A method for simulating chemical equilibria of soil salt ions

Abstract

The embodiment of the application provides a chemical equilibrium simulation method for soil salt ions, comprising: acquiring multiple ion data of parameters associated with a chemical equilibrium simulation process of salt ions and constructing a chemical reaction parameter database; and calculating ion activity and constructing a chemical solving model, wherein the chemical solving model comprises a precipitation-dissolution reaction simulation model and a complexation reaction-cation exchange simulation model, one chemical solving is completed by sequentially solving the precipitation-dissolution reaction simulation model and the complexation reaction-cation exchange simulation model; setting initial conditions and termination conditions of iterative operation of the chemical solving model, inputting parameter data into solving, taking a concentration difference of multiple ions after adjacent two chemical solvings as an external loop control standard epsilon, judging whether to enter next chemical solving iteration or outputting a simulation result to obtain a precipitated chemical component content, a complexed chemical component content and an exchanged chemical component content of the salt ions in the soil.

Description

Technical Field

[0001] This application relates to the field of soil and groundwater environmental technology, and in particular to a method for simulating the chemical equilibrium of soil salt ions. Background Technology

[0002] Soil salinization is a global resource and ecological problem, and one of the main causes of arable land shortage and ecological degradation. Soil contains various salt ions, which undergo highly complex chemical reactions, significantly influencing the chemical composition of the soil system. However, current methods for measuring the chemical composition of soil systems can only determine the total amount of different salt ions, unable to identify their forms and chemical components. Furthermore, different forms of chemical components exhibit different migration characteristics, leading to varying impacts on soil properties and plant and animal growth. Different remediation measures are needed for saline soils with different salt ion compositions to effectively remove excess salt. Therefore, providing a chemical balance simulation method for soil salt ions to further analyze soil chemical component types and determine the chemical forms of soil salt ions and the content of different chemical components is a technical problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0003] This application aims to at least partially address one of the technical problems in the related art.

[0004] Therefore, the purpose of this application is to propose a chemical equilibrium simulation method for soil salt ions, which can simulate the chemical reactions and existing forms of salt ions in soil, as well as the content of different types of chemical components.

[0005] To achieve the above objectives, this application proposes a method for simulating the chemical equilibrium of soil salt ions, comprising:

[0006] Acquire multiple ion data related to parameters in the chemical equilibrium simulation process of salt ions and construct a chemical reaction parameter database;

[0007] The activity of each ion is calculated and a chemical solution model is constructed. The chemical solution model includes a precipitation-dissolution reaction simulation model and a complexation reaction-cation exchange simulation model. A chemical solution is completed by solving the precipitation-dissolution reaction simulation model and the complexation reaction-cation exchange simulation model in sequence.

[0008] The initial and termination conditions of the chemical solution model are set, the parameter data is input for solution, and the concentration difference of multiple ions after two adjacent chemical solutions is used as the external loop control standard ε to determine whether to enter the next chemical solution iteration or output the simulation results to obtain the content of precipitated chemical components, complexed chemical components and exchanged chemical components of salt ions in the soil.

[0009] In some embodiments, the various ions associated with the chemical equilibrium simulation process of salt ions include calcium ions, magnesium ions, potassium ions, sodium ions, carbonate ions, sulfate ions, bicarbonate ions, and chloride ions.

[0010] In some embodiments, the database contains the charge number, hydrated ionic radius, Debye-Hückel constant, precipitation-dissolution solubility product constant, complexation equilibrium constant, and Gapon selectivity coefficient for cation exchange reactions of various ions.

[0011] In some embodiments, the activities of each ion are calculated as follows:

[0012] a i =γ i m i

[0013] In the formula, a i m represents the activity of the component, dimensionless; i The molar concentration of the component is mol / L; γ i The activity coefficient is L / mol; i represents a certain component;

[0014] The activity coefficient of the charged component is calculated as follows:

[0015]

[0016] I represents the ionic strength in mol / L; m i The molar concentration of the charged component is mol / L; z i Let r be the charge number of charged component i; i represents a charged component, including free ions and charged complexes; A' and B' are Debye-Hückel constants, and r is the charge number of the charged component i. i The hydrated ionic radius of component i is 10. -10 m;

[0017] The activity coefficient of an electrically neutral complex is lgγ = a'I

[0018] Where a' is an empirical coefficient; I is the ionic strength in mol / L.

