A foliar barrier agent for treating heavy metal mercury and its preparation method and application

Abstract

The present invention provides a foliar barrier control agent for treating heavy metal mercury, and a preparation method and application thereof, and relates to the technical field of foliar barrier control agents. The foliar barrier control agent includes the following components in mass percentage: 50% to 70% of a modified sulfide mineral nano-scale dispersion; 5% to 10% of a silicone anti-transpiration agent; 1% to 5% of a surfactant; and the rest is distilled water. The preparation of the modified sulfide mineral nano-scale dispersion is as follows: a modified mixed solution consisting of an organic selenium extract and a DMSA dispersion in a volume ratio of 1:1 is prepared; after the sulfide mineral particles and the modified mixed solution are mixed and modified, centrifugal separation is performed to obtain modified sulfide mineral particles, after washing and drying, anhydrous ethanol is added to ball mill to obtain a modified sulfide mineral slurry, and then ultrasonic dispersion is performed in anhydrous ethanol to obtain the modified sulfide mineral slurry. The foliar barrier control agent of the present invention can effectively curb the migration and transformation of mercury in the plant body by accurately allocating the components and proportions, and has the characteristics of good mercury blocking effect, strong stability and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of crop foliar barrier control agents, and in particular to a foliar barrier control agent for treating heavy metal mercury, and a preparation method and application thereof. Background Art

[0002] One of the main factors of soil environmental damage is heavy metal pollution, among which mercury is one of the most toxic heavy metal pollutants. Since industrialization, humans have mined and used mercury on a large scale, and the application of mercury-containing pesticides and fertilizers has led to large amounts of mercury being discharged into the environment. Soil mercury pollution has different effects on vegetation. Mercury in the soil surface poses a serious threat to the ecological environment and human health through the plant-soil-air system, and has been listed as a priority pollutant by many organizations around the world.

[0003] Exogenous addition of chemical passivators can reduce the bioavailability of soil mercury and the accumulation of mercury in crops. It is currently one of the main methods for the safe use of farmland with low or medium mercury pollution to ensure sustainable agricultural production. However, soil application technology based on traditional barrier control principles has limitations in barrier control effect, stability, environmental friendliness, cost control, etc. At the same time, it is also restricted by the multi-source characteristics of plant mercury (soil and atmospheric sources). In areas of atmospheric mercury pollution, compared with root absorption, the absorption, transportation and accumulation of atmospheric gaseous mercury by leaves become the main source of inorganic mercury in plants. As a result, the restoration method based on soil control pathway cannot reduce the mercury absorbed by leaves from the atmosphere, which limits the effectiveness of farmland mercury pollution control and makes it difficult to support the needs of safe production in mercury-polluted agricultural systems, resulting in a bottleneck in the restoration of mercury-polluted farmland systems.

[0004] Therefore, foliar barrier agents for controlling mercury pollution have emerged. For example, the existing Chinese patent document CN118525857A discloses a mercapto foliar barrier agent for reducing the mercury content in rice. The raw materials of the mercapto foliar barrier agent include γ-mercaptopropyltrimethoxysilane, solvent, water, citric acid, sodium selenate, sodium silicate and Tween 20. The γ-mercaptopropyltrimethoxysilane and sodium selenate in this scheme restrict the entry of atmospheric mercury into rice leaves through stomata and the migration from leaves to grains through efficient complexation, which can effectively reduce the total mercury content in rice. CN112335676A discloses a foliar barrier agent for reducing the heavy metal content of rice. The preparation method of the foliar barrier agent comprises: grinding and sieving diatomaceous earth to obtain diatomaceous earth powder; mixing potassium hydroxide aqueous solution and diatomaceous earth powder according to a volume weight ratio and stirring evenly to obtain a silicon-potassium mixed slurry; subjecting the silicon-potassium mixed slurry to low-temperature plasma irradiation to obtain an activated silicon-potassium mixed slurry; mixing humus soil with the activated silicon-potassium mixed slurry according to a weight ratio and stirring evenly to obtain a silicon-potassium organic mixed slurry; subjecting the silicon-potassium organic mixed slurry to low-temperature plasma irradiation to obtain a silicon-potassium-based barrier control alkali slurry; first mixing citric acid weighed according to a weight ratio with the silicon-potassium-based barrier control alkali slurry, and then performing solid-liquid separation to obtain a foliar barrier agent capable of reducing the heavy metal content of rice; the foliar barrier agent can promote rice growth and reduce rice's adsorption of harmful heavy metal elements such as mercury and cadmium in the soil.

