Heavy metal contaminated soil remediation method with bamboo reed planting coupled with melatonin application

Abstract

The invention relates to the technical field of soil remediation, and particularly discloses a heavy metal contaminated soil remediation method by coupling bamboo reed planting with melatonin application, which comprises the following steps: selecting healthy bamboo reed rhizomes with plump buds, and cutting the rhizomes into rhizome sections with the length of 8-15cm and at least 2-3 buds; preparing a melatonin working solution with the concentration of 50M to 300M; the rhizome sections are completely soaked in the melatonin working solution for 2 hours to 8 hours; furrowing is conducted according to the line spacing of 60 cm to 100 cm and the plant spacing of 40 cm to 60 cm, rhizome sections are planted in furrows, the soil covering thickness is 5 cm to 10 cm, and root fixing water is thoroughly watered; s3, when the bamboo reed seedlings grow 3-5 true leaves, the melatonin working solution is used for carrying out leaf surface spraying for the first time; then, spraying is carried out once every 15 days to 30 days; according to the method, an optimized bamboo reed rhizome breeding and planting technology is combined with exogenous melatonin application, so that the synergistic interaction of physical planting and physiological strengthening is realized.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation technology, specifically relating to a method for remediating heavy metal contaminated soil by coupling the planting of Phragmites communis with the application of melatonin. Background Technology

[0002] In the field of soil heavy metal pollution remediation, existing technologies mainly fall into two categories: one is single phytoremediation technology, which involves directly planting hyperaccumulating plants or plants with strong tolerance (such as Reed) to absorb and accumulate heavy metals in the soil through their natural growth process, and then removing the pollutants by harvesting; the other is chemically enhanced phytoremediation technology, which usually involves adding chelating agents (such as EDTA) or surfactants to the soil during the plant growth process to activate heavy metals and improve their bioavailability, thereby enhancing the plant's extraction efficiency of heavy metals.

[0003] However, among the aforementioned existing technologies, single phytoremediation techniques are limited by problems such as low seed germination rates, unstable seedling survival, and slow early growth of plants under heavy metal stress. This results in a lengthy establishment process for the remediation system, and when the pollution concentration exceeds the plant's tolerance threshold, the plants are susceptible to toxicity, biomass decreases, and remediation efficiency is limited. While chemical enhancement techniques can improve plant extraction efficiency in the short term, the exogenous chemical chelating agents used are difficult to degrade, easily causing heavy metals to leach into deep soil or groundwater, leading to secondary pollution risks. They may also be toxic to the plants themselves, and their effectiveness is greatly affected by soil environmental factors, resulting in high costs and insufficient stability. Therefore, none of the existing technologies have been able to simultaneously achieve rapid and healthy establishment of plants in contaminated soil and efficient and safe heavy metal enrichment enhancement. Summary of the Invention

[0004] The purpose of this invention is to provide a method for remediating heavy metal contaminated soil by coupling Reed Plant cultivation with melatonin application, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for remediating heavy metal contaminated soil by coupling Reed Plant cultivation with melatonin application includes the following steps:

[0007] S1. Select healthy rhizomes of Reed and plump buds, cut them into rhizome segments with a length of 8cm to 15cm and containing at least 2-3 buds; prepare a melatonin working solution with a concentration of 50µM to 300µM; and completely immerse the rhizome segments in the melatonin working solution for 2 to 8 hours.

[0008] S2. In heavy metal contaminated soil, dig trenches with a row spacing of 60cm to 100cm and a plant spacing of 40cm to 60cm. Plant the rhizome segments treated in step S1 in the trenches, cover them with soil to a thickness of 5cm to 10cm, and water them thoroughly.

[0009] S3. When the Reed seedlings have grown 3 to 5 true leaves, apply the melatonin working solution for the first foliar spray; thereafter spray once every 15 to 30 days, for a total of 3 to 5 sprays throughout the growing season.

