Method for improving uranium-contaminated soil phytoremediation efficiency

Abstract

The invention discloses a method for improving uranium-contaminated soil phytoremediation efficiency, and belongs to the technical field of uranium-contaminated soil phytoremediation. The method comprises the following steps: determining the type and concentration range of a soil conditioner capable of effectively increasing the proportion of the soluble uranium in the soil, and drawing a change curve of the amount of the soluble uranium in the soil; determining the enrichment amount of the overground part and the underground part of the uranium hyperaccumulator to the soluble uranium in the soil, and drawing a change curve of the uranium enrichment amount of the overground part and the underground part of the uranium hyperaccumulator; the type, the content and the adding time of the soil conditioner are regulated and controlled, so that the curve change trend of the amount of soluble uranium in the soil is consistent with the curve change trend of the amount of uranium enriched in the overground part and the underground part of the uranium hyperaccumulator. According to the method for improving the efficiency of phytoremediation of the uranium-contaminated soil, the efficiency of phytoremediation of the uranium-contaminated soil is remarkably improved, the remediation period is shortened, and the remediation cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of phytoremediation of uranium contaminated soil, and in particular relates to a method for improving the efficiency of phytoremediation of uranium contaminated soil. Background Art

[0002] During the uranium mining process, since uranium has both heavy metal and radioactive toxicity, its contaminated soil poses a serious long-term threat to the health of surrounding residents and the ecological environment. The remediation of uranium-contaminated soil has therefore become particularly urgent. At present, the remediation technologies for uranium-contaminated soil mainly include physical methods, chemical methods and biological methods. Among these methods, phytoremediation has attracted widespread attention due to its advantages such as environmental friendliness, low cost and simple operation. Phytoremediation technology uses plants and their related microorganisms to transfer uranium from the soil to the roots, stems and leaves of the plants to achieve soil purification.

[0003] However, the efficiency of phytoremediation of uranium-contaminated soil is relatively low, mainly due to the limited accumulation capacity of plants for uranium, long growth cycle, and the resistance and low enrichment coefficient of some plants to uranium. In addition, the dissolution and migration rate of uranium in soil is slow, resulting in the inability of dissolved uranium to be efficiently enriched by plants, making the phytoremediation process take years or even decades. In order to improve the efficiency of phytoremediation of uranium-contaminated soil, studies have attempted to change the occurrence form of uranium in soil by adding soil amendments such as chemical chelators, microorganisms and plant growth nutrients to promote the absorption of uranium by plants. However, these methods have certain limitations. For example, the converted uranium in the soil may be adsorbed again by soil minerals or reduced and fixed by microorganisms, becoming insoluble or plant-insoluble uranium, which reduces the effect of phytoremediation. Therefore, it is urgent to develop a new method and technology that can effectively couple the form transformation of uranium in soil with the enrichment of uranium by plants to improve the efficiency of phytoremediation of uranium-contaminated soil. Summary of the invention

[0004] The present invention aims to provide a method for improving the efficiency of phytoremediation of uranium contaminated soil, which significantly improves the efficiency of phytoremediation of uranium contaminated soil, shortens the remediation period, reduces the remediation cost, reduces environmental risks, and provides an efficient and environmentally friendly method for the remediation of uranium contaminated soil.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for improving the efficiency of phytoremediation of uranium-contaminated soil, comprising the following steps:

[0007] S1. Obtaining a change curve of the amount of soluble uranium in the soil: determining the type and concentration range of soil conditioners that can effectively increase the proportion of soluble uranium in the soil, and drawing a change curve of the amount of soluble uranium in the soil under the action of the soil conditioners;

[0008] S2. Obtaining the variation curve of the amount of uranium enrichment in the aboveground and underground parts of uranium hyper-enriched plants: determining the amount of enrichment of soluble uranium in the soil by the aboveground and underground parts of uranium hyper-enriched plants, and drawing the variation curve of the amount of uranium enrichment in the aboveground and underground parts of uranium hyper-enriched plants;

[0009] S3. Coupling of uranium form transformation in soil and uranium enrichment in plants: According to the change curve of the amount of soluble uranium in the soil obtained in step S1 and the change curve of the amount of uranium enriched in the aboveground and underground parts of the uranium hyperaccumulating plants obtained in step S2, the type, content and addition time of the soil conditioner are regulated to make the curve change trend of the amount of soluble uranium in the soil consistent with the curve change trend of the amount of uranium enriched in the aboveground and underground parts of the uranium hyperaccumulating plants, so as to maximize the enrichment of soluble uranium in the soil by uranium hyperaccumulating plants and improve the efficiency of phytoremediation of uranium contaminated soil.

