Method for rapid construction and evaluation of remaining sediment ecosystem after river and lake dredging

Abstract

This invention discloses a rapid construction and evaluation method for the ecosystem of residual sediment after lake dredging. First, biochar is added to the residual sediment after dredging, followed by planting submerged plants and introducing benthic animals. Regular sampling is conducted to monitor the growth of submerged plants and benthic animals, as well as water quality parameters of the overlying water and sediment parameters. The functional coefficient of the constructed sediment ecosystem is determined, and the restoration status of the ecosystem is evaluated. This invention utilizes submerged plants, benthic animals, and biochar to rapidly construct a sediment ecosystem. The reliability of the constructed ecosystem is determined by quantifying the impacts of five aspects: sediment pollutant reduction, diffusion of sediment pollutants to the overlying water, sediment microbial diversity, and the growth of benthic animals and submerged plants. Results show that this invention achieves rapid construction of sediment ecosystems after river and lake dredging, effectively reduces sediment pollutants, significantly slows the diffusion of sediment pollutants to the overlying water, and improves the diversity of sediment microbial communities.

Description

Technical Field

[0001] This invention relates to the field of river and lake dredging, and in particular to a method for the rapid construction and evaluation of the ecosystem of the remaining bottom sediment after river and lake dredging. Background Technology

[0002] Bottom sediment is a crucial component of river and lake ecosystems. Nitrogen, phosphorus, heavy metals, and organic pollutants repeatedly migrate between the bottom sediment and the overlying water. The release of pollutants from the bottom sediment into the overlying water through endogenous sources is a significant cause of water quality deterioration and recurring black and odorous conditions. Even after external pollution sources in rivers are controlled, bottom sediment pollution in black and odorous water bodies becomes a limiting factor for river and lake water quality. Dredging river and lake bottom sediment is the most direct means of addressing endogenous water pollution. Traditional dredging involves completely removing all bottom sediment. While this method effectively removes all pollutants, it also causes devastating damage to benthic habitats and benthic animals, hindering ecosystem recovery and disrupting the complete food chain. Conversely, dredging too shallowly only removes surface pollutants, exposing bottom pollutants at the sediment-water interface, leading to secondary pollution and further hindering ecosystem recovery. Therefore, some studies suggest dredging river and lake sediment to a certain depth before ecological restoration. However, how to quickly construct a bottom sediment ecosystem remains a challenge for the industry. Summary of the Invention

[0003] In view of this, the present invention proposes a method for the rapid construction and evaluation of the ecosystem of the remaining bottom sediment after river and lake dredging, thereby realizing the rapid construction of the ecosystem of the remaining bottom sediment.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The method for rapid construction and evaluation of the ecosystem of residual bottom sediment after river and lake dredging, as described in this invention, includes...

[0006] S1, Ecosystem Construction

[0007] S11, Add a certain amount of biochar to the remaining bottom sediment after dredging; wherein the amount of biochar added is 3% to 5% of the dry weight of the remaining bottom sediment;

[0008] S12, plant submerged plants in the remaining bottom sediment; wherein, the submerged plants include any one or any combination of two or more of the following: dwarf Vallisneria, evergreen Vallisneria, spike-like Myriophyllum spicatum and Malayan Potamogeton.

[0009] S13. After the submerged plants are planted, add benthic animals to the bottom mud; among them, benthic animals include any one or any combination of two or more of the following: cilia, mussels, and freshwater shrimp.

[0010] S2, Ecosystem Assessment

[0011] S21. Regularly sample and test the growth of submerged plants and benthic animals, and regularly sample and test the water quality parameters of the overlying water body and the sediment parameters. The water quality parameters of the overlying water body include COD, total nitrogen, total phosphorus and ammonia nitrogen concentrations, and the sediment parameters include sediment organic matter, sediment total nitrogen, sediment total phosphorus and sediment ammonia nitrogen concentrations.