[0010] S4. Monitor the growth status of Reed and changes in soil heavy metal content during the growth process. Harvest the above-ground parts of Reed at the end of the growing season or when the biomass reaches its peak, and safely treat the harvested plants to remove heavy metals.

[0011] Preferably, the concentration of the melatonin working solution is 100µM to 200µM.

[0012] Preferably, in step S1, the diameter of the rhizome of *Arundinaria salsa* is 0.5 cm to 2.0 cm.

[0013] Preferably, in step S1, the melatonin working solution is prepared by first dissolving the melatonin with ethanol of a volume concentration not exceeding 1%, and then diluting it with deionized water or distilled water to the target concentration.

[0014] Preferably, a surfactant is added to the melatonin working solution at a volume ratio of 0.01% to 0.1%.

[0015] Preferably, in step S1, the soaking process is carried out at 20°C to 25°C, accompanied by intermittent oscillation.

[0016] Preferably, in step S2, the content of the target heavy metal in the heavy metal contaminated soil is between 50 mg / kg and 800 mg / kg.

[0017] Preferably, in step S3, the foliar spraying is performed until both sides of the leaf are evenly moistened without dripping.

[0018] Preferably, step S3 also includes applying compound fertilizer during the tillering and / or jointing stages of Phyllostachys edulis.

[0019] Application of a method as described in any of the above in the remediation of copper, cadmium and / or zinc contaminated soil.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) By combining the optimized rhizome propagation and planting technology of Reed hyacinth with the exogenous application of melatonin, the synergistic effect of "physical establishment" and "physiological enhancement" was achieved, overcoming the difficulties of early establishment and slow growth of Reed hyacinth in heavy metal contaminated soil, improving the survival rate of seedlings and plant biomass, and providing a stable and efficient plant carrier for the remediation process; furthermore, through the physiological regulation of melatonin, an endogenous signaling molecule, the tolerance of Reed hyacinth to heavy metal stress was systematically enhanced, and its absorption of heavy metals and translocation to the aboveground parts were specifically promoted, thereby greatly improving the pollutant removal efficiency per unit time and fundamentally shortening the remediation cycle.

[0022] (2) It avoids the risk of secondary pollution caused by the use of chelating agents in traditional chemical fortification technology. Melatonin, as an environmentally friendly biological agent, is safe and easy to degrade. It is easy to operate and cost-controllable. Through the organic combination of agronomic measures and physiological regulation, the stability and reliability of the remediation effect can be guaranteed. Attached Figure Description

[0023] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0024] 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.

[0025] Example 1:

[0026] Please see Figure 1 As shown, a method for remediating heavy metal contaminated soil by planting Reed amurense coupled with melatonin application includes the following steps:

[0027] S1. Material Preparation and Pretreatment:

[0028] Select healthy, disease-free, one-year-old rhizomes of Reed (Phragmites australis), with a diameter between 0.8 cm and 1.5 cm, and plump, undamaged buds. Cut the rhizomes into 10 cm to 12 cm long sections, each containing 2 to 3 healthy buds. After cutting, place them in a cool, well-ventilated place to dry slightly (about 30 minutes) to reduce sap loss from the cut surfaces.

[0029] Preparation of melatonin working solution: Weigh an appropriate amount of melatonin powder, dissolve it in 0.5% anhydrous ethanol by volume, shake gently until completely dissolved, then add deionized water to make up the volume to obtain a melatonin working solution with a concentration of 150 µM. To enhance adhesion, add 0.05% (volume ratio) of Tween-20 as a surfactant to the working solution and mix well.

[0030] Completely immerse the cut Reed rhizome segments in the above-mentioned melatonin working solution and soak for 4 hours at room temperature (22℃±2℃). Gently shake the container once every hour during this period to ensure that the rhizome segments are evenly contacted with the solution.

[0031] S2, Planting and Establishment:

[0032] Select soil contaminated with heavy metals (in this example, copper contamination is the main one, with a Cu content of about 300 mg / kg in the soil), plow and level it, and dig furrows with a row spacing of 80 cm and a plant spacing of 50 cm, with a furrow depth of about 8 cm to 10 cm.

