A heavy metal pollution control method and system based on fulvic acid type potassium sulfate

Abstract

The present application belongs to the technical field of environmental protection, and relates to a heavy metal pollution control method and system based on fulvic acid type potassium sulfate. First, the types and contents of heavy metal ions in the soil and the complexing ratio with fulvic acid are obtained, the amount of fulvic acid required for complete complexing is calculated, the spreading amount is determined in combination with the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer, after the fertilizer is uniformly spread, a heavy metal ion complexing reaction curve is drawn, the pollution risk is judged according to the residual amount after the reaction reaches equilibrium, and if the standard is exceeded, the demand amount of fulvic acid is recalculated and the spreading amount is adjusted. The present application can effectively complex heavy metal ions in the soil, reduce the activity and biological effectiveness of the heavy metal ions, and reduce the harm to crops; at the same time, in the process of controlling heavy metal pollution, the soil nutrients are adjusted according to the crop demand, the soil fertility is improved, and the healthy growth of crops is ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental protection, and specifically relates to a heavy metal pollution control method and system based on fulvic acid type potassium sulfate. BACKGROUND

[0002] With the rapid development of industry and the unreasonable use of chemical fertilizers and pesticides, the problem of soil heavy metal pollution is becoming increasingly serious. Heavy metals such as lead, cadmium and copper accumulate in the soil, which not only affects the activity of soil microorganisms and destroys the soil structure, but also harms human health through the food chain. At present, the control methods for soil heavy metal pollution mainly include physical remediation, chemical remediation and biological remediation. Among them, chemical remediation is concerned due to its relatively simple operation and fast effect, and one of the common chemical remediation methods is to use complexing agents to form stable complexes with heavy metal ions.

[0003] Fulvic acid is a natural organic complexing agent that can complex with various heavy metal ions, reducing the activity and bioavailability of heavy metal ions. At the same time, potassium sulfate is an important potassium fertilizer that can provide potassium nutrition for crops and promote crop growth. However, when using fulvic acid type potassium sulfate to control soil heavy metal pollution, it is difficult to accurately determine the spreading amount of fulvic acid type potassium sulfate fertilizer to ensure that heavy metal ions are effectively complexed, while avoiding the problem of excessive or insufficient potassium sulfate content in the soil affecting crop growth and soil environment. In addition, the existing methods do not fully consider the synergistic effect of soil nutrient demand and heavy metal pollution control, which may lead to soil nutrient imbalance while controlling heavy metal pollution. SUMMARY

[0004] To solve the above technical problems, the present application realizes the following technical scheme:

[0005] In a first aspect, a heavy metal pollution control method based on fulvic acid type potassium sulfate is provided, including: S1: obtaining the types of heavy metal ions in the soil, the content of each heavy metal ion, and the complexing ratio of each heavy metal ion to fulvic acid; S2: obtaining the fulvic acid demand amount corresponding to the complete complexing of all heavy metal ions in the soil according to the content of each heavy metal ion and the corresponding complexing ratio; S3: obtaining the spreading amount of the fulvic acid type potassium sulfate fertilizer according to the fulvic acid demand amount and the content of the fulvic acid in the fulvic acid type potassium sulfate fertilizer; S4: uniformly spreading the fulvic acid type potassium sulfate fertilizer in the soil according to the spreading amount, and recording the current content of the fulvic acid type potassium sulfate fertilizer in the soil; S5: obtaining the residual amount of each heavy metal ion in the soil after reaching the complexing equilibrium with the fulvic acid; S6: performing S7 for each heavy metal ion; S7: determining whether the residual amount is greater than the agricultural soil pollution risk screening value, if yes, adding a risk label to the heavy metal ion and performing S8, otherwise, performing S9; S8: obtaining the fulvic acid demand amount corresponding to the complete complexing of all heavy metal ions with the risk label in the soil according to the residual amount of each heavy metal ion with the risk label and the corresponding complexing ratio, and returning to S3; S9: obtaining the current content of potassium sulfate in the soil according to the current content of the fulvic acid type potassium sulfate fertilizer; S10: determining whether the current content of potassium sulfate falls within the demand interval, if yes, ending the current heavy metal pollution control, otherwise, performing nutrient adjustment on the soil according to the current content of potassium sulfate.

[0006] Further, the heavy metal pollution control method further includes: S11: collecting a second soil sample from any sampling unit, and extracting a plurality of complexes and a plurality of components from the second soil sample; the components include: mineral matter and organic matter; S12: extracting the initial concentration of each heavy metal ion and the initial concentration of each ligand from any first soil sample; S13: obtaining the decomposition time of each complex; S14: extracting the maximum crop waiting time from the decomposition times of the plurality of complexes; S15: returning to S1 after the waiting time.

[0007] In a second aspect, a heavy metal pollution control system based on fulvic acid type potassium sulfate is provided, comprising: a central processing unit, a first soil detection device, a fertilizer spreading device, and a soil improvement device; the central processing unit is connected with the first soil detection device, the fertilizer spreading device, and the soil improvement device respectively; the first soil detection device is used to obtain the types and contents of heavy metal ions in the soil; the central processing unit comprises: a data acquisition module, which is used to obtain the complexing ratio of each heavy metal ion and fulvic acid; a first data processing module, which is used to obtain the demand amount of fulvic acid corresponding to the complete complexation of all heavy metal ions in the soil according to the content of each heavy metal ion and the corresponding complexing ratio; a second data processing module, which is used to obtain the spreading amount of fulvic acid type potassium sulfate fertilizer according to the demand amount of fulvic acid and the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer; the fertilizer spreading device is used to spread the fulvic acid type potassium sulfate fertilizer uniformly in the soil according to the spreading amount; the central processing unit further comprises: a data recording module, which is used to record the current content of the fulvic acid type potassium sulfate fertilizer in the soil; the first soil detection device is further used to obtain the residual amount of each heavy metal ion after reaching complexation equilibrium with fulvic acid in the soil; the central processing unit further comprises: a first function calling module, which is used to call the first analysis control module for each heavy metal ion; the first analysis control module is used to determine whether the residual amount is greater than the risk screening value of agricultural soil pollution, if yes, control the label adding module and the second analysis control module to work, otherwise, control the third data processing module to work; the label adding module is used to add a risk label to the heavy metal ion; the second analysis control module is used to obtain the demand amount of fulvic acid corresponding to the complete complexation of all heavy metal ions with risk labels in the soil according to the residual amount of each heavy metal ion with a risk label and the corresponding complexing ratio, and sequentially control the second data processing module, the fertilizer spreading device, the data recording module, the first soil detection device, the first analysis control module, and the label adding module to work; the third data processing module is used to obtain the current content of potassium sulfate in the soil according to the current content of the fulvic acid type potassium sulfate fertilizer; the third analysis control module is used to determine whether the content of potassium sulfate falls within the demand interval, if yes, end the current heavy metal pollution control, otherwise, control the soil improvement device to work; the soil improvement device is used to adjust the nutrients of the soil according to the current content of potassium sulfate.

[0008] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0009] 1. The required amount of fulvic acid type potassium sulfate fertilizer is obtained by the type, content and complexing ratio of heavy metal ions in the soil, so as to ensure that the heavy metal ions are effectively complexed; at the same time, the content of potassium ions and sulfate ions in the soil under the complexing balance is considered to affect the soil crops, combined with risk screening value and residual amount analysis, soil nutrient regulation is carried out, so as to avoid the influence of improper content of potassium sulfate on crop growth, realize the synergistic treatment of heavy metal pollution control and soil nutrient balance, and improve the effect of heavy metal pollution control and the stability of soil environment through multiple circulation adjustment of the amount of spreading and nutrient regulation.

[0010] 2. The secondary damage caused by heavy metal ions to the environment after the decomposition of the complex is considered, the decomposition time is obtained through complex decomposition prediction, and the heavy metal ions are controlled regularly according to the decomposition time, so as to prevent the reactivation of heavy metal ions. BRIEF DESCRIPTION OF DRAWINGS

[0011] The drawings described herein are used to provide further understanding of the embodiments of the present application, constitute a part of the present application, and do not constitute a limitation on the embodiments of the present application. In the drawings:

[0012] Figure 1 A heavy metal pollution control method based on fulvic acid type potassium sulfate is provided for the embodiment 1 of the present application. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the present application is further described in detail below, the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not limit the present application, the following described embodiments are part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0014] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application does not have to be implemented with these specific details. In other embodiments, in order to avoid confusion of the present application, well-known structures, materials or methods are not specifically described. The materials, instruments and reagents used in the following embodiments, etc. can be obtained from commercial channels if not otherwise specified. The technical means used in the embodiments, if not otherwise specified, are conventional means known to those skilled in the art.

