Method for safe use of arsenic contaminated paddy field based on artificial aeration organization

Abstract

The application discloses a kind of arsenic pollution paddy field safe utilization method based on artificial ventilation organization, the artificial ventilation organization includes several gas permeable tubes, the gas permeable tube allows oxygen to permeate and does not allow water to permeate, and the gas permeable tube is buried in paddy field flooded soil, and air or oxygen is continuously introduced into the gas permeable tube, so as to increase the oxidation-reduction potential of the flooded environment soil, reduce the activity of iron-arsenic reducing bacteria, increase the oxidation of iron-arsenic, thereby promoting the adsorption and fixation of dissolved arsenic in soil solid, reducing the absorption of arsenic by rice and the accumulation of arsenic in rice, and realizing the safe utilization of arsenic pollution paddy field. The application adds oxygen to the flooded paddy field soil through the artificial ventilation organization, has low operating cost, can efficiently and sustainably fix arsenic at low cost, and reduce the accumulation of arsenic in rice.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of land pollution treatment and safe use of contaminated soil, and particularly relates to a safe use method for arsenic-contaminated paddy fields based on artificial aeration organization. BACKGROUND

[0002] Arsenic is a global environmental pollutant and one of the most toxic heavy metals to humans. Common arsenic forms in the environment include arsenite As(III), arsenate As(V), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). Among them, As(III) is the most toxic and mobile arsenic form, which is often detected in flooded soils or sediments. In these soils, dissimilatory arsenic or iron-reducing microorganisms are abnormally active, directly promoting the reduction of As(V) to As(III), resulting in a large increase in soluble As(III). Rice is the only food crop that requires intermittent flooding, and even in arsenic-contaminated paddy soils, the bioavailability of arsenic is very high. In addition, rice has a very high efficiency of arsenic absorption and transport, and often accumulates a large amount of arsenic in rice grains, which is 10 times higher than other cereals. Rice is the staple food for more than half of the world's population, and the rice food chain poses a significant threat to human arsenic exposure. Therefore, reducing arsenic accumulation in rice is a key measure to alleviate human arsenic exposure.

[0003] Currently, a variety of methods have been developed for remediating arsenic-contaminated paddy soils, but sustainable remediation of soil arsenic contamination still faces challenges. Arsenic passivation agents (such as iron minerals, nitrates, titanium gypsum, biochar, etc.) are often used for the stabilization remediation of soil arsenic contamination, but passivation agents can only temporarily reduce the bioavailability of arsenic. Combined with high cost and potential harm to soil organisms, the long-term use of arsenic passivation agents in the field is limited. Chemical washing and hyperaccumulating plant remediation are two promising methods because they can permanently remove soil arsenic contamination, but both methods remove soil nutrients during implementation; in contrast, plant remediation is more promising because it has much less impact on soil quality than chemical washing. However, plant remediation competes with rice for space, light, and nutrients during implementation and requires additional handling of large amounts of high-arsenic waste, making it difficult to persuade farmers to use it widely in the field.

[0004] In addition to adding passivation agents such as iron minerals to paddy soil, iron mineral hot spots can also be formed naturally in the soil. Moreover, iron mineral hot spots tend to be arsenic distribution hot spots because iron minerals can specifically adsorb arsenic. For example, a brick-red iron oxide is often formed on the surface of rice roots, which is called root surface iron film. The aerenchyma of rice can transport oxygen in the air to the roots, and the root oxygen secretion drives the formation of root surface iron film. However, the newly formed dense iron oxide layer will hinder the further secretion of oxygen. Therefore, the root surface iron film of rice is usually only a few millimeters thick, and its fixation efficiency of arsenic is limited. SUMMARY

[0005] The purpose of the present application is to provide a safe utilization method for arsenic-contaminated paddy fields based on artificial aerenchyma, which is also a green, low-cost and efficient arsenic stabilization and remediation method. The method does not affect soil quality and does not affect normal rice production.

