DGT method for simultaneous determination of phosphorus and sulfur content based on hyperspectral imaging technology

Abstract

The present invention discloses a DGT method for synchronously determining phosphorus and sulfur content based on hyperspectral imaging technology, and relates to the technical field of phosphorus and sulfur content determination, through step one, DGT device assembly; step two, phosphorus and sulfur absorption; step three, membrane coloring; step four, taking pictures; step five, establishment of phosphorus calibration curve; step six, establishment of sulfur calibration curve. It solves the problem that the current existing technology cannot realize the synchronous two-dimensional determination of P and S (-II); the LA-ICP-MS analysis cost is high, the steps are complicated, and there is a lack of a cheap and simple method for synchronously determining P and S (-II) by combining DGT and other technologies. After the fixed film after color development is photographed with a hyperspectral camera, the software is used to separate the colors of phosphorus and sulfur and obtain their respective abundances, and then the calibration curve of abundance and cumulative amount established in advance is used to convert the obtained abundance into cumulative amount, so as to realize the synchronous two-dimensional analysis of phosphorus / sulfur in the environment, and the analysis result is consistent with the result obtained by the CID method, and the method is simple and fast to operate.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphorus and sulfur content determination, and in particular to a DGT method for synchronously determining phosphorus and sulfur contents based on hyperspectral imaging technology. Background Art

[0002] Thin-film diffusion gradient technology (DGT) has been widely used to determine various elements in the environment. Given the high spatial heterogeneity of sediments, high-resolution two-dimensional imaging can provide a better understanding of biogeochemical processes. Simultaneous determination of phosphorus (P) and sulfur (S) is crucial for understanding the relationship between them.

[0003] To date, DGT combined with computer imaging densitometry (CID) has achieved two-dimensional determination of P and S(-II). The CID method is simple, rapid, and easy to use, but it cannot achieve simultaneous two-dimensional determination of P and S(-II). Furthermore, DGT combined with inductively coupled plasma mass spectrometry (LA-ICP-MS) has achieved simultaneous two-dimensional determination of P and S(-II), but LA-ICP-MS analysis is expensive and complex. Currently, there are no studies on inexpensive and simple methods combining DGT with other techniques for the simultaneous determination of P and S(-II).

[0004] Therefore, the present invention proposes a DGT method for synchronously determining phosphorus and sulfur contents based on hyperspectral imaging technology to solve the above problems. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a DGT method for the simultaneous determination of phosphorus and sulfur content based on hyperspectral imaging technology, which solves the problems that the current existing technology cannot achieve simultaneous two-dimensional determination of P and S(-II); LA-ICP-MS analysis has high costs and complex steps, and lacks a cheap and simple method for combining DGT and other technologies for the simultaneous determination of P and S(-II).

[0006] To achieve the above objectives, the present invention is implemented by the following technical solution: a DGT method for synchronously determining phosphorus and sulfur content based on hyperspectral imaging technology, specifically comprising the following steps:

[0007] Step 1: DGT device assembly: assemble the phosphorus-sulfur synchronous DGT fixed membrane into a DGT device;

[0008] Step 2: Phosphorus and sulfur absorption: The DGT device is placed in a medium containing phosphorus and sulfur. The fixed membrane contacts the medium containing phosphorus and sulfur, so that phosphorus and sulfur are enriched on the surface of the fixed membrane, forming a phosphorus and sulfur synchronous DGT fixed membrane.

[0009] Step 3: Membrane coloring: Take out the phosphorus-sulfur synchronous DGT fixed membrane, add color developer, and develop color under constant temperature;

[0010] Step 4: Take photos: Scan the colored phosphorus-sulfur synchronous DGT fixed film using a synchronous detection device, and process the scanned image using image processing software to obtain the abundance values ​​of phosphorus and sulfur;

[0011] Step 5. Establishing a phosphorus calibration curve: Following the methods of steps 1 and 2, the fixed membrane is placed in a set of phosphorus solutions of known concentrations to absorb phosphorus. Each concentration includes at least two replicate samples. After one replicate sample is extracted with NaOH, the phosphorus concentration in the extract is determined using the phosphomolybdenum blue colorimetric method, and the cumulative amount of phosphorus on the surface of the fixed membrane is calculated. For the other replicate sample, the image obtained by photographing is processed using software in the same manner as steps 3 and 4 to obtain the phosphorus abundance value. The phosphorus abundance value on the fixed membrane in the same phosphorus solution and the cumulative amount of phosphorus are then fitted to form a calibration curve.

