First, photolysis
Herbicides applied to plants and soil surfaces undergo photochemical decomposition under sunlight. This photolysis is caused by ultraviolet light, and the photolysis rate depends on the type, species, and molecular structure of the herbicide. The factors such as the intensity of UV light, the ability of herbicide molecules to absorb light, and temperature are all factors that affect photolysis.
Most herbicide solutions can perform photolysis, which absorbs the spectrum from 220 to 400 nm; the photolysis rates of different types of herbicides vary greatly, and the dinitroaniline herbicides, especially trifluralin, are most easily photolyzable. The speed of photolysis of other herbicides is slightly slower. To prevent photolysis, chemicals should be mixed in the soil after spraying.
Second, volatile
Volatilization is one of the important ways for the disappearance of herbicides, especially soil treatment herbicides. The volatility is closely related to the physical properties of the compounds and saturation vapor pressure, and is also constrained by environmental factors; herbicides with high saturation vapor pressure are volatile. Strong; dinitroaniline herbicides belong to the category of higher saturation vapor pressure, followed by thiourethane herbicides. After spraying these herbicides on the soil surface, they will quickly volatilize and lose their activity. Volatile gases are more likely to damage sensitive crops.
Among environmental factors, temperature and soil moisture have the greatest influence on the volatilization of herbicides: the temperature rises, the saturated vapor pressure increases, the greater the volatility; the high soil moisture is favorable for desorption, making the herbicide easy to release in the soil solution. In a free state, it is easy to vaporize and evaporate.
Third, soil adsorption
Adsorption is closely related to the biological activity of the herbicide and its residual in the soil and the persistence period. Herbicides are mainly adsorbed by soil colloids in the soil and contain physical adsorption and chemical adsorption. The adsorption of herbicide by soil depends on the molecular structure of the herbicide on the one hand, and on the other hand, it depends on the content of organic matter and clay in the soil. Many types of herbicides such as urea, homotriazine, and thio-amino acid esters are in soil. It is easy to be adsorbed, and the sulfonylurea and imidazolinone herbicides are not easily adsorbed; soils with high organic matter and clay content have strong adsorption to herbicides. In the use of soil treatment herbicides, the adsorption capacity of the soil colloids to herbicides should be considered to be saturated. Therefore, the dosage per unit area should be appropriately increased or decreased with the soil organic matter and clay content, and irrigation can also be carried out to promote the herbicides. Desorption thus enhances the herbicide effect.
IV. Leaching
Leaching is the distribution of herbicides in the soil with the movement of water in soil profiles. Leaching of herbicides in soils is determined by their characteristics and water solubility, soil composition, organic matter content, pH, permeability, and water flow. The water-soluble species are easily leached, and the salts of the compounds are more leaching than the esters. Different soils lead to large differences in surface area. Soils with high content of clay and organic matter have a strong adsorption effect on herbicides, making them difficult to apply. Leaching; Conversely, sandy soil and sandy loam permeability, adsorption is poor, it is conducive to leaching. Soil pH mainly affects indirectly the leaching of herbicides by affecting the chemical reaction between adsorption and herbicide and soil components. The leaching of sulfonylurea herbicides in soil increases with the increase of PH value, so it is in alkaline soils. It is easier to leach than acid soil.
Herbicides with strong leaching ability can easily penetrate into the lower layer of the soil profile, which not only reduces the effect of herbicides, but also easily accumulates or contaminates groundwater in the lower layers of the soil. In the use of differential selectivity, due to the leaching of herbicides into the soil where the crop seeds are located, it is likely to cause phytotoxicity. Therefore, it should be based on the herbicide species water solubility and mobility, soil properties and other factors affecting the movement of water, To determine the best is to buy methods and dosage per unit area in order to improve the weeding effect and prevent soil and groundwater contamination.
Fifth, chemical decomposition
Chemical decomposition is one of the important ways herbicides disappear in the soil, including oxidation, reduction, hydrolysis, and formation of insoluble salts and complexes. Sulfonylurea herbicides gradually disappear in acidic soils through hydrolysis. When the content of high-valent metal ions such as Ca2+, Mg2+, Fe2+ in the soil is high, some herbicides can react with these ions to form insoluble salts; some herbicides form with cobalt, copper, iron, magnesium, and nickel in the soil. Stable complexes remain in the soil.
VI. Biodegradation
Biodegradation of herbicides includes degradation of the soil by microorganisms and degradation in the body after absorption by plants.
Microbial degradation is the most important way that most herbicides disappear in the soil. Fungi, bacteria and actinomycetes participate in the degradation. Under the action of microorganisms, the molecular structure of the herbicide is subjected to dehalogenation, dealkylation, hydrolysis, oxidation, cyclohydroxylation and cleavage, nitro reduction, condensation, and formation of conjugates, and the herbicide activity is lost through these reactions.
Soil moisture, temperature, pH, organic matter content, etc. significantly affect the microbial degradation of herbicides, and the appropriate high temperature and soil moisture promote degradation.
In different regions, it is necessary to deepen the speed and half-life of herbicides in order to rationally use and properly arrange the crops.
Herbicides that are absorbed by crops and weeds disappear through a series of biological metabolism including oxidation, reduction, hydrolysis, dehalogenation, substitution, oximation, cyclization, isomerization, ring cleavage, and combinations. The main reflection is oxidation, reduction, hydrolysis and binding.
Medical Cold Patch
Patch for diarrhea
[Name] Medical Cold Patch
[Package Dimension] 5cm 4pieces/box
The pain relief patch is composed of three layers, namely, backing lining, middle gel and protective film. It is free from pharmacological, immunological or metabolic ingredients.
[Scope of Application] For cold physiotherapy, closed soft tissue only.
[Indications]
The patches give a fast relief for diarrhea.
[How To Use a Patch]
Please follow the Schematic Diagram. One piece, one time.
The curing effect of each piece can last for 6-8 hours.
[Attention]
Do not apply the patch on the problematic skin, such as wounds, eczema, dermatitis,or in the eyes. People allergic to herbs and the pregnant are advised not to use the medication. If swelling or irritation occurs, please stop using and if any of these effects persist or worsen.notify your doctor or pharmacist promptly. Children using the patch must be supervised by adults.
[Storage Conditions]
Store below 30c in a dry place away from heat and direct sunlight.
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