[0015] In addition, the terms "first", "second", etc. are used only for descriptive purposes and should not be construed as implying or suggesting relative importance or an indicated number of the technical features. Thus, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0016] Embodiment 1: A heavy metal pollution control method based on fulvic acid type potassium sulfate is proposed, which includes Figure 1 The following steps are shown:

[0017] S1: Obtain the types of heavy metal ions in the soil, the content of each heavy metal ion, and the complexing ratio of each heavy metal ion to fulvic acid.

[0018] S2: According to the content of each heavy metal ion and the corresponding complexing ratio, obtain the corresponding fulvic acid demand amount for complete complexation of all heavy metal ions in the soil.

[0019] S3: According to the fulvic acid demand amount and the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer, obtain the spreading amount of the fulvic acid type potassium sulfate fertilizer.

[0020] The following explains S1 to S3:

[0021] Fulvic acid type potassium sulfate is a new type of high-efficiency fertilizer, which is a fertilizer with potassium sulfate as the main component and added fulvic acid or potassium fulvate. Among them, fulvic acid has a complex functional group structure, such as carboxyl and hydroxyl groups. These functional groups can adsorb and complex with heavy metal ions, fixing heavy metal ions in the soil, reducing their activity and mobility in soil solution, and thus reducing the possibility of heavy metal being absorbed by crops. Potassium sulfate can provide potassium and sulfur elements for crops, promote crop growth and development, enhance crop stress resistance, and improve crop quality.

[0022] The purpose of the present method is to control heavy metal pollution by applying fulvic acid type potassium sulfate fertilizer to the soil and using the fulvic acid therein to complex with heavy metal ions in the soil. However, excessive application of fulvic acid type potassium sulfate fertilizer can cause soil compaction and antagonism between various nutrients in the soil, and insufficient application of fulvic acid type potassium sulfate fertilizer can result in residual heavy metal ions in the soil, failing to achieve good heavy metal control effect. Therefore, it is necessary to accurately control the amount of fulvic acid type potassium sulfate fertilizer applied to the soil. The present method is realized by reverse calculation, and the specific implementation is as follows:

[0023] First, obtain the types of heavy metal ions in the soil, the content of each heavy metal ion, and the complexing ratio of each heavy metal ion to fulvic acid.

[0024] It is the premise to accurately calculate the amount of fulvic acid required to completely complex all heavy metal ions to determine the content of different heavy metal ions in the soil and their complexing ratio with fulvic acid. For example, if the soil contains lead ions and cadmium ions, and the content of lead ions is X mol, and the complexing ratio is 1:1; the content of cadmium ions is Y mol, and the complexing ratio is 1:2, then according to these data, the amount of fulvic acid required to complex lead ions and cadmium ions is X mol and 2Y mol respectively, and the amount of fulvic acid required to completely complex all heavy metal ions in the soil is obtained. The method uses experimental determination to obtain the type and content of each heavy metal ion in the soil. Specifically, the following steps are included:

[0025] S1.1: Divide the target area into multiple sampling units.

[0026] The 3D radar scan image of the target area can be obtained by radar scanning, and the 3D radar scan image is imported into the image processing software (QGIS or ArcGISPro). The 3D radar scan image is converted to raster format using the image processing software. The part corresponding to the target area is cut from the 3D radar scan image after format conversion, and the target area refers to the area of the soil that needs to be controlled for heavy metal pollution. In the image processing software, use the "create grid" tool to generate a regular grid, and set the size of the grid according to actual needs (for example, 10m x 10m), and one grid corresponds to one sampling unit. The generated grid is cut to the boundary of the target area.

[0027] S1.2: Obtain the coverage area and average soil thickness of each sampling unit.

[0028] (1) Calculate the coverage area

[0029] Extract the elevation information of the soil surface from the 3D radar scan image (this can be done by using the raster calculator, for example, using the "raster calculator" tool in QGIS). For each grid, calculate its projection area on the horizontal plane (in QGIS, a new field can be added to store the area of each grid using the "field calculator").

[0030] (2) Calculate the average soil thickness

[0031] Extract the soil depth information from the 3D radar scan image (this can be done by using the raster calculator, for example, using the "raster calculator" tool in QGIS). For each grid, calculate the average value of the soil depth of all pixel points inside it (in QGIS, the "raster statistics" tool can be used to calculate the average value of each grid).

[0032] S1.3: Collect a first soil sample from each sampling unit, and detect the soil density of each first soil sample.

[0033] (1) Collecting soil samples

[0034] Soil samples can be collected using a soil auger or a shovel, placing the collected soil samples into sampling bags, and recording the sampling point number.

[0035] (2) Detecting soil density

[0036] Place the collected soil samples in the laboratory in order of the number. Put the soil samples into a drying oven, set the temperature to 105-110 degrees Celsius, and dry for 24 hours to remove the moisture in the soil. Grind the dried soil samples into fine powder and sieve through a 2-millimeter sieve to remove larger particles and impurities. Weigh the mass of the sieved soil samples using a balance and record the mass of each sample. Insert a cutting ring vertically into the soil and collect a complete soil column sample, ensuring that the soil in the cutting ring is tight and has no gaps. Weigh the cutting ring and soil together and record the total mass M1. Remove the soil from the cutting ring and weigh the mass of the empty cutting ring M2. Calculate the mass of the soil M = M1 - M2. The soil density p = VM, where V is the volume of the cutting ring (100 cubic centimeters).

[0037] S1.4: Extract heavy metal ions from each first soil sample and analyze the content of heavy metal ions to obtain detection data for each first soil sample.

[0038] The detection data includes: the amount of substance of each heavy metal ion in unit mass of soil.

[0039] The specific implementation of S1.4 is detailed in steps A1 to A3.

[0040] Step A1: Extract heavy metal ions in the first soil sample into a solution.

[0041] Use the extraction method to extract heavy metal ions - accurately weigh a certain amount of dry soil sample (such as 1.0 grams) using a balance. Place the weighed soil sample in a beaker and add an appropriate amount of extractant (such as 10 milliliters of aqua regia or nitric acid). Place the beaker on an electric heating plate and slowly heat it to a slight boil, maintaining the slight boil for about 1 hour to allow the heavy metal ions in the soil to fully dissolve into the solution. Cool the solution to room temperature, filter with filter paper, and remove the insoluble residue.

[0042] Step A2: Determine the type of heavy metal ions in the solution and the concentration of each heavy metal ion.

[0043] Atomic Absorption Spectrometry (AAS) - The sample extract is diluted to a certain volume (e.g. 10 mL) with a diluent (e.g. 1% nitric acid solution). The diluted solution is filtered through a 0.45 micron filter membrane. The diluted sample is fed into the atomizer of the AAS through a sample injector to measure the intensity of light absorbed at a specific wavelength, identify the type of heavy metal ion in the solution, and determine the concentration of each heavy metal in the solution. The wavelength and absorption intensity of each heavy metal ion are recorded. The detected absorption intensity is matched with the standard curve to determine the type of heavy metal ion and the concentration of each heavy metal ion in the solution.

[0044] Step A3: Perform steps A31 to A32 for each heavy metal ion.

[0045] Step A31: Convert the concentration to the amount-of-substance concentration.

[0046] Find the molar mass of the heavy metal ion. For example, the molar mass of lead (Pb) is 207.2 g / mol, and the molar mass of cadmium (Cd) is 112.4 g / mol. Convert the mass concentration (mg / L) to g / L, i.e. mass concentration (g / L) = mass concentration (mg / L) ÷ 1000. Calculate the amount-of-substance concentration, i.e. amount-of-substance concentration (mol / L) = mass concentration (g / L) ÷ molar mass (g / mol). For example, the mass concentration of lead (Pb) in a certain solution is measured to be 50 mg / L, and the molar mass is 207.2 g / mol. Convert the mass concentration (mg / L) to g / L, i.e. mass concentration (g / L) = 50 (mg / L) ÷ 1000 = 0.05 g / L. Calculate the amount-of-substance concentration, i.e. amount-of-substance concentration (mol / L) = 0.05 g / L ÷ 207.2 g / mol = 0.000241 mol / L.

[0047] Step A32: Obtain the amount of substance of the heavy metal ion per unit mass of soil according to the soil density, molar mass, and amount-of-substance concentration.

