Method for improving soil heavy metal remediation efficiency of mulberries by utilizing michelia champaca

Abstract

The invention discloses a method for improving the soil heavy metal remediation efficiency of mulberries through plumeria champaca. The method comprises the following steps that 1, soil in a remediation area is pretreated; step 2, indoor domestication of Mimeria champaca; 3, mulberry seedlings are planted in the restoration area; step 4, putting plumeria rubra; 5, managing, regulating and controlling the repairing process; and 6, repairing the period. According to the method, a synergistic remediation system is constructed by utilizing the michelia champaca and the mulberries, efficient remediation of the soil heavy metals is achieved through the soil improvement effect and the heavy metal form transformation effect of the michelia champaca in combination with the enrichment capacity of root systems of the mulberries, and the technical blank of'specific and other foot soil animal-mulberry 'synergistic remediation in the prior art is filled up.

Description

Technical Field

[0001] This invention relates to the field of soil heavy metal remediation technology, and in particular to a method for improving the efficiency of mulberry tree remediation of soil heavy metals using Burmese worm. Background Technology

[0002] Soil heavy metal pollution (such as cadmium and lead pollution) is a key challenge in current agricultural environmental remediation. Heavy metals enter the food chain through crop absorption, seriously threatening human health. Mulberry trees, as perennial woody plants, have the characteristics of large biomass, long growth cycle, and a certain ability to accumulate various heavy metals, making them potential plants for soil heavy metal remediation. However, in existing technologies, mulberry trees have low absorption efficiency for heavy metals in deep soil layers, and their ability to transport heavy metals within the tree (from roots to above-ground parts) is insufficient, resulting in long remediation cycles and limited remediation effects. Current phytoremediation technologies for heavy metals in soil often involve screening mulberry varieties with strong heavy metal accumulation capabilities and applying chemical chelating agents (such as EDTA) to enhance the bioavailability of heavy metals. However, chemical chelating agents are prone to causing secondary pollution and cannot address the limitations of mulberry roots in absorbing heavy metals from deep soil layers. Some technologies introduce soil animals such as earthworms to improve soil structure, but conventional earthworms lack specificity in regulating the synergistic effect between mulberry trees and heavy metals, failing to establish a stable "soil animal-plant" synergistic remediation system, making it difficult to achieve breakthroughs in remediation efficiency.

[0003] Therefore, in order to solve the problems of "insufficient deep absorption, low translocation efficiency, and long remediation cycle" when using mulberry trees to remediate heavy metals in soil, this invention aims to provide a green and efficient method for remediating heavy metals in soil. Summary of the Invention

[0004] In view of this, the present invention provides a method for improving the efficiency of mulberry tree in remediating heavy metals in soil by using Pheretima magna; by constructing a synergistic remediation system with Pheretima magna, the soil improvement and heavy metal speciation effects of Pheretima magna, combined with the enrichment capacity of mulberry tree roots, can be achieved to remediate heavy metals in soil efficiently, filling the technical gap in the existing technology of synergistic remediation of "specific isopod soil animals-mulberry trees".

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for improving the efficiency of mulberry trees in remediating heavy metals in soil using Burmese worms includes the following steps: Step 1: Soil pretreatment in the remediation area Select 20 mu of soil contaminated with heavy metals, remove surface debris, till the soil, control soil bulk density, apply decomposed mulberry branch chips in furrows, and adjust soil pH. Step 2: Indoor domestication of Burmese worms Six thousand healthy adult Burmese worms were selected and transferred to the domestication and cultivation room for domestication. Step 3: Planting mulberry seedlings in the repaired area Determine the mulberry variety, plant mulberry seedlings, water thoroughly after planting, and manage during the growing season; Step 4: Release Burmese worms: After being domesticated for two months, Burmese mulberry worms were released into the pretreated remediation soil at a density of 2,000-3,000 worms per acre. Five release points were selected per acre, in the east, west, south, north, and center, and the worms were released through release tubes. The release tubes were hollow PVC tubes. A mixture of mulberry twigs and decaying mulberry leaves was placed in the release tubes, and then Burmese mulberry worms were inoculated into the release tubes. 600 worms were inoculated into each release tube, and the release was carried out twice a year. Step 5: Repair Process Management and Control Monitor the population density of Burmese worms. If the population density is less than 8,000 worms / acre, density control is required. To manage and regulate mulberry trees, measure the diameter at breast height (DBH) of the mulberry trees. If the growth rate is less than 1.0%, spray the mulberry tree leaves with a 0.2% EDTA-iron solution once a month for 2-3 consecutive months. Step 6: Repair Cycle Once the annual population density of Burmese mulberry larvae in the field soil stabilizes at 8,000 individuals / mu for more than 8 months, and the diameter at breast height (DBH) growth rate of mulberry trees is not less than 1.0%, the remediation period will be 18-26 months. Soil samples will then be collected for heavy metal testing. Remediation will be completed when the heavy metal content in the soil meets or falls below the risk screening value in the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (GB 15618-2018)". If it does not meet the standard, the remediation period will be extended until the heavy metal content in the soil reaches the national standard.

