After a large amount of pesticides are applied, pesticide residues or deep groundwater are caused, which also pollutes the water source. In recent years, the low price of garlic was caused by excessive pesticide residues and the cancellation of acquisition by foreign buyers. We may also fail to test our own consumption, but the awareness of the domestic people is not so high, and then the cost of their own tests is too high. Ordinary people can't afford it.
    Organic pesticides can be classified into organophosphorus pesticides, organochlorine pesticides, organic nitrogen pesticides, organic sulfur pesticides, organometallic pesticides, and organic pesticides containing groups such as nitro, amide, nitrile, and triazine. Among the above-mentioned several types of organic pesticides, the application history is the longest in organochlorine pesticides; on the varieties, the organophosphorus pesticides are the most. The organochlorine pesticides used in China are mainly BHC and DDT . In the western countries, there are cyclopentadiene compounds such as aldrin, dieldrin, and endrin. These compounds are stable in nature and require half or even ten years to degrade in the soil. They can enter the water body with runoff, drift with the atmosphere to the rest of the world, and then fall to the ground with rain and snow. Therefore, organochlorine pesticides can also be detected in Antarctica and Greenland. Certain organometallic pesticides, such as organic mercury bactericides , are stable in nature and the residual toxicity of the degradation products is quite severe and has been banned in most countries.
    There are very few varieties of inorganic pesticides applied. Inorganic pesticides used in some areas are mainly mercury-containing fungicides and arsenic-containing pesticides. Mercury-containing fungicides such as mercuric chloride (mercury chloride) and calomel (mercury chloride), which can damage crops, are generally used only for seed disinfection and soil disinfection. Mercury preparations are generally stable in nature, highly toxic, and have serious problems in soil and organisms. Many countries such as China, the United States, Japan, and Sweden have banned their use. The arsenic-containing pesticides are arsenious acid compounds such as arsenious acid (arsenic) and sodium arsenite, and arsenic acid compounds such as lead arsenate and calcium arsenate. Arsenic compounds are highly toxic to plants and have been used as baits to control underground pests. Arsenic compounds have been widely used to control chewing mouthparts pests, but they have also been replaced by organic insecticides due to narrow control surfaces and low efficacy.
    All kinds of pesticides do not have residual toxicity problems (see pesticide residues), and the same type of pesticides of different types have different environmental hazards. The different processing forms of pesticides can spread and cover the pesticide on the surface of the crop, whether the sprayed liquid (or powder) can stably adhere to the surface of the crop, and whether the pesticide can penetrate the stratum corneum of the plant surface. Loss and so on will have an impact, which will make the difference in the degree of pollution of pesticides. In addition, the physical properties of different pesticide formulations in soil loss, leakage and adsorption are not the same, so their residual capacity in the soil is also different.
    Pesticide pollution is mainly caused by organochlorine pesticide pollution, organophosphorus pesticide pollution and organic nitrogen pesticide pollution. People take pesticides from the environment mainly through diet. The reasons for the presence of pesticides in plant foods are the direct contamination of the medicament and the absorption of the pesticide from the surrounding environment. Animal foods contain pesticides that are ingested by animals through the food chain or directly from water. The residual concentration of pesticides in the environment is generally very low, but the concentration of pesticides in the organism can be increased to several thousand times or even tens of thousands of times through the food chain and bioconcentration (see the health effects of pesticide pollution).
Pesticides are degradable in the natural environment. Organophosphorus pesticides are easily degraded. Organochlorine pesticides that are difficult to degrade can also be slowly degraded by microorganisms, ultraviolet light and other factors. Pesticides also undergo metabolism and degradation in living organisms. In general, the degradation of pesticides or the toxicity of metabolites is less than that of the parent. However, there are several situations that should be noted : First, some degradation or metabolites are more toxic than broodstock. For example, 4- chloro-o-toluidine , a degradation product of chlorpyrifos, is much more carcinogenic to mice than larvae. Second, although the degradation products are less toxic, the properties have changed. For example, the solubility of some pesticide degradation products is increased, and the harmfulness is enhanced. Third, some pesticides are non-toxic and their metabolites are toxic . For example , ethylene thiourea, a degradation product formed by disulfide carbamates, has teratogenic and mutagenic effects on the test animals, and the parent compound Will not play this role. Fourth, the residual toxicity of some pesticides after use is caused by impurities contained in the medicine . For example, the herbicide 2,4,5-T has a teratogenic effect on animals because the product contains impurity tetrachlorodiene. Therefore, in what kind of natural environment, the degradation of pesticides is a subject that must be further studied. Regarding the chronic toxicity of pesticides, in addition to the conclusions of organic mercury, 2,4,5-T , and insecticides , most of the pesticides, including the currently widely used pesticides, have no definitive conclusions. When assessing the chronic toxicity of a pesticide, in addition to considering the impact on human health, the impact on the organism should also be considered.
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