[0012] S22, Based on the parameters obtained in S21, determine the functional coefficient of the sediment ecosystem constructed in S1. F ;

[0013] S23, based on the functionality coefficient F Confirm the result.

[0014] The beneficial effects are as follows: This invention utilizes submerged plants, benthic animals, and biochar to rapidly construct a sediment ecosystem. The reliability of the constructed ecosystem is determined by quantifying the impacts on five aspects: sediment pollutant reduction, sediment pollutant diffusion to overlying water bodies, sediment microbial diversity, and the growth of benthic animals and submerged plants. The results demonstrate that this invention can achieve the rapid construction of sediment ecosystems after river and lake dredging, effectively reducing sediment pollutants, significantly slowing the diffusion of sediment pollutants to overlying water bodies, and improving sediment microbial community diversity, thus providing strong support for ensuring the functionality of river and lake aquatic ecosystems.

[0015] The present invention adds biochar to the remaining sediment, which not only helps to enhance the removal effect of sediment pollutants by the submerged plant coupled benthic animal system, but also inhibits the diffusion of pollutants in the sediment to the overlying water.

[0016] Preferably, step S1 further includes: placing multiple aeration heads at intervals 15-30 cm above the sediment before adding benthic animals, and performing aeration after adding the benthic animals. The aeration rate is related to the water temperature; when the water temperature is ≥15℃, the aeration rate is 6 L / min; when the water temperature is <15℃, the aeration rate is 4 L / min. This invention enhances the removal effect of submerged plant-coupled benthic animal system on sediment pollutants by combining biochar and aeration, and can also inhibit the diffusion of pollutants from the sediment to the overlying water.

[0017] In S12, the dwarf Vallisneria natans has a plant height ≥10cm and a planting area of ​​240 plants / m². 2 The evergreen spiny grass should be at least 15cm tall and have a planting area of ​​80 plants / m². 2 The plant height of *Myriophyllum spicatum* should be ≥25cm, and the planting area should be 120 plants / m². 2 The plant height of Potamogeton malaianus should be ≥25cm, and the planting area should be 120 plants / m². 2 ;

[0018] In S13, the weight of a single *Bellamya alopecuroides* is ≥5g, and the dosage density is 50g / m³.2 The weight of a single toothless mussel is ≥50g, and the feeding density is 80g / m³. 2 Individual shrimp weight ≥1g, addition density 5g / m³ 2 .

[0019] In step S11, when the sediment temperature is ≤15℃, the amount of biochar added is 3% of the remaining dry weight of the sediment; when the sediment temperature is >15℃, the amount of biochar added is 5% of the remaining dry weight of the sediment. The preferred biochar is corn stalk biochar, which is ground to an 80-mesh sieve before being added to the sediment. The biochar of this invention is granular, ensuring sufficient contact with the sediment and further guaranteeing the removal effect of pollutants in the sediment.

[0020] In S21, after 10 days of construction, the survival rate of submerged plants, root length and plant height, survival rate and weight gain of benthic animals, parameters of the overlying water, parameters of the sediment, and sediment microorganisms are monitored every two days. The water quality parameters of the overlying water include COD, total nitrogen, total phosphorus and ammonia nitrogen concentrations, and the sediment parameters include sediment organic matter, sediment total nitrogen, sediment total phosphorus and sediment ammonia nitrogen concentrations.

[0021] In S22, the functionality coefficient F The calculation process is as follows: ;

[0022] in, f 1 =a 1 × (1+b 1 ) × 0.15 In the formula a 1 Survival rate of benthic animals, % b 1 The average individual weight gain of benthic animals, %

[0023] f 2 =a 2 × ( 1+b 2 ×0.4＋c 2 × 0.6) ×0.15 In the formula a 2 Survival rate of submerged plants, % b 2 The average increase in root length for submerged plants, % c 2 The average increase in plant height for submerged plants, %

[0024] f 3 = ( a 3 ×0.8＋b 3 ×0.2 ) ×0.10 In the formula a 3 To represent the changes in microbial diversity in sediment, a significant increase is represented by 1, no significant increase by 0, and a significant decrease by -1. b 3 The changes in the dominant microbial species in the sediment are shown. If a dominant microbial species appears, it is 1; if no dominant microbial species appears, it is -1.