[0048] The amount of substance per unit mass of soil = C x V ÷ m. Where C is the amount-of-substance concentration (mol / L), V is the volume of the solution (L), and m is the mass of the soil (g / kg). V = m ÷ p, where p is the density of the soil (kg / m³). For example, the soil density is 1.5 g / cm³ (or 1500 kg / m³), and the amount-of-substance concentration of the heavy metal ion is 0.000241 mol / L. Then, the amount of substance per unit mass of soil = 0.00024 (mol / L) ÷ 1.5 (g / cm³) = 0.00016067 mol / g.

[0049] S1.5: Obtain the amount of substance of each heavy metal ion in each sampling unit according to the detection data.

[0050] The specific implementation of S1.5 is described in steps B1 to B2.

[0051] Step B1: Obtain the soil quality of the sampling unit according to the coverage area, soil density, and average soil thickness.

[0052] Step B2: Obtain the amount of substance of each heavy metal ion in the sampling unit according to the detection data and the soil quality of the sampling unit.

[0053] According to the detected amount of substance concentration and the soil quality of the sampling unit, the total amount of substance of each heavy metal ion in the sampling unit is calculated, and the calculation formula is N = C x M, where N is the total amount of substance of heavy metal ions in the sampling unit (mol), C is the amount of substance concentration of heavy metal ions (mol / kg or mol / g), and M is the soil quality of the sampling unit. For example, the amount of substance concentration of heavy metal ions C = 0.00016067 mol / g, and the soil quality of the sampling unit M = 1000 g, then the total amount of substance of heavy metal ions in the sampling unit N = 0.00016067 mol / g x 1000 g = 0.16067 mol.

[0054] S1.6: Sum the amount of substance of each heavy metal ion in each sampling unit to obtain the content of each heavy metal ion in the soil of the target area.

[0055] Then, according to the content of each heavy metal ion and the corresponding complexing ratio, the demand for fulvic acid corresponding to the complete complexation of all heavy metal ions in the soil is obtained.

[0056] The demand for fulvic acid corresponding to the complete complexation of all heavy metal ions in the soil, i.e. the amount of substance of fulvic acid required for the complete complexation of all heavy metal ions in the soil, is the product of the amount of substance of heavy metal ions and the complexing ratio.

[0057] Finally, according to the demand for fulvic acid and the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer, the spreading amount of the fulvic acid type potassium sulfate fertilizer is obtained.

[0058] The demand for fulvic acid and the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer refer to the mass percentage of fulvic acid in the fulvic acid type potassium sulfate fertilizer. Under the premise of calculating the demand for fulvic acid, the spreading amount of the fulvic acid type potassium sulfate fertilizer = demand for fulvic acid ÷ mass percentage.

[0059] Through the above S1 to S3, the amount of fulvic acid type potassium sulfate fertilizer required to be completely complexed in theory can be accurately calculated. On this basis, the following steps are performed:

[0060] S4: The fulvic acid type potassium sulfate fertilizer is evenly spread in the soil according to the spreading amount, and the current content of the fulvic acid type potassium sulfate fertilizer in the soil is recorded.

[0061] After S4, the fulvic acid begins to complex with various heavy metal ions in the soil. However, the spreading amount of the fulvic acid type potassium sulfate fertilizer calculated through S1 to S3 is the theoretical value. On the one hand, the complexation reaction is a reversible process, which follows the principle of chemical equilibrium, and according to Le Chatelier's principle, even if the amount of fulvic acid is increased, it can only move the equilibrium to the direction of generating complex, but cannot completely convert the heavy metal ions into complex, and a certain amount of heavy metal ions will inevitably remain. On the other hand, due to the complex structure of the soil, the mineral matter, organic matter and other components in the soil will compete with the heavy metal ions for the complexation sites of the fulvic acid. For example, the clay minerals in the soil have electric charges on their surfaces, which can adsorb heavy metal ions, and part of the heavy metal ions adsorbed by the clay minerals are difficult to fully contact with the fulvic acid to occur complexation reaction, resulting in the remaining of part of the heavy metal ions. Moreover, the pH value and oxidation-reduction potential of the soil also affect the progress of the complexation reaction. In acidic soil, the concentration of hydrogen ions is high, which competes with the heavy metal ions for the active groups on the fulvic acid, inhibits the complexation reaction, and makes more heavy metal ions remain. Therefore, after S1 to S4, the heavy metal ions in the soil cannot be completely complexed, and further control of the heavy metal ions in the soil is needed through the following steps. Specifically as follows:

[0062] S5: Obtain the residual amount of each heavy metal ion in the soil after reaching complexation equilibrium with the fulvic acid.

[0063] The present method predicts the residual amount of each heavy metal ion in the soil after reaching complexation equilibrium with the fulvic acid through experimental detection and numerical fitting. Specifically, the following steps are included:

[0064] S5.1: Extract a unit mass of soil sub-sample from each of the first soil samples.

[0065] S5.2: Obtain the amount of fulvic acid added to each soil sub-sample to completely complex all heavy metal ions according to the detection data and the corresponding complexation ratio.

[0066] The amount of fulvic acid added in this step refers to the amount of fulvic acid that needs to be added to completely complex all heavy metal ions in a unit mass of soil sub-sample. Since the detection data includes the amount of substance of each heavy metal ion in a unit mass of soil, by multiplying the amount of substance of each heavy metal ion in a unit mass of soil with the corresponding complexation ratio of each heavy metal ion, the amount of fulvic acid added to each soil sub-sample to completely complex all heavy metal ions can be obtained.

[0067] S5.3 Obtain the amount of the fulvic acid type potassium sulfate fertilizer according to the amount of the fulvic acid and the content of the fulvic acid in the fulvic acid type potassium sulfate fertilizer.

[0068] Refer to S3.

[0069] S5.4: Set multiple test time points.

[0070] Respectively experimentally determine the time required for the complexation reaction of different heavy metal ions (such as lead, cadmium, copper, zinc, etc.) and fulvic acid to reach equilibrium and the residual amount. Set multiple test time points, such as 15 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, 8 hours, 12 hours, 24 hours, etc. Determine the amount of heavy metal ions at each test time point until the amount of heavy metal ions no longer changes. The corresponding time is the maximum length of the complexation reaction, and the final measured concentration of heavy metal ions is the residual amount.

[0071] S5.5: Obtain the residual amount of each heavy metal ion in each soil sub-sample.

[0072] The specific implementation of S5.5 is detailed in steps C1 to C3.

[0073] Step C1: Mix the soil sub-sample and the fulvic acid type potassium sulfate fertilizer with the same amount of the added amount in the reaction dish.

[0074] Step C2: At each test time point, determine and record the concentration of each heavy metal ion in the reaction dish.

[0075] Refer to step A2.

[0076] Step C3: Plot the complexation reaction curve of each heavy metal ion with time as the horizontal coordinate and the concentration of heavy metal ions as the vertical coordinate.

[0077] Organize the concentration data of each heavy metal ion measured at different time points to establish a data table. The first column of the table records the time, and each subsequent column corresponds to the concentration data of one heavy metal ion. Use professional drawing software (such as Origin, Excel, etc.) to establish a coordinate system with time as the horizontal coordinate and the concentration of heavy metal ions as the vertical coordinate. Organize the data in the form of scattered points in the coordinate system, and each time point corresponds to a scattered point of the concentration of heavy metal ions. Use the curve fitting function of the drawing software or manually draw the curve to connect the scattered points into a smooth curve.

[0078] Step C4: Obtain the vertical coordinate corresponding to the point with a slope of zero on the complexation reaction curve of each heavy metal ion to obtain the residual amount of each heavy metal ion.

[0079] In the initial stage of the reaction, the reaction proceeds rapidly in the direction of forming the complex due to the high concentration of fulvic acid and heavy metal ions, at this time the concentration of heavy metal ions decreases rapidly, and the complexation reaction curve has a large slope. As the reaction continues, fulvic acid and heavy metal ions continuously combine to form complexes, their concentration gradually decreases, the reaction rate also gradually slows down, and the curve slope gradually becomes smaller. When the reaction reaches equilibrium, the forward and reverse reaction rates are equal, and the concentrations of various substances in the system no longer change. At this time, the slope of the complexation reaction curve is zero. Therefore, the vertical coordinate corresponding to the point on the complexation reaction curve with a slope of zero is the concentration of the heavy metal ion after the complexation reaction reaches equilibrium.