[0005] However, due to the unique biogeochemical characteristics of mercury, such as its multi-source nature, its ability to be methylated to more toxic methylmercury, and its different enrichment mechanism from other heavy metals, the existing foliar spraying agents are not very effective in controlling mercury. Therefore, it is urgent to develop an efficient and environmentally friendly mercury-blocking foliar spray. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in view of the problems existing in the prior art, a foliar barrier agent for treating heavy metal mercury and a preparation method and application thereof are provided.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A leaf surface control agent for treating heavy metal mercury, comprising the following components in percentage by mass:

[0009] Modified sulfide mineral nano-scale dispersion 50% to 70%;

[0010] Silicone anti-transpiration agent 5% to 10%;

[0011] Surfactant 1% to 5%;

[0012] The rest is distilled water;

[0013] The modified sulfide mineral nano-scale dispersion is prepared by the following method:

[0014] S1. preparing a modified mixed solution consisting of an organic selenium extract and a DMSA dispersion; the volume ratio of the organic selenium extract to the DMSA dispersion is 1:1;

[0015] S2. After the sulfide mineral particles are mixed and modified with the modified mixed solution of S1, the modified sulfide mineral particles are separated by centrifugation. After washing and drying, anhydrous ethanol is added for ball milling to obtain a modified sulfide mineral slurry. The modified sulfide mineral slurry is placed in anhydrous ethanol for ultrasonic dispersion to obtain a modified sulfide mineral nano-scale dispersion.

[0016] Furthermore, the organic selenium extract in S1 is prepared by the following method:

[0017] Drying the above-ground part of the vegetable astragalus, crushing, sieving and defatting the above-ground part to obtain defatted vegetable astragalus powder;

[0018] Add sodium hydroxide solution to defatted vegetable astragalus powder, extract with stirring at room temperature for 2-3 hours, centrifuge and separate, and take the supernatant to obtain the product.

[0019] Preferably, the Chinese astragalus is dried at 90-100°C and sieved through a 100-mesh sieve after being crushed.

[0020] Preferably, ethyl acetate is used for degreasing in the above method.

[0021] Preferably, a sodium hydroxide solution with a molar concentration of 0.1 mol / L is added at a solid-liquid ratio of 1 g:30 mL for extraction at room temperature.

[0022] Further, the DMSA dispersion in S1 is prepared by the following method:

[0023] DMSA (sodium dimethyldithiocarbamate) is dissolved in the first solvent, and ultrasonic dispersion is performed at 400-600 kHz for 0.5-1 hour. After the DMSA is completely dissolved, the volume is fixed to a predetermined concentration with a phosphate buffer.

[0024] Preferably, the solid-liquid ratio of DMSA to the first solvent is 1 g:500 mL.

[0025] Furthermore, the first solvent is dimethyl sulfoxide, methanol, ethanol, phosphate buffer or water, preferably dimethyl sulfoxide.

[0026] Preferably, the sulfide mineral in S2 is pyrite.

[0027] Further, S2 includes the following steps:

[0028] (1) soaking pyrite in dilute hydrochloric acid to remove impurities and oxides, washing and drying, ball milling, and vibrating screening to obtain pyrite particles with uniform particle size;

[0029] (2) mixing the treated pyrite particles and the modified mixed solution at a solid-liquid ratio of 1 g:30 mL, stirring magnetically to allow for sufficient reaction, and centrifuging to obtain modified pyrite particles;

[0030] (3) washing repeatedly with deionized water to remove residual solution and impurities on the surface of the modified pyrite particles, and after drying, adding anhydrous ethanol to the treated modified pyrite particles at a solid-liquid ratio of 1 g:1 mL for ball milling to obtain a modified pyrite slurry;

[0031] (4) The modified pyrite slurry is placed in anhydrous ethanol and ultrasonically dispersed at 300-500 kHz for 30-60 minutes to obtain a modified sulfide mineral nano-scale dispersion, preferably at 500 kHz for 30 minutes.