[0025] f 4 = ( a 4 ×0.30＋b 4 ×0.30＋c 4 ×0.30＋d 4 ×0.10 ) ×0.30 In the formula, a 4 The change in the organic matter content of the sediment is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. b 4 For changes in total nitrogen content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1. c 4 For changes in total phosphorus content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1. d 4 For changes in ammonia nitrogen content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1.

[0026] f 5 = ( a 5 ×0.30＋b 5 ×0.30＋c 5 ×0.2＋d 5 ×0.2 ) ×0.30 In the formula, a 5 The change in COD concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. b 5The change in total nitrogen concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. c 5 The change in total phosphorus concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. d 5 The value represents the change in ammonia nitrogen concentration in the overlying water body. A significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1.

[0027] The beneficial effects are: This invention quantifies the impact of five aspects—reduction of sediment pollutants, diffusion of sediment pollutants to overlying water, sediment microbial diversity, and growth of benthic animals and submerged plants—to determine the functional coefficient of the sediment ecosystem, thereby determining the ecological restoration status of the sediment.

[0028] Compared with existing technologies, this invention enables the rapid construction of sediment ecosystems after river and lake dredging, effectively reduces sediment pollutants, significantly slows the diffusion of sediment pollutants to overlying water bodies, and improves the diversity of sediment microbial communities, providing strong support for ensuring the functionality of river and lake aquatic ecosystems. Furthermore, this invention enables the rapid restoration of river and lake sediment ecosystems, with low restoration costs and simple construction, making it of significant promotional value. Detailed Implementation

[0029] It should be noted that the water temperature in this invention refers to the water temperature at a depth of 0.3m above the bottom sediment; the dry weight of the bottom sediment in this invention is the total dry weight of the remaining bottom sediment, which is calculated from the natural volume and density of the bottom sediment, and the total dry weight of the remaining bottom sediment is determined from the total wet weight and moisture content of the remaining bottom sediment.

[0030] The rapid construction and evaluation method for the residual sediment ecosystem after river and lake dredging, as described in this invention, includes:

[0031] S1, Rapid Construction of Ecosystems

[0032] S11, Add a certain amount of biochar to the remaining bottom sediment after dredging; wherein the amount of biochar added is 3% to 5% of the dry weight of the remaining bottom sediment; wherein, when the water temperature is ≤15℃, the amount of biochar added is 3% of the dry weight of the remaining bottom sediment; when the water temperature is >15℃, the amount of biochar added is 5% of the dry weight of the remaining bottom sediment.

[0033] S12, plant submerged plants in the remaining bottom sediment. Submerged plants include dwarf Vallisneria natans, evergreen Vallisneria natans, spike-like myriophyllum, and Malayan pondweed (of course, one or any combination of two or more can also be planted); of course, seeds of submerged plants can also be sown in the remaining bottom sediment during actual construction.

[0034] Among these requirements, the seedlings of dwarf Vallisneria natans, evergreen Vallisneria natans, spike-shaped Myriophyllum spicatum, and Potamogeton malaianus should all have complete root systems, be free from diseases and pests, have an impurity content of less than 5%, and be intact without mechanical damage; the plant height of dwarf Vallisneria natans should be ≥10cm, and the planting area should be 240 plants / m². 2 The evergreen spiny grass should be at least 15cm tall and planted at a density of 80 plants per square meter. 2 The plant height of *Myriophyllum spicatum* should be ≥25cm, and the planting area should be 120 plants / m². 2 Potamogeton mongolicum should be at least 25cm tall and have a planting area of ​​120 plants / m². 2 ;

