An experimental device for simulating the migration and transformation of nutrients in coastal reservoirs and its implementation method

Abstract

The present invention discloses an experimental device for simulating the migration and transformation of nutrients in a coastal reservoir and an implementation method thereof, comprising a simulated water tank divided from left to right into a groundwater recharge area, a coastal reservoir simulation area and a seawater area, a terrestrial recharge system connected to the groundwater recharge area, a tidal generation system connected to the seawater area, a dam simulation system located at the boundary between the coastal reservoir simulation area and the seawater area and used to adjust the dam parameters to simulate the coastal reservoir environment, a nutrient simulation system for simulating pollutants entering the coastal reservoir and adjacent aquifers from the surface underground, a vertical full-section sampling device for collecting soil and water bodies in the vertical full-section of the surface and underground of the coastal reservoir, a nutrient monitoring system for monitoring the real-time changes in the nutrient concentration of point source pollutants entering the coastal reservoir and adjacent aquifers from the surface underground, and a camera system for photographing the migration and transformation process of nutrients. The present invention can intuitively simulate and characterize the migration and transformation process of nutrients on the surface and underground of a coastal reservoir.

Description

Technical Field

[0001] The invention relates to the technical field of coastal zone solute transport simulation devices, and in particular to an experimental device and an experimental method for simulating the migration and transformation of nutrients in a coastal reservoir. Background Art

[0002] Coastal reservoirs refer to comprehensive water conservancy projects built at estuaries or coasts in coastal areas to store fresh water. Most of their water sources are fresh water from rivers entering the sea, and they are one of the effective ways to alleviate water shortages in coastal areas. Coastal reservoirs have achieved good economic and social benefits after construction and use, but the excessive concentration of nutrients during operation has seriously limited the water supply function of the reservoirs. Some existing reservoirs have serious excesses of total nitrogen and ammonia nitrogen after operation, exceeding 40 times the limit of Class II water quality standards. Not only can they not meet the demand for water for production and life, but they have also caused the deterioration of the local water ecological environment. Revealing the migration and transformation process of nutrients in coastal reservoirs and adjacent aquifers is not only one of the keys to scientifically solving the eutrophication of water bodies, but also can provide strong theoretical support for the control of surface and underground pollutants in coastal zones.

[0003] Regarding the study of the mechanism of nutrient migration and transformation in coastal reservoirs and adjacent aquifers, commonly used research methods include field monitoring and numerical simulation. Field observation is mainly carried out by setting up monitoring points in coastal reservoirs and side banks, sampling at fixed time intervals and hydrochemical analysis, comparing the nutrient storage forms and concentration distribution at different depths in coastal reservoirs and adjacent aquifers, and determining the temporal and spatial distribution of nutrients. Numerical simulation is to generalize the hydrogeological conditions of coastal reservoirs and adjacent aquifers, use variable density and variable saturation characteristic numerical simulation software, construct numerical models and analyze the migration path of nutrients. However, field observation requires a lot of manpower and material resources, and it is impossible to achieve long-term continuous monitoring, so it is difficult to characterize the migration and transformation laws of coastal reservoirs and adjacent aquifers; and numerical simulation is affected by hydrogeological generalization, boundary conditions, grid discretization methods and iterative algorithms, and can only provide approximate numerical solutions for nutrients.

[0004] Indoor experiments are used to invert the migration process of pollutants in coastal reservoirs, which is also an important means to study the migration and transformation of pollutants in coastal reservoirs and adjacent aquifers. However, the current indoor experimental equipment mainly focuses on the qualitative or quantitative research of the seawater intrusion process in coastal reservoirs. There is a lack of simulation and monitoring equipment for the reaction and migration of nutrients. It is difficult to directly observe the occurrence form, concentration, and spatiotemporal distribution of nitrification and denitrification reaction rates of nutrients, and it is impossible to conduct experiments on the migration and transformation of nutrients in coastal reservoirs.

[0005] Therefore, it is urgent to solve the above problems. Summary of the invention

[0006] Purpose of the invention: The first purpose of the present invention is to provide an experimental device for simulating the migration and transformation of nutrients in coastal reservoirs, which can not only qualitatively observe the spatiotemporal distribution characteristics of nutrient content under complex dynamic conditions, but also can quantitatively measure the storage form, concentration, nitrification reaction and denitrification reaction rate of nutrients at different elevations in vertical sections by sampling surface-groundwater in key vertical sections of coastal reservoirs without destroying the storage form and reaction process of nutrients in the sampling section, establish a response relationship between coastal reservoirs, hydrodynamic conditions and nutrient migration and transformation, and provide scientific guidance for the control of nutrient content of water quality in coastal reservoirs and adjacent aquifers.

[0007] The second object of the present invention is to provide an experimental method for an experimental device simulating the migration and transformation of nutrients in coastal reservoirs.

[0008] Technical solution: To achieve the above objectives, the present invention discloses an experimental device for simulating the migration and transformation of nutrients in coastal reservoirs, comprising a simulated water tank divided from left to right into a groundwater recharge area, a coastal reservoir simulation area and a seawater area, a terrestrial recharge system connected to the groundwater recharge area, a tidal generation system connected to the seawater area, a dam simulation system located at the boundary between the coastal reservoir simulation area and the seawater area and used to regulate dam parameters to simulate the coastal reservoir environment, a nutrient simulation system for simulating point source pollutants entering the coastal reservoir and adjacent aquifers from the surface and underground, a vertical full-section sampling device for collecting vertical full-section soil and water bodies from the surface and underground of the coastal reservoir, a nutrient monitoring system for monitoring real-time changes in nutrient concentrations of point source pollutants entering the coastal reservoir and adjacent aquifers from the surface and underground, and a camera system for photographing the migration and transformation process of nutrients.

[0009] Among them, the coastal reservoir simulation area is filled with white quartz sand, the height of the white quartz sand is higher than the liquid level of the groundwater recharge area and the seawater area. The coastal reservoir simulation area is used to simulate the coastal reservoir and the adjacent coastal aquifer. The groundwater recharge area simulates the inland groundwater boundary, and the seawater area simulates the ocean boundary with variable head. A permeable partition is set at the boundary between the groundwater recharge area and the coastal reservoir simulation area.

[0010] Preferably, the land-source recharge system comprises a land-source recharge water tank connected to the bottom of the groundwater recharge area through a first peristaltic pump, and the land-source recharge water tank is filled with a first liquid simulating inland groundwater.