[0033] Place the soaked reed rhizome segments horizontally in the trench, ensuring the buds are facing upwards. Cover with soil to a thickness of about 6 to 8 cm, gently compact it, and then water thoroughly to settle the roots, maintaining the soil moisture content at 70% to 80% of field capacity.

[0034] S3, Intensive Management During the Growth Period:

[0035] When the Reed seedlings emerge from the soil and grow 4 true leaves (about 20 to 25 days after planting), carry out the first foliar spraying. Use the same concentration of melatonin working solution as in step S1, and spray it evenly on both sides of the leaves with a sprayer until the leaves are moist but no liquid drips.

[0036] Spray once every 20 days thereafter, for a total of 4 sprays throughout the growing season. Apply nitrogen, phosphorus and potassium compound fertilizer (N:P2O5:K2O=15:15:15) once during the tillering and jointing stages of Reed, at a rate of about 30 kg per acre, to promote biomass accumulation.

[0037] S4. Monitoring and Harvesting:

[0038] Soil and plant samples were collected on the 60th and 120th day after planting, respectively. The residual amount of Cu in the soil and the enrichment amount of Cu in the roots, stems and leaves of Reed are determined. The analysis is carried out according to the national standards "Determination of Copper, Zinc, Lead and Cadmium in Soil Quality" (GB / T 17139-1997) and "Determination of Heavy Metals in Plants" (GB / T 5009.13-2017).

[0039] At the end of the growing season (approximately 180 days after planting), when the reed plants reach a height of 2.5 to 3.0 meters and the biomass tends to stabilize, the above-ground parts are harvested at ground level. After harvesting, the reed biomass is dried and sent to a biomass power plant for energy utilization. The ash from combustion is collected and heavy metals are recovered, achieving the safe removal of pollutants.

[0040] After implementation of this embodiment, the survival rate of Reed hyacinth in polluted soil reached 92%, which is about 28% higher than that of the untreated control group; the average aboveground biomass (dry weight) was 3.8 tons per mu, which is about 45% higher than that of the control group; the total amount of Cu extracted from the soil by Reed hyacinth increased by about 65%, and the content of available Cu in the soil decreased by about 40%.

[0041] Example 2:

[0042] This embodiment provides a method for remediating heavy metal contaminated soil by coupling melatonin application with reed planting, specifically for remediating soil contaminated with both cadmium (Cd) and zinc (Zn). The specific steps are as follows:

[0043] S1. Material Preparation and Pretreatment:

[0044] Select healthy rhizomes of Reed (Prunus armeniaca) with dense buds, and control the diameter to be between 1.0 cm and 1.8 cm. Cut the rhizomes into segments with a length of 9 cm to 13 cm, ensuring that each segment contains 3 plump buds;

[0045] Preparation of melatonin working solution: First, dissolve melatonin in 1% ethanol (volume concentration), then dilute with deionized water to obtain a working solution with a concentration of 100 µM. Add 0.03% (volume ratio) of agricultural organosilicon adjuvant (surfactant) to improve adhesion. Completely immerse the root and stem segments in the working solution and soak at 25°C for 6 hours, gently shaking every 2 hours during this period.

[0046] S2, Planting and Establishment:

[0047] Mechanical tillage and leveling were carried out in cadmium- and zinc-contaminated soil (Cd content approximately 60 mg / kg, Zn content approximately 450 mg / kg). Furrows were dug with a row spacing of 70 cm and a plant spacing of 45 cm, and a furrow depth of approximately 7 cm to 9 cm. The pre-treated rhizome segments were then inserted obliquely (at approximately 45° angle) into the furrows with the buds facing upwards. The soil was covered with approximately 7 cm of soil, and after light pressing, the roots were thoroughly watered.