[0010] Preferably, in step S1, the soil conditioner comprises oxalic acid and deferoxamine mesylate, the concentration range of oxalic acid is 5-15 mmol / L, and the concentration range of deferoxamine mesylate is 0.05-2 mmol / L.

[0011] Preferably, the oxalic acid is added to the rhizosphere soil, and the concentration of oxalic acid in the soil is in the range of 0.5-10 mmol / kg, and the deferoxamine mesylate is added to the rhizosphere soil, and the concentration of deferoxamine mesylate in the soil is in the range of 0.02-0.45 mmol / kg.

[0012] Preferably, the method for determining soluble uranium in soil comprises the following steps:

[0013] A1. Accurately weigh 2.00 g of soil sample and place it into a 100 mL hard plastic round-bottom centrifuge tube with a lid;

[0014] A2, add 16mL 1mol / L MgCl2 solution, pH = 7.0, and shake continuously at 25℃ for 1h;

[0015] A3, centrifuge at 4000 rpm for 20 min, remove the supernatant and dilute to a 25 mL volumetric flask;

[0016] A4. Wash the residue with deionized water, centrifuge at 4000 rpm for 20 min, filter all the supernatant, and determine the uranium concentration using a micro-uranium analyzer.

[0017] Preferably, the uranium hyperaccumulating plants include one or more of Macleaya cordata, Commelina scabra or Salix babylonica.

[0018] Preferably, the concentration of soluble uranium in the soil is 0.02-150 mg / kg.

[0019] Preferably, the step of calculating the uranium enrichment of the above-ground part and the underground part of the uranium hyperaccumulating plant comprises:

[0020] B1. Harvest uranium hyperaccumulators, rinse roots once with 10 mM Na2CO3 and twice with deionized water;

[0021] B2. The uranium hyperaccumulating plants were sterilized at 105°C for 30 minutes, dried at 70°C to constant weight, and the dry weight of the above-ground and underground parts of the uranium hyperaccumulating plants was weighed and recorded;

[0022] B3. Weigh 0.2000g of dried uranium hyper-enriched plant sample into a 200mL beaker, add 10mL of nitric acid, heat and concentrate to 1-2mL on a hot plate, cool, add 5mL of nitric acid and 3mL of perchloric acid, heat and concentrate to 1-2mL, cool, dilute with deionized water, filter and make up to volume in a 50mL volumetric flask, and use a trace uranium analyzer to detect the uranium content in the solution.

[0023] Preferably, in step S3, the type of the soil conditioner comprises one or both of oxalic acid and deferoxamine mesylate.

[0024] Preferably, in step S3, the specific method for regulating the content and addition time of the soil conditioner is: according to the change curve obtained in step S2, 0.05-10mmol / L of soil conditioner is added to the rhizosphere soil 3-6 days before the highest point of uranium enrichment concentration in the aboveground and underground parts of the hyperaccumulator plants or the slowdown of the rising trend, so that the concentration of the soil conditioner in the soil reaches 0.02-2mmol / kg, and every 15 days, 0.05-10mmol / L of soil conditioner is added to the rhizosphere soil, so that the concentration of the soil conditioner in the soil reaches 0.02-2mmol / kg.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] The present invention discloses a method for improving the efficiency of plant repair of uranium contaminated soil. By regulating the type, content and addition time of soil conditioner, the uranium form transformation in the soil is coupled with the plant uranium enrichment process, so that the change trend of the amount of soluble uranium in the soil is consistent with the change trend of the amount of plant enriched uranium, thereby maximizing the enrichment of soluble uranium by plants. This method not only significantly improves the efficiency of plant repair of uranium contaminated soil, but also shortens the repair cycle, reduces the repair cost, and alleviates the secondary pollution problem that may be caused by soil conditioners. By accurately optimizing the type, content and addition time of soil conditioner, the present invention ensures the efficient enrichment of uranium and the maximization of plant repair effect, realizes efficient and environmentally friendly repair of uranium contaminated soil, and the entire repair process does not increase environmental risks. It is a sustainable uranium contaminated soil repair technology.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a curve showing the change of the amount of soluble uranium in the soil under the action of different concentrations of oxalic acid in Example 1 of the present invention;

