Special heavy metal blocking agent for rice and method for reducing cadmium content of rice grains by using same

Abstract

The invention discloses a heavy metal blocking agent special for rice and a method for reducing the cadmium content of rice grains by using the heavy metal blocking agent, and belongs to the technical field of agricultural environment protection and polluted soil remediation. The heavy metal blocking agent special for rice comprises the following raw materials: 20-30% of molybdenum disulfide, 10-20% of diammonium hydrogen phosphate, 5-10% of disodium magnesium ethylene diamine tetraacetate, 5-10% of zinc ethylene diamine tetraacetate, 10-20% of a silicon fertilizer, 1-2% of a cosolvent, 1-2% of a solubilizer, 1-2% of ethanol and the balance of water. The special heavy metal blocking agent for the rice can effectively inhibit heavy metal cadmium from being transferred into rice grains, obviously reduce the cadmium content of the rice grains, obviously improve the yield of the rice grains, and can obviously reduce the cadmium content in the rice and ensure that the cadmium content in the rice grains meets the national food hygiene standard when being applied to the rice planted in a rice field with soil polluted by cadmium.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural environmental protection and contaminated soil remediation, and in particular to a special heavy metal barrier for rice and a method for reducing the cadmium content in rice grains by utilizing the same. Background Art

[0002] Cadmium, a highly toxic and mobile metal, is easily converted into nutrient residues and ultimately enters the food chain. Cadmium concentrations can increase through trophic levels through biomagnification. Cadmium contamination of cultivated land can lead to excessive cadmium levels in agricultural products. As a key food crop, rice's cadmium contamination is particularly important to consumers. Therefore, research on technologies to control heavy metal contamination in rice is of vital importance.

[0003] Current remediation and control technologies for heavy metals in rice paddies primarily include passivation and foliar fertilizers. Passivation is one of the most widely used measures for remediating heavy metal contamination in rice paddies. Currently, passivation materials primarily include quicklime, biochar, sepiolite, calcium magnesium phosphate fertilizers, and organic amendments. Effective passivation of heavy metals in soil generally requires large application rates, significantly impacting soil structure and physical and chemical properties, potentially leading to a decline in arable land quality and significantly impacting farmers' incomes. Foliar fertilizer control involves applying fertilizer directly to the leaves of plants like rice. It is currently a well-established method for controlling heavy metal uptake by rice. Foliar fertilizers primarily include foliar application of silicon (Si), selenium (Se), and iron (Fe) fertilizers, or spraying humic acid fertilizers and chitosan. Foliar fertilizers not only increase rice yields but also effectively reduce heavy metal uptake, making them a cost-effective control technology.

[0004] In recent years, research on foliar barrier agents that can inhibit or block the absorption of heavy metals by crops has received widespread attention in the field of heavy metal barrier remediation in cultivated land. Chinese patent application publication number CN105851002A discloses a rice heavy metal absorption barrier agent and its use method, and Chinese patent application publication numbers CN110150319A and CN105815313A both disclose a vegetable heavy metal barrier agent and its use method. Based on these published patents, foliar barrier agents have a good effect on reducing the absorption and accumulation of Cd by crops. However, there is currently no foliar barrier agent specifically for rice grains that can effectively block the absorption of heavy metal Cd by rice grains and have a yield-increasing effect on rice. Summary of the Invention

[0005] The present invention aims to provide a heavy metal barrier for rice and a method for reducing the cadmium content in rice grains using the same, thereby addressing the aforementioned problems in the prior art. The present invention not only significantly reduces the cadmium content in rice but also has nutritional benefits, effectively increasing rice yield.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is the use of molybdenum disulfide in the preparation of a foliar barrier for inhibiting the absorption of heavy metal cadmium by rice grains.

[0008] Furthermore, the particle size of the molybdenum disulfide is ≤100 nm.

[0009] The inventors have found that using molybdenum disulfide to prepare a foliar barrier that inhibits the absorption of heavy metal cadmium by rice grains can effectively reduce the cadmium content in rice grains and increase rice yield. The inventors have analyzed that the mechanism by which nano-scale molybdenum disulfide reduces the cadmium content in rice is as follows: 1) Nano-MoS2 penetrates into cells through the stomata or epidermis of leaves, migrates through the vascular bundles to the roots, and induces the plant to synthesize glutathione (GSH) and phytochelatins (PCs), which react with Cd. 2+ Forming a stable complex, inhibiting the transport of Cd to the grain. 2) Nano-MoS2 has sulfur vacancies, which can adsorb Cd through sulfur vacancies. 2+ 3) Nano-MoS2 directly removes Cd-induced reactive oxygen species (ROS) in leaves, maintains cell membrane integrity, and reduces the passive transport of Cd from roots to aerial parts.

[0010] The mechanism by which nano-sized molybdenum disulfide increases rice yield is as follows: 1) Nano-MoS2 is rapidly absorbed through fissures in the leaf cuticle and slowly releases Mo ions in the acidic intracellular environment, acting as a cofactor for nitrate reductase (NR) and aldehyde oxidase (AO), improving nitrogen assimilation efficiency and promoting protein synthesis and panicle differentiation. 2) It reduces Cd damage to chloroplast thylakoid membranes, increasing enzyme activity and photochemical efficiency, and extending the photosynthetic cycle of functional leaves. 3) It enhances sucrose synthase activity in leaves, accelerating the transport of photosynthetic products to grains, significantly increasing thousand-grain weight and seed set.