[0011] Furthermore, the tidal generating system includes a tidal wave generator connected to the bottom of the seawater area and a seawater tank connected to the tidal wave generator through a submersible pump. The seawater tank is filled with a second liquid that simulates seawater and is dyed with a first dye. The submersible pump pumps the second liquid from the seawater tank into the tidal wave generator. The periodically changing water level signal generated by the tidal wave generator enters the seawater area, forming an ocean boundary with tidal fluctuation conditions.

[0012] Furthermore, the dam simulation system includes a water-permeable sliding groove located at the boundary between the coastal reservoir simulation area and the seawater area, and an impermeable partition located in the sliding groove and movable up and down along the sliding groove.

[0013] Preferably, the nutrient simulation system includes a standard solution tank filled with a third liquid that simulates point source pollutants and is dyed with a second dye, a plurality of nutrient input devices arranged in a vertical array near the right side of the groundwater recharge area and in a horizontal array near the left side of the seawater area and at the top of the simulated water tank, a second peristaltic pump connected to the vertically arranged nutrient input devices and the standard solution tank through a hose, and a third peristaltic pump connected to the horizontally arranged nutrient input devices and the standard solution tank through a hose.

[0014] Furthermore, the vertical full-section sampling device includes a working platform, a multi-section telescopic motor vertically arranged on the working platform and capable of being extended and retracted up and down, a connecting plate connected to the ends of the multi-section telescopic motor and horizontally arranged above the simulated water tank, and a plurality of samplers arranged at intervals on the connecting plate and capable of being vertically inserted into the simulated water tank, wherein at least 4 samplers are arranged in the coastal reservoir and side bank areas of the simulated water tank, and at least 2 samplers are arranged in the inland area of ​​the simulated water tank; the sampler includes a hollow tube, a stainless steel patch hinged at the lower port of the hollow tube by a folding hinge, a first iron ring fixed on the outer wall of the top of the hollow tube, a second iron ring fixed on the inner side of the stainless steel patch, a steel wire rope with one end fixed on the second iron ring and passing through the first iron ring, and a transfer block connected to the other end of the steel wire rope, the upper surface of the connecting plate is provided with an interface groove for placing the transfer block and a closing plate adapted to the interface groove for fixing the transfer block in the interface groove.

[0015] Preferably, the nutrient monitoring system includes sampling holes distributed on the back of the simulated water tank, multiple columns of nitrogen, phosphorus and potassium sensors are arranged in the simulated water tank and away from the position of the vertical full-section sampling device, a nutrient data processor connected to the nitrogen, phosphorus and potassium sensors, and a display, wherein at least 4 columns of nitrogen, phosphorus and potassium sensors are used to monitor nitrogen, phosphorus and potassium data around, at the bottom and on the side banks of coastal reservoir dams, and at least 1 column of nitrogen, phosphorus and potassium sensors monitors nitrogen, phosphorus and potassium data of inland groundwater and point source nutrient solution near the inland boundary.

[0016] Furthermore, the camera system includes a camera located in front of the simulated water tank, a desktop computer connected to the camera, a light-shielding curtain surrounding the camera and the simulated water tank, and a lighting panel located directly above the simulated water tank.

[0017] The present invention provides an experimental method for an experimental device for simulating the migration and transformation of nutrients in a coastal reservoir, comprising the following steps:

[0018] (1) white quartz sand and nutrient salt solution were prepared for the experiment. After screening the white quartz sand, the nutrient salt solution was washed with deionized water for multiple times. After washing, the white quartz sand was placed in a bucket in a saturated water manner for standby use. The inland recharged groundwater was mixed with deionized water and potassium nitrate standard solution, and the nitrate nitrogen concentration of the land-based recharged groundwater was set according to different working conditions. The seawater was prepared by mixing deionized water, industrial salt, ammonium chloride standard solution and the first dye, and the ammonia nitrogen concentration and salinity of the seawater were set according to different working conditions to distinguish inland groundwater and simulate the influence of different sea-based ammonia nitrogen on the migration and transformation of nutrient salts in coastal reservoirs. The pollutants in the standard solution tank were prepared with deionized water, potassium nitrate, ammonium chloride and the second dye to distinguish inland groundwater from sea-based nitrogen.

[0019] (2) Regulating the coastal reservoir environment, by adjusting the relative position of the impermeable baffle in the sliding groove, adjusting the size of the coastal reservoir dam and the anti-seepage wall; controlling the average sea level, tidal amplitude and period of the tidal wave generator to influence the tidal signal of the coastal reservoir; turning on the first peristaltic pump, placing the hose into the land-based supply water tank, waiting for all the bubbles in the hose to be eliminated, and adjusting the input of underground fresh water by adjusting the first peristaltic pump;

[0020] (3) Arrange the white quartz sand and nutrient salt input device for the experiment. After placing a certain height of deionized water in the simulated water tank, use a funnel to evenly fill the cleaned white quartz sand for the experiment at the bottom of the simulated water tank. During the filling process, the deionized water level is controlled to be higher than a certain height of the white quartz sand for the experiment to ensure that the filling process is completed according to the predetermined coastal reservoir shape while the sand is filled with water; at a certain distance to the right of the groundwater recharge area, a plurality of nutrient salt input devices are arranged vertically with the same spacing; at a certain distance to the left of the seawater area and a certain distance below the top of the simulated water tank, a plurality of nutrient salt input devices are arranged horizontally with equal spacing. The nutrient salt input devices are connected to the second peristaltic pump and the third peristaltic pump through a hose. Before the experiment starts, the peristaltic pumps are all in a closed state;

[0021] (4) Arrange nitrogen, phosphorus and potassium sensors, calibrate the nitrogen, phosphorus and potassium sensors with nutrient salt standard solutions and connect them to the nutrient salt data processor. During the process of filling the experimental white quartz sand, place the nitrogen, phosphorus and potassium sensors at the preset position on the back of the simulated water tank, and compact the experimental sand around the nitrogen, phosphorus and potassium sensors;

[0022] (5) Run the experiment, open the connecting valve on the simulated water tank, and allow inland groundwater and seawater to enter the coastal reservoir and adjacent aquifers. During the experiment, use a microsampler to extract the coastal reservoir water and adjacent aquifer pore water through the sampling hole on the back of the water tank, and use the nutrient monitoring system to record the temporal and spatial variation data of nitrogen, phosphorus and potassium nutrients in real time; turn on the second peristaltic pump and the third peristaltic pump to allow surface-underground nutrient pollutants to enter the coastal reservoir and adjacent aquifers; use a camera to record the migration process of different colors of seawater and point source nutrient pollutants in the coastal reservoir in real time;