[0019] In some embodiments, the precipitation-dissolution reaction simulation model includes precipitation-dissolution reaction sub-models for five minerals, including a CaCO3 precipitation-dissolution reaction sub-model, a MgCO3 precipitation-dissolution reaction sub-model, a CaSO4 precipitation-dissolution reaction sub-model, a MgSO4 precipitation-dissolution reaction sub-model, and a NaCl precipitation-dissolution reaction sub-model; the precipitation-dissolution reaction simulation method includes:

[0020] The precipitation-dissolution reaction sub-models of the five minerals are solved sequentially according to their solubility from smallest to largest to complete one precipitation-dissolution cycle; the initial concentration values ​​of each free ion used in one precipitation-dissolution cycle are the same;

[0021] The concentration difference of the same free ion after different minerals is solved is used as the internal cycle standard ε1 of the precipitation-dissolution cycle; if the concentration difference of the same free ion after different minerals is solved does not reach ε1, the next precipitation-dissolution cycle is entered; at the same time, the free ion concentration calculated by the mineral with low solubility is used as the initial concentration value of the free ion in the next precipitation-dissolution cycle, until the concentration difference of the same free ion after different minerals is solved reaches ε1.

[0022] In some embodiments, the solution process for the CaCO3 precipitation-dissolution reaction sub-model, the MgCO3 precipitation-dissolution reaction sub-model, the CaSO4 precipitation-dissolution reaction sub-model, the MgSO4 precipitation-dissolution reaction sub-model, and the NaCl precipitation-dissolution reaction sub-model is the same, including the following steps:

[0023] (1) Calculate the activity product Q of the minerals in the solution. sp When Q sp ≠ Solubility product constant K of mineral precipitation-dissolution reaction sp Calculate the amount of mineral precipitation or dissolution ΔC; determine Q. sp Is it greater than K? sp If "yes", the solution is supersaturated with the mineral and precipitation occurs; if "no", the solution is undersaturated with the mineral and dissolves. Dissolution includes one of the following scenarios:

[0024] If the mineral is not present in the soil in the current iteration step, then the mineral will not dissolve and its free ion concentration will remain unchanged.

[0025] If the concentration of a mineral in the solution at the current iteration step, C1 mol / L, is greater than ΔC, then the mineral will partially dissolve until the solubility product constant is reached.

[0026] If the concentration of a mineral in the solution at the current iteration step, C1 mol / L, is less than ΔC, then all of that mineral will dissolve.

[0027] In some embodiments, the precipitation-dissolution reaction of CaCO3 in the CaCO3 precipitation-dissolution reaction sub-model is as follows:

[0028] The solubility product constant of the precipitation-dissolution reaction of CaCO3

[0029] The precipitation-dissolution reaction of MgCO3 in the MgCO3 precipitation-dissolution reaction sub-model is shown in the following equation:

[0030] Solubility product constant of MgCO3 precipitation-dissolution reaction

[0031] The precipitation-dissolution reaction of CaSO4 in the CaSO4 precipitation-dissolution reaction sub-model is shown in the following equation:

[0032] The solubility product constant of the precipitation-dissolution reaction of CaSO4

[0033] The precipitation-dissolution reaction of MgSO4 in the MgSO4 precipitation-dissolution reaction sub-model is shown in the following equation:

[0034] Solubility product constant of MgSO4 precipitation-dissolution reaction

[0035] The NaCl precipitation-dissolution reaction in the NaCl precipitation-dissolution reaction sub-model is shown in the following equation:

[0036] Solubility product constant of NaCl precipitation-dissolution reaction In each formula, () represents activity.

[0037] In some embodiments, the internal iterative convergence index ε1 of the precipitation-dissolution cycle is expressed by the following equation:

[0038]

[0039] in

[0040]

[0041]

[0042]

[0043] In the formula, These are the Ca values ​​obtained from precipitation-dissolution calculations of different minerals. 2 + Mg 2+ CO3 2- SO4 2- The concentration difference (mol / L).

