Governing polluted farmland, land remediation is not lacking

The land remediation mode of polluted farmland consists of two parts: the screening of pollution remediation technology and the integration of remediation and remediation technologies. According to the survey of farmland soil pollution sources and land environmental quality assessment results, the technical content of farmland pollution remediation projects is comprehensively determined through pollution sources, pollution levels and feasibility analysis of various remediation technologies. On this basis, considering the engineering characteristics of traditional land remediation, the compatibility analysis of land remediation and pollution remediation is carried out, and with reference to certain integration principles, the pollution remediation technology is integrated into the construction process of land remediation, forming a “contamination” and The “source control” combined pollution landfill land improvement and optimization integration technology system can improve the land utilization rate and achieve the effect of farmland pollution restoration. It should be noted that in the design of optimized integrated technology, priority should be given to the problem of pollution restoration in farmland environment. The results of investigation and evaluation of farmland environmental quality should be strictly revised to correct the traditional land improvement project to ensure the quality of farmland environment. improve. When optimizing the implementation of integrated technology, different land remediation engineering measures should be taken for different polluted areas. For clean areas, the project should focus on improving land utilization; for warning areas and lightly polluted areas, the project should focus on pollution remediation; for moderately and heavily polluted areas, focus on pollution source isolation should be The spread of pollution has spread. After the implementation of the optimized integration technology, it is necessary to ensure that the contaminated soil cannot be transferred into the non-polluted area, and the heavily polluted soil cannot be transferred into the lightly polluted area to achieve the implementation effect of the contaminated farmland land remediation. What is optimization integration technology?

Interception and control integration technology for farmland pollution sources. The most typical one is the ecological control technology of irrigation ditches, which is to integrate the restoration technology of artificial wetland treatment of farmland irrigation water pollution into the construction of irrigation and drainage projects. The technology can not only block the pollution source during the excavation dredging or ecological slope protection of the irrigation ditches, prevent the sewage from entering the farmland, and can design and construct the repairing unit suitable for treating the irrigation water pollution of the farmland by using existing or newly built irrigation and drainage engineering structures. . For example, the artificial wetland ecosystem reconstruction is carried out at the entrance of farmland irrigation water, so that the sewage passes through the water distribution area, the primary sediment purification area, the aquatic plant purification area and the water drainage area, through the metabolic activities of various organisms and the accompanying physics. , chemical and biological processes, the organic pollutants, nutrients and other pollutants in the sewage are multi-stage converted, degraded and removed, to achieve the harmless and resourceful of sewage, so as to achieve the purpose of controlling farmland pollution sources. Using the ecological control technology of irrigation ditches, the pollution control technology of farmland irrigation water is integrated into the irrigation and drainage project of land remediation, which fully adapts to the topography and natural environment resources of the project area, and guarantees agricultural water use and increases grain output. At the same time, the irrigation water of farmland was purified, the intensification and spread of pollution were controlled, and the economic, social and environmental benefits of land consolidation of contaminated farmland were further improved. However, this technology also has a large area, small hydraulic load, timely cleaning of plants in the wetland, system operation is affected by climate and poor sanitation, and should be paid attention to in future use.

Remediation integration technology for farmland soil pollution. It mainly includes: 1. Mixing and diluting method of excavating and filling earth, that is, in the process of leveling the land, lowering the height of the field, peeling off the topsoil, treating the base layer, and backfilling the plough layer, using the soil in the physical and chemical remediation technology of soil pollution, Physical restoration methods such as deep tillage and soiling are used to treat contaminated soil. The method utilizes physical and mechanical principles to mix or replace the cleaned soil with the contaminated soil to achieve the purpose of diluting and reducing the pollutant content and repairing the contaminated soil. In the process of repair, in order to effectively prevent the transfer of pollution, on the basis of the investigation and evaluation of farmland soil pollution, through the calculation of earthwork, priority should be given to the amount of earthwork in each area, and cross-distribution between areas should be avoided as much as possible. If the excavation and filling balance of the earthwork cannot be achieved in the area, the method of adjusting the earthwork and the amount of the soil to be cleaned must be calculated. Special emphasis is, we should strive to avoid the transfer of contaminated soil to prevent contamination expanded, and should carry out soil fertility, Additions of organic matter and other measures in the warning area, the inhibitory effect of heavy metals bioavailability, in order to reduce pollution levels. The mixed-dilution method of excavating and filling soil has the advantages of rapid pollution control, obvious effect and wide adaptability for farmland with heavy pollution and small area; however, for areas with large pollution area, it consumes a lot of manpower and material resources, and there is secondary pollution. And the problem of destroying soil structure and reducing soil fertility.

2. The Agricultural Production Adjustment Law, which combines the measures of controlling soil moisture, adjusting soil pH and Eh value, changing farming system, adjusting crop types and rational application of organic fertilizer in soil-contaminated agricultural remediation technology, and the geo-retention project in land leveling. According to the source, nature and pollution degree of the pollutants, scientific and reasonable agricultural production methods are selected to complete the soil pollution restoration in the routine agricultural operation. For example, changing the farming system and adjusting the soil pH and Eh value can reduce the toxic effects of heavy metals in the soil; rational application of organic fertilizers such as compost, manure and crop straw can not only increase soil organic matter content, improve soil physical and chemical properties, but also increase soil. The adsorption capacity of colloids on heavy metals and other pollutants affects its morphology and bioavailability in soil. In addition, adjusting the crop species can also reduce the toxic effects of pollutants. In areas with low pollution, crop varieties with strong stain resistance can be planted; in areas with heavy pollution, crops will be abandoned, and ornamental flowers and economic forests will be replanted. The agricultural production adjustment method has the advantages of low cost, no side effects and convenient implementation. However, its repair effect is poor and the cycle is long. It is only suitable for the repair of medium and light pollution, and should be combined with other technologies when necessary. Cooperate.

3. Plant in situ restoration and improvement method, which combines soil pollution phytoremediation technology such as plant fixation, plant extraction, plant evaporation and root filtration with the geotechnical maintenance project in land leveling. In the geotechnical maintenance project, planting and screening plants, exerting its own unique mechanism, and simultaneously accomplishing the dual tasks of increasing soil fertility, improving soil physical and chemical properties and passivation, reducing pollutant content, and controlling pollution. Most of the plants screened by the in situ restoration improvement method are leguminous plants, such as alfalfa and perennial ryegrass. Compared with the physicochemical method, the method has the advantages of maintaining the physical and chemical shape of the soil, low treatment cost, good repair effect, easy operation and management, and the like, and is suitable for the repair and treatment of large-area and low-concentration soil pollution, but it is also affected by environmental factors. It has long repair time and can only repair certain types of pollutants and easily cause secondary pollution.