Farmland environmental pollution will first slow down the growth and development of vegetables, reduce the ability to resist pests and diseases, reduce the quality of vegetables, and directly reduce the production efficiency of vegetable bases. Secondly, some pollutants will be enriched in vegetables and endanger human health through the food chain. It is very unfavorable for the long-term development of vegetable industry to fail to produce green pollution-free vegetables that are safe to eat. Therefore, it is necessary to strengthen the monitoring and control of environmental pollution in vegetable producing areas and create conditions for the healthy and sustainable development of vegetable industry in our city.
1. Industrial pollution
Linfen is rich in coal and iron ore resources, and has a long tradition of coal mining, coking and ironmaking. Coal, coke and iron are traditional pillar industries, accounting for 70% of the total industrial output value in Linfen, and the amount of waste gas, waste water and waste residue produced is difficult to count, which is the main environmental pollution source in Linfen Basin.
1. 1 waste gas pollution
The air pollution in Linfen is mainly soot pollution. In addition to the emissions from factory boilers, thousands of households also emit a lot of smoke and dust in winter. Air pollution is mainly around densely populated towns and polluting factories, and the main components are sulfur dioxide, nitrogen oxides, smoke and dust, metal dust and so on. Taking sulfur dioxide as an example, the average concentration of sulfur dioxide in the air in the city reached 2. 24 mg/m3。 It is 73 times higher than the national secondary standard. Except for Quwo, the concentration of atmospheric sulfur dioxide in Pingchuan county and city failed to meet the national second-class standard. The resistance of vegetables to sulfur dioxide is weak, and a small amount of pollution will cause different degrees of damage, affecting the yield and quality of vegetables. The harm of nitrogen oxides to vegetables is similar to that of sulfur dioxide, but it also causes nitrate in vegetables to exceed the standard. Smoke and dust will be deposited on vegetable leaves, which will affect photosynthesis and reduce yield and vegetable quality. Metal particles in soot, such as lead, cadmium, chromium, zinc, arsenic, mercury, nickel and manganese, can float in the air for a long time, so they are called "floating dust". Metal "floating dust" is easy to spread to distant areas with air flow, and is directly or indirectly absorbed by plants or pollutes soil, resulting in heavy metal pollution of vegetables, and its harm range is wider.
Pingchuan District of Linfen is located in a banded basin with an altitude of more than 200 meters. Air circulation is slow, on the one hand, it is easy to form a warm and humid climate, on the other hand, pollutants are not easy to spread. Especially after entering June 5438+065438+ 10 every year, it is easy to form an atmospheric inversion layer, which makes the temperature above the basin higher than the ground, the atmospheric convection disappears, the generation and accumulation of gas pollutants increase, the air visibility is extremely low, and the pollution is aggravated, which is not conducive to the growth of greenhouse vegetables in winter.
1.2 wastewater pollution
The water conservancy conditions in Pingchuan area of Linfen City are convenient, and the Fenhe River runs through the north and south ends of the basin. Its tributaries and rich shallow groundwater have always been the main sources of local agricultural irrigation water. However, due to the arbitrary discharge of industrial sewage, the water quality of Fenhe River and some tributaries is worse than the fifth category, which is not suitable for direct irrigation. The shallow groundwater on both sides of the river is also polluted to varying degrees, which poses a threat to the production of pollution-free (green) vegetables.
The industrial sewage discharged into Fenhe River in our city mainly comes from coal washing plants, coking plants, pharmaceutical factories, paper mills, metallurgy and other industries. Harmful components are complex, mainly including phenols, benzene, ammonia nitrogen, chloride, cyanide, organic suspended solids, mercury, cadmium, chromium and other pollutants. Vegetables are crops that consume much more water, and water pollution has a great influence on the growth, quality and safety of vegetables. It is easy to cause the decline of vegetable output and the pollutants in the products exceed the standard. Water pollution will cause soil salinization and accumulation of heavy metals, leading to farmland degradation.
2. Traffic pollution
Linfen basin is located in the north-south traffic area of Shanxi, and it is also an important industrial and commercial concentration area. The traffic on the main roads in China is very busy, and there are many vehicles carrying coal. Motor vehicles transporting coal will cause coal dust and dust pollution to farmland on both sides of the highway, which will affect crop photosynthesis. Automobile exhaust will also reduce the yield and quality of crops on both sides of the road, mainly containing hydrocarbons, nitrogen oxides, lead dust and other toxic substances, especially when some coal trucks are overloaded and the engines are aging, the exhaust pollutants are extremely serious. The friction between motor vehicle tires and asphalt pavement will also produce polycyclic aromatic hydrocarbons pollutants, which will affect the food safety of vegetables.