[0080] S5.6: Obtain the residual amount of each heavy metal ion in each sampling unit according to the soil quality of the sampling unit and the residual amount of each heavy metal ion in the soil sub-sample.

[0081] Refer to step B2.

[0082] S5.7: Sum the residual amount of each heavy metal ion in each sampling unit to obtain the residual amount of each heavy metal ion in the soil of the target area after the complexation equilibrium with fulvic acid is reached.

[0083] Refer to S1.6.

[0084] S6: Perform S7 for each heavy metal ion.

[0085] S7: Determine whether the residual amount is greater than the agricultural soil pollution risk screening value. If yes, add a risk label to the heavy metal ion and perform S8, otherwise, perform S9.

[0086] China has clear reference standards for whether the content of heavy metals in soil exceeds the standard, mainly based on the "Soil Environmental Quality Agricultural Soil Pollution Risk Control Standard (Trial)" (GB15618-2018). When the content of heavy metals in soil is equal to or less than the risk screening value, the soil pollution risk is low; when the content of heavy metals in soil is higher than the risk screening value but lower than the risk control value, there may be a risk of soil pollution; when the content of heavy metals in soil is higher than the risk control value, in principle, safety utilization measures should be taken. According to the above reference standard, only when the content of heavy metals in soil is less than or equal to the agricultural soil pollution risk screening value, can it be determined that the content of heavy metals in soil meets the standard. Therefore, in this method, the residual amount of each heavy metal ion is compared with the corresponding agricultural soil pollution risk screening value to determine whether the residual amount is greater than the agricultural soil pollution risk screening value. If yes, add a risk label to the heavy metal ion, and the content of the heavy metal ion with a risk label exceeds the standard. Then perform S8.

[0087] S8: According to the residual amount of each heavy metal ion with a risk label and the corresponding complexing ratio, obtain the demand amount of fulvic acid corresponding to the complete complexing of all heavy metal ions with a risk label in the soil, and return to S3.

[0088] The purpose of this step is to obtain the amount of fulvic acid required to be completely complexed in theory according to the content of each heavy metal ion exceeding the standard in the soil, that is, the amount of fulvic acid that needs to be continuously added to the soil. After obtaining the amount of fulvic acid that needs to be continuously added, further control the content of heavy metal ions in the soil by spreading fulvic acid type potassium sulfate fertilizer according to the above method, and detect whether the content of heavy metal ions in the soil exceeds the standard after further implementing the control measures, and so on, until the content of heavy metal ions in the soil reaches the national standard.

[0089] S9: Obtain the current content of potassium sulfate in the soil according to the current content of fulvic acid type potassium sulfate fertilizer.

[0090] After S7 and S8, the residual amount of each heavy metal ion in the soil is less than or equal to the agricultural soil pollution risk screening value, indicating that the content of heavy metals in the soil has reached the national standard. However, after adding fulvic acid type potassium sulfate fertilizer for many times, the content of potassium sulfate in the soil may still be insufficient or the content of potassium sulfate in the soil may have exceeded. Whether the content of potassium sulfate in the soil is insufficient or exceeds the standard may have a series of adverse effects on the soil environment and crop growth, for example: (1) Sulfate ions (SO4²⁻) react with water in the soil to generate sulfuric acid (H2SO4), causing soil acidification; (2) Excessive sulfur will have antagonistic effect with other nutrients (such as calcium, magnesium, potassium, etc.), affecting the absorption of these nutrients by crops. Insufficient sulfur in the soil may lead to insufficient supply of sulfur to plants, affecting the growth and development of plants. Further, excessive potassium and sulfur in the soil will also have adverse effects on crop growth and soil health, for example: (1) Excessive potassium in the soil will have ion antagonistic effect with other cations (such as calcium, magnesium, etc.), affecting the absorption of these elements by crops, leading to symptoms of calcium, magnesium and other element deficiency in crops. (2) Insufficient potassium in the soil affects crop growth. Therefore, it is necessary to obtain the current content of potassium sulfate in the soil to further determine whether the current content of potassium sulfate meets the crop growth.

[0091] S10: Determine whether the current content of potassium sulfate falls within the demand interval. If yes, end the current heavy metal pollution control, otherwise, adjust the nutrients in the soil according to the current content of potassium sulfate.

[0092] The requirement interval refers to the adaptive interval of the demand of potassium sulfate in the soil for crops in different growth stages. If the current content of potassium sulfate falls within the requirement interval, it means that the nutrients in the soil are suitable for the growth of crops. Otherwise, nutrient adjustment needs to be made to the soil according to the current content of potassium sulfate. It should be noted that the premise of S10 is that after S7 and S8, the heavy metal ions in the soil have reached the national detection standard through complexation reaction.

[0093] To know how to make nutrient adjustment to the soil according to the current content of potassium sulfate, first of all, the amount of potassium and the amount of sulfur required for the normal growth of crops need to be known, which correspond to the amount of potassium ions and the amount of sulfate ions required for the growth of crops. This method is realized by simulation using the QUEFTS model. The QUEFTS model, i.e., the quantitative evaluation of soil fertility model, can predict crop yield by analyzing soil chemical properties and crop fertilizer requirement characteristics, and then evaluate soil fertility to guide fertilization decision-making. The QUEFTS model is used to simulate the demand interval of potassium ions and sulfate for crops in different stages, and the specific implementation is to perform the following steps before S10:

[0094] Obtain multiple potassium ion requirements and multiple sulfate ion requirements of crops in each growth stage. Specifically, it includes steps D1 to D4.

[0095] Step D1: Determine the physicochemical characteristic parameters of the first soil sample.

[0096] The physicochemical characteristic parameters include: initial potassium ion content, initial sulfate ion content, multiple macroelement content, multiple microelement content, pH value, oxidation-reduction potential, cation exchange capacity, and organic matter content. These data are the basis for understanding the soil fertility status and can provide a basis for subsequent calculation of the amount of potassium ions and sulfate ions that can be absorbed by crops.

[0097] The pH value of the soil can be measured using the potentiometric method to understand the soil acidity and alkalinity and provide a basis for reasonable fertilization and soil improvement. The soil organic matter content can be determined by the potassium dichromate oxidation method. Organic matter affects soil fertility, soil water and fertilizer retention capacity, and microbial activity. The soil nutrient content, including macroelements (nitrogen, phosphorus) and microelements (iron, zinc, manganese, etc.), is analyzed. The Kjeldahl method is used to determine the total nitrogen content, and the sodium bicarbonate extraction-molybdenum antimony anti-colorimetric method is used to determine the available phosphorus. When analyzing microelements, atomic absorption spectrometry, inductively coupled plasma mass spectrometry, etc. are commonly used.

[0098] Step D2: Obtain the growth characteristic parameters and ion absorption characteristic parameters of the crop through web crawling.

[0099] The growth characteristic parameters include the growth duration of each growth stage and the growth rate of each growth stage, and the ion absorption characteristic parameters include the potassium ion absorption rate, the potassium ion accumulation amount, the sulfate ion absorption rate, and the sulfate ion accumulation amount. These characteristic parameters help to clarify the demand characteristics of the target crop for potassium elements at different growth stages. For example, some crops mainly demand potassium for the growth of roots and stems and leaves in the early growth stage, and more for the development of fruits or seeds in the later stage.

[0100] The data source of the web crawler can be a website of an agricultural research institution, which publishes crop planting and growth research results, including detailed data for each stage of crop growth. For example, the website of the relevant research institute of the Chinese Academy of Agricultural Sciences publishes research reports on a variety of crops, covering crop growth characteristic parameters. Academic databases such as CNKI and Web of Science contain a large number of academic papers in the field of agriculture, including research papers on crop growth and element absorption, from which key parameters can be extracted by a crawler.

[0101] In addition, the growth characteristic parameters of crops can also be obtained by direct measurement method (using a ruler, caliper, etc. to directly measure the morphological indicators of crops such as plant height, stem diameter, leaf length and width), image analysis method (using a camera or other imaging equipment to obtain images of crops, and analyzing the morphological characteristics of crops such as crown width, plant height, leaf number, and leaf area index through image processing software), sensor monitoring method (using sensors to monitor the physiological state of crops and environmental parameters, and then obtaining relevant growth characteristic parameters), and solution culture method (planting crops in nutrient solution containing known ion concentration, and calculating the ion absorption amount of crops by regularly measuring the change of ion concentration in the nutrient solution), ion selective electrode method (using ion selective electrode to measure the activity or concentration of specific ions in the solution), and isotope tracing method (using radioactive or stable isotope labeled ions, adding them to the environment of crop growth, and then detecting the absorption, distribution and accumulation of isotopes in different parts of crops to study the absorption, transport and distribution rules of ions by crops).

