Soluble organic nitrogen accurate quantification and isotope analysis traceability method and device

Abstract

The invention discloses a method and a device for precisely quantifying soluble organic nitrogen and tracing isotope analysis. The method comprises the following steps: extracting, filtering and removing impurities, namely extracting soluble organic nitrogen and phosphorus in a sediment sample, centrifuging and filtering to remove impurities; separation and purification: carrying out electrodialysis, resin adsorption and anion and cation exchange resin separation and purification on the extracted and filtered soluble organic nitrogen and phosphorus solution to obtain purified soluble organic nitrogen and phosphorus components; concentration and enrichment or catalytic conversion: carrying out nanofiltration on the purified soluble organic nitrogen and phosphorus or carrying out concentration and enrichment on the purified soluble organic nitrogen and phosphorus by a vacuum freezing device, or carrying out catalytic oxidation on the purified soluble organic nitrogen and phosphorus to convert the purified soluble organic nitrogen and phosphorus into inorganic nitrogen and phosphorus; and quantitative and isotope analysis and traceability: carrying out accurate quantitative and isotope analysis on the purified or converted nitrogen and phosphorus, and tracing the source of the soluble organic nitrogen and phosphorus. According to the method, isotope content analysis of dissolved organic nitrogen and phosphorus in the sediment can be rapidly and accurately realized, and the source of the dissolved organic nitrogen and phosphorus can be effectively traced based on a detection result.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental monitoring, and particularly relates to a method and device for accurate quantification and isotopic analysis of dissolved organic nitrogen. BACKGROUND

[0002] Nitrogen is an essential nutrient element for the growth of marine organisms and is also a major influencing factor of primary productivity in many marine areas. However, due to the influence of industrial and agricultural activities, a large amount of active nitrogen is enriched in the earth's surface layer, especially in water, which has caused great ecological damage to aquatic ecosystems, such as water eutrophication, harmful algal blooms, etc. This is also one of the most serious environmental problems currently faced by aquatic ecosystems. Therefore, it is necessary to study the biogeochemical cycle process and influencing mechanism of nitrogen, and isotopic tracing is currently the most ideal technical means for studying the migration and transformation of nitrogen in aquatic ecosystems.

[0003] However, how to accurately and quickly analyze the isotopic ratio of dissolved nitrogen (NH4 + , NO3 - ) in water samples has been a major technical problem faced by the international community, especially the analysis of dissolved nitrogen isotopes in organic matter, which greatly limits the wide application of nitrogen isotope tracing technology.

[0004] Although, at present, NH4 + , NO3 - in water samples can be determined by stable isotope mass spectrometers after a series of biochemical reactions, but after the complicated chemical reactions, the experimental results often have errors beyond the acceptable range. At present, there is still no special and effective experimental method to directly and quickly analyze the content of dissolved organic nitrogen isotopes. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the defect that the existing processing method cannot directly and quickly analyze the content of dissolved organic nitrogen isotopes, so as to provide a method and device for accurate quantification and isotopic analysis of dissolved organic nitrogen.

[0006] A method for accurate quantification and isotopic analysis of dissolved organic nitrogen, comprising:

[0007] extracting and filtering impurities: extracting dissolved organic nitrogen in the sample, filtering out impurities to obtain a dissolved organic nitrogen solution;

[0008] separation and purification: separating and purifying the dissolved organic nitrogen solution to obtain purified dissolved organic nitrogen;

[0009] Concentration enrichment or catalytic conversion: the purified dissolved organic nitrogen is concentrated and enriched, or the purified dissolved organic nitrogen is catalytically converted into inorganic nitrogen.

[0010] Quantitative and isotopic analysis and tracing: the concentrated and enriched or converted nitrogen is accurately quantified and isotopically analyzed to trace the source of the dissolved organic nitrogen.

[0011] A sediment dissolved organic nitrogen and phosphorus fractionation extraction, accurate quantification and isotopic analysis and tracing method, comprising:

[0012] Extraction and impurity removal: extract dissolved organic nitrogen and phosphorus from the sediment sample, remove impurities by centrifugation and filtration to obtain a mixed solution of dissolved organic nitrogen and phosphorus and inorganic ions;

[0013] Separation and purification fractionation: separate and purify the mixed solution of dissolved organic nitrogen and phosphorus and inorganic ions to obtain a purified dissolved organic nitrogen and phosphorus solution, and continuously extract and fractionate the purified dissolved organic nitrogen and phosphorus solution to obtain dissolved organic nitrogen and phosphorus solutions of different components after purification and fractionation;

[0014] Concentration enrichment or catalytic conversion: the purified and fractionated dissolved organic nitrogen and phosphorus solution is concentrated and enriched to form a solid powder, or the purified and fractionated dissolved organic nitrogen and phosphorus solution is concentrated and enriched and catalytically converted into an inorganic nitrogen and phosphorus solution;

[0015] Quantitative and isotopic analysis and tracing: the concentrated and enriched or converted nitrogen is accurately quantified and isotopically analyzed to trace the source of the dissolved organic nitrogen.