3. Garbage pollution
Due to the random dumping of municipal solid waste, some vegetable production bases in the suburbs of the city suffer from garbage. Both sides of vegetable base roads and adjacent residential areas often become garbage accumulation sites, which leads to the breeding of mosquitoes, flies and dust in the wind. Municipal solid waste is not only rich in organic matter, but also contains many dangerous pollutants such as waste batteries and waste circuit boards, which can produce heavy metal ions such as mercury and cadmium and pollute the vegetable environment. Plastic bags, boxes in domestic garbage and agricultural plastic films left in farmland are called "white pollution", in which diphenols, phthalates, polyethylene, PCB PCBs and other components can be gradually dissolved and infiltrated into farmland, polluting vegetables and endangering human health.
4. Agricultural pollution
Agricultural pollution refers to the pollution caused by unreasonable use of agricultural means of production such as pesticides, fertilizers and hormones in the process of agricultural production, among which pesticide and fertilizer pollution are the most common. Due to the low application level, improper application methods and poor performance of application equipment, the loss of pesticides is serious, and only 10% ~ 20% is often attached to the surface of vegetables, and most of them are scattered in the soil. Pesticides can be gradually decomposed in soil, but the half-lives of different kinds are different. The half-life of some pesticides with high residues in soil can reach 100 years, which is extremely harmful and has been banned from production and use, such as bhc and DDT. Pesticide residues in soil will lead to excessive pesticide residues in vegetables and affect food safety.
Chemical fertilizer pollution is mainly caused by unreasonable use of chemical fertilizers. Irrational fertilizer structure and biased application of nitrogen fertilizer will lead to excessive nitrate content in vegetables, especially under greenhouse cultivation conditions. Some inferior phosphorus, potassium and boron fertilizers will bring heavy metal pollutants to farmland environment, resulting in excessive toxic elements such as arsenic, cadmium, chromium and palladium in vegetables. It is worth noting that the application of organic fertilizer to vegetables will also cause heavy metal pollution, mainly because the heavy metal elements in feed exceed the standard, so it should be used with caution.
Second, the solution
Industrial pollution control
The control of agricultural environmental pollution can not be solved by the agricultural sector alone, but by the coordinated operation and comprehensive improvement of various government departments, especially environmental protection departments, in order to reverse the serious situation of environmental pollution. In recent years, Linfen Municipal Party Committee and Municipal Government put environmental protection in the first place, and fought a tough battle to control the environment, in order to realize the fundamental improvement of the city's environmental quality and return Linfen people to a clear water and blue sky. The following measures should be taken to improve the farmland production environment.
1. 1 Strengthen governance and control pollutant discharge.
Existing enterprises that discharge industrial "three wastes" should be strictly cleaned up and rectified. Those who fail to meet the national emission standards should be treated within a time limit, and those who fail to achieve results within a time limit should be closed down for rectification. We must resolutely learn from earth coke ovens, improved coke, small iron making, small oil refining and small paper making. It is forbidden by the state to prevent resurgence. The backward production processes, technologies and equipment eliminated by the state within a time limit should be stopped within a time limit and not relented. Policies and management measures should be taken to guide and support coking enterprises to develop coal chemical industry, recover by-products such as gas and tar, extend the industrial chain, and fundamentally reduce pollution.
1.2 improve the entry threshold and reduce pollution projects.
Environmental protection departments should ensure good market access, implement a one-vote veto system for environmental protection, resolutely veto projects that do not meet the national industrial policies and environmental protection requirements, resolutely veto projects with total pollution exceeding the total control index, and resolutely veto projects with backward technology that have been eliminated.
1.3 Transform the growth mode and develop circular economy.
The traditional industrial growth model is at the expense of huge environmental sacrifices. Circular economy can organically combine environmental protection and development, treat wastes harmlessly through continuous recycling of resources, and minimize resource consumption and pollutant discharge. To realize the coordinated development between man and nature, we must completely change the economic growth mode at the expense of the environment. To this end, the first is to achieve cleaner production in all enterprises in the city. The second is to fully implement the circular economy model in industrial parks where enterprises are concentrated, and organize production in the form of eco-industry. Third, take the county as a unit, implement environmental capacity control, and the environmental capacity determines the total amount of emissions, and implement total pollution control. Counties (cities, districts) that are close to or exceed the environmental capacity will no longer approve projects with serious pollution such as coking and ironmaking.
2. Control rural pollution
2. 1 Popularize integrated pest control technology and scientific fertilization technology.
