A method for analyzing the sources of nitrogen pollution in mangroves based on the stable nitrogen isotope composition

Abstract

The present invention discloses a method for analyzing the sources of nitrogen pollution in mangroves based on the stable nitrogen isotope composition, which includes: culturing mangrove plants in the laboratory to ensure that the initial isotope values of each plant are consistent; placing cages in a series of mangroves with nitrogen concentration gradients and planting the mangrove plants into the cages; allowing the mangrove plants to grow in the cages for at least one month to ensure isotope integration of the mangrove plants; collecting mangrove plant samples from the cages multiple times, drying the mangrove plant samples, and grinding them into powders to make aluminum-tin capsules; using a stable isotope ratio mass spectrometer (IRMS) to analyze the δ<supgt;15< / supgt;N isotope ratio of the aluminum-tin capsules; drawing spatial variation diagrams, temporal variation diagrams, and hotspot diagrams based on the δ<supgt;15< / supgt;N isotope ratio; and determining the sources of nitrogen pollution according to the differences in the δ<supgt;15< / supgt;N isotope ratio of the mangrove plants. Through the method of the present invention, accurate judgment of the sources of nitrogen pollution in mangroves can be achieved, and it can also provide directions for environmental governance and environmental protection.

Description

Technical Field

[0001] This application relates to the technical field of environmental pollution prevention and control, and particularly to a method for analyzing the sources of nitrogen pollution in mangroves based on stable nitrogen isotope composition. Background Art

[0002] In recent years, the emission of nitrogen has caused serious damage to aquatic ecosystems. Excessive nitrogen loads can damage the survival, growth, and reproductive capabilities of organisms. At the same time, the eutrophication caused by the increase in nitrogen loads will have numerous chain reactions on ecosystem functions, such as a decrease in dissolved oxygen concentration, a large number of fish deaths, toxic algal blooms, and an increase in turbidity. In some cases, it will also promote the invasion of alien species. Therefore, determining the sources of nitrogen pollution is an important basis for formulating environmental governance plans.

[0003] Currently, the main method for analyzing the sources of nitrogen pollution is to monitor the total nitrogen, ammonia nitrogen, and nitrate content in water bodies. The general steps of this method are as follows: 1. Water sample collection: Collect water samples in the mangrove ecosystem under study. 2. Sample detection: Detect and analyze the water samples. 3. Data analysis: Synthesize the obtained sample data to judge the degree of nitrogen pollution. However, this method is extremely vulnerable to the surrounding environment. For example, rainfall, sewage discharge, and sea tide will all cause the data of the measured water samples to be inaccurate, resulting in large data errors. At the same time, this method can only reflect the nitrogen pollution situation at the moment when the water samples are collected, and cannot reflect the nitrogen pollution situation in this mangrove over a period of time in the past. It lacks scientificity and cannot provide accurate data as a basis for environmental governance. Therefore, there is an urgent need for a new method to make up for these deficiencies. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a method for analyzing the sources of nitrogen pollution in mangroves based on stable nitrogen isotope composition, so as to solve the technical problems in the related art, such as being vulnerable to the environment and resulting in unstable data, only providing nitrogen pollution data in a short period of time, and being unable to reflect the nitrogen pollution situation in mangroves over a period of time in the past, lacking scientificity.

[0005] According to the embodiments of this application, a method for analyzing the sources of nitrogen pollution in mangroves based on stable nitrogen isotope composition is provided, including the following steps:

[0006] Cultivate mangrove plants in the laboratory to ensure that the initial isotope values of each plant are the same;

[0007] Place cages in a series of mangroves with nitrogen concentration gradients and plant the mangrove plants into the cages;

[0008] The mangrove plants grow in the cages for at least one month to ensure isotope integration of the mangrove plants;

[0009] Collect mangrove plant samples from the net cages multiple times, dry the mangrove plant samples, and grind them into powder to make aluminum-tin capsules;

[0010] Use a stable isotope ratio mass spectrometer (IRMS) to analyze the δ 15 N isotope ratio of the aluminum-tin capsules;

[0011] Based on the δ 15 N isotope ratio, draw spatial variation diagrams, temporal variation diagrams, and hotspot diagrams;

[0012] Based on the different δ 15 N isotope ratios of mangrove plants, determine the sources of nitrogen pollution; when the δ 15 N isotope ratio of mangrove plants > +10.00‰, it indicates that the source of nitrogen pollution is urban domestic sewage; when the δ 15 N isotope ratio of mangrove plants is -2‰ to +2‰, it indicates that the source of nitrogen pollution is agricultural synthetic fertilizers; when the δ 15 N isotope ratio of mangrove plants is +2‰ to +10‰, it indicates that it comes from the natural ecological environment not affected by human activities, industrial and agricultural production.