[0035] S12, place the aeration head of the river / lake aeration equipment 15-30cm above the bottom sediment; add benthic animals to the bottom sediment, including *Bambusa multiplex*, *Ceratophyllum demersum*, and freshwater shrimp (or any one or two of these); the survival rate of *Bambusa multiplex*, *Ceratophyllum demersum*, and freshwater shrimp seedlings should be ≥95%, the seedlings should be robust and free from diseases and pests, and the seedlings should be disinfected before release; the weight of a single *Bambusa multiplex* should be ≥5g, and the release density should be 50g / m³. 2 The weight of a single toothless mussel is ≥50g, and the feeding density is 80g / m³. 2 Individual shrimp weight ≥1g, addition density 5g / m³ 2 ;

[0036] After the benthic animals are added, the river and lake aeration equipment is activated to aerate the bottom sediment. The aeration rate is flexibly determined according to the sediment temperature. Specifically, when the water temperature is ≥15℃, the aeration rate is 6L / min; when the water temperature is <15℃, the aeration rate is 4L / min. Aeration increases the oxygen content in the bottom sediment and the overlying water, further promoting the decomposition of pollutants in the sediment and the growth of submerged plants and benthic animals, thereby reducing pollutants and purifying the water.

[0037] In the above steps, the aerator can also be placed on top of the bottom sediment after the benthic animals are added.

[0038] S2, Evaluation of Residual Sediment Ecosystems in Rivers and Lakes

[0039] S21. After the construction is completed, samples are taken to test the water quality parameters of the overlying water body, the sediment parameters, and the microorganisms in the sediment. The sediment parameters include sediment organic matter, sediment total nitrogen, sediment total phosphorus, and sediment ammonia nitrogen concentration; the water quality parameters of the overlying water body include COD, total nitrogen, total phosphorus, and ammonia nitrogen concentration.

[0040] Ten days after construction, samples were taken every two days (e.g., on days 11, 13, 15 and 17) to test the survival rate, average plant height and root length of submerged plants, the survival rate and individual weight of benthic animals, and the water quality parameters, sediment parameters and sediment microorganisms of the overlying water body.

[0041] S22, Based on the parameters obtained in S21, determine the functional coefficient of the sediment ecosystem. F The calculation formula is as follows: ;in f i The calculation formulas are as follows:

[0042] in, f 1 =a 1 × (1 + b 1 ) × 0.15 In the formula a 1 The average survival rate of the three benthic animals, % b 1 The average individual weight increment for the three benthic animals is expressed as %; in the calculation, the average individual weight increment is based on the average individual weight of the seedlings. m 1 and the average individual weight on the day of sampling m 2 Calculated;

[0043] f 2 =a 2 × ( 1 + b 2 ×0.4 + c 2 × 0.6) ×0.15 In the formula a 2 The average survival rate of the four submerged plants, % b 2 The average root length increment of the four submerged plants, % c 2 The average increase in plant height for the four submerged plants is %; in the calculation, the parameters for each plant are calculated based on the average data of the seedlings and the sampling day, and finally the survival rate, root length increase and plant height increase of the four submerged plants are averaged respectively.

[0044] f 3 = ( a 3 × 0.8 + b 3 × 0.2 )×0.10 In the formula a 3 To represent the changes in microbial diversity in sediment, a significant increase is represented by 1, no significant increase by 0, and a significant decrease by -1. b 3 The changes in the dominant microbial species in the sediment are shown. If a dominant microbial species appears, it is 1; if no dominant microbial species appears, it is -1.

[0045] f 4 = ( a 4 × 0.30 + b 4 ×0.30 + c 4 ×0.30 + d 4 × 0.10 ) ×0.30 In the formula, a 4 The change in the organic matter content of the sediment is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. b 4 For changes in total nitrogen content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1. c 4 For changes in total phosphorus content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1. d 4 For changes in ammonia nitrogen content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1.

[0046] f 5 = ( a 5 ×0.30 + b 5 ×0.30 + c 5 ×0.2 + d 5 ×0.2 ) ×0.30 In the formula, a 5 The change in COD concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. b 5 The change in total nitrogen concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase.c 5 The change in total phosphorus concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. d 5 The change in ammonia nitrogen concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase.

