A method for controlling phosphorus release from bottom sediments in aquatic bodies

Abstract

This invention discloses a method for controlling phosphorus release from bottom sediments in aquatic bodies. The method includes determining the speciation of phosphorus in the bottom sediments, calculating the potential mobile phosphorus content per unit mass of sediment, and then, based on the total dry sediment mass of the water body to be remediated, determining the total potential mobile phosphorus in the sediment. The method also involves determining the total amount of cover material to be added based on the unit saturation adsorption capacity of the cover material for phosphorus in the water and the total potential mobile phosphorus, and then dividing this amount into several equal portions. The cover material is added to the water body to be remediated multiple times, and in-situ passive sampling technology is used to check the formation of a "phosphorus static layer" in the sediment to determine whether to stop adding cover material. The total amount of cover material added before the formation of the "phosphorus static layer" is calculated as the conventional addition amount, and the cover material is added at regular intervals according to this conventional addition amount. Alternatively, the phosphorus concentration in the sediment is analyzed periodically to determine whether to continue adding cover material according to the conventional addition amount.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution control technology, specifically relating to a method for controlling phosphorus release from bottom sediments in water bodies. Background Technology

[0002] Eutrophication is a serious water environment problem, and phosphorus is a key nutrient element that causes eutrophication. The sources of phosphorus in surface water bodies such as lakes, rivers, reservoirs, and ponds are divided into exogenous and endogenous sources. Once the input of exogenous phosphorus is effectively controlled, controlling the release of endogenous phosphorus from the sediment becomes an important measure for the treatment of eutrophication.

[0003] Activated sediment cover is an important method for controlling phosphorus release from water sources. Its working principle is to add activated sediment cover material above the sediment-water interface, and use the adsorption capacity of the activated sediment cover material to control phosphorus release from the sediment. In addition, the cover material can also isolate polluted sediment, thereby controlling phosphorus release from the sediment. Therefore, screening sediment cover materials and determining the application method are the key to controlling phosphorus release from sediment using activated sediment cover technology.

[0004] Currently, most methods for determining the dosage of cover materials, both domestically and internationally, are based on the total phosphorus content in the sediment. This ignores the fact that different forms of phosphorus in the sediment have varying release potentials, leading to unreasonable dosages. Furthermore, current cover materials are often added only once, but these materials are prone to aging, reducing their phosphorus adsorption capacity and thus diminishing their effectiveness in controlling phosphorus release from the sediment. In addition, metal-based materials are the most common type of cover material used to control phosphorus release from sediment, and impregnation is a common method for preparing them. However, existing methods for preparing metal-based cover materials are prone to causing secondary pollution. Therefore, there is an urgent need for a method to control the release of endogenous phosphorus from sediment in aquatic environments that addresses the aforementioned shortcomings. Summary of the Invention

[0005] This invention provides a method for controlling phosphorus release from bottom sediments in water bodies, which solves the technical problems of existing active cover methods, such as the reduction in the phosphorus adsorption capacity of the cover material and the unreasonable amount of cover material to be added, which are mostly done in a single application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for controlling phosphorus release from bottom sediments in aquatic bodies includes the following steps:

[0008] Step 1: Determine the occurrence form of phosphorus in the sediment of the water body, calculate the potential mobile phosphorus content per unit mass of sediment, and then combine it with the total dry sediment mass of the water body to be remediated to determine the total potential mobile phosphorus content in the sediment of the water body to be remediated.

[0009] Step 2: Based on the unit saturated adsorption capacity of the covering material for phosphorus in the water and the total content of potential mobile phosphorus, determine the total amount of covering material to be added, and then divide the total amount of covering material into several equal parts.

[0010] Step 3: Add an equal portion of covering material to the water body that needs to be repaired, and use in-situ passive sampling technology to check the formation of a "phosphorus static layer" in the sediment. If a layer has formed, stop adding the covering material; if not, continue adding an equal portion of covering material and use in-situ passive sampling technology to check the formation of a "phosphorus static layer" in the sediment. Repeat this process until a "phosphorus static layer" is formed. Then calculate the total amount of covering material added before the formation of the "phosphorus static layer". This total amount of covering material is the regular addition amount.

