CN113728748B

CN113728748B - Soil improvement method for greening soil after thermal desorption remediation

Info

Publication number: CN113728748B
Application number: CN202111026290.3A
Authority: CN
Inventors: 王国玉; 穆晓红; 曲辰; 刘睿; 张敬玉; 白伟岚
Original assignee: China Urban Construction Design and Research Institute Co Ltd
Current assignee: China Urban Construction Design and Research Institute Co Ltd
Priority date: 2021-09-02
Filing date: 2021-09-02
Publication date: 2022-05-06
Anticipated expiration: 2041-09-02
Also published as: CN113728748A

Abstract

The invention discloses a method for improving soil after thermal desorption remediation of greening soil. The method comprises the following steps: 1) preparing a soil conditioner, wherein the soil conditioner mainly comprises landscaping wastes, fermented livestock and poultry manure and microbial fertilizer; 2) uniformly mixing the soil conditioner, planting soil and the soil subjected to thermal desorption remediation according to the volume ratio of 1:0.9-1.1:1.8-2.2 to obtain thermal desorption remediation modified soil, wherein the planting soil refers to soil with a surface layer of 10-30 cm; 3) and backfilling the thermal desorption restoration improved soil into a greening planting area, compacting, sprinkling water, and planting and maintaining plants. After treatment, the physical and chemical indexes and biological indexes of the soil are well recovered. The improvement method overcomes the defect that the ecological function of the soil is damaged or lost after thermal desorption restoration, has simple and convenient operation, low cost, safety, effectiveness and no secondary environmental risk, widens the source of the greening backfill soil, solves the problem of resource utilization of the restored soil and has better popularization value.

Description

Soil improvement method for greening soil after thermal desorption remediation

Technical Field

The invention relates to the technical field of soil treatment and improvement, in particular to a method for recycling and improving soil greening soil after thermal desorption remediation.

Background

The thermal desorption technology is a restoration technology capable of efficiently removing pollutants in soil, is mainly suitable for removing volatile and semi-volatile organic pollutants in soil, has the characteristics of high pollutant removal rate, short restoration period, movable equipment, strong adaptability, capability of recycling the restored soil and the like, and is widely applied to restoration of contaminated sites such as soil and sludge polluted by volatile and semi-volatile organic matters. However, the soil thermal desorption can also cause destructive changes to the physical and chemical properties and ecological functions of the soil, such as the destruction of bedding structures and aggregate structures, the loss of organic matters, water and carbonate minerals, the loss of soil animals, plants and microorganisms, and the like, the loss of main ecological functions and slow natural recovery. The recent aim of soil remediation is to achieve a certain remediation standard for the content of a certain pollutant in soil, and to restore the original ecological function in the long term. In the current domestic soil heating desorption repair engineering practice, the soil pollutant content reaches the standard as the main target, the foundation pit is usually backfilled in situ in the repaired soil, the foundation pit is used for leveling the soil as the main resource utilization way, the restoration of the ecological function of the soil is not emphasized, and the site risk management and control after the repair are not facilitated.

As an important urban infrastructure, the ecological quality in urban green lands is not optimistic, and one of the important reasons is that overground plant parts are generally valued and underground soil quality is ignored. The soil is used as a medium for the growth of green plants and a carrier for the function of the green plants, is the foundation of the whole green land system and is also the root of the high-quality development of the whole urban ecological infrastructure. At present, the outstanding problems of resource soil shortage such as poor soil quality, high compactness, insufficient soil depth and the like, and functional soil shortage caused by incomplete management system exist in the green land soil aspect of multi-land cities in China.

Disclosure of Invention

The invention solves the technical problem that the soil after thermal desorption remediation is reprocessed to restore the ecological function of the soil and is used as green land or vegetation soil.

The invention provides a soil improvement method for greening soil after thermal desorption remediation, which comprises the following steps:

1) preparing a soil conditioner, wherein the soil conditioner mainly comprises landscaping wastes, fermented livestock and poultry manure and microbial fertilizer;

2) uniformly mixing the soil conditioner, planting soil and the soil subjected to thermal desorption remediation according to the volume ratio of 1:0.9-1.1:1.8-2.2 to obtain thermal desorption remediation modified soil, wherein the planting soil refers to soil with a surface layer of 10-30 cm;

3) and backfilling the thermal desorption restoration improved soil into a greening planting area, compacting and sprinkling water.

