A system and method for evaluating the impact of nitrogen content in lakes and reservoirs on ecological service value

Abstract

The present invention belongs to the technical field of ecological environmental assessment, specifically relating to a system and method for assessing the impact of nitrogen content in lakes and reservoirs on ecological service value. The system comprises a measuring assembly for measuring the nitrogen content of water samples and a water sampling head, the water sampling head including an opening occupying at least half the width of the sampling plane of the water sampling head. The measuring assembly comprises a sensor module located in the liquid path of the water sampling head and a temperature-control pipe for controlling the temperature of the water to be measured in the liquid path. The assessment system also includes an assessment module that inputs the nitrogen content into a pre-established quantitative assessment model and outputs a quantitative assessment value representing the impact of changes in nitrogen content on ecological service value. Based on pre-measured data detected by a temperature sensor within a collection channel, the system heats and cools water samples at multiple depths to maintain a constant temperature before measurement, thereby preventing temperature from affecting nitrogen measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of ecological environment assessment, and specifically relates to a system and method for assessing the impact of nitrogen content in lakes and reservoirs on ecological service value. Background Art

[0002] In the fields of environmental protection and water resources management, accurately assessing the nitrogen content of lake and reservoir waters and its impact on the value of their ecological services is crucial. As a key indicator of eutrophication, nitrogen levels are directly related to the ecological health of water bodies and the services they provide. However, existing technologies for assessing the impact of nitrogen content in lakes and reservoirs on their ecological services often face numerous challenges.

[0003] A significant problem is that there are significant temperature gradients in the vertical and horizontal directions of lake water bodies. This temperature difference can lead to uneven distribution of nitrogen in the water body. Traditional assessment methods usually rely on single-point or limited-point water sampling and analyze the nitrogen content accordingly. However, due to differences in water temperature, there may be significant differences in nitrogen content in water samples at different depths or locations, which directly leads to deviations and inaccuracies in the assessment results. In addition, the existing assessment system often lacks a set of scientific and systematic quantitative models to fully reflect the complex relationship between changes in nitrogen content and ecological service value. Most methods rely on empirical formulas or qualitative analysis, which makes it difficult to accurately quantify the comprehensive impact of changes in nitrogen content on multiple ecological service functions such as water quality, biodiversity, and water purification capacity. Summary of the Invention

[0004] The purpose of the present invention is to provide a system and method for evaluating the impact of nitrogen content in lakes and reservoirs on ecological service value, so as to solve the problems raised in the background technology.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] In a first aspect, the present invention provides an assessment system for the impact of nitrogen content in lakes and reservoirs on ecological service value, comprising a measurement component for measuring the nitrogen content of a water sample; and at least two water sampling heads forming an integral structure with the measurement component, the water sampling heads including openings that occupy at least half the width of a sampling plane of the water sampling heads, the measurement component comprising a sensor module located in a liquid path of the water sampling heads and a temperature control pipe for controlling the temperature of the water to be measured in the liquid path;

[0007] The evaluation system further includes an evaluation module, which inputs the nitrogen content into a pre-built quantitative evaluation model and outputs a quantitative evaluation value to characterize the impact of changes in nitrogen content on ecological service value;

[0008] The evaluation system further includes an evaluation module, which inputs the nitrogen content into a pre-built quantitative evaluation model and outputs a quantitative evaluation value to characterize the impact of changes in nitrogen content on ecological service value.

[0009] Furthermore, the sensor module includes an optical nitrogen sensor and a microprocessing unit connected to the optical nitrogen sensor signal, and the microprocessing unit is used to send the nitrogen content detected in real time by the optical nitrogen sensor to the evaluation module.

[0010] Furthermore, the water sampling head is provided with a measuring component connected to the liquid path, the sensor module is arranged inside the measuring component, and the measuring component and the water sampling head are placed at different depths of the water body to be tested through a winding member and a pull rope for sampling and detection.

[0011] Furthermore, the water sampling head includes an upper collecting tube connected to the interior of the measuring component, and a sampling end located at the lower end of the upper collecting tube, at least one opening is opened on the side wall of the sampling end, a collecting channel connected to the opening is provided inside the sampling end, and a temperature sensor is provided at the lower end of the collection channel.