[0011] Step 4: Apply the covering material at regular intervals using the standard dosage.

[0012] Alternatively, in-situ passive sampling technology can be used periodically to analyze the phosphorus concentration in the sediment of the water body. If the phosphorus concentration is found to exceed the preset value, the covering material can be added according to the usual dosage.

[0013] Furthermore, in step two, the total potential mobile phosphorus content M in the bottom sediment of the water body is calculated and determined according to the following formula;

[0014]

[0015]

[0016] In the formula, m is the total dry sediment mass in the water body (kg); q is the potential mobile phosphorus content per unit mass of dry sediment (mg / kg); and A is the area of ​​the sediment-water interface (m²). 2 h is the thickness of the bottom sediment in the water body (m), and ρ is the density of the bottom sediment in the water body (kg / m³). 3 W represents the water content of the bottom sediment of the water body.

[0017] Furthermore, the total amount of covering material Q to be added is determined using the following formula.

[0018]

[0019] In the formula, M is the total potential mobile phosphorus content in the sediment of the water body (mg); Q m The unit saturation adsorption capacity (mg / kg) of the covering material for phosphate in water is given.

[0020] Furthermore, the total amount of covering material added is divided into 20-200 equal portions;

[0021] Alternatively, the following formula can be used to calculate the number of equal parts, n;

[0022]

[0023] In the formula, F is the phosphorus release flux from the sediment (mg / (m³)). 2 ·d), where t is the duration d of phosphorus release from the sediment controlled by the covering material, which needs to be determined based on the actual situation.

[0024] Furthermore, the method for calculating the phosphorus release flux from the sediment is set as either the sediment core culture method or the sediment available phosphorus and pore water dissolved concentration profile estimation method.

[0025] Furthermore, the method for determining the unit saturated adsorption capacity of the covering material for phosphorus in water includes the following steps:

[0026] Step 1: Prepare phosphorus solutions with different initial concentrations and adjust the pH value of the phosphorus solutions to a certain value, which is determined according to the actual pH value of the water body;

[0027] Step II: The added covering material is subjected to a shaking reaction with phosphorus solutions of different concentrations. After the reaction is completed, the phosphorus concentration in the solution is measured.

[0028] Step III: Calculate the unit adsorption capacity of the covering material for phosphorus in water using the following formula. ;

[0029]

[0030] In the formula, V represents the volume of the phosphorus solution (L); a represents the amount of covering material added in step II (g); c0 and c e The values ​​represent the phosphorus concentration (mg / L) in the phosphorus solution before the adsorption reaction and at the reaction equilibrium time, respectively.

[0031] The unit saturated adsorption capacity Q of the covering material for phosphorus in water m The unit adsorption capacity corresponding to different concentrations of phosphorus solutions The maximum value can be determined by fitting the experimental data to the following isothermal adsorption model;

[0032]

[0033] In the formula, c e This indicates the equilibrium concentration of phosphorus in the solution (mg / L); K L Q is the isothermal adsorption model constant (L / mg). m This indicates the saturated adsorption capacity of the covering material for phosphorus in water, expressed in mg / g; Q e This indicates the amount of phosphorus adsorbed by the covering material in water at equilibrium time, expressed in mg / g.

[0034] Furthermore, the covering material is configured to be a metal-based covering material prepared using a multi-stage impregnation method.

[0035] Furthermore, a graded continuous chemical extraction method was used to determine the occurrence form of phosphorus in the sediment of the water body, and easily desorbed phosphorus and redox-sensitive phosphorus in the sediment were set as potential mobile phosphorus.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] (1) By using a multi-stage impregnation method to prepare metal-based covering materials, all metal ions in the liquid phase can be loaded onto the surface of inexpensive natural mineral materials. This not only yields efficient and economical active covering materials for bottom sediments, but also avoids the waste of metal salts, saving resources and being safe and environmentally friendly.

