CN115340875A

CN115340875A - Barrier agent for reducing content of harmful heavy metals in plants, use method and application

Info

Publication number: CN115340875A
Application number: CN202211041772.0A
Authority: CN
Inventors: 刘卫东; 赵蓓; 杨立新
Original assignee: Chongqing Miaozhan Ecological Agriculture Development Co ltd; Chongqing Miaozhu Biotechnology Co ltd
Current assignee: Chongqing Miaozhan Ecological Agriculture Development Co ltd; Chongqing Miaozhu Biotechnology Co ltd
Priority date: 2022-08-29
Filing date: 2022-08-29
Publication date: 2022-11-15
Anticipated expiration: 2042-08-29
Also published as: CN115340875B

Abstract

The invention provides a blocking agent for reducing the content of harmful heavy metals in plants, which comprises soluble phosphate, quaternized chitosan and N-acetylglucosamine, and also provides a use method and application of the blocking agent. The 'ecological and chemical combined remediation technology' is applied to heavy metal blocking, secondary pollution is not introduced, and the harmful heavy metal content of plants can be obviously reduced under the condition of low-concentration spraying.

Description

Barrier agent for reducing content of harmful heavy metals in plants, use method and application

Technical Field

The invention belongs to the technical field of heavy metal polluted farmland restoration, and particularly relates to a blocking agent for reducing harmful heavy metal content of plants, a use method and application thereof.

Background

The national soil pollution condition survey shows that the soil environment of China is not optimistic overall, the soil pollution of partial regions is serious, and the soil environment quality of cultivated land is great. The heavy metal pollution area of the cultivated land in China exceeds 16 percent, wherein the situation is serious around big cities, industrial and mining areas, and serious hidden danger is brought to the water environment and the food safety. According to measurement and calculation, the current grain polluted by heavy metal is up to 1200 ten thousand tons every year, which is equivalent to one-year grain of 4000 ten thousand people. Heavy metal pollution has the characteristics of large and wide range, long-term property, enrichment property, long-term property, high toxicity and the like, and the enrichment is generated by long-term ingestion through a food chain, so that the health of a human body is seriously threatened. Heavy metals not only have negative effects on the number of soil microorganisms, the population structure and the activity of soil enzymes, so that the soil fertility is reduced, but also interfere the normal growth and metabolism of crops, reduce the yield and the quality of the crops, finally accumulate in human bodies through food chains, cause harm to the health of the human bodies, seriously affect the prevention and health care effects of functional nutritional agricultural products, and become bottleneck restriction on the development of functional agriculture.

In 2016, china promulgates 'action plan for preventing and controlling soil pollution', determines the idea of classified management of agricultural lands, and emphasizes on safe utilization of medium and light polluted farmlands. In 2019, the national ministry of agricultural and rural areas publishes the guide for treatment and restoration of polluted cultivated land, proposes a mode of selecting treatment and restoration according to local conditions, and reduces the input and total amount of pollutants in the cultivated land soil or reduces the activity of the pollutants through measures such as source control, agricultural engineering regulation, soil improvement, phytoremediation and the like, thereby reducing the risk of exceeding the standard of pollutants of agricultural products and improving the environmental quality of the polluted cultivated land soil.

Aiming at the excessive heavy metal residue of crops caused by heavy metal pollution in large-area cultivated land, the method of conditioning the pH value of soil, applying organic fertilizer, applying microbial fertilizer and the like is mainly adopted, and the purpose is to reduce the migration capability and biological effectiveness of heavy metal in the soil through the actions of chelating complexation, adsorption, precipitation and the like, so as to achieve the effect of reducing the total absorbable amount of the heavy metal, play a certain role in reducing the heavy metal residue of the crops, but have limited effect; when the soil conditioner and the passivator are applied for a long time, secondary pollution is introduced, the granular structure of soil is damaged, soil hardening is caused, the land fertility of cultivated land is reduced, the crop yield of the plough is influenced, and the income of farmers is greatly influenced.

The biotoxicity and accumulation capacity of heavy metals in crops is not completely controlled by the total amount of heavy metals, but rather is determined by the bioavailability, root absorption and transfer of heavy metals in plants. The soil contains organic matter and other nutrients, microbes and root system, and has obvious effect on the bioavailability of heavy metal in soil, the cell wall of microbes consists of mannose, glucan, protein and chitin, extracellular Polysaccharide (EPS) covered on the cell surface, polar functional group on the cell wall and chemical groups inside the cell can combine with metal ion to realize extracellular enrichment precipitation and cell surface adsorption or complexation, and the existence of great amount of microbes and organic matter in soil can solidify heavy metal ion, reduce its bioavailability and reduce the absorption of heavy metal ion by root system.

