Pesticide is an indispensable means of production in agricultural production, and it is also a toxic and harmful chemical substance. Unreasonable use will lead to harm to human health and ecological environment. With the arrival of the new century, people's requirements for environmental quality and food safety are getting higher and higher. Due to various reasons, the present situation of pesticide pollution in China is not optimistic, and it is quite serious in some places. It is more and more important to improve the environmental awareness of the whole people and prevent pesticide pollution.

1. Development of pesticides

Generally speaking, the development of pesticides has gone through three historical stages, namely, the natural medicine era (1before 1970s), the inorganic synthetic pesticide era (1from 1970s to mid-1940s) and the organic synthetic pesticide era.

2. Present situation of chemical pesticide pollution in China

China is a big agricultural country with many kinds of pesticides and a large number of users. Among them, 70%~80% pesticides directly penetrate into the environment, causing pollution to soil, surface water, groundwater and agricultural products, and further entering the biological chain, causing serious, long-term and potential harm to all environmental organisms and human health.

Since the establishment of the plant protection policy of "prevention first and comprehensive control" in China, the technical level of crop pest control has made great achievements, but there are also outstanding problems such as excessive use of chemical pesticides, and some areas rely solely on chemical pesticides to control pests and diseases. China has restricted the production and use of organochlorine since 1983, and the pollution of organochlorine to the environment has been greatly improved. However, local and intermittent pollution will occur in heavily polluted areas of organochlorine.

The scale, equipment and technical force of chemical pesticide production enterprises in China are relatively backward, and the quality of chemical pesticides is not satisfactory. In recent ten years, although the contract varieties of chemical agriculture have changed greatly and many new varieties have been developed, the old traditional varieties are still dominant, the proportion of various chemical pesticides is unreasonable, the products are aging and the dosage forms are monotonous.

In China, pesticide 1 accounts for more than 70% of chemical pesticides, of which highly toxic pesticide organophosphorus accounts for more than 70%; There are 12 varieties with an original yield of more than 10,000 tons, including insecticide l 1 and herbicide L 1. Compared with foreign countries, there is a big gap in the development of pesticides. In the United States, the ratio of pesticide technical to preparation is 1: 36, which means that there are often 36 preparations for a pesticide, and the ratio in Japan is L: 30, while that in China is only L: 5, so there is great room for development.

3. The harm of pesticides

3. 1 Harm of pesticide pollution to human health

Pesticide is not only an important agricultural means of production, but also a chemical substance harmful to organisms, that is, toxic. Pesticides can enter human body through digestive tract, respiratory tract and skin and cause poisoning, including acute poisoning and chronic poisoning. Drug poisoning is caused by people's different lifestyles, eating unsanitary fruits and vegetables by mistake and not paying attention to personal hygiene, while some pesticides can be dissolved in human fat and sweat, especially organophosphorus pesticides, which can enter the human body through the skin and endanger human health.

Acute poisoning mostly occurs in highly effective pesticides, especially highly toxic organophosphorus pesticides and carbamate pesticides. Acute poisoning of these two pesticides can cause dizziness, headache, nausea, vomiting, sweating and weakness. Severe cases include coma, convulsion, spitting, pulmonary edema, extremely difficult breathing, incontinence and even death. Chronic poisoning is often persistent, inhalation or skin contact with a small amount of pesticides; Causes the poison to gradually appear pathological changes and poisoning symptoms after entering the human body. This process is usually slow in onset, long in course and difficult to distinguish symptoms, which is often ignored by people. In addition to the researchers and producers of pesticides, millions of people in China are exposed to pesticides due to transportation, storage and use, which is a quite large group. Because of poor self-protection facilities and poor self-protection consciousness of pesticide users, drug poisoning is caused and life is endangered.

3.2 pesticide pollution to the ecological environment

With the development of science today, the pollution of pesticides to the ecological environment is particularly serious. Why is this? It includes a process from quantitative change to qualitative change. We can understand pesticide pollution from two aspects: background value standard and pesticide hygiene standard or biological standard. If the content of pollutants exceeds the background value and reaches a certain value, it is called pollution. The concentration of pollutants exceeds the hygienic standard or biological standard, which is generally called pollution or serious pollution. These are harmful to human health, biology and environment.