[0044] In some embodiments, the complexation reaction-cation exchange simulation model solves for both the complexation reaction and the cation exchange reaction simultaneously, as follows:

[0045] By simultaneously establishing the mass action equations for ten complexation reactions, the Gapon equations for three of the six cation exchange reactions, the CEC conservation equation, and the mass conservation equations for eight salt ions, and simplifying them, a nonlinear equation system containing eleven unknowns is obtained. Solving for the unknowns completes one complexation reaction-cation exchange cycle. The unknowns are the concentrations of free ions other than chloride ions and the four exchangeable cations Ca2+. 1 / 2 X, Mg 1 / 2 The contents of X, KX and NaX; among which the Gapon equations for the three cation exchange molecules are Ca 2+ Exchange Mg 2+ Equation, Ca 2+ Swap K + Equation, Ca 2+ Exchange Na + equation:

[0046] The error index obtained from solving the nonlinear equations is used as the internal cycle standard ε2 for complexation reaction-cation exchange. If the error index obtained from solving the nonlinear equations does not reach the internal cycle standard ε2, the next complexation reaction-cation exchange cycle begins. The initial value of the complexation reaction-cation exchange simulation model is the free ion concentration value after solving the precipitation-dissolution reaction. The initial value of the cycle is the value calculated in the previous solution, until the error index obtained from solving the nonlinear equations reaches ε2.

[0047] In some embodiments, the complexation reaction includes ten types, including CaCO3. 0 CaSO4 0 CaHCO3 + MgCO3 0 MgSO4 0 MgHCO3 + KSO4 - NaCO3 - NaSO4 - NaHCO3 0 By calculating the equilibrium constant K of the complexation reaction in each simulation process c Determine the content of complexed chemical components; there are six types of cation exchange reactions, including Ca. 2+ Exchange Mg 2+ Ca 2+ Swap K + Ca 2+ Exchange Na + Mg 2+ Swap K + Mg 2+ Exchange Na + K + Exchange Na + To determine the content of exchangeable chemical components.

[0048] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0049] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0050] Figure 1 This is a flowchart of a method for simulating the chemical equilibrium of soil salt ions according to an embodiment of this application;

[0051] Figure 2 This is a flowchart of the precipitation-dissolution reaction simulation model proposed in one embodiment of this application. Detailed Implementation

[0052] Embodiments of this application are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Rather, embodiments of this application include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0053] To achieve the above objectives, this application proposes a method for simulating the chemical equilibrium of soil salt ions, comprising:

[0054] S1: Obtain multi-ion data of parameters associated with the chemical equilibrium simulation process of salt ions and construct a chemical reaction parameter database;

[0055] S2: Calculate the activity of each ion and construct a chemical solution model, which includes a precipitation-dissolution reaction simulation model and a complexation reaction-cation exchange simulation model. A chemical solution is completed by solving the precipitation-dissolution reaction simulation model and the complexation reaction-cation exchange simulation model in sequence.

[0056] The initial and termination conditions of the chemical solution model are set, the parameter data are input for solution, and the concentration difference of multiple ions after two adjacent chemical solutions is used as the external loop control standard ε to determine whether to enter the next chemical solution iteration or output the simulation results to obtain the content of precipitated chemical components, complexed chemical components and exchanged chemical components of salt ions in the soil.

[0057] Specifically, in S1, among the various ion data related to the chemical equilibrium simulation process of salt ions, it is necessary to acquire and collect data on basic ions in the soil of the study area. The various ions related to the chemical equilibrium simulation process of salt ions include calcium ions, magnesium ions, potassium ions, sodium ions, carbonate ions, sulfate ions, bicarbonate ions, and chloride ions.

[0058] A database of chemical reaction parameters was constructed, including the charge number, hydrated ionic radius, Debye-Hückel constant, solubility product constant of precipitation-dissolution reaction, equilibrium constant of complexation reaction, and Gapon selectivity coefficient of cation exchange reaction for different chemical components (i.e., all charged chemical components, including free ions and charged complexes).

[0059] Specifically, in S2, the activities of different ions are calculated based on the basic data. The calculation method for each ion activity is as follows:

[0060] a i =γ i m i

[0061] In the formula, a i m represents the activity of the component, dimensionless; i The molar concentration of the component is mol / L; γ i The activity coefficient is L / mol; i represents a certain component;

[0062] The activity coefficient of the charged component is calculated as follows:

[0063]

[0064] I represents the ionic strength in mol / L; m i The molar concentration of the charged component is mol / L; z i Let r be the charge number of charged component i; i represents a charged component, including free ions and charged complexes; A' and B' are Debye-Hückel constants, and r is the charge number of the charged component i. i The hydrated ionic radius of component i is 10. -10 m;

[0065] The activity coefficient of an electrically neutral complex is lgγ = a'I

[0066] Where a' is an empirical coefficient; I is the ionic strength in mol / L.