In the prior art, the schemes of conditioning the pH value of soil, applying organic fertilizers additionally, applying microbial fertilizers additionally and the like have adverse effects on the structure and physicochemical properties of the soil after long-term application, are easy to introduce secondary pollution, and have no obvious effect on reducing heavy metals in plants. Aiming at the relationship between plant root system absorption and soil micro-ecology, an ecological and chemical combined remediation technology is used for heavy metal blocking, soil heavy metal pollution is solved under the condition of low-concentration spraying, and safe agricultural products can be produced in the farmland with moderate and light heavy metal pollution.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a blocking agent which can be used for blocking heavy metal by applying an 'ecological and chemical combined remediation technology', does not introduce secondary pollution and can obviously reduce the content of harmful heavy metal in plants under the condition of low-concentration spraying, and a using method and application thereof.

The technical problem to be solved by the invention is realized by adopting the following technical scheme:

the invention aims to provide a blocking agent for reducing the content of harmful heavy metals in plants, which is characterized by comprising soluble phosphate, quaternized chitosan and N-acetylglucosamine.

Further, the blocking agent comprises the following raw materials in percentage by weight: 15 to 25 percent of soluble phosphate; quaternized chitosan, 20-30%; 10 to 15 percent of N-acetylglucosamine.

Further, the blocking agent is a root-applied blocking agent.

Further, the soluble phosphate is dihydrogen phosphate or diammonium phosphate.

Further, the dihydrogen phosphate is potassium dihydrogen phosphate or calcium dihydrogen phosphate.

The second purpose of the invention is to provide a using method of the blocking agent for reducing the content of harmful heavy metals in plants, which is characterized by comprising the following steps: the method comprises the steps of spraying the blocking agent to soil for the first time during land leveling, rotary tillage or base fertilizer application and top dressing before plant cultivation, and spraying the blocking agent to the soil at the roots of plants for the second time during a plant grouting period, a fruit expanding period or a color-changing and sugar-increasing period.

Further, before use, a blocking agent is prepared, the soluble phosphate, the quaternized chitosan and the N-acetylglucosamine which are weighed according to a certain proportion are mixed and then the volume is determined by water, and the prepared blocking agent comprises the following raw materials in percentage by mass: 15 to 25 percent of soluble phosphate; quaternized chitosan, 20-30%; 10 to 15 percent of N-acetylglucosamine.

Further, the blocking agent is diluted by 50 times before the blocking agent is sprayed for the first time, and the blocking agent is diluted by 100 times before the blocking agent is sprayed for the second time.

Further, for annual plants, the use method of the blocking agent comprises the following steps:

the method comprises the steps of firstly spraying the blocking agent on soil during land leveling and rotary tillage before plant cultivation, then spraying the blocking agent on root soil for the second time during a plant grouting period or a fruit expanding period and a color and sugar changing period, and keeping the soil fully wet during spraying.

Further, for perennial plants, the use method of the barrier agent comprises the following steps:

when base fertilizer or additional fertilizer is applied every year, the blocking agent is sprayed along the dripping line of the tree crown for the first time through drip irrigation or mechanical pressure, the blocking agent is sprayed for the second time in the fruit expanding period or in the month before picking, and the soil is kept fully wet in the spraying process.

Further, the spraying blocking agent is sprayed in a drip irrigation mode or is sprayed at the position of 30-50 cm of the root depth along the water dripping line of the tree crown by mechanical pressure.

Further, the using amount of the blocking agent is adjusted according to the content of heavy metal in the soil, and is 0.7<P _Heald When the spraying amount is less than or equal to 1.0, the total spraying amount per mu is 0.5-1L; when 1.0<P _Heald When the spraying amount is less than or equal to 2.0, the total spraying amount per mu is 1-2L; when 2.0<P _Heald When the spraying amount is less than or equal to 3.0, the total spraying amount per mu is 2-3L; p is _Heald Is the comprehensive pollution index of the heavy metal in the soil.