[0029] Figure 2 This is a curve showing the change of the amount of soluble uranium in the soil under the action of different concentrations of deferoxamine mesylate according to Example 1 of the present invention;

[0030] Figure 3 This is the variation curve of the uranium enrichment amount in the aboveground and underground parts of the uranium hyper-enriched plant in Example 1 of the present invention, wherein: Figure 3 A in the figure is the variation curve of uranium enrichment in the aboveground part of uranium hyperaccumulating plants. Figure 3 B in the figure is the curve showing the change of uranium enrichment in the underground part of uranium hyperaccumulating plants. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0032] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0033] In the present invention, unless otherwise specified, other test materials and instruments and equipment are conventional test materials in the art and can be purchased through commercial channels.

[0034] Example 1 This example provides a method for improving the efficiency of phytoremediation of uranium-contaminated soil, comprising the following steps:

[0035] S1. Obtain the change curve of the amount of soluble uranium in the soil: grind the test soil and pass it through a 200-mesh sieve, dry it to constant weight, and take 50.00g of samples respectively, evenly distribute them in a culture dish with a diameter of 90mm, set three replicates for each concentration, and conduct 30 groups of tests in total. In each group of tests, different concentrations of soil conditioner 1-oxalic acid were added, and the concentrations of oxalic acid were set to 0, 3, 6, 9 and 12mmol / L, respectively. Different concentrations of oxalic acid were added to the rhizosphere soil, and the concentrations of oxalic acid in the soil were 0, 2, 4, 6 and 8mmol / kg, respectively. In each group of tests, the water-soil ratio was 1:2, and the culture dish was covered to prevent water loss. The test samples were placed in the test environment under natural light and temperature conditions, and samples were taken on the 0th, 3rd, 6th, 9th, 13th and 15th days of the test to detect the content of soluble uranium in the soil.

[0036] The method for determining soluble uranium in soil includes the following steps:

[0037] A1. Accurately weigh 2.00 g of soil sample and place it into a 100 mL hard plastic round-bottom centrifuge tube with a lid;

[0038] A2, add 16mL 1mol / L MgCl2 solution, pH = 7.0, and shake continuously at 25℃ for 1h;

[0039] A3, centrifuge at 4000 rpm for 20 min, remove the supernatant and dilute to a 25 mL volumetric flask;

[0040] A4. Wash the residue with deionized water, centrifuge at 4000 rpm for 20 min, filter all the supernatant, and determine the uranium concentration using a micro-uranium analyzer.

[0041] Based on the above results, a curve of the change in the amount of soluble uranium in the soil under the action of soil conditioner 1-oxalic acid was drawn. Figure 1 .

[0042] S2. Obtain the curve of the change of uranium enrichment in the aboveground and underground parts of uranium hyper-enriched plants: select the uranium hyper-enriched plant Macleaya cordata, where Macleaya cordata is a seedling cultivated for 2 months, soaked in deionized water for a week and planted when the root length is 1 cm. The size of the flower pot is 15.7cm×17cm×26.5cm. 5kg of uranium-contaminated farmland soil is added to each flower pot. The concentration of soluble uranium in the soil is 30mg / kg. Macleaya cordata with the same growth size are planted in the flower pots respectively, and collected once a week, 3 plants are taken each time, and a total of 9 samples are taken. All plant cultivation is carried out in a greenhouse. During the experiment, the air temperature is maintained at 28°C and the humidity is 60%. The entire experiment lasts for 63 days. After harvesting the plants, the uranium enrichment of the aboveground and underground parts of the plants is calculated, including the following steps:

[0043] B1. Harvest Macleaya, rinse the roots once with 10 mM Na2CO3 and twice with deionized water;

[0044] B2. Fix the Macleania scoparia at 105°C for 30 minutes, dry at 70°C to constant weight, and weigh and record the dry weight of the above-ground and underground parts of the Macleania scoparia.