[0011] The inventors also discovered that nano-molybdenum disulfide has unparalleled advantages over other molybdenum fertilizers: 1) Traditional foliar molybdenum fertilizers, with large molecules difficult to penetrate and an absorption rate of less than 30%, can penetrate the cuticle, achieving an absorption rate of over 75%. 2) Traditional foliar molybdenum fertilizers only provide molybdenum nutrients and lack Cd control. Nano-molybdenum disulfide, after leaf absorption, systematically regulates Cd transport and simultaneously provides molybdenum for increased yields. 3) Traditional foliar molybdenum fertilizers can produce excessive molybdate ions, leading to leaf burns.

[0012] The second technical solution of the present invention: A heavy metal barrier specially used for rice, comprising the following raw materials, calculated by mass percentage: 20%-30% molybdenum disulfide, 10%-20% diammonium hydrogen phosphate, 5%-10% disodium magnesium ethylenediaminetetraacetate, 5%-10% zinc ethylenediaminetetraacetate, 10%-20% silicon fertilizer, 1%-2% cosolvent, 1%-2% solubilizer, 1%-2% ethanol, and the balance water.

[0013] The synergistic effect of the above components can significantly reduce the cadmium content in rice grains and increase rice yield. The specific mechanism is as follows:

[0014] 1. Synergistic cadmium reduction mechanism:

[0015] Nano-sized MoS2 as a core functional component can induce rice to synthesize GSH and PCs to adsorb Cd 2+ To inhibit the transport of Cd to grains and adsorb Cd through sulfur vacancies 2+ And by removing ROS, it maintains the integrity of the cell membrane to reduce the passive transport of Cd from the root system to the aboveground part. After being absorbed by the rice leaves, silicon fertilizer can reduce the transport of Cd to the grain through cell wall Cd fixation, vacuolar compartmentalization and transport gene inhibition, thereby reducing the Cd content in the edible part. The EDTA ligand in magnesium disodium ethylenediaminetetraacetate (Mg-EDTA) and zinc ethylenediaminetetraacetate (Zn-EDTA) preferentially binds free Cd through strong complexation. 2+ , forming a stable Cd-EDTA complex to block the 2+ Calcium ions (Ca 2+ ) channels, thereby inhibiting the absorption of Cd. Moreover, EDTA chelators (Mg-EDTA and Zn-EDTA) can penetrate into the stomata and capture the adsorbed Cd in the intercellular space. 2+ After entering the vascular bundle, the formed Cd-EDTA complex cannot be transported to the grain through the phloem sieve tube due to its large molecular weight (>500Da). In addition, inside the cell, the Zn provided by Zn-EDTA 2+ By competitively inhibiting the expression of Cd transporters (such as OsNramp5), the diffusion of Cd out of the vacuole is reduced, and the Mg provided by Mg-EDTA 2+ By activating the tonoplast transporter OsHMA3, it promotes the storage of Cd in the vacuole, ultimately reducing Cd content in the grain. Diammonium hydrogen phosphate (DAP) provides nitrogen and phosphorus nutrients, promotes adenosine triphosphate (ATP) synthesis, regulates cellular pH, enhances the dispersion stability of MoS2 and EDTA components, and strengthens rice's tolerance to Cd through energy supply. These components work synergistically to effectively reduce cadmium content in rice grains.

[0016] 2. Production increase mechanism:

[0017] Molybdenum provided by molybdenum disulfide significantly improves nitrogen assimilation efficiency through the activation of nitrate reductase (NR) and aldehyde oxidase (AO), promoting protein synthesis and tillering growth. Silicon fertilizers provide silicon, which increases the number of effective panicles by upregulating the auxin synthesis gene (OsYUCCA1) and enhances leaf uprightness to optimize light energy capture. Zinc provided by Zn-EDTA acts as a cofactor for carbonic anhydrase (CA), accelerating the transport of CO2 to chloroplasts. It synergizes with phosphorus provided by DAP to increase the maximum photochemical efficiency (Fv / Fm) of photosystem II (PSII), significantly increasing the photosynthetic rate. Furthermore, magnesium provided by Mg-EDTA is a core element of the chlorophyll molecule. Its stable supply can delay leaf senescence, prolong the photosynthetic cycle, and significantly increase thousand-grain weight and grain plumpness. These elements work synergistically to effectively increase rice yield.