[0006] Preferably, in step 1, the selected areas have heavy metal content of 3.06-3.69 mg / kg total cadmium, 166-178 mg / kg lead, and pH 5.82, which meet the high-risk screening values ​​in the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (GB 15618-2018)".

[0007] Preferably, in step 1, the soil is tilled to a depth of 20-30 cm to control the soil bulk density at 1.1-1.3 g / cm³. 3 Apply well-rotted mulberry branch chips in the furrows at a rate of 1500-2000 kg / mu.

[0008] Preferably, in step 1, the soil pH is adjusted to 6.0-7.5 by using well-rotted organic fertilizer or lime powder, with the amount of organic fertilizer applied being 1000-1500 kg / mu.

[0009] Preferably, in step 2, healthy adult Burmese worms with a body length of 2cm and a weight of 0.02g are selected and transferred to an acclimatization and cultivation room for acclimatization for 30-45 days.

[0010] Preferably, in step 2, the acclimatization chamber contains 60 kg of acclimatization main substrate, which is the soil of the selected remediation area. Mulberry root secretion extract is added to the substrate at a rate of 5%-8% of the substrate mass. The chamber is ventilated 1-2 times a day to maintain substrate humidity at 60%-70%, and the temperature of the acclimatization chamber is controlled at 20-22℃.

[0011] Preferably, the extraction method for the mulberry root exudate extract is as follows: One-year-old hybrid mulberry roots were crushed and added to deionized water. The mixture was ultrasonically extracted for 2 hours at a mass ratio of 2:5. The filtrate was then filtered and the concentration was 0.5-1.0 g / mL.

[0012] Preferably, the specific method of step 3 is as follows: Step 3.1: Selection of Mulberry Varieties For fast-growing varieties with strong tolerance to heavy metals, such as Guisangyou 12, Huangma seedling mulberry, Xiujiang No. 3, and Xiujiang No. 5, select one-year-old seedlings with a plant height of 30-40cm, complete root system, and main root length ≥15cm. Step 3.2: Planting Method Plant mulberry seedlings at a density of 0.5m × 1.5m, with a planting hole depth of 25-30cm. Apply 50-100g of microbial inoculant to each hole and water thoroughly after planting. The microbial inoculant contains Bacillus subtilis: Trichoderma harzianum = 1:2, with an effective viable count ≥ 2 × 10⁻⁶. 8 CFU / g; Step 3.3: Growth Period Management After transplanting, cover the soil surface with a 2-3cm thick layer of straw, sawdust, or rice husks, and water 2-3 times a month to maintain soil moisture at 50%-60%.

[0013] Preferably, in step 4, the diameter of the placement tube is 20cm and the length is 15cm. The placement tube is placed at a 45-degree angle to the ground in the soil. Then, 800g of a mixture of mulberry branch debris and decaying mulberry leaves with a humidity of 80% is placed into the placement tube. The ambient temperature of the placement environment does not exceed 25℃.

[0014] Preferably, step 5 specifically comprises: Step 5.1: Monitoring the population density of Burmese worms Soil samples were collected every 3 months at a depth of 0-30cm using a five-point sampling method. The average number of samples was calculated to investigate the population density of Burmese worms in the soil. If the population density was less than 8,000 worms / acre, density control was required. The ground was sprayed with a conditioning solution twice a week for 2 weeks. The conditioning solution used was a mixture of dried silkworm pupa powder, freshwater mussel shell powder, and water in a mass ratio of 10:5:85. Step 5.2: Mulberry Tree Management and Control Measures Every March and October, till the soil to a depth of 20 cm and apply well-rotted mulberry branch chips in furrows, with a moisture content of not less than 75%, at a rate of 1500 kg / mu. Every 3 months, measure the diameter at breast height (DBH) of the mulberry trees at a height of 20 cm above the ground. If the growth rate is less than 1.0%, spray the mulberry tree leaves with a 0.2% EDTA-iron solution once a month for 2-3 consecutive months.

