Multi-type heavy metal distribution rapid calculation method in dredged soil bottom throwing process

Abstract

The invention discloses a rapid calculation method for multi-type heavy metal distribution in a dredged soil bottom throwing process, which comprises the following steps: measuring the mass ratio of various heavy metals to a dredged soil sample to obtain the solid content ratio of various heavy metals in dredged soil; collecting the temperature of a water body, performing particle size grade screening on the dredged soil, and calculating balance distribution coefficients of a heavy metal dissolved state and a particle state; establishing a rapid calculation model of the concentration of the dissolved heavy metals and the concentration of the suspended particulate heavy metals in the overlying water body; according to the deposition thickness, the mixing thickness and the dry volume weight of the sediments, calculating the heavy metal-containing sediment concentration and the total sediment concentration after the bottom bed sediments are mixed; and establishing a rapid calculation model for the concentrations of the dissolved heavy metals and the bottom bed granular heavy metals in the interstitial water body. According to the method, plankton and benthos environments are considered, toxic heavy metal environment monitoring, management and treatment in the bottom throwing operation are realized, and rapid, efficient, total-space and multi-type heavy metal distribution evaluation requirements in the bottom throwing operation process are met.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal assessment in dredged water bodies, and in particular to a method for quickly calculating the distribution of multiple types of heavy metals in a dredged soil bottom dumping process. Background Art

[0002] At present, the diffusion and deposition of toxic heavy metals caused by the bottom dumping of dredged soil in rivers or offshore areas may cause great harm to aquatic ecosystems, especially predators at the top of the food chain. The assessment of dissolved and particulate heavy metals in the bottom dumping process often requires a lot of manpower and material resources for sampling and measurement. At the same time, due to the dynamic nature of the bottom dumping process, the representativeness of the sampling is also greatly limited. In addition, the use of mathematical models to calculate the distribution of heavy metals requires complex calculations of hydrodynamics, sediment and multiple heavy metal variables. The model establishment process is complicated and the timeliness of the calculation is difficult to guarantee. At the same time, it is difficult for existing models to effectively calculate the concentration of heavy metals in the interstitial water and sediments of the bottom bed. These limitations make it difficult for existing technical means to meet the needs of rapid, efficient, full-space and multi-type heavy metal distribution assessment.

[0003] To this end, we designed a fast calculation method for the distribution of multiple types of heavy metals in the dredged soil bottom dumping process to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the existing technical means for evaluating heavy metals in the process of dredged soil bottom dumping are difficult to meet the needs of rapid, efficient, full-space and multi-type heavy metal distribution evaluation, and a method for rapid calculation of the distribution of multiple types of heavy metals in the process of dredged soil bottom dumping is proposed. Based on various rapid calculation models, the distribution of multiple types of heavy metals in the full space of the water environment during the process of dredged soil bottom dumping is rapidly calculated.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for quickly calculating the distribution of multiple types of heavy metals in the process of dredged soil bottom dumping, the method mainly comprises the following steps:

[0007] Step S1, pre-processing of the solid content ratio of heavy metals, by drying and digesting the dredged soil, measuring the ratio of the mass of various heavy metals to the mass of the dredged soil sample, and obtaining the solid content ratio of various heavy metals in the dredged soil;

[0008] Step S2, obtaining the equilibrium distribution coefficient of heavy metals, by collecting the water temperature, screening the dredged soil by particle size, and calculating the equilibrium distribution coefficient of heavy metals in dissolved and granular states at different particle size levels;

[0009] Step S3, calculating the concentration of dissolved and particulate heavy metals in the overlying water, calculating the diffusion concentration of dredged soil and the thickness of sediment in the overlying water according to the dredged soil bottom dumping diffusion model, and establishing a rapid calculation model for the concentration of dissolved heavy metals and the concentration of suspended particulate heavy metals in the overlying water under equilibrium state;

[0010] Step S4, calculating the effective sediment concentration in the bottom sediment, based on the sediment thickness, mixed thickness, and dry bulk density in the sediment, taking into account the mixing process of new sediment and historical sediment, calculating the heavy metal sediment concentration and total sediment concentration after mixing the bottom sediment;

[0011] Step S5, calculate the concentrations of dissolved and particulate heavy metals in interstitial water, establish a rapid calculation model for the concentrations of dissolved heavy metals in interstitial water and particulate heavy metals in the bottom bed, and realize rapid acquisition of the concentrations of dissolved heavy metals in the interstitial water area and particulate heavy metals in the sediment bed area.

[0012] As a further preferred solution of the present invention, in step S1, the process of obtaining the solid content ratio of various heavy metals in the dredged soil is as follows:

[0013] Collect representative dredged soil samples from the dredged soil, ensure that the sampling points are evenly covered and representative of the environment, remove debris from the dredged soil samples, and mix them evenly;

[0014] The dredged soil samples were dried to constant weight, and ground into uniform fine powder using a mortar and pestle, and the dry mass of the dredged soil samples was weighed;

[0015] According to the wet digestion method, weigh the dredged soil sample, add the digestion reagent, place it in a microwave digestion instrument for digestion, cool and fix the volume after completion, and measure the fixed volume;

[0016] The mass concentration of various heavy metals was determined by atomic emission spectrometry, and the solid content ratio of various heavy metals was obtained according to the following formula: :

[0017] .

