A method and system for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication

Abstract

The invention discloses a method and system for calculating the threshold value of nitrogen and phosphorus nutrients for preventing and controlling seawater eutrophication, which relates to the technical field of ecological environment detection, including: inputting the red tide intensity factor after gridding of the sea area into the red tide intensity kernel density model, obtaining the red tide intensity kernel density of each grid in the sea area; judging the red tide generation and disappearance area and the non-red tide generation and disappearance area according to the red tide intensity kernel density; obtaining the grid distribution of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the non-red tide generation and disappearance area; using the t-test method and the effect size statistical analysis method to obtain the difference, and determine whether there is a seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold when the red tide occurs; inputting the nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area into the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold model, and obtaining the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold. The invention can accurately obtain the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold.

Description

Technical Field

[0001] The present invention relates to the technical field of ecological environment detection, and in particular to a method and system for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication. Background Art

[0002] As the amount of land-based nitrogen, phosphorus and other pollutants discharged into the sea due to the development of global economic centers continues to increase, the ecological safety risk of offshore eutrophication has generally become a prominent issue of global marine ecological environmental safety risks. The ecological safety risk of offshore eutrophication is not only manifested in the primary symptoms of eutrophication such as a substantial increase in phytoplankton biomass, but also in the secondary symptoms of eutrophication such as red tides, lack of dissolved oxygen, loss of aquatic vegetation and benthic animals. The ecological safety risk effect of offshore eutrophication is closely related to the concentration of dissolved nitrogen and phosphorus nutrients and the ratio of the two. The nitrogen and phosphorus nutrient concentration threshold of marine eutrophication refers to the critical value of nitrogen and phosphorus nutrient concentration under the condition that the ecological environment of the target sea area remains healthy. Therefore, the accurate measurement of the nitrogen and phosphorus nutrient threshold for offshore eutrophication prevention and control is a key scientific support for my country to carry out offshore eutrophication prevention and control actions.

[0003] In the prior art, method 1 usually selects appropriate quantile concentrations as the nitrogen and phosphorus nutrient thresholds for seawater eutrophication prevention and control based on the eutrophication status of the sea area and the distribution of nitrogen and phosphorus nutrient concentrations. Method 2 first selects the target state element, such as chlorophyll a (Chl-a), and determines the limit of the state element, then constructs the response relationship between the state element and the nutrient, and determines the nitrogen and phosphorus nutrient thresholds for seawater eutrophication prevention and control based on the limit of the state element. The methods for calculating the nitrogen and phosphorus nutrient concentration thresholds for offshore eutrophication prevention and control mainly include the reference state method, the pressure-state response method, and the model method.

[0004] However, in the above method, when using the nitrogen and phosphorus nutrient concentrations of marine eutrophication, it is not determined whether it is directly related to the occurrence of seawater eutrophication symptoms (such as the occurrence of red tide disasters, their temporal and spatial distribution and their intensity). As a result, this method usually performs threshold calculations in the entire sea area, and cannot achieve statistical calculations of thresholds in key sea areas for eutrophication prevention and control. The calculation results of the nitrogen and phosphorus nutrient thresholds for seawater eutrophication prevention and control are not accurate. Summary of the invention

[0005] The embodiment of the present invention provides a method and system for calculating nitrogen and phosphorus nutrient thresholds for seawater eutrophication prevention and control, which can solve the problem in the prior art that the nitrogen and phosphorus nutrient thresholds for seawater eutrophication prevention and control cannot be accurately obtained.

