CN113484294B - Diagnostic method for bonding capability of soluble organic carbon and electronic configuration metals of different valence layers - Google Patents
Diagnostic method for bonding capability of soluble organic carbon and electronic configuration metals of different valence layers Download PDFInfo
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N21/643—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" non-biological material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
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Abstract
The invention relates to a method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence layers, and belongs to the technical field of water ecology. According to the method, firstly, soluble organic carbon (DOC) components with different molecular weights are obtained through an ultrafiltration classification technology, wherein the soluble organic carbon (DOC) components comprise 0.1-1 kDa, 1-5 kDa, 5-10 kDa and 10-100 kDa DOCs; then, respectively carrying out fluorescence quenching titration experiments on DOC with different molecular weights and metal ions with different valence layer electron configurations (p, d and s areas) on the periodic table of elements; measuring three-dimensional fluorescence spectra of DOCs with different molecular weights before and after the experiment is finished, and obtaining fluorescent components participating in combination and fluorescence quenching curves of the components through parallel factor analysis (PARAFAC); and finally, calculating by using a modified Stren-Volmer model to obtain binding parameters of different fluorescent components and different valence-layer electron configuration metals, and obtaining affinity differences of the binding of the different components and the metals.
Description
Technical Field
The invention relates to the technical field of water ecology, in particular to a method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence layers.
Background
The soluble organic carbon (DOC) is an important water chemical index representing the level of soluble organic substances in water, is a very active chemical substance in a water ring, and has the characteristics of wide molecular weight range, complex composition and the like; DOC is an important carbon source for planktonic bacteria propagation metabolism, not only reflects the water environment pollution condition in a water body, but also characterizes the influence of human activities such as fertilization and irrigation, industrial construction, vegetation destruction and the like on water quality, and can reflect the effectiveness of the water body quality to different degrees by utilizing the DOC, so that the purposes of effectively monitoring the organic carbon content of the water body and the water body quality are achieved by detecting the DOC, meanwhile, the DOC can interact with metal ions to form an organic metal complex, the toxicity and bioavailability of free metal ions on aquatic organisms can be reduced, and the binding capacities of metals with different valence layer electronic configurations and the DOC are different; metals are widely existing in water environment, and the metal in sediment or surrounding soil can enter the water body through release and runoff, so that the risk of metal pollution exists in the water body; among metals with different valence layer electronic configurations on the periodic table (including s, p and d regions), most metals in the p and d regions have toxic effects on human health, and when the concentration of the metals in the water environment exceeds a threshold value, the toxic effects become obvious and can be enriched in organisms through migration and transformation or physical and chemical effects, so that ecological risks caused to the water environment are aggravated, while the metal ions in the s region do not obviously harm the water environment, the concentration of the metal ions in fresh water is higher, the toxicity of heavy metals to aquatic organisms is greatly influenced, and the health of human bodies is threatened indirectly, so that attention is also needed.
Because metal ions can interact with substances in the surrounding environment and are influenced by various environmental factors, pollution caused by the metal and ecological risks possibly caused by the metal need to be judged according to the environment where the metal ions are located, wherein DOC is one of main influencing factors influencing the environmental risks of the metal; the DOC can interact with metal ions to form an organic metal complex, so that the organic metal complex becomes a means for monitoring and measuring water quality, but the binding capacities of the electronic configuration metals (including s, p and d regions) of different valence layers and the DOC are different, compared with the binding capacities of the s region (Ca 2+ 、Mg 2+ 、Na + ) Metal element, p region (Al 3+ 、Pb 2+ ) And d region (Cd) 2+ 、Cu 2+ 、Fe 3+ 、Fe 2+ 、Zn 2+ ) The coordination capability of the metal element is higher, the pollution and the biotoxicity are stronger, and important distinction is needed; for example, the invention of Chinese patent No. CN201811072505.3 discloses a method for estimating the concentration of dissolved organic carbon in a lake, which constructs the correlation between the measured salinity S of the lake and the concentration of DOC by using measured data through a data fitting analysis method, and timely, quickly and accurately estimates the DOC concentration of the surface water after measuring the salinity value of the water in a field; however, the difference of metal ions contained in the soil is extremely large and the DOC concentration is changed due to the interaction between non-salt substances in the surrounding environment according to the difference of lake distribution, so that the measurement range cannot be limited only by the correlation of salinity and DOC, and the binding capacity of metals with different valence shell electron configurations and DOC is also different, and the concentration of the DOC in the region s (Ca 2+ 、Mg 2+ 、Na + ) The DOC combined with the metal elements has far less pollution to the environment than the DOC in the p region (Al 3+ 、Pb 2+ ) And d region (Cd) 2+ 、Cu 2+ 、Fe 3+ 、Fe 2+ 、Zn 2+ ) Brought by metal elementsPollution, so that the DOC concentration of the surface water body is not accurately estimated by only salinity measurement, and the DOC concentration obtained by not subdividing the electronic configuration metals of different valence layers cannot be used as a criterion of the water body quality; therefore, the intensive study of the binding capability of DOC and different valence layer electronic configuration metals, especially the binding capability of DOC and p and d region parts of toxic and harmful heavy metals, provides valuable information and reliable basis for evaluating and predicting the environmental behaviors of different metals in different water bodies.