[0018] As a further preferred solution of the present invention, in step S2, the process of obtaining the equilibrium distribution coefficient of heavy metals includes:

[0019] The water temperature was collected, and the dredged soil was screened by particle size using a laser particle size analyzer. The equilibrium distribution coefficients of dissolved and particulate heavy metals of various types were calculated at different particle size levels:

[0020] ;

[0021] In the above formula, Representative The median particle size of heavy metals in dredged soil is In the group, when the temperature is T, the equilibrium distribution coefficient of heavy metal dissolved and particulate state; is the standard distribution coefficient, Factors that characterize the effect of temperature change on the equilibrium partition coefficient, represents the median particle size of the dredged soil component, Characterize the influence coefficient of different specific surface areas of different median particle size groups on the adsorption capacity of heavy metals.

[0022] As a further preferred solution of the present invention, in step S3, the dredged soil bottom dumping diffusion model is used to calculate the sediment content and sediment thickness in the overlying water body during the dredged soil bottom dumping process, and a rapid acquisition model for the concentration of dissolved heavy metals and the concentration of suspended heavy metals in the overlying water body under equilibrium state is established to achieve rapid acquisition of the concentration of dissolved heavy metals and the concentration of suspended heavy metals in the overlying water body;

[0023] Step S31, the dredged soil bottom dump diffusion model calculation formula of the dredged soil bottom dump diffusion sand content and sediment thickness is as follows:

[0024] ;

[0025] ;

[0026] In the formula, It is the calculated transitional sediment content after the diffusion process of dredged soil occurs and before the settlement process occurs. Points within the diffusion range of dredged materials The quality of dredged soil Points within the diffusion range of dredged materials The sediment content at the point, H is the water depth, K is the diffusion coefficient, Indicates the location coordinates of the dredged material dumping point, and are the average lateral and longitudinal velocities respectively, η is the cloud following coefficient, is the sediment settling velocity, To calculate the time step;

[0027] ;

[0028] In the formula, Points within the diffusion range of dredged materials After the sedimentation, the bottom siltation increases the sediment thickness. is the porosity of the bottom sediment, represents the dry bulk density of sediment;

[0029] Step S32, based on the analytical theory of dissolved and particulate heavy metals in the overlying water body under equilibrium state, a rapid acquisition model of the concentration of dissolved heavy metals in the overlying water body is established, and its expression is as follows:

[0030] ;

[0031] In the formula, Represents the point within the range of dredged material diffusion In the overlying water Dissolved heavy metal concentrations, Representative The solid content ratio of heavy metals in dredged materials is Representative The equilibrium distribution coefficient of heavy metals at a specific temperature, is the porosity in water;

[0032] Step S33, based on the analytical theory of dissolved and particulate heavy metals in the overlying water body under equilibrium state, a rapid calculation model for the concentration of particulate heavy metals in the suspended matter of the overlying water body is established, and its expression is as follows:

[0033] ;

[0034] In the formula, Represents the point within the range of dredged material diffusion The suspended matter in The concentration of heavy metals in particle form, is the porosity in water.

[0035] As a further preferred solution of the present invention, in step S4, the calculation method of the heavy metal-containing sediment concentration and the total sediment concentration after the bottom sediment is mixed is as follows:

[0036] Step S41, using the exchange relationship between new sediments and surface sediments, in the process of calculating the heavy metal concentration distribution in the bottom sediments and interstitial water, the mixing process of new sediments and historical sediments is taken into account to calculate the concentration of heavy metal-containing sediment in the bottom sediments after mixing. :

[0037] ;

[0038] In the formula, Represents the point within the range of dredged material diffusion The concentration of heavy metals in the mixed sediments is Points within the diffusion range of dredged materials After the sedimentation, the bottom siltation increases the sediment thickness. Points within the diffusion range of dredged materials The cumulative thickness of sediments accumulated after sedimentation at the bottom increases. The thickness represents the mixing of historical sediments with new sediments under the action of dynamic and biological disturbance. represents the dry bulk density of sediment;

[0039] Step S42: After mixing, the particulate heavy metals in the bottom sediment and the dissolved heavy metals in the interstitial water are balanced. At this time, the total sediment concentration after mixing the bottom sediment is :

[0040] ;

[0041] In the formula, Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, The porosity of the bottom sediment.