[0038] (2) By using the calculation method for the total amount and single amount of active cover material added to the sediment proposed in this invention, the amount of active cover material required to control phosphorus release from the sediment can be accurately determined. This allows for the precise and sequential addition of the cover material below the sediment-water interface to form a cover layer. Compared with traditional methods, the sediment phosphorus release control method of this invention not only controls sediment phosphorus release more effectively but also saves on the amount of active cover material added, thereby reducing sediment remediation costs. Therefore, this method has significant application and promotion value. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the overall process of the present invention;

[0040] Figure 2 The image shows a physical diagram of the covering material of the present invention, wherein (a) represents iron-modified dolomite; and (b) represents iron-modified bentonite.

[0041] Figure 3 This is the X-ray diffraction pattern of the iron-modified dolomite used as the covering material in this invention;

[0042] Figure 4 This is a schematic diagram of the chemical composition of the original dolomite and iron-modified dolomite used as the covering materials of this invention.

[0043] Figure 5 The adsorption kinetics curve of phosphate in water by iron-modified dolomite, the coating material of this invention;

[0044] Figure 6 This is a schematic diagram illustrating the effect of the initial phosphorus concentration on the adsorption of phosphates in water by the iron-modified dolomite covering material according to the present invention.

[0045] Figure 7This is a schematic diagram of the removal effect of iron-modified dolomite, the covering material of the present invention, on the DGT available phosphorus in the vertical cross section of the overlying water-sediment. The zero mark on the vertical axis represents the sediment-overlying water interface, with the overlying water above the interface and the sediment below the interface. The higher the concentration of DGT available phosphorus, the more severe the phosphorus pollution.

[0046] Wherein, (a) represents the change curve of DGT available phosphorus concentration in different states, and (b) represents the change of DGT available phosphorus removal rate by the covering material using the existing one-time covering method and the multiple covering method of the present invention. Detailed Implementation

[0047] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings and preferred embodiments.

[0048] To address the shortcomings of existing methods for controlling phosphorus release from bottom sediments in water bodies, such as... Figure 1 As shown, this invention proposes a method for controlling phosphorus release from aquatic sediments. Specifically, it involves first developing an active sediment cover material that reduces secondary pollution, is simple to prepare, and has good phosphate adsorption properties. Then, based on the potential mobile phosphorus content in the sediment and the specific conditions of the water body, the total amount of active cover material to be added is determined. Next, the amount of active cover material to be added in a single application is determined. Finally, a method for gradually adding the cover material to the water body is provided. Compared with existing methods for controlling phosphorus release from sediments, the sediment cover layer formed by gradual addition can effectively control phosphorus release from aquatic sediments. The method proposed in this invention is more environmentally friendly, has a better effect on controlling phosphorus release from sediments, and can more accurately determine the amount of active cover material to be added, thereby reducing the cost of controlling phosphorus release from aquatic sediments and environmental remediation.

[0049] Specifically as follows:

[0050] Step 1: Preparation of Covering Material

[0051] Metal-based coating materials were prepared using a multi-stage impregnation method. The preparation steps were as follows:

[0052] 1) Mix the metal salt solution with the natural mineral material at a mass ratio of 0.5:1 or higher, and react for a period of time, such as 30 to 1440 minutes. Collect the solid material, wash it, and obtain the first metal-based coating material. The natural mineral material can be bentonite, montmorillonite, attapulgite, illite, kaolinite, palygorskite, calcite, dolomite, etc.; the metal salt can be ferric chloride, ferric sulfate, ferric nitrate, polyferric sulfate, aluminum chloride, aluminum sulfate, polyaluminum chloride, lanthanum chloride, lanthanum nitrate, zirconium oxychloride octahydrate, etc.