[0048] S3, Intensive Management During the Growth Period:

[0049] When the seedlings have grown 3 true leaves, perform the first foliar spray using the above-mentioned 100 µM melatonin working solution, spraying evenly until the leaves are moist. Spray once every 25 days thereafter, for a total of 3 sprays throughout the growing season. At the jointing stage of the reed, apply a low-chlorine compound fertilizer (N:P2O5:K2O=12:12:12) at a rate of 25 kg per acre.

[0050] S4. Monitoring and Harvesting:

[0051] Samples were taken on the 90th and 150th day after planting to determine the total and available Cd and Zn content in the soil, as well as the heavy metal enrichment in different parts of Reed hyacinth. Inductively coupled plasma mass spectrometry (ICP-MS) was used for detection.

[0052] Harvest the above-ground parts at the end of the growing season (about 160 days after planting, when the plant height is about 2.2 m–2.6 m). After drying, the harvested material can be used as a heavy metal solidification material or sent to a qualified hazardous waste treatment unit for resource recycling.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for remediating heavy metal contaminated soil by coupling the planting of giant reed (Arundo donax) with the administration of melatonin, characterized in that, The method comprises the following steps: S1, selecting healthy and full-bud Arundo donax rhizomes, cutting the rhizomes into 8-15 cm long segments containing at least 2-3 bud points, and preparing a melatonin working solution with a concentration of 50-300 µM; completely immersing the rhizome segments in the melatonin working solution for 2-8 hours; S2, in heavy metal contaminated soil, digging a ditch with a row distance of 60-100 cm and a plant distance of 40-60 cm, planting the rhizome segments treated in step S1 in the ditch, covering the soil with a thickness of 5-10 cm, and pouring water to fix the roots; S3, when the Arundo donax seedlings grow 3-5 true leaves, using the melatonin working solution for the first time leaf spraying; then spraying once every 15-30 days, a total of 3-5 times during the whole growth season; S4, monitoring the growth status and soil heavy metal content during the growth of Arundo donax, and at the end of the growth season or when the biomass reaches the peak, harvesting the aboveground parts of Arundo donax in unison, and safely disposing of the harvested plants to remove heavy metals.

2. A method for remediating heavy metal contaminated soil by growing Arundo donax coupled with melatonin application according to claim 1, characterized by the fact that: The concentration of the melatonin working solution is 100-200 µM.

3. A method for remediating heavy metal contaminated soil by growing Arundo donax coupled with melatonin application as claimed in claim 1, wherein: In step S1, the diameter of the Arundo donax rhizome is 0.5-2.0 cm.

4. A method of remediating heavy metal contaminated soil by growing Arundo donax coupled with melatonin application as claimed in claim 1, wherein, In step S1, the preparation method of the melatonin working solution is: first, dissolving melatonin with ethanol with a volume concentration of not more than 1%, and then diluting with deionized water or distilled water to the target concentration.

5. A method of remediating heavy metal contaminated soil by growing Arundo donax coupled with melatonin application as claimed in claim 1, wherein: A surfactant with a volume ratio of 0.01%-0.1% is also added to the melatonin working solution.

6. A method of remediating heavy metal contaminated soil by growing reed coupled with melatonin application according to claim 1, characterized in that: In step S1, the soaking process is carried out at 20-25°C with intermittent oscillation.

7. A method of remediating heavy metal contaminated soil by growing reed coupled with melatonin administration according to claim 1, characterized in that: In step S2, the content of the target heavy metal in the heavy metal contaminated soil is 50-800 mg / kg.

8. A method of remediating heavy metal contaminated soil by growing reed coupled with melatonin application according to claim 1, characterized in that: In step S3, the leaf spraying is carried out until the front and back of the leaves are evenly wetted and no dripping occurs.

9. A method of remediating heavy metal contaminated soil by growing reed coupled with melatonin administration according to claim 1, characterized in that: Step S3 also includes applying compound fertilizer during the tillering and / or jointing stage of Arundo donax.

10. Use of the method according to any one of claims 1-9 for repairing copper, cadmium and / or zinc contaminated soil.

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