Further, the calculation formula of the single-term pollution index of the heavy metal i for evaluating the heavy metal pollution degree of the soil is as follows:

Pi＝Ci/Si

in the formula, pi is a single pollution index of heavy metal i in the soil of the sampling point, ci is an actual measured value of the content of the heavy metal i, and Si is an initial critical value of the pollution content of the heavy metal i. Pi is less than or equal to 1, indicating no pollution, and no comprehensive pollution index evaluation is carried out; pi >1 indicates contamination, and the composite contamination index is further evaluated.

The calculation formula of the inner Metro comprehensive pollution index for evaluating the heavy metal pollution degree of the soil is as follows:

P _heald ＝{(P ² _imax +P ² _iave )/2} ^1/2

In the formula P _Heald Is the comprehensive pollution index P of the heavy metal in the soil at a sampling point ² _imax Is the maximum value of the single pollution index of heavy metal in soil, P ² _iave The average value of the single pollution indexes of the heavy metals in the soil is shown. P is _Heald Has 5 grades of P _Heald Cleaning at less than or equal to 0.7, 0.7<P _Heald Less than or equal to 1.0 is still clean (warning limit), 1.0<P _Heald Slight pollution of 2.0 or less, 2.0<P _Heald Moderate pollution with less than or equal to 3.0, P _Heald >3.0 is heavily contaminated.

Further, the barrier agent is used alone as a root-applied barrier agent.

Further, the blocking agent is used as a fertilizer additive in combination with a fertilizer.

Further, the fertilizer comprises organic fertilizer and biological fertilizer.

Further, the blocking agent is a lead, cadmium or chromium heavy metal blocking agent.

The third purpose of the invention is to provide the application of the use method of the blocking agent in reducing the content of heavy metals such as lead, cadmium and chromium in plants.

The invention reduces the content of harmful heavy metals in plants, especially the content of lead, cadmium and chromium in plants, by an 'ecological and chemical combined remediation' technology.

Soluble phosphate is added, and the soluble phosphate and heavy metal ions are subjected to chemical precipitation reaction in soil, roots and stems, so that in-situ passivation and blocking of heavy metals are realized, root absorption and migration from roots to edible parts are reduced, and redundant phosphate can be used as phosphate fertilizer to be absorbed by plants, so that no residue is generated, and secondary pollution is avoided.

The N-acetylglucosamine is added, the rapid mass propagation of microorganisms in the soil is promoted, the soil microecology is activated, the biological effectiveness of the soil is reduced by solidifying heavy metal ions through biological adsorption, and the migration of heavy metals from the soil to root hair cells is reduced.

The quaternary ammonium chitosan is added, amino and hydroxyl in the molecules of the quaternary ammonium chitosan can generate chelation reaction with metal ions to adsorb heavy metal ions, the migration of heavy metals from soil to root hair cells is reduced, meanwhile, the quaternary ammonium chitosan can be used as macromolecular organic matters to quickly form soil aggregates in the soil, loosen the soil, improve the physical properties of the soil, provide a good soil microenvironment for beneficial microorganisms, slowly degrade the soil aggregates into N-acetylglucosamine, and continuously activate the soil microecology for a long time.

Compared with the prior art, the invention has the beneficial technical effects that:

1. the invention can obviously reduce the content of harmful heavy metals in plants under the condition of low-concentration spraying, is greatly lower than the limit requirement in national standard food, and has obvious effect of obstructing the harmful heavy metals.

2. The ecological influence is small. The invention integrates the micro-ecological restoration, plant passivation and chemical restoration technologies, pays attention to the coordination with the natural ecological process, does not form secondary pollution and does not influence the safety of agricultural products.

3. The cost is low. The invention takes the advantages of micro-ecological restoration, and the cost is lower than that of microbial restoration.

4. The blocking agent can be prepared into aqueous solution for independent spraying, and can also be used as an additive of organic fertilizers, biological fertilizers and other fertilizers, so that the blocking effect of the blocking agent on harmful heavy metals is enhanced, and the blocking agent is convenient to popularize.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

In addition, unless otherwise specifically indicated, various starting materials, reagents, instruments and equipment used in the present invention may be commercially available or prepared by existing methods.

Example 1 verification test for rice field

The test base is a heavy metal solidification and passivation test point demonstration project for Chongqing cadmium polluted farmland. Through field investigation and soil environment quality evaluation, and rice planting field management, a barrier technology implementation plan is formed, and project implementation scheme compilation is formed.