[0053] The ratio of the mass of natural mineral material to the volume of water is 1 g: (5-100) mL, that is, 1 g of natural mineral material is mixed with 5-100 mL of water.

[0054] 2) The reacted solution is then mixed with natural mineral materials, and the same steps 1) are followed to obtain a second metal-based coating material;

[0055] 3) Repeat step 2) until all the metal ions in the solution are loaded by the natural mineral material.

[0056] Step 2: Determine the occurrence form of phosphorus in the sediment of the water body, calculate the potential mobile phosphorus content per unit mass of the sediment, and then, in combination with the total dry sediment mass of the water body to be remediated, determine the total potential mobile phosphorus content in the sediment of the water body to be remediated.

[0057] S2.1 Analysis of phosphorus occurrence in sediment using a graded continuous chemical extraction method

[0058] This method classifies phosphorus in sediment into five forms: readily desorbable phosphorus, redox-sensitive phosphorus, metal-bound phosphorus, calcium-bound phosphorus, and residual phosphorus. These five forms of phosphorus are treated with 1 mol / L ammonium chloride solution, a mixed solution of 0.11 mol / L sodium bicarbonate and 0.11 mol / L sodium dithionite, 1 mol / L sodium hydroxide solution (room temperature), 1 mol / L hydrochloric acid solution, and 1 mol / L sodium hydroxide solution (85 degrees Celsius), respectively.

[0059] Among them, easily desorbed phosphorus and redox-sensitive phosphorus are potential mobile phosphorus in the sediment. The content of this potential mobile phosphorus is the sum of the contents of easily desorbed phosphorus and redox-sensitive phosphorus in the sediment.

[0060] S2.2 Determine the sediment-overlying water interface area and sediment thickness of the surface water bodies such as lakes, reservoirs, and ponds that need to be restored, and calculate the total dry sediment mass m according to the following formula;

[0061]

[0062] In the formula, A is the area (m²) of the sediment-water interface. 2 h is the thickness of the bottom sediment in the water body (m), and ρ is the density of the bottom sediment in the water body (kg / m³). 3 W represents the water content of the bottom sediment of the water body.

[0063] S2.3. Determine the total potential mobile phosphorus content M in the sediment of the water body that needs remediation according to the following formula.

[0064]

[0065] In the formula, q is the potential mobile phosphorus content per unit mass of dry sediment (mg / kg), which is equal to the sum of the easily desorbed phosphorus and redox-sensitive phosphorus content in the sediment, and can be obtained by direct measurement.

[0066] Step 3: Based on the unit saturated adsorption capacity of the covering material for phosphorus in the water and the total potential mobile phosphorus content M, determine the total amount of covering material to be added, and then divide the total amount of covering material into several equal parts.

[0067] S3.1 Calculate the unit saturated adsorption capacity of the covering material for phosphorus in water, specifically including the following steps:

[0068] Step 1: Prepare phosphorus solutions with different initial concentrations and adjust the pH value of these phosphorus solutions to a certain value, which is determined according to the actual pH value of the water body;

[0069] Step II: The covering material is reacted with phosphorus solutions of different phosphorus concentrations by shaking. After the reaction is completed, the phosphorus concentration in the solution is measured.

[0070] Step III: Calculate the unit adsorption capacity of the covering material for phosphorus in water using the following formula. ;

[0071]

[0072] In the formula, V represents the volume of the phosphorus solution (L); a represents the amount of covering material added in step II (g); c0 and c e The values ​​represent the phosphorus concentration (mg / L) in the phosphorus solution before the adsorption reaction and at the reaction equilibrium time, respectively.

[0073] The unit saturated adsorption capacity Q of the covering material for phosphorus in water m The adsorption capacity per unit area in the adsorption equilibrium data can be obtained through the above steps. The maximum value can be determined, or it can be determined by fitting the experimental data to the following isothermal adsorption model;

[0074]

[0075] In the formula, c e This indicates the equilibrium concentration of phosphorus in the solution (mg / L); K L Q is the isothermal adsorption model constant (L / mg); m Q represents the saturated adsorption capacity (mg / g) of the covering material for phosphorus in water, i.e., the saturated adsorption amount of phosphate in water per unit mass of covering material; e This indicates the amount of phosphorus adsorbed by the covering material in water at equilibrium (mg / g).