[0042] As a further preferred solution of the present invention, in step S5, by establishing a rapid calculation model for the concentration of dissolved heavy metals in the interstitial water and the concentration of particulate heavy metals in the bottom bed, the concentration of dissolved heavy metals in the interstitial water area and the concentration of particulate heavy metals in the sediment bed area are rapidly obtained, including:

[0043] Step S51, using the analytical theory of dissolved heavy metals in interstitial water and particulate heavy metals in bottom sediments, a rapid calculation model for the concentration of dissolved heavy metals in interstitial water is established, and its expression is as follows:

[0044] ;

[0045] In the formula, Represents the point within the range of dredged material diffusion The gap water Dissolved heavy metal concentrations, Representative The solid content ratio of heavy metals in dredged materials is Represents the point within the range of dredged material diffusion The concentration of heavy metals in the mixed sediments is Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, is the porosity of the bottom sediment, Representative Equilibrium partition coefficients of heavy metals at specific temperatures;

[0046] Step S52, using the analytical theory of dissolved heavy metals in interstitial water and particulate heavy metals in bottom sediments, a rapid calculation model for the concentration of particulate heavy metals in the interstitial water is established, and its expression is as follows:

[0047] ;

[0048] In the formula, Represents the point within the range of dredged material diffusion The bottom sediments at The concentration of heavy metals in particle form, Representative The solid content ratio of heavy metals in dredged materials is Represents the point within the range of dredged material diffusion The concentration of heavy metals in the mixed sediments is Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, is the porosity of the bottom sediment, Representative The equilibrium distribution coefficient of heavy metals at a specific temperature.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows: the rapid calculation model of heavy metal distribution of the present invention does not need to be iteratively calculated through the traditional water flow-sediment-heavy metal coupling calculation equation group, especially the convection diffusion transmission equation of multiple types of heavy metal concentration parameters and the net flux equation of heavy metals from the sediment bed to the overlying water. The concentration of heavy metal dissolved and particulate states can be directly calculated and obtained in the form of a rapid calculation model under equilibrium state, which improves the timeliness and simplicity of calculation and avoids the representative limitations of large-scale sampling monitoring. By introducing the bottom bed sediment mixing process and the equilibrium state analysis process of heavy metal concentration in intermittent water, the rapid calculation of the concentration distribution in the entire space of the water environment, such as the dissolved state of the overlying water body, the dissolved state of the interstitial water body, the suspended particulate state, and the bottom bed sediment particulate state, can be simultaneously realized, thereby providing data support for the evaluation of the heavy metal environmental suitability of plankton in the water body and benthic organisms in the sediment bed under actual conditions. By proposing a calculation scheme for the equilibrium distribution coefficients of dissolved and particulate heavy metals under different types, different temperatures and different particle size distributions, the bottom throwing process of dredged materials under conditions of complex particle size distribution of dredged materials, temperature changes in water areas and pollution by various toxic heavy metals can be better calculated, thereby improving the reliability and accuracy of the evaluation of heavy metal distribution and transport processes.

[0050] The present invention takes into account both the plankton and benthic environments, realizes environmental monitoring, management and treatment of toxic heavy metals in bottom disposal operations, and meets the needs of rapid, efficient, full-space and multi-type heavy metal distribution assessment during bottom disposal operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of a flow chart of a method for rapidly calculating the distribution of multiple types of heavy metals in a dredged soil bottom dumping process proposed by the present invention; Figure 2 This is a schematic diagram of the heavy metal transmission process in the entire water environment of an embodiment of the present invention; Figure 3This is a schematic diagram of the calculation results of the concentration diffusion of dissolved heavy metals in the overlying water body near the bottom dumping point in an embodiment of the present invention; Figure 4 Schematic diagram of the calculation result of the diffusion of heavy metal concentration in sediment particles in the interstitial water body at points near the bottom throwing point in the embodiment of the present invention; Figure 5 Graph showing particle size distribution in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0053] Reference Figure 1 The present embodiment proposes a method for quickly calculating the distribution of multiple types of heavy metals in the process of dredged soil dumping, which is based on a fast calculation model for quickly calculating the distribution of multiple types of heavy metals in the whole space of the water environment during the process of dredged soil dumping. The method comprises the following steps:

[0054] Step S1, heavy metal solid content ratio pretreatment, through the dredged soil drying and digestion treatment, measuring the mass ratio of various heavy metals and the mass of the dredged soil sample, to obtain the solid content ratio of various heavy metals in the dredged soil.

[0055] The various heavy metals referred to in this embodiment include lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn) and other heavy metals.

[0056] The process of obtaining the solid content ratio of various heavy metals in dredged soil is as follows:

[0057] Step S11, collecting representative dredged soil samples from the dredged soil, ensuring that the sampling points are evenly covered and representative of the environment, removing debris from the dredged soil samples, and mixing them evenly;

[0058] Step S12, drying the dredged soil sample after the above pretreatment to a constant weight, grinding the dredged soil sample into uniform fine powder using a mortar, and weighing the dry mass of the dredged soil sample;

[0059] Step S13, weighing the digestion reagent added to the dredged soil sample according to the wet digestion method (polytetrafluoroethylene is preferably used in this embodiment), placing it in a microwave digestion instrument for digestion according to the set program, cooling and fixing the volume after completion, and measuring the fixed volume;

[0060] Step S14, using atomic emission spectrometry (inductively coupled plasma emission spectrometry is preferred in this embodiment) to simultaneously measure the mass concentration of various heavy metals, and the solid content ratio of various heavy metals is obtained according to the following formula: :

[0061] .

[0062] The test obtains the content ratio of Pb (lead), Cd (cadmium), Cu (copper) and Zn (zinc).

