Method for determining ecological reference threshold value of total nitrogen water

Abstract

The invention discloses a total nitrogen water ecology reference threshold determination method, and relates to the technical field of water ecology. The water ecological environments under different conditions can be simulated by constructing the ecological environment model, so that a reference basis can be provided for monitoring the benchmark threshold value of the collected water sample, the detection requirements under different conditions can be met, the practicability is high, and the application range is wide; by treating a water sample, nitrogen loss can be avoided, the measurement accuracy can be ensured, interference of ammonia nitrogen and nitrite is eliminated through a flocculation precipitation method, zinc sulfate and sodium hydroxide react to generate zinc hydroxide precipitate, suspended solids, turbidity, colloids and part of soluble substances are adsorbed and removed, and the accuracy is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydroecology, and particularly relates to a method for determining the hydroecological benchmark threshold of total nitrogen. Background Art

[0002] Total nitrogen, abbreviated as TN, is the total amount of various forms of inorganic and organic nitrogen in water. The total nitrogen content in water is one of the important indicators for measuring water quality. Total nitrogen includes inorganic nitrogen such as NO3-, NO2- and NH4+, and organic nitrogen such as proteins, amino acids and organic amines, and is calculated in milligrams of nitrogen per liter of water. It is often used to represent the degree of pollution of water bodies by nutrients.

[0003] The total nitrogen benchmark threshold refers to the critical concentration at which the total nitrogen concentration in the water body reaches or exceeds this value, and may cause water quality deterioration or ecological function decline. This threshold needs to be determined comprehensively in combination with specific water body types, aquatic ecosystems and environmental management objectives.

[0004] The Kjeldahl method in the prior art decomposes nitrogen in water samples through strong acids at high temperatures, converts it into ammonium sulfate, and then performs acid-base neutralization titration calculations. This method has high accuracy, but is complex in operation, time-consuming, and has limited detection effect on non-protein nitrogen. Therefore, we propose a method for determining the hydroecological benchmark threshold of total nitrogen. Summary of the Invention

[0005] The purpose of the present invention is: to solve the problems mentioned in the above background art, the present invention provides a method for determining the hydroecological benchmark threshold of total nitrogen.

[0006] The present invention specifically adopts the following technical solutions to achieve the above purpose:

[0007] A method for determining the hydroecological benchmark threshold of total nitrogen includes the following steps:

[0008] Step 1, construct an ecological environment model: simulate different aquatic environments and set different total nitrogen concentrations;

[0009] Step 2, collect water samples: place the collected water samples in test tubes;

[0010] Step 3, water sample treatment: perform pretreatment on the completed collection;

[0011] Step 4, measure organic nitrogen: separate organic nitrogen compounds by chromatography and quantify them in combination with mass spectrometry or thermal conductivity detection;

[0012] Step 5, measure inorganic nitrogen compounds: indirectly reflect the inorganic nitrogen content by measuring the nitrate ion concentration in the solution;

[0013] Step 6, total nitrogen determination: determine according to the content of organic nitrogen and the content of inorganic nitrogen compounds, and determine according to the formula total nitrogen = inorganic nitrogen + organic nitrogen.

[0014] Further, the construction of the ecological environment model includes the following steps:

[0015] Step 11, data collection and processing: Collect data through a combination of field surveys, remote sensing technology, monitoring network and sensor data, and historical records and literature;

[0016] Step 12, data verification: Process missing values and outliers through on-site verification and cross-checking;

[0017] Step 13, model establishment: Combine ecosystem dynamics models, material migration models, biogeochemical models, etc., and realize multi-scale and multi-process water ecological simulation through parameter calibration and model integration;

[0018] Step 14, model verification and optimization: Compare the simulation results with actual observation data, evaluate the accuracy, use cross-validation and sensitivity analysis to identify key parameters, adjust the model parameters according to the verification results, and optimize the model structure by combining expert consultation and laboratory simulation.

[0019] Further, the water sample treatment includes the following steps:

[0020] Step 31, water sample digestion: Mix the water sample with persulfate total nitrogen powder, and heat and digest;

[0021] Step 32, cooling and transfer: After digestion, cool to room temperature and transfer to a spectrophotometer for detection;

[0022] Step 33, calibration and standard: Calibrate the instrument with a high-concentration potassium nitrate standard solution, and establish a standard curve of absorbance vs. total nitrogen concentration.

[0023] Further, the heating temperature in the water sample digestion is 105 °C, and the digestion time is 30 minutes.

[0024] Further, the spectrophotometer selected is an ultraviolet spectrophotometer.

[0025] Further, the measurement of organic nitrogen is based on gas chromatography.