[0045] B3. Weigh 0.2000g of dried Macleaya sample into a 200mL beaker, add 10mL nitric acid, heat and concentrate to 1-2mL on a hot plate, add 5mL nitric acid and 3mL perchloric acid after cooling, heat and concentrate to 1-2mL, cool, dilute with deionized water, filter and make up to volume in a 50mL volumetric flask, and use a trace uranium analyzer to detect the uranium content in the solution. The results are as follows: Figure 3 .

[0046] S3. Coupling of uranium form transformation in soil and uranium enrichment in plants: According to the change curve of the amount of soluble uranium in the soil obtained in step S1 and the change curve of the amount of uranium enriched in the aboveground and underground parts of Macleaya cordata obtained in step S2, starting from the 14th day, the uranium concentration in the aboveground and underground parts of Macleaya cordata began to decrease, with the highest value on the 14th day. 6 days before the highest point of uranium enrichment concentration in the aboveground and underground parts of Macleaya cordata, that is, starting from the 8th day of planting Macleaya cordata, 10 mmol / L oxalic acid was added to the rhizosphere soil to make the concentration of oxalic acid in the soil reach 2 mmol / kg. Thereafter, 10 mmol / L oxalic acid was added to the rhizosphere soil every 15 days to make the concentration of oxalic acid in the soil reach 2 mmol / kg, so that the curve change trend of the amount of soluble uranium in the soil is consistent with the change trend of the amount of uranium enriched in Macleaya cordata, so as to maximize the enrichment of soluble uranium in the soil by Macleaya cordata and improve the efficiency of phytoremediation of uranium-contaminated soil.

[0047] Example 2 This example provides a method for improving the efficiency of phytoremediation of uranium-contaminated soil, comprising the following steps:

[0048] S1. Obtain the variation curve of the amount of soluble uranium in the soil: Grind the test soil and pass it through a 200-mesh sieve, dry it to constant weight, and take 50.00g of samples respectively, evenly distribute them in a culture dish with a diameter of 90mm. Set three replicates for each concentration, and conduct a total of 30 groups of experiments. In each group of experiments, different concentrations of soil conditioner 2-deferoxamine mesylate were added, and the concentrations of deferoxamine mesylate were 0, 0.05, 0.10, 0.20 and 0.40mmol / L, respectively. Different concentrations of deferoxamine mesylate were added to the rhizosphere soil, and the concentrations of deferoxamine mesylate in the soil were 0, 0.025, 0.05, 0.10 and 0.20mmol / kg, respectively. In each group of experiments, the water-soil ratio was 1:2, and the culture dish was covered to prevent water loss. The test samples were placed in a test environment under natural light and temperature conditions, and samples were taken on the 0th, 3rd, 6th, 9th, 13th and 15th days of the test to detect the content of soluble uranium in the soil.

[0049] The method for determining soluble uranium in soil includes the following steps:

[0050] A1. Accurately weigh 2.00 g of soil sample and place it into a 100 mL hard plastic round-bottom centrifuge tube with a lid;

[0051] A2, add 16mL 1mol / L MgCl2 solution, pH = 7.0, and shake continuously at 25℃ for 1h;

[0052] A3, centrifuge at 4000 rpm for 20 min, remove the supernatant and dilute to a 25 mL volumetric flask;

[0053] A4. Wash the residue with deionized water, centrifuge at 4000 rpm for 20 min, filter all the supernatant, and determine the uranium concentration using a micro-uranium analyzer.

[0054] Based on the above results, a curve of the change of the amount of soluble uranium in the soil under the action of soil conditioners was drawn. Figure 2 .

[0055] S2. Same as step S2 in Example 1.