[0006] To achieve the purpose of the present application, the following technical solutions are adopted:

[0007] A safe utilization method for arsenic-contaminated paddy fields based on artificial aerenchyma, the artificial aerenchyma comprising a plurality of air-permeable tubes that allow oxygen to pass through but not water, the air-permeable tubes being buried in the flooded soil of the paddy field, and air or oxygen being continuously introduced into the air-permeable tubes.

[0008] In the above technical solution, by introducing air or oxygen, oxygen passes through the air-permeable tubes into the soil environment, thereby increasing the oxidation-reduction potential of the paddy soil, promoting the oxidation of As(III) with high solubility to As(V) with low solubility, reducing the activity of iron-arsenic reducing bacteria, inhibiting the reduction of high-valence arsenic to dissolved arsenic, and forming iron oxides to adsorb and fix dissolved arsenic, thereby reducing the bioavailability of arsenic in the paddy soil and reducing the absorption and accumulation of arsenic in rice.

[0009] In the above technical solution, the arsenic-contaminated paddy field includes an arsenic-contaminated paddy field exceeding the standard and an arsenic-contaminated paddy field not exceeding the standard but with high arsenic bioavailability. The arsenic-contaminated paddy field not exceeding the standard but with high arsenic bioavailability can cause the rice planted therein to absorb and accumulate arsenic, leading to arsenic exceeding the standard in rice and causing food safety problems.

[0010] Air or oxygen is continuously introduced into the air-permeable tubes during the entire growth period of rice, or the continuous aeration is maintained until the dissolved arsenic content in the soil is essentially constant or within a set target.

[0011] In the above technical solution, the working condition of the artificial aeration tissue is that the air pressure in the air permeable tube is 20-500 kPa, preferably 20-400 kPa, or 20-300 kPa, or 20-200 kPa, or 20-100 kPa, or 20-80 kPa, or 20-60 kPa, or 20-40 kPa, or 20-30 kPa, or 20-28 kPa, or 22-26 kPa.

[0012] In the above technical solution, the depth of the air permeable tube buried in the soil is 5-15 cm,

[0013] The inner diameter of the air permeable tube is 1-20 mm, and the wall thickness is 0.5-2.5 mm,

[0014] The laying density of the air permeable tube in the soil is 0.1-0.5 m 2 tube / m 2 soil,

[0015] The air permeable tube is a silica gel tube, and the end of the air permeable tube is closed during aeration.

[0016] Preferably, the depth of the air permeable tube buried in the soil is 7-13 cm, or 7-11 cm, or 7-9 cm;

[0017] The inner diameter of the air permeable tube is 1-15 mm, or 1-10 mm, or 1-8 mm, or 1-5 mm, or 2-5 mm, or 2-4 mm, and the wall thickness is 0.5-2.5 mm, or 0.5-2.0 mm, or 0.5-1.5 mm, or 0.8-1.2 mm;

[0018] The laying density of the air permeable tube in the soil is 0.1-0.4 m 2 tube / m 2 soil, preferably 0.1-0.3, or 0.15-0.25 m 2 tube / m 2 soil.

[0019] Preferably, in the above technical solution, one air permeable tube is laid on the other side or directly below each row of rice plants in the rice field.

[0020] In the above technical solution, the artificial aeration tissue further comprises a gas delivery pump and a power supply unit, the power supply unit is electrically connected with the gas delivery pump to provide electric energy for the working of the gas delivery pump, the gas outlet of the gas delivery pump is connected with the air permeable tube, the gas delivery pump is used to input air or oxygen into the air permeable tube, and the gas source of the gas inlet of the gas delivery pump comes from the ambient air or an oxygen cylinder.

[0021] Preferably, the gas delivery pump adopts an oxygenation pump or an air compression pump;

[0022] The power supply unit comprises a solar panel and a storage battery, the solar panel is connected to the storage battery to charge the storage battery, the storage battery is electrically connected to the oxygenation pump to provide power for the oxygenation pump, and the outlet of the oxygenation pump is connected to the air permeable pipe.