[0032] Furthermore, the concentration of the dilute hydrochloric acid in step (1) is preferably 1.0 mol / L. Generally, the impurities and oxides on the surface of the pyrite are removed by soaking for 0.5 to 1 hour.

[0033] Furthermore, the particle size of the pyrite particles is 50 to 80 microns.

[0034] Furthermore, the magnetic stirring reaction conditions in step (2) are: 60-80° C. and normal pressure for 2-4 hours, preferably 80° C. and normal pressure for 4 hours.

[0035] Furthermore, the ball milling slurry in step (3) is carried out in a zirconia ball mill, and the ball-to-material ratio of zirconia balls to modified pyrite particles is 10:1.

[0036] Preferably, the zirconia balls include an equal number of two types of zirconia balls having diameters of 3 mm and 8 mm.

[0037] Furthermore, in step (3), the ball milling speed is 400-450 r / min, and the ball milling activation is performed for 20-24 h, preferably 450 r / min, and the ball milling activation is performed for 24 h.

[0038] Furthermore, the surfactant is Tween 80, also known as polysorbate 80, which is a non-ionic surfactant.

[0039] Furthermore, the silicone anti-transpiration agent adopts a polyether modified silicone defoaming agent.

[0040] In a second aspect, the present invention also provides a method for preparing the above-mentioned foliar barrier agent for treating heavy metal mercury, comprising the following steps:

[0041] A1. Weigh corresponding weights of modified sulfide mineral nano-scale dispersion, silicone anti-transpiration agent, surfactant and distilled water according to the mass percentages;

[0042] A2. Add modified sulfide mineral nano-scale dispersion, silicone anti-transpiration agent and surfactant into distilled water, stir and mix thoroughly, and after the mixed solution after the reaction returns to room temperature, the foliar barrier control agent is obtained.

[0043] Furthermore, the preparation method also includes filling the mixed liquid prepared by A2, and then packaging it according to product requirements.

[0044] In a third aspect, the present invention also provides the use of the above-mentioned foliar barrier agent or the foliar barrier agent prepared by the above-mentioned preparation method in the treatment of heavy metal mercury.

[0045] The mechanism of action and beneficial effects of the main ingredients in the present invention are as follows:

[0046] Sulfide minerals, such as pyrite (FeS2) in the present invention, are high-iron and high-sulfur minerals with good reducing power. They are widely used as electron donors and play an important role in pollutant removal. Since mercury has a strong affinity with sulfide elements, sulfide substances can fix mercury and convert it into mercuric sulfide. Metal sulfides have excellent mercury removal efficiency because their surfaces are enriched with a variety of chemical groups that can spontaneously react with mercury under low temperature conditions (such as surface monomeric sulfur, polysulfide chains, metal active sites, etc.). Natural iron sulfide has a strong affinity for Hg 0 It has a strong affinity and can convert Hg into stable HgS. In addition, natural metal sulfide ores are rich in sulfur sites and metal sites and can be used as potential cheap mercury removal materials.

[0047] However, natural iron sulfides generally have a dense structure, small specific surface area, and large particle size, which results in limited active sites exposed on the surface that can react with mercury; on the other hand, the crystal structure of natural minerals is highly stable and highly reactive, showing high resistance to external elements and not prone to chemical changes. Therefore, in order to overcome the challenges brought by the physical properties of the surface and the stability of the crystal structure of natural minerals, natural iron sulfides must be modified.

[0048] In the scheme of the present invention, pyrite is modified by forming a modified mixed solution with an organic selenium extract and a DMSA dispersion, and a modified sulfide mineral nano-scale dispersion is first prepared. Among them, the organic selenium extract is rich in selenium, which can enhance the complexation of inorganic mercury ions by cysteine ​​in the plant body and reduce its transport into the grain. DMSA is an organic heavy metal chelating agent containing a dithiol group, which can combine with heavy metal ions in the plant body to form a stable water-soluble chelate. At the same time, because it contains a dithiol group, it can combine with the thiol groups in plant cells damaged by heavy metal ions, restore the activity of enzymes containing thiol groups, and reduce the toxic effects of heavy metal ions.