[0016] The extraction and impurity removal method comprises a method of filtering and removing impurities after extraction with an extraction solution; the extraction solution is preferably one of H2O, KCl, K2SO4 and CaCl2 solution, and a bacteriostatic agent is also added to the extraction solution, the bacteriostatic agent is preferably HgCl2, the extraction temperature is in the range of 4-25°C, and the pH is 5-9; the process of filtering and removing impurities is: first centrifugation and then removal of suspended colloids and particulate matter and other impurities by filter membrane; preferably, the centrifugation parameters are 10000r / min centrifugation for 30min at 4°C, and the filter membrane is a glass fiber filter membrane with a pore size of 0.22-0.45 microns;

[0017] And / or, the separation and purification fractionation method comprises one or more of the following methods: electrodialysis method, anion and cathode electrode ionization method, anion and cation exchange membrane method, XAD-8 resin adsorption method, and anion and cation exchange resin method;

[0018] And / or, the concentration enrichment method comprises a vacuum concentration method and / or a nanofiltration method, and the vacuum concentration method is preferably a vacuum freeze concentration method;

[0019] And / or, the catalytic conversion method comprises a photocatalytic method and / or an advanced oxidation method.

[0020] The separation and purification grading process is:

[0021] The extracted and filtered impurity-removed soluble organic nitrogen and phosphorus solution is introduced into an ionization tank through a pressure regulation transmission system, and under the combined action of aluminum electrodes and cation and anion exchange membranes, the cations and anions in the extraction solution are fully separated from the soluble organic nitrogen and phosphorus, inorganic nitrogen and phosphorus and metal ion impurities are removed, and

[0022] The soluble organic nitrogen and phosphorus solution is passed through an XAD-8 resin column, the resin particle size is 50-250 μm, the flow rate is set to 1-2 mL / min, and the part passing through the resin column is collected, the pH is adjusted to 2 with 6 mol / L HCl, and the hydrophilic organic nitrogen and phosphorus is obtained by elution with 0.01 mol / L HCl.

[0023] Further, the resin column is washed with 0.1 mol / L HCl and 0.01 mol / L HCl, and washed with ultrapure water to obtain hydrophobic basic organic nitrogen and phosphorus, then the resin column is washed with 0.1 mol / L NaOH solution, and washed with ultrapure water to collect the washing solution to obtain hydrophobic acidic organic nitrogen and phosphorus, and after the resin column is dried, hydrophobic neutral organic nitrogen and phosphorus is obtained by Soxhlet extraction with methanol.

[0024] The extracted hydrophilic organic nitrogen and phosphorus solution is further passed through an Amberlyst 15 cation exchange resin, washed with 0.1 mol / L ammonia water to obtain hydrophilic basic organic nitrogen and phosphorus, then passed through an Amberlyst 21 anion exchange resin, washed with 1 mol / L, and then passed through an Amberlyst 15 cation exchange resin to obtain hydrophilic acidic organic nitrogen and phosphorus. After the Amberlyst 21 anion exchange resin column is dried, hydrophilic neutral organic nitrogen and phosphorus is obtained by Soxhlet extraction with methanol.

[0025] The process of the photocatalytic method is that the purified DON is contacted with a photocatalyst, and under the action of light, inorganic nitrogen is formed by degradation; the photocatalyst is a TiO2 catalyst, the spectral range of the light is 200-1000 nm, and the light time is not less than 30 min.

[0026] The addition amount of the photocatalyst is 1.5 g / L or more, and is preferably 1.5-2.5 g / L.

[0027] And / or, the light time is 30-800 min;

[0028] When the light source is a xenon lamp, the light time is 30-60 min;

[0029] When the light source is a mercury lamp, the light time is 700-800 min.

[0030] The device based on the above-mentioned accurate quantification and isotope analysis tracing method of soluble organic nitrogen comprises:

[0031] An extraction and filtration device is used for extracting and filtering the sample.