[0056] S3. Coupling of uranium form transformation in soil and uranium enrichment in plants: According to the change curve of the amount of soluble uranium in the soil obtained in step S1 and the change curve of the amount of uranium enrichment in the aboveground and underground parts of Macleaya cordata obtained in step S2, 1 mmol / L of deferoxamine mesylate was added to the rhizosphere soil 3 days before the highest uranium enrichment concentration in the aboveground and underground parts of Macleaya cordata, that is, on the 11th day of Macleaya cordata planting, so that the concentration of deferoxamine mesylate in the soil reached 0.1 mmol / kg. Thereafter, 1 mmol / L of deferoxamine mesylate was added to the rhizosphere soil every 15 days, so that the concentration of deferoxamine mesylate in the soil reached 0.1 mmol / kg, so that the curve change trend of the amount of soluble uranium in the soil was consistent with the change trend of the amount of uranium enriched in Macleaya cordata, so as to maximize the enrichment of soluble uranium in the soil by Macleaya cordata plants and improve the efficiency of phytoremediation of uranium-contaminated soil.

[0057] Example 3 This example provides a method for improving the efficiency of phytoremediation of uranium-contaminated soil, comprising the following steps:

[0058] S1. Same as step S1 in Example 1.

[0059] S2. Same as step S2 in Example 1, except that the uranium hyperaccumulating plant is Coleus ovata.

[0060] S3. Coupling of uranium form transformation in soil and uranium enrichment by plants: According to the variation curve of the amount of soluble uranium in soil obtained in step S1 and the variation curve of the amount of uranium enriched in the aboveground and underground parts of scutellaria baicalensis obtained in step S2, the uranium concentration in the aboveground and underground parts of scutellaria baicalensis began to show a slow upward trend after 49 days. In the first 6 days after 49 days of planting scutellaria baicalensis, 10 mmol / L oxalic acid was added to the rhizosphere soil from the 43rd day to make the oxalic acid concentration in the soil reach 2 mmol / kg. Thereafter, 10 mmol / L oxalic acid was added to the rhizosphere soil every 15 days to make the oxalic acid concentration in the soil reach 2 mmol / kg. The variation trend of the curve of the amount of soluble uranium in soil was kept consistent with the variation trend of the amount of uranium enriched by scutellaria baicalensis, so as to maximize the enrichment of soluble uranium in soil by scutellaria baicalensis and improve the efficiency of plant remediation of uranium-contaminated soil.

[0061] Example 4 This example provides a method for improving the efficiency of phytoremediation of uranium contaminated soil, comprising the following steps:

[0062] S1. Same as step S1 in Example 2.

[0063] S2. Same as step S2 in Example 2, except that the uranium hyperaccumulating plant is Coleus ovata.

[0064] S3. Coupling of uranium form transformation in soil and uranium enrichment by plants: According to the change curve of the amount of soluble uranium in the soil obtained in step S1 and the change curve of the uranium enrichment in the aboveground and underground parts of the spatholobi obtained in step S2, 1 mmol / L deferoxamine mesylate was added to the rhizosphere soil on the 46th day, 3 days before the rising trend of the spatholobi slowed down from the 49th day, so that the concentration of deferoxamine mesylate in the soil reached 0.1 mmol / kg. Thereafter, 1 mmol / L deferoxamine mesylate was added to the rhizosphere soil every 15 days, so that the concentration of deferoxamine mesylate in the soil reached 0.1 mmol / kg, so that the curve change trend of the amount of soluble uranium in the soil was consistent with the change trend of the amount of uranium enriched by the spatholobi, so as to maximize the enrichment of soluble uranium in the soil by the spatholobi, and improve the efficiency of plant remediation of uranium-contaminated soil.

[0065] Example 5 This example provides a method for improving the efficiency of phytoremediation of uranium-contaminated soil, comprising the following steps:

[0066] S1. Same as step S1 in Example 1.