[0023] The end of the air permeable pipe is provided with a valve, preferably a three-way valve, which is closed during gas transmission.

[0024] Preferably, the plurality of air permeable pipes are arranged in parallel with each other, and are connected in series or in parallel through connecting pipes, and are arranged along the rice plant rows in the rice field in parallel with the rice plant rows.

[0025] When the air permeable pipes are connected in series, a valve is arranged at the end of the air permeable pipe; when the air permeable pipes are connected in parallel, a valve is arranged at the end of each air permeable pipe connected in parallel.

[0026] Definition of terms: the laying density of the air permeable pipe in the soil refers to the ratio of the outer surface area of the air permeable pipe to the total surface area of the soil plot.

[0027] The mechanism of the method of the present application is as follows:

[0028] After the artificial aeration organization is placed in the flooded soil, the abiotic or biological processes induced by the artificial aeration organization will participate in the fixation of arsenic in the soil. First, the oxygen introduced by the artificial aeration organization increases the oxidation-reduction potential of the flooded soil. Since iron-arsenic reducing bacteria are more active under reducing conditions, the increase in the oxidation-reduction potential of the soil can reduce the ecological niche of the iron-arsenic reducing bacteria in the soil, reduce the activity of the iron-arsenic reducing bacteria, and inhibit the release of arsenic caused by the dissolution of iron-arsenic reducing bacteria. The increase in the oxidation-reduction potential of the soil can promote the biological oxidation of arsenic, which is beneficial to the oxidation of As(III) with high solubility to As(V) with low solubility. In addition, the iron oxides induced by the oxygen introduced by the artificial aeration organization can provide additional adsorption sites for dissolved arsenic, and the dissolved arsenic is adsorbed and fixed by the newly formed iron oxides, thereby reducing the biological availability of arsenic. Since previous studies have shown that iron oxides can adsorb a large amount of arsenic and are an important arsenic reservoir in the soil, many researchers have attempted to add iron oxides to the flooded soil to reduce the biological availability of arsenic; however, the added iron minerals only have a short-term effect because they are quickly reduced and dissolved by the iron-reducing bacteria in the flooded soil. In contrast, the artificial aeration organization of the present application can continuously input oxygen, thereby continuously promoting the oxidation of divalent iron to promote the formation of iron oxides in the soil. The artificial aeration organization can maintain a centimeter-wide iron oxide reservoir in the soil around it, and the iron oxides can fix the soluble arsenic in the soil, continuously adsorb and fix the arsenic in the soil, and significantly reduce the biological availability of arsenic.

[0029] The beneficial effects of the present application are as follows:

[0030] The inventors found in previous studies that although plastic pipes such as polyethylene and polypropylene pipes can allow oxygen to pass through, when the plastic pipes are inserted into flooded soil, iron oxides can be induced to form on the pipe wall in contact with the soil, which is very similar to the iron film on the rice root system. The formation of the iron oxide layer on the pipe wall can greatly inhibit the diffusion of oxygen, thereby reducing the oxygen transmission efficiency and failing to continuously provide oxygen to the soil, so it cannot significantly promote the formation of iron oxides in the soil and has limited effect on arsenic adsorption and fixation.

[0031] The inventors unexpectedly found that the air permeable tube of the artificial aeration organization is a silica gel tube, the surface of the silica gel tube is not conducive to the formation of iron oxide nodules, so the silica gel tube can still maintain a high oxygen transmission efficiency during long-term use; the silica gel tube can effectively regulate the soil oxidation-reduction potential, promote the oxidation of divalent iron and the generation of iron oxides in the soil, and at the same time promote the oxidation of As(III) with high solubility to As(V) with low solubility. The newly generated iron oxides can fix arsenic in the soil and reduce the bioavailability of arsenic. In addition, iron-arsenic reducing bacteria are anaerobic bacteria, and after the oxidation-reduction potential of the soil is increased, the activity of the iron-arsenic reducing bacteria is inhibited, and the iron-arsenic reduction and dissolution mediated by the bacteria is inhibited. The application of the artificial aeration organization in the present application to rice planting can effectively reduce the bioavailability of arsenic in the soil, thereby significantly reducing the absorption and accumulation of arsenic by rice. Compared with the traditional addition of iron oxide passivation agent, the method of the present application has the advantages of low cost, simple operation, and no secondary pollution, and provides an environmentally friendly and economically efficient method for the safe use of arsenic-contaminated paddy fields, which can effectively ensure the safe production of rice. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a structural schematic diagram of the artificial aeration organization used in the present application.