3.2. 1 Pesticide pollution to water environment

3.2. 1. 1 Sources of pesticides in water

The sources of pesticides in water mainly include the following aspects: pesticides are directly applied to water; Rainwater containing pesticides falls into the water body; Pesticides attached to plants or soil enter the water body after being washed or dissolved by water; Industrial wastewater from pesticide production or domestic sewage containing pesticides will always endanger the quality of surface water and groundwater, which is not conducive to the survival of aquatic organisms and even destroys the balance of water ecological environment.

3.2. 1.2 Harm of pesticide pollution to water environment

During the extensive use of organic pesticides, HCH and Didi Didi Didi were detected in some famous rivers in the world, such as Mississippi River and Rhine River. Sometimes pesticides such as dichlorvos and trichlorfon are applied on the water surface to control mosquito larvae; In order to eliminate weeds in channels, reservoirs and lakes, aquatic herbicides are used, resulting in high pesticide concentration in water and a large number of aquatic animals such as fish and shrimp die. Some pesticide preparation points still have a lot of packaging materials such as medicine bottles at night, which will cause runoff pollution after rainfall, and random cleaning of application tools will also cause water pollution.

3.2.2 Pesticide pollution to soil

3.2.2. 1 Sources of pesticides in soil

There are three ways for pesticides to enter the soil: the first way is for pesticides to enter the soil directly, including some herbicides, insecticides for controlling underground pests and seed dressing agents. The latter is applied to the soil with seeds to prevent nematodes and seedling diseases, and basically these pesticides enter the soil in this way; The second is to control pests and diseases by spraying various pesticides on farmland. Their direct targets are insects and grass, aiming at protecting crops, but a considerable part of pesticides fall on the soil surface or the water surface of rice fields and indirectly enter the soil. The third is that irrigation water and plant residues settle with the atmosphere.

Effects of soil pesticides on crops and soil organisms in 3.2.2.2

The impact of soil pesticides on crops is mainly manifested in the impact on crop growth and the absorption of pesticides by crops in the soil, which reduces the quality of agricultural products. The absorption of soil pesticides by crops mainly depends on the types of pesticides. Generally, water-soluble pesticide plants are easy to absorb, while fat-soluble pesticide plants strongly adsorbed by soil are not easy to absorb.

The experimental data of the former Soviet Union showed that dimethoate, a water-soluble pesticide, was easily absorbed by lettuce, oats and radish F, and the ratio of pesticide concentration in crops to soil was 5.3-4.8. The absorption coefficient of dimethoate by plants is very high, and crops can easily absorb pesticides from sandy soil, but it is difficult to absorb pesticides from clay and organic matter. Earthworms are the most important invertebrates in the soil, which are of great significance for maintaining a good soil structure and improving soil fertility. However, some highly toxic pesticides, such as toxaphene, parathion and ground insect phosphorus, can kill them in a short time.

In addition, the influence of pesticides on soil microorganisms is another issue that people pay attention to, that is, the influence of pesticides on the total number of microorganisms, nitrification, ammoniation and respiration. Fungicides have a great influence on soil microorganisms, which can not only kill or control pathogenic microorganisms, but also harm some beneficial microorganisms, such as nitrifying bacteria and ammonifying bacteria. With the decrease of pesticide dosage per unit cultivated area, the influence of herbicides and pesticides on soil microorganisms is further weakened, and the negative influence of fungicides on soil microorganisms will become our concern. 3.2.3 Pollution of pesticides to the atmosphere

Due to the different geographical location and spatial distance of pesticide pollution, the amount of pesticides in the air is distributed in three zones. The first area is the drug source area that causes pesticides to enter the air. The concentration of pesticides in the air in this area is the highest, and then the pesticides in the air gradually spread and dilute due to the action of airflow, away from the use area. In addition, due to evaporation and volatilization, pesticides on the treated target and in the soil diffuse into the air. Because of these effects, a second air pollution area was formed near the pesticide application area. In this area, the concentration of pesticides is generally lower than that in the first area due to diffusion and air convection. However, under certain meteorological conditions, when the air mass cannot be completely mixed, the concentration of pesticides in the air in some areas may be high. The third area is the area with the widest migration of pesticides and the lowest concentration of pesticides in the atmosphere. Due to the different meteorological conditions and application methods, the distance in this area can spread to hundreds or even thousands of kilometers away from the drug source.