[0049] The addition of modified mineral nanoparticles in the foliar barrier component provided by the present invention can further lock and fix the mercury element with its high specific surface area and strong adsorption, forming nano-mercury sulfide in the leaves. Due to the low mobility and bioavailability of nano-mercury sulfide, the transfer of mercury between body tissues can be reduced, thereby ensuring that plants are protected from mercury damage and ensuring the safety of agricultural products.

[0050] The silicone anti-transpiration agent of the present invention is a kind of film-type anti-transpiration agent, which can effectively reduce the transpiration of plants, form a thin film on the surface of leaves or fruits, block stomata and cover the cuticle, and inhibit the transpiration of water by reducing the opening of plant stomata. When sprayed on the leaves of plants, it can reduce the opening of stomata, thereby reducing the exchange rate of mercury between leaves and the atmosphere, enhancing the interception capacity of plant stems and leaves for mercury, and effectively blocking the upward migration of mercury in the plant body.

[0051] In summary, the foliar barrier agent provided by the present invention can effectively inhibit the migration and transformation of mercury in plant bodies by accurately adjusting the ingredients and proportions, and has the characteristics of good mercury barrier effect, strong stability and low cost. The present invention develops corresponding foliar barrier agents for mercury-contaminated farmland, which can provide a solid material foundation for the green development of agriculture, and at the same time can largely ensure the safety of people's food. DETAILED DESCRIPTION

[0052] As used herein:

[0053] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0054] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0055] When a parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges of "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0056] In these examples, parts and percentages are by mass unless otherwise indicated.

[0057] For ease of understanding of the present invention, preferred embodiments of the present invention are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0059] The main raw materials and their sources used in the following examples are as follows:

[0060] Edible sweet vetch: The variety is Min Zi No. 7, which is managed normally under natural conditions and harvested before budding.

[0061] Ethyl acetate: purchased from Wuhan Xinyuhang Chemical Co., Ltd.

[0062] Pyrite: purchased from Lingshou County Chenran Mineral Products Co., Ltd. Density 2350 (g / cm 3 ), sulfur content ≥45%.

[0063] DMSA (sodium dimethyldithiocarbamate): purchased from Nanjing Dongna Biotechnology Co., Ltd.

[0064] Dimethyl sulfoxide (DMSO, ACS grade): purchased from AMRESCO, USA.

[0065] Silicone anti-transpiration agent: polyether modified silicone defoamer, purchased from Guangdong Zhongke Hongtai New Materials Co., Ltd.

[0066] Surfactant: Tween 80, purchased from Xi'an Tianmao Baoding Biological Co., Ltd.

[0067] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0068] Example 1

[0069] This embodiment provides a method for preparing an organic selenium extract, which specifically comprises the following steps:

[0070] The above-ground part of the vegetable astragalus is harvested and air-dried under natural conditions, then dried in an oven at 90°C, crushed, passed through a 100-mesh sieve, and deesterified with ethyl acetate to obtain deesterified vegetable astragalus powder.

[0071] Weigh the deesterified vegetable astragalus powder, add a sodium hydroxide solution with a molar concentration of 0.1 mol / L according to a solid-liquid ratio of 1 g:30 mL, stir and extract at room temperature for 2 h, and centrifuge to obtain an organic selenium extract.

[0072] The contents of total selenium and inorganic selenium in the organic selenium extract were determined with reference to GB5009.93-2017 and DBS42 / 010-2018, and the organic selenium content was the total selenium content minus the inorganic selenium content. It was determined that the total selenium content in the organic selenium extract of Astragalus sinensis obtained in this embodiment was 125 mg / kg, and the content of organic selenium was 110.58 mg / kg. The selenium in Astragalus sinensis was mainly organic selenium, and its content accounted for 88% of the total selenium content.

[0073] Example 2

[0074] This embodiment provides a method for preparing a DMSA dispersion, which specifically comprises the following steps:

[0075] Accurately weigh 2.00 g of DMSA and dissolve it in 100 ml of dimethyl sulfoxide. Set 600 kHz ultrasonic dispersion for 1 hour. After complete dissolution, use phosphate buffer (pH = 7.4) to make the volume to 1 L. The concentration of DMSA reaches 10 mmol / L, and the DMSA dispersion is obtained.