[0018] In addition, magnesium disodium ethylenediaminetetraacetate (Mg-EDTA) and zinc ethylenediaminetetraacetate (Zn-EDTA) as chelated micronutrient fertilizers have significant advantages over common foliar fertilizers such as magnesium sulfate and zinc sulfate:

[0019] (1) Absorption efficiency and mobility: EDTA chelate has a small molecular weight (about 300Da) and can directly penetrate into cells through the lipid channels of the leaf cuticle, with an absorption rate of more than 85%. Ordinary magnesium and zinc fertilizers are in ionic form (Mg 2+ 、Zn 2+ ) are easily electrostatically repelled by the epidermal wax layer, resulting in an absorption rate of less than 25%. Once inside the plant, EDTA chelates can be transported bidirectionally through the symplast and apoplast pathways, rapidly reaching the root system or growing points. However, ionic nutrients are easily fixed by the cell wall, leading to localized accumulation and leaf burns.

[0020] (2) Heavy metal blocking ability: EDTA ligand for Cd 2+ The complexing ability (logK=16.5) is much higher than that of Mg 2+ (logK=8.7) and Zn 2+ (logK=16.1), can preferentially chelate Cd 2+ And reduce its bioavailability; ordinary magnesium and zinc fertilizers do not have this function, and sulfate may increase the solubility of Cd in the soil.

[0021] (3) Chemical stability and environmental friendliness: EDTA chelates are stable over a wide pH range (3-9), avoiding precipitation with phosphates or carbonates on the leaf surface. Conventional magnesium and zinc fertilizers, on the other hand, tend to form hydroxides that clog stomata under alkaline conditions. Furthermore, EDTA can be degraded into harmless products by soil microorganisms, while excessive sulfate application can lead to soil acidification and increase the risk of Cd activation.

[0022] Furthermore, the particle size of the molybdenum disulfide is ≤100 nm.

[0023] Furthermore, the purity of the molybdenum disulfide is ≥99%.

[0024] Furthermore, the silicon fertilizer includes nano-silicon dioxide, sodium metasilicate or nano-elemental silicon.

[0025] In addition to providing silicon, nano-silicon dioxide and nano-elemental silicon also form a physical barrier on the leaf surface in the form of nanoparticles. Their high surface area adsorbs Cd, reducing passive Cd absorption by stomata. Together with MoS2, they enhance the mechanical strength of the leaves. Furthermore, nano-elemental silicon is highly inert and has a low risk of environmental residues. Sodium metasilicate rapidly releases silicate, promoting cell wall thickening and tillering.

[0026] Furthermore, the cosolvent includes sodium benzoate, sodium salicylate, urea or acetamide.

[0027] Urea can provide an alkaline environment to promote the dispersion of MoS2 and other substances, and also serve as a foliar nitrogen source; sodium salicylate can enhance the stability of the solution and has a disease-resistant inducing effect; acetamide has low toxicity and good compatibility with EDTA chelating agents; sodium benzoate can improve the dispersion stability of nano-MoS2 in water and inhibit the growth of microorganisms in heavy metal barrier agents.

[0028] Furthermore, the solubilizing agent includes cresol soap or Tween 80.

[0029] Tween 80 is a low-foaming solubilizer suitable for use with nanoparticles; cresol soap has strong permeability and is suitable for rapid absorption during the booting period.

[0030] The third technical solution of the present invention is a method for preparing the above-mentioned heavy metal barrier for rice, comprising the following steps:

[0031] The raw materials are weighed according to mass percentage and mixed evenly to obtain the special heavy metal barrier for rice.

[0032] Technical solution 4 of the present invention: A method for reducing the cadmium content in rice grains, spraying the above-mentioned rice-specific heavy metal barrier agent on rice fields contaminated with heavy metal cadmium at two or three stages of the rice tillering stage, booting stage and filling stage.

[0033] The reasons for spraying during the tillering, booting or grain filling stages of rice are as follows:

[0034] 1. Spraying during the tillering stage: blocking early cadmium absorption and promoting tillering

[0035] The tillering stage is a critical phase in rice growth, when the root system rapidly expands and begins to absorb cadmium from the soil. Foliar spraying of heavy metal blockers can work through the following mechanisms:

[0036] Matching physiological needs: During the tillering period, rice's demand for nitrogen, phosphorus, magnesium and other elements surges. The synergistic effect of DAP and Mg-EDTA can enhance the differentiation of tiller primordia and increase the number of effective tillers.

[0037] Cadmium control window period: At this stage, the cadmium absorbed by the roots has not yet been transported to the aboveground parts in large quantities. The GSH synthesis induced by nano-MoS2 can form a "cadmium interception zone" at the base of the stem in advance, reducing the potential for subsequent migration to the panicle.

[0038] Adaptability of leaf development: The cuticle of new leaves is thinner (about 0.8 μm), nanoparticles can penetrate more easily, and the absorption efficiency is higher than that of mature leaves.

[0039] 2. Spraying during the booting stage: inhibiting the accumulation of cadmium in the ears

[0040] The booting stage is the initial stage of rice reproductive growth, and young panicle differentiation is extremely sensitive to cadmium (cadmium stress can significantly increase the spikelet abortion rate). The core advantages of spraying at this time include:

[0041] Vascular transport blockage: The development of young panicles depends on the nutrient transport of the stem vascular bundle. EDTA chelates competitively bind to Cd 2+ , forming a Cd-EDTA complex with a molecular weight of >500Da, which prevents it from passing through the phloem sieve tube (pore size limit <400Da) and entering the panicle.