[0012] Step 6. Establish a sulfur calibration curve: Following the methods of Steps 1 and 2, place the fixed membrane in a set of sulfur solutions of known concentrations to absorb sulfur. Each concentration includes at least two replicates. For one replicate, measure the accumulated sulfur on the fixed membrane surface using computer imaging densitometry. For the other replicate, use the same methods as Steps 3 and 4 to process the image obtained using software to determine the sulfur abundance value. The sulfur abundance values ​​and accumulated sulfur on the fixed membrane in the same sulfur solution are then fitted to form a calibration curve.

[0013] Furthermore, the synchronous detection device includes a hyperspectral camera, a reference white panel, and a supplementary light source for fill light.

[0014] Furthermore, the DGT fixed membrane is based on polyacrylamide and loaded with zirconium oxide (Zr-oxide) as a phosphorus adsorption material and silver iodide (AgI) as a sulfur adsorption material.

[0015] Furthermore, in step three, the color developer is a color developer used in the phosphomolybdenum blue colorimetric method.

[0016] Furthermore, in the step 4, the resolution of scanning the surface of the phosphorus-sulfur synchronous DGT fixed membrane with a hyperspectral camera is set to 50×50 μm per pixel to 100×100 μm per pixel.

[0017] Furthermore, in step three, the constant temperature is 35° C. and the color development time is 45 minutes.

[0018] Furthermore, in step 4, the image processing software is ENVI, which is used to separate the colors of the image and obtain the abundance of phosphorus and sulfur respectively.

[0019] Furthermore, the DGT fixed membrane is an improved ZrO-AgI polyacrylamide gel film, and the particle sizes of Zr-oxide and AgI particles uniformly distributed on the membrane surface are no more than 2 μm.

[0020] Beneficial effects

[0021] The present invention provides a DGT method for simultaneous determination of phosphorus and sulfur content based on hyperspectral imaging technology. Compared with existing technologies, it has the following advantages:

[0022] 1. A DGT method for simultaneous determination of phosphorus and sulfur content based on hyperspectral imaging technology, comprising steps 1: DGT device assembly; 2: phosphorus and sulfur absorption; 3: membrane staining; 5: establishment of a phosphorus calibration curve; and 6: establishment of a sulfur calibration curve. This method addresses the current limitations of existing technologies for simultaneous two-dimensional determination of phosphorus and sulfur(-II); the high cost and complex steps of LA-ICP-MS analysis; and the lack of a cost-effective and simple method combining DGT with other techniques for simultaneous determination of phosphorus and sulfur(-II).

[0023] 2. The DGT method for synchronously determining phosphorus and sulfur content based on hyperspectral imaging technology. After photographing the colored fixed film with a hyperspectral camera, the present invention uses software to separate the colors of phosphorus and sulfur and obtain their respective abundances. Then, using a pre-established calibration curve of abundance and cumulative amount, the obtained abundance is converted into cumulative amount, achieving simultaneous two-dimensional analysis of phosphorus / sulfur in the environment. The analysis results are consistent with those obtained by the CID method, and the method is simple and fast to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of RGB imaging of the present invention;

[0025] Figure 2 Schematic diagram of hyperspectral imaging of the present invention;

[0026] Figure 3 This is a diagram showing the principle of hybrid pixel decomposition according to the present invention;

[0027] Figure 4 Scanning diagram of fixed film adsorbed with phosphorus and sulfur for invention;

[0028] Figure 5 The spectral reflectance curves of phosphorus and sulfur obtained by the present invention using the hyperspectral imaging technology;

[0029] Figure 6 This is a scan of the fixed membrane that only adsorbs S(-II) of the present invention;

[0030] Figure 7 This is a scan of the fixed membrane that simultaneously adsorbs S(-II) and P according to the present invention;

[0031] Figure 8 This is a sulfur calibration curve diagram of the present invention;

[0032] Figure 9 This is a scan of the fixed membrane that only adsorbs P in the present invention;

[0033] Figure 10 Schematic diagram of the fixed membrane that simultaneously adsorbs S(-II) and P according to the present invention;