In the prevention and control of vegetable diseases and insect pests, it is necessary to vigorously promote the new pollution-free comprehensive control technology, advocate the use of new high-efficiency and low-toxicity pesticides for chemical control, and use insecticidal lamps, insect nets and other devices for physical or biological control to reduce pesticide pollution. It is necessary to vigorously carry out the work of "reducing and increasing efficiency" of pesticides, update pesticide varieties and dosage forms, popularize new application equipment, improve drug efficacy and reduce pollution. Vigorously promote scientific fertilization techniques such as soil testing formula, and promote the use of new fertilizers such as special fertilizers, compound fertilizers, biological fertilizers, slow-release fertilizers and biogas fertilizers to meet the production requirements of pollution-free vegetables.
2.2 Promote new energy technologies and reduce rural life pollution.
The majority of rural residents in our city live in scattered areas, and their living pollution has different characteristics from those of urban residents. For example, central heating and gas can not be realized, so the soot pollution caused by heating in winter and daily cooking is higher than the per capita level of urban residents. To this end, the following measures should be taken: First, integrate immigrants into qualified villages, build small towns, and implement central heating and gas supply. The second is to encourage or subsidize the use of clean energy, such as briquette, anthracite, straw gasification, small gas, biogas and other rural new energy technologies to reduce soot pollution. Rural domestic garbage should be concentrated and properly disposed of, and should not be discarded in front of the door or behind the farm. harmful waste such as batteries should be recycled to avoid serious pollution to the farmland production environment.
3. Treatment and control of urban garbage and industrial waste residue
It is difficult to treat urban garbage and industrial waste residue. Dumping in farmland occupies a lot of cultivated land, and dumping in rivers pollutes water sources and destroys natural landscapes. Municipal solid waste is mainly composed of coal cinder and building materials waste, and also contains a lot of organic pollutants that can produce stench and germs, as well as some highly toxic pollutants such as batteries and waste circuit boards. Traditionally, landfill is the main treatment method, which will pollute groundwater. The composition of industrial waste residue is stable, and most of it can be used as building materials. The main problem is whether the utilization rate is low or mainly buried. The following methods can be used to treat domestic garbage and industrial waste residue: First, develop the technology of combined incineration of gas and garbage to generate electricity. Most of the gas produced by coking enterprises in our city is white-burned. If it is used as a combustion-supporting substance of domestic waste, it can solve the problems of high moisture content and low calorific value of domestic waste. Based on this resource advantage, combined power generation technology with local characteristics should be developed. The second is to develop the garbage building materials industry. Using industrial waste residue and domestic garbage as raw materials of building materials can not only reduce land occupation, but also solidify heavy metal pollutants in building materials and reduce environmental pollution. At present, the technology of making bricks and concrete components from garbage is very mature, and has formed production capacity in some places where building materials are scarce. As a building material, waste has the disadvantages of high technical requirements and high cost, but its good ecological benefits are its main value. The government should restrict the use of ordinary clay bricks and concrete components in policy and support the development of waste building materials industry.
4. Do a good job in the planning and construction of pollution-free vegetable bases
Pollution-free is the minimum quality requirement of future agricultural products, and pollution-free vegetable production must have a good agricultural environment. Traditional vegetable production is often concentrated in urban suburbs and on both sides of traffic arteries, but urban suburbs and on both sides of traffic arteries are also concentrated areas of urban pollution, industrial pollution and traffic pollution, which is not an ideal environment for vegetable production. Therefore, it is necessary to strengthen the location and planning of vegetable bases, so as to keep them away from pollution sources such as urban suburbs, industrial and mining enterprises and traffic arteries. Before the site selection, the farmland environment should be scientifically monitored and evaluated to find out the content of heavy metals in soil, the quality grade of irrigation water, the quality of atmospheric environment and the pesticide residues in soil. Agricultural land that cannot meet the requirements of pollution-free environmental conditions shall not be used for vegetable production, and non-edible and non-medicinal crops may be planted. Pollution-free vegetable base requires not only a good agricultural environment, but also strict compliance with pollution-free production technical regulations and prevention of agricultural chemical pollution, and must strengthen management and technical guidance. In recent years, our city has implemented pollution-free vegetable facilities project in the south of Jinzhong, involving six counties (urban areas) including Du Yao, Houma, Yicheng, Quwo, Xiangfen and Hongdong. The project implementation area covers an area of 28,500 mu of sunlight greenhouse and 77,900 mu of arch shed. Agricultural management departments should take these demonstration areas as bases, demonstrate and popularize pollution-free production technologies, radiate and drive surrounding areas, expand production scale, make pollution-free vegetable production develop rapidly, and give play to the advantages of vegetable industry.