[0063] Step S2, obtaining the equilibrium distribution coefficient of heavy metals, by collecting the water temperature, screening the dredged soil by particle size, and calculating the equilibrium distribution coefficient of heavy metals in dissolved state and particle state at different particle size levels; the process of obtaining the equilibrium distribution coefficient of heavy metals includes:

[0064] The water temperature is collected. The temperature change has an exponential effect on the distribution coefficient, which can characterize the change of the distribution coefficient with the water temperature variable. At the same time, the distribution coefficient is related to the sediment particle size, especially the difference in the adsorption capacity of clay and sand for heavy metals. Therefore, the particle size screening is performed for the sieve holes between the dredged soil. The equilibrium distribution coefficients of dissolved and particulate states of various types of heavy metals are calculated at different particle size levels:

[0065] ;

[0066] In the above formula, Representative The median particle size of heavy metals in dredged soil is In the group, when the temperature is T, the equilibrium distribution coefficient of heavy metal dissolved and particulate state; is the standard partition coefficient at 20°C, Factors that characterize the effect of temperature change on the equilibrium partition coefficient, represents the median particle size of the dredged soil component, Characterizes the influence coefficient of different specific surface areas of different median particle size groups on the adsorption capacity of heavy metals. Generally, the smaller the particle size, the larger the surface area to volume ratio (specific surface area), and the stronger the ability to adsorb heavy metals for transportation.

[0067] Step S3, calculation of the concentration of dissolved and particulate heavy metals in the overlying water, calculation of the diffusion concentration of dredged soil and the thickness of sediment in the overlying water according to the dredged soil bottom dumping diffusion model, and establishment of a rapid calculation model for the concentration of dissolved heavy metals and the concentration of suspended particulate heavy metals in the overlying water under equilibrium state. Figure 2 Represents the distribution of heavy metals in the water environment where bottom-cast vessels are located.

[0068] The dredged soil bottom dumping diffusion model is used to calculate the sediment content and sediment thickness in the overlying water body during the dredged soil bottom dumping process. According to the analytical theory of dissolved heavy metals in the overlying water body, the heavy metal concentration distribution is quickly calculated, and a rapid acquisition model for the concentration of dissolved heavy metals and suspended heavy metal particles in the overlying water body under equilibrium state is established to achieve rapid acquisition of the concentration of dissolved heavy metals and suspended heavy metal particles in the overlying water body.

[0069] The calculation steps are as follows:

[0070] Step S31, the dredged soil bottom dump diffusion model calculation formula of the dredged soil bottom dump diffusion sand content and sediment thickness is as follows:

[0071] ;

[0072] ;

[0073] in, It is the calculated transitional sediment content after the diffusion process of dredged soil occurs and before the settlement process occurs. Points within the diffusion range of dredged materials The quality of dredged soil Points within the diffusion range of dredged materials The sediment content at the point, H is the water depth, K is the diffusion coefficient, Indicates the location coordinates of the dredged material dumping point, and are the average lateral and longitudinal velocities respectively, η is the cloud following coefficient, is the sediment settling velocity, is the calculation time step.

[0074] The calculation formula for obtaining the sediment thickness in the overlying water body during the dredged soil bottom dumping process using the dredged soil bottom dumping diffusion model is as follows:

[0075] ;

[0076] In the formula, Points within the diffusion range of dredged materials After the sedimentation, the bottom siltation increases the sediment thickness. is the porosity of the bottom sediment, which can be taken as 1. Represents the dry bulk density of sediment.

[0077] Step S32, based on the analytical theory of dissolved and particulate heavy metals in the overlying water body under equilibrium state, a rapid acquisition model of the concentration of dissolved heavy metals in the overlying water body is established, and its expression is as follows:

[0078] ;

[0079] In the formula, Represents the point within the range of dredged material diffusion In the overlying water Dissolved heavy metal concentrations, Representative The solid content ratio of heavy metals in dredged materials is Representative The equilibrium distribution coefficient of heavy metals at a specific temperature, It can represent various heavy metals such as lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), etc. is the porosity in water.

[0080] Step S33, based on the analytical theory of dissolved and particulate heavy metals in the overlying water body under equilibrium state, a rapid calculation model for the concentration of particulate heavy metals in the suspended matter of the overlying water body is established, and its expression is as follows:

[0081] ;

[0082] In the formula, Represents the point within the range of dredged material diffusion The suspended matter in The concentration of heavy metals in particle form, Representative The solid content ratio of heavy metals in dredged materials is Representative The equilibrium distribution coefficient of heavy metals at a specific temperature, It can represent various heavy metals such as lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), etc. is the porosity in water.

[0083] Step S4, calculating the effective sediment concentration in the bottom sediment, based on the sediment thickness, mixed thickness, and dry bulk density in the sediment, taking into account the mixing process of new sediment and historical sediment, calculates the heavy metal sediment concentration and total sediment concentration after mixing the bottom sediment.