[0026] Further, the measurement of inorganic nitrogen compounds is based on ion-selective electrode method.

[0027] Further, the interference of ammonia nitrogen and nitrite in the measurement of organic nitrogen and the measurement of inorganic nitrogen compounds is eliminated by flocculation precipitation method. Zinc hydroxide precipitate is generated by the reaction of zinc sulfate and sodium hydroxide to adsorb and remove suspended solids, turbidity, colloid and some dissolved substances.

[0028] Further, the preparation process of zinc hydroxide is as follows: Prepare zinc sulfate and sodium hydroxide solutions, adjust the pH to 10.5, let it stand for 8 - 10 minutes to form a precipitate, and then filter.

[0029] Further, after the measurement of organic nitrogen and the measurement of inorganic nitrogen compounds are completed, standard calibration is carried out using a standard curve or a reference substance.

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. By constructing an ecological environment model, the present invention can simulate the water ecological environment under different conditions, thereby providing a reference basis for the monitoring of the benchmark threshold of water samples collection, meeting the detection requirements under different conditions, with strong practicability and wide application scope.

[0032] 2. Through the treatment of water samples, the present invention can avoid nitrogen loss, ensure the accuracy of measurement, eliminate the interference of ammonia nitrogen and nitrite by the flocculation precipitation method, generate zinc hydroxide precipitation by the reaction of zinc sulfate and sodium hydroxide, adsorb and remove suspended solids, turbidity, colloid and some dissolved substances, and further improve the accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the work flow chart of the present invention;

[0034] Figure 2 is the work flow chart of constructing the ecological environment model in the present invention;

[0035] Figure 3 is the work flow chart of water sample treatment in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0037] Please refer to Figure 1 - Figure 3 , the present invention provides a method for determining the total nitrogen hydroecology benchmark threshold, including the following steps:

[0038] Step 1, construct an ecological environment model: Simulate different aquatic environments and set different total nitrogen concentrations;

[0039] Step 2, collect water samples: Place the collected water samples in test tubes;

[0040] Step 3, water sample treatment: Perform pretreatment on the completed collection;

[0041] Step 4, measure organic nitrogen: Separate organic nitrogen compounds by chromatography and quantify by combining mass spectrometry or thermal conductivity detection;

[0042] Step 5, Measuring inorganic nitrogen compounds: Indirectly reflect the inorganic nitrogen content by measuring the concentration of nitrate ions in the solution;

[0043] Step 6, Total nitrogen determination: Determine according to the content of organic nitrogen and inorganic nitrogen compounds, and determine according to the formula total nitrogen = inorganic nitrogen + organic nitrogen.

[0044] In this embodiment, preferably, constructing an ecological environment model includes the following steps:

[0045] Step 11, Data collection and processing: Collect data by combining field surveys, remote sensing technology, monitoring network and sensor data, and historical records and literature;

[0046] Step 12, Data verification: Ensure reliability through on-site verification and cross-checking, process missing values and outliers to ensure data integrity;

[0047] Step 13, Establishing a model: Combine ecosystem dynamics models, material migration models, biogeochemical models, etc., and through parameter calibration and model integration, achieve multi-scale and multi-process water ecological simulation;

[0048] Step 14, Model verification and optimization: Compare the simulation results with actual observation data, evaluate the accuracy, use cross-validation and sensitivity analysis to identify key parameters, adjust the model parameters according to the verification results, and optimize the model structure by combining expert consultation and laboratory simulation.

[0049] By constructing an ecological environment model, it is possible to simulate water ecological environments under different conditions, thereby providing a reference basis for the benchmark threshold monitoring of water samples collected, meeting the detection requirements under different conditions, with strong practicability and a wide range of applications.

[0050] In this embodiment, preferably, water sample treatment includes the following steps:

[0051] Step 31, Water sample digestion: In sample treatment, mix the water sample with the total nitrogen persulfate powder and heat and digest it;

[0052] Step 32, Cooling and transfer: After digestion, cool to room temperature and transfer to a spectrophotometer for detection;

[0053] Step 33, Calibration and standard: Calibrate the instrument with a high-concentration potassium nitrate standard solution and establish a standard curve of absorbance vs. total nitrogen concentration.

[0054] In this embodiment, preferably, the heating temperature in water sample digestion is 105 °C and the digestion time is 30 minutes, which can avoid nitrogen loss and ensure the accuracy of measurement.

[0055] In this embodiment, preferably, an ultraviolet spectrophotometer is selected as the spectrophotometer; the ultraviolet spectrophotometer has high sensitivity and can detect substances at the ppm (one part per million) level; the ultraviolet-visible spectrophotometer can detect wavelengths in the range from ultraviolet to visible light, with a wide detection range; the sample will not be damaged or changed during the measurement process, so the sample can be used continuously, with excellent non-destructiveness; the ultraviolet spectrophotometer is easy to operate and use.