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: aiming at the problem that the binding capacity of different valence-layer electronic configuration metals, particularly the p-region and d-region toxic and harmful heavy metals, and DOC are different, and the environmental behaviors of different metals in different water bodies cannot be effectively estimated, the method for diagnosing the binding capacity of the soluble organic carbon and the different valence-layer electronic configuration metals is provided. According to the diagnosis method provided by the invention, the combination capability of DOC and different valence layer electronic configuration metals, especially the toxic and harmful heavy metals in p and d regions can be deeply researched, and valuable information and reliable basis can be provided for evaluating and predicting the environmental behaviors of different metals in different water bodies.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence layers is characterized by comprising the following steps:
(1) Pretreatment of a water sample:
according to the principle of parallel factor analysis, 20-40 sampling sections are arranged in a research area, collection is carried out at a position about 0.5 m below the water surface of each sampling section, a sampling bottle is pre-washed 3 times with water samples before sampling, 3 parts of parallel water samples are collected for each section and then mixed to obtain a sample, the sample is brought back to a laboratory and filtered by a glass fiber filter membrane with the diameter of 0.45 mu m and a vacuum suction filter, and then the sample is refrigerated and stored in a dark place at the temperature of 4 ℃ to obtain a pretreated water sample;
(2) DOC molecular weight fractionation:
the method comprises the steps of carrying out DOC molecular weight classification on a filtered pretreated water sample by an ultrafiltration method, wherein an instrument is an ultrafiltration cup and an ultrafiltration membrane, respectively using 50-60% NaOH solution and 60-70% HCl solution by mass fraction before the experiment starts, cleaning the ultrafiltration membrane without pressurizing and stirring, then adding deionized water for pressurizing and stirring to clean the ultrafiltration membrane, ultrafiltering 100 mL ultrapure water before formal ultrafiltration is carried out, taking a 10kDa ultrafiltration membrane at 25 ℃ for standby, placing 200 mL of the pretreated water sample into the ultrafiltration cup for pressurizing and filtering by nitrogen, collecting filtrate under the membrane, adding 10 mL deionized water into the ultrafiltration cup when the pretreated water sample is remained at 50 mL, continuing pressurizing and stirring to filter 10 mL, adding 10 mL deionized water into the ultrafiltration cup, pressurizing and stirring to filter 10 mL, pouring out concentrate on the membrane and adding 150 mL deionized water, namely the DOC solution which is 10-100 kDa, and adding 30 mL deionized water into the membrane, namely DOC solution which is 0.1-10 kDa, sequentially filtering membranes according to the method, and obtaining four molecular weight segments of DOC of 5 kDa in sequence: four DOC-like solutions are prepared from 0.1-1 kDa, 1-5 kDa, 5-10 kDa and 10-100 kDa;
(3) Fluorescence quenching titration experiments:
adding deionized water into the four DOC sample solutions for dilution until the concentration of all DOC sample solutions is 1-mg.L -1 Within the range of (2), DOC-like solutions 30 and mL were each introduced into a conical flask, and 0.01 mol/L (0, 60, 120, 180, 240, 300. Mu.L) was added dropwise to the conical flask -1 The metal solutions with different valence layer electron configurations are respectively used for leading the concentration of metal ions in the conical flask to be 0, 20, 40, 60, 80 and 100 mu mol.L -1 Ignoring the concentration dilution effect, and placing all samples in a constant temperature shaking box for shaking for 24 hours in a dark place after titration to prepare an experimental solution;
(4) Three-dimensional fluorescence spectrum scanning:
taking out the experimental solution after the combination and balance, and obtaining three-dimensional fluorescence scanning data of all samples by three-dimensional fluorescence spectrum scanning, wherein the excitation wavelength and the emission wavelength range are respectively 220-450 nm and 290-600 nm;
(5) Parallel factor analysis:
carrying out parallel factor analysis on three-dimensional fluorescence spectrum scanning data of all experimental solutions to obtain the maximum fluorescence intensity of different fluorescent components in each water sample;
(6) Calculation of the binding parameters:
the binding parameters between the metal and the parallel factor analysis derived fluorescent components were determined using a modified Stren-Volmer model, the calculation formula of which is as follows:
fitting a modified Stren-Volmer model: f (F) 0 /（F 0 -F）=1/（f*K*C M ）+1/f（1）。
The pore sizes of the ultrafiltration membranes in the step (2) are respectively 10kDa, 5 kDa and 1 kDa.
The metal solution in the step (3) is Cu 2+ 、Pb 2+ A solution.
The specific steps of three-dimensional fluorescence spectrum scanning in the step (4) are as follows:
(1) Three-dimensional fluorescence spectrum scanning is carried out on a fluorescence spectrum analyzer, the analyzer is matched with a 1 cm quartz cuvette, a 150W xenon arc lamp is adopted as an excitation light source, PMT voltage=400V, signal to noise ratio is 110-220, response time is set to be automatic, and scanning speed is set to be high: 60000 nm min -1 Excitation wavelength range λEX=220-450 nm, interval 5 nm, emission wavelength range λEm=290-600 nm, interval 1 nm, scanning spectrum to perform instrument automatic correction;
(2) Two-dimensional scanning and three-dimensional scanning are needed to be carried out by ultrapure water before fluorescence of the test solution is measured, so that Raman scattering correction and comparison of a fluorescence spectrum are carried out on the measurement result, and the fluorescence intensity unit is R.U.