[0032] A separation and purification device is in communication with the extraction and filtration device and is used for separating and purifying the extracted and filtered solution to obtain the purified soluble organic nitrogen.

[0033] A concentration and enrichment device or a catalytic conversion device is in communication with the separation and purification device and is used for concentrating and enriching or catalytically converting the soluble organic nitrogen.

[0034] A quantification and isotope analysis and tracing device is used for accurately quantifying and isotope analyzing the concentrated and enriched or converted nitrogen.

[0035] The filtration device comprises a sample cup, a filtrate cup in communication with the sample cup, and a filter arranged between the sample cup and the filtrate cup.

[0036] The separation and purification device is an electrodialysis device, which is in communication with the water outlet of the extraction and filtration device and is used for separating and purifying the filtered liquid to obtain the purified soluble organic nitrogen.

[0037] The catalytic conversion device is a photocatalytic device, which comprises a transparent container with water inlets and outlets, a catalyst arranged in the transparent container, and a light source for providing light for the transparent container.

[0038] The water inlet of the transparent container is in communication with the water outlet of the electrodialysis device.

[0039] The water inlet of the electrodialysis device is in communication with the water outlet of the filtrate cup through a first liquid guide pipe, and a first peristaltic pump is arranged on the first liquid guide pipe.

[0040] The water inlet of the transparent container is in communication with the water outlet of the electrodialysis device through a second liquid guide pipe, and a second peristaltic pump is arranged on the second liquid guide pipe; a water inlet flow monitoring pipe is arranged between the water inlet of the transparent container and the second liquid guide pipe.

[0041] Ultraviolet-fluorescent signal sensors are arranged at the positions of the water inlets and outlets of the transparent container, respectively; and the light source is a high-pressure mercury lamp and a xenon lamp.

[0042] The water outlet of the transparent container is in communication with a liquid collector through a water outlet flow monitoring pipe.

[0043] The technical scheme has the following advantages:

[0044] 1. The application provides a method for accurate quantification and isotopic analysis of dissolved organic nitrogen, which comprises the following steps: obtaining a dissolved organic nitrogen solution by extraction and filtration, separating and purifying the dissolved organic nitrogen solution to obtain purified dissolved organic nitrogen, concentrating and enriching or catalytically converting the purified dissolved organic nitrogen, and finally accurately quantifying and isotopically analyzing the concentrated and enriched or catalytically converted nitrogen sample to trace the source of the dissolved organic nitrogen; the method can quickly and accurately realize isotopic content analysis of dissolved organic nitrogen, and effectively trace the source of dissolved organic nitrogen based on the detection results.

[0045] 2. The application provides a method for accurate quantification and isotopic analysis of dissolved organic nitrogen, which further comprises the following steps: under specific light conditions, the purified dissolved organic nitrogen is effectively photocatalytically degraded by combining with a specific catalyst, which can more completely degrade the dissolved organic nitrogen and will not cause result errors caused by existing complex biochemical reactions; the conversion is simpler, the results are more accurate compared with existing chemical conversion methods, and thus provides a prerequisite for accurate measurement of stable isotopes of dissolved organic nitrogen in the later stage.

[0046] 3. The device provided by the application effectively and automatically realizes accurate quantification and isotopic analysis of nitrogen, and only needs manual sampling to obtain accurate quantification and isotopic analysis results, which is more time-saving and labor-saving. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0048] Figure 1 Figure 1 is a structural schematic diagram of the device of embodiment 1 of the application;

[0049] Figure 2 Figure 5 is a structural schematic diagram of the device in embodiment 5 of the application;

[0050] Figure 3 Figure 5 is a structural schematic diagram of the device in embodiment 5 of the application;

[0051] Figure 4 Figure 5 is a structural schematic diagram of the device in embodiment 5 of the application;

[0052] BRIEF DESCRIPTION OF DRAWINGS

[0053] 1-sample cup, 2-filter, 3-filtrate cup, 4-first liquid guide pipe, 5-first peristaltic pump, 6-electrodialysis device, 7-second liquid guide pipe, 8-second peristaltic pump, 9-inlet water flow monitoring pipe, 10-transparent container, 11-catalyst, 12-light source, 13-ultraviolet-fluorescence signal sensor, 14-outlet water flow monitoring pipe, 15-liquid collector;