[0056] In this embodiment, preferably, the measurement of organic nitrogen is carried out based on gas chromatography; gas chromatography has the advantages of high selectivity, high separation efficiency, high sensitivity, rapid analysis, wide applicability, simple operation and low cost.

[0057] In this embodiment, preferably, the measurement of inorganic nitrogen compounds is carried out based on the ion selective electrode method; the ion selective electrode method has the advantages of convenient operation, accuracy and low cost.

[0058] In this embodiment, preferably, the interference of ammonia nitrogen and nitrite is eliminated by flocculation precipitation method for the measurement of organic nitrogen and inorganic nitrogen compounds. Zinc hydroxide precipitate is generated by the reaction of zinc sulfate and sodium hydroxide, which adsorbs and removes suspended solids, turbidity, colloids and some dissolved substances.

[0059] In this embodiment, preferably, the preparation process of zinc hydroxide is as follows: prepare zinc sulfate and sodium hydroxide solutions, adjust the pH to 10.5, and filter after standing for 8 - 10 minutes to form a precipitate.

[0060] In this embodiment, preferably, after the measurement of organic nitrogen and inorganic nitrogen compounds is completed, standard calibration is carried out using a standard curve or reference substance to ensure accuracy.

[0061] Through the treatment of water samples, nitrogen loss can be avoided, the accuracy of measurement can be guaranteed, and the interference of ammonia nitrogen and nitrite is eliminated by flocculation precipitation method. Zinc hydroxide precipitate is generated by the reaction of zinc sulfate and sodium hydroxide, which adsorbs and removes suspended solids, turbidity, colloids and some dissolved substances, further improving the accuracy.

[0062] The working principle and usage process of the present invention:

[0063] Step 1. Construct an ecological environment model: simulate different aquatic environments and set different total nitrogen concentrations; it includes the following steps:

[0064] Step 11. Data collection and processing: collect data by combining field surveys, remote sensing technology, monitoring network and sensor data, and historical records and literature materials;

[0065] Step 12, Data verification: Through on-site verification and cross-checking, reliability can be ensured, missing values and outliers are processed to ensure data integrity;

[0066] Step 13, Model establishment: Combine ecosystem dynamics models, material migration models, biogeochemical models, etc. Through parameter calibration and model integration, multi-scale and multi-process water ecological simulations are achieved;

[0067] Step 14, Model verification and optimization: Compare the simulation results with actual observation data, evaluate the accuracy, use cross-validation and sensitivity analysis to identify key parameters, adjust the model parameters according to the verification results, and optimize the model structure in combination with expert consultation and laboratory simulation.

[0068] Step 2, Collect water samples: Place the collected water samples in test tubes.

[0069] Step 3, Water sample treatment: Conduct pretreatment on the completed collection; it includes the following steps:

[0070] Step 31, Water sample digestion: In sample treatment, mix the water sample with persulfate total nitrogen powder, and conduct heating and digestion. The heating temperature is 105 °C, and the digestion time is 30 minutes, which can avoid nitrogen loss and ensure the accuracy of measurement;

[0071] Step 32, Cooling and transfer: After digestion, cool to room temperature and transfer to a spectrophotometer for detection. The spectrophotometer selected is an ultraviolet spectrophotometer; the ultraviolet spectrophotometer has high sensitivity and can detect substances at the ppm (parts per million) level; the ultraviolet-visible spectrophotometer can detect wavelengths in the range from ultraviolet to visible light, with a wide detection range; the sample will not be damaged or changed during the measurement process, so the sample can be used continuously, with excellent non-destructiveness; the ultraviolet spectrophotometer is simple to operate and easy to use;

[0072] Step 33, Calibrate the instrument using a high-concentration potassium nitrate standard solution and establish a standard curve of absorbance versus total nitrogen concentration.

[0073] Step 4, Measure organic nitrogen: Separate organic nitrogen compounds by chromatography and quantify in combination with mass spectrometry or thermal conductivity detection; Measure based on gas chromatography; Gas chromatography has the advantages of high selectivity, high separation efficiency, high sensitivity, rapid analysis, wide applicability, simple operation, and low cost.

[0074] Step 5, Measure inorganic nitrogen compounds: Indirectly reflect the inorganic nitrogen content by measuring the nitrate ion concentration in the solution; Measure based on the ion-selective electrode method; The ion-selective electrode method has the advantages of convenient operation, accuracy, and low cost.