[0012] Furthermore, a flow channel for connecting the temperature control tube and the collection channel is provided in the upper collecting cylinder, and an interface is provided at the lower end of the flow channel;

[0013] A solenoid valve is provided on the communication path between the opening and the collecting channel, a branch channel is provided on the path between the opening and the solenoid valve, the end of the branch channel is communicated with the side of the interface component, and a pressure regulating valve is provided at the communication point;

[0014] The pressure regulating valve is used to compare the water pressure of the water body in the branch channel with the preset sampling depth when the water sampling head is at different depths. When the water pressure meets the preset range of the corresponding sampling depth, the pressure regulating valve and the solenoid valve are opened synchronously.

[0015] Furthermore, the measuring component includes a first chamber and a second chamber, the first chamber is connected to the upper collecting cylinder, the temperature control pipe includes a U-shaped conduit arranged in the first chamber, and a temperature control component arranged thereon, the second chamber is provided with a water pump 2 connected to one port of the U-shaped conduit, the sensor module is located on the water pumping path of the water pump 2, and a temperature measuring component is also provided on the water pumping path, the other end of the U-shaped conduit faces the upper end of the first chamber and is located at two-thirds of the liquid level in the first chamber.

[0016] Furthermore, the quantitative evaluation model includes a first function and a second function, wherein the nitrogen content is input into the first function to obtain the ecological sensitivity index ESI, and then the ecological sensitivity index ESI is input into the second function to obtain the quantitative evaluation value EVA, which is used to characterize the impact of changes in nitrogen content on ecological service value, wherein the formulas of the first function and the second function are as follows:

[0017] ESI=a*ln(N+1)+b

[0018] EVA=c*ESI d +e

[0019] Among them, a is the sensitivity coefficient of the ecosystem to changes in nitrogen, b is the ecological sensitivity index baseline when the nitrogen content is zero, N is the nitrogen content, c, d and e are the assessment coefficient, sensitivity index and benchmark value respectively.

[0020] In a second aspect, the present invention proposes a method for evaluating the impact of nitrogen content in lakes and reservoirs on the ecological service value. The method is implemented based on the above-mentioned evaluation system and includes:

[0021] S1. The water sampling head is placed at different depths of the water body to be tested through a winding member and a pull rope for sampling and detection. When the water pressure meets the preset range corresponding to the sampling depth, the pressure regulating valve and the solenoid valve are opened synchronously;

[0022] S2. Sampling the water to be tested through the opening on at least one of the water sampling heads, so that the water to be tested is transported to the sensor module along the liquid path;

[0023] S3, starting the sensor module to measure the nitrogen content of the water sample, and transmitting the nitrogen content to the evaluation module;

[0024] S4. The assessment module inputs the nitrogen content into a pre-built quantitative assessment model and outputs a quantitative assessment value to characterize the impact of changes in nitrogen content on ecological service value.

[0025] The beneficial effects of the present invention are:

[0026] 1. This paper introduces a combined model of the first and second functions to directly convert nitrogen content into an ecological sensitivity index, which is then quantified into a specific ecological service value assessment. This model fully considers the impact of water temperature differences on nitrogen distribution and, through comprehensive multi-point sampling and temperature correction, ensures the accuracy and reliability of the assessment results.

[0027] 2. The present invention collects the pre-data detected by the temperature sensor in the channel and can heat and cool water samples at different depths multiple times based on the data, so that the water samples can maintain a constant temperature before measurement, thereby avoiding the influence of temperature on nitrogen measurement.

[0028] 3. The present invention provides a temperature control pipe in the first chamber, thereby achieving temperature control of the water to be tested. At the same time, the U-shaped conduit design can preferentially collect the upper layer of water in the first chamber, thereby ensuring that the collected water sample is purer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a framework diagram of the evaluation system in the present invention.

[0030] Figure 2 It is a structural schematic diagram of the water sampling head in the present invention.

[0031] Figure 3 It is a structural schematic diagram of the collecting cylinder in the present invention.

[0032] Figure 4 It is a schematic diagram of the cross-sectional structure of the collecting cylinder in the present invention.

[0033] Figure 5 It is a schematic structural diagram of the measuring component in the present invention.