[0076] The phosphate buffer (pH=7.4) in this example is prepared by the following method: 1.36 g of potassium dihydrogen phosphate is added to 79 mL of 0.1 mol / mol sodium hydroxide solution, and diluted to 200 mL with water. The phosphate buffer is used to fix the volume and maintain the pH value of the solution stable.

[0077] Example 3

[0078] The present invention provides a method for preparing a modified sulfide mineral nano-scale dispersion. As a preferred embodiment, the sulfide mineral is pyrite, and the method specifically comprises the following steps:

[0079] (1) The organic selenium extract obtained in Example 1 and the DMSA dispersion obtained in Example 2 were mixed at a volume ratio of 1:1 to obtain a modified mixed solution.

[0080] (2) High-quality pyrite is selected and soaked in 1.0 mol / L dilute hydrochloric acid for 1 h to remove impurities and oxides. After washing and drying, the pyrite is crushed to a particle size of about 50 μm using a high-precision ball mill. The particle size is then screened using a vibrating screen to ensure uniformity of the particle size, thereby obtaining pyrite particles.

[0081] (3) The pyrite particles treated in (2) and the modified mixed solution prepared in (1) were mixed evenly at a solid-liquid ratio of 1 g:30 mL, placed on a magnetic stirrer at 80° C., and reacted at normal pressure for 4 hours; after the reaction was completed, the modified pyrite particles were separated by a centrifuge.

[0082] (4) Use deionized water to wash repeatedly to remove the residual solution and impurities on the surface of the modified pyrite particles. After drying in a vacuum drying oven, add the modified pyrite particles obtained in (3) and anhydrous ethanol into a 50.0 ml zirconia ball mill at a solid-liquid ratio of 1:1 for ball milling to prepare a slurry. The ratio of zirconia balls to modified pyrite particles in the zirconia ball mill is 10:1, and the zirconia balls include the same number of two types of zirconia balls with diameters of 3 mm and 8 mm. Set the ball mill speed to 400-450 r / min, and ball mill activation for 20-24 hours; as a preferred embodiment, the present embodiment sets the ball mill speed to 450 r / min, and ball mill activation for 24 hours to obtain a modified pyrite slurry.

[0083] (5) The modified pyrite slurry obtained in (4) is placed in 300 ml of anhydrous ethanol and ultrasonically dispersed at 500 kHz for 30 minutes to obtain the modified sulfide mineral nano-scale dispersion, which is then sealed for later use.

[0084] Example 4

[0085] This embodiment provides a method for preparing a leaf surface barrier agent, which specifically includes the following steps:

[0086] Weigh the corresponding weights of the components according to the mass percentages in Table 1 below: the modified sulfide mineral nano-scale dispersion prepared in Example 3, a silicone anti-transpiration agent (a polyether-modified silicone defoamer is used in this example), a surfactant (Tween 80 is used in this example), and distilled water.

[0087] Then, the modified sulfide mineral nano-scale dispersion, silicone anti-transpiration agent and surfactant are added into distilled water respectively, and the mixture is fully stirred and evenly mixed. After the mixed solution after the reaction returns to room temperature, the foliar barrier control agent is obtained.

[0088] The mixed liquid can then be filled and packaged according to product requirements.

[0089] Example 5

[0090] The proportions of the components of the foliar barrier agent provided in Example 5 are shown in Table 1, and the preparation method is similar to that in Example 4.

[0091] Example 6

[0092] The proportions of the components of the foliar barrier agent provided in Example 6 are shown in Table 1, and the preparation method is similar to that in Example 4.

[0093] Comparative Example 1

[0094] The difference between the foliar barrier agent of this comparative example 1 and that of Example 4 is that the foliar barrier agent component uses an unmodified pyrite dispersion, and the unmodified pyrite dispersion is prepared by the following method:

[0095] After obtaining pyrite particles according to step (2) of Example 3, an unmodified pyrite dispersion was obtained according to steps (4) and (5) of Example 3.

[0096] The mass percentage of each component of the foliar barrier agent is shown in Table 1, and the preparation method is shown in Example 4.