[0054] 21-first inlet pipe, 22-vibrating extraction system, 23-solid-liquid separation system, 24-impurity discharge pipeline, 25-sand core-microporous filter system, 26-vacuum negative pressure regulating system, 27-solution delivery pipeline, 28-ion exchange membrane, 29-aluminum electrode anode, 210-aluminum electrode cathode, 211-anode bin, 212-cathode bin, 213-sampling pipe and control valve, 214-acid-base solution regulating system, 215-XAD-8 adsorption resin, 216-cation exchange resin, 217-anion exchange resin, 218-second inlet pipe, 219-vacuum condenser, 220-nanofiltration system, 221-sample transmission system, 222-sample digestion system, 223-sample detection system. DETAILED DESCRIPTION

[0055] The technical solutions of the present application will be described clearly and completely in combination with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0056] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0057] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0058] In addition, the technical features involved in the different embodiments of the application described below can be combined with each other as long as they do not conflict with each other.

[0059] Embodiment 1

[0060] A pre-treatment device for accurate quantification and stable isotope analysis of dissolved organic nitrogen, comprising: a filtering device for filtering a water sample; a separation and purification device, which is also an electrodialysis device 6, for communicating with the water outlet of the filtering device to separate and purify the filtered water sample to obtain purified DON; a photocatalytic device, comprising a transparent container 10 with water inlets and outlets, a catalyst 11 arranged in the transparent container 10, and a light source 12 for providing light to the transparent container 10; the water inlet of the transparent container 10 is in communication with the water outlet of the electrodialysis device 6.

[0061] The filtering device effectively removes large-particle insoluble impurities such as sand and gravel, and the electrodialysis device 6 purifies the filtered water sample to obtain purified DON, avoiding the influence of soluble inorganic nitrogen salts on the final results. Finally, the photocatalytic device effectively converts the purified DON into inorganic matter, effectively realizing the extraction and conversion of dissolved organic nitrogen. Through the device of the present application, only manual sampling is required to obtain the converted substance, and the operation is more time-saving and labor-saving.

[0062] Further, in the filtering device, the filtering device is composed of a sample cup 1, a filtrate cup 3 and a filter 2; only the water sample needs to be added to the sample cup 1, and after filtering through the filter 2 at the outlet position of the sample cup 1, it enters the sample cup 1 for use. Preferably, the filter 2 is a filter membrane, which is arranged at the outlet position of the sample cup 1, and the water sample in the sample cup 1 enters the filtrate cup 3 after filtering through the filter membrane to obtain the filtered water sample.

[0063] The electrodialysis device 6 is of a conventional structure, and its principle and process of electrodialysis are not repeated here. In order to effectively add the filtered water sample in the filtrate cup 3 to the electrodialysis device 6, a first liquid guide pipe 4 communicating with the water inlet of the electrodialysis device 6 is arranged on the filtrate cup 3, and a first peristaltic pump 5 is arranged on the first liquid guide pipe 4; the water sample in the filtrate cup 3 is transported to the electrodialysis device 6 through the first liquid guide pipe 4 based on the power provided by the first peristaltic pump 5 for purification to obtain the purified DON.

[0064] The purified DON is transported to the photocatalytic device through a second liquid guide pipe 7, and a second peristaltic pump 8 is arranged on the second liquid guide pipe 7, so that the purified DON can be automatically transported from the electrodialysis device 6 to the photocatalytic device by the power provided by the second peristaltic pump 8.

[0065] The photocatalytic device in the application comprises a transparent container 10, a catalyst 11 and a light source 12, and the photocatalyst is a TiO2 catalyst. The purified DON enters the transparent container 10 and contacts the catalyst 11 arranged in the transparent container 10, the transparent container 10 is provided with light by the light source 12, the light is combined with the catalyst 11, and the catalytic effect is effectively achieved, so that the DON is converted into inorganic matter, and the converted water sample flows out of the transparent container 10 through the water outlet flow monitoring pipe 14 and enters the liquid collector 15, and the water sample collected by the liquid collector 15 is the water sample that can be subjected to subsequent stable isotope detection of dissolved organic nitrogen, thereby providing a premise for the detection of stable isotopes of dissolved organic nitrogen.

[0066] In order to achieve better catalytic effect, the transparent container 10 is a transparent container with a circulating pipeline, which can be spiral, circular, elliptical or coil-shaped, as long as the water sample can circulate in the circulating pipeline, such as Figure 1 As shown, the transparent container 10 is circular, which can effectively improve the contact between the water sample and the catalyst and further improve the catalytic effect.