[0076] S3.2. Use the following formula to determine the total amount Q of the covering material to be added.

[0077]

[0078] In the formula, M is the total potential mobile phosphorus content in the sediment of the water body (mg); Q m The unit saturation adsorption capacity (mg / kg) of the covering material for phosphate in water is given.

[0079] S3.3 Divide the covering material to be added into several equal parts and determine the amount of covering material to be added to each equal part. The following two methods can be used to determine the number of equal parts.

[0080] The first method involves dividing the total amount of covering material into 20-200 equal portions.

[0081] The second method involves using the following formula to calculate the number of equal parts, n.

[0082]

[0083] In the formula, F is the phosphorus release flux from the sediment (mg / (m³)). 2 ·d), where t is the duration d of phosphorus release from the sediment controlled by the covering material, which needs to be determined according to the actual situation, and is generally taken as 20 to 200 days.

[0084] Among them, the methods for calculating the phosphorus release flux F from the sediment include in-situ observation, sediment core culture, sediment effective phosphorus and pore water dissolved concentration profile estimation, mass balance, isotope mass balance and empirical formula method. Generally, sediment core culture and sediment effective phosphorus and pore water dissolved concentration profile estimation are adopted.

[0085] 1. The steps for determining phosphorus release flux from sediment using the sediment core culture method are as follows:

[0086] 1) Collect sediment core samples and then seal the sediment core samples with rubber stoppers;

[0087] 2) Analyze the phosphorus concentration in the overlying water;

[0088] 3) Calculate the phosphorus release flux in the sediment according to the following formula.

[0089]

[0090] In the formula, F is the phosphorus release flux from the sediment [mg / (m³)]. 2 / d)];V is the volume of water covering the sediment column (L); V j-1 The volume (L) of the water sample taken in the (j-1)th time; C0, C n and C j-1 These represent the phosphorus concentrations (mg / L) in the water samples taken at the 1st, nth, and (j-1th)th times, respectively; C aIndicates the phosphorus concentration (mg / L) in the added water; A represents the surface area (m²) of the sediment-water interface. 2 ); t is the sediment culture period (d).

[0091] 2. The steps for determining the phosphorus release flux from sediment using the sediment available phosphorus and pore water dissolved phosphorus concentration profile estimation method are as follows:

[0092] 1) Determine the concentration of dissolved or available phosphorus above and below the sediment-water interface;

[0093] 2) For dissolved phosphorus, the phosphorus release flux in the sediment is calculated using the following formula;

[0094]

[0095] In the formula, D indicates the porosity of the sediment; s The effective diffusion coefficient of phosphate in sediment (cm) 2 / s); This represents the concentration gradient at the sediment-overlying water interface [mg / (L·cm)].

[0096] 3) For available phosphorus, the phosphorus release flux in the sediment is calculated according to the following formula.

[0097]

[0098] In the formula, This represents the concentration gradient of available phosphorus in the sediment [mg / (L·cm)]; D represents the concentration gradient of available phosphorus in the overlying water [mg / (L·cm)]; s Indicates the effective diffusion coefficient of phosphate in sediment (cm). 2 / s); D w The effective diffusion coefficient of phosphate in water (cm) 2 / s).

[0099] Step 4: Add an equal amount of covering material to the water body that needs to be repaired, and use in-situ passive sampling technology to check the formation of a "phosphorus static layer" in the sediment. If it forms, stop adding the covering material; if it does not form, continue adding an equal amount of covering material and use in-situ passive sampling technology to check the formation of a "phosphorus static layer" in the sediment. Repeat this process until a "phosphorus static layer" forms. Then calculate the total amount of covering material added before the formation of the "phosphorus static layer", which is the regular addition amount.