[0034] In the figure: 1. Winding member; 2. Pull rope; 3. Measuring component; 4. Water sampling head; 31. First chamber; 32. Second chamber; 41. Collecting tube; 42. Water pump 1; 311. Water inlet; 312. U-shaped guide tube; 313. Temperature control component; 314. Sampling port; 321. Water pump 2; 322. Sensor module; 323. Temperature measuring component; 411. Upper collecting tube; 412. Sampling end; 413. Flow channel; 414. Opening; 415. Protrusion; 416. Positioning member; 417. Filter; 418. Collecting channel; 419. Temperature sensor; 420. Solenoid valve; 421. Branch channel; 422. Pressure regulating valve; 423. Interface member. DETAILED DESCRIPTION

[0035] The present application is described in further detail below in conjunction with the accompanying drawings. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0036] Example 1

[0037] like Figure 1-5As shown, this embodiment proposes an evaluation system for the impact of nitrogen content in lakes and reservoirs on ecological service value, including a measuring component 3 for measuring the nitrogen content of water samples; and at least two water sampling heads 4 forming an integrated structure with the measuring component 3, the water sampling head 4 including an opening 414 that occupies at least half the width of the sampling plane of the water sampling head 4, the measuring component 3 including a sensor module 322 located on the liquid path of the water sampling head 4 and a temperature control pipe for controlling the temperature of the water to be measured on the liquid path; the evaluation system also includes an evaluation module, which inputs the nitrogen content into a pre-constructed quantitative evaluation model and outputs a quantitative evaluation value to characterize the impact of changes in nitrogen content on the ecological service value.

[0038] Further preferably, the water sampling head 4 is provided with a measuring component 3 connected to the liquid path, and the sensor module 322 is arranged inside the measuring component 3. The measuring component 3 and the water sampling head 4 are placed at different depths of the water body to be tested through the winding member 1 and the pull rope 2 for sampling and detection. Specifically, the sampling is achieved by winding and unwinding the winding member 1 and the pull rope 2.

[0039] More preferably, combined with Figure 2 、 3 and 4, the water sampling head 4 includes an upper collecting cylinder 411 connected to the interior of the measuring component 3, and a sampling end 412 located at the lower end of the upper collecting cylinder 411, at least one opening 414 is opened on the side wall of the sampling end 412, a collecting channel 418 connected to the opening 414 is provided inside the sampling end 412, and a temperature sensor 419 is provided at the lower end of the collecting channel 418.

[0040] It can be understood that in this embodiment, the opening 414 occupies at least half the width of the sampling plane (the outer peripheral surface of the sampling end 412) of the water sampling head 4, and the arc path within the opening 414 is oriented towards the sampling direction of the water sampling head 4. Such a semi-open opening design allows water to enter the sampling head more smoothly, reducing resistance, thereby speeding up the sampling speed. The semi-open design allows water to enter the sampling head from a wider angle, which helps to reduce water vortexes and deviations during the sampling process and improve the uniformity and representativeness of the sampling.

[0041] Further preferably, a flow channel 413 for connecting the temperature control pipe and the collection channel 418 is provided in the upper collecting cylinder 411, and an interface part 423 is provided at the lower end of the flow channel 413 (including at least three same ports for connecting with the flow channel 413, the collection channel 418 and the branch channel 421); a solenoid valve 420 is provided on the communication path between the opening 414 and the collection channel 418, and a branch channel 421 is provided on the path between the opening 414 and the solenoid valve 420, and the end of the branch channel 421 is connected to the side of the interface part 423, and a pressure regulating valve 422 is provided at the connection point; the pressure regulating valve 422 is used to compare the water pressure of the water body in the branch channel 421 with the preset sampling depth when the water sampling head 4 is at different depths. When the water pressure meets the preset range of the corresponding sampling depth, the pressure regulating valve 422 and the solenoid valve 420 are opened synchronously.

[0042] Combine Figure 4 When the rope 2 is lowered to different depths for water sampling, due to the provision of the collection channel 418, water flows into the collection channel 418 from an arc path during the lowering of the entire device, so that a certain amount of water begins to gather at the bottom of the collection channel 418, and the temperature of the current water body is detected in real time by the temperature sensor 419. When the real-time temperatures in multiple water sampling heads 4 at different depths are inconsistent or exceed the limit value, it indicates that there is a temperature gradient in the water body in the lake reservoir area. This temperature gradient will cause uneven distribution of nitrogen elements in the water body. In specific implementation, the temperature sensor 419 in the collection channel 418 can be used to realize pre-temperature judgment, which provides a certain data basis for subsequent detection.