[0067] In order to better realize automation, the water inlet flow monitoring pipe 9 and the water outlet flow monitoring pipe 14 are arranged on the water inlet and the water outlet of the transparent container 10 respectively, and an ultraviolet-fluorescent signal sensor 13 with a communication module is arranged in each of the water inlet flow monitoring pipe 9 and the water outlet flow monitoring pipe 14, so that the light intensity of the transparent container 10 can be understood in real time. A total controller can also be arranged in the application, which is in communication with the first peristaltic pump 5, the second peristaltic pump 8, the water inlet flow monitoring pipe 9, the water outlet flow monitoring pipe 14, the ultraviolet-fluorescent signal sensor 13 and the light source 12 respectively. The fluorescent intensity at the water inlet and the water outlet is detected by the ultraviolet-fluorescent signal sensor 13, the detected fluorescent intensity is fed back to the total controller through the communication module, and the light intensity and time of the light source 12 are controlled by the total controller, so that full-automatic control is realized.

[0068] Further, the light source 12 in the application is a high-pressure mercury lamp and a xenon lamp, which can simulate sunlight and ultraviolet light respectively, wherein the xenon lamp has a radiation spectrum range of 200-1000nm, a time of 30-60min, and preferably 60min; the mercury lamp has a radiation spectrum range of 200-600nm, a time of 700-800min, and preferably 700-750min, and more preferably 720min.

[0069] Example 2

[0070] A method for accurate quantification and isotopic analysis of dissolved organic nitrogen and traceability, comprising the following steps: extracting and filtering impurities: extracting dissolved organic nitrogen in a sample, filtering impurities to obtain a dissolved organic nitrogen solution; separation and purification: separating and purifying the dissolved organic nitrogen solution to obtain purified dissolved organic nitrogen; concentration and enrichment or catalytic conversion: concentrating and enriching the purified dissolved organic nitrogen, or catalytically converting the purified dissolved organic nitrogen into inorganic nitrogen. Quantification and isotopic analysis and traceability: accurately quantifying and isotopically analyzing the concentrated and enriched or converted nitrogen, and tracing the source of the dissolved organic nitrogen.

[0071] Specifically, the dissolved organic nitrogen catalytically converted can be obtained by using the pretreatment device for accurate quantification and stable isotopic analysis of dissolved organic nitrogen in Embodiment 1, and then the converted inorganic nitrogen can be used for quantification and isotopic analysis and traceability detection, and the specific conversion process and parameter conditions of the inorganic nitrogen are as follows:

[0072] (1) The water sample is introduced into the sample cup 1, and the first peristaltic pump 5 is started to make the water sample pass through the filter membrane and enter the filtrate cup 3, and then enter the electrodialysis device through the first liquid guide pipe 4 for separation and purification of DON;

[0073] (2) The second peristaltic pump 8 is started to make the purified DON enter the photocatalytic device through the water inflow monitoring pipe 9; the addition amount of the photocatalyst in the photocatalytic device is 1.5 g / L, that is, when the content of the photocatalyst in the photocatalytic device is 1.5 g, the total volume of the water sample entering the photocatalytic device is 1 L.

[0074] (3) Under the action of the light source 12 and the catalyst 11, the purified DON is circulated and degraded, and in this embodiment, the xenon lamp in the light source 12 is radiated for 60 min, and the mercury lamp is radiated for 720 min;

[0075] (4) After the irradiation and degradation are completed, the converted inorganic nitrogen solution enters the liquid collector 15 through the water outflow monitoring pipe 14.

[0076] Embodiment 3

[0077] The difference between this embodiment and Embodiment 2 is that the addition amount of the catalyst is 2.5 g / L, and in this embodiment, the xenon lamp in the light source 12 is radiated for 30 min, and the mercury lamp is radiated for 700 min.

[0078] Embodiment 4

[0079] The difference between this embodiment and Embodiment 2 is that the addition amount of the catalyst is 2 g / L, and in this embodiment, the xenon lamp in the light source 12 is radiated for 20 min, and the mercury lamp is radiated for 800 min.

[0080] The above-mentioned modes of embodiments 2-4 can effectively obtain detection samples convenient for quantitative and isotopic analysis and tracing, so as to achieve the purpose of accurate quantitative detection of isotopes and facilitate subsequent isotopic analysis and tracing.