[0100] S4.1 Determination of "Phosphorus Static Layer"

[0101] In-situ passive sampling technology can be used to analyze the concentration of available or dissolved phosphorus in the surface sediment. The discrimination method is: the concentration of available or dissolved phosphorus in the sediment of 0 to (10-40) mm is 50% or more lower than the initial concentration.

[0102] The in-situ passive sampling technology refers to thin-film gradient diffusion (DGT) technology, high-resolution dialysis sampling technology, or in-situ sediment pore water collectors.

[0103] S4.2. The total amount of covering material added before the formation of the "static phosphorus layer" in the sediment is the regular addition amount. The quality of each subsequent addition of covering material is then determined.

[0104] Step 5: Apply the covering material at regular intervals using the standard dosage.

[0105] Alternatively, in-situ passive sampling technology can be used periodically to analyze the phosphorus concentration in the sediment of the water body. If the phosphorus concentration is found to exceed the preset value, the covering material can be added according to the usual dosage.

[0106] To verify the feasibility of the method for controlling phosphorus release from sediment in this invention, we take the control of phosphorus release from sediment in surface water bodies using iron-based covering materials as an example to illustrate the implementation process and effects of this invention.

[0107] After testing, the potential mobile phosphorus content in the sediment of the implemented case was 141 mg / kg. Iron-modified dolomite was used to control the release of phosphorus from the sediment.

[0108] I. Preparation steps of iron-modified dolomite: 1) Weigh a certain mass of dolomite and place it in a container, then add a certain volume of water so that the mass ratio of dolomite to water is 1g:2.5mL; 2) Weigh a certain mass of ferric nitrate nonahydrate and place it in a container, then add a certain volume of water to prepare an iron solution so that the mass ratio of ferric nitrate nonahydrate to water is 1g:5mL; 3) Add the iron solution dropwise to the dolomite suspension so that the mass ratio of ferric nitrate nonahydrate to dolomite is 0.5, and continue the reaction for 24 hours; 4) Wash three times, dry at 105 degrees Celsius, crush, and pass through a 200-mesh sieve. See Appendix for its specific structure. Figure 2-4 .

[0109] Adsorption experiments determined that the unit saturated adsorption capacity of the prepared iron-modified dolomite for phosphate in water was 2.64 mg / g. Figure 5-6 As shown.

[0110] II. Based on a surface water area of ​​1 square meter and a surface sediment thickness of 4 cm, the required phosphorus concentration in the sediment per unit water surface area is calculated to be 2543 mg P / m³. 2 Further calculations determined 1m 2The water surface area requires the addition of 963g of iron-modified dolomite.

[0111] The DGT concentration in the surface sediment was determined using the thin-film diffusion gradient (DGT) technique. Based on the sediment available phosphorus concentration profile estimation method, the sediment phosphorus release flux F was determined to be 11.9 mg / (m³). 2 •d).

[0112] 3. Divide the covering material into several equal parts.

[0113] The dosage of each equal portion of covering material is 11.9 × 21 / 2.64 = 95 g / m³. 2 The number of mulch material portions is approximately 963 / 95 ≈ 10. Based on the determined number of equal portions, the dosage of each mulch material portion is adjusted to 96.3 g / m³. 2 .

[0114] Testing revealed that adding one part of iron-modified dolomite, which is applied as a cover layer above the sediment-water interface, resulted in an addition rate of 96.3 g / m³. 2 Iron-modified dolomite can form a "static phosphorus layer" in the surface sediment. Therefore, the single dosage of iron-modified dolomite was determined to be 96.3 g / m³. 2 .