[0067] In the S2 chemical solution model, the chemical solution model includes a precipitation-dissolution reaction simulation model and a complexation reaction-cation exchange simulation model. By setting the initial and termination conditions for the iterative operation of the chemical solution model, the parameter data is input for solution. That is, the precipitation-dissolution reaction simulation model and the complexation reaction-cation exchange simulation model are solved sequentially to complete one chemical solution. One chemical solution can be understood as setting the initial and termination conditions for the iterative operation of the chemical solution model, inputting the parameter data to start one chemical solution, and first calculating the parameter data through the precipitation-dissolution reaction simulation model. If the termination condition of the precipitation-dissolution reaction simulation model is not met, the precipitation-dissolution reaction solution continues in the precipitation-dissolution reaction simulation model until the termination condition is met. Then, the parameter data is input into the complexation reaction-cation exchange simulation model for complexation reaction-cation exchange solution. If the termination condition of the complexation reaction-cation exchange simulation model is not met, the complexation reaction-cation exchange solution continues in the complexation reaction-cation exchange simulation model until the termination condition is met.

[0068] Based on the established termination conditions for the iterative operation of the chemical solution model, it is determined whether the termination conditions have been met after one chemical solution iteration. If the termination conditions have been met, the simulation results are output, yielding the contents of precipitated, complexed, and exchangeable chemical components of salt ions in the soil. If the termination conditions have not been met, the next chemical solution iteration begins, and this process is repeated until the termination conditions are met and the simulation results are output. In this embodiment, the concentration difference of various ions after two consecutive chemical solutions is used as the external loop control standard ε to determine whether to proceed to the next chemical solution iteration or output the simulation results.

[0069] The known precipitation-dissolution reaction simulation model and the complexation reaction-cation exchange simulation model both have initial and termination conditions for iterative operation. Specifically, the precipitation-dissolution reaction simulation model includes precipitation-dissolution reaction sub-models for five minerals, namely CaCO3, MgCO3, CaSO4, MgSO4, and NaCl.

[0070] The precipitation-dissolution reaction of CaCO3 in the CaCO3 precipitation-dissolution reaction sub-model is shown in the following equation:

[0071]

[0072] The solubility product constant of the precipitation-dissolution reaction of CaCO3 In the formula, () represents activity;

[0073] The precipitation-dissolution reaction sub-model for MgCO3 is shown in the following equation:

[0074]

[0075] Solubility product constant of MgCO3 precipitation-dissolution reaction In the formula, () represents activity;

[0076] CaSO4 precipitation-dissolution reaction sub-model

[0077] The precipitation-dissolution reaction of CaSO4 is shown in the following equation:

[0078] The solubility product constant of the precipitation-dissolution reaction of CaSO4 In the formula, () represents activity;

[0079] The precipitation-dissolution reaction sub-model for MgSO4 is shown in the following equation:

[0080]

[0081] Solubility product constant of MgSO4 precipitation-dissolution reaction In the formula, () represents activity;

[0082] The NaCl precipitation-dissolution reaction sub-model is shown in the following equation:

[0083]

[0084] Solubility product constant of NaCl precipitation-dissolution reaction In the formula, () represents activity.

[0085] The algorithm solves for the precipitation-dissolution reaction sub-models of CaCO3, MgCO3, CaSO4, and NaCl in ascending order of solubility to complete one precipitation-dissolution cycle. The initial concentrations of all free ions used in each precipitation-dissolution cycle are the same. First, it determines whether a certain mineral needs to be calculated. If the measured concentration of any salt ion molecule composing a certain mineral is 0, the sub-module for that mineral is skipped. For example, if the measured carbonate ion content is 0, the CaCO3 and MgCO3 precipitation-dissolution reaction sub-models are skipped.

[0086] The solution process for the CaCO3 precipitation-dissolution reaction sub-model, MgCO3 precipitation-dissolution reaction sub-model, CaSO4 precipitation-dissolution reaction sub-model, MgSO4 precipitation-dissolution reaction sub-model, and NaCl precipitation-dissolution reaction sub-model is the same, as follows: Figure 2 The steps shown are as follows:

[0087] For each mineral, first calculate the activity product of that mineral in solution, when Q sp ≠ Solubility product constant K of mineral precipitation-dissolution reaction sp Precipitation or dissolution will occur, and the amount of mineral precipitation or dissolution ΔC will be calculated; where Figure 2 [] indicates concentration (mol / L); C1 is the concentration (mol / L) of minerals already present in the solution in the current iteration step;

[0088] When Q sp ≠ Solubility product constant K of mineral precipitation-dissolution reaction sp If precipitation occurs, the following equation will be satisfied when equilibrium is reached:

[0089] γ2(C2-ΔC)γ3(C3-ΔC)=K sp

[0090] In the formula, γ2 is the activity coefficient of the cations that make up the mineral; γ3 is the activity coefficient of the anions that make up the mineral; C2 is the concentration of the cations that make up the mineral (mol / L); and C3 is the concentration of the anions that make up the mineral (mol / L).