[0034] Figure 11 This is a phosphorus calibration curve diagram of the present invention;

[0035] Figure 12 This is a comparison chart of phosphorus / sulfur fluxes calculated by the HSI method and the CID method of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] like Figure 1-12 The present invention provides a technical solution: a DGT method for synchronously determining phosphorus and sulfur content based on hyperspectral imaging technology, which specifically includes the following steps:

[0038] Step 1: DGT device assembly: assemble the phosphorus-sulfur synchronous DGT fixed membrane into a DGT device;

[0039] Step 2: Phosphorus and sulfur absorption: The DGT device is placed in a medium containing phosphorus and sulfur. The fixed membrane contacts the medium containing phosphorus and sulfur, and is immersed in a phosphorus solution and a sulfur solution (concentration range is 0-1000 μg / L). After immersion for 24 hours, phosphorus and sulfur are enriched on the surface of the fixed membrane, forming a phosphorus-sulfur synchronous DGT fixed membrane.

[0040] Step 3, membrane coloring: the phosphorus-sulfur synchronous DGT fixed membrane is taken out, a color developer is added, and color is developed under constant temperature conditions. The color developer can be the color developer used in the phosphomolybdenum blue colorimetric method, which is prepared by dissolving ammonium molybdate stock solution (20g ammonium molybdate and 0.5g potassium antimony tartrate separately and adding 194.6mL concentrated sulfuric acid to 1L) and ascorbic acid in a ratio of 100mL:1.5g and then diluting 10 times to obtain a 1:10 color developer. The color development temperature is controlled at 35°C and the color development time is 45min.

[0041] Step 4. Take photos: Use a synchronous detection device to scan the colored phosphorus-sulfur synchronous DGT fixed film, and process the scanned image with image processing software to obtain the abundance values ​​of phosphorus and sulfur. Based on HSI technology, use a hyperspectral camera to scan the colored film, and the resolution can be set to 50×50μm per pixel to 100×100μm per pixel. Use software such as ENVI to separate the colors of the image obtained by taking photos, and obtain the abundance of phosphorus and sulfur respectively. After processing with ENVI software, the following three end member spectra are obtained: a) Background end member: reference white panel + blank ZrO-AgI fixed film; b) S(-II) end member: fixed film enriched with the highest S(-II) content; c) P end member: fixed film enriched with the highest P content. Then, use the previously established calibration curves of phosphorus accumulation and abundance, and sulfur accumulation and abundance to convert the obtained abundance into phosphorus and sulfur accumulation;

[0042] Step 5. Establishing a phosphorus calibration curve: Following the methods of steps 1 and 2, the fixed membrane is placed in a set of phosphorus solutions of known concentrations to absorb phosphorus. Each concentration includes at least two replicate samples. After one replicate sample is extracted with NaOH, the phosphorus concentration in the extract is determined using the phosphomolybdenum blue colorimetric method, and the cumulative amount of phosphorus on the surface of the fixed membrane is calculated. For the other replicate sample, the image obtained by photographing is processed using software in the same manner as steps 3 and 4 to obtain the phosphorus abundance value. The phosphorus abundance value on the fixed membrane in the same phosphorus solution and the cumulative amount of phosphorus are then fitted to form a calibration curve.

[0043] Step 6: Establishing a sulfur calibration curve: Following the methods of steps 1 and 2, the fixed membrane is placed in a set of sulfur solutions of known concentrations to absorb sulfur. Each concentration contains at least two replicate samples. For one replicate sample, the accumulated sulfur on the fixed membrane surface is measured using computer imaging densitometry. For the other replicate sample, the image obtained is processed using software in the same manner as steps 3 and 4 to obtain a sulfur abundance value. The sulfur abundance values ​​on the fixed membrane in the same sulfur solution are then fitted to the accumulated sulfur values ​​to form a calibration curve. This method addresses the current limitations of existing technologies for simultaneous two-dimensional determination of phosphorus and sulfur (-II). LA-ICP-MS analysis is costly, complex, and lacks inexpensive and simple methods for simultaneous determination of phosphorus and sulfur (-II) by combining DGT and other techniques. The present invention photographs the developed fixed membrane with a hyperspectral camera, then uses software to separate the phosphorus and sulfur colors and determine their respective abundances. Using a pre-established calibration curve for abundance versus accumulation, the resulting abundances are converted to cumulative amounts. This achieves simultaneous two-dimensional analysis of phosphorus and sulfur in the environment. The analytical results are consistent with those obtained using CID, and the method is simple and rapid to operate.