[0015] The present invention achieves the following technical effects compared to the prior art: (1) This invention utilizes the synergistic effect of Burmese worm and mulberry tree. Burmese worm can improve soil aeration by loosening the soil (increasing soil porosity by 15%-20%) and promote the growth of mulberry tree roots (increasing the length of the main root by 20%-30%). At the same time, the intestinal secretions of Burmese worm can convert insoluble heavy metals in the soil (such as sulfide-bound and residual forms) into soluble forms (such as exchangeable and carbonate-bound forms), thereby increasing the bioavailability of heavy metals by 30%-40% and significantly enhancing the absorption efficiency of mulberry tree for heavy metals. (2) Compared with traditional mulberry tree remediation methods, this invention can shorten the remediation cycle of soil heavy metals (cadmium, lead) by 40%-50%, and does not require the addition of chemical chelating agents, thus avoiding secondary pollution and conforming to the concept of green remediation. (3) The domestication process of Burmese worm in this invention, combined with the secretions of mulberry root system, can improve the adaptability of Burmese worm to the growth environment of mulberry tree (the survival rate is increased to more than 85%), forming a stable "Burmese worm-mulberry tree-soil" synergistic system, and the restoration effect is highly sustainable. Attached Figure Description

[0016] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention discloses a method for improving the efficiency of mulberry tree remediation of heavy metals in soil using Burmese worms, comprising the following steps: Step 1: Soil pretreatment in the remediation area Select 20 mu of soil contaminated with heavy metals, remove surface debris, till the soil, control soil bulk density, apply decomposed mulberry branch chips in furrows, and adjust soil pH. Step 2: Indoor domestication of Burmese worms Six thousand healthy adult Burmese worms were selected and transferred to the domestication and cultivation room for domestication. Step 3: Planting mulberry seedlings in the repaired area Determine the mulberry variety, plant mulberry seedlings, water thoroughly after planting, and manage during the growing season; Step 4: Release Burmese worms: After being domesticated for two months, Burmese mulberry worms were released into the pretreated remediation soil at a density of 2,000-3,000 worms per acre. Five release points were selected per acre, in the east, west, south, north, and center, and the worms were released through release tubes. The release tubes were hollow PVC tubes. A mixture of mulberry twigs and decaying mulberry leaves was placed in the release tubes, and then Burmese mulberry worms were inoculated into the release tubes. 600 worms were inoculated into each release tube, and the release was carried out twice a year. Step 5: Repair Process Management and Control Monitor the population density of Burmese worms. If the population density is less than 8,000 worms / acre, density control is required. To manage and regulate mulberry trees, measure the diameter at breast height (DBH) of the mulberry trees. If the growth rate is less than 1.0%, spray the mulberry tree leaves with a 0.2% EDTA-iron solution once a month for 2-3 consecutive months. Step 6: Repair Cycle Once the annual population density of Burmese mulberry larvae in the field soil stabilizes at 8,000 individuals / mu for more than 8 effective months each year, and the growth rate of mulberry tree diameter at breast height is not less than 1.0%, the remediation period is 18-26 months. After that, soil samples are collected for heavy metal testing. When the soil heavy metal content meets or falls below the risk screening value in the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (GB 15618-2018)," the remediation is completed. If it does not meet the standard, the remediation period is extended until the soil heavy metal content meets the standard.

[0019] In step 1, areas with heavy metal content of 3.06-3.69 mg / kg total cadmium, 166-178 mg / kg lead, and pH 5.82 were selected, meeting the high-risk screening values ​​in the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (GB 15618-2018)".

[0020] In step 1, the soil is tilled to a depth of 20-30cm to control the soil bulk density at 1.1-1.3g / cm³. 3 Apply well-rotted mulberry branch chips in the furrows at a rate of 1500-2000 kg / mu.

[0021] In step 1, adjust the soil pH to 6.0-7.5 by using well-rotted organic fertilizer or lime powder. The amount of organic fertilizer applied is 1000-1500 kg / mu.

[0022] In step 2, healthy adult Burmese worms with a body length of 2cm and a weight of 0.02g are selected and transferred to the domestication and cultivation room for 30-45 days.

[0023] In step 2, the acclimatization chamber contains 60 kg of acclimatization substrate, which is the soil of the selected remediation area. Mulberry root secretion extract is added to the substrate at a rate of 5%-8% of the substrate mass. The chamber is ventilated 1-2 times a day to maintain substrate humidity at 60%-70%, and the temperature of the acclimatization chamber is controlled at 20-22℃.

[0024] The extraction method for mulberry root exudate is as follows: One-year-old hybrid mulberry roots were crushed and added to deionized water. The mixture was ultrasonically extracted for 2 hours at a mass ratio of 2:5. The filtrate was then filtered and the concentration was 0.5-1.0 g / mL.