[0091] When Q sp ≠ Solubility product constant K of mineral precipitation-dissolution reaction sp If precipitation occurs, the following equation will be satisfied when equilibrium is reached:

[0092] γ2(C2+ΔC)γ3(C3+ΔC)=K sp

[0093] In the formula, γ2 is the activity coefficient of the cations that make up the mineral; γ3 is the activity coefficient of the anions that make up the mineral; C2 is the concentration of the cations that make up the mineral (mol / L); and C3 is the concentration of the anions that make up the mineral (mol / L).

[0094] ΔC can be calculated as follows:

[0095]

[0096] In the formula, γ2 is the activity coefficient of the cations that make up the mineral; γ3 is the activity coefficient of the anions that make up the mineral; C2 is the concentration of the cations that make up the mineral (mol / L); and C3 is the concentration of the anions that make up the mineral (mol / L).

[0097] Determine Q sp Is it greater than K? sp If Q sp >K sp This indicates that the solution is supersaturated with the mineral, resulting in precipitation and a decrease in the concentration of free ions. If Q sp <K sp This indicates that the solution is undersaturated with respect to the mineral, which can be divided into three cases: If the mineral is not present in the soil in the current iteration step, no dissolution will occur, and the free ion concentration remains unchanged; if the mineral is present in the solution, dissolution will occur, and the free ion concentration will increase; if the concentration of the mineral already present in the solution in the current iteration step, C1 mol / L, is greater than the calculated precipitation amount ΔC, then only some minerals will dissolve, and dissolution will stop after reaching the solubility product constant; if the concentration of the mineral already present in the solution in the current iteration step, C1 mol / L, is less than the calculated precipitation amount ΔC, then all minerals will dissolve.

[0098] For the initial solutions of the CaCO3, MgCO3, CaSO4, and NaCl precipitation-dissolution sub-models, the measured concentrations of each salt ion are used as the initial concentrations of free ions. The initial concentrations of other precipitates and complexes are set to 0. Precipitation-dissolution calculations are performed on the five minerals in ascending order of solubility. After each mineral sub-module is completed, the concentrations of anions and cations composing that mineral and the concentration of that precipitate can be obtained. The concentration difference of the same free ion after solving different minerals is used as the internal cycle standard ε1 of the precipitation-dissolution cycle. If the concentration difference of the same free ion after solving different minerals does not reach ε1, the next precipitation-dissolution cycle begins. At the same time, the free ion concentration calculated by the mineral with low solubility is used as the initial concentration value of that free ion in the next precipitation-dissolution cycle, until the concentration difference of the same free ion after solving different minerals reaches ε1.

[0099] For example, CaCO3 and CaSO4 will both result in the calculation of Ca. 2+ If the difference between the two concentrations does not meet the convergence criterion, then the Ca calculated using CaCO3... 2 The concentration is set as the new initial value for the next precipitation-dissolution cycle. The internal circulation standard of the precipitation-dissolution cycle can be expressed by the following formula:

[0100]

[0101] in

[0102]

[0103]

[0104]

[0105] In the formula, These are the Ca values ​​obtained from precipitation-dissolution calculations of different minerals. 2 + Mg 2+ CO3 2- SO4 2- The concentration difference (mol / L).