Dividing a 400 mu rice trial farmland into 8 areas, each area is 50 mu, each area is provided with a 2-meter protection row, and 4 experimental groups and 4 contrast groups are randomly arranged. The soil sample is sampled, stored, treated and analyzed according to the technical Specification for soil environmental monitoring (HT/J166-2004), before sampling, the accumulated water on the upper part of the rice field is drained, 10 sampling points are arranged in a test base according to a chessboard pattern, 0-20 cm of surface soil is equivalently collected, the surface soil is uniformly mixed, impurities are removed, the surface soil is naturally air-dried, crushed and sieved by a nylon sieve, the crushed soil is leached by aqua regia, the contents of lead, cadmium and chromium are measured by an atomic absorption spectrophotometry, and the comprehensive pollution index of the soil is calculated.

The calculation formula of the single-term pollution index of the heavy metal i for evaluating the heavy metal pollution degree of the soil is as follows:

Pi＝Ci/Si

P _heald ＝{(P ² _imax +P ² _iave )/2} ^1/2

In the formula P _Heald Is the comprehensive pollution index P of the heavy metal in the soil at a sampling point ² _imax Is the maximum value of the single pollution index of heavy metal in soil, P ² _iave The average value of the single pollution indexes of the heavy metals in the soil is obtained. P _Heald Has 5 grades of P _Heald Cleaning at less than or equal to 0.7, 0.7<P _Heald Less than or equal to 1.0 is still clean (warning limit), 1.0<P _Heald Slight contamination of not more than 2.0, 2.0<P _Heald Moderate pollution with less than or equal to 3.0, P _Heald >3.0 is heavily contaminated. When 0.7<P _Heald When the spraying amount is less than or equal to 1.0, the total spraying amount per mu is 0.5-1L; when 1.0<P _Heald When the spraying amount is less than or equal to 2.0, the total spraying amount per mu is 1-2L; when 2.0<P _Heald When the spraying amount is less than or equal to 3.0, the total spraying amount per mu is 2-3L.

Determining the comprehensive soil pollution index P according to calculation _Heald 0.9, thereby determining the barrier per muThe spraying amount of the agent is 0.5L. The barrier agent is sprayed on the experimental group, irrigation water is applied on the control group, the fertilization and planting time and pesticide in each area are the same as the daily management in the field, and the crops are harvested uniformly after being matured. The compositions of the blocking agents in this example are shown in table 1:

TABLE 1 composition of Rice Barrier

In this embodiment, the preparation method of the rice blocking agent is as follows: 150g of monopotassium phosphate, 200g of quaternized chitosan and 150g of N-acetylglucosamine are weighed, mixed, dissolved by water and added into a volumetric flask to be constant volume to 1L for later use.

Spraying the blocking agent for the first time, and synchronously carrying out the selection when the rice field is ploughed in the beginning of 4 months. Measuring 0.5L of the blocking agent, diluting by 50 times, loading into a spraying device, fixing the spraying device on a rotary cultivator, synchronously spraying the soil during rotary cultivation, uniformly combining the blocking agent with the soil on a rotary cultivation surface, and keeping the uniform spraying amount in the implementation process.

And spraying the barrier agent for the second time, namely measuring 0.5L of the barrier agent in the rice grouting period, spraying the barrier agent to the soil in an unmanned aerial vehicle mode after diluting by 100 times, and keeping the spraying amount uniform in the spraying process.

The growth cycle of the rice in the test base is about 160 days, the roots are turned over in the middle and last ten days of 3 months, the rice is transplanted after ploughing and watering in the early 4 months, and watering is carried out in the middle and last ten days of 5 months; drying the field in the late 7 th month and harvesting uniformly at the bottom of 8 months. The inspection-submitted rice is collected by the joint sampling of farmers, villagers and planting enterprises, and sent to Shanghai Tong Biao SGS to detect the content of heavy metal cadmium. The detection comparison ratio of the average contents of heavy metals of lead, cadmium and chromium in the experimental group and the average content of the reference group is shown in table 2:

TABLE 2 comparison table for testing heavy metal content of experimental group and control group of rice

( Note: ND represents that the content of the heavy metal is below the detection quantitative limit and can not be detected; 2. the limit standard of cadmium content in national standard food is 0.1mg/kg )

As can be seen from the table, the cadmium content of the rice experimental group is reduced by 75.1% compared with that of the control group, so that the content of heavy metal lead, cadmium and chromium in the rice sprayed with the blocking agent is obviously reduced compared with the content of heavy metal in the plant sprayed with the blocking agent, and the effect of reducing the content of heavy metal in the plant is obvious.