[0006] The embodiment of the present invention provides a method for calculating the threshold value of nitrogen and phosphorus nutrients for preventing and controlling eutrophication of seawater, comprising the following steps: gridding a sea area, and obtaining a red tide intensity factor representing the duration and distribution area of ​​a red tide in each grid; inputting the red tide intensity factor of each grid into a red tide intensity kernel density model used to describe the density of the intensity of red tide occurrence in a unit area, and obtaining the red tide intensity kernel density of each grid in the sea area; adding the red tide intensity kernel densities of all grids to obtain a total value; sorting the values ​​of the red tide intensity kernel densities of all grids from large to small, and summing the maximum value in the sorted result and the second-ranked value to obtain a cumulative value; selecting the maximum value from the values ​​that have not been summed in the sorted result, summing the selected maximum value and the cumulative value to obtain a new cumulative value, and summing the new cumulative value with the The new maximum values ​​selected from the values ​​that have not been summed in the sorting results are summed until the summed result reaches 90% of the total value; based on the multiple red tide intensity kernel densities used for the summation, the grids used when obtaining the multiple red tide intensity kernel densities are selected; wherein the sea area corresponding to the selected grid is used as the red tide generation and disappearance zone, and the sea area outside the red tide generation and disappearance zone is used as the non-red tide generation and disappearance zone; the grid distribution of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zone and the non-red tide generation and disappearance zone is obtained; based on the grid distribution, the difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zone and the non-red tide generation and disappearance zone is obtained; if the difference exists, the nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zone are input into the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold calculation model to obtain the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold.

[0007] Furthermore, the red tide intensity factor The derivation formula is:

[0008]

[0009] Among them, A represents the distribution area of ​​red tide, and T represents the duration of red tide.

[0010] Furthermore, the step of obtaining the difference in the concentration of nitrogen and phosphorus nutrients in the red tide generation and disappearance area and the non-red tide generation and disappearance area comprises: obtaining the t value and p value of the concentration of nitrogen and phosphorus nutrients in the red tide generation and disappearance area and the non-red tide generation and disappearance area respectively according to the t-test method;

[0011] The formula for the t-test method is:

[0012]

[0013] in, express Statistics; and They represent the average values ​​of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas and the non-red tide generation and disappearance areas respectively; It represents the weighted average of the variance of nitrogen and phosphorus nutrient concentrations in the red tide breeding and non-red ... and Represent the sample sizes of the two samples respectively; find the corresponding p-value according to the t distribution table;

[0014] The effect size d in the effect size statistical method is used to quantify the size of the difference and provide auxiliary judgment.

[0015] Furthermore, the step of obtaining the nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication comprises:

[0016] If the t value in the t-test of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zone and the non-red tide generation and disappearance zone is greater than or equal to 0.05 and the p value is less than or equal to 0.05, then there is a difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zone and the non-red tide generation and disappearance zone, and it is judged that there is a nitrogen and phosphorus nutrient threshold for seawater eutrophication prevention and control that can determine whether red tide disasters occur;

[0017] The derivation formula of the calculation model of nitrogen and phosphorus nutrient threshold for seawater eutrophication prevention and control is:

[0018]

[0019] in, The Kriging grid values ​​of dissolved inorganic nitrogen nutrient concentration DIN and phosphate concentration PO4-P in the water body near the occurrence of red tide, n represents the number of Kriging grids, k represents the nutrient type, and subscript Represents the longitude and latitude of the kriging grid points.

[0020] Furthermore, the red tide cumulative scale density model The derivation formula is:

[0021]

[0022] in, is the weight of the i-th grid data point, which is obtained according to the area of ​​each red tide occurrence; n is the number of grid sample points; K is the kernel function, h is the bandwidth parameter, d(x,xi) is the distance from the grid sample point x to the grid observation point x i distance.

[0023] The embodiment of the present invention provides a system for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication, including:

[0024] The data acquisition module is used to grid the sea area and obtain the red tide intensity factor representing the duration and distribution area of ​​the red tide in each grid; the regional judgment module is used to input the red tide intensity factor of each grid into the red tide intensity kernel density model used to describe the density of the red tide occurrence intensity per unit area, and obtain the red tide intensity kernel density of each grid in the sea area; the red tide intensity kernel densities of all grids are added to obtain a total value; the values ​​of the red tide intensity kernel density of all grids are sorted from large to small, and the maximum value in the sorted result and the second value in the sorted result are summed to obtain a cumulative value; the maximum value is selected from the values ​​that are not summed in the sorted result, the selected maximum value is summed with the cumulative value to obtain a new cumulative value, and the new cumulative value is selected from the values ​​that are not summed in the sorted result. The new maximum values ​​obtained are summed until the summed result reaches 90% of the total value; according to the multiple red tide intensity kernel densities used for the summation, the grids used for obtaining the multiple red tide intensity kernel densities are selected; wherein the sea area corresponding to the selected grid is used as the red tide generation and disappearance zone, and the sea area outside the red tide generation and disappearance zone is used as the non-red tide generation and disappearance zone; the threshold acquisition module is used to obtain the grid distribution of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zone and the non-red tide generation and disappearance zone; according to the grid distribution, the difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zone and the non-red tide generation and disappearance zone is obtained; if the difference exists, the nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zone are input into the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold calculation model to obtain the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold.

