A method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy

Abstract

A method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy. The present invention relates to the field of environmental monitoring and intelligent electromagnetic perception, and in particular to a method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy. The present invention aims to solve the technical problems of long monitoring cycle, lack of representativeness of sampling, complex chemical pretreatment process of water samples, and high difficulty of analysis process in existing traditional detection technologies. Method: Collect water samples and determine the ammonia nitrogen concentration of water samples; use a fluorescence spectrophotometer to scan the three-dimensional fluorescence spectrum matrix data of water samples; use a parallel factor analysis method to analyze and obtain the optimal component number M of the water sample and the N fluorescence intensities of each component; determine the organic component Cm that characterizes the ammonia nitrogen concentration of the water sample, and obtain a "component Cm fluorescence intensity-ammonia nitrogen concentration" curve; detect the ammonia nitrogen concentration of the new water sample to be tested. The method for monitoring ammonia nitrogen concentration in water of the present invention is quick, sensitive and effective. The method of the present invention is used to monitor the ammonia nitrogen concentration in water.

Description

Technical Field

[0001] The present invention relates to the field of environmental monitoring and intelligent electromagnetic perception, and in particular to a method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy. Background Art

[0002] Water pollution has always been the focus of environmental monitoring work, and the deterioration of water quality poses a threat to the ecosystem and human health. Organic pollutants mainly come from pollution from the service industry, aquaculture, surface runoff and aquatic biological sources, mainly organic pollutants such as protein, amino acids, and humic acid. Taking pig wastewater as an example, it is the main source of agricultural wastewater in my country. It is difficult to meet the discharge standards after biotechnology treatment, especially high-concentration ammonia nitrogen is difficult to remove through microbial degradation. Ammonia nitrogen concentration is one of the important indicators for measuring water quality. Most sewage treatment plants use daily manual monitoring and analysis, which is time-consuming and labor-intensive and cannot reflect the changes in pollutant concentrations in tail water in real time. Traditional monitoring technology has difficulties such as long monitoring cycle, lack of representative sampling, complex chemical pretreatment process of water samples, and high difficulty of analysis process, resulting in insufficient distribution of monitoring data in time and space. Therefore, it is of great significance to develop fast, sensitive and effective water quality monitoring technology.

[0003] Three-dimensional fluorescence spectroscopy can obtain fluorescence intensity information when the excitation wavelength and emission wavelength or other variables change simultaneously. It can spectrally identify and characterize objects with overlapping fluorescence spectra (emission / excitation, Ex / Em) in multi-component complex systems. It is an efficient and convenient spectral fingerprint technology and is increasingly widely used in the characterization of water quality in oceans, lakes, and engineering fields. Previous studies have found that dissolved organic matter (DOM) is one of the most important types of pollutants widely present in sewage. By characterizing the composition and content of DOM in sewage, the concentration of ammonia nitrogen in sewage can be indirectly monitored. However, at present, three-dimensional fluorescence spectroscopy is mainly used to characterize the characteristics of each component in natural organic matter, and then analyze the types of DOM in water. There are no reports on its use for monitoring ammonia nitrogen concentration. Summary of the invention

[0004] The present invention aims to solve the defects of existing traditional detection technology, such as long monitoring cycle, lack of representative sampling, complex chemical pretreatment process of water samples and high difficulty of analysis process, and provide a method for monitoring ammonia nitrogen concentration in water quickly, sensitively and effectively, avoiding the use of chemical reagents and complex water sample pretreatment process.

[0005] A method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy is specifically carried out in the following steps:

[0006] 1. Collect water samples to be tested every day for N consecutive days to obtain N water samples;

[0007] 2. Determine the ammonia nitrogen concentration of the N water samples in step 1 by spectrophotometry;

[0008] 3. Scan and measure the N water samples described in step 1 using a fluorescence spectrophotometer;

[0009] The measurement parameters were set as follows: the excitation wavelength was 220-500 nm, the emission wavelength was 220-550 nm, the scanning step was 5 nm, and the three-dimensional fluorescence spectrum matrix data of N water samples were measured;

[0010] Fourth, using the three-dimensional fluorescence spectrum matrix data obtained in step three, a parallel factor analysis method is used to obtain the optimal number of components M of the water sample and the N fluorescence intensities of each component;

[0011] 5. Perform K-order polynomial fitting on the N fluorescence intensities of the M components in step 4 and the ammonia nitrogen concentration values ​​of the N water samples obtained in step 2, respectively, where 1≤K≤3, to obtain 3×M correlation coefficients;

[0012] 6. Select the largest correlation coefficient from the 3×M correlation coefficients described in step 5, and use the component Cm corresponding to this correlation coefficient as the organic component characterizing the ammonia nitrogen concentration of the water sample. The order corresponding to the largest correlation coefficient is used as the best fitting order, and the fitting curve of this fitting order is used as the "component Cm fluorescence intensity-ammonia nitrogen concentration" curve graph;

[0013] 7. Repeat steps 3 to 4 for the new water sample to be tested to obtain the fluorescence intensity of component Cm, and obtain the ammonia nitrogen concentration of the new water sample to be tested according to the fitting curve in step 6.