The thermally desorbed remediated soil is screened to remove impurities as needed.

In a typical embodiment of the invention, the soil conditioner is mainly prepared from the following raw materials in parts by weight: 90-95 parts of garden greening waste, 5-10 parts of fermented livestock manure and 0.5-1 part of microbial fertilizer.

Preferably, the pH value of the soil conditioner is adjusted to be 6.8-7.3, wherein the content of organic matters is not less than 23%, and the contents of total nitrogen, total phosphorus and total potassium are not less than 1%, 0.8% and 1.25% respectively.

The improved soil of the invention can be used for green land restoration, nursery cultivation and non-edible crop planting (such as cotton). After planting for e.g. 3 years, it can also be used for the planting of food crops. Preferably, leguminous herbaceous plants are planted in the planting process, and then local shrubs and trees are planted in the second growing season.

According to the method for recycling and improving the soil greening soil after thermal desorption restoration, the initial restoration of the ecological function of the soil after thermal desorption restoration is realized through proportioning improvement; the soil resource utilization and environmental risk management and control after restoration are completed through backfilling and compaction; the reconstruction and the restoration of the ecological function of the soil are completed through planting and maintaining the plants, and a stable ecological relation of the soil and vegetation is established. The method makes up the defect that the ecological function of the soil is damaged or lost after thermal desorption remediation, is simple and convenient to operate, safe and effective, has no secondary environmental risk, practically reduces the soil treatment cost, widens the source of greening backfill soil, solves the problem of resource utilization of the remedied soil, and has good popularization value.

Drawings

FIG. 1 is a flow chart of a method according to the present invention;

FIG. 2 is a plant map of a planting box in an embodiment of the present invention;

FIG. 3 is a graph showing the change in the growth height of malachite grass;

FIG. 4 is a graph showing statistics of the flowering of maidenhair;

FIG. 5 is a graph showing statistics of the size of the flowers of maidenhair;

FIG. 6 is a graph showing the variation in high growth of rye grass;

FIG. 7 is a graph showing rye grass coverage statistics;

FIG. 8 is a graph showing variation in height growth of roses;

FIG. 9 is a graph showing variation in the basal diameter growth of roses;

FIG. 10 is a photograph of plants at each time period of each example.

Detailed Description

In the invention, landscaping waste refers to plant materials such as arbor and shrub trimmings (intermediate cuts), lawn trimmings, fallen leaves, branches, waste grass and flowers in gardens and flower beds, weeds and the like generated in the natural or maintenance process of greening plants in urban green lands or suburb forest lands. It is envisioned by those skilled in the art that the intent of the present invention may also be accomplished with herbal or woody plant stalks. These wastes are usually prepared as powders, for example, with a particle size not exceeding 2 mm. Preferably, the material is fermented prior to use. Such fermented landscaping waste can be obtained commercially.

In the invention, the microbial fertilizer is preferably bacterial fertilizer for increasing soil nitrogen and crop nitrogen nutrition, such as rhizomatous bacterial fertilizer, nitrogen-fixing blue algae fertilizer and the like. On the basis, bacterial manure with other functions can be added, such as bacterial manure for stimulating plant growth, such as growth-promoting bacterial manure; bacterial manure for improving stress resistance of crop root systems, such as antibiotic fertilizer and stress-resistant bacterial fertilizer. The microbial fertilizer used in the embodiment of the invention is a microbial fertilizer produced by Standby agriculture group, Inc. of Shandong province.

The invention uses a compound soil conditioner which is mainly prepared from the following raw materials in parts by weight: 90-95 parts of fermentation and crushing landscaping waste, 5-10 parts of fully fermented livestock and poultry manure and 0.5-1 part of commercial microbial fertilizer, and uniformly mixing. The pH value of the compound soil conditioner is 6.8-7.3, the content of organic matters is not less than 23%, and the content of total nitrogen, total phosphorus and total potassium is not less than 1%, 0.8% and 1.25% respectively.