[0084] The calculation method of heavy metal-containing sediment concentration and total sediment concentration after mixing with bottom sediment is as follows:

[0085] Step S41, using the exchange relationship between new sediments and surface sediments, in the calculation process of heavy metal concentration distribution in bottom sediments and interstitial water, the mixing process of new sediments and historical sediments is first considered, so as to calculate the concentration of heavy metal-containing sediment in the bottom sediment after mixing. :

[0086] ;

[0087] In the formula, Represents the point within the range of dredged material diffusion The concentration of heavy metals in the mixed sediments is Points within the diffusion range of dredged materials After the sedimentation, the bottom siltation increases the sediment thickness. Points within the diffusion range of dredged materials The cumulative thickness of sediments accumulated after sedimentation at the bottom increases. The thickness represents the mixing of historical sediments with new sediments under the action of dynamic and biological disturbance. Represents the dry bulk density of sediment.

[0088] Step S42: After mixing, the particulate heavy metals in the bottom sediment and the dissolved heavy metals in the interstitial water are balanced. At this time, the total sediment concentration after mixing the bottom sediment is :

[0089] ;

[0090] In the formula, Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, The porosity of the bottom sediment.

[0091] Step S5, calculate the concentration of dissolved and particulate heavy metals in interstitial water, establish a rapid calculation model for the concentration of dissolved heavy metals in interstitial water and particulate heavy metals in the bottom bed, and achieve rapid acquisition of the concentration of dissolved heavy metals in the interstitial water area and particulate heavy metals in the sediment bed area. The steps include:

[0092] Step S51, using the analytical theory of dissolved heavy metals in interstitial water and particulate heavy metals in bottom sediments, a rapid calculation model for the concentration of dissolved heavy metals in interstitial water is established, and its expression is as follows:

[0093] ;

[0094] In the formula, Represents the point within the range of dredged material diffusion The gap water Dissolved heavy metal concentrations, Representative The solid content ratio of heavy metals in dredged materials is Represents the point within the range of dredged material diffusion The concentration of heavy metals in the mixed sediments is Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, is the porosity of the bottom sediment, Representative The equilibrium distribution coefficient of heavy metals at a specific temperature, It can represent various heavy metals such as lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), etc.

[0095] Step S52, using the analytical theory of dissolved heavy metals in interstitial water and particulate heavy metals in bottom sediments, a rapid calculation model for the concentration of particulate heavy metals in the interstitial water is established, and its expression is as follows:

[0096] ;

[0097] In the formula, Represents the point within the range of dredged material diffusion The bottom sediments at The concentration of heavy metals in particle form, Representative The solid content ratio of heavy metals in dredged materials is Represents the point within the range of dredged material diffusion The concentration of heavy metals in the mixed sediments is Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, is the porosity of the bottom sediment, Representative The equilibrium distribution coefficient of heavy metals at a specific temperature, It can represent various heavy metals such as lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), etc.

[0098] This example further verifies the above method with experimental data, and the calculation process is as follows:

[0099] Step S1, heavy metal solid content ratio pretreatment, through the dredged soil drying and digestion treatment, measuring the mass ratio of various heavy metals and the mass of the dredged soil sample, to obtain the solid content ratio of various heavy metals in the dredged soil.

[0100] The process of obtaining the solid content ratio of various heavy metals in dredged soil is as follows:

[0101] Step S11, collecting 1.5 kg of representative dredged soil samples from the dredged soil, ensuring that the sampling points are evenly covered and representative of the environment, removing debris from the dredged soil samples, and mixing them evenly;

[0102] Step S12, drying the dredged soil sample to a constant weight, grinding the dredged soil sample into uniform fine powder using a mortar, and weighing the dry mass of the dredged soil sample, which is 1.2 kg;

[0103] Step S13, according to the wet digestion method, weigh the dredged soil sample, add 12 kg of polytetrafluoroethylene, place it in a microwave digestion instrument and digest it according to the set program, and after completion, cool it to room temperature 25°C and adjust the volume, and the measured fixed volume is 0.1L;

[0104] Step S14, using inductively coupled plasma emission spectroscopy, according to the mass concentration of each heavy metal, calculate the solid content ratio of each heavy metal as follows:

[0105] The test results showed that the Pb (lead) content was 200 mg / kg, the Cd (cadmium) content was 5 mg / kg, the Cu (copper) content was 250 mg / kg, and the Zn (zinc) content was 100 mg / kg.

[0106] Step S2, obtaining the equilibrium distribution coefficient of heavy metals, by collecting the water temperature, screening the dredged soil by particle size, and calculating the equilibrium distribution coefficient of heavy metals in dissolved state and particle state at different particle size levels; the process of obtaining the equilibrium distribution coefficient of heavy metals includes:

[0107] The water temperature was 20 degrees Celsius. The temperature change has an exponential effect on the distribution coefficient, which can characterize the change of the distribution coefficient with the water temperature variable. At the same time, the distribution coefficient is related to the sediment particle size, especially the difference in the adsorption capacity of clay and sand for heavy metals. Therefore, the dredged soil is screened by using a sieve hole between 10 mesh and 30 mesh. The gradation composition of the dredged soil is shown in Table 1, and the particle size distribution curve is shown in Figure 5 .