The parallel factor analysis in the step (5) comprises the following specific steps:
(1) Parallel factor analysis is carried out to obtain fluorescence components shared by a plurality of DOCs, the parallel factor analysis is carried out on the processed fluorescence data set through MATLAB R2016a software, and the number of the fluorescence components is determined through residual analysis, core consistency analysis, half-division inspection and other methods;
(2) The obtained maximum fluorescence intensity of each fluorescence component can be compared to obtain the quenching intensities of the metal ions with different valence layer electron configurations on different fluorescence components of the DOC.
The modified Stren-Volmer model in the step (6) comprises the following steps:
F 0 the fluorescence intensity at the beginning of titration, i.e., when no metal is added, F is the metal concentration C M mol·L -1 Fluorescence intensity under.
The modified Stren-Volmer model in the step (6) comprises the following steps:
the ratio f of the conditional stability constant K to the fluorescent group involved in metal ion coordination was logarithmic for the conditional stability constant K to give a binding stability constant lgK.
The numerical relation in the modified Stren-Volmer model in the step (6) is as follows:
(1) Calculating the proportion f of the fluorescent groups involved in metal ion coordination through 1/f;
(2) The binding stability constant lgK is obtained by calculating the conditional stability constant K by 1/f×k and taking the logarithm of the conditional stability constant K.
The lgK value can characterize the difference in binding capacity of metal ions of different valence shell electron configurations to the DOC.
The beneficial effects of the invention are as follows:
(1) According to the invention, firstly, a soluble organic carbon (DOC) component is finely divided by an ultrafiltration grading technology to obtain DOC components with different molecular weights, the DOC components comprise four DOC sample solutions of 0.1-1 kDa, 1-5 kDa, 5-10 kDa and 10-100 kDa, further more test comparison examples are obtained, the coverage range of the test is widened, the scientificity and the reliability of a diagnosis method are improved, the DOC sample solutions with different molecular weights are respectively subjected to fluorescence quenching titration experiments with metal ions with different valence layer electronic configurations (p, d and s regions) on the periodic table of elements, and the DOC and the different valence layer electronic configuration metals, especially heavy metal Cu with high toxicity with the p and d regions, are deeply studied by finely dividing the metal valence layer electronic configuration 2+ 、Pb 2+ Binding capacity between the two, thus obtaining a representative comparison conclusion; according to the invention, the DOC samples with different molecular weights after grading are diluted to be consistent, so that the influence of DOC concentration and internal filtering effect are reduced as much as possible, and the rationality and accuracy of the diagnosis method are further improved;
(2) The method comprises the steps of measuring the three-dimensional fluorescence spectrum of DOC sample solutions with different molecular weights before and after titration experiments, and adding Cu 2+ All DOC-like and Pb addition 2+ The DOC samples of the diagnostic method are respectively subjected to parallel factor analysis, fluorescent components participating in combination and fluorescence quenching curves of the components are obtained through the parallel factor analysis, wherein two fluorescent components, namely a humus-like substance C1 and a protein-like substance C2, are mainly identified, and the accuracy and the scientificity of the diagnostic method are ensured by utilizing the adsorption effect and the ion exchange effect of organic colloid contained in the humus-like substance on metal ions and the integration and complexation effect of humic acid in the humus on elements, accurately measuring the combination capability of the metal ions and the DOC, and simultaneously carrying out the combination reaction of the metal ions and the humus-like substance; a small part of immobilized metal can also react with protein substances, the immobilized metal and the protein are subjected to chelation and then are adsorbed under the control of the main electrostatic action and the auxiliary coordination action, and the parallel factor analysis can be carried out on the immobilized metal and the protein to more comprehensively determine the binding capacity between DOC and metals with different valence-layer electronic configurations, so that the diagnosis method is more comprehensive and scientific, the influence of environmental factors is reduced as much as possible by analyzing the interaction between metal ions and substances in the surrounding environment, the undetermined metal ions are reduced, and the accuracy of the diagnosis method is improved; the invention utilizes the modified Stren-Volmer model to calculate and obtain the combination parameters of different fluorescent components and different valence-layer electron configuration metals, scientifically and accurately obtains the affinity difference between different components and metal combination, and has wide application prospect.
Drawings
FIG. 1 is a chart of PARAFAC identifying two fluorescent components of DOC of different molecular weights;
FIG. 2 is a schematic diagram showing Cu dropwise addition 2+ And Pb 2+ Fmax of post-fluorescent components C1, C2 varied.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1:
a method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence layers is characterized by comprising the following steps:
(1) Pretreatment of a water sample:
according to the principle of parallel factor analysis, 20 sampling sections are arranged in a research area, the sampling sections are collected at the position about 0.5 m below the water surface of each sampling section, a sampling bottle is pre-washed 3 times with water samples before sampling, 3 parts of parallel water samples are collected for each section and then mixed to obtain a sample, the sample is brought back to a laboratory and filtered by a 0.45 mu m glass fiber filter membrane and a vacuum filter, and then the sample is refrigerated and preserved in a dark place at 4 ℃ to obtain a pretreated water sample.