[0102] Step D3: setting target yield and climate parameters.

[0103] The target yield is determined according to actual demand. The climate parameters include temperature, precipitation and light duration, which are determined according to the actual situation of local climate.

[0104] Step D4: using the QUEFTS model to analyze the physicochemical characteristic parameters, growth characteristic parameters, ion absorption characteristic parameters, target yield and climate parameters, and obtaining the potassium ion demand and sulfate ion demand of crops at each generation stage.

[0105] The QUEFTS model is based on a large amount of experimental data and theoretical research, and establishes a mathematical relationship between soil parameters, crop growth stages, yield targets and potassium element absorption. The physical and chemical characteristic parameters, growth characteristic parameters, ion absorption characteristic parameters, target yield and climate parameters are input into the QUEFTS model, and the QUEFTS model outputs the absorption amounts of potassium ions and sulfate ions at each stage of the crop through calculation on the input data.

[0106] The maximum and minimum values are extracted from the plurality of potassium ion demand amounts to obtain a demand interval of potassium ions; and the maximum and minimum values are extracted from the plurality of sulfate ion demand amounts to obtain a demand interval of sulfate ions.

[0107] On the basis of obtaining the amount of potassium ions and the amount of sulfate ions required for crop growth, S10 judges whether the current content of potassium ions and the current content of sulfate ions in the soil meet the normal growth demand of the crop based on the demand amount of potassium ions and the demand amount of sulfate ions. If excessive or insufficient, the nutrients in the soil are adjusted accordingly to meet the growth demand of the crop. The specific method is:

[0108] S10.1: According to the current content of potassium sulfate and the proportion of potassium ions in potassium sulfate, the current content of potassium ions is obtained; and according to the current content of potassium sulfate and the proportion of sulfate ions in potassium sulfate, the current content of sulfate ions is obtained.

[0109] S10.2: Judge whether the current content of potassium ions and the current content of sulfate ions are both within the corresponding demand interval, if yes, end the current heavy metal pollution control, otherwise, add fertilizer or exchange resin according to the content of potassium ions and the content of sulfate ions.

[0110] Specifically includes the following steps:

[0111] S10.2.1: Judge whether the current content of potassium ions and the current content of sulfate ions are both within the corresponding demand interval, if yes, end the current heavy metal pollution control, otherwise, judge whether the current content of potassium ions and the current content of sulfate ions are both not within the demand interval of potassium ions, if yes, execute S10.2.2 to S10.2.3, otherwise, judge whether the current content of potassium ions is not within the demand interval of potassium ions, if yes, execute S10.2.4, otherwise, execute S10.2.5.

[0112] S10.2.2: Judge whether the current content of potassium ions is on the left side of the demand interval, if yes, add potassium fertilizer to the soil according to the current content of potassium ions, otherwise, add cation exchange resin to the soil according to the current content of potassium ions.

[0113] S10.2.3: judging whether the current content of sulfate ion is located at the left side of the demand interval, if yes, adding sulfate fertilizer into the soil according to the current content of sulfate ion, otherwise, adding anion exchange resin into the soil according to the current content of sulfate ion.

[0114] S10.2.4: performing S10.2.1.

[0115] S10.2.5: performing S10.2.2.

[0116] It should be noted that: (1) if the current content of potassium ion and the current content of sulfate ion are both within the corresponding demand interval, it means that the current content of potassium ion and the current content of sulfate ion in the soil both meet the requirements for normal growth, and there will be no potassium ion deficiency affecting crop growth and potassium ion excess causing ion antagonism with other cations in the soil, and there will also be no sulfate ion content deficiency leading to insufficient supply of sulfur elements to plants and excessive sulfate ion leading to soil alkali and antagonism with other nutrients. At this time, the heavy metal ions in the soil have been complexed with fulvic acid, the content has reached the national detection standard, and the content of potassium ion and the content of sulfate ion both meet the requirements for normal growth of crops, so the synergy of soil nutrient demand and heavy metal pollution control is achieved, and the heavy metal pollution control is completed while ensuring the normal growth of crops. (2) If the current content of potassium ion and the current content of sulfate ion are not both within the corresponding demand interval, there are three cases. The first case is that the current content of potassium ion and the current content of sulfate ion are both not within the corresponding demand interval; the second case is that the current content of potassium ion is not within the corresponding demand interval, while the current content of sulfate ion is within the corresponding demand interval; the third case is that the current content of potassium ion is not within the corresponding demand interval, while the current content of sulfate ion is within the corresponding demand interval. The three cases need to be judged separately.

[0117] Further, for the first case, if the current content of potassium ion and the current content of sulfate ion are both not within the corresponding demand interval, it is further judged whether the current content of potassium ion is insufficient (located at the left side of the demand interval) or the current content of potassium ion is excessive (located at the right side of the demand interval), i.e. corresponding to the second case described above; and it is further judged whether the current content of sulfate ion is insufficient (located at the left side of the demand interval) or the current content of sulfate ion is excessive (located at the right side of the demand interval), i.e. corresponding to the third case described above.

[0118] Further, for the case of insufficient current content of potassium ion, potassium fertilizer needs to be added into the soil according to the current content of potassium ion. The amount of potassium fertilizer added can be determined by referring to the following method:

[0119] First, a first difference between the current content of potassium ions and the lower limit of the demand interval is obtained, and a second difference between the current content of potassium ions and the upper limit of the demand interval is obtained.

[0120] Then, the supplement of potassium ions is determined according to the first difference and the second difference. For example, the supplement of potassium ions = (first difference + second difference) ÷ 2. The purpose is to make the current content of potassium ions after supplementing located in the corresponding demand interval.

[0121] Finally, the amount of potassium fertilizer to be supplemented is determined according to the supplement of potassium ions and the proportion of potassium ions in potassium fertilizer.

[0122] Further, for the case that the current content of potassium ions is excessive, cation exchange resin needs to be added to the soil according to the current content of potassium ions. The cation exchange resin is used to adsorb potassium ions in the soil to reduce its antagonism to other cations. The amount of cation exchange resin added can be determined by the following method:

[0123] First, the absorption amount of potassium ions is obtained according to the first difference and the second difference. For example, the absorption amount of potassium ions = (first difference + second difference) ÷ 2. The purpose is to make the current content of potassium ions after absorption located in the corresponding demand interval.

[0124] Then, the adsorption efficiency of cation exchange resin to potassium ions is obtained by web crawler.

[0125] Finally, the amount of cation exchange resin added is calculated according to the formula R = K × M ÷ E. Wherein, R represents the amount of cation exchange resin added, K represents the amount of potassium ions to be absorbed in unit mass of soil, M represents the mass of soil, and E represents the absorption efficiency of cation exchange resin to potassium ions.

[0126] Further, for the case that the current content of sulfate ions is insufficient, sulfate fertilizer needs to be added to the soil according to the current content of sulfate ions. The amount of sulfate fertilizer added can refer to the determination method of the amount of potassium fertilizer added.

[0127] Further, for the case that the current content of sulfate ions is excessive, anion exchange resin needs to be added to the soil according to the current content of sulfate ions. The anion exchange resin is used to adsorb sulfate ions in the soil. Anion exchange resin is a kind of high molecular material with ion exchange function, which can adsorb and exchange anions. The amount of anion exchange resin added can refer to the determination method of the amount of cation exchange resin added.

[0128] Up to S1-S10, the heavy metal pollution control is completed, and the soil nutrient demand and heavy metal pollution control are achieved. However, under the conditions of soil environment (pH, oxidation-reduction point and temperature), microbial action and competition of other substances, the complex in the soil will decompose into heavy metal ions, ligands and new compounds. After decomposition, the heavy metal ions will be released into the soil again, causing secondary pollution. Therefore, after S10, the content of heavy metal ions needs to be detected within a specified time. If the content of heavy metal ions exceeds the national detection standard, the method of S1-S10 needs to be used for heavy metal pollution control. The method uses model simulation to detect the content of heavy metal ions in the soil after the decomposition of the complex. The specific method is as follows:

[0129] S11: Collect a second soil sample from any sampling unit, and extract a plurality of complexes and a plurality of components from the second soil sample.

[0130] The components refer to various minerals and various organic matters in the soil.