[0108] Table 1: Dredged soil gradation composition table

[0109] The distribution coefficient calculation method covers different sediment particle sizes. The equilibrium distribution coefficients of various types of heavy metals in dissolved and particle states are calculated at different particle sizes. It can be calculated that, taking dredged soil with a particle size of 0.075 mm as an example, the equilibrium distribution coefficient of Pb (lead) is 750L / kg, the equilibrium distribution coefficient of Cd (cadmium) is 75L / kg, the equilibrium distribution coefficient of Cu (copper) is 750L / kg, and the equilibrium distribution coefficient of Zn (zinc) is 75L / kg.

[0110] Step S3, using the dredged soil bottom dumping diffusion model to calculate the sediment content and sediment thickness in the overlying water body during the dredged soil bottom dumping process. According to the analytical theory of dissolved heavy metals in the overlying water body, the heavy metal concentration distribution is quickly calculated, and a rapid acquisition model for the concentration of dissolved heavy metals and suspended particulate heavy metals in the overlying water body under equilibrium state is established to achieve rapid acquisition of the concentration of dissolved heavy metals and suspended particulate heavy metals in the overlying water body. Next, Pb (lead) is taken as the research object.

[0111] Step S31, the dredged soil bottom dump diffusion model calculation formula of the dredged soil bottom dump diffusion sand content and sediment thickness is as follows:

[0112] ;

[0113] ;

[0114] in, It is the calculated transitional sediment content after the diffusion process of dredged soil occurs and before the settlement process occurs. Points within the diffusion range of dredged materials The dredged soil mass is 20,000 tons. Points within the diffusion range of dredged materials The sediment content at the location, H is the water depth, the average value is 90m, K is the diffusion coefficient 10 -6 , and are the average lateral and longitudinal velocity, respectively, which is 0.3 m / s, η is the cloud following coefficient, is the sediment settling velocity, The calculation time step is taken as 60s. The calculated diffused sediment content at the mud dumping point is 40mg / L.

[0115] The calculation formula for obtaining the sediment thickness in the overlying water body during the dredged soil bottom dumping process using the dredged soil bottom dumping diffusion model is as follows:

[0116] ;

[0117] In the formula, Points within the diffusion range of dredged materials After the sedimentation, the bottom siltation increases the sediment thickness. is the porosity of the bottom sediment, which can be taken as 1. Represents the dry bulk density of sediment, which is 2650kg / m 3 . Calculation shows that the bottom sediment thickness is 1.7m.

[0118] Step S32, based on the analytical theory of dissolved and particulate heavy metals in the overlying water body under equilibrium state, a rapid acquisition model of the concentration of dissolved heavy metals in the overlying water body is established, and its expression is as follows:

[0119] ;

[0120] In the formula, represents lead (Pb), is the porosity in water, which can be directly taken as 1. The calculated results of the concentration of dissolved heavy metals in the overlying water vary with time as shown in Figure 3 .

[0121] The maximum concentration of Pb (lead) in the overlying water body in the mud dumping area is about 0.8 mg / L. The maximum concentration of Pb (lead) in the overlying water body 100m away from the mud dumping area is about 0.4 mg / L.

[0122] Step S33, based on the analytical theory of dissolved and particulate heavy metals in the overlying water body under equilibrium state, a rapid calculation model for the concentration of particulate heavy metals in the suspended matter of the overlying water body is established, and its expression is as follows:

[0123] ;

[0124] In the formula, Represents the point within the range of dredged material diffusion The suspended matter in The concentration of heavy metals in particle form, Representative The solid content ratio of heavy metals in dredged materials is Representative The equilibrium distribution coefficient of heavy metals at a specific temperature, represents lead (Pb), is the porosity in water and can be directly taken as 1.

[0125] According to the above formula, the particle concentration of Pb (lead) in the overlying water body in the mud dumping point area is 0.8 mg / L.

[0126] Step S4, the calculation method of the heavy metal-containing sediment concentration and the total sediment concentration after the bottom sediment is mixed is as follows:

[0127] Step S41, using the exchange relationship between new sediments and surface sediments, in the process of calculating the heavy metal concentration distribution in the bottom sediments and interstitial water bodies, the mixing process of new sediments and historical sediments is first considered, so as to calculate the concentration of heavy metal-containing sediment in the bottom sediments after mixing.

[0128] Step S42: After mixing, the particulate heavy metals in the bottom sediment and the dissolved heavy metals in the interstitial water are balanced. At this time, the total sediment concentration after mixing the bottom sediment is :

[0129] ;

[0130] In the formula, Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, is the porosity of sediment in the bottom bed. The total concentration of Pb (lead) mixed in the bottom bed in the mud dumping area is 0.15 mg / L.

[0131] Step S5, calculate the concentrations of dissolved and particulate heavy metals in interstitial water, establish a rapid calculation model for the concentrations of dissolved heavy metals in interstitial water and particulate heavy metals in the bottom bed, and realize rapid acquisition of the concentrations of dissolved heavy metals in the interstitial water area and particulate heavy metals in the sediment bed area.