[0023] (6) Sampling in a stable state: when the experiment has entered a stable state, the surface and groundwater and quartz sand of the entire vertical section are collected. Before sampling the surface and groundwater and quartz sand of the entire vertical section in the simulated water tank, the adapter block is removed from the interface groove, so that the wire rope is in a relaxed state and the stainless steel patch is kept perpendicular to the bottom of the hollow tube. When the experiment has entered a stable state, sampling is ready to begin. The hollow tube is inserted into the corresponding section at a uniform speed through the multi-section telescopic motor. When the bottom of the hollow tube is at a certain distance from the bottom of the water tank, the multi-section telescopic motor is controlled to stop descending, and then the adapter block is rotated to make the hollow tube move. The steel wire rope is wound and tightened, and the stainless steel patch at the bottom of multiple hollow tubes is controlled to rotate upward through the second iron ring at the same time, until the bottom of each sampler is completely closed, the adapter block wrapped with the steel wire rope is put back into the interface groove, and the closing plate is fixed in the interface groove by fixing screws to ensure that the adapter block cannot move, and finally the multi-section telescopic motor is controlled to move the hollow tube upward and remove it; the experimental sand in the hollow tube is layered according to different elevations and then loaded into the culture bottle, and the nitrification and denitrification rates in the freshwater area and the saltwater-freshwater mixed area of ​​the coastal reservoir and the adjacent aquifer are measured;

[0024] (7) Stop the experiment and data analysis. After the experiment, turn off the power supply, take out the experimental sand and wash it with deionized water, and then repeat the next set of experiments according to the above steps; organize the photos at different times, and qualitatively analyze the invasion distance and diffusion range of marine, terrestrial and point sources of nutrients; quantitatively explain the spatiotemporal distribution law and eutrophication degree of nutrients in coastal reservoirs by analyzing the in-situ data of nutrient concentration changes at different locations; determine the nitrification and denitrification rates of the vertical section of the coastal reservoir in a stable state; and calculate the total volume V of the coastal reservoir water body by dividing the total volume V of the coastal reservoir water body by the total volume V of the coastal reservoir water body. re Total volume of groundwater in the aquifer V aq As the control body, the following formula is fitted so that the mathematical relationship between the change of nutrient concentration in coastal reservoirs and aquifers and groundwater flow can be described as follows:

[0025]

[0026] The average nutrient concentration monitored by the sampling holes and nitrogen, phosphorus and potassium sensors in the flume coastal reservoir is C re,iThe subscript i in the formula represents the ith nutrient concentration, and the average nutrient concentration C monitored by the sampling holes and nitrogen and potassium sensors in the groundwater of the aquifer is aq,i , the nutrient concentration of the standard solution tank is C point,i , the nutrient concentration of the land-based recharge water tank is C inland,i , the nutrient concentration of the seawater tank is C sea,i , the biochemical reaction rate of nutrients in coastal reservoirs is R re,i , the biochemical reaction rate of nutrients in the aquifer is R aq,i , the flow rate of the first peristaltic pump is Q inland , the flow rate of the second peristaltic pump is Q point1 , the flow rate of the third peristaltic pump is Q point2 , the tidal-driven seawater flow is Q sea .

[0027] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention can intuitively simulate and characterize the surface-underground nutrient migration and transformation process of coastal reservoirs; the present invention can realize the simulation of nutrient migration and transformation of coastal reservoirs and adjacent aquifers under the influence of surface and underground pollutant release of different concentrations and flow rates through a nutrient simulation system; the nutrient monitoring system of the present invention can record the temporal and spatial variation data of nitrogen, phosphorus and potassium nutrients in coastal reservoirs and adjacent aquifers in real time, saving manpower costs while having high reliability of data results; the vertical full-section sampling device of the present invention can monitor the changing law of the nutrient reaction (nitrification reaction, denitrification reaction) rate in the surface-underground water body of coastal reservoirs, so as to study the mechanism of nutrient migration reaction of coastal reservoirs under different conditions, and provide scientific guidance for nutrient pollution control of coastal reservoirs and adjacent aquifers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the main view of the device in the present invention;

[0029] Figure 2 It is a schematic diagram of the vertical full-section sampling device in the present invention at the highest position;

[0030] Figure 3 It is a schematic diagram of the vertical full-section sampling system of the present invention at the lowest position;

[0031] Figure 4 is a schematic diagram of a nutrient salt monitoring system of the present invention;

[0032] Figure 5 for Figure 2 A local enlarged schematic diagram before sampling at point A;

[0033] Figure 6 for Figure 2 A local enlarged schematic diagram before sampling at B in the middle;

[0034] Figure 7 for Figure 3 A local enlarged schematic diagram after sampling at C in the middle;

[0035] Figure 8 for Figure 3 A partial enlarged schematic diagram of point D in the middle. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0037] like Figure 1 , Figure 2 and Figure 4 As shown, the present invention is an experimental device for simulating the migration and transformation of nutrients in coastal reservoirs, including a simulated water tank 1, a terrestrial supply system, a tidal generation system, a dam simulation system, a nutrient simulation system, a vertical full-section sampling device, a nutrient monitoring system and a camera system.

[0038] The simulated water tank 1 is made of an acrylic glass plate with a thickness of 2 cm. The simulated water tank 1 is 340 cm long, 2 cm wide and 70 cm high. The inside of the simulated water tank 1 is divided from left to right into a groundwater recharge area 101, a coastal reservoir simulation area 102 and a seawater area 103 by a permeable partition plate 4 and a dam simulation system. The groundwater recharge area 101 simulates the boundary of inland groundwater with a constant flow and a constant concentration. The bottom of the groundwater recharge area 101 is connected to the terrestrial supply water tank 2 through a first peristaltic pump 3. The first peristaltic pump 3 is a BW100 peristaltic pump. The first peristaltic pump 3 pumps inland groundwater from the terrestrial supply water tank 2 into the groundwater recharge area 101. The inland groundwater recharge amount is controlled by the first peristaltic pump 3. The terrestrial supply water tank 2 contains a first liquid. The first liquid is used to simulate inland groundwater. The first liquid is prepared by mixing deionized water and a potassium nitrate standard solution. The nitrogen nutrient concentration of the inland groundwater is controlled by the amount of the added potassium nitrate standard solution. The seawater area 103 simulates a marine boundary with variable water head. The bottom of the seawater area 103 is connected to the tidal wave generator 5. The tidal wave generator 5 is connected to the seawater tank 7 through a submersible pump 6. The submersible pump 6 pumps simulated seawater from the seawater tank 7 into the tidal wave generator 5. The periodically changing water level signal generated by the tidal wave generator 5 enters the seawater area 103 to form a marine boundary with tidal fluctuation conditions. The seawater tank 7 contains a second liquid, which is used to simulate seawater. The second liquid is prepared by mixing deionized water, table salt and ammonium chloride standard solution, and is dyed with a first dye, which is a food red dye. The coastal reservoir simulation area 102 simulates a coastal reservoir and adjacent coastal aquifers. It is filled with white quartz sand. The height of the quartz sand needs to be higher than the liquid level of the groundwater recharge area and the seawater area. The particle size of the quartz sand is d 50 =0.24mm,d 90 / d10 =2.86. The saturated hydraulic conductivity of the sand used in the experiment of the present invention is measured by the constant head method to be 4.78×10 -3 ms -1 The porosity is 0.46. The sand sample is washed several times with deionized water before use and placed in water for later use.

