Imaging device and method for characterizing degradation of organic phosphorus by active oxygen in soil sediment

Abstract

The invention provides an imaging device and method for characterizing degradation of organic phosphorus by active oxygen in soil sediment, the imaging device comprises a diffusion film, a fixing film and a film fixing frame, the diffusion film is attached to the upper portion of the fixing film, the diffusion film is a film formed by agarose gel, and iron oxide particles containing organic phosphorus are dispersed in the diffusion film; the fixing film is a thin film formed by second gel, a phosphorus adsorbent is dispersed in the fixing film, and the second gel is agarose gel or cross-linked gel of polyacrylamide and agarose. According to the method, a two-dimensional imaging gel film is constructed, iron oxide particles containing organic phosphorus are utilized, and the efficiency difference of active oxygen generated on an iron oxide interface for degrading free-state organic phosphorus and adsorbed-state organic phosphorus is represented in an imaging mode. And the imaging control precision is controlled in a submillimeter range. The device disclosed by the invention can represent the process of reducing and releasing organic phosphorus by iron ore in soil and sediments, and reproduces the microcosmic rule of dynamic degradation of organic phosphorus mediated by active oxygen to the greatest extent.

Description

Technical Field

[0001] The present invention belongs to the fields of environmental science and geochemistry, and specifically relates to an imaging device and method for characterizing the degradation of organic phosphorus by active oxygen in soil and sediments, which can provide technical support for the study of phosphorus cycle in the fields of environmental science and geochemistry. Background Art

[0002] Phosphorus in soils and sediments is a crucial biogenic element, and its bioavailability is directly related to food security and water eutrophication. In addition to the highly bioavailable orthophosphate, soils and sediments also contain significant amounts of organic phosphorus. Although organic phosphorus cannot be directly bioavailable, it can be converted to orthophosphate by biological phosphatases. Traditional research on organic phosphorus mineralization in soils and sediments has primarily focused on biotransformation processes such as enzymatic degradation of organic phosphorus. Currently, research on the abiotic mineralization of organic phosphorus driven by reactive oxygen species (ROS) is scarce. Under redox fluctuations, reduced iron ore and organic matter in soils and sediments can activate oxygen to generate large amounts of reactive oxygen species (ROS) (superoxide radicals, hydrogen peroxide, and hydroxyl radicals). These highly oxidizing ROS pose a potential risk of degrading organic phosphorus. Elucidating the ROS-mediated degradation of organic phosphorus in soils and sediments is of great scientific significance for assessing phosphorus bioavailability and improving phosphorus cycling mechanisms.

[0003] Frequent water level fluctuations at the sediment (soil)-water interface expose clay minerals near the interface to a fluctuating redox environment. During flooding, anaerobic reduction of iron ore in the soil and sediments releases surface-adsorbed organic phosphorus. During drainage and drought, dissolved ferrous iron ore oxidizes upon contact with air to form iron hydroxide precipitates, which again adsorb and fix the organic phosphorus in solution. Redox fluctuations at the sediment (soil)-water interface also generate reactive oxygen species (ROS). The efficiency of ROS degradation varies significantly between dissolved and adsorbed ROS. Accurately detecting the efficiency of ROS degradation at the iron ore interface under redox fluctuations remains a significant challenge, both domestically and internationally. Summary of the Invention

[0004] The object of the present invention is to provide an imaging device and method for characterizing the difference in efficiency of reactive oxygen species in soil sediments in degrading dissolved and adsorbed organic phosphorus.

[0005] The above-mentioned purpose of the present invention is achieved like this: An imaging device for characterizing the degradation of organic phosphorus by active oxygen in soil sediments comprises a diffusion membrane, a fixed membrane and a film fixing frame for fixing the diffusion membrane and the fixed membrane. The diffusion membrane is arranged on top of the fixed membrane. The diffusion membrane is a thin film formed by a first gel, iron oxide particles containing organophosphorus are dispersed in the first gel, and the first gel is an agarose gel; The fixed membrane is a thin film formed by a second gel, a phosphorus adsorbent is dispersed in the second gel, and the second gel is agarose gel or a cross-linked gel of polyacrylamide and agarose.

[0006] Preferably, the iron oxides containing organophosphorus come from the soil or sediment to be tested.

[0007] Preferably, the phosphorus adsorbent is selected from nanoparticles of La(OH)3, ZrO2 or CaCO3.

[0008] Preferably, the diffusion membrane is prepared by the following method: A mixed solution of acrylamide and agarose is injected into a mold, and dried iron oxide particles containing organic phosphorus are added and evenly dispersed. Then, an initiator and a catalyst are added to solidify the agarose solution to obtain the diffusion membrane.