[0033] Figure 2 is the influence of the artificial aeration organization on the chemical properties of the soil, wherein Fig. A is the change of pH, Fig. B is the change of oxidation-reduction potential, Fig. C is the change of soluble organic carbon, Fig. D is the change of dissolved iron, Fig. E is the change of dissolved manganese, and Fig. F is the change of dissolved arsenic.

[0034] Figure 3 is the result of controlling the oxygen evolution rate of the artificial aeration organization using air pressure and density, wherein Fig. A is the relationship between the air pressure inside the artificial aeration organization and the oxygen evolution rate, and Fig. B is the oxygen evolution rate of the artificial aeration organization under different air pressures and densities.

[0035] Figure 4Chemical changes in the soil near the artificial aeration organization silica gel tube, wherein Figure A is the gradient change of the oxidation-reduction potential, Figure B is the gradient change of dissolved iron, Figure C is the gradient change of dissolved manganese, Figure D is the gradient change of dissolved arsenic, Figure E is the gradient change of dissolved As(III), and Figure F is the gradient change of dissolved As(V).

[0036] Figure 5 Effects of the artificial aeration organization on the physicochemical properties during the planting of potted rice, wherein Figure A is the oxidation-reduction potential, Figure B is dissolved iron, Figure C is dissolved manganese, and Figure D is dissolved arsenic.

[0037] Figure 6 Effects of the artificial aeration organization on the biomass of rice and the arsenic content in different tissues. DETAILED DESCRIPTION

[0038] The application will be further described in conjunction with the examples below, but the application is not limited by the examples.

[0039] In the following examples, the experimental methods are conventional methods unless otherwise specified; the materials used are conventional materials; and the chemical reagents used are of chemical analysis purity.

[0040] The sources of the materials in the examples of the application are as follows:

[0041] Silica gel tube: a commercially available conventional silica gel tube (main raw material is silica gel (mSiO2·nH2O), and a vulcanizing agent is added for extrusion molding), the silica gel tube used in the examples of the application has an inner diameter of 3 mm and a wall thickness of 1 mm;

[0042] The oxygenation pump, the solar cell panel, and the storage battery are purchased from Beijing Jingdong Century Trade Co., Ltd.

[0043] Example 1: Construction of an artificial aeration organization for aeration in a rice field wetland environment

[0044] The artificial aeration organization constructed in the application, as shown in Figure 1 is mainly composed of an air-permeable tube 1, a gas delivery pump 2, and a power supply unit 3. The power supply unit 3 is electrically connected to the gas delivery pump 2 to provide power for the operation of the gas delivery pump 2. The gas delivery pump 2 is used to input air or oxygen into the air-permeable tube 1. The gas source at the gas inlet of the gas delivery pump 2 comes from the ambient air or an oxygen cylinder. The gas outlet of the gas delivery pump 2 is connected to the air-permeable tube 1, which is buried in the soil. The end of the air-permeable tube 1 is provided with a stainless steel three-way ball valve, which is closed during the pumping process to maintain a certain air pressure in the air-permeable tube 1.