[0115] The following experiment was conducted to examine the effect of multiple additions of iron-modified dolomite on controlling phosphorus release from sediment. The experimental steps are as follows:

[0116] 1) Take 9 cylindrical columns with a diameter of 11.5 cm and a height of 30 cm, and add bottom mud into the columns until the bottom mud is 10 cm high;

[0117] 2) The columns were divided into three groups: a control group, a single large-dose iron-modified dolomite addition group, and a multiple small-dose iron-modified dolomite addition group, with three columns in each group. For the control group (T0), 5g of dry suspended particulate matter (SPM) was added every 2 days. For the single iron-modified dolomite addition group (T1), 5g of dry SPM was added every 2 days, and before the sediment culture began, 10g of iron-modified dolomite was placed on top of the sediment in one go (equivalent to 963g / m³). 2 For the iron-modified dolomite multi-dosing group (T2), 5g of dry SPM was added every 2 days, and 10g of cover material was divided into 10 batches, with an initial addition of 1g of cover material (equivalent to 96.3g / m³). 2 After that, add once every 4 days, and complete the addition in 36 days;

[0118] 3) The dissolved active phosphorus (SRP) and dissolved total phosphorus (DTP) in the overlying water were determined.

[0119] The experimental results showed that on day 28, the SRP concentrations in the overlying water of groups T0, T1, and T2 were 0.517, 0.242, and 0.022 mg / L, respectively, and the DTP concentrations were 0.590, 0.309, and 0.068 mg / L, respectively. The removal rates of SRP from the overlying water by T1 and T2 were 53.1% and 95.7%, respectively, and the removal rates of DTP were 40.2% and 86.7%, respectively. On day 48, the SRP concentrations in the overlying water of groups T0, T1, and T2 were 0.891, 0.521, and 0.034 mg / L, respectively, and the DTP concentrations were 0.921, 0.528, and 0.061 mg / L, respectively. The removal rates of SRP from the overlying water by T1 and T2 were 41.5% and 96.1%, respectively, and the removal rates of DTP were 40.7% and 93.2%, respectively. This indicates that the multiple additions of iron-modified dolomite can effectively control the release of phosphorus from the sediment into the overlying water. It also shows that the multiple additions of iron-modified dolomite are significantly better than the single addition of iron-modified dolomite in controlling phosphorus release from the sediment, which further proves the effectiveness of the method proposed in this invention.

[0120] The concentration of available phosphorus in the DGT-rich vertical profile of the overlying water-sediment was further determined using a DGT apparatus, such as... Figure 7 As shown, the results indicate that the concentration of available DGT phosphorus in the overlying water under multiple additions of iron-modified dolomite was significantly lower than that in the control group, and the concentration of available DGT phosphorus in the 0-18mm sediment was also significantly lower under the former method. This further demonstrates that multiple additions of iron-modified dolomite can effectively control the release of phosphorus from the sediment into the overlying water. Furthermore, the removal efficiency of available DGT phosphorus in both the overlying water and surface sediment by multiple additions of iron-modified dolomite was significantly higher than that by a single addition. This further confirms that the effect of multiple additions of iron-modified dolomite in controlling phosphorus release from the sediment is significantly better than that of a single addition, further demonstrating the effectiveness of the method proposed in this invention.

[0121] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples. Various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. Therefore, the scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for controlling phosphorus release from bottom sediments in aquatic bodies, characterized in that... Includes the following steps: Step 1: Determine the occurrence form of phosphorus in the sediment of the water body, calculate the potential mobile phosphorus content per unit mass of sediment, and then combine it with the total dry sediment mass of the water body to be remediated to determine the total potential mobile phosphorus content in the sediment of the water body to be remediated. Step 2: Based on the unit saturated adsorption capacity of the covering material for phosphorus in the water and the total content of potential mobile phosphorus, determine the total amount of covering material to be added, and then divide the total amount of covering material into several equal parts. Calculate the number of equal parts, n, using the following formula; In the formula, F is the phosphorus release flux from the sediment (mg / (m³)). 2 ·d), where t is the duration (d) of phosphorus release from sediment controlled by the cover material, ranging from 20 to 200 days, M is the total potential mobile phosphorus content (mg), and A is the area (m²) of the sediment-water interface. 2 ; Step 3: Add an equal portion of covering material to the water body that needs to be repaired, and use in-situ passive sampling technology to check the formation of a "phosphorus static layer" in the sediment. If a layer has formed, stop adding the covering material; if not, continue adding an equal portion of covering material and use in-situ passive sampling technology to check the formation of a "phosphorus static layer" in the sediment. Repeat this process until a "phosphorus static layer" is formed. Then calculate the total amount of covering material added before the formation of the "phosphorus static layer". This total amount of covering material is the regular addition amount. Step 4: Apply the covering material at regular intervals using the standard dosage. Alternatively, in-situ passive sampling technology can be used periodically to analyze the phosphorus concentration in the sediment of the water body. If the phosphorus concentration is found to exceed the preset value, the covering material can be added according to the usual dosage.