[0009] Preferably, the concentration of the agarose solution is 0.3-5% by mass.

[0010] Preferably, the mold is a culture dish.

[0011] Preferably, the uniform dispersion method is ultrasonic treatment.

[0012] Preferably, the uniform dispersion is carried out at 40-60°C.

[0013] The thickness of the diffusion membrane is 2-10 mm.

[0014] Preferably, the fixed membrane is prepared by the following method: A phosphorus adsorbent is added to a mixed solution containing acrylamide, N,N-bisacrylamide, and agarose, and uniformly dispersed to obtain a gel solution. An initiator and a catalyst are then added to the gel solution, and the coagulation solution is injected into a mold and solidified to obtain the fixed film.

[0015] Preferably, in the gel solution, the mass fraction of the phosphorus adsorbent is 1-10%.

[0016] Preferably, the initiator is ammonium persulfate.

[0017] Preferably, the catalyst is TEMED.

[0018] Preferably, the solvent of the gel solution is water.

[0019] A second object of the present invention is to provide a method for characterizing the degradation of organic phosphorus by active oxygen in soil sediments, comprising the following steps: (1) Using the imaging device for characterizing the degradation of organic phosphorus by active oxygen in soil sediments, the upper surface of the diffusion membrane is uniformly contacted with a reducing substance in an oxygen-free environment, and then allowed to stand, so that the iron oxide particles in the diffusion membrane are fully reduced and dissolved, and the organic phosphorus is released as free organic phosphorus; (2) The imaging device treated in step (1) is used as an experimental group, and the imaging device not treated in step (1) is used as a control group; the upper surfaces of the diffusion membranes of the control group and the experimental group are uniformly exposed to the active oxygen for reaction; (3) The fixed membranes of the experimental group and the control group treated in step (2) were taken out, washed, and contacted with a color developer respectively. Then, they were scanned by a scanner and image processed using image J software. By comparing the imaging data of the experimental group and the control group, the kinetic data of the degradation of organic phosphorus to produce phosphate by active oxygen in soil sediments were obtained.

[0020] Preferably, the oxygen-free environment in step (1) is an environment with an oxygen concentration below 0.1 ppm.

[0021] Preferably, the reducing substance in step (1) is derived from organic matter in soil or sediment.

[0022] Preferably, the standing time in step (1) is 24 hours.

[0023] Preferably, the active oxygen in step (2) comes from potassium superoxide, hydrogen peroxide, or the reaction of hydrogen peroxide and ferrous sulfate.

[0024] Preferably, the reaction time in step (2) is 24 hours.

[0025] Preferably, the developer in step (3) is a mixed solution of molybdate and ascorbic acid.

[0026] When the diffusion membrane of the experimental group came into contact with reducing substances, the iron oxide particles containing organophosphorus reacted with them, and the iron oxides were reduced, thereby releasing the organophosphorus in a free form. However, the control group was not reduced, and the organophosphorus was still adsorbed by the iron oxide particles. In the process of reacting with active oxygen, the iron in the experimental group was re-oxidized into iron oxide. Since the rate of degradation of organophosphorus by active oxygen is much faster than its rate of adsorption (such as Figure 8 As shown in Figure 2, the released free organic phosphorus can be quickly degraded by active oxygen into phosphate and fall into the fixed membrane below, where it is adsorbed by the fixed membrane and will not be adsorbed and fixed by the iron ore again. The adsorption rate of phosphate by the phosphorus adsorbent in the fixed membrane is greater than the adsorption rate of phosphate by the iron ore (as shown in Figure 2). Figure 9As shown, the phosphate generated by organophosphorus degradation is not retained on the iron ore in the diffusion membrane, but is quickly fixed to the phosphorus adsorbent nanomaterial in the fixed mold, and the received phosphate is displayed through imaging. The control group, however, does not release free organophosphorus during contact with reactive oxygen species, resulting in a difference in fixed-film imaging compared to the experimental group. By analyzing these images, researchers can obtain data on the degradation kinetics of organophosphorus by reactive oxygen species in soil sediments, as well as the release kinetics of ferrous iron or organophosphorus.

[0027] This invention constructs a two-dimensional imaging gel film and uses iron oxide particles containing organophosphorus to characterize the difference in the degradation efficiency of free and adsorbed organophosphorus by reactive oxygen species generated at the iron oxide interface. The imaging accuracy is controlled within the submillimeter range. The device can characterize the reduction and release of organophosphorus from iron ore in soil and sediments, reproducing the dynamic microscopic characteristics of organophosphorus degradation mediated by reactive oxygen species to the greatest extent possible.

[0028] The beneficial effects of the present invention are: (1) The realistic simulation of the organic phosphorus dissolution process at the soil-sediment iron ore interface is beneficial to the accuracy of the characterization data.