[0043] In addition, in this embodiment, the water sampling head 4 has an automatic sampling function. Specifically, the corresponding sampling depth is preset first. When the water pressure meets the preset range of the corresponding sampling depth, the pressure regulating valve 422 and the solenoid valve 420 are opened synchronously. Figure 4 At this point, when the water reaches the designated depth, it enters the collection channel 418 through the opening 414 for pre-temperature determination. After the temperature determination is completed, the water enters the flow channel 413 through the interface 423. During this process, the branch channel 421 can assist the water sampling head 4 in exhausting air, facilitating the entry of water. While the branch channel 421 assists in exhausting air, before the sampling depth is reached, the pressure regulating valve 422 in the channel can monitor the water pressure in real time. Based on the water pressure at this location and the preset water pressure range, it is determined whether the water sampling head has reached the preset depth.

[0044] Combine Figure 5The measuring component 3 includes a first chamber 31 and a second chamber 32. The first chamber 31 is connected to the upper collecting cylinder 411. The temperature control pipe includes a U-shaped tube 312 provided in the first chamber 31, and a temperature control component 313 provided thereon (specifically, an electric heating thermostat in this embodiment, which heats and cools the U-shaped tube 312). The second chamber 32 is provided with a water pump 2 321 connected to one end of the U-shaped tube 312. The sensor module 322 is located on the water pumping path of the water pump 2 321, and a temperature measuring component 323 is also provided on the water pumping path. The other end of the U-shaped tube 312 faces the upper end of the first chamber 31 and is located at two-thirds of the liquid level in the first chamber 31.

[0045] During specific implementation, the water to be measured in the collection channel 418 is pumped from the water inlet 311 into the first chamber 31 through water pump 1 42 until the water level inside the first chamber 31 reaches two-thirds. Then, based on the data detected by the temperature sensor 419 in the collection channel 418, water samples at different depths can be heated and cooled multiple times to keep a constant temperature before measurement to avoid the influence of temperature on nitrogen measurement. Then, water pump 2 321 is started to pump the water in the first chamber 31 from the U-shaped conduit 312 into the temperature measuring component 323 and sensor module 322 in the second chamber 32. The temperature measuring component 323 is specifically another liquid temperature sensor.

[0046] It can be appreciated that by installing a temperature-controlled tube in first chamber 31, the temperature of the water being tested is controlled. Furthermore, the U-shaped conduit 312 preferentially collects the upper layer of water within first chamber 31, ensuring a purer water sample. Because impurities and contaminants in water tend to settle in the lower layers, the upper layer is relatively clean and more suitable as a test sample. Collecting the upper layer reduces interfering substances in the sample, thereby improving the accuracy of nitrogen measurement.

[0047] Further preferably, the sensor module 322 includes an optical nitrogen sensor and a microprocessing unit connected to the optical nitrogen sensor signal, and the microprocessing unit is used to send the nitrogen content detected in real time by the optical nitrogen sensor to the evaluation module.

[0048] Further preferably, a filter screen 417 and a positioning member 416 are provided on the opening 414. The filter screen 417 is made of soft silicone, which has good flexibility and elasticity and can adapt to the deformation requirements of the water sampling head 4 in different water depths and environments. Soft silicone also has excellent corrosion resistance and wear resistance, and can maintain stable performance during long-term water sampling. Positioning member 416 is used to fix the position of the filter screen 417, and can be used, for example, with screws, removable clips, etc.

[0049] In this embodiment, the quantitative assessment model includes a first function and a second function. The nitrogen content is input into the first function to obtain the ecological sensitivity index (ESI), and the ecological sensitivity index (ESI) is then input into the second function to obtain the quantitative assessment value (EVA), which is used to characterize the impact of changes in nitrogen content on the ecological service value. The formulas of the first function and the second function are as follows:

[0050] ESI=a*ln(N+1)+b

[0051] EVA=c*ESI d +e

[0052] Where a is the ecosystem's sensitivity to changes in nitrogen, determined through ecological research experiments or historical data analysis. The sensitivity coefficient a can be obtained by observing the ecosystem's responses to key ecological indicators, such as algal blooms, water quality changes, and biodiversity, under varying nitrogen concentration gradients. Regression analysis and other methods can be used to fit the relationship between nitrogen concentration and ecological responses, thereby determining the sensitivity coefficient a. b is the baseline ecological sensitivity index (ESI) at zero nitrogen. Typically, under theoretical or experimental conditions, the nitrogen concentration is set to an extremely low or zero value, and the ecosystem state at this point is measured, using this baseline to establish the baseline b. This can be achieved by comparing the ecological responses under different nitrogen concentration gradients and selecting the stable value at the lowest or near-zero concentration as the baseline. N is the nitrogen content, while c, d, and e are the assessment coefficient, sensitivity index, and baseline value, respectively. The assessment coefficient c reflects the impact of changes in the ESI on the EVA and requires interdisciplinary approaches such as economics and ecology. The value of c can be determined by analyzing the changing trends in the value of ecological services under different ESIs based on historical data and using regression analysis and other methods. The sensitivity index d is used to adjust the weight or impact of the ESI in the EVA calculation. Its specific value depends on the characteristics of the ecosystem and the assessment objectives. Its acquisition requires the integration of ecological expertise, determined through model simulations and expert scoring. The baseline value, e, represents the baseline level of the lake's ecological service value, either in the absence of nitrogen pollution or at a specific nitrogen concentration. This can be determined based on historical data, ecosystem service value assessment models, or expert evaluation.

[0053] As can be understood, this quantitative assessment model systematically and scientifically evaluates the specific impact of changes in nitrogen content in lakes and reservoirs on the ecological service value (EVA) by integrating the first and second functions. Specifically, the Ecological Sensitivity Index (ESI) is quantified: using the first function, combined with the ecosystem's sensitivity coefficient to nitrogen changes (a) and the baseline Ecological Sensitivity Index (ESI) at zero nitrogen content (b), the sensitivity of the ecosystem to different nitrogen concentration levels (ESI) is accurately calculated. This index directly reflects the intensity of the ecosystem's response to nitrogen pollution. Calculation of the Quantified Ecological Service Value (EVA): Using the second function, the ESI is used as one of the inputs, combined with the assessment coefficient (c), the sensitivity index (d), and the baseline value (e), to comprehensively assess changes in the ecological service value of lakes and reservoirs. This step not only considers the impact of nitrogen pollution on ecological sensitivity but also further converts this impact into a quantifiable economic value, providing an intuitive and scientific basis for decision makers.

[0054] Example 2

[0055] Based on Example 1, this example proposes a method for evaluating the impact of nitrogen content in lakes and reservoirs on ecological service value. The method is implemented based on the above-mentioned evaluation system and includes:

[0056] S1. Place the water sampling head 4 at different depths of the water body to be tested through the winding member 1 and the pull rope 2 for sampling and detection. When the water pressure meets the preset range corresponding to the sampling depth, the pressure regulating valve 422 and the solenoid valve 420 are opened synchronously;

[0057] S2. Sampling the water to be tested through the opening 414 on at least one water sampling head 4, so that the water to be tested is transported to the sensor module 322 along the liquid path;

[0058] S3, starting the sensor module 322 to measure the nitrogen content of the water sample and transmitting the nitrogen content to the evaluation module;

[0059] S4. The assessment module inputs the nitrogen content into a pre-built quantitative assessment model and outputs a quantitative assessment value to characterize the impact of changes in nitrogen content on the value of ecological services.

[0060] It is obvious to those skilled in the art that the embodiments of the present invention are not limited to the details of the above-mentioned exemplary embodiments, and that the embodiments of the present invention can be implemented in other specific forms without departing from the spirit or essential features of the embodiments of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the embodiments of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the embodiments of the present invention. Any figure marks in the claims should not be regarded as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units, modules or devices stated in the system, device or terminal claims may also be implemented by the same unit, module or device through software or hardware. Words such as first and second are used to indicate names and do not indicate any particular order.