[0042] Gene expression regulation window: The expression level of the OsLCT1 gene (which controls grain cadmium transport) in rice during the booting stage rises to a peak, and nano-MoS2 can specifically inhibit the activity of this gene by inducing methylation modification.

[0043] Photosynthetic enhancement requirements: The formation of young ears requires a large amount of photosynthetic products. Silicon, Mg and Zn work together to increase the photosynthetic rate of leaves and ensure the number of grains per ear.

[0044] 3. Spraying during the grain filling period: blocking cadmium in grains and consolidating yield

[0045] The grain filling period is the core stage of cadmium migration to grains. Spraying at this time can achieve:

[0046] Phloem re-interception: During the grain filling period, cadmium is mainly transported from stems and leaves to grains through the phloem. Nano-MoS2 is enriched in the leaf sheath and secondary adsorbs free Cd through sulfur vacancies. 2+ , reducing the probability of it entering the sieve tube.

[0047] Grain protection barrier: Nano components form a nano layer on the surface of the husk, blocking the direct attachment of cadmium deposited from the atmosphere.

[0048] Furthermore, the application amount of the heavy metal barrier agent is 100mL-200mL / mu each time.

[0049] Furthermore, the heavy metal barrier agent is diluted with water to a concentration of molybdenum disulfide component of 0.1g / L-0.25g / L before spraying (i.e., the heavy metal barrier agent is diluted with water to a heavy metal barrier agent solution with a concentration of molybdenum disulfide component of 0.1g / L-0.25g / L before spraying).

[0050] Furthermore, the soil pH value of the paddy field contaminated by heavy metal cadmium is less than 7.5.

[0051] Furthermore, the spraying is specifically to spray the diluted heavy metal barrier agent solution on the rice leaves in a spraying form.

[0052] Furthermore, avoid spraying during periods of strong midday sunlight.

[0053] The heavy metal barrier of the present invention is a rice-specific heavy metal barrier, specifically designed for rice and tailored to the physiological characteristics of rice. The specific design basis for the heavy metal barrier of the present invention for rice is as follows:

[0054] 1. Adaptation of rice leaf structure and absorption characteristics

[0055] As a monocot, rice has leaves with parallel veins, a thin cuticle, and dense stomata (the density of stomata is about 200-300 / mm 2 The nano-MoS2 in the present invention can effectively penetrate through the stomata (pore size of about 5-20 μm) or epidermal cracks of rice leaves, while the cuticle of dicotyledonous plants (such as soybeans and spinach) is thicker (2-5 μm) and the stomatal density is low (about 50-150 / mm). 2 ), resulting in a decrease in the absorption efficiency of nanoparticles. Furthermore, silicon can induce the formation of a silicified cell layer in rice leaves, strengthening the physical barrier function. Rice's silicon absorption capacity (10% of its total dry weight) is significantly higher than that of other crops (e.g., corn, which only absorbs 1%), further amplifying its cadmium-blocking effect.

[0056] 2. Specific responses of rice cadmium transport genes

[0057] The accumulation of cadmium in rice is highly dependent on the expression of OsNramp5 (root uptake) and OsLCT1 (grain transport). 2+ The affinity of Zn 2+ with cd 2+ The ion radius is similar), and the GSH synthesis induced by nano-MoS2 can specifically downregulate the expression of OsLCT1. This dual regulatory mechanism is effective in rice. Compared with crops such as wheat, its cadmium transport genes (such as TaNramp5) are sensitive to Zn 2+The sensitivity of OsHMA3 is low and it lacks the vacuolar compartmentalization reinforcement mechanism similar to OsHMA3, resulting in a decrease in the Cd control efficiency of grains under the same scheme.

[0058] 3. Matching the rice growth environment with its nutrient requirements

[0059] Rice is in a flooded anaerobic environment for a long time, and Cd in the soil is more easily absorbed by Cd 2+ The present invention avoids the complex Cd activation process in the rice rhizosphere by spraying on the leaves, and directly blocks the migration of Cd to the aboveground part. At the same time, the ammonium nitrogen (NH4 + ) is more in line with the nitrogen source form that rice prefers to absorb. Rice preferentially absorbs NH4 under flooding conditions. + The ammonium nitrogen provided by DAP can avoid the risk of Cd activation caused by nitrate nitrogen fertilizers (such as calcium nitrate), while molybdenum (Mo) as a cofactor of nitrate reductase can synergistically improve the nitrogen use efficiency of rice under flooding conditions, which has limited effect in dryland crops (such as corn).

[0060] 4. Adaptation of rice metabolic system and enzyme system

[0061] Rice has a high demand for sulfur, and the S released after the decomposition of MoS2 2- It can participate in the synthesis of cysteine ​​and enhance the synthesis of chelating peptides (PCs), but crops with low sulfur requirements cannot fully utilize this pathway.

[0062] Aldehyde oxidase (AO) in rice photorespiration pathway 2+ is highly dependent on Mg, while RuBisCO activating enzyme requires Mg 2+ Participation, the EDTA chelated form can accurately match its enzyme activity regulation needs.