[0039] The dam simulation system is installed between the coastal reservoir simulation area 102 and the seawater area 103. The dam simulation system includes an impermeable baffle 8 and a sliding groove 9. The impermeable baffle 8 can move up and down along the sliding groove 9; the sliding groove 9 is installed at a distance of 10 cm from the right side boundary of the simulated water tank 1. The impermeable baffle 8 is made of an acrylic plate with a length of 2 cm, a width of 2 cm, and a height of 40 cm. The impermeable baffle is sealed with a waterproof tape. The sliding groove 9 is fixed to the inner wall of the simulated water tank 1. The sliding groove includes a stainless steel frame and a gauze with a length of 2 cm, a width of 2 cm, and a height of 70 cm. By sliding the position of the impermeable baffle 8, adjusting the height of the impermeable baffle 8 on the sliding groove 9, and changing the size of the permeable groove on the sliding groove 9, the coastal reservoir environment with different anti-seepage wall and dam parameters can be quantitatively controlled.

[0040] The nutrient salt simulation system includes a standard solution tank 10, a second peristaltic pump 11, a third peristaltic pump 12 and a nutrient salt input device 13. The second peristaltic pump 11 and the third peristaltic pump 12 are both BW100 peristaltic pumps. The liquid in the standard solution tank 10 is prepared by deionized water, potassium nitrate and ammonium chloride standard solution. The liquid in the standard solution tank 10 is dyed with a second dye, and the second dye is bright blue to distinguish inland groundwater from marine nitrogen. The standard solution tank 10 is connected to the second peristaltic pump 11, the third peristaltic pump 11 and the nutrient salt input device 13 in sequence through a silicone transparent hose. The nutrient salt input device 13 is composed of a hollow stainless steel cube frame and a gauze. The stainless steel cube The length, width and height of the frame are all 1 cm. The gauze is permeable and can also isolate the experimental sand. The nutrient input device 13 is fixed on the inner wall of the simulated water tank 1. The vertical array of the nutrient input device 13 is set 15 cm to the right of the groundwater recharge area 101, and 5 nutrient input devices 13 are vertically arranged with the same spacing of 10 cm. The nutrient input device 13 is horizontally arranged 5 cm to the left of the seawater area 103 and 25 cm below the top of the simulated water tank 1. 6 nutrient input devices 13 are horizontally arranged with an equal spacing of 15 cm. The nutrient simulation system can simulate point source pollutants with different flow rates and concentrations entering the coastal reservoir and adjacent aquifers from the surface and underground respectively.

[0041] like Figure 2 and Figure 3As shown, the vertical full-section sampling device includes a working platform 14, a multi-section telescopic motor 15, a connecting plate 16 and a sampler 17. The working platform 14 is fixed 15 cm outside the simulated water tank 1, and the height of the working platform 14 is 60 cm. The multi-section telescopic motor 15 is vertically placed on the working platform. The multi-section telescopic motor 15 has 8 telescopic sections with a stroke of 15 cm. The telescopic range of the multi-section telescopic motor 15 is 15 cm to 120 cm. The connecting plate 16 includes an acrylic plate with a length of 210 cm, a width of 10 cm, and a height of 10 cm, a fixing buckle 1601, a welding block 1602, and an interface groove 1603. 03, fixing screws 1604 and closing plate 1605, the connecting plate 16 is fixed to the top of the multi-section telescopic motor 15 by a welding block 1602, the fixing buckles 1601 are respectively arranged at 30cm, 50cm, 70cm, 110cm, 155cm and 190cm from the left side of the working platform 14, the interface groove 1603 is arranged on the connecting plate 16, and the interface groove 1603 is arranged at a position 100cm from the right side of the connecting plate 16, the dimensions of the interface groove 1603 are 5.2cm long, 4.2cm wide and 3.2cm deep, and the outer diameter of the fixing screw 1604 is 1cm. The fixing screws 1604 are placed 1 cm on both sides of the interface groove 1603. The closing plate 1605 is an acrylic plate with a length of 8 cm, a width of 4 cm, and a height of 1 cm. A rectangular block with a length of 3 cm, a width of 2 cm, and a height of 1 cm is excavated on the closing plate 1605, making the closing plate 1605 a rectangular annular plate. Two small holes are provided on the edge of the closing plate, and the inner diameter of the small holes is 1.2 cm, so that the interface groove 1603 is connected to the fixing screws 1604.