[0097] Comparative Example 2

[0098] The difference between the foliar barrier agent of this comparative example 2 and that of Example 4 is that the foliar barrier agent uses a DMSA-modified pyrite dispersion, which is prepared by the following method:

[0099] After obtaining pyrite particles according to step (2) of Example 3, add the DMSA dispersion obtained in Example 2 at a solid-liquid ratio of 1 g:30 mL, mix well, place on a magnetic stirrer at 80°C, and keep the reaction at normal pressure for 4 hours; after the reaction is completed, separate the DMSA-modified pyrite by centrifuge. Then refer to steps (4) and (5) of Example 3 to obtain a DMSA-modified pyrite dispersion.

[0100] The mass percentage of each component of the foliar barrier agent is shown in Table 1, and the preparation method is shown in Example 4.

[0101] Comparative Example 3

[0102] The difference between the foliar barrier control agent of this comparative example 3 and that of Example 4 is that the foliar barrier control agent uses a selenium-modified pyrite dispersion, which is prepared by the following method:

[0103] After obtaining pyrite particles according to step (2) of Example 3, the organic selenium extract obtained in Example 1 was added at a solid-liquid ratio of 1 g:30 mL, mixed evenly, and placed on a magnetic stirrer at 80°C and kept at normal pressure for 4 hours; after the reaction was completed, the selenium-modified pyrite was separated by a centrifuge. Referring to steps (4) and (5) of Example 3, a selenium-modified pyrite dispersion was obtained.

[0104] The mass percentage of each component of the foliar barrier agent is shown in Table 1, and the preparation method is shown in Example 4.

[0105] Comparative Example 4

[0106] The difference between Comparative Example 4 and Example 4 is that no silicone anti-transpiration agent is added to the leaf surface barrier agent of this comparative example. The mass percentage of each component is referred to Table 1, and the preparation method is referred to Example 4.

[0107] Table 1 Components and ratios of leaf surface control agents in Examples and Comparative Examples

[0108]

[0109] In order to verify the feasibility and effectiveness of the present invention, the following tests were conducted on the leaf surface control agents prepared in the above embodiments and comparative examples:

[0110] 1. Before the start of the experiment, mixed samples from 6 sampling points in the entire experimental field were taken as the basic soil samples for the experiment. The background value of soil mercury content was determined with reference to GB15618-2018. The test results are shown in Table 2.

[0111] Table 2 Soil pH and mercury and cadmium content

[0112] project pH <![CDATA[Cd / mg·kg -1 ]]> Test soil for Chinese cabbage 4.97±0.51 25.89±0.21 Rice test soil 6.39±0.28 0.17

[0113] 2. Spray the foliar control agents prepared in the above embodiments and comparative examples on Chinese cabbage and rice in groups according to the following method.

[0114] 1. A method for spraying a leaf barrier agent on Chinese cabbage, comprising the following steps:

[0115] Spray on the front and back of the plant leaves (leaf surface is moist but not dripping), and spray the control group with an equal amount of water. Spray for the first time at the seedling stage, take 125ml of the foliar barrier prepared in the above embodiment and comparative example and add 10kg of water, spray four times continuously, each spraying interval is 10 days, harvest the plants one week after the fourth foliar spraying treatment, collect the edible part of the pakchoi, wash, dry at low temperature and grind it to determine its total mercury content, the detection method refers to GB2762-2022.

[0116] 2. A method for spraying a leaf barrier control agent on rice, comprising the following steps:

[0117] (1) During the peak tillering period of rice, 250 ml of the foliar control agent prepared in the above embodiments and comparative examples was diluted with 20 kg of water and sprayed on the leaf surface and back of the rice leaves;

[0118] (2) During the rice heading stage, take 250 ml of the foliar inhibitor and add it to 20 kg of water, then spray it on the rice leaves and back of the leaves.