The invention is also characterized in that the soil improvement agent is compounded with the planting soil and the thermal desorption remediation soil according to the volume ratio of 1:0.9-1.1:1.8-2.2 to obtain the thermal desorption remediation soil improvement soil. Experiments show that the proportion is particularly important for restoring the ecological capability of the soil. The planting soil is soil with the surface depth of the plantable land being less than 30 cm.

The thermal desorption remediation soil improvement soil is backfilled or covered to a required place, compacted and applied with a proper amount of water to provide proper humidity for the soil. Preferably, the backfill bottom should be above the highest water level of the groundwater, more preferably at least 1.0m from the surface of the groundwater, and the bottom is preferably laid with a clay barrier layer of thickness not less than 0.5 m.

In general, the land filled with the improved soil can be used as a greening land. Where the contaminants comprise heavy metals or highly toxic metals such as chromium, thermal desorption remediation is insufficient to eliminate their toxicity, and to prevent the possibility of contact of the backfill with humans and animals, the improved soil may be covered with additional in situ planted soil, typically 5-15cm thick, typically no more than 10cm thick.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described with reference to the attached drawings in the implementation of the method, and the following embodiments are used for illustrating the present invention, but are not limited to the scope of the present invention.

The soil of the embodiment of the invention is from the soil repaired in a certain site of the stone landscape mountain area in Beijing, the soil is silty clay, the in-situ ex-situ thermal desorption technology is adopted for repairing, and the soil after thermal desorption repair meets the index value specified in GB 36000-2018. The landscaping waste is derived from fermentation treatment products of Beijing XuanChun environmental technology Limited liability company. In this example, the herbaceous plants are maidenhair and ryegrass, and the shrub plants are Chinese roses. Planting with 5 planting boxes of 1m2 as shown in figure 1, wherein the planting density of rye grass is 20-30g/m2, the planting density of maidenhair is 250 clusters/m 2 (3 plants per cluster), and the planting distance of Chinese rose is 12-15 cm. And collecting the growth process data of the plants in each planting box, and calculating the average value of the single plants.

Example 1

Firstly, carrying out thermal desorption remediation treatment on the polluted soil to reach the utilization standard of landscaping soil;

step two, compounding a soil conditioner, and uniformly stirring 90 parts of landscaping waste, 10 parts of fully fermented livestock and poultry manure and 1 part of commercial microbial fertilizer to obtain the compounded soil conditioner;

and thirdly, mixing the compound soil conditioner, the planting soil and the treated thermal desorption remediation soil according to the ratio of 1:1:2, and fully and uniformly mixing.

And fourthly, reasonably distributing areas in the planting box, planting herbs and shrubs respectively, and maintaining and managing. Recording initial data, recording data according to 60 days in the early stage of plant growth, and then acquiring data samples according to 30 days, wherein the observation period of herbs and shrubs is 6 months and 8 months respectively. As shown in fig. 3 to fig. 10, the growth state of the vegetation of the sparrow is good, the growth period is 6 months, the plant height is increased by 0.89 cm/month, the flowering period of the sparrow is 5 months, the flower diameter is 3cm, the overall flowering rate reaches 100%, and the inflorescence state is good; the height of the ryegrass is increased by 5 cm/month, the coverage reaches 100%, the yellow leaves at the base account for 10%, and the leaves are normal in color; the Chinese rose grows well, the plant height growth rate reaches 86%, the base diameter growth rate is 14.7%, and the whole body has good performance.

Example 2

secondly, applying a soil conditioner, uniformly stirring the compounded soil conditioner according to 90 parts of landscaping wastes, 10 parts of fully fermented livestock and poultry manure and 1 part of commercial microbial fertilizer to obtain the compounded soil conditioner, wherein the application ratio is 2.02kg/m²；

And thirdly, mixing the compound soil conditioner, the planting soil and the treated thermal desorption remediation soil according to the ratio of 2:1:2, and fully and uniformly mixing.

And fourthly, reasonably distributing areas in the planting box, and carrying out maintenance, management, data acquisition and observation on the areas in the planting box in the same way as in the embodiment 1. The malachite vegetation has good expression state, the growth cycle is 6 months, the plant height is increased by 0.39 cm/month, the flowering period is 5 months, the diameter of flowers is 2cm, the overall flowering rate reaches 75%, and the inflorescence state is good; the height of the ryegrass is increased by 3.7 cm/month, the integral coverage reaches 70%, yellow leaves exist at the base part, the percentage of the yellow leaves is 30%, and the leaves are slightly light in color; the Chinese rose grows well, the plant height growth rate reaches 54 percent, the base diameter growth rate is 0.8 percent, and the performance is better.