Example 2 field verification test for Zanthoxylum bungeanum

A harmful heavy metal barrier verification test is carried out in a Chongqing pepper planting base, a barrier technology implementation plan is formed by field investigation and soil environment quality evaluation and pepper planting field management, and a project implementation scheme is worked out.

The 600 mu pepper experiment base is divided into 6 areas, each area is 100 mu, each area is provided with a 2-meter protection row, and 3 experiment groups and 3 comparison groups are randomly arranged. In this example, soil samples were sampled in the same manner as in example 1, and the soil comprehensive pollution index P was determined by calculation _Heald 1.2, so that the spraying amount of the barrier agent per mu is determined to be 1.5L. The barrier agent is sprayed on the experimental group, the irrigation water is applied on the control group, the fertilization and planting time, the pesticide and the daily management in the field of each area are the same, and the crops are harvested uniformly after being matured. The compositions of the blocking agents in this example are shown in table 3:

TABLE 3 composition of the Pepper Barrier

The method for preparing the pepper blocking agent in this example refers to example 1.

Spraying the blocking agent for the first time, and synchronously applying the organic base fertilizer when the pepper is ditched. Measuring 1.5L of the blocking agent per mu of land, diluting by 50 times, spraying the blocking agent on the base fertilizer and the ditching soil to enable the blocking agent to be uniformly combined with the root system soil, and covering soil after spraying.

Spraying the blocking agent for the second time, selecting the expanding period after the initial buds of the zanthoxylum at the bottom of April, measuring 1.5L of the blocking agent per mu of land, diluting by 100 times, and spraying root soil in a drip irrigation mode.

The inspection-submitted Chinese prickly ash is collected by combined sampling of agricultural parks and planting enterprises and is detected by the Shanghai Tong standard SGS. The detection comparison ratio of the average contents of heavy metals cadmium, lead and chromium in the experimental group and the average content of the reference group is shown in table 4:

table 4 table for detecting and comparing heavy metal content of pepper experimental group and control group

( Note: ND represents that the content of the heavy metal is below the detection quantitative limit and can not be detected; 2. the limit standard of cadmium content in national standard food is 0.11mg/kg )

As can be seen from the table, the lead content of the pepper experimental group is reduced by 85.9 percent compared with the control group, the cadmium content is reduced by 68.6 percent compared with the control group, the national standard requirement of the pepper is met, the chromium content cannot be detected (the detection quantitative limit is 0.1 mg/kg), and therefore, the heavy metal lead and cadmium content in the pepper is obviously reduced after the barrier agent is sprayed according to the method, and the effect of reducing the heavy metal content in the plant is obvious compared with the method of spraying the barrier agent.

Example 3 tea field validation test

Harmful heavy metal barrier verification tests are carried out in Guangxi tea planting bases, barrier technology implementation plans are formed through field investigation and soil environment quality assessment and combined with planting field management, and project implementation schemes are worked out.

Dividing a tea experiment base into 4 areas with each area being 25 mu and each area being provided with a protection row with the length of 2 meters, and randomly arranging 2 experiment groups and 2 comparison groups. The soil is sampled, processed and analyzed and tested according to the mode of the embodiment 1, and the comprehensive soil pollution index P is determined _Heald 2.1, so that the spraying amount of the barrier agent per mu is determined to be 2.5L. And spraying a blocking agent on the experimental group, not applying the blocking agent on the control group, and uniformly harvesting after the fertilizer is matured, wherein the fertilization time, the planting time, the pesticide and the field daily management in each area are the same. The compositions of the blocking agents in this example are shown in table 5, respectively:

TABLE 5 composition of tea leaf Barrier

In this example, the method of preparing the tea leaf barrier agent is described in example 1.

Spraying the separating agent for the first time, selecting 11 months, performing the implementation of the base fertilizer, measuring 2.5L of the separating agent, diluting by 50 times, uniformly selecting 2-3 points per tea tree, spraying the soil at a position 30-50 cm away from the root of the tea tree by using a pressure gun, wherein the depth is about 20-30cm, and the soil is kept fully wet in the spraying process and the ground surface is not accumulated with water.