[0132] Step S51, using the analytical theory of dissolved heavy metals in interstitial water and particulate heavy metals in bottom sediments, a rapid calculation model for the concentration of dissolved heavy metals in interstitial water is established, and its expression is as follows:

[0133] ;

[0134] Calculation shows that the dissolved concentration of Pb (lead) in the interstitial water in the mud dumping area is 82 mg / L.

[0135] Step S52, using the analytical theory of dissolved heavy metals in interstitial water and particulate heavy metals in bottom sediments, a rapid calculation model for the concentration of particulate heavy metals in interstitial water is established according to the following formula:

[0136] ;

[0137] The calculated results of the concentration of heavy metals in sediment particles in interstitial water vary with time. Figure 4 The final calculated concentration of Pb (lead) in the interstitial water in the mud dumping point area is 8.5 mg / L.

[0138] The present invention measures the ratio of the mass of multiple types of heavy metals such as lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn) and the like to the mass of the dredged soil samples by drying and digesting the dredged soil samples, and obtains the solid content ratio of each heavy metal in the bottom-thrown dredged soil; collects the water temperature, distinguishes the particle size groups of different particle size gradations of the dredged materials, and calculates the equilibrium distribution coefficients of the dissolved and particulate states of each type of heavy metal; calculates the sediment concentration in the overlying water body according to the bottom-thrown diffusion model of the dredged soil, establishes a rapid calculation model for the concentration of dissolved heavy metals in the overlying water body and the concentration of particulate heavy metals in the suspended sediment, and realizes rapid acquisition of the concentration of dissolved heavy metals in the overlying water body and the concentration of particulate heavy metals in the suspended sediment; establishes a rapid calculation model for the concentration of dissolved heavy metals in interstitial water and the concentration of particulate heavy metals in the bottom bed according to the sediment deposition thickness, mixing thickness and porosity, and realizes rapid acquisition of the concentration of dissolved heavy metals in interstitial water and the concentration of particulate heavy metals in the sediment in the sediment bed area. The present invention can realize the rapid calculation and evaluation of the concentration distribution of various types of heavy metal substances in the whole space of the water environment, such as the dissolved state in the overlying water, the dissolved state in the interstitial water, the suspended silt particle state, the bottom sediment particle state, etc. during the bottom dumping process of dredged soil, taking into account the environment of plankton and benthic organisms, and providing a practical tool to realize the environmental monitoring, management and treatment of toxic heavy metals in bottom dumping operations, which is suitable for wide application in actual operations.

[0139] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for quickly calculating the distribution of multiple types of heavy metals in the process of dredged soil bottom dumping, characterized in that: The following steps are involved: Step S1, by drying and digesting the dredged soil, measuring the ratio of the mass of various heavy metals to the mass of the dredged soil sample, and obtaining the solid content ratio of various heavy metals in the dredged soil; Step S2, collecting water temperature, performing particle size screening on the dredged soil, and calculating the equilibrium distribution coefficient of heavy metals in dissolved and particulate states at different particle size levels; Step S3, calculating the diffusion concentration of dredged soil and the thickness of sediment in the overlying water body according to the dredged soil bottom dumping diffusion model, and establishing a rapid calculation model for the concentration of dissolved heavy metals and the concentration of suspended particulate heavy metals in the overlying water body under equilibrium state; Step S4, according to the sediment thickness, mixed thickness, and dry bulk density in the sediment, taking into account the mixing process of new sediment and historical sediment, the heavy metal sediment concentration and the total sediment concentration after the bottom sediment is mixed are calculated; Step S5, establishing a rapid calculation model for the concentrations of dissolved heavy metals in interstitial water and particulate heavy metals in the bottom bed, so as to achieve rapid acquisition of the concentrations of dissolved heavy metals in the interstitial water area and particulate heavy metals in the sediment bed area.

2. The method for rapidly calculating the distribution of multiple types of heavy metals in the process of dredged soil bottom dumping according to claim 1 is characterized in that: In step S1, the process of obtaining the solid content ratio of various heavy metals in the dredged soil is as follows: Collect representative dredged soil samples from the dredged soil, ensure that the sampling points are evenly covered and representative of the environment, remove debris from the dredged soil samples, and mix them evenly; The dredged soil samples were dried to constant weight, and ground into uniform fine powder using a mortar and pestle, and the dry mass of the dredged soil samples was weighed; According to the wet digestion method, weigh the dredged soil sample, add the digestion reagent, place it in a microwave digestion instrument for digestion, cool and fix the volume after completion, and measure the fixed volume; The mass concentration of various heavy metals was determined by atomic emission spectrometry, and the solid content ratio of various heavy metals was obtained according to the following formula: : 。 3. The method for rapidly calculating the distribution of multiple types of heavy metals in the process of dredged soil bottom dumping according to claim 1 is characterized in that: In step S2, the process of obtaining the equilibrium distribution coefficient of heavy metals includes: The water temperature was collected, and the dredged soil was screened by particle size using a laser particle size analyzer. The equilibrium distribution coefficients of dissolved and particulate heavy metals of various types were calculated at different particle size levels: ； In the above formula, Representative The median particle size of heavy metals in dredged soil is In the group, when the temperature is T, the equilibrium distribution coefficient of heavy metal dissolved and particulate state; is the standard distribution coefficient, Factors that characterize the effect of temperature change on the equilibrium partition coefficient, represents the median particle size of the dredged soil component, Characterize the influence coefficient of different specific surface areas of different median particle size groups on the adsorption capacity of heavy metals.