[0013] Preferably, the laboratory culture lasts for 30 - 40 days.

[0014] Preferably, the frequency of collecting mangrove plant samples from the net cages multiple times is 1 - 2 times per month, and the collection continues for one year.

[0015] Preferably, each sampling period is after the ebb tide, that is, at the low tide moment.

[0016] Preferably, each time 10.0 - 15.0 mg of wet weight mangrove plant samples are collected from the net cages.

[0017] Preferably, the drying temperature is 50 - 55°C, and the drying time is 40 - 48 hours.

[0018] The technical solutions provided by the embodiments of the present application may include the following beneficial effects:

[0019] The present application uses stable nitrogen isotopes to measure the analytical method for the sources of nitrogen pollution in mangroves, enabling accurate determination of the sources of nitrogen pollution in mangroves and providing directions for environmental governance and environmental protection. Some deficiencies of the prior art are being easily affected by the surrounding environment, only being able to reflect the short-term pollution situation, and having large errors. The method in the present invention can solve the deficiencies of the traditional method by measuring the nitrogen stable isotopes of mangrove plants, because nitrogen stable isotopes are very stable, and it takes a certain amount of time for mangrove plants to fuse with the isotopes. Therefore, the data measured by the present invention through mangrove plants is stable and reliable, and can explain the nitrogen pollution situation in mangroves on a longer time scale, enabling environmental managers to correctly judge the sources of nitrogen pollution.

[0020] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. Brief Description of the Drawings

[0021] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments in accordance with the present application, and are used together with the specification to explain the principles of the present application.

[0022] Figure 1 is a flowchart of a method for analyzing the sources of nitrogen pollution in mangroves based on the stable nitrogen isotope composition shown according to an exemplary embodiment.

[0023] Figure 2 is a photograph of mangrove plants cultured in the laboratory shown according to an exemplary embodiment.

[0024] Figure 3 is a drawn spatial variation diagram shown according to an exemplary embodiment.

[0025] Figure 4 is a time variation diagram shown according to an exemplary embodiment. Detailed Description of the Embodiments

[0026] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are only examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0027] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms "a", "the", and "said" used in this application and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0028] Figure 1 is a flowchart of a method for analyzing the sources of nitrogen pollution in mangroves based on stable nitrogen isotope composition shown according to an exemplary embodiment, as Figure 1 shown, the method may include the following steps:

[0029] S1: Cultivate mangrove plants in the laboratory to ensure that the initial isotope values of each plant are consistent;

[0030] S2: Place cages in a series of mangroves with nitrogen concentration gradients and plant the mangrove plants into the cages;

[0031] S3: The mangrove plants grow in the cages for at least one month to ensure isotope integration of the mangrove plants;

[0032] S4: Collect mangrove plant samples from the cages multiple times, dry the mangrove plant samples, and grind them into powders to make aluminum-tin capsules;

[0033] S5: Use a stable isotope ratio mass spectrometer (IRMS) to analyze the δ 15 N isotope ratio of the aluminum-tin capsules;

[0034] S6: Draw a contour map to perform spatio-temporal variation analysis on the δ 15 N of mangrove plants, and use ArcGIS 10.5 for the hotspot map;

[0035] S7: Determine the source of nitrogen pollution based on the different δ 15 N isotope ratios of mangrove plants; when the δ 15 N isotope ratio of mangrove plants > +10.00‰, it indicates that the source of nitrogen pollution is urban domestic sewage; when the δ 15 N isotope ratio of mangrove plants is -2‰ to +2‰, it indicates that the source of nitrogen pollution is agricultural synthetic fertilizers; when the δ 15 N isotope ratio of mangrove plants is +2‰ to +10‰, it indicates that it comes from a natural ecological environment not affected by human activities, industrial, and agricultural production.