(2) DOC molecular weight fractionation:
the method comprises the steps of carrying out DOC molecular weight classification on a pretreated water sample after filtration by an ultrafiltration method, wherein an instrument is an ultrafiltration cup and an ultrafiltration membrane, respectively using 50% NaOH solution and 60% HCl solution by mass fraction before the beginning of an experiment, not pressurizing and stirring to clean the ultrafiltration membrane, then adding deionized water for pressurizing and stirring to clean the ultrafiltration membrane, ultrafiltering 100 mL ultrapure water before formal ultrafiltration, taking 10kDa ultrafiltration membrane at 25 ℃ for standby, placing 200 mL of the pretreated water sample into the ultrafiltration cup for pressurizing and filtering by using nitrogen, collecting filtrate under the membrane, adding 10 mL deionized water into the ultrafiltration cup when the pretreated water sample is remained at 50 mL, continuing pressurizing and stirring to filter out 10 mL, adding 10 mL deionized water into the ultrafiltration cup, pressurizing and stirring to filter out 10 mL, pouring out concentrate on the membrane and adding 150 mL deionized water, namely DOC solution of 10-100 kDa, adding 30 mL to the filtrate under the membrane, namely the solution of 0.1-10 kDa, sequentially filtering the DOC solution into the DOC solution of 10kDa, and obtaining four molecular weight segments of DOC-5 kDa according to the method, wherein the DOC is sequentially obtained by the steps of 10kDa and the DOC molecular weight is equal to 1kDa, and the molecular weight is obtained after four segments of molecular weight: four DOC-like solutions are prepared from 0.1-1 kDa, 1-5 kDa, 5-10 kDa and 10-100 kDa.
(3) Fluorescence quenching titration experiments:
adding deionized water into the four DOC sample solutions for dilution until the concentration of all DOC sample solutions is 1 mg.L -1 Within the range of (2), DOC-like solutions 30 and mL were each introduced into a conical flask, and 0.01 mol/L (0, 60, 120, 180, 240, 300. Mu.L) was added dropwise to the conical flask -1 The metal solutions with different valence layer electron configurations are respectively used for leading the concentration of metal ions in the conical flask to be 0, 20, 40, 60, 80 and 100 mu mol.L -1 Ignoring the concentration dilution effect, and placing all samples in a constant temperature shaking box for shaking for 24 hours in a dark place after titration to prepare an experimental solution;
(4) Three-dimensional fluorescence spectrum scanning:
taking out the experimental solution after the combination and balance, and obtaining three-dimensional fluorescence scanning data of all samples by three-dimensional fluorescence spectrum scanning and setting the excitation wavelength and emission wavelength ranges to be 220nm and 290nm respectively;
(5) Parallel factor analysis:
carrying out parallel factor analysis on three-dimensional fluorescence spectrum scanning data of all experimental solutions to obtain the maximum fluorescence intensity of different fluorescent components in each water sample;
(6) Calculation of the binding parameters:
the binding parameters between the metal and the parallel factor analysis derived fluorescent components were determined using a modified Stren-Volmer model, the calculation formula of which is as follows:
fitting a modified Stren-Volmer model: f (F) 0 /（F 0 -F）=1/（f*K*C M ）+1/f（1）。
The pore sizes of the ultrafiltration membranes in the step (2) are respectively 10kDa, 5 kDa and 1 kDa.
The metal solution in the step (3) is Cu 2+ 、Pb 2+ A solution.
The specific steps of three-dimensional fluorescence spectrum scanning in the step (4) are as follows:
(1) Three-dimensional fluorescence spectrum scanning is carried out on a fluorescence spectrum analyzer, the analyzer is matched with a 1 cm quartz cuvette, and a 150W xenon arc lamp is adopted as excitationLight source, PMT voltage=400V, signal to noise ratio 110, response time set to automatic, scan speed: 60000 nm min -1 Excitation wavelength range λEX=220 nm, interval 5 nm, emission wavelength range λEm=290 nm, interval 1 nm, scanning spectrum for instrument automatic correction;
(2) Two-dimensional scanning and three-dimensional scanning are needed to be carried out by ultrapure water before fluorescence of the test solution is measured, so that Raman scattering correction and comparison of a fluorescence spectrum are carried out on the measurement result, and the fluorescence intensity unit is R.U.
The parallel factor analysis in the step (5) comprises the following specific steps:
(1) Parallel factor analysis is carried out to obtain fluorescence components shared by a plurality of DOCs, the parallel factor analysis is carried out on the processed fluorescence data set through MATLAB R2016a software, and the number of the fluorescence components is determined through residual analysis, core consistency analysis, half-division inspection and other methods;
(2) The obtained maximum fluorescence intensity of each fluorescence component can be compared to obtain the quenching intensities of the metal ions with different valence layer electron configurations on different fluorescence components of the DOC.