[0131] (1) Complex extraction

[0132] Chemical reagent extraction method is used to extract the complex. 0.05 mol / L EDTA (ethylenediaminetetraacetic acid) solution is used as the extracting agent. The second soil sample is placed in a conical flask, and the EDTA solution is added according to the ratio of soil to extracting agent 1:5-1:10 (mass ratio), then the conical flask is placed on a shaker, and shaken at a certain temperature (such as 25°C) and shaking speed (such as 150-200 r / min) for 1-3 hours. After shaking, the sample is centrifuged (usually at a speed of 3000-5000 r / min for 10-15 minutes), and the supernatant is taken to obtain the extracting solution containing metal-organic complex. For some specific complexes, chelating agents can also be used for extraction, such as DTPA (diethylenetriaminepentaacetic acid) for extracting effective state zinc, iron, manganese and other metal complexes in the soil.

[0133] (2) Mineral extraction

[0134] Acid dissolution method is used to extract minerals. The second soil sample is placed in a polytetrafluoroethylene crucible, and hydrofluoric acid and perchloric acid are added. The soil is carbonized and decomposed on an electric heating plate at a low temperature (the initial temperature is about 100-120°C), and then gradually heated to 200-250°C until white smoke of perchloric acid is generated, so that the soil is completely digested. After cooling, the residue is dissolved with dilute hydrochloric acid and transferred to a volumetric flask for constant volume to obtain a solution containing mineral components. The types and contents of minerals in the solution can also be determined by atomic absorption spectrometry, and the operation method of A2 or D2 in the above steps is referred to, which is not repeated here.

[0135] (3) Organic matter extraction

[0136] The organic matter was extracted by potassium dichromate oxidation method. The second soil sample was placed in a test tube, and a known concentration of potassium dichromate solution and concentrated sulfuric acid were added. The test tube was heated to boiling at 170-180°C for 5 minutes. After the test tube was cooled, the solution was transferred to a conical flask. The residual potassium dichromate was titrated with a standard solution of ferrous ammonium sulfate, using eriochrome black T as an indicator. The color of the solution changed from orange yellow to blue green to brick red, which was the end point of titration. The volume of the ferrous ammonium sulfate standard solution consumed was recorded. Based on the blank test (same operation but without adding the solution sample) and the sample titration data, the content of organic matter in the solution was calculated.

[0137] S12: Extract the initial concentration of each heavy metal ion and the initial concentration of each ligand from any first soil sample.

[0138] Refer to step A2 or step D2.

[0139] S13: Obtain the decomposition time of each complex.

[0140] The specific implementation of S13 is detailed in S13.1 to S13.3.

[0141] S13.1: Obtain the thermodynamic characteristic parameters of the complex and the interaction parameters between the complex and each component through web crawling.

[0142] The thermodynamic parameters include composition, structure, stability constant, and dissociation constant.

[0143] Interaction parameters reflect the degree of deviation from the ideal state when two or more substances interact, which can help scientists more accurately understand and predict the behavior of substances in complex systems. For example, in the study of the interaction between the complex and the soil, the interaction parameters can reflect the comprehensive influence of factors such as the strength of the combination, the size of the affinity, and the steric hindrance between the complex and the soil mineral surface, organic matter, etc. The interaction parameters between the complex and each component include thermodynamic interaction parameters, kinetic interaction parameters, and structural interaction parameters.

[0144] The data source of the web crawler can be academic databases such as the Web of Science, CNKI, etc., which have collected a large number of research literature in the fields of chemistry and materials science, containing a large amount of thermodynamic parameters of complexes and interaction parameters between each component in the soil. In addition, professional chemical websites such as the American Chemical Society (ACS) website and the German Chemical Society (GDCh) website also publish chemical data information.

[0145] In addition, the thermodynamic characteristic parameters and the interaction parameters of the complex and each component can also be determined by experimental methods such as calorimetry (obtaining thermodynamic parameters by measuring heat changes during the complexation reaction) and spectroscopy (obtaining thermodynamic parameters by studying the structure and composition of the complex using spectroscopic techniques).

[0146] S13.2: Analyzing the physicochemical characteristic parameters of the soil, the initial concentration of each heavy metal ion, the initial concentration of each ligand, the thermodynamic characteristic parameters of the complex, and the interaction parameters of the complex and each component by using the PHREEQC model to obtain the decomposition curve of the complex concentration over time.

[0147] PHREEQC comes with a variety of thermodynamic databases, such as phreeqc.dat. These databases contain thermodynamic data for various chemical substances, such as standard free energy of formation, enthalpy, entropy, etc., which are used to calculate the equilibrium constant and Gibbs free energy change of reactions. By inputting the physicochemical characteristic parameters of the soil, the initial concentration of each heavy metal ion, the initial concentration of each ligand, the thermodynamic characteristic parameters of the complex, and the interaction parameters of the complex and each component into the PHREEQC model, the PHREEQC model will calculate the chemical equilibrium between the complex and other ions in the soil solution under given soil conditions based on the input parameters and thermodynamic data. The calculation results include the equilibrium concentration of the complex, the activity of various ions, the saturation index, and other information. In addition, the PHREEQC model simulates the decomposition process of the complex in the soil over time. The simulation results will give the concentration changes of the complex at different time points, so that the decomposition curve of the complex can be obtained.

[0148] S13.3: Obtaining the abscissa corresponding to the point where the slope of the decomposition curve is zero to obtain the decomposition time of the complex.

[0149] S14: Extracting the maximum value from the decomposition times of multiple complexes as the crop waiting time.

[0150] S15: Returning to S1 after the waiting time.

[0151] In summary, the heavy metal pollution control method based on fulvic acid type potassium sulfate proposed in this embodiment can effectively complex heavy metal ions in the soil by accurately determining the spreading amount of fulvic acid type potassium sulfate fertilizer, and can adjust according to the soil nutrient demand to ensure the health of the soil environment and the growth demand of crops.

[0152] Embodiment 2: Corresponding to embodiment 1, the heavy metal pollution control system based on fulvic acid type potassium sulfate proposed in this embodiment includes a central processing unit, a first soil detection device, a fertilizer spreading device, and a soil improvement device; the central processing unit is connected with the first soil detection device, the fertilizer spreading device, and the soil improvement device respectively.

[0153] The first soil detection device is configured to obtain the types of heavy metal ions and the content of each heavy metal ion in the soil;

[0154] The central processor comprises:

[0155] The data acquisition module is configured to obtain the complexing ratio of each heavy metal ion to fulvic acid;

[0156] The first data processing module is configured to obtain the demand amount of fulvic acid corresponding to the complete complexation of all heavy metal ions in the soil according to the content of each heavy metal ion and the corresponding complexing ratio;

[0157] The second data processing module is configured to obtain the spreading amount of the fulvic acid type potassium sulfate fertilizer according to the demand amount of fulvic acid and the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer;

[0158] The fertilizer spreading device is configured to uniformly spread the fulvic acid type potassium sulfate fertilizer in the soil according to the spreading amount;

[0159] The central processor further comprises:

[0160] The data recording module is configured to record the current content of the fulvic acid type potassium sulfate fertilizer in the soil;

[0161] The first soil detection device is further configured to obtain the residual amount of each heavy metal ion in the soil after reaching the complexing equilibrium with fulvic acid;

[0162] The central processor further comprises:

[0163] The first function calling module is configured to call the first analysis control module for each heavy metal ion;

[0164] The first analysis control module is configured to determine whether the residual amount is greater than the agricultural soil pollution risk screening value, if yes, control the label adding module and the second analysis control module to work, otherwise, control the third data processing module to work;

[0165] The label adding module is configured to add a risk label to the heavy metal ion;

[0166] The second analysis control module is configured to obtain the demand amount of fulvic acid corresponding to the complete complexation of all heavy metal ions with risk labels in the soil according to the residual amount of each heavy metal ion with a risk label and the corresponding complexing ratio, and sequentially control the second data processing module, the fertilizer spreading device, the data recording module, the first soil detection device, the first analysis control module and the label adding module to work;

[0167] The third data processing module is configured to obtain the current content of potassium sulfate in the soil according to the current content of the fulvic acid type potassium sulfate fertilizer;

[0168] A third analysis control module is configured to determine whether the potassium sulfate content falls within a required range. If yes, the current heavy metal pollution control is ended. Otherwise, the soil improvement device is controlled to work.

[0169] The soil improvement device is configured to adjust the soil nutrients according to the current potassium sulfate content.