[0025] An embodiment of the present invention provides a computer device, including: a memory and a processor; the memory stores a computer program, and the processor implements the above-mentioned method for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication when executing the computer program.

[0026] An embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned method for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication is implemented.

[0027] The embodiment of the present invention provides a method and system for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication. Compared with the prior art, the beneficial effects thereof are as follows:

[0028] The red tide generation and disappearance zones and non-red tide generation and disappearance zones in the sea area are first determined through the red tide intensity kernel density model, and the difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zones and non-red tide generation and disappearance zones is obtained according to the grid distribution. If the difference exists, it is determined that the occurrence of red tide in the red tide generation and disappearance zones is related to the nitrogen and phosphorus nutrient concentrations. This can explain that the nitrogen and phosphorus nutrient concentrations of marine eutrophication are the determining factors of seawater eutrophication. Then, the nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance zones are input into the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold calculation model, and the nitrogen and phosphorus nutrient thresholds for seawater eutrophication prevention and control are accurately obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A flowchart provided for an embodiment of the present invention;

[0030] Figure 2 A concentration diagram of dissolved inorganic nitrogen in a red tide-occurring area during a red tide-occurring period (spring and summer) provided by an embodiment of the present invention;

[0031] Figure 3 A concentration diagram of dissolved inorganic nitrogen during a red tide period in a non-red tide area provided by an embodiment of the present invention (spring and summer);

[0032] Figure 4 A diagram of dissolved inorganic phosphorus concentration during the red tide period in the red tide occurrence area provided by an embodiment of the present invention (spring and summer);

[0033] Figure 5 A dissolved inorganic phosphorus concentration diagram (spring and summer) during the red tide period in a non-red tide occurrence area provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0035] See also Figure 1 The embodiment of the present invention provides a method for calculating the nitrogen and phosphorus nutrient threshold for preventing and controlling seawater eutrophication, comprising the following steps:

[0036] Step 1: Grid the sea area and obtain the red tide intensity factor representing the duration and distribution area of ​​red tide in each grid.

[0037] Step 2: Input the red tide intensity factor of each grid into the red tide intensity kernel density model used to describe the density of the intensity of red tide occurrence per unit area, and obtain the red tide intensity kernel density of each grid in the sea area; add the red tide intensity kernel densities of all grids to obtain the total value; sort the values ​​of the red tide intensity kernel density of all grids from large to small, and sum the maximum value in the sorting result and the second value in the sorting result to obtain the cumulative value; select the maximum value from the values ​​that have not been summed in the sorting result, sum the selected maximum value with the cumulative value to obtain a new cumulative value, and sum the new cumulative value with the new maximum value selected from the values ​​that have not been summed in the sorting result, until the sum reaches 90% of the total value; according to the multiple red tide intensity kernel densities used for the summation, select multiple grids used for obtaining the red tide intensity kernel densities; wherein, the sea area corresponding to the selected grid is used as the red tide occurrence and disappearance zone, and the sea area outside the red tide occurrence and disappearance zone is used as the non-red tide occurrence and disappearance zone.

[0038] Step 3: Obtain the grid distribution of nitrogen and phosphorus nutrient concentrations in red tide generating and disappearing areas and non-red tide generating and disappearing areas; based on the grid distribution, obtain the difference in nitrogen and phosphorus nutrient concentrations in red tide generating and disappearing areas and non-red tide generating and disappearing areas; if there is a difference, input the nitrogen and phosphorus nutrient concentrations in the red tide generating and disappearing areas into the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold calculation model to obtain the seawater eutrophication prevention and control nitrogen and phosphorus nutrient thresholds.

[0039] 1. Definition of key sea areas for offshore eutrophication prevention and control.