[0119] When rice is harvested, it is harvested and dried separately in each plot, and the yield is calculated by weighing it separately. In each plot, about 1 kg of agricultural product samples are collected according to the principle of random, diverse and equal amounts to test the mercury content in agricultural products. The collected rice samples are sent to Zhejiang Zhenong Testing and Certification Technology Co., Ltd. for testing. The testing method refers to GB2762-2022. The test results and analysis are as follows:

[0120] 1. Effects of different treatments on mercury content in edible parts of Chinese cabbage

[0121] The test data of the effects of leaf barrier agents in different embodiments and comparative examples on the mercury content in the edible parts of Chinese cabbage are shown in Table 3 below:

[0122] Table 3 Effects of different treatments on mercury content in edible parts of Chinese cabbage

[0123] deal with Mercury content in edible parts (mg / kg) Reduction (%) CK 2.73 - Example 4 0.89 -67.40％ Example 5 1.02 -62.64％ Example 6 1.56 -42.86％ Comparison 1 2.1 -23.08％ Comparison 2 1.79 -34.43％ Contrast 3 1.85 -32.23％ Contrast 4 1.71 -37.36％

[0124] As can be seen from Table 3, there are significant differences in the effects of different treatments on the mercury content in the edible parts of Chinese cabbage. The mercury content in the edible parts of Chinese cabbage in the control group (CK) was 2.73 mg / kg. Compared with the control, the mercury content in the edible parts of Chinese cabbage treated with the foliar barrier agents of Examples 4, 5 and 6 of the present invention was reduced to 0.89 mg / kg, 1.02 mg / kg and 1.56 mg / kg, respectively, with a reduction of 67.40%, 62.64% and 42.86%, respectively. This result clearly shows that the application of the foliar barrier agent prepared by the present invention can significantly reduce the accumulation of mercury in the edible parts of Chinese cabbage. Further analysis found that with the increase in the mass ratio of nano-scale modified pyrite in the foliar barrier agent, its barrier effect on mercury is more obvious. Compared with the embodiments, each component of each comparative example does weaken the barrier effect of the product on the edible parts of Chinese cabbage to varying degrees.

[0125] 2. Effects of different treatments on mercury content in brown rice

[0126] The test data of the effects of foliar barrier agents on the mercury content of brown rice in different embodiments and comparative examples are shown in Table 4 below:

[0127] Table 4 Effects of different treatments on mercury content in brown rice

[0128] deal with Mercury content in edible parts (mg / kg) Reduction (%) CK 0.47 - Example 4 0.17 -64.52％ Example 5 0.19 -60.09％ Example 6 0.21 -55.74％ Comparison 1 0.36 -23.04％ Comparison 2 0.25 -47.04％ Contrast 3 0.28 -41.48％ Contrast 4 0.26 -44.87％

[0129] As can be seen from Table 4, there are significant differences in the effects of different treatments on the mercury content of brown rice. The mercury content in the brown rice grains of the control group (CK) was 0.47 mg / kg. Compared with the control, the mercury content in the brown rice grains treated with the foliar barrier agents of Example 4, Example 5 and Example 6 was reduced to 0.17 mg / kg, 0.19 mg / kg and 0.21 mg / kg, respectively, with a reduction of 64.52%, 60.09% and 55.74%, respectively. This result shows that the application of the foliar barrier agent prepared by the present invention can significantly reduce the accumulation of mercury in rice brown rice grains. Further analysis found that with the increase in the mass ratio of nano-scale modified pyrite in the foliar barrier agent, its barrier effect on mercury is more obvious. Compared with the embodiments, each component of each comparative example does weaken the barrier effect of the product on the edible part of Chinese cabbage to varying degrees.

[0130] The present invention determines the role of each component of the foliar barrier agent through the above-mentioned embodiments and comparative examples, and can adjust the components accordingly according to the actual situation of soil pollution in the subsequent promotion process; and the mercury-inhibiting foliar barrier agent of the present invention achieves the effect of "1+1>2" of each active component on mercury reduction in crops. It shows that the foliar barrier agent provided by the present invention can effectively inhibit the migration and transformation of mercury in the plant body by accurately adjusting the components and proportions, and has the characteristics of good mercury-blocking effect, strong stability and low cost.

[0131] The above descriptions are only some preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A leaf surface control agent for treating heavy metal mercury, characterized in that: The following components are included in mass percentage: Modified sulfide mineral nano-scale dispersion 50% to 70%; Silicone anti-transpiration agent 5% to 10%; Surfactant 1% to 5%; The rest is distilled water; The modified sulfide mineral nano-scale dispersion is prepared by the following method: S1. preparing a modified mixed solution consisting of an organic selenium extract and a DMSA dispersion; the volume ratio of the organic selenium extract to the DMSA dispersion is 1:1; S2. After the sulfide mineral particles are mixed and modified with the modified mixed solution of S1, the modified sulfide mineral particles are separated by centrifugation. After washing and drying, anhydrous ethanol is added for ball milling to obtain a modified sulfide mineral slurry. The modified sulfide mineral slurry is placed in anhydrous ethanol for ultrasonic dispersion to obtain a modified sulfide mineral nano-scale dispersion.