[0063] In addition, the present invention also proves through experiments that the same heavy metal barrier has different heavy metal barrier effects on different plants, that is, different plants require different heavy metal barrier agents, further proving the specificity of the heavy metal barrier of the present invention to rice.

[0064] The present invention discloses the following technical effects:

[0065] (1) The present invention provides a new application of molybdenum disulfide. There have been no previous reports on spraying molybdenum disulfide on the leaves to reduce the heavy metal cadmium content in rice grains. The present invention uses a rice-specific heavy metal barrier containing molybdenum disulfide to spray on the rice leaves to reduce the cadmium content in the grains. The operation is simple and will not cause secondary pollution to the soil, air and irrigation water, providing a good solution to the problem of cadmium pollution in rice grains.

[0066] (2) The present invention provides a rice-specific heavy metal barrier that can effectively inhibit the transport of heavy metal cadmium into rice grains, significantly reduce the cadmium content in rice grains, and significantly increase its yield. When applied to rice planted in rice fields with cadmium-contaminated soil, the cadmium content in rice can be significantly reduced, ensuring that the cadmium content in rice grains meets national food hygiene standards.

[0067] (3) The rice-specific heavy metal barrier provided by the present invention has a strong specificity in inhibiting the absorption of heavy metal cadmium by rice grains, and can effectively and significantly block the absorption of heavy metal cadmium by rice grains. It can be applied to rice fields with moderately to lightly cadmium-contaminated soil to alleviate the toxic effects of heavy metal cadmium on rice grains. It is sprayed during the period of vigorous growth and development of rice, such as the tillering stage and the heading stage. According to the experimental data of two years of continuous field trials, the cadmium content in rice grains can be reduced by 36.9%-46.8% compared with the control, and the rice yield can be increased by 8.0%-17.3% compared with the control.

[0068] (4) The raw materials of the heavy metal barrier agent for rice provided by the present invention are green and environmentally friendly, and can effectively block the absorption and accumulation of heavy metal cadmium by rice, effectively reduce the content of heavy metal cadmium in grains, and at the same time increase rice yield; the foliar spraying method is convenient to operate, and high-yield, healthy and safe rice can be obtained in a simple and economical way. DETAILED DESCRIPTION

[0069] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0070] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0071] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0072] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0073] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0074] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0075] As a first aspect of the present invention, the present invention provides the use of molybdenum disulfide in the preparation of a foliar barrier for inhibiting the absorption of heavy metal cadmium by rice grains.

[0076] As a second aspect of the present invention, the present invention provides a heavy metal barrier for rice. The raw material composition is, by mass percentage, 20%-30% of molybdenum disulfide, 10%-20% of diammonium hydrogen phosphate, 5%-10% of disodium magnesium ethylenediaminetetraacetate, 5%-10% of zinc ethylenediaminetetraacetate, 10%-20% of silicon fertilizer, 1%-2% of cosolvent, 1%-2% of solubilizer, 1%-2% of ethanol and the balance of water.

[0077] As a preferred embodiment of the present invention, the particle size of the molybdenum disulfide is ≤100 nm.

[0078] As a preferred embodiment of the present invention, the purity of the molybdenum disulfide is ≥99%.

[0079] As an optional embodiment of the present invention, the silicon fertilizer includes nano-silicon dioxide, sodium metasilicate or nano-elemental silicon.

[0080] As an optional embodiment of the present invention, the co-solvent includes sodium benzoate, sodium salicylate, urea or acetamide.

[0081] As an optional embodiment of the present invention, the solubilizer includes cresol soap or Tween 80.

[0082] As a third aspect of the present invention, the present invention provides a method for preparing the above-mentioned heavy metal barrier for rice, comprising the following steps:

[0083] The raw materials are weighed according to mass percentage and mixed evenly to obtain the special heavy metal barrier for rice.

[0084] As a fourth aspect of the present invention, a method for reducing the cadmium content in rice grains is provided, wherein the rice-specific heavy metal barrier is sprayed on rice fields contaminated with heavy metal cadmium at two or three stages, namely, the tillering stage, the booting stage, and the filling stage.

[0085] As a preferred embodiment of the present invention, the application amount of the heavy metal barrier agent is 100 mL-200 mL / mu each time.

[0086] As a preferred embodiment of the present invention, the heavy metal barrier agent is diluted with water to a concentration of the molybdenum disulfide component of 0.1 g / L-0.25 g / L before spraying.

[0087] As a preferred embodiment of the present invention, the pH value of the soil in the paddy field contaminated by heavy metal cadmium is less than 7.5.

[0088] As a preferred embodiment of the present invention, the spraying is specifically to spray the diluted heavy metal barrier agent solution on the rice leaves in a spraying form.

[0089] As a preferred embodiment of the present invention, the spraying is done during the period of strong sunlight at noon.

[0090] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0091] When referring to room temperature or normal temperature in the specific embodiments of the present invention, it specifically refers to 20-30°C.

[0092] Unless otherwise specified, all raw materials used in the embodiments of the present invention are common commercial products.