Example 3

and thirdly, mixing the compound soil conditioner and the treated thermal desorption remediation soil according to the ratio of 2:1, and fully and uniformly mixing.

Fourthly, reasonably distributing areas in the planting box, planting herbs and shrubs respectively, maintaining, managing, collecting data and observing the plants, wherein the height of the peacock grass is increased by 0.21 cm/month, the flowering rate is reduced compared with the examples 1 and 2, the growth state of the plants is lagged, the flowering period is 5 months, the diameter of the flowers is 2cm, the overall flowering rate reaches 60%, and the inflorescence state is general; the height of the ryegrass is increased by 2 cm/month, the integral coverage reaches 70%, the proportion of yellow leaves reaches 60% along with the growth of plants, and the color of the leaves is slightly light; the plant height growth rate of the Chinese rose reaches 74%, the growth rate of the basal diameter is 1.4%, and the whole performance is good.

Example 4 (control one)

and step two, reasonably distributing areas in the planting box, and maintaining and managing.

Data collection and observation were performed as in example 1. The vegetation growth state is general, the ratio of the yellow grass leaves is 25%, the survival rate of shrub growth is 80%, and the overall performance is poor. Specifically, the survival period of the malachite grass is only 4 months, the survival rate of the plants in the growth period is only 30%, the plant height is increased by 0.025 cm/month, and the plants have no inflorescence; the height of the ryegrass is increased by 3.3 cm/month, the character is that the yellow leaves at the base part reach 25 percent, and the leaves are darker in color; the plant height growth rate of the Chinese rose is 61%, the color of the Chinese rose leaves is darker and is influenced by soil properties, the basal diameter growth rate is 0.2%, and the overall performance is poor.

Example 5 (control two)

The areas of the planting soil in the planting box are reasonably distributed, and the maintenance, management, data acquisition and observation are the same as those in the embodiment 1. The survival period of the peacock is only 6 months, the height of the survival plant is increased by 0.85 cm/month, the growth of the peacock is influenced by the growth of ryegrass, the growth period of the peacock plant is shorter, but the flowering rate of the plant reaches 100%, the diameter of the flower is 3cm, and the inflorescence state is good; the ryegrass has the largest growth change, the growth period is 5 months, the height is increased by 7.5 cm/month, and the leaves of the plant have no yellow leaf symptom and have normal color; the rose is influenced by ryegrass, the plant height growth rate is 79 percent, the rose is influenced by the growth of the ryegrass, the growth period of the basal diameter is only 4 months, the growth rate of the basal diameter is 1.4 percent, and the whole performance is good.

Claims

1. A soil improvement method used after thermal desorption remediation of green soil comprises the following steps:

2) uniformly mixing the soil conditioner, planting soil and soil subjected to thermal desorption remediation according to the volume ratio of 1:0.9-1.1:1.8-2.2 to obtain thermal desorption remediation modified soil, wherein the planting soil is soil with a surface layer of 10-30cm, and the soil conditioner is mainly prepared from the following raw materials in parts by weight: 90-95 parts of landscaping waste, 5-10 parts of fermented livestock manure and 0.5-1 part of microbial fertilizer;

2. A method according to claim 1, wherein the thermal desorption remediated soil used is screened to remove impurities.

3. The method of claim 1, wherein the soil conditioner has a pH of 6.8 to 7.3, an organic matter content of not less than 23%, and total nitrogen, total phosphorus and total potassium contents of not less than 1%, 0.8% and 1.25%, respectively.

4. The method of claim 1, wherein the backfilling technique is as follows: the backfill bottom is at least 1.0m higher than the highest water level of the underground water, and a clay barrier layer with the thickness of not less than 0.5m is preferably paved at the bottom.

5. The method according to claim 1, wherein in the step 3), surface soil covering is further performed, and 5-10cm of in-situ planting soil is covered on the backfilled thermal desorption remediation modified soil.