[0067] S2. Obtain the curve of the change of uranium enrichment in the aboveground and underground parts of uranium hyper-enriched plants: select the uranium hyper-enriched plant bamboo willow, where the bamboo willow is planted by cuttings, soaked in deionized water for a week and planted when the roots are 1 cm long. The size of the flower pot is 15.7cm×17cm×26.5cm. 5kg of uranium-contaminated farmland soil is added to each flower pot. The concentration of soluble uranium in the soil is 30mg / kg. Bamboo willows of the same growth size are planted in the flower pots respectively, and collected once a week, 3 plants are taken each time, and a total of 9 samples are taken. All plant cultivation is carried out in a greenhouse. During the experiment, the air temperature is maintained at 28°C and the humidity is 60%. The entire experiment lasts 63 days. After harvesting the plants, the uranium enrichment of the aboveground and underground parts of the plants is calculated, including the following steps:

[0068] B1. Harvest bamboo willows, rinse the roots once with 10 mM Na2CO3 and twice with deionized water;

[0069] B2. Fix the bamboo willow at 105℃ for 30 minutes, dry at 70℃ to constant weight, and weigh and record the dry weight of the above-ground and underground parts of the bamboo willow;

[0070] B3. Weigh 0.2000g of dried bamboo willow sample into a 200mL beaker, add 10mL nitric acid, heat and concentrate to 1-2mL on a hot plate, add 5mL nitric acid and 3mL perchloric acid after cooling, heat and concentrate to 1-2mL, cool, dilute with deionized water, filter and make up to volume in a 50mL volumetric flask, and use a trace uranium analyzer to detect the uranium content in the solution. The results are as follows: Figure 3 .

[0071] S3. Coupling of uranium form transformation in soil and uranium enrichment in plants: According to the change curve of the amount of soluble uranium in the soil obtained in step S1 and the change curve of the uranium enrichment in the aboveground and underground parts of the bamboo willow obtained in step S2, during the 63-day planting period, the uranium concentration in the aboveground and underground parts maintained an upward trend. The soil conditioner 1-oxalic acid or the soil conditioner 2-deferoxamine methanesulfonate should be added 6 days or 3 days before the inflection point value of the concentration decrease or the slowdown of the upward trend, so that the curve change trend of the amount of soluble uranium in the soil is consistent with the change trend of the amount of uranium enriched in the bamboo willow, so as to maximize the enrichment of soluble uranium in the soil by uranium bamboo willow. After experiments, it was finally determined that the time to add the soil conditioner 1-oxalic acid was the 98th day after the bamboo willow was transplanted. Starting from the 98th day after bamboo and willow transplantation, 10mmol / L oxalic acid was added to the rhizosphere soil to make the concentration of oxalic acid in the soil reach 2mmol / kg. Thereafter, 10mmol / L oxalic acid was added to the rhizosphere soil every 15 days to make the concentration of oxalic acid in the soil reach 2mmol / kg. The curve change trend of the amount of soluble uranium in the soil was consistent with the change trend of the amount of uranium enriched in bamboo and willow, so as to maximize the enrichment of soluble uranium in the soil by bamboo and willow and improve the efficiency of phytoremediation of uranium-contaminated soil.

[0072] Comparative Example 1 This comparative example is consistent with the steps of a method for improving the efficiency of phytoremediation of uranium-contaminated soil provided in Example 1, except that 10 mmol / L oxalic acid is added to the rhizosphere soil on the first day of planting Macleaya cordata to make the concentration of oxalic acid in the soil reach 2 mmol / kg, and thereafter, 10 mmol / L oxalic acid is added to the rhizosphere soil every 15 days to make the concentration of oxalic acid in the soil reach 2 mmol / kg.

[0073] Comparative Example 2 This comparative example is consistent with the method steps for improving the efficiency of phytoremediation of uranium-contaminated soil provided in Example 2, except that 1 mmol / L of deferoxamine mesylate is added to the rhizosphere soil on the first day of planting Macleaya cordata, so that the concentration of deferoxamine mesylate in the soil reaches 0.1 mmol / kg, and thereafter, 1 mmol / L of deferoxamine mesylate is added to the rhizosphere soil every 15 days, so that the concentration of deferoxamine mesylate in the soil reaches 0.1 mmol / kg.

[0074] Comparative Example 3 This comparative example has the same steps as the method for improving the efficiency of phytoremediation of uranium-contaminated soil provided in Example 3, with the difference being that 10 mmol / L oxalic acid is added to the rhizosphere soil on the first day of planting ophiopogon affine to bring the concentration of oxalic acid in the soil to 2 mmol / kg, and thereafter, 10 mmol / L oxalic acid is added to the rhizosphere soil every 15 days to bring the concentration of oxalic acid in the soil to 2 mmol / kg.