[0040] Key areas for offshore eutrophication prevention and control can be defined by selecting areas with serious eutrophication symptoms. Therefore, considering that eutrophication is high in my country's offshore and its symptoms and distribution are easy to monitor, offshore red tide occurrence is selected as an indicator factor to define key areas for offshore eutrophication prevention and control.

[0041] The degree of harm caused by offshore red tides depends not only on the area where red tides occur, but also on the duration of red tides. Based on the collection and summary of monitoring data on the sea area, location, distribution area, duration, etc. of red tide disasters, the kernel density method is used to analyze and define the scope of offshore red tide disasters through Kriging grid data of the cumulative scale of red tides. It can be expressed as:

[0042] (1)

[0043] Among them, A represents the red tide distribution area, and T represents the duration of the red tide. In this way, the kernel density of the red tide intensity can be expressed as:

[0044] (2)

[0045] in, is the weight of the ith data point (calculated here based on the area of ​​each red tide occurrence), n is the number of sample points, K(⋅) is the kernel function, h is the bandwidth parameter, which is used to control the width of the kernel function. i ) is the distance from the sample point x to the observation point x i The distance. The sea area corresponding to the red tide intensity kernel density whose previous cumulative total accounts for the top 90% is selected as the red tide generation and disappearance zone, and the sea area outside the red tide generation and disappearance zone is selected as the non-red tide generation and disappearance zone. The red tide intensity kernel density whose previous cumulative total accounts for the top 90% is specifically explained as follows: sort the values ​​of the red tide intensity kernel density of all grids from large to small, and sum the maximum value in the sorting result and the second value in the sorting to obtain the cumulative value; select the maximum value from the values ​​that are not summed in the sorting result, sum the selected maximum value and the cumulative value to obtain a new cumulative value, and sum the new cumulative value with the new maximum value selected from the values ​​that are not summed in the sorting result, until the sum reaches 90% of the total value.

[0046] 2. Standardization of monitoring data on dissolved inorganic nitrogen and phosphorus nutrient concentrations.

[0047] This study first divides the research area into several grid cells of equal size. Then the Kriging spatial interpolation method is used to statistically analyze the planar distribution of the marine survey data. The main principles are:

[0048] (1) Determination of semivariogram .

[0049] The semivariogram describes the spatial autocorrelation of the variable, that is, the degree to which the variable values ​​change with the increase of spatial distance h. Considering that the monitoring data is continuous data, the semivariogram is selected as exponential. It is usually expressed as:

[0050] (3)

[0051] Where h is the spatial distance, n is the number of known data points, is the observed value of the ith data point, is the observed value of the point that is h away from the ith data point.

[0052] (2) Kriging interpolation model.

[0053] The Kriging interpolation model assumes that the value of the unknown location can be estimated by the weighted average of the known data points, with the weights determined by the spatial relationship and autocorrelation between the interpolation points and the known points. , ) It can be expressed as a weighted average:

[0054] (4)

[0055] in, is the weight between the unknown location and the known data point i, which is usually determined by the Kriging interpolation model and spatial distance.

[0056] (3) Determine the weight.

[0057] Weight Usually by minimizing the estimated Observed values ​​with known data points to determine the error between them.

[0058] Finally, the kriging equation is solved to determine the interpolated estimate for the unknown location, based on the spatial locations and observed values ​​of the known data points and the chosen semivariogram. and the corresponding weights Solve the Kriging equation to obtain the best interpolation result.

[0059] For each grid cell, the Kriging interpolation method is used to estimate the average value of all interpolation data points in the grid cell, and the average value of each grid cell is used as the value of the grid cell to generate a spatial distribution map of the grid average results. These grid values ​​​​precisely reflect the spatial distribution of monitoring data in the application sea area, and are also convenient for geostatistical analysis of data.

[0060] 3. Accurately calculate the threshold value of dissolved inorganic nitrogen and phosphorus nutrient concentration.

[0061] (1) Calculation of the difference in nitrogen and phosphorus nutrient concentrations between red tide-prone and non-red tide-prone areas.