[0045] The energy supply is an important problem when using artificial aeration organization in the field. Although the energy required by the 3.5W oxygenation pump can be supplied by a large-capacity battery, this energy supply method is high in cost and not economical and environmentally friendly. Therefore, we designed a solar-powered artificial aeration organization. Energy is collected through a solar panel and stored in a battery, which can ensure uninterrupted power supply to the artificial aeration organization throughout the day to maximize the oxygen excretion rate of the artificial aeration organization. Field tests have proven that the solar-powered artificial aeration organization design is feasible, and this setting improves the feasibility of using artificial aeration organization methods on a large scale.

[0046] In embodiments 2-5 of the present application, experiments were conducted using the artificial aeration organization, wherein the air permeable tube 1 was a silica gel tube, the gas delivery pump 2 was a commercially available oxygenation pump, the power supply unit 3 consisted of a solar panel 31 and a battery 32, the solar panel 31 was connected to the battery 32 to charge the battery 32, the battery 32 was electrically connected to the oxygenation pump to provide power to the oxygenation pump, the outlet of the oxygenation pump was connected to the silica gel tube, the ball valve at the end of the silica gel tube was closed, a certain air pressure was maintained in the silica gel tube, and the gas source at the gas inlet of the oxygenation pump was natural environmental air.

[0047] The gas delivery pump 2 is not limited to an oxygenation pump, but can also use devices capable of inputting gas into the air permeable tube 1 in the prior art, such as air compression pumps.

[0048] Example 2, Effect of Artificial Aeration Organization on Soil Chemical Properties

[0049] Typical surface soil (0-20 cm) of a rice field was collected, dried naturally in a cool place, and dried for storage. Using flooded culture to simulate rice field conditions, 1.0 kg of rice field soil was added to a 650 mL culture tank, the soil depth was 10 cm, and the silica gel tube (length 10 cm, i.e. the silica gel tube was laid at a density of 0.2 m 2 per tube / m 2 of soil) of the artificial aeration organization in Example 1 was placed in the soil at a depth of about 8 cm from the surface soil. During the culture, the soil was flooded, the flooding was higher than the soil surface by 3 cm, and the microcosm culture was carried out at room temperature. During the experiment, air was input into the silica gel tube, and the air pressure in the silica gel tube was 20 kPa.

[0050] During the 30-day incubation, soil pore water around the artificial aeration tissue was collected periodically (1, 3, 6, 10, 15, 20, 30 days) using a Rhizon sampler (sampling head pore size: 0.1 pm), and the pH and oxidation-reduction potential of the pore water were tested using a portable pH and oxidation-reduction potential meter. After the test was completed, the soil pore water was preserved using 1M hydrochloric acid. The soluble organic carbon content in the soil pore water was tested using a TOC instrument, the divalent iron (Fe(II)) and trivalent iron (Fe(III)) in the soil pore water were determined using a 1, 10-phenanthroline spectrophotometric method, and the manganese and arsenic in the soil pore water were tested using an inductively coupled plasma mass spectrometer.

[0051] The results are shown in Figure 2 As shown in A, compared with the control group without air input, the artificial aeration tissue had less effect on the pH of the flooded soil, and the pH of the control and treatment groups remained near neutral (~ 6.88); Figure 2 B shows that the artificial aeration tissue significantly increased the oxidation-reduction potential of the soil, changing the oxidation-reduction potential of the soil from strong reduction (-145 mV) to moderate reduction (-87.3 mV); Figure 2 C shows that the artificial aeration tissue significantly reduced the dissolved organic carbon, with a reduction of 20.3%; Figure 2 D-E shows that the artificial aeration tissue significantly reduced the soluble iron and manganese in the soil, with a reduction of 41.5% and 45.2%, respectively; at the same time, the artificial aeration tissue significantly reduced the bioavailability of arsenic in the soil, with a reduction of 44.0% of dissolved arsenic Figure 2 F).

[0052] Example 3, Regulation of air pressure on the oxygen excretion rate of artificial aeration tissue

[0053] The density of silica gel tubes in artificial aeration tissue is a key parameter for controlling its oxygen excretion rate, but in practical applications, continuously increasing the density of silica gel tubes is not feasible in terms of economy and operability. Therefore, we designed an experiment combining physical parameter testing and simulation analysis to test whether changing the air pressure in the artificial aeration tissue can be an alternative scheme for controlling the oxygen excretion rate of artificial aeration tissue.