[0075] Comparative Example 4 This comparative example is consistent with the method steps for improving the efficiency of phytoremediation of uranium-contaminated soil provided in Example 4, except that 1 mmol / L of deferoxamine mesylate is added to the rhizosphere soil on the first day of planting smilax glabra, so that the concentration of deferoxamine mesylate in the soil reaches 0.1 mmol / kg, and thereafter, 1 mmol / L of deferoxamine mesylate is added to the rhizosphere soil every 15 days, so that the concentration of deferoxamine mesylate in the soil reaches 0.1 mmol / kg.

[0076] Comparative Example 5 This comparative example has the same steps as the method for improving the efficiency of phytoremediation of uranium-contaminated soil provided in Example 5, except that 10 mmol / L oxalic acid is added to the rhizosphere soil on the first day after bamboo willow transplantation to make the concentration of oxalic acid in the soil reach 2 mmol / kg, and thereafter, 10 mmol / L oxalic acid is added to the rhizosphere soil every 15 days to make the concentration of oxalic acid in the soil reach 2 mmol / kg.

[0077] Depend on Figure 1 It can be seen that under the action of soil conditioner 1-oxalic acid, the curve change trend of the amount of soluble uranium in the soil is as follows: when the concentration of soil conditioner 1-oxalic acid is 2.0mmol / kg, the soluble uranium content in the soil is the highest on the 6th day, and then it begins to decline. By the 15th day, it has basically returned to the level without adding soil conditioner 1-oxalic acid.

[0078] Depend on Figure 2 It can be seen that under the action of soil conditioner 2-deferoxamine methanesulfonate, the curve change trend of the amount of soluble uranium in the soil is as follows: when the concentration of soil conditioner 2-deferoxamine methanesulfonate is 0.1mmol / kg, the soluble uranium content in the soil is the highest on the third day, and then it begins to decline. By the 15th day, it has basically returned to the level without adding soil conditioner 2-deferoxamine methanesulfonate.

[0079] Depend on Figure 3It can be seen that the uranium content in the above-ground and underground parts of Boletus oleraceus showed the following trend, reaching the maximum value on the 14th day, and then gradually decreased with the passage of time; the uranium content in the above-ground and underground parts of Coleus ovata showed the following trend, within the 63rd day, the uranium concentration gradually increased with the passage of time, and after 49 days, the rising trend gradually slowed down; the uranium content in the above-ground and underground parts of Salix matsudana showed the following trend, within the 63rd day, the uranium concentration gradually increased with the passage of time, and the rising trend remained good within the 63-day time range.

[0080] The effects of the above embodiments and comparative examples were verified by the following experiments.

[0081] The harvested herbs were dried, crushed, burned, weighed, and digested. The uranium content in the digestion solution was determined using a trace uranium analyzer, and the uranium enrichment in the hyper-enriched plants was further calculated. The results are shown in Table 1.

[0082] Table 1 Total amount of uranium enrichment of various plants in the restoration cycle of the embodiments and comparative examples

[0083]

[0084] It can be seen from Table 1 that, compared with Comparative Example 1, the uranium enrichment of the Macleaya cordata in Example 1 is increased by 127.38%.

[0085] Compared with Comparative Example 2, the uranium enrichment of Macleaya cordata in Example 2 is increased by 52.17%.

[0086] Compared with Comparative Example 3, the uranium enrichment of D. edulis in Example 3 is increased by 119.52%.

[0087] Compared with Comparative Example 4, the uranium enrichment of D. edulis in Example 4 is increased by 89.95%.