[0170] Further, the first soil detection device comprises:

[0171] A 3D scanning device is configured to obtain a 3D scanning image of the target area.

[0172] An image processing unit is configured to divide the target area into a plurality of sampling units according to the 3D scanning image, and obtain the coverage area and the average soil thickness of each sampling unit.

[0173] A first sample collection device is configured to collect a first soil sample from each sampling unit.

[0174] A soil density detection device is configured to detect the soil density of each first soil sample, and extract the heavy metal ion species and analyze the heavy metal ion content of each first soil sample to obtain detection data of each first soil sample. The detection data comprises the amount of substance of each heavy metal ion in unit mass of soil.

[0175] A first data processing unit is configured to obtain the amount of substance of each heavy metal ion in each sampling unit according to the detection data.

[0176] A second data processing unit is configured to sum the amount of substance of each heavy metal ion in each sampling unit to obtain the content of each heavy metal ion in the soil of the target area.

[0177] Further, the first soil detection device further comprises:

[0178] A second sample collection device is configured to extract a unit mass of soil sub-sample from each first soil sample.

[0179] A fourth data processing unit is configured to obtain the addition amount of fulvic acid corresponding to the complete complexation of all heavy metal ions in each soil sub-sample according to the detection data and the corresponding complexing ratio, and obtain the addition amount of the fulvic acid type potassium sulfate fertilizer according to the addition amount of the fulvic acid and the content of the fulvic acid in the fulvic acid type potassium sulfate fertilizer.

[0180] A time setting unit is configured to set a plurality of test time points.

[0181] The fourth data processing unit is configured to obtain the residual amount of each heavy metal ion in each soil sub-sample.

[0182] The fifth data processing unit is configured to obtain the residual amount of each heavy metal ion in each sampling unit according to the soil quality of the sampling unit and the residual amount of each heavy metal ion in the soil sub-sample, and sum the residual amount of each heavy metal ion in each sampling unit to obtain the residual amount of each heavy metal ion in the soil of the target area after the heavy metal ion reaches a complex equilibrium with fulvic acid.

[0183] Further, the heavy metal pollution control system further comprises:

[0184] The fourth data processing module is configured to obtain a plurality of potassium ion requirements and a plurality of sulfate ion requirements of the crop at each growth stage.

[0185] The second soil detection device is configured to measure physicochemical characteristic parameters of the first soil sample, wherein the physicochemical characteristic parameters include: a potassium ion initial content, a sulfate ion initial content, a plurality of macroelement contents, a plurality of microelement contents, a pH value, an oxidation-reduction potential, a cation exchange capacity, and an organic matter content.

[0186] The first data acquisition module is configured to acquire growth characteristic parameters and ion absorption characteristic parameters of the crop through a web crawler, wherein the growth characteristic parameters include: a growth duration of each growth stage and a growth rate of each growth stage; and the ion absorption characteristic parameters include: a potassium ion absorption rate, a potassium ion accumulation amount, a sulfate ion absorption rate, and a sulfate ion accumulation amount.

[0187] The parameter setting module is configured to set a target yield and climate parameters, wherein the climate parameters include: a temperature, a precipitation, and an illumination duration.

[0188] The first numerical analysis module is configured to analyze the physicochemical characteristic parameters, the growth characteristic parameters, the ion absorption characteristic parameters, the target yield, and the climate parameters by using a QUEFTS model to obtain the potassium ion requirements and the sulfate ion requirements of the crop at each growth stage.

[0189] The fourth data processing module is configured to extract a maximum value and a minimum value from the plurality of potassium ion requirements to obtain a requirement interval of the potassium ion, and extract a maximum value and a minimum value from the plurality of sulfate ion requirements to obtain a requirement interval of the sulfate ion.

[0190] Further, the soil improvement device comprises:

[0191] The sixth data processing unit is configured to obtain a current content of the potassium ion and a current content of the sulfate ion according to the current content of the potassium sulfate and the proportions of the potassium ion and the sulfate ion in the potassium sulfate, respectively.

[0192] The data analysis control unit is configured to determine whether the current content of potassium ions and the current content of sulfate ions are both within the corresponding required ranges, and if so, end the current heavy metal pollution control, otherwise, control the fertilizer adding device or the resin adding device to work.

[0193] The fertilizer adding device is configured to add fertilizer to the soil.

[0194] The resin adding device is configured to add exchange resin to the soil.

[0195] Further, the heavy metal pollution control system further comprises:

[0196] The third sample collecting device is configured to collect a second soil sample from any sampling unit.

[0197] The third soil detecting device is configured to extract a plurality of complex compounds and a plurality of components from the second soil sample, wherein the components include mineral substances and organic substances.

[0198] The third concentration measuring device is configured to extract the initial concentration of each heavy metal ion and the initial concentration of each ligand from any first soil sample.

[0199] The sixth data processing module is configured to obtain the decomposition time of each complex compound.

[0200] The seventh data processing module is configured to extract the maximum crop waiting time from the decomposition time of the plurality of complex compounds.

[0201] The system restart module is configured to restart the system after the waiting time.

[0202] It should be understood that the terms “system”, “device”, “unit” and / or “module” used in the specification are a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the words can be replaced by other expressions.

[0203] As shown in the specification and claims, unless the context clearly indicates otherwise, the words “one”, “a”, “an” and / or “the” do not refer to the singular, but can also include the plural. Generally, the terms “comprise” and “include” only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements.

[0204] The above detailed description of the specific implementation, the purpose, technical solutions and beneficial effects of the present application are further described in detail, it should be understood that the above description is only a specific embodiment of the present application, and is not used to limit the protection scope of the present application, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

[0205] It should be noted that the structure, proportion, size, etc. shown in the drawings attached to the present specification are only used to cooperate with the content disclosed in the specification, so that those skilled in the art can understand and read, and are not used to limit the implementation conditions of the present application, so they do not have technical significance. Any modification of structure, change of proportion relationship or adjustment of size, without affecting the effect and purpose that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and the like in the present specification are only for the convenience of clear description, and are not used to limit the implementation scope of the present application. The change or adjustment of the relative relationship is also considered as the implementation range of the present application without substantial changes in technical content.

Claims

1. A heavy metal pollution control method based on fulvic acid type potassium sulfate, characterized in that: include: S1: Obtain the types of heavy metal ions in the soil, the content of each heavy metal ion and the complexation ratio of each heavy metal ion to fulvic acid; S2: Based on the content of each heavy metal ion and the corresponding complexation ratio, the amount of fulvic acid required for all heavy metal ions in the soil to be completely complexed is obtained; S3: Obtaining the sowing amount of the fulvic acid type potassium sulfate fertilizer according to the fulvic acid demand and the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer; S4: evenly spread the fulvic acid-type potassium sulfate fertilizer in the soil according to the spreading amount, and record the current content of the fulvic acid-type potassium sulfate fertilizer in the soil; S5: Obtain the residual amount of each heavy metal ion in the soil after reaching complexation equilibrium with fulvic acid; S6: perform S7 for each heavy metal ion; S7: Determine whether the residual amount is greater than the agricultural land soil pollution risk screening value. If so, add a risk label to the heavy metal ion and execute S8. Otherwise, execute S9. S8: Based on the residual amount of each heavy metal ion with a risk label and the corresponding complexation ratio, obtain the fulvic acid requirement corresponding to the complete complexation of all heavy metal ions with a risk label in the soil, and return to S3; S9: Obtain the current content of potassium sulfate in the soil according to the current content of fulvic acid type potassium sulfate fertilizer; S10: Determine whether the current content of potassium sulfate falls within the required range. If so, end the current heavy metal pollution control. Otherwise, adjust the soil nutrients according to the current content of potassium sulfate.

2. A heavy metal pollution control method based on fulvic acid type potassium sulfate according to claim 1, characterized in that, S1 includes: Divide the target area into multiple sampling units; Obtain the coverage area and average soil thickness of each sampling unit; collecting a first soil sample from each sampling unit, and detecting the soil density of each first soil sample; Extracting the types of heavy metal ions and analyzing the content of heavy metal ions in each first soil sample to obtain test data for each first soil sample; the test data includes: the amount of each heavy metal ion in a unit mass of soil; Obtain the amount of each heavy metal ion in each sampling unit according to the test data; The amount of each heavy metal ion in each sampling unit was summed to obtain the content of each heavy metal ion in the soil of the target area.