[0042] like Figure 5 , Figure 6 , Figure 7 and Figure 8As shown, the sampler 17 is connected to the connecting plate 16 by a fixed buckle 1601, wherein the samplers 17 at 30cm, 50cm, 70cm, and 110cm from the left side of the working platform 14 mainly monitor the migration and transformation of nutrients in the coastal reservoir-groundwater-seawater exchange process, and the samplers 17 at 155cm and 190cm from the left side of the working platform 14 mainly monitor the inland groundwater migration path and nitrate nitrogen reaction process. Such spacing setting can ensure that the main hydrodynamics and nutrient migration and transformation processes in the operation process of the coastal reservoir are fully captured to the greatest extent, and can also ensure the feasibility of the sampling process in a relatively economical manner. The connection position of the sampler 17 and the fixing buckle 1601 is 10 cm away from the top of the sampler. The sampler 17 includes a hollow tube 1701, a stainless steel patch 1702, a steel wire rope 1703, a first iron ring 1704, a second iron ring 1705, a folding hinge 1706 and a transfer block 1707. The hollow tube 1701 is composed of a stainless steel tube with a length of 2 cm, a width of 2 cm and a height of 90 cm. The stainless steel patch 1702 is a stainless steel plate with a length of 4 cm, a width of 2 cm and a height of 1 cm. The stainless steel patch 1702 is fixed to the bottom of the hollow tube 1701 by a folding hinge 1706. The first iron ring 1704 and the second iron ring 1705 are respectively fixed to the outer side of the top of the hollow tube 1701 and the inner wall of the stainless steel patch 1702. One end of the steel wire rope 1703 is fixed on the second iron ring 1705. The steel wire rope 1703 passes through the first iron ring 1704 and the other end is fixed to the second iron ring 1705. The end is fixed on the adapter block 1707. Such a design can ensure that the adapter block 1707 simultaneously contracts and relaxes the steel wire rope 1703 and controls the stainless steel patch 1702 at the bottom of the hollow tube 1701 to rotate upward and downward. The bottom stainless steel patch 1702 rotates upward until the bottom of the hollow tube 1701 is completely closed, so that the vertical full-section soil and water in the sampler 17 will not leak downward, and it can also ensure that the nutrient salt storage form and reaction process in the sampler 17 are consistent with the state in the simulated water tank 1. The adapter block 1707 is an acrylic plate with a length of 5 cm, a width of 4 cm, and a height of 3 cm. There is a small hole with a diameter of 0.5 cm on the top of the adapter block 1707. Six steel wire ropes 1703 are knotted and fixed in the small hole. Through the control of the multi-section telescopic motor 15 and the sampler 17, the vertical full-section soil and water of the surface and underground of the coastal reservoir can be collected. The position of the fixing buckle 1601 is determined according to the length of the water flume and the terrain size of the coastal reservoir. When the length of the simulated water flume 1 is 340 cm, the bottom length of the coastal reservoir is 40 cm, and the slope of the coastal reservoir bank is 1:2.7, the fixing buckle 1601 is respectively set at 30 cm, 50 cm, 70 cm, 110 cm, 155 cm and 190 cm from the left side of the working platform 14.

[0043] like Figure 4As shown, the nutrient monitoring system includes sampling holes 18, nitrogen, phosphorus and potassium sensors 19, nutrient data processors 20 and displays 21. Eight rows of sampling holes 18 are arranged at different depths of 5 cm, 20 cm, 35 cm and 45 cm on the back of the simulated water tank 1. The diameter of the sampling holes 18 is 5 mm. The sampling holes 18 are filled with white silica gel to ensure the entry of the micro-sampling needle while preventing the water in the simulated water tank 1 from flowing out. Five rows of nitrogen, phosphorus and potassium sensors 18 are arranged at different depths of 10 cm and 30 cm on the back of the simulated water tank 1. The arrangement at the depths of 10 cm and 30 cm is mainly due to the fact that the aquifer above 45 cm in the operation of the coastal reservoir is in an unsaturated state, and the measured nitrogen, phosphorus and potassium nutrient concentration is likely to be distorted. In addition, the water flow migration path and the corresponding exchange flux in the aquifer above 45 cm are extremely small and can be ignored. Therefore, the nutrient concentration monitoring at the depths of 10 cm and 30 cm can not only obtain high-precision nitrogen, phosphorus and potassium concentration data, but also ensure real-time monitoring of the nutrient concentration level in areas with strong hydrodynamic exchange capacity. Five rows of nitrogen, phosphorus and potassium sensors 18 are arranged at 10 cm, 35 cm, 60 cm, 90 cm and 250 cm from the left side of the seawater area 103. The arrangement positions of the five rows of nitrogen, phosphorus and potassium sensors 18 are mainly considered to monitor the real-time data of the coastal reservoir nutrient migration flux and the area with strong conversion rate while avoiding the conflict with the vertical full-section sampling device. Among them, the four rows of nitrogen, phosphorus and potassium sensors 18 at 10 cm, 35 cm, 60 cm and 90 cm from the left side of the seawater area 103 monitor the nitrogen, phosphorus and potassium data around the coastal reservoir dam, at the bottom and on the side bank; the four rows of nitrogen, phosphorus and potassium sensors 18 at 250 cm from the left side of the seawater area 103 monitor the nitrogen, phosphorus and potassium data of inland groundwater and the point source nutrient input device 13 near the inland boundary; the four rows of nitrogen, phosphorus and potassium sensors 18 at 10 cm, 35 cm, 60 cm and 90 cm from the left side of the seawater area 103 monitor the nitrogen, phosphorus and potassium data of inland groundwater and the point source nutrient input device 13 near the inland boundary; Two nitrogen, phosphorus and potassium sensors 18 with a depth of 45 cm are arranged at cm to measure the real-time changes in the concentration of nitrogen, phosphorus and potassium nutrients at different elevations in the water body of the coastal reservoir, and are also used to directly monitor the impact of the point source nutrient input device 13 on the water quality of the coastal reservoir. One end of the nitrogen, phosphorus and potassium sensor 18 is connected to the nutrient salt data processor 20, and the nutrient salt data processor 20 is connected to the display 21. The nitrogen, phosphorus and potassium sensor 18 can monitor the changes in nutrients inside the simulated water tank 1 and transmit the high-frequency monitoring data to the nutrient salt data processor 20. The nutrient salt data processor 20 can record the high-frequency monitoring data and transmit the recorded data to the display 21. The nutrient salt monitoring system can experimentally simulate the in-situ monitoring of the temporal and spatial changes of nutrients in the water tank 1. The above-mentioned arrangement of nitrogen, phosphorus and potassium sensors 18 can monitor the nutrient data of surface water and groundwater in coastal reservoirs at high frequency. By considering the data processing formula of generalized convective transport and chemical reactions, combined with the initial conditions of nutrients such as ammonia nitrogen and nitrate nitrogen in the terrestrial supply water tank 2, the standard solution tank 10 and the seawater tank 7, the coastal reservoir-groundwater-seawater exchange flux, the nutrient migration path and the nutrient conversion process are derived.

[0044] The camera system is a high-definition camera system, which includes a high-definition camera 22, a desktop computer 23, a blackout curtain 24 and a lighting panel 25. The high-definition camera 22 is located in front of the simulated water tank 1. The position and shooting angle of the high-definition camera 22 are adjusted to ensure that the front of the simulated water tank 1 can be recorded. The high-definition camera 22 is connected to the desktop computer 23, and the shooting frequency and duration of the high-definition camera 21 are controlled by the desktop computer 23. A blackout curtain 24 is arranged around the high-definition camera 22 and the simulated water tank 1. The blackout curtain forms a dark room with a length of 4m, a height of 2m and a width of 1.5m. The lighting panel 25 is placed directly above the simulated water tank 1 and consists of evenly distributed LED light strips.