[0106] In some embodiments, the complexation reaction-cation exchange simulation model solves for both the complexation reaction and the cation exchange reaction simultaneously, as follows:

[0107] By simultaneously establishing the mass action equations for ten complexation reactions, the Gapon equations for three of the six cation exchange reactions, the CEC conservation equation, and the mass conservation equations for eight salt ions, and simplifying them, a nonlinear equation system containing eleven unknowns is obtained. Solving for the unknowns completes one complexation reaction-cation exchange cycle. The unknowns are the concentrations of free ions other than chloride ions and the four exchangeable cations Ca2+. 1 / 2 X, Mg 1 / 2 The contents of X, KX and NaX; among which the Gapon equations for the three cation exchange molecules are Ca 2+ Exchange Mg 2+ Equation, Ca 2+ Swap K + Equation, Ca 2+ Exchange Na + equation:

[0108] Complexation reactions and cation exchange reactions have relatively short reaction times and can be considered to be in a state of chemical equilibrium, allowing them to be solved simultaneously. There are ten types of complexation reactions, including CaCO3. 0 CaSO4 0 CaHCO3 + MgCO3 0 MgSO4 0 MgHCO3 + KSO4 - NaCO3 - NaSO4 - NaHCO3 0 By calculating the equilibrium constant K of the complexation reaction in each simulation process c The content of the complexed chemical components was determined; the corresponding complexation reaction equations are shown below:

[0109] CaCO3 0 :

[0110] CaSO4 0 :

[0111] CaHCO3 + :

[0112] MgCO3 0 :

[0113] MgSO4 0 :

[0114] MgHCO3 + :

[0115] KSO4 - :

[0116] NaCO3 - :

[0117] NaSO4 - :

[0118] NaHCO3 0 :

[0119] Among them, K c This is the equilibrium constant for complexation reactions. Its subscript is used to distinguish the ten types of complexation reactions, which will not be elaborated further.

[0120] A cation exchange reaction simulation was conducted to determine the content of exchangeable chemical components. There are six types of cation exchange reactions, and the corresponding Gapon equations for cation exchange are shown below: where K G Gapon selectivity coefficient for cation exchange;

[0121] Ca 2+ Exchange Mg 2+ :

[0122] Ca 2+ Swap K + :

[0123] Ca 2+ Exchange Na + :

[0124] Mg 2+ Swap K + :

[0125] Mg2+ Exchange Na + :

[0126] K + Exchange Na + :

[0127] The complexation reaction-cation exchange submodule needs to solve for the content of each dissolved component in the soil solution and the content of each exchangeable cation in the soil colloid when the solution reaches chemical equilibrium. This involves 8 free ions, 10 complexes, and 4 exchangeable cations, totaling 22 unknowns. The 22 independent equations consist of 10 mass action equations for complexation reactions and 3 Gapon equations for cation exchange (three of these Gapon equations are selected in the model as Ca...). 2+ Exchange Mg 2+ Equation, Ca 2+ Swap K + Equation, Ca 2+ Exchange Na + The equations are as follows: the CEC conservation equation and the mass conservation equation for the 8 salt ions.

[0128] CEC = Ca 1 / 2 X+Mg 1 / 2 X+KX+NaX

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136] Cl T =[Cl - ]

[0137] In the formula, Ca 1 / 2 X, Mg 1 / 2X, KX, and NaX represent the exchange capacities (meq / 100g) of four cations in the soil, indicating the maximum adsorption capacity of the soil for these four cations; the subscript T indicates the total amount of dissolved salt ions (mol / L); [] indicates the concentration (mol / L). Combining the above 22 equations and simplifying, we obtain a nonlinear equation system containing 11 unknowns, excluding Cl. - The concentrations of the other 7 free ions and the contents of the 4 exchangeable cations are shown below:

[0138]

[0139] In the formula, the units for exchangeable cation content and CEC are meq / 100g. Kr is an intermediate coefficient, calculated as follows:

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150] In the formula, γ represents the activity coefficient, and its subscript is used to distinguish each ion; Kc is the equilibrium constant of the complexation reaction, and the subscript of Kc is used to distinguish them, which will not be elaborated further.

[0151] The error index obtained by solving the nonlinear equation system is used as the internal cycle standard ε2 for complexation reaction-cation exchange. When the error index obtained by solving the nonlinear equation system does not reach ε2, the next complexation reaction-cation exchange cycle begins. The initial value of the complexation reaction-cation exchange simulation model is the free ion concentration value after solving the precipitation-dissolution reaction. If the nonlinear equation system of complexation reaction-cation exchange needs to be solved iteratively, the initial value of each recycle is the value calculated in the previous cycle, until the error index obtained by solving the nonlinear equation system reaches ε2.

[0152] Example 1

[0153] The measured soil salt ion concentrations at the three sampling points are shown in Table 1.

[0154] Table 1. Measured salt ion concentrations (mg / L) at three sampling points.