[0047] The above f 1 and f 2 The parameters are calculated from the data on the day of sampling and the initial data of the seedlings; f 3 , f 4 and f 5 The significance of the changes in each parameter was calculated using data from sampling days before and after ecosystem construction. f 3 , f 4 and f 5 The significance level for each parameter was 0.05.

[0048] S23, based on the functionality coefficient F When evaluating the restoration of sediment ecosystems, F A value ≥0.70 indicates that the sediment ecosystem has been restored after dredging; if... F A value less than 0.7 indicates that the sediment ecosystem has not been restored.

[0049] In actual sampling, the sampling of submerged plants, benthic animals, overlying water, and bottom sediment includes the following:

[0050] Meridian sampling lines were drawn at 200m intervals along the meridian direction and parallel sampling lines were drawn at 200m intervals along the parallel direction. The intersection of the meridian and parallel sampling lines was the sampling point. Sampling points were preferentially set at the lake's sewage outlet and the water connection point. The bottom sediment sampling depth was 20cm down from the mud-water interface. The sampling situation of the overlying water body at each sampling point is shown in Table 1.

[0051] Table 1 Sampling points for rivers, lakes and reservoirs

[0052]

[0053] The sampling area for submerged plants and benthic animals is a 1m radius area centered on the sampling point. The survival rate of each type of submerged plant and benthic animal is collected and statistically analyzed. At least 3 plants of each type of submerged plant should be collected within the sampling area to determine the average plant height and average root length. At least 3 animals of each type of benthic animal should be collected within the sampling area to determine the average individual weight of each animal.

[0054] Using the method of this invention, the organic matter, TN, and NH4 in the remaining sediment after 15 days of construction were analyzed. + -N, NO3 - -N, NO2 - The removal rates of -N and TP were 35.2%, 41.8%, 76.3%, 80.5%, 98.2%, and 22.7%, respectively; the removal rates of COD, TN, TP, and NH4+ diffused from the sediment to the overlying water were also reduced. + -N, NO3 - -N, NO2 - The inhibition rates of -N were 56.5%, 37.9%, 91.5%, 45.2%, 80.1%, and 33.2%, respectively, indicating good pollutant removal effect and preventing diffusion to the overlying water body. In addition, this invention significantly improved the abundance and diversity of the microbial community in the remaining sediment, with the survival rate of submerged plants and benthic animals both greater than 95%, the average individual weight increase of benthic animals greater than 5%, the average root length increase of submerged plants greater than 10%, and the average plant height increase of submerged plants greater than 12%. The ecosystem functionality coefficient of the remaining sediment was 0.85 after 15 days.

[0055] Dredging is a direct means of removing pollutants accumulated in water bodies, but it inevitably disturbs or even destroys the integrity and functionality of the original sediment ecosystem. This invention, through planting submerged plants, introducing benthic animals, adding biochar as a sediment conditioner, and supplementing with aeration, achieves rapid reconstruction of the remaining sediment ecosystem after dredging. Ecological restoration of the remaining sediment can be achieved in approximately 15 days. It also effectively removes pollutants from the remaining sediment, prevents the diffusion of pollutants to the overlying water, and enriches the sediment microorganisms.