Spraying the blocking agent for the second time, measuring the blocking agent for 2.5L in a month before picking the tea in the first spring of 3 months, diluting by 100 times, and spraying the soil, wherein the spraying process is consistent with the spraying process for the first time.

After the tea leaves are picked from the tea leaf center, the tea leaves are sent to Shanghai Tong Biao SGS to detect the content of heavy metals of lead, cadmium and chromium. The detection ratio of the average heavy metal content of the experimental group to the average heavy metal content of the control group is shown in table 6:

table 6 table for detecting and comparing heavy metal content in tea experimental group and control group

( Note: ND represents that the content of the heavy metal is below the detection quantitative limit, and the heavy metal cannot be detected )

As can be seen from the table, the cadmium content of the tea experimental group is reduced by 81.6 percent compared with that of the control group, and the chromium content is reduced by 93.1 percent compared with that of the control group. After the method is used for spraying the blocking agent, the content of heavy metal chromium and cadmium in the tea leaves is obviously reduced compared with the situation that the blocking agent is not sprayed, and the effect of reducing the content of heavy metal in plants is obvious.

The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.

While embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments, which are intended to be illustrative rather than limiting, and many modifications may be made by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A blocking agent for reducing the content of harmful heavy metals in plants is characterized in that: comprises soluble phosphate, quaternized chitosan and N-acetylglucosamine.

2. The blocking agent for reducing the content of harmful heavy metals in plants according to claim 1, wherein: the blocking agent comprises the following raw materials in percentage by weight: 15 to 25 percent of soluble phosphate; quaternized chitosan, 20-30%; 10 to 15 percent of N-acetylglucosamine.

3. The blocking agent for reducing the content of harmful heavy metals in plants according to claim 1, wherein: the blocking agent is a root-applied blocking agent.

4. The use method of the blocking agent for reducing the content of the harmful heavy metals in plants according to any one of claims 1 to 3, is characterized by comprising the following steps: the method comprises the steps of spraying the blocking agent to soil for the first time during land leveling, rotary tillage or winter fertilization before plant cultivation, and spraying the blocking agent to soil at plant roots for the second time during a plant grouting period, a fruit expanding period or a color and sugar conversion period.

5. The method for using the blocking agent for reducing the content of the harmful heavy metals in plants according to claim 4, wherein the blocking agent comprises the following components in percentage by weight: before use, preparing a barrier agent, mixing soluble phosphate, quaternized chitosan and N-acetylglucosamine weighed according to a certain proportion, and then fixing the volume with water to ensure that the prepared barrier agent comprises the following raw materials in percentage by mass: 15 to 25 percent of soluble phosphate; quaternized chitosan, 20-30%; 10 to 15 percent of N-acetylglucosamine.

6. The method for using the blocking agent for reducing the content of the harmful heavy metals in plants according to claim 4, wherein the blocking agent comprises the following components in percentage by weight: the blocking agent is diluted by 50 times before the first spraying of the blocking agent, and the blocking agent is diluted by 100 times before the second spraying of the blocking agent.

7. The method for using the blocking agent for reducing the content of the harmful heavy metals in the plants as claimed in any one of claims 4 to 6, wherein the using amount of the blocking agent is adjusted according to the content of the heavy metals in the soil, and is 0.7<P _Heald When the spraying amount is less than or equal to 1.0, the total spraying amount per mu is 0.5-1L; when 1.0<P _Heald When the spraying amount is less than or equal to 2.0, the total spraying amount per mu is 1-2L; when 2.0<P _Heald When the spraying amount is less than or equal to 3.0, the total spraying amount per mu is 2 to 3L; p _Heald Is the comprehensive pollution index of the heavy metal in the soil.

8. The use method of the blocking agent for reducing the content of the harmful heavy metals in plants according to any one of claims 4 to 7, wherein the blocking agent is used alone as a root-applied blocking agent.

9. The use of the blocking agent for reducing the content of harmful heavy metals in plants according to any one of claims 4 to 7, wherein: the blocking agent is used as a fertilizer additive in combination with a fertilizer.

10. Use of a blocking agent according to any one of claims 4 to 9 for reducing the content of heavy metals such as lead, cadmium and chromium in plants.