The degree of air pollution caused by pesticides is also related to factors such as pesticide varieties, pesticide formulations and meteorological conditions. The pollution of volatile pesticides, aerosols and powders is quite serious, and long residual pesticides last for a long time in the atmosphere. Other things being equal, wind speed plays an important role. High wind speed increases the distance of pesticide diffusion area and the amount of pesticide entering it.

The extensive use of chemical pesticides not only causes the pollution of soil, air and water resources, but also produces the residue, enrichment and lethal effect of chemical pesticides in animals and plants, which has become a major problem that destroys the ecological environment, biodiversity and sustainable development of agriculture, and should be paid full attention to. How to solve this problem has also become the focus of attention. The author believes that in agricultural production, we should give full play to the existing natural pest control mechanism in farmland ecosystem, comprehensively use effective ecological control means such as agricultural control, physical and mechanical control, biological control, etc., and minimize the use of chemical pesticides.

4. Characteristics of pesticide pollution

The pollution of chemical pesticides to the environment is mainly poisoning the atmosphere, water system and soil, causing pollution to nature, affecting all kinds of creatures living in nature, causing changes in biota, reducing and disappearing sensitive species, and increasing and strengthening polluted species.

4. 1 Direct toxicity of chemical pesticides to organisms

Chemical pesticides can be divided into three categories, namely insecticides, fungicides and herbicides. Insecticide is a non-specific poison, not only for a target pest, but also for all life, which is the most harmful to human beings. At present, nearly one million people are poisoned by pesticides and tens of thousands of people die every year in the world. Although some chemical pesticides have low acute toxicity, they have serious potential harm to the environment after application, and have high chronic or "three-cause" toxicity, that is, they may eventually lead to teratogenesis and carcinogenesis in animals, and may even destroy the genetic mechanism of organisms and cause kevin keegan mutation.

4.2 "3R" problem of chemical pesticides

First, the continuous use of pesticides has led to the increase of insect resistance, and the use of chemical pesticides has gradually lost its normal control effect. Therefore, only by increasing the dosage and frequency of pesticides can we eliminate pesticides and aggravate the impact of chemical pesticides on the environment. Second, because most pesticides used at present are still not selective, they often kill natural enemies while killing pests, which leads to the resurgence of pests and the rise of secondary pests. Third, chemical pesticides will remain in crops and other environmental factors (soil, agricultural products, groundwater, etc.). ) after using various forms. With the residue, there will be the problem of biological enrichment. Due to biological enrichment and food chain transmission, many a mickle makes a muckle, and low toxicity becomes high toxicity, which poses a great potential threat to human health.

5. Implement continuous plant protection and control pesticide pollution.

Although China has made some achievements in pest control since the implementation of the plant protection policy of "prevention first and comprehensive control", the task of controlling environmental pollution caused by chemical pesticides is still quite arduous. It is necessary to carry out continuous plant protection, so that the plant protection function can take into account the requirements of continuous yield increase, human and animal safety, environmental protection and ecological balance, and study the ecological population dynamics and related environment for the whole farmland ecosystem. Adopt L}j coordinated and effective control measures as far as possible, give full play to the role of natural inhibitors, control pest population at the level of economic loss, and minimize the adverse effects of control measures on farmland ecosystem in order to obtain the best economy and ecology; FlI social welfare.

5. 1 Establish a new idea of pest control.

Biological control is an important part of comprehensive management. Biological control agents (natural enemy insects and insect pathogenic microorganisms) are used to regulate the population density of harmful organisms, maintain biodiversity in the ecosystem through biological control, and protect organisms with biodiversity, so as to keep the population density below the economically allowable harm level. Traditional pest control is mainly through measures such as disease resistance, insect species and plant quarantine, cultivation system and physical and chemical control.