[0044] In an embodiment of the present invention, the synchronous detection device includes a hyperspectral camera, a reference white panel, and an enhanced light source for fill light. The camera head of the hyperspectral camera is facing the fixed film and the reference white panel. The enhanced light source is arranged near the hyperspectral camera. The DGT fixed film is placed face up on black plastic cardboard and faces the camera lens.

[0045] In the embodiment of the present invention, the DGT fixed membrane is based on polyacrylamide and loaded with zirconium oxide (Zr-oxide) as a phosphorus adsorption material and silver iodide (AgI) as a sulfur adsorption material.

[0046] In the embodiment of the present invention, in step three, the color developer is a color developer used in the phosphomolybdenum blue colorimetric method.

[0047] In the embodiment of the present invention, in step 4, the resolution of scanning the surface of the phosphorus-sulfur synchronous DGT fixed film with a hyperspectral camera is set to 50×50 μm per pixel to 100×100 μm per pixel.

[0048] In the embodiment of the present invention, in step 3, the constant temperature is 35° C. and the color development time is 45 minutes.

[0049] In the embodiment of the present invention, in step 4, the image processing software is ENVI, which is used to separate the colors of the image and obtain the abundance of phosphorus and sulfur respectively.

[0050] In the embodiment of the present invention, the DGT fixed membrane is an improved ZrO-AgI polyacrylamide gel film, and the particle sizes of Zr-oxide and AgI particles uniformly distributed on the membrane surface are no greater than 2 μm.

[0051] The embodiment of the present invention also provides a sediment application of the DGT method for synchronously determining phosphorus and sulfur content based on hyperspectral imaging technology, which specifically includes the following steps:

[0052] (1) Collect sediment column samples and the corresponding overlying water from the target water body, slice the sediment at intervals of depth, mix the sediments at the same depth thoroughly, and screen out large particles;

[0053] (2) Place the sediment in a transparent box according to the original depth, place the transparent box in a water tank, add overlying water, and incubate for at least 1 week;

[0054] (3) A Zr-oxide fixed film and a ZrO-AgI fixed film are attached to both sides of a stainless steel sheet, wherein the stainless steel sheet has a length of 10 to 15 cm, a width of 2 to 3 cm, and a thickness of 1 to 3 mm.

[0055] (4) The stainless steel sheet in step (3) was inserted into the sediment and placed for more than 24 hours. The stainless steel sheet was removed and the two-dimensional distribution of the P flux was obtained by the CID method for the Zr-oxide fixed membrane. For the ZrO-AgI fixed membrane, the two-dimensional distribution of the S(-II) flux was first obtained by the CID method, and then the two-dimensional distribution of the P and S(-II) fluxes was obtained by the HSI method.

[0056] The present invention specifically introduces the process of measuring the phosphorus / sulfur synchronous distribution information in water sediments by the present method in detail through the following examples:

[0057] (1) Collect six sediment columns (9 cm in diameter, 40 cm in length) and the overlying water from Meiliang Bay in the northern part of Taihu Lake and transport them to the laboratory within 24 hours. Slice the sediments at 2 cm intervals according to depth, and thoroughly mix the sediments at the same depth. Sieve the sediments with a 0.6 mm pore size sieve to remove large particles.

[0058] (2) The sediments were then stacked in transparent plexiglass boxes according to their original depth. The transparent plexiglass boxes were then placed in a water tank containing water from the target water area (three groups of experiments can be arranged), and a 45 cm deep layer of filtered lake water was ensured above the sediments.

[0059] (3) A Zr-oxide fixed film and a ZrO-AgI fixed film are respectively attached to both sides of a stainless steel sheet, wherein the stainless steel sheet has a length of 10 to 15 cm, a width of 2 to 3 cm, and a thickness of 1 to 3 mm.

[0060] (4) Insert the stainless steel sheet (3) into the sediment and place it for more than 24 hours. Remove the stainless steel sheet and use the CID method to obtain the two-dimensional distribution of the P flux for the Zr-oxide fixed film. For the ZrO-AgI fixed film, first use the CID method to obtain the two-dimensional distribution of the S(-II) flux, and then use the HSI method to obtain the two-dimensional distribution of the P and S(-II) fluxes.