[0088] Compared with Comparative Example 5, the uranium enrichment of bamboo willow in Example 5 is increased by 107.55%.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for improving the efficiency of phytoremediation of uranium-contaminated soil, characterized in that: The following steps are involved: S1. Obtaining a change curve of the amount of soluble uranium in the soil: determining the type and concentration range of soil conditioners that can effectively increase the proportion of soluble uranium in the soil, and drawing a change curve of the amount of soluble uranium in the soil under the action of the soil conditioners; S2. Obtaining the variation curve of the amount of uranium enrichment in the aboveground and underground parts of uranium hyper-enriched plants: determining the amount of enrichment of soluble uranium in the soil by the aboveground and underground parts of uranium hyper-enriched plants, and drawing the variation curve of the amount of uranium enrichment in the aboveground and underground parts of uranium hyper-enriched plants; S3. Coupling of uranium form transformation in soil and uranium enrichment in plants: According to the change curve of the amount of soluble uranium in the soil obtained in step S1 and the change curve of the amount of uranium enriched in the aboveground and underground parts of the uranium hyperaccumulating plants obtained in step S2, the type, content and addition time of the soil conditioner are regulated to make the curve change trend of the amount of soluble uranium in the soil consistent with the curve change trend of the amount of uranium enriched in the aboveground and underground parts of the uranium hyperaccumulating plants, so as to maximize the enrichment of soluble uranium in the soil by uranium hyperaccumulating plants and improve the efficiency of phytoremediation of uranium contaminated soil.

2. According to a method for improving the efficiency of phytoremediation of uranium-contaminated soil according to claim 1, in step S1, the soil conditioner comprises oxalic acid and deferoxamine mesylate, the concentration range of oxalic acid is 5-15 mmol / L, and the concentration range of deferoxamine mesylate is 0.05-2 mmol / L.

3. According to a method for improving the efficiency of phytoremediation of uranium-contaminated soil according to claims 1-2, the method for determining soluble uranium in soil comprises the following steps: A1. Accurately weigh 2.00 g of soil sample and place it into a 100 mL hard plastic round-bottom centrifuge tube with a lid; A2, add 16mL 1mol / L MgCl2 solution, pH = 7.0, and shake continuously at 25℃ for 1h; A3, centrifuge at 4000 rpm for 20 min, remove the supernatant and dilute to a 25 mL volumetric flask; A4. Wash the residue with deionized water, centrifuge at 4000 rpm for 20 min, filter all the supernatant, and determine the uranium concentration using a micro-uranium analyzer.

4. A method for improving the efficiency of phytoremediation of uranium contaminated soil according to claim 1, characterized in that: The concentration of soluble uranium in the soil is 0.02-150 mg / kg.

5. A method for improving the efficiency of phytoremediation of uranium contaminated soil according to claim 1, characterized in that: The steps for calculating the uranium enrichment of the above-ground part and the underground part of the uranium hyper-enriched plant include: B1. Harvest uranium hyperaccumulators, rinse roots once with 10 mM Na2CO3 and twice with deionized water; B2. The uranium hyperaccumulating plants were sterilized at 105°C for 30 minutes, dried at 70°C to constant weight, and the dry weight of the above-ground and underground parts of the uranium hyperaccumulating plants was weighed and recorded; B3. Weigh 0.2000g of dried uranium hyper-enriched plant sample into a 200mL beaker, add 10mL of nitric acid, heat and concentrate to 1-2mL on a hot plate, cool, add 5mL of nitric acid and 3mL of perchloric acid, heat and concentrate to 1-2mL, cool, dilute with deionized water, filter and make up to volume in a 50mL volumetric flask, and use a trace uranium analyzer to detect the uranium content in the solution.

6. According to the method for improving the efficiency of phytoremediation of uranium-contaminated soil according to claim 1, in step S3, the type of the regulated soil conditioner comprises one or both of oxalic acid and deferoxamine mesylate.

7. According to a method for improving the efficiency of plant remediation of uranium-contaminated soil according to claim 1, in step S3, the specific method for regulating the content and addition time of the soil conditioner is: according to the change curve obtained in step S2, 0.5-10mmol / L of soil conditioner is added to the rhizosphere soil 3-6 days before the highest point of uranium enrichment concentration in the above-ground and underground parts of the hyperaccumulator plant or the slowdown of the rising trend, so that the concentration of the soil conditioner in the soil reaches 0.02-2mmol / kg, and every 15 days, 0.5-10mmol / L of soil conditioner is added to the rhizosphere soil to make the concentration of the soil conditioner in the soil reach 0.02-2mmol / kg.

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