[0081] Embodiment 5

[0082] A pretreatment device for sediment dissolved organic nitrogen and phosphorus fractionation extraction, accurate quantitative and isotopic analysis and tracing, as shown in Figure 2 , comprising:

[0083] A filtering device is used for filtering water samples from different sources, and is specifically configured as: a first sample inlet pipe 21, an oscillation extraction system 22, a solid-liquid separation system 23, a sand core-micro porous filter membrane filtering system 25, a vacuum negative pressure adjusting system 26, a solution conveying pipeline 27, which are sequentially connected; the solid-liquid separation system 23 is provided with an impurity discharge pipeline 24; the sediment sample and the extraction liquid are introduced from the first sample inlet pipe 21 into the oscillation extraction system 22 for oscillation extraction, the extraction liquid is preferably one of H2O, KCl and CaCl2 solution, and HgCl2 is used as a bacteriostatic agent, the extraction temperature ranges between 4℃ and 25℃, and the pH ranges between 5 and 9. After extraction, the solid-liquid separation system 23 is used for solid-liquid separation, the separated liquid enters the sand core-micro porous filter membrane filtering system 25 for filtration, and the mixed solution after filtration is obtained, the mixed solution is conveyed through the solution conveying pipeline 27 by the vacuum negative pressure adjusting system 26 to enter the subsequent separation and purification device.

[0084] A separation and purification device, comprising a positive and negative aluminum electrode ionization system, a positive and negative ion exchange membrane 28 and a fractionation purification system; the positive and negative aluminum electrode ionization system comprises an ionization bin, an anode bin 211 and a cathode bin 212 located at opposite sides of the ionization bin, an aluminum electrode anode 29 arranged in the anode bin 211, and an aluminum electrode cathode 210 arranged in the cathode bin 212; the ion exchange membrane 28 is arranged in the ionization bin, the water outlet end of the ionization bin is connected to the sand core-micro porous filter membrane filtering system 25 for filtration to obtain a filtered solution, and the filtered solution is conveyed through the vacuum negative pressure adjusting system 26 and the solution conveying pipeline 27 to enter the subsequent fractionation purification system, and the filtered solution is taken out through a sampling pipe and a control valve 213 to obtain a detection sample solution;

[0085] The graded purification system includes an XAD-8 adsorption resin 215, an Amberlyst 15 cation exchange resin 216, and an Amberlyst 21 anion exchange resin 217, which are connected in sequence. An acid-base solution control system 214 is provided before the XAD-8 adsorption resin 215, Amberlyst 15 cation exchange resin 216, and Amberlyst 21 anion exchange resin 217, and a sand core-microporous membrane filtration system 25 is provided after the XAD-8 adsorption resin 215, Amberlyst 15 cation exchange resin 216, and Amberlyst 21 anion exchange resin 217.

[0086] The acid-base concentration in the acid-base solution control system 214 before the XAD-8 adsorption resin 215 is adjusted to 0.01 mol / L HCl, and 0.01 mol / L HCl is used for elution to obtain a hydrophilic organic nitrogen phosphorus; the acid-base concentration is then adjusted to 0.1 mol / L HCl, 0.01 mol / L HCl, and 0.1 mol / L NaOH in sequence, and the resin column is washed with 0.1 mol / L HCl and 0.01 mol / L HCl in sequence to obtain a hydrophobic alkaline organic nitrogen phosphorus, and then the resin column is washed with 0.1 mol / L NaOH solution to obtain a hydrophobic acidic organic nitrogen phosphorus; after the resin column is dried, it is then Soxhlet extracted with methanol to obtain a hydrophobic neutral organic nitrogen phosphorus.

[0087] The acid-base concentration in the acid-base solution control system 214 before the Amberlyst 15 cation exchange resin 216 is adjusted to 0.1 mol / L ammonia water, and the hydrophilic alkaline organic nitrogen and phosphorus are obtained by washing with 0.1 mol / L ammonia water.

[0088] The acid-base concentration in the acid-base solution control system 214 before the Amberlyst 21 anion exchange resin 217 is adjusted to 1 mol / L ammonia water, and the hydrophilic acidic organic nitrogen and phosphorus are washed with 1 mol / L ammonia water. The Amberlyst 21 anion exchange resin 217 is dried and then Soxhlet extracted with methanol to obtain the hydrophilic neutral organic nitrogen and phosphorus.

[0089] Concentration and enrichment devices, such as Figure 3 As shown, the system for concentrating and enriching dissolved organic nitrogen includes a vacuum condenser 219 or a nanofiltration system 220, a sample transmission system 221, and a sample digestion system 222, which are sequentially arranged. Amberlyst 21 anion exchange resin 217 is connected to the vacuum condenser 219 or the nanofiltration system 220 via a second sample inlet tube 218 for concentration. The concentrated sample then passes through the sample transmission system 221 to the sample digestion system 222. The sample digestion system 222 digests the sample before it enters the subsequent sample detection system 223.