From the perspective of sustainable agriculture, pest control should be realized at a higher level, including the use of transgenic plants with disease resistance and insect resistance, the use of ecology to control diseases and pests, and the use of biological resistance. Transferring cloned disease-resistant and insect-resistant genes into the genome of excellent varieties by biological means to obtain new varieties with high disease-resistant and insect-resistant properties has been a hot spot in disease-resistant and insect-resistant breeding for scholars all over the world in the past two decades, and a major breakthrough has been made at present. For example, high-efficiency insect-resistant cotton, insect-resistant rice and insect-resistant Chinese cabbage were successfully obtained by transferring Bt gene of Bacillus thuringiensis, among which insect-resistant cotton has been widely used in production. The Institute of Microbiology of China Academy of Sciences successfully transformed Bt gene into poplar, and the insect-resistant poplar obtained has entered the field experiment stage. Crops, pests and environment are an interdependent and competitive entity. By improving the ecological environment, such as rotation leisure, crop layout, farming system, cultivation management, etc. It can adjust the growth and development of crops to control the harm of pests. In recent years, the cultivation and utilization of transgenic herbicide-resistant crops has become one of the focuses of breeding and plant protection. At present, corn, soybean, rape, cotton and other herbicide-resistant crops and herbicide-resistant tobacco 1 have been obtained, which makes some herbicides with low selectivity widely used and effectively controls the succession of weed communities.

5.2 Vigorously develop botanical pesticides

Botanical pesticides have the advantages of fast biodegradation in the environment, low toxicity to people and animals and non-target protection organisms, low resistance to pests, low cost and easy availability. In particular, tropical plants contain active ingredients of plant-derived pest control agents, which have great application prospects. At present, at least 10 species of Meliaceae plants have insecticidal activity and are potential substitutes for chemically synthesized pesticides. Botanical pesticides have unique advantages in overcoming insect resistance and reducing environmental pollution. In recent years, China's botanical pesticides have developed rapidly, and there have been small-scale industrial production of rotenone, nicotine sulfate, nicotine oleate, oxymatrine and toosendan seed preparation.

5.3 Research and development of new pest monitoring technology

On the basis of routine monitoring methods of plant pathogens such as spore capture, utilization of food plants and serological identification, research on molecular monitoring technology of pathogens should be carried out, and the fluctuation of genetic composition of pathogenic species and races should be monitored by modern molecular biology technology to provide basic data for long-term and ultra-long-term prediction of diseases. Modern genetic marker technology (RFLP RAPD, etc.). ) can also be used to monitor the migration law of pest population. For weeds, we should fully consider the succession law of weed community, analyze the competitive relationship between crops-weeds and weeds-weeds, and also consider the influence of selective herbicides on weed community to study the ecological control of weeds.

5.4 establish super-long-term prediction and macro-control of pests

In order to adapt to the sustainable development of agriculture, it is necessary to make a scientific judgment on the growth and decline of pests, that is, to predict the growth and decline of pests for several years or even ten years It is not only the climatic factors closely related to the growth and decline of pest population, but also the planting structure, environmental protection requirements, plant protection policies and policies and measures formulated by the state to realize the sustainable and stable development of agricultural production.

5.5 Establish a long-term and repeated pest control idea.

Since the history of planting crops, pests and weeds have been restricting the yield and quality of agricultural products, but the technical problems such as the loss of disease resistance of varieties, the emergence of drug resistance of pests, the unpredictable succession law of pests, the contradiction between crop genetic diversity required by pest control and the simplification of varieties required by production, cultivation and commerce have not been solved. At the same time, some pests that have been controlled will rise again after relaxing control or changing environmental conditions, such as four pandemics of soybean gray leaf spot in the 1960s and 1990s, wheat smut that caused great harm in the 1960s, 1998, 1999 and grassland borer that was rampant in the early 1980s in the spring. The trend of alternating changes shows that the prevention and control of plant diseases, pests and weeds is long-term and repetitive, and plant protection work should adapt to the changes of agricultural production conditions, ecological environment and environmental protection requirements, and establish a continuous thinking of controlling harmful biological hazards under the new situation. At the same time, gradually establish a scientific and perfect plant protection technical support system and a stable plant protection scientific and technological team that adapts to the direction of sustainable agricultural development, and make contributions to ensuring the sustained, healthy and stable development of agricultural production at a higher level.