[0029] (2) Analyze the ease or difficulty of degradation of organic phosphorus adsorbed on iron oxides and dissolved organic phosphorus by active oxygen by imaging.

[0030] (3) Provide technical and data support for the degradation efficiency of organic phosphorus mediated by active oxygen at the soil-water interface, rhizosphere interface, and sediment-water interface under redox fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of the diffusion membrane.

[0032] Figure 2 Schematic diagram of the structure of the fixed membrane.

[0033] Figure 3 Schematic diagram of the structure of the film fixing frame.

[0034] Figure 4 Schematic diagram of the assembly of the imaging device.

[0035] Figure 5 This is an external view of the imaging device in Example 1. From left to right, it shows the diffusion membrane, the fixed mold, and the actual assembly diagram. The diffusion membrane contains iron ore that absorbs organic phosphorus, and the fixed mold contains a phosphorus adsorbent.

[0036] Figure 6These are images of the degradation of organophosphorus by active oxygen in Example 1, including, from left to right, a blank background image (control group), an image of the phosphate content produced by the degradation of adsorbed organophosphorus in iron ore by active oxygen under oxidizing conditions (after oxidation in the experimental group), and an image of the phosphate content produced by the degradation of free organophosphorus after dissolution of iron ore by active oxygen under reducing conditions (after reduction in the experimental group).

[0037] Figure 7 These are the test results for different organophosphorus compounds in Example 1.

[0038] Figure 8 This is a comparison chart of the rates of organic phosphorus degradation by active oxygen and adsorption by iron oxides.

[0039] Figure 9 This is a comparison chart of the adsorption rates of phosphate by iron oxide and zirconium oxide.

[0040] Figure 10 This is a graph showing the changes in the concentrations of ferrous iron and free organic phosphorus during the reduction process of the iron oxides in the experimental group (reduction) in Example 1.

[0041] Figure 11 This is a graph showing the concentration changes of ferrous iron and free organic phosphorus in the experimental group (oxidation) in Example 1.

[0042] 1 is the first gel membrane, 2 is iron oxide, 3 is organic phosphorus, 4 is the second gel membrane, 5 is phosphorus adsorbent, 6 is the upper cover of the membrane fixing frame, 7 is the groove of the membrane fixing frame, 8 is the diffusion membrane, and 9 is the fixed membrane. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the specific embodiments, but is defined by the claims. Example

[0044] (1) The ferrihydrite and phytate solutions were mixed and shaken. After the adsorption was completed, the phytate containing ferrihydrite was washed with pure water, freeze-dried and stored as simulated sediment.

[0045] (2) A gel solution containing 15% acrylamide and 0.3% agarose was prepared and cooled to 40-60°C. The solution was then poured into a Petri dish, and dried ferrihydrite particles containing phytate were added. After ultrasonic mixing, ammonium persulfate initiator (70 μL) and TEMED catalyst (25 μL) were added and mixed thoroughly. The mixture was then cooled and solidified for 1 hour. The gel was then soaked in deionized water for at least 24 hours to obtain the diffusion membrane.

[0046] (3) A uniform mixed solution of 28.5% acrylamide, 1.5% N,N-bisacrylamide, and 0.3% agarose was prepared. Activated ZrO2 nanoparticles were then added to the solution at a mass ratio of 1-10%. The mixture was dispersed in an ultrasonic crusher to obtain a coagulated solution containing ZrO2 nanoparticles. The solution was then quickly and evenly transferred to a preheated glass plate. After standing at room temperature for 60 min, the solution was cut into 3 cm diameter discs using a mold to obtain a fixed membrane.

[0047] (4) Place the prepared diffusion membrane and fixed membrane in the film fixing frame according to Figure 4 As shown in FIG. 1 , the diffusion film is stacked on top of the fixed film and assembled and fixed, and the two films are pressed tightly to obtain an imaging device.

[0048] (5) Humic acid is reacted with hydrogen in the presence of nano-palladium catalyst and used as a reducing substance.

[0049] (6) In a glove box (O2 < 0.1 ppm), a reducing substance was injected into the upper surface of the diffusion membrane of the experimental group, and then allowed to stand for 24 hours, so that the iron oxide particles in the diffusion membrane were fully reduced and released organic phosphorus. The released concentration changed as shown in Figure 10 This process simulates the reductive dissolution of iron ore in soils and sediments to release organic phosphorus molecules.

[0050] (7) Potassium superoxide was injected into the upper surface of the diffusion membrane of the experimental group and the control group respectively to generate superoxide radical reaction for 24 hours. In the experimental group, the active oxygen reacted with the released dissolved organic phosphorus, and the orthophosphate produced by the degradation of organic phosphorus was adsorbed and fixed by the phosphate fixation membrane below. In the control group, since it was not treated with reducing substances, it did not cause the iron ore to be reduced and dissolved, and the organic phosphorus was in a state of being adsorbed by the iron ore, such as Figure 11 shown.