[0036] As can be seen from the above embodiments, the method of the present application can accurately determine the source of nitrogen pollution in mangroves and provide a treatment direction for environmental managers. For example, when the nitrogen pollution in mangroves comes from urban sewage, the treatment equipment of the sewage treatment plant can be upgraded to reduce the nitrogen content in the discharged water body. At present, the methods for analyzing the source of nitrogen pollution in mangroves are easily affected by the surrounding environment, can only reflect the short-term pollution situation, and have large errors. There is an urgent need for new methods to make up for these deficiencies. The method described in the present application can solve the deficiencies of existing traditional methods.

[0037] In the specific implementation of S1, the mangrove plants are cultivated in the laboratory to ensure that the initial isotope values of each plant are the same;

[0038] Specifically, the mangrove plants are cultivated in the laboratory to grow in the same growth environment to ensure that the initial isotope values of each mangrove plant are the same. In the example, the mangrove plant seeds collected are planted in the pre-prepared cultivation bags and cultivated in the laboratory for 30 - 40 days (such as Figure 2 ).

[0039] In the specific implementation of S2, cages are placed in mangroves with a series of nitrogen concentration gradients, and the mangrove plants are planted into the cages;

[0040] Specifically, cages are placed in mangroves in a series of nitrogen concentration gradients (i.e., marked as C1, C2, C3, C4, C5, C6, C7), such as near cities, formal and informal residential areas, agricultural irrigation areas, and natural locations not affected by human activities, industrial and agricultural production, etc., to ensure the richness and scientificity of the data source. At the same time, the cages are fixed to the underwater cement weights with ropes to prevent the cages from drifting. Then, the mangrove plant seedlings cultivated in the laboratory are planted into the cages. By planting the mangrove plants into the cages, not only can the mangrove plants be well fixed in the monitored mangrove area, but it is also convenient for later collection of mangrove plant samples.

[0041] In the specific implementation of S3, the mangrove plants grow in the cages for one month;

[0042] Specifically, the mangrove plants planted in the cages grow for at least one month to ensure that the mangrove plants have enough time for isotope fusion. At the same time, if it is found that any mangrove plant dies during the growth process, it should be promptly replaced with a mangrove plant cultivated in the laboratory. In addition, the dirt and algae adhering to the cages need to be cleaned 1 - 2 times during their growth period to ensure that the mangrove plants are in full contact with the water body and fully absorb nitrogen.

[0043] In the specific implementation of S4, multiple mangrove plant samples are collected from the cages, and the mangrove plant samples are dried and ground into powder to make aluminum - tin capsules; it can include the following steps:

[0044] S41: The method in this invention can analyze the sources of nitrogen pollution through stable nitrogen isotopes, and can explain the nitrogen pollution status of mangroves on a longer time scale. Therefore, in order to ensure that the obtained data is more accurate and scientific, it is necessary to collect mangrove plant samples from the cages multiple times. Samples of mangrove plants are collected 1 - 2 times per month, and each sampling period is at the low tide moment, and the sampling continues for one year.

[0045] S42: Each time, 10.0 - 15.0 mg of wet weight mangrove plant samples are collected from the cages. The samples are placed in a crucible and dried at 50 - 55 °C for 40 - 48 hours.

[0046] S43: The stable isotope ratio mass spectrometer (IRMS) is a very precise instrument. Therefore, the dried mangrove plant samples need to be ground into powder and made into 12×6 mm aluminum - tin capsules.

[0047] In the specific implementation of S5, a stable isotope ratio mass spectrometer is used to analyze the δ 15 N isotope ratio of the aluminum - tin capsules;

[0048] Specifically, the aluminum - tin capsules containing mangrove plant samples are placed in the DELTAV Advantage isotope ratio mass spectrometer in sequence, and the instrument is started. After the analysis is completed, the δ 15 N isotope ratio corresponding to each sample is recorded.