[0062] In the process of screening data from red tide areas and non-red tide areas, the nitrogen and phosphorus nutrient concentration monitoring data were divided into different areas according to the definition of the red tide zone, and the nitrogen and phosphorus nutrient concentration data in the red tide zone and non-red tide zone were further analyzed for differences. This process aims to clarify the temporal and spatial differences in nitrogen and phosphorus nutrient concentrations in red tide zones and non-red tide zones, and to demonstrate that there are significant differences in nitrogen and phosphorus nutrient concentrations in red tide zones and non-red tide zones, providing a scientific basis for the subsequent precise calculation of nitrogen and phosphorus nutrient concentration thresholds.

[0063] Two main methods were used to determine the differences in dissolved inorganic nitrogen and phosphorus concentrations between red tide and non-red tide zones: t-test and effect size analysis. These two methods combined allowed for a comprehensive statistical analysis of the differences between the two sets of data.

[0064] The t-test method is widely used to compare the mean differences between data. In this article, it is mainly used to qualitatively determine whether the difference between two groups of data is significant.

[0065] The formula for the t-test method is:

[0066]

[0067] in, express Statistics; and They represent the average values ​​of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas and the non-red tide generation and disappearance areas respectively; It represents the weighted average of the variance of nitrogen and phosphorus nutrient concentrations in the red tide breeding and non-red ... and Represent the sample sizes of the two samples respectively; the corresponding p-values ​​are found according to the t distribution table.

[0068] Effect size is an indicator used to measure the degree of difference between two groups of data. Its calculation formula is:

[0069] (5)

[0070] Where d is the effect size (Cohen's d); and are the means of the two groups, is the standard deviation of the two groups combined.

[0071] (6)

[0072] in, and is the sample size for both groups; and is the sample standard deviation of the two groups.

[0073] The t-test and effect size statistical analysis methods were used to analyze the differences between the red tide generation and disappearance areas and the non-generation and disappearance areas; the red tide occurrence period and the non-occurrence period in the red tide occurrence area. Based on the difference results and the degree of difference, it was analyzed whether there is a threshold for the occurrence of red tide in a certain sea area.

[0074] (2) Calculation of nitrogen and phosphorus nutrient thresholds for the prevention and control of seawater eutrophication.

[0075] Nitrogen and phosphorus nutrient thresholds for seawater eutrophication prevention and control ( ) refers to the average concentration of nitrogen and phosphorus nutrients in the red tide generation and disappearance area when the red tide is approaching. The result can be expressed as:

[0076] (7)

[0077] in, The Kriging grid values ​​of the dissolved inorganic nitrogen nutrient concentration DIN (Dissolved Inorganic Nitrogen) and the phosphate as phosphorus concentration PO4-P (Phosphate as Phosphorus) in the water body near the occurrence of red tide, n represents the number of Kriging grids, subscript k represents the nutrient type, and subscript Represents the longitude and latitude of the Kriging grid points.

[0078] The beneficial effects of the present invention also include the following aspects:

[0079] The nitrogen and phosphorus nutrient thresholds for offshore eutrophication control are key bridge parameters for implementing various eutrophication control action plans, and are key environmental targets for guiding the setting and implementation of offshore eutrophication control indicators and control engineering measures. Close integration with eutrophication and its symptoms is a key means of calculating nitrogen and phosphorus nutrient thresholds. However, the current method for calculating nitrogen and phosphorus nutrient thresholds for offshore eutrophication control lacks association with the occurrence of eutrophication symptoms and their spatiotemporal characteristics, resulting in the deviation of nitrogen and phosphorus nutrient threshold calculations from offshore eutrophication conditions, making it difficult to efficiently guide the implementation of offshore eutrophication control action plans. This method uses the location and intensity of offshore red tides as indicators to identify offshore red tide occurrence areas, define key offshore eutrophication control areas, compare nitrogen and phosphorus nutrient concentrations in red tide occurrence areas with those in non-red tide occurrence areas, analyze the spatiotemporal differences in nitrogen and phosphorus nutrient concentrations in red tide occurrence areas, and then accurately calculate the nitrogen and phosphorus nutrient thresholds for offshore eutrophication control based on nitrogen and phosphorus nutrient concentration monitoring data in red tide occurrence areas.