Example 2:
a method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence layers is characterized by comprising the following steps:
(1) Pretreatment of a water sample:
according to the principle of parallel factor analysis, 30 sampling sections are arranged in a research area, collection is carried out at a position about 0.5 m part below the water surface of each sampling section, a sampling bottle is pre-washed 3 times with water samples before sampling, 3 parts of parallel water samples are collected for each section and then mixed to obtain samples, the samples are brought back to a laboratory and filtered by a 0.45 mu m glass fiber filter membrane and a vacuum filter, and then the samples are refrigerated and stored in a dark place at 4 ℃ to obtain a pretreated water sample;
(2) DOC molecular weight fractionation:
the method comprises the steps of carrying out DOC molecular weight classification on a filtered pretreated water sample by an ultrafiltration method, wherein an instrument is an ultrafiltration cup and an ultrafiltration membrane, respectively using a 55% NaOH solution and a 65% HCl solution with no pressurizing and stirring to clean the ultrafiltration membrane before the experiment starts, then adding deionized water for pressurizing and stirring to clean the ultrafiltration membrane, ultrafiltering 100 mL ultrapure water before the formal ultrafiltration is finished, taking a 10kDa ultrafiltration membrane at 25 ℃ for standby, placing 200 mL of the pretreated water sample into the ultrafiltration cup for pressurizing and filtering by using nitrogen, collecting an under-membrane filtrate, adding 10 mL deionized water into the ultrafiltration cup when the pretreated water sample is remained at 50 mL, continuing pressurizing and stirring to filter out 10 mL, adding 10 mL deionized water into the ultrafiltration cup, pressurizing and stirring to filter out 10 mL, pouring out a concentrated solution on the membrane and adding 150 mL deionized water, namely the DOC solution which can be considered as 10-100 kDa DOC solution, adding 30 mL to be considered as 0.1-10 kDa DOC deionized water, sequentially filtering the DOC solution which is sequentially and has a DOC of 5 kDa molecular weight of four molecular stages of 1kDa to 5 kDa according to the method, and obtaining four molecular weight stages of DOC: four DOC-like solutions are prepared from 0.1-1 kDa, 1-5 kDa, 5-10 kDa and 10-100 kDa;
(3) Fluorescence quenching titration experiments:
adding deionized water into the four DOC sample solutions for dilution until the concentration of all DOC sample solutions is 5 mg.L -1 Within the range of (2), DOC-like solutions 30 and mL were each introduced into a conical flask, and 0.01 mol/L (0, 60, 120, 180, 240, 300. Mu.L) was added dropwise to the conical flask -1 The metal solutions with different valence layer electron configurations are respectively used for leading the concentration of metal ions in the conical flask to be 0, 20, 40, 60, 80 and 100 mu mol.L -1 Ignoring the concentration dilution effect, and placing all samples in a constant temperature shaking box for shaking for 24 hours in a dark place after titration to prepare an experimental solution;
(4) Three-dimensional fluorescence spectrum scanning:
taking out the experimental solution after the combination and balance, and obtaining three-dimensional fluorescence scanning data of all samples by three-dimensional fluorescence spectrum scanning and setting the excitation wavelength and emission wavelength ranges to 300nm and 450nm respectively;
(5) Parallel factor analysis:
carrying out parallel factor analysis on three-dimensional fluorescence spectrum scanning data of all experimental solutions to obtain the maximum fluorescence intensity of different fluorescent components in each water sample;
(6) Calculation of the binding parameters:
the binding parameters between the metal and the parallel factor analysis derived fluorescent components were determined using a modified Stren-Volmer model, the calculation formula of which is as follows:
fitting a modified Stren-Volmer model: f (F) 0 /（F 0 -F）=1/（f*K*C M ）+1/f（1）。
The pore sizes of the ultrafiltration membranes in the step (2) are respectively 10kDa, 5 kDa and 1 kDa.
The metal solution in the step (3) is Cu 2+ A solution.
The specific steps of three-dimensional fluorescence spectrum scanning in the step (4) are as follows:
(1) Three-dimensional fluorescence spectrum scanning is performed on a fluorescence spectrum analyzer, the analyzer is matched with a 1 cm quartz cuvette, a 150W xenon arc lamp is adopted as an excitation light source, PMT voltage=400V, signal to noise ratio is 150, response time is set to be automatic, and scanning speed is set to be high: 60000 nm min -1 Excitation wavelength range λEX=300 nm, interval 5 nm, emission wavelength range λEm=400 nm, interval 1 nm, scanning spectrum for instrument automatic correction;
(2) Two-dimensional scanning and three-dimensional scanning are needed to be carried out by ultrapure water before fluorescence of the test solution is measured, so that Raman scattering correction and comparison of a fluorescence spectrum are carried out on the measurement result, and the fluorescence intensity unit is R.U.
The parallel factor analysis in the step (5) comprises the following specific steps:
(1) Parallel factor analysis is carried out to obtain fluorescence components shared by a plurality of DOCs, the parallel factor analysis is carried out on the processed fluorescence data set through MATLAB R2016a software, and the number of the fluorescence components is determined through residual analysis, core consistency analysis, half-division inspection and other methods;
(2) The obtained maximum fluorescence intensity of each fluorescence component can be compared to obtain the quenching intensities of the metal ions with different valence layer electron configurations on different fluorescence components of the DOC.