[0090] Quantitative and isotopic analysis and tracing device, i.e. sample detection system 223, is used for accurate quantitative and isotopic analysis of concentrated enriched or transformed nitrogen.

[0091] The organic nitrogen and phosphorus contents in each step are as follows Figure 4 and shown in Table 1 below.

[0092] Table 1 Dissolved organic nitrogen and phosphorus extraction, separation, enrichment, and quantitative results (mg / L)

[0093]

[0094]

[0095] Obviously, the above examples are merely illustrative and not limiting. Other variations or changes in different forms can be made by those of ordinary skill in the art based on the above description. It is not necessary or possible to exhaust all embodiments. The obvious changes or changes still fall within the protection scope of the present application.

Claims

1. A method for accurate quantification and isotope analysis and traceability of dissolved organic nitrogen, characterized in that: include: Extraction, filtration and impurity removal: Extract the dissolved organic nitrogen in the sample, filter and remove impurities to obtain a dissolved organic nitrogen solution; Separation and purification: separating and purifying the dissolved organic nitrogen solution to obtain purified dissolved organic nitrogen; Concentration and enrichment or catalytic conversion: concentrating and enriching the purified dissolved organic nitrogen, or catalytically converting the purified dissolved organic nitrogen into inorganic nitrogen; Quantification, isotope analysis and traceability: The concentrated or converted nitrogen is subjected to precise quantification and isotope analysis to trace the source of dissolved organic nitrogen.

2. A method for fractional extraction, precise quantification and isotope analysis of dissolved organic nitrogen and phosphorus in sediments, characterized in that: include: Extraction, filtration and impurity removal: Extract dissolved organic nitrogen and phosphorus from sediment samples, centrifuge and filter to remove impurities to obtain a mixed solution of dissolved organic nitrogen and phosphorus and inorganic ions; Separation, purification and classification: separating and purifying the mixed solution of soluble organic nitrogen and phosphorus and inorganic ions to obtain a purified soluble organic nitrogen and phosphorus solution, and continuously extracting and classifying the purified soluble organic nitrogen and phosphorus solution to obtain purified and classified soluble organic nitrogen and phosphorus solutions of different components; Concentration and enrichment or catalytic conversion: the purified and classified dissolved organic nitrogen and phosphorus solution is concentrated and enriched to be converted into a solid powder, or the purified and classified dissolved organic nitrogen and phosphorus solution is concentrated and enriched and catalytically converted into an inorganic nitrogen and phosphorus solution; Quantification, isotope analysis and traceability: The concentrated or converted nitrogen and phosphorus are accurately quantified and isotopically analyzed to trace the source of dissolved organic nitrogen and phosphorus in the sediment.

3. The method according to claim 1 or 2, characterized in that The extraction, filtration and impurity removal method comprises a method of extracting with an extracting solution and then filtering and removing impurities; the extracting solution is preferably one of H2O, KCl, K2SO4 and CaCl2 solutions, an antibacterial agent is further added to the extracting solution, and the antibacterial agent is preferably HgCl2, the extraction temperature range is 4°C-25°C, and the pH is 5-9; preferably, the centrifugation parameters in the extraction, filtration and impurity removal are 10000r / min at 4°C for 30min, and the filtration is performed using a filter membrane with a pore size of 0.22-0.45 micron, preferably a glass fiber filter membrane with a pore size of 0.22-0.45 micron; And / or, the separation, purification and classification method includes one or more of an electrodialysis method, an anion and alumina electrode ionization method, an anion and cation exchange membrane method, an XAD-8 resin adsorption method, and an anion and cation exchange resin method; And / or, the concentration and enrichment method includes a vacuum concentration method and / or a nanofiltration method, and the vacuum concentration method is preferably a vacuum freeze concentration method; And / or, the catalytic conversion method includes a photocatalytic method and / or an advanced oxidation method.