[0080] The key point is that when calculating the nitrogen and phosphorus nutrient concentration thresholds for near-shore eutrophication prevention and control, the cumulative kernel density method is applied through the historical red tide occurrence areas, scales and durations to define the sea areas where red tides occur. By comparing the nitrogen and phosphorus nutrient concentrations in the sea areas where red tides occur and those in non-red tide sea areas, the nitrogen and phosphorus nutrient concentration thresholds for near-shore eutrophication prevention and control are determined, which closely links near-shore eutrophication prevention and control with eutrophication symptoms and improves the accuracy of the nitrogen and phosphorus nutrient concentration thresholds.

[0081] The embodiment of the present invention provides a system for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication, including:

[0082] The data acquisition module is used to grid the sea area and obtain the red tide intensity factor representing the duration and distribution area of ​​the red tide in each grid. The regional judgment module is used to input the red tide intensity factor of each grid into the red tide intensity kernel density model used to describe the density of the red tide occurrence intensity per unit area, and obtain the red tide intensity kernel density of each grid in the sea area; add the red tide intensity kernel densities of all grids to obtain the total value; sort the values ​​of the red tide intensity kernel density of all grids from large to small, and sum the maximum value in the sorting result with the second value in the sorting result to obtain the cumulative value; select the maximum value from the values ​​that are not summed in the sorting result, sum the selected maximum value with the cumulative value to obtain a new cumulative value, and sum the new cumulative value with the new maximum value selected from the values ​​that are not summed in the sorting result until the summed result reaches 90% of the total value; select multiple grids used for the acquisition of the red tide intensity kernel densities according to the multiple red tide intensity kernel densities used for the summation; wherein, the sea area interval corresponding to the selected grid is used as the red tide generation and disappearance zone, and the sea area interval outside the red tide generation and disappearance zone is used as the non-red tide generation and disappearance zone. The threshold acquisition module is used to obtain the grid distribution of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the non-red tide generation and disappearance area; according to the grid distribution, the difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the non-red tide generation and disappearance area is obtained; if the difference exists, the nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area are input into the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold calculation model to obtain the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold.

[0083] An embodiment of the present invention provides a computer device, including: a memory and a processor; the memory stores a computer program, and when the processor executes the computer program, the steps of a method for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication are implemented.

[0084] An embodiment of the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of a method for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication are implemented.

[0085] A specific embodiment is as follows:

[0086] (1) Definition of key sea areas for eutrophication control in a certain sea area.

[0087] According to the monitoring and statistical results of the distribution area and duration of red tide disasters in a certain sea area since 1989, the kernel density analysis method was used to analyze the cumulative scale of red tide disasters in a certain sea area. The results show that red tide disasters in a certain sea area mainly occur in Bay A, the sea area adjacent to Island B, Bay C, the sea area near the mouth of the D River, Bay E, Sea Area F and the sea area of ​​the G Strait, and the distribution area of ​​red tide accounts for about 35% of the total area of ​​the sea area. The comparative analysis results show that the cumulative scale of red tides in different sea areas generally decreases in the order of the sea area adjacent to Island B (56.1%), Bay C (31.3%), Bay E (5.1%), Bay A (4.3%), the sea area near the mouth of the D River (2.5%), Bay F (0.4%) and the sea area of ​​the G Strait (0.3%). Since the cumulative scale of red tides in the central bay and G Strait is less than 1% in total, and the former and the latter have only occurred 3 and 2 times respectively, the red tide disaster generation and elimination areas in a certain sea area are mainly distributed in five large sea areas: A Bay, the waters adjacent to B Island, C Bay, the waters near the D estuary and E Bay.

[0088] (2) Analysis on the difference of dissolved inorganic nitrogen and phosphorus nutrient concentration between red tide occurrence and disappearance areas and non-red tide occurrence and disappearance areas.

[0089] The results of difference analysis showed that the concentrations of dissolved inorganic nitrogen and phosphorus in red tide in a certain sea area were significantly different not only between the red tide generation and disappearance zone and the non-red tide generation and disappearance zone, but also between the red tide period and the non-red tide period in the red tide generation and disappearance zone.