Example 3:
a method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence layers is characterized by comprising the following steps:
(1) Pretreatment of a water sample:
according to the principle of parallel factor analysis, 40 sampling sections are arranged in a research area, sampling is carried out at the position about 0.5 m below the water surface of each sampling section, a sampling bottle is pre-washed 3 times with water samples before sampling, 3 parts of parallel water samples are collected for each section and then mixed to obtain samples, the samples are brought back to a laboratory and filtered by a 0.45 mu m glass fiber filter membrane and a vacuum filter, and then the samples are refrigerated and stored in a dark place at 4 ℃ to obtain a pretreated water sample;
(2) DOC molecular weight fractionation:
the method comprises the steps of carrying out DOC molecular weight classification on a filtered pretreated water sample by an ultrafiltration method, wherein an instrument is an ultrafiltration cup and an ultrafiltration membrane, respectively using a NaOH solution with the mass fraction of 55% and a HCl solution with the mass fraction of 70% before the experiment starts, carrying out non-pressurized stirring to clean the ultrafiltration membrane, then adding deionized water for pressurization and stirring to clean the ultrafiltration membrane, carrying out ultrafiltration on 100 mL ultrapure water before the formal ultrafiltration, taking a 10kDa ultrafiltration membrane at 25 ℃ for standby, placing 200 mL of the pretreated water sample in the ultrafiltration cup for pressurization and membrane filtration by using nitrogen, collecting an under-membrane filtrate, adding 10 mL deionized water into the ultrafiltration cup when the pretreated water sample is remained at 50 mL, continuing to carry out pressurization and stirring to filter out 10 mL, adding 10 mL deionized water into the ultrafiltration cup, carrying out pressurization and stirring to filter out 10 mL, pouring out concentration on the membrane and adding 150 mL deionized water, namely the DOC solution which can be considered as 10-100 kDa DOC solution, adding 30 mL to be considered as 0.1-10 kDa DOC deionized water, carrying out pressurization according to the method, and sequentially filtering membranes in the order of 10kDa to 5 kDa, and obtaining four molecular weight segments of DOC: four DOC-like solutions are prepared from 0.1-1 kDa, 1-5 kDa, 5-10 kDa and 10-100 kDa;
(3) Fluorescence quenching titration experiments:
adding deionized water into the four DOC sample solutions for dilution until the concentration of all DOC sample solutions is 10 mg L -1 Within the range of (2), DOC-like solutions 30 and mL were each introduced into a conical flask, and 0.01 mol, 0, 60, 120, 180, 240, 300. Mu.L, was added dropwise to the conical flask·L -1 The metal solutions with different valence layer electron configurations are respectively used for leading the concentration of metal ions in the conical flask to be 0, 20, 40, 60, 80 and 100 mu mol.L -1 Ignoring the concentration dilution effect, and placing all samples in a constant temperature shaking box for shaking for 24 hours in a dark place after titration to prepare an experimental solution;
(4) Three-dimensional fluorescence spectrum scanning:
taking out the experimental solution after the combination and balance, and obtaining three-dimensional fluorescence scanning data of all samples by three-dimensional fluorescence spectrum scanning, wherein the excitation wavelength and the emission wavelength range are respectively 450nm and 600 nm;
(5) Parallel factor analysis:
carrying out parallel factor analysis on three-dimensional fluorescence spectrum scanning data of all experimental solutions to obtain the maximum fluorescence intensity of different fluorescent components in each water sample;
(6) Calculation of the binding parameters:
the binding parameters between the metal and the parallel factor analysis derived fluorescent components were determined using a modified Stren-Volmer model, the calculation formula of which is as follows:
fitting a modified Stren-Volmer model: f (F) 0 /（F 0 -F）=1/（f*K*C M ）+1/f（1）。
The pore sizes of the ultrafiltration membranes in the step (2) are respectively 10kDa, 5 kDa and 1 kDa.
The metal solution in the step (3) is Pb 2+ A solution.
The specific steps of three-dimensional fluorescence spectrum scanning in the step (4) are as follows:
(1) Three-dimensional fluorescence spectrum scanning is performed on a fluorescence spectrum analyzer, the analyzer is matched with a 1 cm quartz cuvette, a 150W xenon arc lamp is adopted as an excitation light source, PMT voltage=400V, signal to noise ratio 220, response time is set to be automatic, and scanning speed is set to be high: 60000 nm min -1 Excitation wavelength range λex=450 nm, interval 5 nm, emission wavelength range λem=600 nm, interval 1 nm, scanning spectrum for instrument auto-calibration;
(2) Two-dimensional scanning and three-dimensional scanning are needed to be carried out by ultrapure water before fluorescence of the test solution is measured, so that Raman scattering correction and comparison of a fluorescence spectrum are carried out on the measurement result, and the fluorescence intensity unit is R.U.
The parallel factor analysis in the step (5) comprises the following specific steps:
(1) Parallel factor analysis is carried out to obtain fluorescence components shared by a plurality of DOCs, the parallel factor analysis is carried out on the processed fluorescence data set through MATLAB R2016a software, and the number of the fluorescence components is determined through residual analysis, core consistency analysis, half-division inspection and other methods;
(2) The obtained maximum fluorescence intensity of each fluorescence component can be compared to obtain the quenching intensities of the metal ions with different valence layer electron configurations on different fluorescence components of the DOC.