[0056] Finally, it should be emphasized that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for rapidly constructing and evaluating the ecosystem of residual bottom sediment after river and lake dredging, characterized in that: The rapid construction and evaluation method includes the following steps: S1, Ecosystem Construction S11, Add a certain amount of biochar to the remaining bottom sediment after dredging; wherein the amount of biochar added is 3% to 5% of the dry weight of the remaining bottom sediment; S12, plant submerged plants in the remaining bottom sediment; wherein, the submerged plants include any one or any combination of two or more of the following: dwarf Vallisneria, evergreen Vallisneria, spike-like Myriophyllum spicatum and Malayan Potamogeton. S13. After the submerged plants are planted, add benthic animals to the bottom mud; among them, benthic animals include any one or any combination of two or more of the following: cilia, mussels, and freshwater shrimp. S2, Ecosystem Assessment S21, regularly sample and test the growth of submerged plants and benthic animals, and regularly sample and test the water quality parameters, sediment parameters and microorganisms in the overlying water body; S22, Based on the parameters obtained in S21, determine the functional coefficient of the sediment ecosystem constructed in S1. F ; S23, based on the functionality coefficient F Determine the result; S1 further includes: placing multiple aeration heads at intervals 15-30cm above the bottom sediment before adding benthic animals, and performing aeration after adding benthic animals; In S11, when the water temperature is ≤15℃, the amount of biochar added is 3% of the dry weight of the remaining sediment; when the water temperature is >15℃, the amount of biochar added is 5% of the dry weight of the remaining sediment. In S21, after 10 days of construction, the survival rate of submerged plants, root length and plant height, survival rate and weight gain of benthic animals, overlying water parameters, sediment parameters, and sediment microorganisms are monitored every two days. The water quality parameters of the overlying water include COD, total nitrogen, total phosphorus, and ammonia nitrogen concentrations, and the sediment parameters include sediment organic matter, sediment total nitrogen, sediment total phosphorus, and sediment ammonia nitrogen concentrations. In S22, the functionality coefficient F The calculation process is as follows: ； in, f 1 = a 1 × (1+b 1 ) × 0.15 In the formula a 1 Survival rate of benthic animals, % b 1 The average individual weight gain of benthic animals, % f 2 =a 2 ×(1 + b 2 ×0.4＋c 2 ×0.6)×0.15 In the formula a 2 Survival rate of submerged plants, % b 2 The average increase in root length for submerged plants, % c 2 The average increase in plant height for submerged plants, % f 3 =(a 3 ×0.8 + b 3 ×0.2)×0.10 In the formula a 3 To represent the changes in microbial diversity in sediment, a significant increase is represented by 1, no significant increase by 0, and a significant decrease by -1. b 3 The changes in the dominant microbial species in the sediment are shown. If a dominant microbial species appears, it is 1; if no dominant microbial species appears, it is -1. f 4 =(a 4 ×0.30 + b 4 ×0.30 + c 4 ×0.30 + d 4 ×0.10)×0.30 In the formula, a 4 The change in the organic matter content of the sediment is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. b 4 For changes in total nitrogen content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1. c 4 For changes in total phosphorus content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1. d 4 For changes in ammonia nitrogen content in sediment, a significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1. f 5 =(a 5 ×0.30 + b 5 ×0.30 + c 5 ×0.2 + d 5 ×0.2)×0.30 In the formula, a 5 The change in COD concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. b 5 The change in total nitrogen concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. c 5 The change in total phosphorus concentration in the overlying water body is represented by 1 for a significant decrease, 0 for a non-significant decrease, and -1 for a significant increase. d 5 The value represents the change in ammonia nitrogen concentration in the overlying water body. A significant decrease is represented by 1, a non-significant decrease by 0, and a significant increase by -1.

2. The method for rapid construction and evaluation of the ecosystem of residual bottom sediment after river and lake dredging according to claim 1, characterized in that: In S12, the dwarf Vallisneria natans has a plant height ≥10cm and a planting area of ​​240 plants / m². 2 The evergreen spiny iris should be at least 15cm tall and planted at a density of 80 plants per square meter. 2 The plant height of *Myriophyllum spicatum* should be ≥25cm, and the planting area should be 120 plants / m². 2 Potamogeton mongolicum should be at least 25cm tall and have a planting area of ​​120 plants / m². 2 ; In S13, the weight of a single *Bellamya alopecuroides* is ≥5g, and the dosage density is 50g / m³. 2 The weight of a single toothless mussel is ≥50g, and the feeding density is 80g / m³. 2 Individual shrimp weight ≥1g, addition density 5g / m³ 2 .

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