China is not optimistic, and the soil environment problems in industrial and mining wasteland are prominent; in terms of the contamination type, the most common type is the inorganic type, and among the inorganic pollutants, the most common pollutants are eight types of heavy metal elements such as cadmium, mercury, arsenic, copper, lead, chromium, zinc and nickel. Studies have shown that the process of soil contamination by toxic minerals not only leads to decline in soil fertility, crop yield and quality, but also easily causes groundwater pollution and accumulates in plants, animals and humans through the food chain. Therefore, restoration and treatment of compound contaminated soil caused by various heavy metals or organic and inorganic mixed pollutants has always been a hot and difficult point in research at home and abroad.
Soil barrier landfill restoration technology is a common technical means for the treatment of contaminated sites and is widely used, and the technical principle thereof is to block the migration and diffusion of pollutants in the soil by laying a barrier layer, so that the contaminated soil is isolated from the surrounding environment and achieve the purpose of treatment of the contaminated land. The in situ soil barrier covering system generally consists of a soil blocking system, a covering system, a monitoring system, etc. The soil barrier system is mainly composed of an HDPE membrane, a mud wall and other anti-penetration barrier materials, and a barrier layer is built around the contaminated area to limit the contaminated area within a specific range; for the soil covering system, the clay layer and the geomembrane usually constitute one or more isolation layers; the monitoring system mainly consists of upstream and downstream monitoring wells of the barrier area.
With respect to the soil barrier landfill technology currently used in China, the barrier treatment of contaminated sites is close to the pollution control level of China's hazardous waste landfills, and the system to be built during the restoration process is complicated. When the treatment area with heavy metal contaminated soil is larger and the amount of treatment work increases correspondingly, it directly leads to high construction cost and low cost-effectiveness for the restoration work. For example, the cost of restoration in the situ soil barrier covering technology is generally 500 to 800 RMB/m2, that is, 33.3 to 533,000 RMB/mu, and the restoration cost is high. Therefore, it is necessary to find a kind of isolation and restoration technology that is relatively low in price and can effectively isolate compound contaminated soil caused by pollutants mixed by a plurality of heavy metals or organic matters and inorganic matters, so that the technology can be widely promoted.