[0155]

[0156] A database of chemical reaction parameters was constructed, including the charge number, hydrated ionic radius, Debye-Hückel constant, solubility product constant of precipitation-dissolution reaction, equilibrium constant of complexation reaction, and Gapon selectivity coefficient of cation exchange reaction for various ions. The activities of each ion were calculated, and the parameter values ​​required for calculating the activity coefficients of different components are shown in Table 2.

[0157] Table 2. Parameter values ​​required for calculating the activity coefficients of different components.

[0158]

[0159]

[0160] The solubility product constants of the five minerals are shown in Table 3.

[0161] Table 3. Solubility product constants of five minerals

[0162]

[0163] The equilibrium constants for the ten complexation reactions are shown in Table 4.

[0164] Table 4. Equilibrium constants for ten complexation reactions

[0165]

[0166] The Gapon selectivity coefficient values ​​are shown in Table 5.

[0167] Table 5. Values ​​of Gapon Selectivity Coefficient

[0168]

[0169] The parameter data were input into the chemical solution model to simulate the chemical equilibrium of soil salt ions and the simulation results were output as shown in Table 6.

[0170] Table 6 Simulation results of soil chemical component content

[0171]

[0172]

[0173] It should be noted that in the description of this application, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0174] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0175] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0176] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for simulating the chemical equilibrium of soil salt ions, characterized in that, include: Acquire multiple ion data related to parameters in the chemical equilibrium simulation process of salt ions and construct a chemical reaction parameter database; The activity of each ion is calculated and a chemical solution model is constructed. The chemical solution model includes a precipitation-dissolution reaction simulation model and a complexation reaction-cation exchange simulation model. A chemical solution is completed by solving the precipitation-dissolution reaction simulation model and the complexation reaction-cation exchange simulation model in sequence. The calculation methods for the activities of each ion are as follows: In the formula, a i The molar concentration scale activity of the component, in mol / L; m i The molar concentration of the component is expressed in mol / L. γ i The activity coefficient is dimensionless. i Represents a certain component; The activity coefficient of the charged component is calculated as follows: I Ionic strength, mol / L; z i Charged components i The number of charges; i It represents a charged component, including free ions and charged complexes; A '、 B ' is the Debye-Hückel constant, r i for i The hydrated ionic radius of the component is 10. -10 m; Activity coefficient of electrically neutral complexes in γ The activity coefficient of the electrically neutral complex; a ' is an empirical coefficient, in L / mol; I Ionic strength, mol / L; The precipitation-dissolution reaction simulation model includes five precipitation-dissolution reaction sub-models for five minerals: CaCO3, MgCO3, CaSO4, MgSO4, and NaCl. The precipitation-dissolution reaction simulation method includes: The precipitation-dissolution reaction sub-models of the five minerals are solved sequentially according to their solubility from smallest to largest to complete one precipitation-dissolution cycle; the initial concentration values ​​of each free ion used in one precipitation-dissolution cycle are the same; The concentration difference of the same free ion after solving different minerals is used as the internal circulation standard for the precipitation-dissolution cycle. ε 1; When the concentration difference of the same free ion after solving different minerals does not reach ε If the concentration of free ions is less soluble, the next precipitation-dissolution cycle will begin. Simultaneously, the concentration of free ions calculated for the mineral with lower solubility will be used as the initial concentration for the next precipitation-dissolution cycle, until the concentration difference of the same free ion among different minerals reaches a certain value. ε 1; The solution process for the CaCO3 precipitation-dissolution reaction sub-model, the MgCO3 precipitation-dissolution reaction sub-model, the CaSO4 precipitation-dissolution reaction sub-model, the MgSO4 precipitation-dissolution reaction sub-model, and the NaCl precipitation-dissolution reaction sub-model is the same; including the following steps: (1) Calculate the activity product of minerals in the solution. Q sp ;when Q sp ≠ Solubility product constant of mineral precipitation-dissolution reaction K sp Calculate the amount of mineral precipitation or dissolution. C ;judge Q sp Is it greater than K sp If "yes", the solution is supersaturated with the mineral and a precipitate forms; if "no", the solution is undersaturated with the mineral and the mineral dissolves. Dissolution includes one of the following scenarios: If the mineral is not present in the soil in the current iteration step, then the mineral will not dissolve and its free ion concentration will remain unchanged. b. Concentration of minerals already present in the solution in the current iteration step C 1 mol / L greater than C If the mineral partially dissolves until the solubility product constant is reached; c. The concentration of minerals already present in the solution in the current iteration step. C 1 mol / L less C If so, the mineral will completely dissolve; The complexation reaction-cation exchange simulation model solves for both complexation and cation exchange reactions simultaneously, as follows: By simultaneously establishing the mass action equations for ten complexation reactions, the Gapon equations for three of the six cation exchange reactions, the CEC conservation equation, and the mass conservation equations for eight salt ions, and simplifying them, a nonlinear equation system containing eleven unknowns is obtained. Solving for the unknowns completes one complexation reaction-cation exchange cycle. The unknowns are the concentrations of free ions other than chloride ions and the four exchangeable cations Ca2+. 1 / 2 X, Mg 1 / 2 The contents of X, KX and NaX; among which the Gapon equations for the three cation exchange molecules are Ca 2+ Exchange Mg 2+ Equation, Ca 2+ Swap K + Equation, Ca 2+ Exchange Na + equation: The error index of solving the aforementioned nonlinear equation system is used as the internal circulation standard for complexation reaction-cation exchange. ε 2; When the error index of solving the nonlinear equation system does not meet the inner loop criterion. ε 2. Then proceed to the next complexation reaction-cation exchange cycle; the initial value of the complexation reaction-cation exchange simulation model is the free ion concentration value after solving the precipitation-dissolution reaction; the initial value of the cycle is the value calculated in the previous solution, until the error index of the solution of the nonlinear equation system reaches... ε 2; The initial and termination conditions of the chemical solution model are set, the parameter data is input for solution, and the concentration difference of multiple ions after two adjacent chemical solutions is used as the external loop control standard ε to determine whether to enter the next chemical solution iteration or output the simulation results to obtain the content of precipitated chemical components, complexed chemical components and exchanged chemical components of salt ions in the soil.