[0061] (5) The synchronous two-dimensional distribution of phosphorus / sulfur at the Meiliang Bay sampling point in the northern part of Taihu Lake, measured by the DGT method of the present invention for synchronous determination of phosphorus and sulfur content based on hyperspectral imaging technology, was compared with the data obtained by the CID method.

[0062] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0063] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A DGT method for simultaneous determination of phosphorus and sulfur content based on hyperspectral imaging (HSI) technology, characterized in that: The specific steps include: Step 1, DGT device assembly: assemble the phosphorus-sulfur synchronous DGT fixed membrane into a DGT device; Step 2: Phosphorus and sulfur absorption: The DGT device is placed in a medium containing phosphorus and sulfur, and the fixed membrane contacts the medium containing phosphorus and sulfur, so that phosphorus and sulfur are enriched on the surface of the fixed membrane to form a phosphorus and sulfur synchronous DGT fixed membrane; Step 3: Membrane coloring: Take out the phosphorus-sulfur synchronous DGT fixed membrane, add a color developer, and color it under constant temperature; Step 4: Take photos: Use a synchronous detection device to scan the colored phosphorus-sulfur synchronous DGT fixed film, and process the scanned image with image processing software to obtain the abundance values ​​of phosphorus and sulfur; Step 5, establishing a phosphorus calibration curve: according to the method of step 1 and step 2, the fixed membrane is placed in a group of phosphorus solutions with known concentrations to absorb phosphorus, each concentration includes at least two parallel samples, one parallel sample is extracted with NaOH, and the concentration of phosphorus in the extract is determined by phosphomolybdenum blue colorimetry, and the cumulative amount of phosphorus on the surface of the fixed membrane is calculated, and the other parallel sample is processed by software using the same method as step 3 and step 4 to obtain the abundance value of phosphorus, and then the abundance value of phosphorus on the fixed membrane in the same phosphorus solution and the cumulative amount of phosphorus are fitted into a calibration curve; Step 6. Establishment of sulfur calibration curve: According to the method of step 1 and step 2, the fixed membrane is placed in a set of sulfur solutions with known concentrations to absorb sulfur, each concentration includes at least two parallel samples, one of which is used to measure the accumulated amount of sulfur on the surface of the fixed membrane using computer imaging density measurement technology, and the other parallel sample is used to process the image obtained by taking pictures using software according to the same method as step 3 and step 4 to obtain the abundance value of sulfur, and then the abundance value of sulfur on the fixed membrane in the same sulfur solution and the accumulated amount of sulfur are fitted into a calibration curve; The DGT fixed membrane is based on polyacrylamide and loaded with zirconium oxide, a phosphorus adsorbent, and silver iodide, a sulfur adsorbent. The DGT fixed membrane is an improved ZrO-AgI polyacrylamide gel film. The color developer used in the phosphomolybdic blue colorimetric method is prepared by dissolving ammonium molybdate stock solution and ascorbic acid in a ratio of 100 mL:1.5 g and then diluting 10 times to obtain a 1:10 color developer. The ammonium molybdate stock solution is prepared by dissolving 20 g of ammonium molybdate and 0.5 g of potassium antimony tartrate separately and then adding 194.6 mL of concentrated sulfuric acid to make the volume 1 L. The color development temperature is controlled at 35°C and the color development time is 45 min. Based on HSI technology, a hyperspectral camera is used to scan the colored film. The resolution can be set to 50×50μm to 100×100μm per pixel. The color of the image obtained by taking a photo is separated by software to obtain the abundance of phosphorus and sulfur respectively. After processing with ENVI software, the following three end member spectra are obtained: a) Background end member: reference white panel + blank ZrO-AgI fixed film; b) S(-II) end member: fixed film enriched with the highest S(-II) content; c) P end member: fixed film enriched with the highest P content; The synchronous detection device includes a hyperspectral camera, a reference white panel, and a supplementary light source for fill light. The camera head of the hyperspectral camera is facing the fixed film and the reference white panel. The supplementary light source is arranged near the hyperspectral camera. The DGT fixed film is placed face up on black plastic cardboard and faces the camera lens.

Images