The detection method comprises the following steps:
the DOC is selected from park landscape water, the electronic configuration of different valence layers is selected from d area and p area, and the corresponding metal ions are Cu respectively 2+ And Pb 2+ 。
(1) Fluorescent component identified in water sample after combination
After the titration experiment is finished, cu is added 2+ All DOC-like and Pb addition 2+ Two fluorescent components were identified (FIG. 1), humus-like substance C1 (Ex/Em=245 (270)/436 nm) and protein-like substance C2 (Ex/Em=225 (285)/347 nm), respectively, for parallel factor analysis of all DOC samples, respectively. Table 1 lists the types and wavelength ranges of the two fluorescent components and their comparison with the results of previous studies.
The results of the fluorescent component show that Cu 2+ And Pb 2+ The typical d-region and p-region metals, when bound to a DOC, participate in the binding of the same fluorescent components, and do not change with the electronic configuration of different valence layers.
(2) Judgment of binding capacity of different valence layer electronic configuration metals and DOC
a. Determining binding capacity difference by comparing fluorescence quenching degree of fluorescent components
Cu 2+ 、Pb 2+ The reaction with both components C1 and C2 shows fluorescence quenching effect. Wherein Cu is 2+ For any molecular weight rangeQuenching effect generated by two fluorescent components in DOC is stronger than Pb 2+ 。
The quenching degree of the fluorescent component indicates that Cu is used for 2+ And Pb 2+ The representative d-zone and p-zone metals both bind to two fluorescent components in park landscape water and cause quenching of DOC fluorescence, but the d-zone metals (Cu 2+ ) The two fluorescent components in DOC are quenched to a degree higher than that of the p-region metal (Pb 2+ ) The combination capability of the metal in the d area and two fluorescent components in the DOC of the park landscape water body is stronger than that of the metal in the p area.
Judging the difference of binding capacities by comparing the binding parameters of the fluorescent component and the electronic configuration metals of different valence layers
Two fluorescent components in DOC with different molecular weights and Cu 2+ Are all greater than Pb in binding stability constant 2+ And both heavy metals have the largest complexation stability constant when complexed with a < 1kDa DOC. The result shows that Cu is used in the DOC combination process with the park landscape water body 2+ The represented d-block metal has a higher binding capacity with two fluorescent components than Pb 2+ Is a representative p-region metal. Meanwhile, the difference of the binding capacity of the different valence layer electron configuration metals and the DOC is not influenced by the molecular weight of the DOC, that is, the binding capacity of the d-region metal and the DOC is stronger than that of the p-region metal in any molecular weight section.
TABLE 1 location of fluorescent components and comparison with previous studies
TABLE 2 DOC to different valence shell electron configuration metal bindinglgK、f、R 2 Value of
In the experiment, only one metal ion is selected for the electronic configuration (p region and d region) of the different valence layers in the embodiment 2 and the embodiment 3, and the research result shows that when the metals of the two different valence layers are combined with the DOC of the park landscape water body, the combination components are the same, but the combination capability of the two different components is different, wherein the combination capability of the d region metal to the two fluorescent components in the DOC is stronger than that of the p region metal; example 1 uses a two metal ion mixing test, when the DOC is combined with a park landscape water body, the combination ability of the same components but different components is consistent with that of examples 2 and 3, namely, the difference of the combination ability of different valence layer electron configuration metals and DOC is not influenced by the molecular weight of DOC, and meanwhile, the d-zone metal and DOC are shown to be stronger than the p-zone metal no matter what molecular weight section.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (9)
1. A method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence layers is characterized by comprising the following specific steps:
(1) Pretreatment of a water sample:
according to the principle of parallel factor analysis, 20-40 sampling sections are arranged in a research area, collection is carried out at a position about 0.5 m below the water surface of each sampling section, a sampling bottle is pre-washed 3 times with water samples before sampling, 3 parts of parallel water samples are collected for each section and then mixed to obtain a sample, the sample is brought back to a laboratory and filtered by a glass fiber filter membrane with the diameter of 0.45 mu m and a vacuum suction filter, and then the sample is refrigerated and stored in a dark place at the temperature of 4 ℃ to obtain a pretreated water sample;
(2) DOC molecular weight fractionation:
the method comprises the steps of carrying out DOC molecular weight classification on a filtered pretreated water sample by an ultrafiltration method, wherein an instrument is an ultrafiltration cup and an ultrafiltration membrane, respectively using 50-60% NaOH solution and 60-70% HCl solution by mass fraction before the experiment starts, cleaning the ultrafiltration membrane without pressurizing and stirring, then adding deionized water for pressurizing and stirring to clean the ultrafiltration membrane, ultrafiltering 100 mL ultrapure water before formal ultrafiltration is carried out, taking a 10kDa ultrafiltration membrane at 25 ℃ for standby, placing 200 mL of the pretreated water sample into the ultrafiltration cup for pressurizing and filtering by nitrogen, collecting filtrate under the membrane, adding 10 mL deionized water into the ultrafiltration cup when the pretreated water sample is remained at 50 mL, continuing pressurizing and stirring to filter 10 mL, adding 10 mL deionized water into the ultrafiltration cup, pressurizing and stirring to filter 10 mL, pouring out concentrate on the membrane and adding 150 mL deionized water, namely the DOC solution which is 10-100 kDa, and adding 30 mL deionized water into the membrane, namely DOC solution which is 0.01-10 kDa, sequentially filtering membranes according to the method, and sequentially obtaining four DOC molecular weight segments of 1kDa and 5 kDa: four DOC-like solutions are prepared from 0.1-1 kDa, 1-5 kDa, 5-10 kDa and 10-100 kDa;