[0093] The average particle size of molybdenum disulfide used in the following examples and comparative examples is 90 nm and the purity is 99%; the average particle size of nano-silicon dioxide is 50 nm; and the average particle size of elemental silicon is 50 nm.

[0094] Example 1

[0095] A heavy metal barrier agent for rice, the raw materials of which are composed of the following by mass percentage:

[0096] 25% molybdenum disulfide, 15% diammonium hydrogen phosphate, 8% disodium magnesium ethylenediaminetetraacetic acid, 7% zinc ethylenediaminetetraacetic acid, 15% silicon fertilizer (nano silicon dioxide), 1.5% cosolvent (urea), 1.5% solubilizer (Tween 80), 1.5% ethanol and the balance water.

[0097] Weigh the raw materials according to mass percentage, mix them evenly, and obtain a special heavy metal barrier for rice.

[0098] Example 2

[0099] A heavy metal barrier agent for rice, the raw materials of which are composed of the following by mass percentage:

[0100] Molybdenum disulfide 22%, diammonium hydrogen phosphate 18%, disodium magnesium EDTA 6%, zinc EDTA 6%, silicon fertilizer (sodium metasilicate) 16%, cosolvent (sodium salicylate) 1.2%, solubilizer (cresol soap) 1.8%, ethanol 1% and water balance.

[0101] Weigh the raw materials according to mass percentage, mix them evenly, and obtain a special heavy metal barrier for rice.

[0102] Example 3

[0103] A heavy metal barrier agent for rice, the raw materials of which are composed of the following by mass percentage:

[0104] 20% molybdenum disulfide, 12% diammonium hydrogen phosphate, 5% disodium magnesium ethylenediaminetetraacetic acid, 5% zinc ethylenediaminetetraacetic acid, 18% silicon fertilizer (nano elemental silicon), 1% cosolvent (acetamide), 1% solubilizer (Tween 80), 2% ethanol and the balance water.

[0105] Weigh the raw materials according to mass percentage, mix them evenly, and obtain a special heavy metal barrier for rice.

[0106] Comparative Example 1

[0107] Same as Example 1, except that the mass amount of molybdenum disulfide is replaced by ammonium molybdate.

[0108] Comparative Example 2

[0109] Same as Example 1, except that the mass amount of zinc edetate is replaced by zinc sulfate.

[0110] Comparative Example 3

[0111] The same as Example 1, except that the use of diammonium hydrogen phosphate is omitted and the content of diammonium hydrogen phosphate is supplemented with water.

[0112] Comparative Example 4

[0113] Same as Example 1, except that the mass amount of magnesium disodium edetate is replaced by zinc edetate.

[0114] Comparative Example 5

[0115] Same as Example 1, except that the mass amount of zinc edetate is replaced by magnesium disodium edetate.

[0116] Application Example 1

[0117] In 2023, a test was conducted in a cadmium-contaminated rice paddy in Daye City, Hubei Province. Testing of the irrigation water revealed a cadmium ion concentration of 0.002 mg / L, below the limit of ≤0.01 mg / L in the Agricultural Irrigation Water Quality Standard (GB 5084-2021). The paddy soil had a pH of 5.76, a total cadmium content of 0.542 mg / kg, and an available cadmium content of 0.257 mg / kg.

[0118] Several experimental plots were divided in the cadmium-contaminated rice fields with consistent soil fertility and cadmium pollution. The area of ​​each experimental plot was 100m 2 The experimental groups used the rice-specific heavy metal barrier prepared in Examples 1-3 and Comparative Examples 1-5, respectively (three parallel tests were set up for each experimental group. The rice-specific heavy metal barrier was sprayed once during the tillering stage, booting stage, and filling stage, respectively. 200 mL of the stock solution was sprayed per mu each time. The solution was diluted with water to a concentration of 0.1 g / L of molybdenum disulfide component or ammonium molybdate component before spraying. The spraying was done in an area away from strong sunlight at noon. The rice variety was Guangliangyouxiang 66 (hybrid rice). The control group did not use any heavy metal barrier (three parallel tests were set up). Other field management activities were carried out in accordance with local conventional management methods.

[0119] During the rice harvest period, the rice yield of each experimental group and the control group was calculated based on the actual harvest and measurement in each plot, and the cadmium content in rice grains was tested in accordance with the Chinese national standard GB5009.15-2023 "National Food Safety Standard - Determination of Cadmium in Food". The results were taken as the average of three parallel experiments, as shown in Table 1.

[0120] Table 1

[0121] Rice yield (kg / mu) Cadmium content in rice grains (mg / kg) Example 1 459.0 0.162 Example 2 465.8 0.169 Example 3 498.4 0.171 Comparative Example 1 430.6 0.211 Comparative Example 2 428.5 0.189 Comparative Example 3 443.0 0.195 Comparative Example 4 451.1 0.181 control group 425.0 0.271

[0122] As shown in Table 1, the field test results show that compared with the control group, the rice treated with Examples 1-3 increased yield by 8.0%, 9.6%, and 17.3%, respectively, and the cadmium content in the grains decreased by 40.2%, 37.6%, and 36.9%, respectively. In addition, the cadmium content in brown rice was significantly lower than the national limit (0.2 mg / kg). This indicates that spraying the rice-specific heavy metal barrier of the present invention has the dual effects of increasing rice yield and reducing cadmium.