[0051] (8) The fixed molds of the experimental group and the control group were removed, rinsed three times with pure water, and immersed in a mixed solution of molybdate and ascorbic acid at 60°C for color development; the colored fixed molds were scanned with a scanner and converted into grayscale images, and finally imaged using image J software to obtain the difference in the efficiency of dissolved organic phosphorus and adsorbed organic phosphorus being degraded by active oxygen to produce orthophosphate. Figure 6 This is a differential image of the phosphate production from the degradation of adsorbed and free phytate by reactive oxygen species. Based on this differential data, the kinetics of phosphate production from the degradation of organic phosphorus by reactive oxygen species in soil sediments were calculated.

[0052] (9) Replace the organophosphorus in step (1) with a different type and use the same method to test. The results are as follows: Figure 7 shown. Figure 7It is a bar graph showing the phosphate production from the degradation of different types of adsorbed and free organophosphorus molecules (glycerophosphate, glucose phosphate, and DNA) by reactive oxygen species.

Claims

1. An imaging device for characterizing the degradation of organic phosphorus by active oxygen in soil sediments, characterized in that: It comprises a diffusion membrane (8), a fixed membrane (9) and a film fixing frame for fixing the diffusion membrane and the fixed membrane. The diffusion membrane (8) is arranged on top of the fixed membrane (9). The diffusion membrane (8) is a thin film formed by a first gel, iron oxide particles containing organic phosphorus are dispersed in the first gel, and the first gel is agarose gel; The fixed membrane (9) is a thin film formed by a second gel, a phosphorus adsorbent is dispersed in the second gel, and the second gel is agarose gel or a cross-linked gel of polyacrylamide and agarose.

2. The imaging device for characterizing the degradation of organic phosphorus by active oxygen in soil sediments according to claim 1, characterized in that: The iron oxides containing organic phosphorus come from the soil to be tested or the sediment to be tested.

3. The imaging device for characterizing the degradation of organic phosphorus by active oxygen in soil sediments according to claim 1, characterized in that: The phosphorus adsorbent is selected from nanoparticles of La(OH)3, ZrO2 or CaCO3.

4. The imaging device for characterizing the degradation of organic phosphorus by active oxygen in soil sediments according to claim 1, characterized in that: The diffusion membrane is prepared by the following method: The mixed solution of acrylamide and agarose is injected into a mold, and dry iron oxide particles containing organic phosphorus are added and evenly dispersed. Then, an initiator and a catalyst are added to solidify the agarose solution, thereby obtaining the diffusion membrane.

5. The imaging device for characterizing the degradation of organic phosphorus by active oxygen in soil sediments according to claim 1, characterized in that: Preferably, the fixed membrane is prepared by the following method: The phosphorus adsorbent is added to a mixed solution containing acrylamide, N,N-bisacrylamide and agarose, and dispersed uniformly to obtain a gel solution. Then, an initiator and a catalyst are added to the gel solution, and the coagulation solution is injected into a mold and solidified to obtain the fixed film.

6. A method for characterizing the degradation of organic phosphorus by active oxygen in soil sediments using the imaging device according to any one of claims 1 to 5, characterized in that: The steps include: (1) in an oxygen-free environment, allowing the upper surface of the diffusion membrane to uniformly contact the reducing substance, and then allowing it to stand, so that the iron oxide particles in the diffusion membrane are fully reduced and dissolved and release the organic phosphorus into free organic phosphorus; (2) using the imaging device treated in step (1) as an experimental group and the imaging device not treated in step (1) as a control group; allowing the upper surfaces of the diffusion membranes of the control group and the experimental group to uniformly contact the active oxygen for reaction; (3) The fixed membranes of the experimental group and the control group treated in step (2) are taken out, washed, and contacted with a color developer respectively, and then scanned by a scanner and image processed using image J software. By comparing the imaging data of the experimental group and the control group, the kinetic data of the degradation of organic phosphorus by active oxygen in soil sediments to produce phosphate is obtained.

7. The method according to claim 6, characterized in that The reducing substance in step (1) is derived from organic matter in soil or sediment.

8. The method according to claim 6, characterized in that The active oxygen in step (2) comes from potassium superoxide, hydrogen peroxide or the reaction of hydrogen peroxide and ferrous sulfate.

9. The method according to claim 6, characterized in that The reaction time in step (2) is 24 hours.

10. The method according to claim 6, characterized in that The developer described in step (3) is a mixed solution of molybdate and ascorbic acid.

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