[0025] The specific method for step 3 is as follows: Step 3.1: Selection of Mulberry Varieties For fast-growing varieties with strong tolerance to heavy metals, such as Guisangyou 12, Huangma seedling mulberry, Xiujiang No. 3, and Xiujiang No. 5, select one-year-old seedlings with a plant height of 30-40cm, complete root system, and main root length ≥15cm. Step 3.2: Planting Method Plant mulberry seedlings at a density of 0.5m × 1.5m, with a planting hole depth of 25-30cm. Apply 50-100g of microbial inoculant to each hole and water thoroughly after planting. The microbial inoculant contains Bacillus subtilis: Trichoderma harzianum = 1:2, with an effective viable count ≥ 2 × 10⁻⁶. 8 CFU / g; Step 3.3: Growth Period Management After transplanting, cover the soil surface with a 2-3cm thick layer of straw, sawdust, or rice husks, and water 2-3 times a month to maintain soil moisture at 50%-60%.

[0026] In step 4, the placement tube has a diameter of 20cm and a length of 15cm. The placement tube is placed at a 45-degree angle to the ground in the soil. Then, 800g of a mixture of mulberry branch scraps and decaying mulberry leaves with a moisture content of 80% is placed into the placement tube. The ambient temperature for placement should not exceed 25℃.

[0027] Step 5 specifically involves: Step 5.1: Monitoring the population density of Burmese worms Soil samples were collected every 3 months at a depth of 0-30cm using a five-point sampling method. The average number of samples was calculated to investigate the population density of Burmese worms in the soil. If the population density was less than 8,000 worms / acre, density control was required. The ground was sprayed with a conditioning solution twice a week for 2 weeks. The conditioning solution used was a mixture of dried silkworm pupa powder, freshwater mussel shell powder, and water in a mass ratio of 10:5:85. Step 5.2: Mulberry Tree Management and Control Measures Every March and October, till the soil to a depth of 20 cm and apply well-rotted mulberry branch chips in furrows, with a moisture content of not less than 75%, at a rate of 1500 kg / mu. Every 3 months, measure the diameter at breast height (DBH) of the mulberry trees at a height of 20 cm above the ground. If the growth rate is less than 1.0%, spray the mulberry tree leaves with a 0.2% EDTA-iron solution once a month for 2-3 consecutive months.

[0028] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for improving the efficiency of mulberry tree remediation of heavy metals in soil using Burmese worms, characterized in that, Includes the following steps: Step 1: Soil pretreatment in the remediation area Select 20 mu of soil contaminated with heavy metals, remove surface debris, till the soil, control soil bulk density, apply decomposed mulberry branch chips in furrows, and adjust soil pH. Step 2: Indoor domestication of Burmese worms Six thousand healthy adult Burmese worms were selected and transferred to the domestication and cultivation room for domestication. Step 3: Planting mulberry seedlings in the repaired area Determine the mulberry variety, plant mulberry seedlings, water thoroughly after planting, and manage during the growing season; Step 4: Release Burmese worms: After being domesticated for two months, Burmese mulberry worms were released into the pretreated remediation soil at a density of 2,000-3,000 worms per acre. Five release points were selected per acre, in the east, west, south, north, and center, and the worms were released through release tubes. The release tubes were hollow PVC tubes. A mixture of mulberry twigs and decaying mulberry leaves was placed in the release tubes, and then Burmese mulberry worms were inoculated into the release tubes. 600 worms were inoculated into each release tube, and the release was carried out twice a year. Step 5: Repair Process Management and Control Monitor the population density of Burmese worms. If the population density is less than 8,000 worms / acre, density control is required. To manage and regulate mulberry trees, measure the diameter at breast height (DBH) of the mulberry trees. If the growth rate is less than 1.0%, spray the mulberry tree leaves with a 0.2% EDTA-iron solution once a month for 2-3 consecutive months. Step 6: Repair Cycle Once the annual population density of Burmese mulberry larvae in the field soil stabilizes at 8,000 individuals / mu for more than 8 effective months each year, and the growth rate of mulberry tree diameter at breast height is not less than 1.0%, the remediation period is 18-26 months. After that, soil samples are collected for heavy metal testing. When the soil heavy metal content meets or falls below the risk screening value in the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (GB 15618-2018)," the remediation is completed. If it does not meet the standard, the remediation period is extended until the soil heavy metal content meets the standard.

2. The method for improving the efficiency of mulberry tree remediation of heavy metals in soil using Burmese worms according to claim 1, characterized in that, In step 1, areas with heavy metal content of 3.06-3.69 mg / kg total cadmium, 166-178 mg / kg lead, and pH 5.82 are selected, which meet the high-risk screening values ​​in the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (GB 15618-2018)".