[0014] Step 2: Determine using the Nessler reagent spectrophotometric method specified in the "Water and Wastewater Monitoring and Analysis Methods".

[0015] The K-order polynomial fitting formula in step 5 is:

[0016]

[0017] Wherein, F is the fluorescence intensity, H is the ammonia nitrogen concentration, a0 and a1 are the first-order polynomial fitting coefficients, b0, b1, b2 are the second-order polynomial fitting coefficients, c0, c1, c2, c3 are the third-order polynomial fitting coefficients.

[0018] The beneficial effects of the present invention are:

[0019] The present invention provides a method for monitoring the concentration of ammonia nitrogen in water quickly, sensitively and effectively based on three-dimensional fluorescence spectroscopy, avoiding the excessive use of chemical reagents and complicated water sample pretreatment process in traditional monitoring technology.

[0020] Common methods for detecting ammonia nitrogen concentration include test paper detection method, spectrophotometry and distillation-neutralization titration method. The test paper detection method uses a colorimetric tube to develop color, and then compares the color with the naked eye. It is a qualitative detection method and cannot obtain a quantitative value of ammonia nitrogen concentration. Although the spectrophotometry and distillation-neutralization titration methods can obtain more accurate detection values, they both require the consumption of chemical agents, are prone to secondary pollution, and the detection process is cumbersome and the detection cycle is long. The present invention provides a method for quickly, sensitively and effectively monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy, which avoids the excessive use of chemical reagents and complicated water sample pretreatment processes in traditional monitoring technologies.

[0021] The method of the invention is used for monitoring the ammonia nitrogen concentration in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a process for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy according to a specific implementation method 1;

[0023] Figure 2 The three-dimensional fluorescence spectrum of component 1 in step five of Example 1;

[0024] Figure 3 The three-dimensional fluorescence spectrum of component 2 in step five of Example 1;

[0025] Figure 4 The three-dimensional fluorescence spectrum of component 3 in step five of Example 1;

[0026] Figure 5 104 fluorescence intensity images of the three organic components in step 5 of Example 1, where represents component 1, “○” represents component 2, and “·” represents component 3;

[0027] Figure 6 This is a graph of “component Cm fluorescence intensity-ammonia nitrogen concentration” obtained by fitting in step seven of Example 1, where “·” represents the ammonia nitrogen concentration of 104 water samples and “—” represents the fitting curve. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0029] Specific implementation method 1: This implementation method is a method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy, characterized in that the method is specifically carried out in the following steps:

[0030] 1. Collect water samples to be tested every day for N consecutive days to obtain N water samples;

[0031] 2. Determine the ammonia nitrogen concentration of the N water samples in step 1 by spectrophotometry;

[0032] 3. Scan and measure the N water samples described in step 1 using a fluorescence spectrophotometer;

[0033] The measurement parameters were set as follows: the excitation wavelength was 220-500 nm, the emission wavelength was 220-550 nm, the scanning step was 5 nm, and the three-dimensional fluorescence spectrum matrix data of N water samples were measured;

[0034] Fourth, using the three-dimensional fluorescence spectrum matrix data obtained in step three, a parallel factor analysis method is used to obtain the optimal number of components M of the water sample and the N fluorescence intensities of each component;

[0035] 5. Perform K-order polynomial fitting on the N fluorescence intensities of the M components in step 4 and the ammonia nitrogen concentration values ​​of the N water samples obtained in step 2, respectively, where 1≤K≤3, to obtain 3×M correlation coefficients;

[0036] 6. Select the largest correlation coefficient from the 3×M correlation coefficients described in step 5, and use the component Cm corresponding to this correlation coefficient as the organic component characterizing the ammonia nitrogen concentration of the water sample. The order corresponding to the largest correlation coefficient is used as the best fitting order, and the fitting curve of this fitting order is used as the "component Cm fluorescence intensity-ammonia nitrogen concentration" curve graph;

[0037] 7. Repeat steps 3 to 4 for the new water sample to be tested to obtain the fluorescence intensity of component Cm, and obtain the ammonia nitrogen concentration of the new water sample to be tested according to the fitting curve in step 6.