[0090] Further analysis showed that during the red tide period in a certain sea area, the dissolved inorganic nitrogen DIN (Dissolved Inorganic Nitrogen) and dissolved inorganic phosphorus DIP (Dissolved Inorganic Phosphorus) may also be significantly different in the red tide generation and disappearance zones of A Bay (LDB), B Island Neighboring Sea (QHD), C Bay (BHB), D River Estuary (HHK) and E Bay (LZB). Therefore, the DIN and DIP concentration thresholds for eutrophication control in a certain sea area should be the DIN and DIP concentration thresholds during the red tide period in each red tide generation and disappearance zone (Formula 7).

[0091] Table 1 Overall difference analysis of DIN and DIP during red tide period and non-red tide period in the red tide area.

[0092]

[0093] Note: "*" indicates significant difference at p<0.05 level, "**" indicates significant difference at p<0.01 level. Same below.

[0094] Table 2 Analysis of differences among different sea areas during the red tide occurrence period in the DIN red tide area.

[0095]

[0096] Table 3 Analysis of differences among different sea areas during the red tide occurrence period in the DIP red tide area.

[0097]

[0098] (3) Thresholds of dissolved inorganic nitrogen and phosphorus nutrients for preventing and controlling coastal eutrophication.

[0099] The calculation results using formula (7) show that for the five major red tide occurrence and disappearance areas in a certain sea area since 1989, the average DIN concentrations in summer and autumn near the occurrence of red tides are 0.23 mg / L and 0.26 mg / L, respectively, with the minimums of 0.02 mg / L and 0.03 mg / L, and the maximums of 0.92 mg / L and 0.98 mg / L, respectively. The average PO4-P concentrations are 0.04 mg / L and 0.01 mg / L, respectively, with the minimums of 0.001 mg / L and 0.001 mg / L, and the maximums of 0.88 mg / L and 0.26 mg / L, respectively. Figure 2~Figure 5 shown.

[0100] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication, characterized in that: The following steps are involved: Grid the sea area and obtain the red tide intensity factor representing the duration and distribution area of ​​red tide in each grid; The red tide intensity factor of each grid is input into the red tide intensity kernel density model used to describe the density of the red tide occurrence intensity per unit area, and the red tide intensity kernel density of each grid in the sea area is obtained; The red tide intensity kernel density of all grids is added to obtain a total value; the values ​​of the red tide intensity kernel density of all grids are sorted from large to small, and the maximum value in the sorting result and the second value in the sorting result are summed to obtain a cumulative value; the maximum value is selected from the values ​​that have not been summed in the sorting result, and the selected maximum value is summed with the cumulative value to obtain a new cumulative value, and the new cumulative value is summed with the new maximum value selected from the values ​​that have not been summed in the sorting result, until the summed result reaches 90% of the total value; According to the multiple red tide intensity kernel densities used for summing, the grids used for obtaining the multiple red tide intensity kernel densities are selected; wherein the sea area corresponding to the selected grid is used as the red tide generation and disappearance zone, and the sea area outside the red tide generation and disappearance zone is used as the non-red tide generation and disappearance zone; Obtain the grid distribution of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas and the non-red tide generation and disappearance areas; obtain the difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas and the non-red tide generation and disappearance areas based on the grid distribution; if there is a difference, input the nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas into the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold calculation model to obtain the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold; The nitrogen and phosphorus nutrient thresholds for seawater eutrophication prevention and control include: If the t value in the t-test of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas is greater than or equal to 0.05 and the p value is less than or equal to 0.05, then there is a difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas and the non-red tide generation and disappearance areas, and it is determined that there is a nitrogen and phosphorus nutrient threshold for seawater eutrophication prevention and control that can determine whether red tide disasters occur; The derivation formula of the nitrogen and phosphorus nutrient threshold calculation model for seawater eutrophication prevention and control is: in, It represents the nitrogen and phosphorus nutrient threshold for the prevention and control of seawater eutrophication. Cr represents the Kriging grid value of the dissolved inorganic nitrogen nutrient concentration DIN and the phosphate concentration PO4-P in the water body when the red tide is approaching. n represents the number of Kriging grids. k represents the nutrient category. The subscript (x, y) represents the latitude and longitude of the Kriging grid point.