3. The method for improving the efficiency of mulberry tree remediation of heavy metals in soil using Burmese worms according to claim 1, characterized in that, In step 1, the soil is tilled to a depth of 20-30cm to control the soil bulk density at 1.1-1.3g / cm³. 3 Apply well-rotted mulberry branch chips in the furrows at a rate of 1500-2000 kg / mu.

4. The method for improving the efficiency of mulberry tree remediation of heavy metals in soil using *Bombyx mori* as described in claim 1, characterized in that, In step 1, the soil pH is adjusted to 6.0-7.5 by using well-rotted organic fertilizer or lime powder, with an application rate of 1000-1500 kg / mu.

5. A method for improving the efficiency of mulberry tree remediation of heavy metals in soil using Burmese worms according to claim 1, characterized in that, In step 2, healthy adult Burmese worms with a body length of 2cm and a weight of 0.02g are selected and transferred to an acclimatization and cultivation room for acclimatization for 30-45 days.

6. The method for improving the efficiency of mulberry tree remediation of heavy metals in soil using Burmese worms according to claim 1, characterized in that, In step 2, the acclimatization chamber contains 60 kg of acclimatization main substrate, which is the soil of the selected remediation area. Mulberry root secretion extract is added to the substrate at a rate of 5%-8% of the substrate mass. The chamber is ventilated 1-2 times a day to maintain substrate humidity at 60%-70%, and the temperature of the acclimatization chamber is controlled at 20-22℃.

7. A method for improving the efficiency of mulberry tree remediation of heavy metals in soil using Burmese worms according to claim 6, characterized in that, The extraction method for the mulberry root exudate extract is as follows: One-year-old hybrid mulberry roots were crushed and added to deionized water. The mixture was ultrasonically extracted for 2 hours at a mass ratio of 2:

5. The filtrate was then filtered and the concentration was 0.5-1.0 g / mL.

8. A method for improving the efficiency of mulberry tree remediation of heavy metals in soil using *Bombyx mori* as described in claim 1, characterized in that, The specific method for step 3 is as follows: Step 3.1: Selection of Mulberry Varieties For fast-growing varieties with strong tolerance to heavy metals, such as Guisangyou 12, Huangma seedling mulberry, Xiujiang No. 3, and Xiujiang No. 5, select one-year-old seedlings with a plant height of 30-40cm, complete root system, and main root length ≥15cm. Step 3.2: Planting Method Plant mulberry seedlings at a density of 0.5m × 1.5m, with a planting hole depth of 25-30cm. Apply 50-100g of microbial inoculant to each hole and water thoroughly after planting. The microbial inoculant contains Bacillus subtilis: Trichoderma harzianum = 1:2, with an effective viable count ≥ 2 × 10⁻⁶. 8 CFU / g; Step 3.3: Growth Period Management After transplanting, cover the soil surface with a 2-3cm thick layer of straw, sawdust, or rice husks, and water 2-3 times a month to maintain soil moisture at 50%-60%.

9. A method for improving the efficiency of mulberry tree remediation of heavy metals in soil using *Bombyx mori* as described in claim 1, characterized in that, In step 4, the placement tube has a diameter of 20cm and a length of 15cm. The placement tube is placed at a 45-degree angle to the ground in the soil. Then, 800g of a mixture of mulberry branch debris and decaying mulberry leaves with a humidity of 80% is placed into the placement tube. The ambient temperature for placement does not exceed 25℃.

10. A method for improving the efficiency of mulberry tree remediation of heavy metals in soil using Burmese worms according to claim 1, characterized in that, Step 5 specifically involves: Step 5.1: Monitoring the population density of Burmese worms Soil samples were collected every 3 months at a depth of 0-30cm using a five-point sampling method. The average number of samples was calculated to investigate the population density of Burmese worms in the soil. If the population density was less than 8,000 worms / acre, density control was required. The ground was sprayed with a conditioning solution twice a week for 2 weeks. The conditioning solution used was a mixture of dried silkworm pupa powder, freshwater mussel shell powder, and water in a mass ratio of 10:5:

85. Step 5.2: Mulberry Tree Management and Control Measures Every March and October, till the soil to a depth of 20 cm and apply well-rotted mulberry branch chips in furrows, with a moisture content of not less than 75%, at a rate of 1500 kg / mu. Every 3 months, measure the diameter at breast height of the mulberry tree at a height of 20 cm above the ground. If the growth rate is less than 1.0%, spray the mulberry tree leaves with a 0.2% EDTA-iron solution once a month for 2-3 consecutive months.

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