[0054] In the laboratory, according to the ISO-17455 standard test method, the oxygen permeability tester was used to test the oxygen permeability of the silica gel tube under different air pressure conditions (0, 2, 5, 10, 20, 50 kPa, 25°C) in a 1-meter-long silica gel tube. According to the relationship between oxygen permeability and air pressure and silica gel tube density, the oxygen permeability under different air pressure and silica gel tube density during the entire rice growth period (120 days) was simulated.

[0055] Experimental results show that the oxygen secretion rate of artificially ventilated tissues is linearly positively correlated with air pressure. Figure 3 A). This strongly supports the idea that, at a given density, the oxygen release rate can be quickly, conveniently, and efficiently controlled by increasing the air pressure inside the silicone tube. For example... Figure 3 As shown in Figure B, the target oxygen yield can be easily achieved by adjusting the density of the silicone tubing in the artificial ventilation system and the air pressure of the oxygen pump. For example, with a silicone tubing density of 0.2 m³ / s and an oxygen pump pressure of 0.2 m³ / s... 2 pipe / m 2 Under soil conditions and a pressure of 25 kPa, a considerable amount of oxygen will be released (~600 kg O2 / (hectare·quarter)). Under this oxygen release condition, the oxygen released into the flooded soil through artificial aeration can additionally induce the formation of 5850 kg Fe2O3 / (hectare·quarter), which will provide a large number of adsorption sites for dissolved arsenic.

[0056] Example 4

[0057] Typical arsenic-contaminated paddy soil (0-20cm) was collected, air-dried naturally in a cool place, and stored for later use. Simulating paddy field conditions, 5.0kg of paddy field soil was added to a 2500mL culture tank at a depth of 15cm. The silicone tubes used in Example 1 for artificial aeration were placed approximately 5.5cm below the surface soil, with a tube length of 15cm (i.e., a density of 0.2m). 2 pipe / m 2 In situ repeated pore water samplers (IPI; planar test distance 45 mm, spatial resolution 2 mm) were installed on the soil-silicone tube plane. The soil was submerged and cultured, with the water level 3 cm above the soil surface, under microcosmic conditions at room temperature. When using artificially aerated tissue, a 3.5 W aerator was used to maintain the air pressure in the silicone tube of the artificially aerated tissue at 25 kPa. After 30 days of culture, the change in redox potential from surface water to the surface of the silicone tube was measured along the soil profile using Unisense redox microelectrodes (spatial resolution 1.1 mm) for a total of 7 cm. Simultaneously, soil pore water samples (4.5 cm in total) were collected from the silicone tube-soil micro-interface at a soil depth of ~6 cm using an IPI sampler. The divalent iron (Fe(II)) and trivalent iron (Fe(III)) in the soil pore water were determined using the 1,10-phenanthroline spectrophotometric method. The manganese and arsenic in the soil pore water were tested using inductively coupled plasma mass spectrometry (ICP-MS), and different arsenic forms were tested using high performance liquid chromatography coupled with ICP-MS.