4. The method for rapidly calculating the distribution of multiple types of heavy metals in the process of dredged soil bottom dumping according to claim 1 is characterized in that: In step S3, the dredged soil bottom dumping diffusion model is used to calculate the sediment content and sediment thickness in the overlying water body during the dredged soil bottom dumping process, and a rapid acquisition model for the concentration of dissolved heavy metals and the concentration of suspended particulate heavy metals in the overlying water body under equilibrium is established: Step S31, the dredged soil bottom dump diffusion model calculation formula of the dredged soil bottom dump diffusion sand content and sediment thickness is as follows: ； ; In the formula, It is the calculated transitional sediment content after the diffusion process of dredged soil occurs and before the settlement process occurs. Points within the diffusion range of dredged materials The quality of dredged soil Points within the diffusion range of dredged materials The sediment content at the point, H is the water depth, K is the diffusion coefficient, Indicates the location coordinates of the dredged material dumping point, and are the average lateral and longitudinal velocities respectively, η is the cloud following coefficient, is the sediment settling velocity, To calculate the time step; ； In the formula, Points within the diffusion range of dredged materials After the sedimentation, the bottom siltation increases the sediment thickness. is the porosity of the bottom sediment, represents the dry bulk density of sediment; Step S32, based on the analytical theory of dissolved and particulate heavy metals in the overlying water body under equilibrium state, a rapid acquisition model of the concentration of dissolved heavy metals in the overlying water body is established, and its expression is as follows: ； In the formula, Represents the point within the range of dredged material diffusion In the overlying water Dissolved heavy metal concentrations, Representative The solid content ratio of heavy metals in dredged materials is Representative The equilibrium distribution coefficient of heavy metals at a specific temperature, is the porosity in water; Step S33, based on the analytical theory of dissolved and particulate heavy metals in the overlying water body under equilibrium state, a rapid calculation model for the concentration of particulate heavy metals in the suspended matter of the overlying water body is established, and its expression is as follows: ； In the formula, Represents the point within the range of dredged material diffusion The suspended matter in The concentration of heavy metals in particle form, is the porosity in water.

5. The method for rapidly calculating the distribution of multiple types of heavy metals in the process of dredged soil bottom dumping according to claim 1 is characterized in that: In step S4, the calculation method of the heavy metal-containing sediment concentration and the total sediment concentration after mixing the bottom sediment is as follows: Step S41, using the exchange relationship between new sediments and surface sediments, in the process of calculating the heavy metal concentration distribution in the bottom sediments and interstitial water, the mixing process of new sediments and historical sediments is taken into account to calculate the concentration of heavy metal-containing sediment in the bottom sediments after mixing. : ； In the formula, Represents the point within the range of dredged material diffusion The concentration of heavy metals in the mixed sediments is Points within the diffusion range of dredged materials After the sedimentation, the bottom siltation increases the sediment thickness. Points within the diffusion range of dredged materials The cumulative thickness of sediments accumulated after sedimentation at the bottom increases. The thickness represents the mixing of historical sediments with new sediments under the action of dynamic and biological disturbance. represents the dry bulk density of sediment; Step S42: After mixing, the particulate heavy metals in the bottom sediment and the dissolved heavy metals in the interstitial water are balanced. At this time, the total sediment concentration after mixing the bottom sediment is : ； In the formula, Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, The porosity of the bottom sediment.

6. The method for rapidly calculating the distribution of multiple types of heavy metals in the process of dredged soil bottom dumping according to claim 1 is characterized in that: In step S5, by establishing a rapid calculation model for the concentration of dissolved heavy metals in interstitial water and particulate heavy metals in the bottom bed, the concentration of dissolved heavy metals in the interstitial water area and particulate heavy metals in the sediment bed area can be rapidly obtained, including: Step S51, using the analytical theory of dissolved heavy metals in interstitial water and particulate heavy metals in bottom sediments, a rapid calculation model for the concentration of dissolved heavy metals in interstitial water is established, and its expression is as follows: ； In the formula, Represents the point within the range of dredged material diffusion The gap water Dissolved heavy metal concentrations, Representative The solid content ratio of heavy metals in dredged materials is Represents the point within the range of dredged material diffusion The concentration of heavy metals in the mixed sediments is Represents the point within the range of dredged material diffusion The total sediment concentration of the mixed sediment after mixing, is the porosity of the bottom sediment, Representative Equilibrium partition coefficients of heavy metals at specific temperatures; Step S52, using the analytical theory of dissolved heavy metals in interstitial water and particulate heavy metals in bottom sediments, a rapid calculation model for the concentration of particulate heavy metals in the interstitial water is established, and its expression is as follows: ； In the formula, Represents the point within the range of dredged material diffusion The bottom sediments at Heavy metal concentrations in particle form.

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