3. A heavy metal pollution control method based on fulvic acid type potassium sulfate according to claim 2, characterized in that S5 include: A soil subsample of unit mass is extracted from each first soil sample; According to the test data and the corresponding complexation ratio, the amount of fulvic acid added corresponding to the complete complexation of all heavy metal ions in each soil subsample was obtained; Obtaining the addition amount of the fulvic acid type potassium sulfate fertilizer according to the addition amount of fulvic acid and the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer; Set multiple test time points; Obtain the residual amount of each heavy metal ion in each soil subsample; According to the soil mass of the sampling unit and the residual amount of each heavy metal ion in the soil subsample, the residual amount of each heavy metal ion in each sampling unit was obtained; The residual amount of each heavy metal ion in each sampling unit was summed to obtain the residual amount of each heavy metal ion in the soil of the target area after reaching complexation equilibrium with fulvic acid.

4. A heavy metal pollution control method based on fulvic acid type potassium sulfate according to claim 2 or 3, characterized in that, Before S10, the following steps were involved: Obtain multiple potassium ion requirements and multiple sulfate ion requirements of crops at each growth stage; The maximum and minimum values ​​are extracted from multiple potassium ion requirements to obtain the potassium ion requirement range; the maximum and minimum values ​​are extracted from multiple sulfate ion requirements to obtain the sulfate ion requirement range.

5. A heavy metal pollution control method based on fulvic acid type potassium sulfate according to claim 4, characterized in that, S10 includes the following steps: Obtain the current content of potassium ions according to the current content of potassium sulfate and the ratio of potassium ions in potassium sulfate; obtain the current content of sulfate ions according to the current content of potassium sulfate and the ratio of sulfate ions in potassium sulfate; Determine whether the current content of potassium ions and the current content of sulfate ions are both within the corresponding demand range. If so, end the current heavy metal pollution control. Otherwise, add fertilizer or exchange resin according to the potassium ion content and sulfate ion content.

6. A heavy metal pollution control method based on fulvic acid type potassium sulfate according to claim 4, characterized in that, Also includes: S11: collecting a second soil sample from any sampling unit, and extracting a plurality of complexes and a plurality of components from the second soil sample; Components include: minerals and organic matter; S12: extracting the initial concentration of each heavy metal ion and the initial concentration of each ligand from any first soil sample; S13: obtaining the decomposition time of each complex; S14: Extract the maximum crop waiting time from the decomposition time of multiple complexes; S15: Return to S1 after the waiting time.

7. A heavy metal pollution control system based on fulvic acid potassium sulfate, characterized in that: include: A central processing unit, a first soil detection device, a fertilizer spreading device, and a soil improvement device; the central processing unit is connected to the first soil detection device, the fertilizer spreading device, and the soil improvement device respectively; The first soil detection device is used to obtain the types of heavy metal ions in the soil and the content of each heavy metal ion; The CPU includes: A data acquisition module, used to obtain the complexation ratio of each heavy metal ion and fulvic acid; The first data processing module obtains the fulvic acid requirement corresponding to the complete complexation of all heavy metal ions in the soil based on the content of each heavy metal ion and the corresponding complexation ratio; The second data processing module is used to obtain the sowing amount of the fulvic acid type potassium sulfate fertilizer according to the fulvic acid demand and the content of fulvic acid in the fulvic acid type potassium sulfate fertilizer; The fertilizer spreading device is used to spread the fulvic acid type potassium sulfate fertilizer evenly in the soil according to the spreading amount; The CPU also includes: A data recording module is used to record the current content of fulvic acid-type potassium sulfate fertilizer in the soil; The first soil detection device is also used to obtain the residual amount of each heavy metal ion in the soil after reaching complex equilibrium with fulvic acid; The CPU also includes: A first function calling module is used to call the first analysis control module for each heavy metal ion; The first analysis and control module is used to determine whether the residual amount is greater than the agricultural land soil pollution risk screening value. If so, it controls the label adding module and the second analysis and control module to operate; otherwise, it controls the third data processing module to operate; Label adding module, used to add risk labels for heavy metal ions; a second analysis and control module, configured to obtain the fulvic acid requirement corresponding to the complete complexation of all heavy metal ions with risk labels in the soil based on the residual amount and corresponding complexation ratio of each heavy metal ion with risk labels, and sequentially control the operation of the second data processing module, the fertilizer spreading device, the data recording module, the first soil detection device, the first analysis and control module, and the label adding module; A third data processing module is used to obtain the current content of potassium sulfate in the soil according to the current content of fulvic acid-type potassium sulfate fertilizer; The third analysis and control module is used to determine whether the potassium sulfate content falls within the required range. If so, the current heavy metal pollution control is terminated; otherwise, the soil improvement device is controlled to operate; The soil amendment device is used to adjust the nutrients of the soil according to the current content of potassium sulfate.

8. A heavy metal pollution control system based on fulvic acid type potassium sulfate according to claim 7, characterized in that: The first soil detection device includes: 3D scanning equipment, used to obtain a 3D scan image of the target area; An image processing unit is used to divide the target area into multiple sampling units according to the 3D scanning image, and obtain the coverage area and average soil thickness of each sampling unit; a first sample collection device for collecting a first soil sample from each sampling unit; Soil density detection equipment is used to detect the soil density of each first soil sample, and to extract the types of heavy metal ions and analyze the heavy metal ion content of each first soil sample to obtain detection data of each first soil sample; the detection data includes: the amount of each heavy metal ion per unit mass of soil; A first data processing unit is used to obtain the amount of each heavy metal ion in each sampling unit according to the detection data; The second data processing unit is used to sum the amount of each heavy metal ion in each sampling unit to obtain the content of each heavy metal ion in the soil of the target area.

9. A heavy metal pollution control system based on fulvic acid type potassium sulfate according to claim 8, characterized in that: The first soil detection device also includes: a second sample collection device for extracting a soil subsample of unit mass from each first soil sample; a third data processing unit, configured to obtain, based on the detection data and the corresponding complexation ratio, an amount of fulvic acid added corresponding to complete complexation of all heavy metal ions in each soil subsample, and to obtain an amount of fulvic acid-type potassium sulfate fertilizer added based on the amount of fulvic acid added and the content of fulvic acid in the fulvic acid-type potassium sulfate fertilizer; Time setting unit, used to set multiple test time points; a fourth data processing unit, configured to obtain the residual amount of each heavy metal ion in each soil subsample; The fifth data processing unit is used to obtain the residual amount of each heavy metal ion in each sampling unit based on the soil quality of the sampling unit and the residual amount of each heavy metal ion in the soil subsample, and to sum the residual amount of each heavy metal ion in each sampling unit to obtain the residual amount of each heavy metal ion in the soil of the target area after reaching complexation equilibrium with fulvic acid.

10. A heavy metal pollution control system based on fulvic acid potassium sulfate according to claim 8 or 9, characterized in that: Also includes: a fourth data processing module, for obtaining a plurality of potassium ion requirements and a plurality of sulfate ion requirements of the crop at each growth stage; The fifth data processing module is used to extract the maximum and minimum values ​​from multiple potassium ion requirements to obtain the potassium ion requirement range, and to extract the maximum and minimum values ​​from multiple sulfate ion requirements to obtain the sulfate ion requirement range.

11. A heavy metal pollution control system based on fulvic acid potassium sulfate according to claim 10, characterized in that: Soil improvement equipment includes: a sixth data processing unit, configured to obtain a current content of potassium ions and a current content of sulfur ions according to a current content of potassium sulfate and a ratio of potassium ions to sulfate ions in the potassium sulfate; The data analysis control unit is used to determine whether the current content of potassium ions and the current content of sulfate ions fall within the corresponding required range. If so, the current heavy metal pollution control is terminated; otherwise, the fertilizer addition equipment or the resin addition equipment is controlled to work; Fertilizer addition equipment, used to add fertilizer to the soil; Resin adding equipment, used to add exchange resin to the soil.

12. A heavy metal pollution control system based on fulvic acid potassium sulfate according to claim 10, characterized in that: Also includes: a third sample collection device for collecting a second soil sample from any sampling unit; A third soil detection device is used to extract multiple complexes and multiple components from the second soil sample; the components include: minerals and organic matter; a third concentration measuring device, for extracting the initial concentration of each heavy metal ion and the initial concentration of each ligand from any first soil sample; a sixth data processing module, for obtaining the decomposition time of each complex; a seventh data processing module, for extracting a maximum crop waiting time from the decomposition times of the various complexes; The system restart module is used to restart the system after a waiting time.

Images