[0045] The present invention provides an experimental method for an experimental device for simulating the migration and transformation of nutrients in a coastal reservoir, comprising the following steps:

[0046] (1) Prepare the white quartz sand and nutrient salt solution for the experiment, and the sieve particle size is d 50 =0.24mm,d 90 / d 10 =2.86 quartz sand is washed with deionized water for multiple times. After washing, the white quartz sand is placed in a bucket in a saturated water manner for standby use; the inland recharge groundwater is mixed with deionized water and potassium nitrate standard solution. The nitrate nitrogen concentration of the terrestrial recharge groundwater is set according to different working conditions. The nitrate nitrogen concentration of the terrestrial recharge groundwater can be 20mg / L, 50mg / L and 100mg / L respectively, and its salinity is 0g / L; the configuration seawater is mixed with deionized water, industrial salt, ammonium chloride standard solution and edible red dye. The ammonia nitrogen concentration of the seawater is set according to different working conditions. The ammonia nitrogen concentration of the seawater can be 5mg / L, 10mg / L and 20mg / L respectively, and its salinity is 35g / L. While distinguishing inland groundwater, it simulates the influence of different sea-source ammonia nitrogen on the migration and transformation of nutrients in coastal reservoirs; the pollutants in the standard solution tank are prepared by deionized water, potassium nitrate, ammonium chloride and the second dye to distinguish inland groundwater from sea-source nitrogen;

[0047] (2) Regulating the coastal reservoir environment, by adjusting the relative position of the impermeable baffle in the sliding groove, adjusting the size of the coastal reservoir dam and the anti-seepage wall; controlling the average sea level, tidal amplitude and period of the tidal wave generator to influence the tidal signal of the coastal reservoir; turning on the first peristaltic pump, placing the hose into the land-based supply water tank, waiting for all the bubbles in the hose to be eliminated, and adjusting the input of underground fresh water by adjusting the first peristaltic pump;

[0048] (3) Arrange the white quartz sand and nutrient salt input device for the experiment. After placing 10 cm high deionized water in the simulated water tank, use a funnel to evenly fill the cleaned white quartz sand for the experiment at the bottom of the simulated water tank. During the filling process, the deionized water level is controlled to be 10 cm higher than the white quartz sand for the experiment to ensure that the filling process is completed according to the predetermined coastal reservoir shape while the sand is filled with water; 5 nutrient salt input devices are arranged vertically with the same spacing of 10 cm at 15 cm to the right of the groundwater recharge area, and 6 nutrient salt input devices are arranged horizontally with an equal spacing of 15 cm at 5 cm to the left of the seawater area and 25 cm below the top of the simulated water tank. The nutrient salt input devices are connected to the second peristaltic pump and the third peristaltic pump through a hose. Before the experiment starts, the peristaltic pumps are all in the off state;

[0049] (4) Arrange nitrogen, phosphorus and potassium sensors, calibrate them with nutrient salt standard solution and connect them to nutrient salt data processor. During the process of filling the experimental white quartz sand, place the nitrogen, phosphorus and potassium sensors at the preset position on the back of the simulated water tank, and compact the experimental sand around the nitrogen, phosphorus and potassium sensors to prevent the appearance of large gaps and increase the measurement accuracy of the nitrogen, phosphorus and potassium sensors.

[0050] (5) Run the experiment, open the connecting valve on the simulated water tank, and allow inland groundwater and seawater to enter the coastal reservoir and adjacent aquifers. During the experiment, use a microsampler to extract the coastal reservoir water and adjacent aquifer pore water through the sampling hole on the back of the water tank, and use the nutrient monitoring system to record the temporal and spatial variation data of nitrogen, phosphorus and potassium nutrients in real time; turn on the second peristaltic pump and the third peristaltic pump to allow surface-underground nutrient pollutants to enter the coastal reservoir and adjacent aquifers; use a camera to take pictures every 1 minute to record the migration and transformation process of different colors of seawater and point source nutrient pollutants in the coastal reservoir in real time;

[0051] (6) Sampling in a stable state: when the experiment has entered a stable state, the surface and groundwater and quartz sand of the entire vertical section are collected. Before sampling the surface and groundwater and quartz sand of the entire vertical section in the simulated water tank, the adapter block is removed from the interface groove, so that the wire rope is in a relaxed state and the stainless steel patch is kept perpendicular to the bottom of the hollow tube. When the experiment has entered a stable state, sampling is ready to begin. The hollow tube is controlled by a multi-section telescopic motor to insert into the corresponding section at a uniform speed. When the bottom of the hollow tube is 5 cm away from the bottom of the water tank, the multi-section telescopic motor is controlled to stop descending, and then the adapter block is rotated to make the wire rope wind and tighten. The bottom of multiple hollow tubes is controlled by the second iron ring to rotate the stainless steel patch upward until the bottom of each sampler is completely closed, the adapter block wrapped with the wire rope is put back into the interface groove, the closing plate is fixed in the interface groove by fixing screws to ensure that the adapter block cannot move, and finally the multi-section telescopic motor is controlled to move the hollow tube upward 0.7m and remove it; the experimental sand in the hollow tube is layered according to different elevations and then loaded into the culture bottle, and the nitrification and denitrification rates in the freshwater area and saltwater-freshwater mixed area of ​​the coastal reservoir and adjacent aquifer are measured by the 15N culture method and the anaerobic flooding culture method respectively;

[0052] (7) Stop the experiment and data analysis. After the experiment, turn off the power supply, take out the experimental sand and wash it with deionized water, and then repeat the next set of experiments according to the above steps; organize the photos at different times, and qualitatively analyze the invasion distance and diffusion range of marine, terrestrial and point sources of nutrients; quantitatively explain the spatiotemporal distribution law and eutrophication degree of nutrients in coastal reservoirs by analyzing the in-situ data of nutrient concentration changes at different locations; determine the nitrification and denitrification rates of the vertical section of the coastal reservoir in a stable state, reveal the chemical reaction law of nutrients in the coastal reservoir and reveal the influencing mechanism; by calculating the total volume V of the coastal reservoir water body re Total volume of groundwater in the aquifer V aq As the control body, the following formula is fitted to describe the mathematical relationship between the change of nutrient concentration in coastal reservoirs and aquifers and groundwater flow:

[0053]

[0054] The average nutrient concentration monitored by the sampling holes and nitrogen, phosphorus and potassium sensors in the flume coastal reservoir is C re,i The subscript i in the formula represents the ith nutrient concentration, and the average nutrient concentration C monitored by the sampling holes and nitrogen and potassium sensors in the groundwater of the aquifer is aq,i , the nutrient concentration of the standard solution tank is C point,i , the nutrient concentration of the land-based recharge water tank is C inland,i , the nutrient concentration of the seawater tank is C sea,i , the biochemical reaction rate of nutrients in coastal reservoirs is R re,i , the biochemical reaction rate of nutrients in the aquifer is Raq,i , the flow rate of the first peristaltic pump is Q inland , the flow rate of the second peristaltic pump is Q point1 , the flow rate of the third peristaltic pump is Q point2 , the tidal-driven seawater flow is Q sea ; The unit of nutrient concentration is ML -3 , the unit of nutrient biochemical reaction rate is ML -3 T, the unit of flow is L 3 T -1 .