2. The simulation method according to claim 1, characterized in that, The chemical equilibrium simulation process involving salt ions involves various ions, including calcium, magnesium, potassium, sodium, carbonate, sulfate, bicarbonate, and chloride ions.

3. The simulation method according to claim 2, characterized in that, The database contains the charge number, hydrated ionic radius, Debye-Hückel constant, solubility product constant of precipitation-dissolution reaction, equilibrium constant of complexation reaction, and Gapon selectivity coefficient of cation exchange reaction for various ions.

4. The simulation method according to claim 1, characterized in that, The precipitation-dissolution reaction of CaCO3 in the CaCO3 precipitation-dissolution reaction sub-model is shown in the following equation: The solubility product constant of the precipitation-dissolution reaction of CaCO3 ; The precipitation-dissolution reaction of MgCO3 in the MgCO3 precipitation-dissolution reaction sub-model is shown in the following equation: The solubility product constant of the precipitation-dissolution reaction of MgCO3 ; The precipitation-dissolution reaction of CaSO4 in the CaSO4 precipitation-dissolution reaction sub-model is shown in the following equation: The solubility product constant of the precipitation-dissolution reaction of CaSO4 ; The precipitation-dissolution reaction of MgSO4 in the MgSO4 precipitation-dissolution reaction sub-model is shown in the following equation: The solubility product constant of the precipitation-dissolution reaction of MgSO4 ; The NaCl precipitation-dissolution reaction in the NaCl precipitation-dissolution reaction sub-model is shown in the following equation: The solubility product constant of the precipitation-dissolution reaction of NaCl In each formula, ( ) represents activity.

5. The simulation method according to claim 1, characterized in that, Internal iterative convergence index of precipitation-dissolution cycle It can be expressed by the following formula: in ; ； ； ； In the formula, , , , These are the Ca values ​​obtained from precipitation-dissolution calculations of different minerals. 2+ Mg 2+ CO3 2- SO4 2- The concentration difference (mol / L).

6. The simulation method according to claim 1, characterized in that, There are ten types of complexation reactions, including CaCO3. 0 CaSO4 0 CaHCO3 + MgCO3 0 MgSO4 0 MgHCO3 + KSO4 - NaCO3 - NaSO4 - NaHCO3 0 By calculating the equilibrium constant of the complexation reaction in each simulation process K c Determine the content of complexed chemical components; there are six types of cation exchange reactions, including Ca. 2+ Exchange Mg 2+ Ca 2 + Swap K + Ca 2+ Exchange Na + Mg 2+ Swap K + Mg 2+ Exchange Na + K + Exchange Na + To determine the content of exchangeable chemical components.

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