[0038] Specific implementation mode 2: This implementation mode is different from the specific implementation mode 1 in that: the N in step 1 is 100 to 200. The rest is the same as the specific implementation mode 1.

[0039] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: step 2 adopts Nessler's reagent spectrophotometry for determination. The rest is the same as specific implementation method 1 or 2.

[0040] Specific implementation method 4: This implementation method is different from specific implementation methods 1 to 3 in that: in step 3, the water sample is filtered using an acetate fiber filter membrane after sampling. The rest is the same as specific implementation methods 1 to 3.

[0041] This embodiment filters the water sample to prevent suspended matter from interfering with spectral analysis.

[0042] Specific implementation mode 5: This implementation mode is different from specific implementation modes 1 to 4 in that the pore size of the filter membrane is 0.45 μm. The rest is the same as specific implementation modes 1 to 4.

[0043] Specific implementation method 6: This implementation method is different from specific implementation methods 1 to 5 in that: in step 3, the filtered water sample is frozen and stored, and thawed and warmed to room temperature before scanning with a fluorescence spectrophotometer. The rest is the same as specific implementation methods 1 to 5.

[0044] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that the freezing temperature in step 3 is -10 to -20° C. The rest is the same as specific embodiments 1 to 6.

[0045] Specific implementation example 8: This implementation example is different from specific implementation examples 1 to 7 in that the excitation width in step 3 is 5 nm, and the emission slit width is 10 nm. The rest is the same as specific implementation examples 1 to 7.

[0046] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the scanning speed in step 3 is controlled to be 1200 nm / min. The rest is the same as specific embodiments 1 to 8.

[0047] Specific embodiment ten: This embodiment differs from one of specific embodiments one to nine in that: Step four, the parallel factor analysis method includes tools for identifying abnormal samples, performing residual analysis and semi-confirmatory analysis;

[0048] First, a sample data set is created; second, the Raman scattering peak and the Rayleigh scattering peak are removed to limit the spectral noise area of ​​the matrix; finally, the sample identification components and their quantities are verified by splitting, semi-verification and random initialization methods to obtain the optimal component category of the sample. The rest is the same as the specific implementation methods one to nine.

[0049] The following examples are used to verify the beneficial effects of the present invention:

[0050] Embodiment 1:

[0051] This embodiment provides a method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy, which is specifically carried out in the following steps:

[0052] 1. Collect effluent from biological treatment of piggery wastewater for 26 consecutive days, multiple times a day, and obtain 104 water samples;

[0053] 2. Determine the ammonia nitrogen concentration of the 104 water samples described in step 1 by Nessler's reagent spectrophotometry;

[0054] 3. Immediately filter the water sample in step 1 through a cellulose acetate filter membrane with a pore size of 0.45 μm, and then freeze and store;

[0055] 4. Thaw the frozen water sample in step 3, warm it to room temperature, and scan the water sample using a fluorescence spectrophotometer (Hitachi, F-4600);

[0056] The measurement parameters were set as follows: the excitation wavelength (Ex) was 220-500 nm, the emission wavelength (Em) was 220-550 nm, the scanning step was 5 nm, the excitation width was 5 nm, the emission slit width was 10 nm, and the three-dimensional fluorescence spectrum matrix data of 104 water samples were measured; the scanning speed was controlled at 1200 nm / min, and ultrapure water in a 10 mm quartz cuvette was detected as a blank water sample;

[0057] Fifth, DOMFluor Toolbox was used to perform parallel factor analysis on all influent EEMs data, which included tools for identifying abnormal samples, performing residual analysis, and semi-validation analysis. First, a sample data set was created. Second, Raman and Rayleigh scattering peaks were removed to limit the spectral noise region of the matrix. Finally, the sample identification components and their number were verified using splitting, semi-validation, and random initialization methods, and the optimal component category of the sample was 3 components.

[0058] Among them, Figure 2 As shown, component 1 consists of two excitation peaks at Ex240,305 / Em415nm, belonging to microbial humus substances; Figure 3 As shown, component 2 has two peaks at Ex265,370 / Em485nm, belonging to terrestrial humus; Figure 4 As shown, component 3 has two excitation peaks at Ex235, 275 / Em320nm, belonging to a tyrosine-like substance; Figure 5 Shown are 104 fluorescence intensities of three organic components;

[0059] 6. The 104 fluorescence intensities of the three components in step 5 and the ammonia nitrogen concentrations of the 104 water samples obtained in step 2 were fitted with first-order, second-order and third-order polynomials, and 9 correlation coefficients were obtained. The first-order, second-order and third-order correlation coefficients of component 1 were 0.50, 0.51 and 0.43, respectively; the first-order, second-order and third-order correlation coefficients of component 2 were 0.87, 0.64 and 0.61, respectively; the first-order, second-order and third-order correlation coefficients of component 3 were 0.65, 0.66 and 0.41, respectively;