Claims

1. An experimental method for simulating the migration and transformation of nutrients in coastal reservoirs, characterized in that: The experimental device comprises a simulated water tank (1) which is divided from left to right into a groundwater recharge area (101), a coastal reservoir simulation area (102) and a seawater area (103), a land-source recharge system connected to the groundwater recharge area, a tidal generation system connected to the seawater area, a dam simulation system located at the boundary between the coastal reservoir simulation area and the seawater area and used to adjust dam parameters to simulate the coastal reservoir environment, a nutrient simulation system used to simulate point source pollutants entering the coastal reservoir and adjacent aquifers from the surface underground, a vertical full-section sampling device used to collect soil and water bodies in a vertical full-section of the surface underground of the coastal reservoir, a nutrient monitoring system used to monitor the real-time changes in nutrient concentration of point source pollutants entering the coastal reservoir and adjacent aquifers from the surface underground, and a camera system used to capture the nutrient migration and transformation process; The experimental method comprises the following steps: (1) Prepare white quartz sand and nutrient salt solution for the experiment. After screening the white quartz sand, wash it with deionized water for multiple times. After washing, place the white quartz sand in a bucket with saturated water for standby use. Inland recharge groundwater is mixed with deionized water and potassium nitrate standard solution. The nitrate nitrogen concentration of land-based recharge groundwater is set according to different working conditions. Prepare seawater by mixing deionized water, industrial salt, ammonium chloride standard solution and the first dye. Set the ammonia nitrogen concentration and salinity of seawater according to different working conditions, distinguish inland groundwater and simulate the influence of ammonia nitrogen from different sea sources on the migration and transformation of nutrients in coastal reservoirs. The pollutants in the standard solution box are prepared from deionized water, potassium nitrate, ammonium chloride and a second dye to distinguish between inland groundwater and marine nitrogen; (2) Regulate the coastal reservoir environment by adjusting the relative position of the impermeable baffle in the sliding groove and adjusting the size of the coastal reservoir dam and the anti-seepage wall; influence the tidal signal of the coastal reservoir by controlling the average sea level, tidal amplitude and period of the tidal wave generator; turn on the first peristaltic pump, put the hose into the land-based supply water tank, wait for all the bubbles in the hose to be eliminated, and adjust the input of groundwater by adjusting the first peristaltic pump; (3) Arrange the white quartz sand and nutrient salt input device for the experiment. After placing a certain height of deionized water in the simulated water tank, use a funnel to evenly fill the cleaned white quartz sand for the experiment at the bottom of the simulated water tank. During the filling process, the deionized water level is controlled to be higher than the white quartz sand for the experiment by a certain height to ensure that the sand is filled with water and the filling process is completed according to the predetermined coastal reservoir shape; at a certain distance to the right of the groundwater recharge area, multiple nutrient salt input devices are arranged vertically with the same spacing; at a certain distance to the left of the seawater area and a certain distance below the top of the simulated water tank, multiple nutrient salt input devices are arranged horizontally with equal spacing. The nutrient salt input devices are connected to the second peristaltic pump and the third peristaltic pump through a hose. Before the experiment starts, the peristaltic pumps are all in the off state; (4) Arrange nitrogen, phosphorus and potassium sensors, calibrate them with nutrient standard solution and connect them to the nutrient data processor. During the process of filling the experimental white quartz sand, place the nitrogen, phosphorus and potassium sensors at the preset position on the back of the simulated water tank and compact the experimental sand around the nitrogen, phosphorus and potassium sensors. (5) Run the experiment, open the connecting valve on the simulated water tank, and allow inland groundwater and seawater to enter the coastal reservoir and adjacent aquifers. During the experiment, use a microsampler to extract the coastal reservoir water and adjacent aquifer pore water through the sampling hole on the back of the water tank, and use the nutrient monitoring system to record the temporal and spatial variation data of nitrogen, phosphorus and potassium nutrients in real time; turn on the second peristaltic pump and the third peristaltic pump to allow surface-underground nutrient pollutants to enter the coastal reservoir and adjacent aquifers; use a camera to record the migration process of different colors of seawater and point source nutrient pollutants in the coastal reservoir in real time; (6) Sampling in a stable state: when the experiment has entered a stable state, the surface and groundwater and quartz sand of the entire vertical section are collected. Before sampling the surface and groundwater and quartz sand of the entire vertical section in the simulated water tank, the adapter block is removed from the interface groove, so that the wire rope is in a relaxed state and the stainless steel patch is kept perpendicular to the bottom of the hollow tube. When the experiment has entered a stable state, sampling is ready to begin. The hollow tube is inserted into the corresponding section at a uniform speed through a multi-section telescopic motor. When the bottom of the hollow tube is at a certain distance from the bottom of the water tank, the multi-section telescopic motor is controlled to stop descending, and then the adapter block is rotated. The steel wire rope is wound and tightened, and the stainless steel patches at the bottom of multiple hollow tubes are controlled to rotate upwards through the second iron ring at the same time until the bottom of each sampler is completely closed, and the adapter block wrapped with the steel wire rope is put back into the interface groove, and the closing plate is fixed in the interface groove by fixing screws to ensure that the adapter block cannot move, and finally the multi-section telescopic motor is controlled to move the hollow tube upward and remove it; the experimental sand in the hollow tube is layered according to different elevations and then loaded into the culture bottle, and the nitrification and denitrification rates in the freshwater area and the saltwater-freshwater mixed area of ​​the coastal reservoir and the adjacent aquifer are measured; (7) Stop the experiment and data analysis. After the experiment, turn off the power supply, take out the experimental sand and wash it with deionized water, and then repeat the next set of experiments according to the above steps; organize the photos at different times, and qualitatively analyze the invasion distance and diffusion range of marine, terrestrial and point sources of nutrients; quantitatively explain the spatiotemporal distribution law and eutrophication degree of nutrients in coastal reservoirs by analyzing the in-situ data of nutrient concentration changes at different locations; determine the nitrification and denitrification rates of the vertical section of the coastal reservoir in a stable state; and calculate the total volume V of the coastal reservoir water body by dividing the total volume V of the coastal reservoir water body by the total volume V of the coastal reservoir water body. re Total volume of groundwater in the aquifer V aq As the control body, the following formula is fitted so that the mathematical relationship between the change of nutrient concentration in coastal reservoirs and aquifers and groundwater flow can be described as follows: ， The average nutrient concentration monitored by sampling holes and nitrogen, phosphorus and potassium sensors in the simulated flume coastal reservoir is C re,i , small standard in formula i Indicates i Nutrient concentrations, average nutrient concentrations monitored by sampling wells and nitrogen and potassium sensors in groundwater in the aquifer C aq,i , the nutrient salt concentration in the standard solution tank is C point,i , the nutrient concentration of the terrestrial recharge water tank is C inland,i , the nutrient concentration of the seawater tank is C sea,i , the biochemical reaction rate of nutrients in coastal reservoirs is R re , i , the biochemical reaction rate of nutrients in the aquifer is R aq , i , the flow rate of the first peristaltic pump is Q inland , the flow rate of the second peristaltic pump is Q point1 , the flow rate of the third peristaltic pump is Q point2 , the tidal-driven seawater flow is Q sea。 2. The experimental method of the experimental device for simulating the migration and transformation of nutrients in coastal reservoirs according to claim 1 is characterized in that: The coastal reservoir simulation area (102) is filled with white quartz sand, the height of the white quartz sand is higher than the liquid level of the groundwater recharge area (101) and the seawater area (103), the coastal reservoir simulation area (102) is used to simulate the coastal reservoir and the adjacent coastal aquifer, the groundwater recharge area (101) simulates the inland groundwater boundary, the seawater area (103) simulates the ocean boundary with variable water head, and a permeable partition plate (4) is provided at the boundary between the groundwater recharge area (101) and the coastal reservoir simulation area (102).