[0058] The results are as follows Figure 4As shown, the artificial aeration organization significantly improved the oxidation-reduction potential of the centimeter-wide flooded soil, and also had a huge impact on other processes in the flooded soil that are sensitive to changes in oxidation-reduction potential. Without the artificial aeration organization, along the soil-water interface, from the overlying water to the underlying soil (6.0 cm deep), the oxidation-reduction potential rapidly decreased from 224 mV to -115 mV. In contrast, in the presence of the artificial aeration organization, the oxidation-reduction potential slowly decreased from 237 mV to -42.1 mV, and then gradually increased to 0.891 mV near the silica gel tube deployed at a soil depth of 6.0 cm. The artificial aeration organization significantly improved the oxidation-reduction potential of the centimeter-wide soil. In addition, without the artificial aeration organization, the iron in the underlying soil pore water at a depth of ~ 6 cm was extremely high (99.7 mg / L). In contrast, the dissolved iron and manganese within a distance of 4.5 cm around the silica gel tube were significantly reduced (-60.9% and -46.3%, respectively). At the same time, the arsenic within a distance of 4.5 cm around the silica gel tube was significantly reduced by 73.3%, and the two inorganic arsenic species were also significantly reduced. Notably, newly formed brick-red iron oxides were present within a centimeter range around the silica gel tube. This indicates that after using the artificial aeration organization, the ferrous iron in the flooded soil is strongly oxidized to iron oxides, which provides a large number of additional adsorption sites for dissolved arsenic, reducing arsenic bioavailability.

[0059] Example 5, Effect of artificial aeration organization on physicochemical properties during potted rice planting and on arsenic uptake and accumulation of potted rice

[0060] Under the experimental conditions of a 25 kPa air pressure and a 0.2 m 2 pipe / m 2 soil density of the silica gel tube, the effect of the artificial aeration organization on the physicochemical properties of arsenic-contaminated paddy soil during potted rice planting was tested under greenhouse conditions.

[0061] Under greenhouse conditions, 5.0 kg of paddy soil was added to a 2500 mL culture pot, with a soil depth of 15 cm, and the silica gel tube of the artificial aeration organization in Example 1 was placed in the soil at a depth of about 8 cm from the surface soil, with a flooding depth of 5 cm. An air treatment group and a non-air control group were set up. Two rice seedlings with consistent growth (variety Yongyou 15, four-leaf stage) were transplanted to the center of each culture pot, with the silica gel tube located directly below the rice seedlings. The air treatment group used the artificial aeration organization to continuously aerate the rice throughout the growing season.

[0062] I. Effect on physicochemical properties during potted rice planting

[0063] Within 120 days after rice transplanting, soil pore water around artificially aerated tissues was collected using a Rhizon sampler (sampling head aperture: 0.1 μm). The redox potential of the pore water was measured using a portable redox potentiometer. After testing, the soil pore water was acidified with 1M hydrochloric acid and preserved. The concentrations of ferrous iron (Fe(II)) and ferric iron (Fe(III)) in the soil pore water were determined using the 1,10-phenanthroline spectrophotometric method, and the concentrations of manganese and arsenic in the soil pore water were determined using inductively coupled plasma mass spectrometry (ICP-MS).

[0064] The results are as follows Figure 5 As shown in Figure A, under greenhouse conditions, due to waterlogging during cultivation, the redox potential of the soil in the control group was lower (-119 mV); compared with the control group, artificially aerated tissue significantly increased the redox potential of the soil (-80.7 mV; 32.2%). Meanwhile, Figure 5 BC showed that artificial aeration significantly reduced dissolved iron and manganese in the soil (-37.0% and 51.0%). Similarly, as Figure 5 As shown in Figure D, artificial aeration significantly reduced dissolved arsenic in the soil (-54.4%). It can be predicted that the efficiency of artificial aeration in fixing dissolved arsenic can be further improved by simply increasing the air pressure in the artificial aeration system.

[0065] II. Effects on arsenic absorption and accumulation in potted rice

[0066] Rice plants were harvested 120 days after transplanting and cultivation. The plants were then separated into roots, stems, leaves, and panicles, and dried in an 80℃ oven to constant weight. The weights were then measured using a balance to estimate the biomass of different rice tissues. Subsequently, the dried rice tissues were ground, passed through a 100-mesh sieve, and digested using a 1:1 solution of concentrated nitric acid and hydrogen peroxide. Inductively coupled plasma mass spectrometry (ICP-MS) was used to test the arsenic content in the digestion solution, thereby calculating the arsenic content in the rice tissues.