2. The leaf surface control agent for treating heavy metal mercury according to claim 1, characterized in that: The organic selenium extract in S1 is prepared by the following method: The above-ground part of the vegetable astragalus is dried, crushed, sieved, and defatted with ethyl acetate to obtain defatted vegetable astragalus powder; the defatted vegetable astragalus powder is weighed, and a sodium hydroxide solution with a molar concentration of 0.1 mol / L is added according to a solid-liquid ratio of 1 g:30 mL, and the mixture is extracted with stirring at room temperature for 2 to 3 hours, centrifuged, and the supernatant is obtained.

3. The leaf surface control agent for treating heavy metal mercury according to claim 1, characterized in that: The DMSA dispersion in S1 was prepared by the following method: DMSA was dissolved in the first solvent at a solid-liquid ratio of 1 g:500 mL, and ultrasonic dispersion was performed at 400-600 kHz for 0.5-1 h. After complete dissolution, the volume was fixed to a predetermined concentration with a phosphate buffer.

4. The leaf surface barrier agent for treating heavy metal mercury according to claim 3, characterized in that: The first solvent is any one of dimethyl sulfoxide, methanol, ethanol, phosphate buffer or water.

5. The leaf surface control agent for treating heavy metal mercury according to claim 1, characterized in that: The sulfide mineral in S2 is pyrite, and S2 specifically comprises the following steps: (1) soaking pyrite in dilute hydrochloric acid to remove impurities and oxides, washing and drying, ball milling, and vibrating screening to obtain pyrite particles with uniform particle size; (2) The treated pyrite particles and the modified mixed solution in S1 are mixed evenly at a solid-liquid ratio of 1 g:30 mL, reacted at 60-80° C. and normal pressure for 2-4 hours on a magnetic stirrer, and after sufficient reaction, centrifuged to obtain modified pyrite particles; (3) washing repeatedly with deionized water to remove residual solution and impurities on the surface of the modified pyrite particles, and after drying, adding anhydrous ethanol to the treated modified pyrite particles at a solid-liquid ratio of 1 g:1 mL for ball milling to obtain a modified pyrite slurry; (4) The modified pyrite slurry is placed in anhydrous ethanol and ultrasonically dispersed at 300-500 kHz for 30-60 minutes to obtain a modified sulfide mineral nano-scale dispersion.

6. The leaf surface control agent for treating heavy metal mercury according to claim 5, characterized in that: The particle size of the pyrite particles obtained by the treatment is 50 to 80 microns.

7. The leaf surface barrier agent for treating heavy metal mercury according to claim 5, characterized in that: In step (3), the ball milling is carried out in a zirconia ball mill, and the ball-to-material ratio of zirconia balls to modified pyrite particles is 10:1; The zirconia balls include the same number of two types of zirconia balls with diameters of 3 mm and 8 mm; Set the ball mill speed to 400-450 r / min and activate the ball mill for 20-24 hours.

8. The leaf surface barrier agent for treating heavy metal mercury according to claim 1, characterized in that: The surfactant is Tween 80; the silicone anti-transpiration agent is a polyether modified silicone defoamer.

9. A method for preparing the leaf surface barrier agent for treating heavy metal mercury according to any one of claims 1 to 8, characterized in that: The steps include: A1. Weigh corresponding weights of modified sulfide mineral nano-scale dispersion, silicone anti-transpiration agent, surfactant and distilled water according to the mass percentages; A2. Add modified sulfide mineral nano-scale dispersion, silicone anti-transpiration agent and surfactant into distilled water, stir and mix them evenly, and after the mixed solution after the reaction returns to room temperature, the foliar barrier control agent is obtained.

10. Use of the foliar barrier agent according to any one of claims 1 to 8 or the foliar barrier agent prepared by the preparation method according to claim 9 in the treatment of heavy metal mercury.

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