[0123] Application Example 2

[0124] In 2024, a test was conducted in a cadmium-contaminated rice paddy in Daye City, Hubei Province. Testing of the irrigation water revealed a cadmium ion concentration of 0.006 mg / L, below the limit of ≤0.01 mg / L in the Agricultural Irrigation Water Quality Standard (GB5084-2021). The paddy soil had a pH of 6.25, a total cadmium content of 0.749 mg / kg, and an available cadmium content of 0.305 mg / kg.

[0125] Several experimental plots were divided in the cadmium-contaminated rice fields with consistent soil fertility and cadmium pollution. The area of ​​each experimental plot was 100m 2 The experimental groups used the rice-specific heavy metal barrier agents prepared in Examples 1-3 and Comparative Examples 1-5, respectively (three parallel tests were set up for each experimental group. The rice-specific heavy metal barrier agent was sprayed once during the tillering stage, booting stage, and filling stage of rice, respectively. 200 mL of the stock solution was sprayed per mu each time, and the solution was diluted with water to a concentration of 0.25 g / L of the molybdenum disulfide component or the ammonium molybdate component. The spraying was carried out after avoiding the strong light period at noon. The rice variety was Huanghuazhan (conventional rice)). The control group did not use any heavy metal barrier agent (three parallel tests were set up). Other field management activities were carried out in accordance with local conventional management methods.

[0126] During the rice harvest period, the rice yield of each experimental group and the control group was counted and the cadmium content of rice grains was tested. The results were taken as the average of three repetitions, as shown in Table 2.

[0127] Table 2

[0128] Rice yield (kg / mu) Cadmium content in rice grains (mg / kg) Example 1 520.9 0.136 Example 2 513.2 0.133 Example 3 511.9 0.141 Comparative Example 1 479.8 0.203 Comparative Example 2 495.3 0.188 Comparative Example 3 500.2 0.176 Comparative Example 4 498.6 0.196 control group 464.7 0.250

[0129] As shown in Table 2, the field test results show that compared with the control group, the rice treated with Examples 1-3 increased yield by 12.1%, 10.4%, and 10.2%, respectively, and the cadmium content in the grain decreased by 45.6%, 46.8%, and 43.6%, respectively. Moreover, the cadmium content in brown rice was significantly lower than the national limit (0.2 mg / kg). This indicates that spraying the rice-specific heavy metal barrier of the present invention has the dual effects of increasing rice yield and reducing cadmium.

[0130] Test Example 1

[0131] Differences in cadmium inhibition of nano-silica in wheat and rice

[0132] The experiment was conducted in 2023-2024 in a cadmium-contaminated rice paddy (rice-wheat rotation) in Shiyan City, Hubei Province. Testing of the irrigation water revealed a cadmium ion concentration of 0.005 mg / L, below the limit of ≤0.01 mg / L in the Agricultural Irrigation Water Quality Standard (GB5084-2021). The soil pH was 6.27, with a total cadmium content of 0.530 mg / kg and an available cadmium content of 0.223 mg / kg.

[0133] Several experimental plots were divided in the cadmium-contaminated rice fields with consistent soil fertility and cadmium pollution. The area of ​​each experimental plot was 50m 2The experimental group used nano-liquid silicon fertilizer (containing nano-silicon dioxide; three parallel experiments were set up for each experimental group. Nano-liquid silicon fertilizer was sprayed once during the tillering, booting, and grain filling stages of wheat and rice, with 100 mL of the original solution sprayed per mu each time, diluted 1000 times with water before spraying. Spraying was avoided during the period of strong sunlight at noon. The wheat variety was Yumai 34, and the rice variety was Quanyou 967). The control group did not use any heavy metal barrier agents (three parallel experiments were set up). Other field management activities were carried out according to local routine management methods.

[0134] During the wheat and rice harvest seasons, the wheat and rice yields of each experimental group and the control group were calculated based on the actual harvest and measurement in each plot. The cadmium content in wheat and rice grains was tested in accordance with the Chinese national standard GB5009.15-2023 "National Food Safety Standard - Determination of Cadmium in Food". The results were the average of three parallel experiments, as shown in Table 3.

[0135] Table 3

[0136]

[0137] Table 3 shows that the field test results show that compared with the control treatment, the experimental treatment increased wheat yield by 5.2% and reduced grain cadmium content by 15.3%. Rice yield increased by 5.9% and reduced grain cadmium content by 29.1%. The reduction rate of cadmium content in rice grains was significantly higher than that in wheat. This indicates that foliar application of nano-silicon (SiO2) reduced Cd content in rice grains at a higher rate than that in wheat grains. This is primarily due to the fact that rice leaves have a significantly higher silicon deposition capacity than wheat, and the expression levels of its silicon transporters (such as OsLsi1 and OsLsi2) are significantly higher than those in wheat. In addition, organic acids (such as citric acid) secreted by wheat roots dissolve silicon-Cd co-precipitates, weakening the control effect.