4. The method according to claim 3, characterized in that The process of separation, purification and classification is as follows: The extracted, filtered, and impurity-removed soluble organic nitrogen and phosphorus solution is passed into an ionization tank, where the anions and cations in the extract are fully separated from the soluble organic nitrogen and phosphorus under the combined action of an aluminum electrode and anion and cation exchange membrane, and inorganic nitrogen and phosphorus and metal ion impurities are removed to obtain a primary soluble organic nitrogen and phosphorus solution; The primary soluble organic nitrogen and phosphorus solution was passed through an XAD-8 resin column with a resin particle size of 50 to 250 μm at a flow rate of 1 to 2 mL / min. The portion passing through the resin column was collected and the pH was adjusted to 2 with 6 mol / L HCl, and then eluted with 0.01 mol / L HCl to obtain the hydrophilic organic nitrogen and phosphorus. The resin column was then washed with 0.1 mol / L HCl and 0.01 mol / L HCl in sequence, and then rinsed with ultrapure water to obtain a hydrophobic alkaline organic nitrogen phosphate; The resin column is then washed with a 0.1 mol / L NaOH solution and rinsed with ultrapure water, and the washing liquid is collected to obtain a hydrophobic acidic organic nitrogen phosphate; the resin column is dried and then subjected to Soxhlet extraction with methanol to obtain a hydrophobic neutral organic nitrogen phosphate; The extracted hydrophilic organic nitrogen and phosphorus solution is passed through Amberlyst 15 cation exchange resin, washed with 0.1 mol / L ammonia water to obtain hydrophilic alkaline organic nitrogen and phosphorus, then passed through Amberlyst 21 anion exchange resin, washed with 1 mol / L ammonia water, and then passed through Amberlyst 15 cation exchange resin to obtain hydrophilic acidic organic nitrogen and phosphorus. The Amberlyst 21 anion exchange resin column is dried and then Soxhlet extracted with methanol to obtain hydrophilic neutral organic nitrogen and phosphorus. And / or, the process of the photocatalytic method is: The purified soluble organic nitrogen is brought into contact with a photocatalyst and degraded to form inorganic nitrogen under the action of light; the photocatalyst is a TiO2 catalyst, the spectrum range of the light is 200 to 1000 nm, and the light exposure time is not less than 30 minutes.

5. The method according to claim 4, characterized in that The amount of the photocatalyst added is 1.5 g / L or more, preferably 1.5 to 2.5 g / L; And / or, the illumination time is 30 to 800 minutes; And / or, when the light source of the illumination is a xenon lamp, the illumination time is 30 to 60 minutes; And / or, when the light source of the illumination is a mercury lamp, the illumination time is 700 to 800 minutes.

6. The device according to any one of claims 1 to 5, characterized in that: include: An extraction and filtration device, used for extracting and filtering samples; A separation and purification device, connected to the extraction and filtration device, is used to separate and purify the extracted and filtered solution to obtain purified soluble organic nitrogen; A concentration and enrichment device or a catalytic conversion device, connected to the separation and purification device, is used to concentrate and enrich or catalytically convert dissolved organic nitrogen; Quantitative and isotopic analysis and traceability device, used for accurate quantification and isotopic analysis of concentrated or converted nitrogen.

7. The device according to claim 6, characterized in that The filtering device comprises a sample cup (1), a filtrate cup (3) connected to the sample cup (1), and a filter (2) arranged between the sample cup (1) and the filtrate cup (3); And / or, the separation and purification device is an electrodialysis device (6), which is connected to the water outlet of the extraction and filtration device to separate and purify the filtered liquid to obtain purified dissolved organic nitrogen; And / or, the catalytic conversion device is a photocatalytic device, comprising a transparent container (10) having a water inlet and outlet, a catalyst (11) disposed in the transparent container (10), and a light source (12) for providing light to the transparent container (10); The water inlet of the transparent container (10) is communicated with the water outlet of the electrodialysis device (6).

8. The device according to claim 7, characterized in that The water inlet of the electrodialysis device (6) is connected to the water outlet of the filtrate cup (3) through a first liquid conduit (4), and a first peristaltic pump (5) is provided on the first liquid conduit (4).

9. The device according to claim 7 or 8, characterized in that The water inlet of the transparent container (10) is connected to the water outlet of the electrodialysis device (6) through a second liquid guide tube (7), and a second peristaltic pump (8) is provided on the second liquid guide tube (7); a water inlet flow monitoring tube (9) is provided between the water inlet of the transparent container (10) and the second liquid guide tube (7); And / or, ultraviolet-fluorescence signal sensors (13) are respectively provided at the water inlet and outlet of the transparent container (10); and the light source (12) is a high-pressure mercury lamp and a xenon lamp.

10. The device according to any one of claims 7 to 9, characterized in that: The water outlet of the transparent container (10) is connected to a liquid collector (15) via a water flow monitoring tube (14).

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