[0061] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A system for evaluating the impact of nitrogen content in lakes and reservoirs on ecological service value, characterized in that: The invention comprises a measuring component (3) for measuring the nitrogen content of a water sample; and at least two water sampling heads (4) forming an integral structure with the measuring component (3), wherein the water sampling head (4) comprises an opening (414) occupying at least half the width of a sampling plane of the water sampling head (4); and the measuring component (3) comprises a sensor module (322) located on a liquid path of the water sampling head (4) and a temperature control pipe for controlling the temperature of the water to be measured on the liquid path; The evaluation system further includes an evaluation module, which inputs the nitrogen content into a pre-built quantitative evaluation model and outputs a quantitative evaluation value to characterize the impact of changes in nitrogen content on ecological service value; The sensor module (322) comprises an optical nitrogen sensor and a microprocessing unit connected to the optical nitrogen sensor signal, wherein the microprocessing unit is used to send the nitrogen content detected in real time by the optical nitrogen sensor to the evaluation module; The water sampling head (4) comprises an upper collecting tube (411) in communication with the interior of the measuring component (3), and a sampling end (412) located at the lower end of the upper collecting tube (411), at least one opening (414) is provided on the side wall of the sampling end (412), a collecting channel (418) in communication with the opening (414) is provided inside the sampling end (412), and a temperature sensor (419) is provided at the lower end of the collecting channel (418); A flow channel (413) for connecting the temperature control pipe and the collection channel (418) is provided in the upper collecting cylinder (411), and an interface member (423) is provided at the lower end of the flow channel (413); A solenoid valve (420) is provided on the communication path between the opening (414) and the collecting channel (418); a branch channel (421) is provided on the path between the opening (414) and the solenoid valve (420); the end of the branch channel (421) is communicated with the side of the interface member (423), and a pressure regulating valve (422) is provided at the communication point; The pressure regulating valve (422) is used to compare the water pressure of the water body in the branch channel (421) with the preset sampling depth when the water sampling head (4) is at different depths. When the water pressure meets the preset range corresponding to the sampling depth, the pressure regulating valve (422) and the solenoid valve (420) are opened synchronously; The measuring component (3) includes a first chamber (31) and a second chamber (32), wherein the first chamber (31) is communicated with the upper collecting cylinder (411), and the temperature control pipe comprises a U-shaped conduit (312) provided in the first chamber (31) and a temperature control component (313) provided thereon, and the second chamber (32) is provided with a water pump 2 (321) communicated with one end of the U-shaped conduit (312), the sensor module (322) is located on the water pumping path of the water pump 2 (321), and a temperature measuring component (323) is also provided on the water pumping path, and the other end of the U-shaped conduit (312) faces the upper end of the first chamber (31) and is located at two-thirds of the liquid level in the first chamber (31).

2. The system for evaluating the impact of nitrogen content in lakes and reservoirs on ecological service value according to claim 1, characterized in that: The sensor module (322) is arranged inside the measuring component (3), and the measuring component (3) and the water sampling head (4) are placed at different depths of the water body to be measured via a reel (1) and a pull rope (2) for sampling and detection.

3. The system for evaluating the impact of nitrogen content in lakes and reservoirs on ecological service value according to claim 1, characterized in that: The quantitative assessment model includes a first function and a second function, wherein the nitrogen content is input into the first function to obtain the ecological sensitivity index (ESI), and then the ecological sensitivity index (ESI) is input into the second function to obtain the quantitative assessment value (EVA), which is used to characterize the impact of changes in nitrogen content on ecological service value. The formulas of the first function and the second function are as follows: ； Among them, a is the sensitivity coefficient of the ecosystem to changes in nitrogen, b is the ecological sensitivity index baseline when the nitrogen content is zero, N is the nitrogen content, c, d and e are the assessment coefficient, sensitivity index and benchmark value respectively.

4. A method for evaluating the impact of nitrogen content in lakes and reservoirs on ecological service value, characterized in that: Based on the implementation of the evaluation system according to any one of claims 1 to 3, the method includes: S1. The water sampling head (4) is placed at different depths of the water body to be tested via the reel (1) and the pull rope (2) for sampling and testing. When the water pressure meets the preset range corresponding to the sampling depth, the pressure regulating valve (422) and the solenoid valve (420) are opened synchronously; S2, sampling the water body to be tested through the opening (414) on at least one of the water body sampling heads (4), so that the water body to be tested is transported to the sensor module (322) along the liquid path; S3, starting the sensor module (322) to measure the nitrogen content of the water sample, and transmitting the nitrogen content to the evaluation module; S4. The assessment module inputs the nitrogen content into a pre-built quantitative assessment model and outputs a quantitative assessment value to characterize the impact of changes in nitrogen content on ecological service value.

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