[0049] In the specific implementation of S6, a contour map is drawn to analyze the spatio - temporal changes of δ 15 N of mangrove plants. The hotspot map uses ArcGIS 10.5; the following steps can be included:

[0050] S61: According to the δ 15 N isotope ratio data obtained from the DELTAV Advantage isotope ratio mass spectrometer, a spatial change map and a time change map ( Figure 3 and Figure 4 ) are drawn. By drawing the δ 15 N spatio - temporal change map, the changes of δ 15 N in each concentration gradient area of the mangroves can be clearly presented. As Figure 3 and Figure 4 shown, the δ 15 N measured is lower the farther away from the mangroves, and at the same time, the δ 15 N isotope ratio within each nitrogen concentration gradient changes little with time and the data is stable.

[0051] S62: Open the ArcGIS 10.5 software, and import the δ 15Inputting the N isotope ratio data into this software enables the creation of a hotspot map. By using ArcGIS 10.5 to create the hotspot map, it is possible to highlight the mangrove areas with severe pollution, allowing environmental managers to carry out targeted treatment with high efficiency and high return on investment. Among them, ArcGIS 10.5 is a collection of software modules for geographic data processing and analysis, capable of accurately locating the sampling sites of mangrove plants.

[0052] In the specific implementation of S7, based on the different δ 15 N isotope ratios of mangrove plants, the sources of nitrogen pollution are determined;

[0053] Specifically, based on the different δ 15 N isotope ratios of mangrove plants measured by the DELTAV Advantage isotope ratio mass spectrometer, the sources of nitrogen pollution are determined. When the δ 15 N isotope ratio of mangrove plants > +10.00‰ (generally 10‰ - 25‰), it indicates that the source of nitrogen pollution is urban domestic sewage; when the δ 15 N isotope ratio of mangrove plants is -2‰ - +2‰, it indicates that the source of nitrogen pollution is agricultural synthetic fertilizers; when the δ 15 N isotope ratio of mangrove plants is +2‰ - +10‰, it indicates that it comes from the natural ecological environment that has not been affected by human activities, industrial and agricultural production.

[0054] After considering the specification and practicing the content disclosed herein, those skilled in the art will readily conceive of other embodiments of this application. This application aims to cover any variations, uses, or adaptations of this application, which follow the general principles of this application and include the common knowledge or conventional technical means in this technical field that are not disclosed in this application. The specification and examples are only regarded as exemplary, and the true scope and spirit of this application are pointed out by the claims.

[0055] It should be understood that this application is not limited to the exact structure described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is only limited by the appended claims.

Claims

1. A method for source apportionment of nitrogen pollution in mangroves based on stable nitrogen isotope composition, comprising the following steps: Mangrove plants were cultured in the laboratory to ensure that the initial isotope values of each plant were consistent; placing cages in mangroves with a series of nitrogen concentration gradients, and planting the mangrove plants in the cages; The mangrove plants were grown in the cages for at least one month to ensure isotopic fusion of the mangrove plants; Collecting mangrove plant samples from the cage multiple times, drying the mangrove plant samples, grinding them into powder and preparing aluminum-tin capsules; Using stable isotope ratio mass spectrometry, the δ 15 N isotope ratio; According to the δ 15 N isotope ratio, drawing spatial variation map, temporal variation map and hot spot map; According to the δ 15 The difference in N isotope ratios can be used to determine the source of nitrogen pollution; when the δ 15 When the N isotope ratio is greater than +10.00‰, it indicates that the source of nitrogen pollution is urban domestic sewage; when the δ 15 When the N isotope ratio is -2‰ to +2‰, it indicates that the source of nitrogen pollution is agricultural synthetic fertilizers; when the δ 15 When the N isotope ratio is +2‰ to +10‰, it indicates that it comes from a natural ecological environment that is not affected by human activities, industrial and agricultural production.

2. The method according to claim 1, characterized in that The laboratory culture is carried out for 30-40 days.

3. The method according to claim 1, characterized in that Mangrove plant samples were collected from the cages at a frequency of 1-2 times per month for one year.

4. The method according to claim 1, wherein Each sampling period is after low tide, that is, at low tide.

5. The method according to claim 1, wherein Each time, 10.0-15.0 mg wet weight of mangrove plant samples were collected from the cages.

6. The method according to claim 1, characterized in that The drying temperature is 50-55° C., and the drying time is 40-48 hours.

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