[0060] 7. Select the largest correlation coefficient of 0.87 from the 9 correlation coefficients described in step 6. The component Cm (i.e., component 2) corresponding to this correlation coefficient is used as the organic component characterizing the ammonia nitrogen concentration of the water sample. The order corresponding to the highest correlation coefficient is used as the best fitting order. The polynomial fitting curve of this fitting order is used as the "component Cm fluorescence intensity-ammonia nitrogen concentration" curve graph, as shown in Figure 6 As shown;

[0061] 8. Number the new water sample to be tested as 105, repeat steps 3 to 5 for the water sample, obtain the fluorescence intensity of component Cm as 0.25, and obtain the ammonia nitrogen concentration of the new water sample to be tested according to the fitting curve in step 7, and the ammonia nitrogen concentration of the new water sample to be tested is 66.3 mg / L.

[0062] The measured ammonia nitrogen concentration of the new water sample is 64.2 mg / L. It can be seen that this method can effectively monitor the ammonia nitrogen concentration in water.

Claims

1. A method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy, characterized in that The method is specifically carried out in the following steps:

1. Collect water samples to be tested every day for N consecutive days to obtain N water samples; 2. Determine the ammonia nitrogen concentration of the N water samples in step 1 by spectrophotometry; 3. Scan and measure the N water samples described in step 1 using a fluorescence spectrophotometer; The measurement parameters were set as follows: the excitation wavelength was 220-500 nm, the emission wavelength was 220-550 nm, the scanning step was 5 nm, and the three-dimensional fluorescence spectrum matrix data of N water samples were measured; Fourth, using the three-dimensional fluorescence spectrum matrix data obtained in step three, a parallel factor analysis method is used to obtain the optimal number of components M of the water sample and the N fluorescence intensities of each component; 5. Perform K-order polynomial fitting on the N fluorescence intensities of the M components in step 4 and the ammonia nitrogen concentration values ​​of the N water samples obtained in step 2, respectively, where 1≤K≤3, to obtain 3×M correlation coefficients; 6. Select the largest correlation coefficient from the 3×M correlation coefficients in step 5. The component Cm corresponding to this correlation coefficient is used as the organic component characterizing the ammonia nitrogen concentration of the water sample. The order corresponding to the largest correlation coefficient is used as the best fitting order. The fitting curve of this fitting order is used as the "component Cm fluorescence intensity-ammonia nitrogen concentration" curve graph; 7. Repeat steps 3 to 4 for the new water sample to be tested to obtain the fluorescence intensity of component Cm, and obtain the ammonia nitrogen concentration of the new water sample to be tested according to the fitting curve in step 6; Step 2: Nessler's reagent spectrophotometric determination; The K-order polynomial fitting formula in step 5 is: Where F is the fluorescence intensity, H is the ammonia nitrogen concentration, a 0. a 1 are the first-order polynomial fitting coefficients, b 0. b 1. b 2. are the second-order polynomial fitting coefficients, c 0. c 1. c 2. c 3 are the third-order polynomial fitting coefficients.

2. A method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy according to claim 1, characterized in that In step 1, N is 100-200.

3. According to claim 1, a method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy, characterized in that: Step 3: After water sampling, filter it using cellulose acetate filter membrane.

4. According to claim 3, a method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy is characterized in that: The pore size of the filter membrane is 0.45 μm.

5. The method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy according to claim 1, characterized in that: Step 3: Store the filtered water sample in frozen state, thaw it and warm it to room temperature before scanning with the fluorescence spectrophotometer.

6. The method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy according to claim 5, characterized in that: Step 3: The freezing temperature is -10~-20℃.

7. The method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy according to claim 1, characterized in that: Step 3: The excitation width is 5nm and the emission slit width is 10nm.

8. The method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy according to claim 1, characterized in that: Step 3: Control the scanning speed to 1200 nm / min.

9. The method for monitoring ammonia nitrogen concentration in water based on three-dimensional fluorescence spectroscopy according to claim 1, characterized in that: Step 4: Parallel factor analysis methods include tools to identify outlier samples, perform residual analysis, and semi-confirmatory analysis; First, a sample data set is created. Second, the Raman scattering peaks and Rayleigh scattering peaks are removed to limit the spectral noise area of ​​the matrix. Finally, the sample identification components and their quantities are verified by splitting, semi-verification and random initialization methods to obtain the optimal component category of the sample.

Images