Artificial conditioning method for recovering production function of soil after thermal desorption

Abstract

The invention discloses an artificial conditioning method for recovering the production function of soil after thermal desorption. The method comprises the following steps: cooling the soil after thermal desorption treatment to room temperature, then mixing the soil with pollution-free natural soil according to a volume ratio of 1: 1, applying plant growth-promoting bacteria methylobacterium, maintaining the water content to be 30-40%, incubating for 7 days, and sowing and planting ryegrass for 1-3 months. After treatment, the key enzyme activity, the plant germination rate, the plant growth amount and the microbial diversity of the soil are remarkably improved compared with those of untreated soil subjected to thermal desorption, and sustainable utilization of the soil subjected to thermal desorption remediation is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of soil ecological restoration, and in particular to an artificial conditioning method for soil after thermal desorption treatment. Background Art

[0002] Thermal desorption technology heats the soil to change the physical and chemical properties of pollutants, causing them to volatilize or decompose, thereby separating pollutants from the soil. Thermal desorption technology has the advantages of good pollutant removal effect, short treatment time, wide application range, and large treatment volume. It has been widely used in soil remediation of heavily polluted sites. However, while thermal desorption technology removes pollutants, it may also have a great impact on the ecological function of the soil. The soil after heat treatment is actually no longer soil in the traditional sense, and its ecological and production functions have significantly degraded.

[0003] At present, the soil after thermal desorption is mainly used as building materials or backfill, with a poor utilization rate, and its ecological and production functions cannot be fully utilized, resulting in a waste of resources. In particular, the soil after low-temperature thermal desorption remediation treatment, in which most of its organic matter and mineral structure are retained, still has the possibility of biological community restoration, and it is entirely possible to restore its production function through artificial intervention. However, to date, there has been no complete and operational artificial intervention conditioning method for restoring the production function of soil after thermal desorption. Summary of the invention

[0004] The present invention is based on many years of research by this research group. Simple and economical artificial conditioning of the soil after thermal desorption can effectively improve the soil microbial diversity, key enzyme activity and crop germination rate in a short period of time, and effectively restore the production function of the soil after thermal desorption.

[0005] The artificial conditioning method for restoring the production function of soil after thermal desorption comprises the following steps:

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] Step 1, enriching and culturing the plant growth-promoting bacteria Methylobacterium in a common bacterial culture medium;

[0008] Step 2: Cool the soil after thermal desorption to room temperature and mix it evenly with unpolluted farmland soil in a ratio of 1:1;

[0009] Step 3, diluting the cultured and enriched Methylobacterium suspension to obtain a growth-promoting bacterial suspension;

[0010] Step 4: Spray the growth-promoting bacteria suspension into the mixed soil at one time, water the soil appropriately to keep the soil moisture content at 30% to 40% on the same day, and incubate at room temperature for 7 days.

[0011] Step 5: Sow the seeds and plant the ryegrass for 1 to 3 months, watering and maintaining it normally during this period.

[0012] The aforementioned growth-promoting bacteria is Methylobacterium extorquens C1, which is an endophyte isolated from ryegrass. The strain is deposited in China Center for Type Culture Collection, with the deposit number CCTCCNO: M2019060, and the deposit address is Wuhan University, Wuhan, China.

[0013] The common bacterial culture medium in the above step 1 is beef extract peptone liquid culture medium, including: 3g beef extract, 10g peptone, 5g NaCl, 1000mL water, pH 7.4-7.6.

[0014] The concentration of the diluted Methylobacterium suspension in the above step 3 is OD600 value of 1.0.

[0015] In the aforementioned step 4, the spraying amount of the growth-promoting bacterial suspension is 12 mL per kg of soil.

[0016] In the aforementioned step 4, after the growth-promoting bacteria suspension is sprayed, tap water is evenly sprinkled every day starting from the same day to keep the soil moisture content in the range of 30% to 40%, and the incubation is carried out for a total of 7 days.

[0017] After sowing the ryegrass seeds in step 5, continue to plant the ryegrass for 1 to 3 months. During this period, water the soil normally depending on the dryness of the soil to maintain the soil moisture content at about 25%.

[0018] The benefit of the present invention lies in that the present invention found that after mixing the soil after thermal desorption with farmland soil in a 1:1 ratio and inoculating plant growth-promoting bacteria at the same time, most of the dominant bacterial communities in the farmland soil can colonize and grow in the mixed soil. The inoculation of growth-promoting bacteria helps the stress resistance of late ryegrass, improves the growth quality of ryegrass, and significantly helps the recovery of soil aggregate structure and microbial diversity after 1 to 3 months. Planting vegetables in the conditioned soil can obtain a yield close to that of normal soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow chart of an embodiment of the present invention;

[0020] Figure 2 This is a comparison diagram of vegetable yield effects in two embodiments of the present invention; DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Embodiment 1:

[0023] Taking the soil after thermal desorption and remediation at a coal gasification enterprise site in Shanxi as an example, 20 kg of thermal desorbed soil was mixed with uncontaminated local farmland soil in a 1:1 ratio and stirred evenly. 48 mL of Methylobacterium suspension with an OD value of 1.0 was sprayed at one time, and then 15 L of water was added and stirred again to mix evenly. For the next 7 days, tap water was added every day depending on the dryness of the soil to keep its moisture content at 30-40%. On the 8th day, the above soil was divided into pots, with 3 kg per pot, and ryegrass seeds were sprinkled in the pots, and ryegrass was planted in the pots for 3 months. The 7-day germination rate, 14-day germination rate, average plant height and root length of ryegrass after 30 days were significantly higher than those of untreated thermal desorbed soil, and there was no significant difference with local farmland soil. Samples were taken and analyzed after the first month of planting ryegrass, and the activities of urease, alkaline phosphatase and dehydrogenase in the soil were significantly higher than those in local farmland soil (p<0.05). After 3 months, ryegrass was removed and early-maturing No. 5 green vegetables were planted. The germination rate and growth of green vegetables in the artificially conditioned soil were significantly higher than those in the unconditioned thermal desorption soil control (p<0.05), and there was no significant difference with the local farmland soil, indicating that the productivity of the thermal desorption soil has been restored.

[0024] Embodiment 2:

[0025] Taking the soil after thermal desorption and remediation of the former Maanshan Iron and Steel Plant as an example, 20kg of thermal desorbed soil was mixed with uncontaminated local farmland soil in a 1:1 ratio and stirred evenly. Spray 48mL of Methylobacterium suspension with an OD value of 1.0 at one time, add 15L of water, and stir again to mix evenly. For the next 7 days, tap water was added every day depending on the dryness of the soil to keep its moisture content at 30-40%. On the 8th day, the above soil was divided into pots, with 3kg per pot, and ryegrass seeds were sprinkled in the pots, and ryegrass was planted in the pots for 3 months. The 7-day germination rate, 14-day germination rate, average plant height and root length of ryegrass after 30 days were significantly higher than those of untreated thermal desorbed soil, and there was no significant difference with local farmland soil. Samples were taken and analyzed after the first month of planting ryegrass, and the activities of urease, alkaline phosphatase and dehydrogenase in the soil were significantly higher than those in unconditioned soil (p<0.05), and there was no significant difference with local farmland soil. After 3 months, ryegrass was removed and then large-leafed chrysanthemum was planted. The germination rate and growth of chrysanthemum in the artificially conditioned soil were significantly higher than those in the unconditioned thermal desorption soil control (p<0.05), and there was no significant difference with the local farmland soil, indicating that the productivity of the thermal desorption soil has been restored.

[0026] The above two embodiments respectively take the soil after thermal desorption treatment of soil from different contaminated sites as an example, and implement the soil conditioning method of the present invention. Compared with the unconditioned soil, the enzyme activity and microbial diversity of the soil are significantly improved after 3 months, and the vegetable productivity is not significantly different from that of the local uncontaminated farmland soil.

[0027] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. An artificial conditioning method for restoring soil production function after thermal desorption, characterized in that: The method comprises: 1) Enrich and culture the plant growth-promoting bacteria, Methylobacterium, in ordinary bacterial culture medium; 2) Cool the soil after thermal desorption to room temperature and mix it evenly with unpolluted farmland soil in a ratio of 1:1; 3) diluting the cultured and enriched Methylobacterium suspension to obtain a growth-promoting bacterial suspension; 4) Spray the growth-promoting bacteria suspension into the mixed soil at one time, water the soil appropriately to keep the soil moisture content at 30% to 40% on the same day, and incubate at room temperature for 7 days. 5) Sow the ryegrass for 1 to 3 months, and water and maintain it normally during this period.

2. The artificial conditioning method for restoring soil production function after thermal desorption according to claim 1, characterized in that: The growth-promoting bacteria is Methylobacterium extorquens C1, which is an endophyte isolated from ryegrass. The strain is deposited in China Center for Type Culture Collection, with a deposit number of CCTCC NO: M2019060, and the deposit address is Wuhan University, Wuhan, China.

3. The artificial conditioning method for restoring soil production function after thermal desorption according to claim 1, characterized in that: In step 1), the common bacterial culture medium is a beef extract peptone liquid culture medium, comprising: 3 g beef extract, 10 g peptone, 5 g NaCl, 1000 mL water, and pH 7.4-7.

6.

4. The artificial conditioning method for restoring soil production function after thermal desorption according to claim 1, characterized in that: In step 3), the Methylobacterium suspension is diluted to an OD600 value of 1.

0.

5. The artificial conditioning method for restoring soil production function after thermal desorption according to claim 1, characterized in that: In step 4), the spraying amount of the growth-promoting bacteria suspension is 12 mL per kg of soil.

6. The artificial conditioning method for restoring soil production function after thermal desorption according to claim 1, characterized in that: In step 4), after the growth-promoting bacteria suspension is sprayed, tap water is evenly sprinkled every day starting from the same day to make the soil moisture content in the range of 30% to 40%, and the incubation is carried out for 7 days in total.

7. The artificial conditioning method for restoring soil production function after thermal desorption according to claim 1, characterized in that: In step 5), after incubation for 7 days, ryegrass is sown and cultivated on the 8th day, and watered normally for 1 to 3 months depending on the dryness of the soil to maintain the soil moisture content at about 25%.

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