2. A method for calculating nitrogen and phosphorus nutrient thresholds for seawater eutrophication control according to claim 1, characterized in that: The derivation formula of the red tide intensity factor Q is: Q=AT Among them, A represents the distribution area of ​​red tide, and T represents the duration of red tide.

3. A method for calculating nitrogen and phosphorus nutrient thresholds for seawater eutrophication control according to claim 1, characterized in that: The specific steps of obtaining the difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the non-red tide generation and disappearance area include: The t-test method was used to obtain the t-value and p-value of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas and non-red tide generation and disappearance areas respectively; The formula for the t-test method is: Where t represents the t statistic; x1 and x2 represent the average values ​​of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance areas and non-red tide generation and disappearance areas, respectively; s 2 It represents the weighted average of the variance of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the non-red tide generation and disappearance area; n1 and n2 represent the sample sizes of the two samples respectively; the corresponding p value is found according to the t distribution table; The effect size d in the effect size statistical method is used to quantify the size of the difference and provide auxiliary judgment.

4. A method for calculating nitrogen and phosphorus nutrient thresholds for seawater eutrophication control according to claim 1, characterized in that: The derivation formula of the red tide intensity kernel density model Density is: Among them, ω i is the weight of the i-th grid data point, which is obtained according to the area of ​​each red tide occurrence; n is the number of grid sample points; K is the kernel function, h is the bandwidth parameter, and d(x,x i ) is the distance from the grid sample point x to the grid observation point x i distance.

5. A system for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication, characterized in that: include: The data acquisition module is used to grid the sea area and obtain the red tide intensity factor representing the duration and distribution area of ​​the red tide in each grid; The regional judgment module is used to input the red tide intensity factor of each grid into the red tide intensity kernel density model used to describe the density of the red tide occurrence intensity within a unit area, and obtain the red tide intensity kernel density of each grid in the sea area; add the red tide intensity kernel densities of all grids to obtain a total value; sort the values ​​of the red tide intensity kernel density of all grids from large to small, and sum the maximum value in the sorting result and the second value in the sorting result to obtain a cumulative value; select the maximum value from the values ​​that have not been summed in the sorting result, sum the selected maximum value with the cumulative value to obtain a new cumulative value, and sum the new cumulative value with the new maximum value selected from the values ​​that have not been summed in the sorting result until the summed result reaches 90% of the total value; select multiple grids used for obtaining the red tide intensity kernel densities according to the multiple red tide intensity kernel densities used for the summation; wherein the sea area interval corresponding to the selected grid is used as the red tide generation and disappearance zone, and the sea area interval outside the red tide generation and disappearance zone is used as the non-red tide generation and disappearance zone; The threshold acquisition module is used to obtain the grid distribution of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the non-red tide generation and disappearance area; according to the grid distribution, the difference of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the non-red tide generation and disappearance area is obtained; if the difference exists, the nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area are input into the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold calculation model to obtain the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold; the seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold includes: if the t value in the t test of nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the p value is less than or equal to 0.05, then there is a difference in nitrogen and phosphorus nutrient concentrations in the red tide generation and disappearance area and the non-red tide generation and disappearance area, and it is determined that there is a seawater eutrophication prevention and control nitrogen and phosphorus nutrient threshold that can define whether a red tide disaster occurs; The derivation formula of the nitrogen and phosphorus nutrient threshold calculation model for seawater eutrophication prevention and control is: in, It represents the nitrogen and phosphorus nutrient threshold for the prevention and control of seawater eutrophication. Cr represents the Kriging grid value of the dissolved inorganic nitrogen nutrient concentration DIN and the phosphate concentration PO4-P in the water body when the red tide is approaching. n represents the number of Kriging grids. k represents the nutrient category. The subscript (x, y) represents the latitude and longitude of the Kriging grid point.

6. A computer device comprising: Memory and processor; The memory stores a computer program, wherein the processor implements a method for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication according to any one of claims 1 to 5 when executing the computer program.

7. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, a method for calculating nitrogen and phosphorus nutrient thresholds for preventing and controlling seawater eutrophication according to any one of claims 1 to 5 is implemented.

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