[0067] The results are as follows Figure 6 As shown, artificial aeration had little effect on the dry matter content of different rice tissues, namely roots, stems, leaves, and panicles (p>0.134). Compared with the control, artificial aeration significantly reduced the arsenic content of different rice tissues, namely roots, stems, leaves, and panicles (p<0.001). It can be predicted that simply increasing the air pressure in the artificial aeration system could further enhance its effect in reducing arsenic accumulation in rice.

Claims

1. A method for safe utilization of arsenic contaminated paddy field based on artificially aerated tissue, characterized by: The artificial aeration organization comprises several air permeable tubes which allow air or oxygen to permeate but not water, and the air permeable tubes are buried in the flooded soil of the paddy field, one air permeable tube is laid in each row of rice plants in the paddy field, and air or oxygen is continuously introduced into the air permeable tubes; through the introduction of air or oxygen, oxygen permeates into the soil environment through the air permeable tubes, thereby increasing the oxidation-reduction potential of the soil in the paddy field, promoting the oxidation of As(III) with high solubility into As(V) with low solubility, reducing the activity of iron-arsenic reducing bacteria, inhibiting the reduction of high-valence arsenic into dissolved arsenic, and adsorbing and fixing the dissolved arsenic by the formed iron oxides, thereby reducing the bioavailability of arsenic in the soil of the paddy field and the absorption and accumulation of arsenic in rice; during the whole growth period of rice, air or oxygen is continuously introduced into the air permeable tubes, or the continuous aeration is performed until the content of dissolved arsenic in the soil is basically constant or reaches a set target. The air permeable tube is buried in the soil at a depth of 5-15 cm, the inner diameter of the air permeable tube is 1-20 mm, the wall thickness is 0.5-2.5 mm, and the laying density of the air permeable tube in the soil is 0.1-0.5 m 2 pipe / m 2 The soil is permeable to the tube, the surface of the silica gel tube is not conducive to the combination of iron oxide, and the silica gel tube maintains a high oxygen permeability during long-term use; the end of the air permeable tube is closed during the aeration process; The artificial aeration organization further comprises a gas delivery pump and a power supply unit, the power supply unit is electrically connected with the gas delivery pump to provide electric energy for the operation of the gas delivery pump, the gas outlet of the gas delivery pump is connected with the air permeable tube, the gas delivery pump is used to input air or oxygen into the air permeable tube, and the gas source of the gas inlet of the gas delivery pump is from ambient air or an oxygen cylinder; the air permeable tubes are arranged in parallel with each other, and the air permeable tubes are connected in series or in parallel through connecting pipes, and are arranged along the rows of rice plants in the paddy field in parallel with the rows of rice plants; when the air permeable tubes are connected in series, valves are arranged at the ends of the air permeable tubes; when the air permeable tubes are connected in parallel, valves are arranged at the ends of the air permeable tubes connected in parallel.

2. The method of claim 1, wherein: The arsenic-contaminated paddy field includes an arsenic-contaminated paddy field exceeding the standard and an arsenic-contaminated paddy field not exceeding the standard but with high arsenic bioavailability.

3. The method of claim 1, wherein: The working condition of the artificial aeration organization is that the air pressure in the air permeable tube is 20-500 kPa.

4. The method of claim 1, wherein: The depth of the air permeable tube buried in the soil is 7-13 cm; The inner diameter of the air permeable tube is 1-15 mm; The air permeable tubes are laid in the soil at a density of 0.1-0.4 m 2 pipes / m 2 soil.

5. The method of claim 1, wherein: The gas delivery pump is an oxygenation pump or an air compression pump; The power supply unit comprises a solar cell panel and a storage battery, the solar cell panel is connected with the storage battery to charge the storage battery, the storage battery is electrically connected with the oxygenation pump to provide electric energy for the oxygenation pump, and the outlet of the oxygenation pump is connected with the air permeable tube; Valves are arranged at the ends of the air permeable tubes.

6. The method of claim 5, wherein: The valves are three-way valves, and the valves are closed during gas transmission.

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