[0138] Test Example 2

[0139] Differences in cadmium blocking performance of the rice-specific heavy metal barrier of the present invention in rice and corn

[0140] In 2024, a rice planting experiment was conducted in a cadmium-contaminated rice field in Shiyan City, Hubei Province. The irrigation water tested had a cadmium ion concentration of 0.007 mg / L, lower than the limit (≤0.01 mg / L) in the Agricultural Irrigation Water Quality Standard (GB5084-2021). The soil pH was 6.34, the total cadmium content was 0.575 mg / kg, and the available cadmium content was 0.211 mg / kg. At the same time, a corn planting experiment was conducted on a local cadmium-contaminated dryland. The irrigation water tested had a cadmium ion concentration of 0.007 mg / L, lower than the limit (≤0.01 mg / L) in the Agricultural Irrigation Water Quality Standard (GB5084-2021). The soil pH was 6.41, the total cadmium content was 0.586 mg / kg, and the available cadmium content was 0.193 mg / kg.

[0141] Several experimental plots were divided in cadmium-contaminated rice fields and dry land with consistent soil fertility and cadmium pollution, with an area of ​​50m2 per plot. 2 The experimental group used the special heavy metal barrier for rice prepared in Example 1 (three parallel tests were set for each experimental group. The heavy metal barrier was sprayed once in the tillering stage, booting stage and filling stage of rice, and once in the jointing stage, large trumpet stage and filling stage of corn. Each time, 200 mL of the stock solution was sprayed per mu, and it was diluted with water to a concentration of 0.25 g / L of molybdenum disulfide component before spraying. The strong light period at noon was avoided during spraying. The rice variety was Quanyou 967 and the corn variety was Huayu 11). The control group did not use any heavy metal barrier (three parallel tests were set). Other field management activities were carried out in accordance with local conventional management methods.

[0142] During the rice and corn harvest period, the rice and corn yields of each experimental group and the control group were calculated based on the actual harvest and measurement in each plot. The cadmium content in rice and corn grains was tested in accordance with the Chinese national standard GB5009.15-2023 "National Food Safety Standard - Determination of Cadmium in Food". The results were taken as the average of three parallel experiments, as shown in Table 4.

[0143] Table 4

[0144]

[0145] As shown in Table 4, the results of the field test show that compared with the control group, the rice yield of the test group increased by 10.3%, and the cadmium content of the grain decreased by 43.9%; the corn yield increased by 3.2%, and the cadmium content of the grain decreased by 28.4%; the cadmium content reduction rate of rice grains was significantly higher than that of corn. This shows that the Cd reduction rate of rice grains was higher than that of corn grains when the special heavy metal barrier for rice of the present invention was sprayed. This may be because the thickness of the wax layer of corn leaves (3-4 μm) is 2-3 times that of rice (1-1.5 μm), and the penetration rate of nanoparticles decreased by 60%; and corn lacks the OsHMA3 homologous gene and has a weak vacuolar compartmentalization ability, so Cd is more likely to enter the grains through the symplasm pathway.

[0146] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. Application of molybdenum disulfide in the preparation of foliar barrier for inhibiting the absorption of heavy metal cadmium by rice grains.

2. A heavy metal barrier for rice, characterized in that: Calculated by mass percentage, the raw material composition is: 20%-30% of molybdenum disulfide, 10%-20% of diammonium hydrogen phosphate, 5%-10% of disodium magnesium ethylenediaminetetraacetate, 5%-10% of zinc ethylenediaminetetraacetate, 10%-20% of silicon fertilizer, 1%-2% of cosolvent, 1%-2% of solubilizer, 1%-2% of ethanol and the balance of water.

3. The heavy metal barrier for rice according to claim 2, characterized in that: The particle size of the molybdenum disulfide is ≤100 nm.

4. The heavy metal barrier for rice according to claim 2, characterized in that: The silicon fertilizer includes nano silicon dioxide, sodium metasilicate or nano elemental silicon.

5. The heavy metal barrier for rice according to claim 2, characterized in that: The cosolvent includes sodium benzoate, sodium salicylate, urea or acetamide.

6. The heavy metal barrier for rice according to claim 2, characterized in that: The solubilizing agent includes cresol soap or Tween 80.

7. A method for preparing the heavy metal barrier for rice according to any one of claims 2 to 6, characterized in that: The following steps are involved: The raw materials are weighed according to mass percentage and mixed evenly to obtain the special heavy metal barrier for rice.

8. A method for reducing cadmium content in rice grains, characterized in that: For rice fields polluted by heavy metal cadmium, the rice-specific heavy metal barrier according to any one of claims 2 to 6 is sprayed at two or three stages of the rice tillering stage, booting stage and filling stage.

9. The method according to claim 8, wherein The application amount of the heavy metal barrier agent is 100mL-200mL / mu each time; And / or, the heavy metal barrier agent is diluted with water to a concentration of the molybdenum disulfide component of 0.1 g / L-0.25 g / L before spraying.

10. The method according to claim 8, wherein The pH value of the soil in the rice field contaminated by heavy metal cadmium is less than 7.5.

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