3. The experimental method of the experimental device for simulating the migration and transformation of nutrients in coastal reservoirs according to claim 1 is characterized in that: The land-source recharge system comprises a land-source recharge water tank (2) connected to the bottom of a groundwater recharge area (101) via a first peristaltic pump (3), wherein the land-source recharge water tank (2) contains a first liquid simulating inland groundwater.

4. The experimental method of the experimental device for simulating the migration and transformation of nutrients in coastal reservoirs according to claim 1 is characterized in that: The tidal wave generating system comprises a tidal wave generator (5) connected to the bottom of a seawater area (103) and a seawater tank (7) connected to the tidal wave generator via a submersible pump (6); a second liquid simulating seawater and dyed with a first dye is contained in the seawater tank (7); the submersible pump (6) pumps the second liquid from the seawater tank (7) into the tidal wave generator (5); a periodically changing water level signal generated by the tidal wave generator (5) enters the seawater area, thereby forming a marine boundary with tidal fluctuation conditions.

5. The experimental method of the experimental device for simulating the migration and transformation of nutrients in coastal reservoirs according to claim 1 is characterized in that: The dam simulation system comprises a water-permeable sliding groove (9) located at the boundary between the coastal reservoir simulation area and the seawater area, and a water-impermeable partition (8) located in the sliding groove (9) and movable up and down along the sliding groove.

6. The experimental method of the experimental device for simulating the migration and transformation of nutrients in coastal reservoirs according to claim 1, characterized in that: The nutrient simulation system comprises a standard solution tank (10) containing a third liquid containing simulated point source pollutants and dyed with a second dye, a plurality of nutrient input devices (13) arranged in a vertical array near the right side of the groundwater recharge area and in a horizontal array near the left side of the seawater area and at the top of the simulated water tank, a second peristaltic pump (11) connected to the vertically arranged nutrient input devices and the standard solution tank via a hose, and a third peristaltic pump (12) connected to the horizontally arranged nutrient input devices and the standard solution tank via a hose.

7. The experimental method of the experimental device for simulating the migration and transformation of nutrients in coastal reservoirs according to claim 1 is characterized in that: The vertical full-section sampling device comprises a working platform (14), a multi-section telescopic motor (15) vertically arranged on the working platform and capable of being extended up and down, a connecting plate (16) connected to the end of the multi-section telescopic motor and horizontally arranged above the simulated water tank, and a plurality of samplers (17) arranged at intervals on the connecting plate and capable of being vertically inserted into the simulated water tank, wherein at least four samplers are arranged in the coastal reservoir and side bank area of ​​the simulated water tank, and at least two samplers are arranged in the inland area of ​​the simulated water tank; the sampler (17) comprises a hollow tube (1701), a hollow tube (1702) hinged to the hollow tube by a folding hinge (1706), and a plurality of samplers (17) arranged at intervals on the connecting plate and capable of being vertically inserted into the simulated water tank. A stainless steel patch (1702) at the lower end of the tube (1701), a first iron ring (1704) fixed on the outer wall of the top of the hollow tube, a second iron ring (1705) fixed on the inner side of the stainless steel patch, a steel wire rope (1703) with one end fixed on the second iron ring (1705) and passing through the first iron ring (1704), and a transfer block (1707) connected to the other end of the steel wire rope, wherein the upper surface of the connecting plate (16) is provided with an interface groove (1603) for accommodating the transfer block and a closing plate (1605) adapted to the interface groove for fixing the transfer block in the interface groove.

8. The experimental method of the experimental device for simulating the migration and transformation of nutrients in coastal reservoirs according to claim 1 is characterized in that: The nutrient monitoring system comprises sampling holes (18) distributed on the back of the simulated water tank, a plurality of rows of nitrogen, phosphorus and potassium sensors (19) arranged in the simulated water tank and away from the position of the vertical full-section sampling device, a nutrient data processor (20) connected to the nitrogen, phosphorus and potassium sensors, and a display (21), wherein at least four rows of nitrogen, phosphorus and potassium sensors are used to monitor nitrogen, phosphorus and potassium data around, at the bottom and on the side banks of coastal reservoir dams, and at least one row of nitrogen, phosphorus and potassium sensors is used to monitor nitrogen, phosphorus and potassium data of inland groundwater and point source nutrient solution near the inland boundary.

9. The experimental method of the experimental device for simulating the migration and transformation of nutrients in coastal reservoirs according to claim 1, characterized in that: The camera system comprises a camera (22) located in front of the simulated water tank, a desktop computer (23) connected to the camera, a light-shielding curtain (24) surrounding the camera and the simulated water tank, and a lighting panel (25) located directly above the simulated water tank.

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