[0075] The measurement of organic nitrogen and the measurement of inorganic nitrogen compounds eliminate the interference of ammonia nitrogen and nitrite by the flocculation precipitation method. Zinc hydroxide precipitation is generated by the reaction of zinc sulfate and sodium hydroxide, which adsorbs and removes suspended solids, turbidity, colloids and some dissolved substances. The preparation process of zinc hydroxide is as follows: Prepare zinc sulfate and sodium hydroxide solutions, adjust the pH to 10.5, let it stand for 8 - 10 minutes to form a precipitate, and then filter.

[0076] After the measurement of organic nitrogen and the measurement of inorganic nitrogen compounds are completed, standard calibration is carried out using a standard curve or a reference substance to ensure accuracy.

[0077] Step 6: Total nitrogen determination: Determine according to the content of organic nitrogen and the content of inorganic nitrogen compounds, and measure according to the formula total nitrogen = inorganic nitrogen + organic nitrogen.

[0078] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining a total nitrogen water ecology benchmark threshold, characterized in that: The steps include: Step 1: Construct an ecological environment model: simulate different aquatic environments and set different total nitrogen concentrations; Step 2, taking water samples: placing the collected water samples in a test tube; Step 3, water sample processing: pre-processing of the collected water; Step 4: Measure organic nitrogen: Separate organic nitrogen compounds by chromatography and quantify by mass spectrometry or thermal conductivity detection; Step 5, measuring inorganic nitrogen compounds: indirectly reflecting the inorganic nitrogen content by measuring the concentration of nitrate ions in the solution; Step 6, total nitrogen determination: Determine according to the content of organic nitrogen and the content of inorganic nitrogen compounds, and determine according to the formula total nitrogen = inorganic nitrogen + organic nitrogen.

2. A method for determining a total nitrogen water ecology benchmark threshold according to claim 1, characterized in that: The construction of the ecological environment model comprises the following steps: Step 11: Data collection and processing: Collect data through field surveys, remote sensing technology, monitoring networks and sensor data combined with historical records and literature; Step 12: Data verification: Process missing values ​​and outliers through field verification and cross-checking; Step 13: Model building: Combine ecosystem dynamics models, material migration models, biogeochemical models, etc., and achieve multi-scale and multi-process water ecological simulation through parameter calibration and model integration; Step 14: Model validation and optimization: Compare simulation results with actual observation data to evaluate accuracy, use cross-validation and sensitivity analysis to identify key parameters, adjust model parameters based on validation results, and optimize model structure through expert consultation and laboratory simulation.

3. The method for determining a total nitrogen water ecological benchmark threshold according to claim 1, characterized in that: The water sample processing comprises the following steps: Step 31, water sample digestion: Sample treatment: Mix the water sample with persulfate total nitrogen powder, and heat and digest it; Step 32, cooling and transferring: cooling to room temperature after digestion, and transferring to a spectrophotometer for detection; Step 33, calibration and standard: Use a high concentration potassium nitrate standard solution to calibrate the instrument and establish a standard curve of absorbance and total nitrogen concentration.

4. A method for determining a total nitrogen water ecological benchmark threshold according to claim 3, characterized in that: The heating temperature during the water sample digestion is 105° C., and the digestion time is 30 minutes.

5. The method for determining a total nitrogen water ecological benchmark threshold according to claim 3, characterized in that: The spectrophotometer is an ultraviolet spectrophotometer.

6. A method for determining a total nitrogen water ecological benchmark threshold according to claim 1, characterized in that: The measurement of organic nitrogen is based on gas chromatography.

7. The method for determining a total nitrogen water ecological benchmark threshold according to claim 1, characterized in that: The inorganic nitrogen compound is measured based on an ion selective electrode method.

8. The method for determining a total nitrogen water ecological benchmark threshold according to claim 1, characterized in that: The measurement of organic nitrogen and the measurement of inorganic nitrogen compounds eliminate the interference of ammonia nitrogen and nitrite through flocculation precipitation, generate zinc hydroxide precipitate through the reaction of zinc sulfate and sodium hydroxide, and adsorb and remove suspended matter, turbidity, colloid and some soluble substances.

9. A method for determining a total nitrogen water ecological benchmark threshold according to claim 8, characterized in that: The zinc hydroxide preparation process comprises: preparing zinc sulfate and sodium hydroxide solution, adjusting the pH to 10.5, standing for 8 to 10 minutes to form a precipitate, and then filtering.

10. The method for determining a total nitrogen water ecological benchmark threshold according to claim 1, characterized in that: After the measurement of organic nitrogen and the measurement of inorganic nitrogen compounds are completed, standard calibration is performed using a standard curve or a reference substance.

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