2. The method for controlling phosphorus release from bottom sediments in water bodies according to claim 1, characterized in that: In step one, the total potential mobile phosphorus content M in the bottom sediment of the water body is calculated and determined according to the following formula; In the formula, m is the total dry sediment mass in the water body (kg); q is the potential mobile phosphorus content per unit mass of dry sediment (mg / kg); and A is the area of ​​the sediment-water interface (m²). 2 h is the thickness of the bottom sediment in the water body (m), and ρ is the density of the bottom sediment in the water body (kg / m³). 3 W represents the water content of the bottom sediment of the water body.

3. The method for controlling phosphorus release from bottom sediments in water bodies according to claim 2, characterized in that: The total amount of covering material Q to be added is determined using the following formula. In the formula, M is the total potential mobile phosphorus content in the sediment of the water body (mg); Q m The unit saturation adsorption capacity (mg / kg) of the covering material for phosphate in water is given.

4. The method for controlling phosphorus release from bottom sediments in water bodies according to claim 1, characterized in that: The method for calculating the phosphorus release flux from the sediment is set as either the sediment core culture method or the sediment available phosphorus and pore water dissolved concentration profile estimation method.

5. The method for controlling phosphorus release from bottom sediments in water bodies according to claim 1, characterized in that... The method for determining the unit saturated adsorption capacity of the covering material for phosphorus in water includes the following steps: Step 1: Prepare phosphorus solutions with different initial concentrations and adjust the pH value of the phosphorus solutions to a certain value, which is determined according to the actual pH value of the water body; Step II: The added covering material is subjected to a shaking reaction with phosphorus solutions of different concentrations. After the reaction is completed, the phosphorus concentration in the solution is measured. Step III: Calculate the unit adsorption capacity of the covering material for phosphorus in water using the following formula. ; In the formula, V represents the volume of the phosphorus solution (L); a represents the amount of covering material added in step II (g); c0 and c e The values ​​represent the phosphorus concentration (mg / L) in the phosphorus solution before the adsorption reaction and at the reaction equilibrium time, respectively. The unit saturated adsorption capacity Q of the covering material for phosphorus in water m The unit adsorption capacity corresponding to different concentrations of phosphorus solutions The maximum value can be determined by fitting the experimental data to the following isothermal adsorption model; In the formula, c e This indicates the equilibrium concentration of phosphorus in the solution (mg / L); K L Q is the isothermal adsorption model constant (L / mg). m This indicates the saturated adsorption capacity of the covering material for phosphorus in water, expressed in mg / g; Q e This indicates the amount of phosphorus adsorbed by the covering material in water at equilibrium time, expressed in mg / g.

6. The method for controlling phosphorus release from bottom sediments in water bodies according to claim 1, characterized in that: The covering material is prepared using a multi-stage impregnation method to create a metal-based covering material.

7. The method for controlling phosphorus release from bottom sediments in water bodies according to claim 1, characterized in that: The occurrence forms of phosphorus in water sediment were determined by a graded continuous chemical extraction method, and easily desorbed phosphorus and redox-sensitive phosphorus in the sediment were identified as potential mobile phosphorus.

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