(3) Fluorescence quenching titration experiments:
adding deionized water into the four DOC sample solutions for dilution until the concentration of all DOC sample solutions is 1-mg.L -1 Within the range of (2), DOC-like solutions 30 and mL were each introduced into a conical flask, and 0.01 mol/L (0, 60, 120, 180, 240, 300. Mu.L) was added dropwise to the conical flask -1 The metal solutions with different valence layer electron configurations are respectively used for leading the concentration of metal ions in the conical flask to be 0, 20, 40, 60, 80 and 100 mu mol.L -1 Ignoring the concentration dilution effect, and placing all samples in a constant temperature shaking box for shaking for 24 hours in a dark place after titration to prepare an experimental solution;
(4) Three-dimensional fluorescence spectrum scanning:
taking out the experimental solution after the combination and balance, and obtaining three-dimensional fluorescence scanning data of all samples by three-dimensional fluorescence spectrum scanning, wherein the excitation wavelength and the emission wavelength range are respectively 220-450 nm and 290-600 nm;
(5) Parallel factor analysis:
carrying out parallel factor analysis on three-dimensional fluorescence spectrum scanning data of all experimental solutions to obtain the maximum fluorescence intensity of different fluorescent components in each water sample;
(6) Calculation of the binding parameters:
the binding parameters between the metal and the parallel factor analysis derived fluorescent components were determined using a modified Stren-Volmer model, the calculation formula of which is as follows:
fitting a modified Stren-Volmer model: f (F) 0 /（F 0 -F）=1/（f*K*C M ）+1/f（1）。
2. The method for diagnosing the binding capacity of soluble organic carbon and electronic-configured metal of different valence shells according to claim 1, wherein the pore size of the ultrafiltration membrane in the step (2) is 10kDa, 5 kDa and 1kDa, respectively.
3. The method for diagnosing the binding capacity of soluble organic carbon and electron configuration metals of different valence shells according to claim 1, wherein the metal solution in the step (3) is Cu 2+ 、Pb 2+ A solution.
4. The method for diagnosing the binding capacity of the soluble organic carbon and the electronic configuration metal of the different valence shells according to claim 1, wherein the specific steps of three-dimensional fluorescence spectrum scanning in the step (4) are as follows:
(1) Three-dimensional fluorescence spectrum scanning is carried out on a fluorescence spectrum analyzer, the analyzer is matched with a 1 cm quartz cuvette, a 150W xenon arc lamp is adopted as an excitation light source, PMT voltage=400V, signal to noise ratio is 110-220, response time is set to be automatic, and scanning speed is set to be high: 60000 nm min -1 Excitation wavelength range λEX=220-450 nm, interval 5 nm, emission wavelength range λEm=290-600 nm, interval 1 nm, scanning spectrum to perform instrument automatic correction;
(2) Two-dimensional scanning and three-dimensional scanning are needed to be carried out by ultrapure water before fluorescence of the test solution is measured, so that Raman scattering correction and comparison of a fluorescence spectrum are carried out on the measurement result, and the fluorescence intensity unit is R.U.
5. The method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence shells according to claim 1, wherein the specific steps of the parallel factor analysis in the step (5) are as follows:
(1) Parallel factor analysis is carried out to obtain fluorescence components shared by a plurality of DOCs, the parallel factor analysis is carried out on the processed fluorescence data set through MATLAB R2016a software, and the number of the fluorescence components is determined through residual analysis, core consistency analysis, half-division inspection and other methods;
(2) The obtained maximum fluorescence intensity of each fluorescence component can be compared to obtain the quenching intensities of the metal ions with different valence layer electron configurations on different fluorescence components of the DOC.
6. The method for diagnosing the binding capacity of soluble organic carbon and electron configuration metals of different valence shells according to claim 1, wherein the modified Stren-Volmer model in the step (6) comprises:
F 0 the fluorescence intensity at the beginning of titration, i.e., when no metal is added, F is the metal concentration C M mol·L -1 Fluorescence intensity under.
7. The method for diagnosing the binding capacity of soluble organic carbon and electron configuration metals of different valence shells according to claim 1, wherein the modified Stren-Volmer model in the step (6) comprises:
the ratio f of the conditional stability constant K to the fluorescent group involved in metal ion coordination was logarithmic for the conditional stability constant K to give a binding stability constant lgK.
8. The method for diagnosing the binding capacity of soluble organic carbon and electronic configuration metals of different valence shells according to claim 1, wherein the numerical relationship in the modified Stren-Volmer model in the step (6) is as follows:
(1) Calculating the proportion f of the fluorescent groups involved in metal ion coordination through 1/f;
(2) The binding stability constant lgK is obtained by calculating the conditional stability constant K by 1/f×k and taking the logarithm of the conditional stability constant K.
9. The method for diagnosing the binding capacity of a soluble organic carbon with a metal having an electron configuration of a different valence shell according to claim 8, wherein the lgK value in the step (2) characterizes the difference of the binding capacities of the metal ions having an electron configuration of a different valence shell with DOC.
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