CN110157442B

CN110157442B - Passivation material for repairing cadmium-copper polluted soil and repairing method of passivation material combining with agronomic measures

Info

Publication number: CN110157442B
Application number: CN201910196786.1A
Authority: CN
Inventors: 周静; 梁家妮; 张娜; 祝振球; 华进城
Original assignee: Institute of Soil Science of CAS
Current assignee: Institute of Soil Science of CAS
Priority date: 2019-03-15
Filing date: 2019-03-15
Publication date: 2021-02-09
Anticipated expiration: 2039-03-15
Also published as: CN110157442A

Abstract

A passivation material for repairing cadmium-copper polluted soil and a repairing method of the passivation material combined with an agronomic measure. The passivation material has the pH value of 10-13 and the particle size of 1-3 mm, and is prepared from biomass power plant ash, lime, apatite and an organic fertilizer; wherein the mass percentages of the materials are as follows: 60% of biomass power plant ash, 20% of lime, 10% of apatite and 10% of organic fertilizer; the combined agricultural measures comprise passivation material application dosage, plant planting time, density, cultivation mode and soil moisture control. The passivation material and the combined remediation method thereof can effectively promote the transformation of heavy metals Cd and Cu in soil from a usable state to a potentially usable state or an unusable state, promote plant growth and biomass accumulation while stabilizing/solidifying the heavy metals Cd and Cu, and improve the land productivity and economic benefits; the method has the advantages of wide material source, low price, simple and easy combined restoration method, high restoration efficiency and stability, so the method has high economic benefit, ecological benefit, restoration application and popularization value.

Description

Passivation material for repairing cadmium-copper polluted soil and repairing method of passivation material combining with agronomic measures

Technical Field

The invention belongs to the technical field of heavy metal contaminated soil remediation, and particularly relates to a passivation material for remedying cadmium and copper contaminated soil and a remediation method combining the passivation material with an agronomic measure.

Background

In most areas in the south of the Yangtze river in China, the influence of climate and environment changes, such as temperature, acid rain and strong rainfall, the soil is acidic (the pH is more than 5.6), the soil is mainly characterized in that the salt base in the soil is highly unsaturated, iron and aluminum oxides are obviously accumulated, and the problems of organic matter deficiency, insufficient supply of nitrogen, phosphorus and potassium, less content of effective calcium and magnesium and the like exist, so that the productivity of the soil is limited. In addition, Guixi City in Jiangxi provinceThe production of copper smelters results in the soil in the surrounding and downstream areas being heavily contaminated with heavy metals. The pollutants mainly comprise heavy metals of copper and cadmium, and the copper content on the surface layer of the soil is up to 102-2300 mg kg^-1The cadmium content is 0.39-6.87 mgkg^-1. According to the secondary standard of the national soil environment quality standard (GB 15618-. Therefore, the problems of repairing and improving the cadmium-copper polluted soil in the area need to be solved urgently.

The material for improving the heavy metal contaminated soil mainly comprises calcareous substances, phosphates, inorganic mineral substances and organic materials. The traditional method for improving acid soil is to use lime or limestone powder to improve the pH value of the soil and reduce the content of effective heavy metals. However, the application of lime in large amount or for a long time can not only cause soil hardening, but also enhance the soil acidification degree, and cause imbalance of the balance of 3 elements of calcium, potassium and magnesium in the soil. In contrast, biomass power plant ash, as an alkaline material, has been used as an acidic soil conditioner. The soil acidity is regulated, and simultaneously, the contents of silicon, potassium and zinc in the soil can be increased, and the soil hardening is relieved. The biomass power plant ash refers to residual ash generated by converting chemical energy into heat energy through combustion of wastes such as straws and chaffs generated in agricultural production. CN 103497771A and CN 102424639B only relate to soil conditioners taking biomass power plant ash as a main raw material, but do not relate to the problem of remediation of heavy metal contaminated soil. CN 102329620B uses the biomass power plant ash for the restoration of heavy metal polluted acid soil, but the proportion of the biomass power plant ash is only 10-20%, and different materials are only sieved and mixed to prepare the high-efficiency heavy metal polluted acid soil, so that doubts exist as to whether the difficulty of overcoming the difficulty of scattering powdery materials is doubted. Similar problems exist with CN 104690087 a. Meanwhile, the above invention only describes the preparation or use method of the passivation material, but lacks the agronomic control technology in the process of plant restoration. The agricultural measures such as soil moisture condition, fertilization type and quantity, cultivated plant type, cultivation mode, cultivation system and the like play an important role in regulating or improving chemical passivation effect and plant restoration efficiency. However, few studies have been made to date concerning the effect of agronomic control measures on soil remediation, and no combined remediation technology has been reported for the new model "chemical inactivation + phytoremediation + agronomic control".

Disclosure of Invention

The technical problem to be solved is as follows: the invention provides a passivation material for repairing cadmium-copper polluted soil and a repairing method of a combined agronomic measure thereof, so as to form a combined repairing technology and concept of a new mode of chemical passivation, plant repairing and agronomic regulation. The passivation material takes green and cheap biomass power plant ash as a main material, is uniformly mixed with lime, apatite and organic fertilizer, is produced by granulation, and is combined with reasonable application dosage, cultivation mode, plant planting time, density, soil moisture control and other agricultural measures to repair polluted soil. The combined remediation method can promote the transformation of heavy metals cadmium and copper in the soil from a usable state to a potentially usable state and an unusable state, effectively passivate the heavy metals cadmium and copper, improve the soil properties (soil pH and nutrient elements) and facilitate the growth of plants, thereby achieving the aim of low-cost, high-efficiency and stable in-situ remediation of the heavy metals cadmium and copper polluted soil.

The technical scheme is as follows: a passivation material for repairing cadmium-copper polluted soil comprises the following materials in percentage by mass: 60% of biomass power plant ash, 20% of lime, 10% of apatite and 10% of organic fertilizer, 10-13% of pH, and the particle size is less than or equal to 3 mm.

The passivation material for repairing cadmium-copper polluted soil contains 14% of organic matter, 14% of phosphorus, 14% of calcium and silicon by mass percentage, and P₂O₅4%, CaO 7% and SiO₂ 13％。

The organic fertilizer is fermented cow dung.

The preparation method of the passivation material for repairing cadmium-copper polluted soil comprises the following steps of 1) drying raw materials: drying the raw materials of each component until the water content of the raw materials does not exceed 1 wt.%; 2) sieving: all materials were sieved through 60 mesh sieves respectively; 3) preparing materials: weighing the materials according to the mass ratio, placing the materials in a stirrer, and stirring for 2-3 min to mix uniformly; 4) and (3) granulation: a centrifugal granulator and a rounding machine are utilized, the temperature is controlled to be 50-60 ℃, the rotating speed is controlled to be 20r/min, the water content is controlled to be 40%, spherical particles with the particle size being less than or equal to 3mm are formed, and the granulation rate of the raw materials is 98%; 5) and (3) drying: and after granulation, drying at the temperature of 70-150 ℃ until the water content is less than or equal to 10 wt%, and then bagging and sealing.

The passivation material is applied to repairing cadmium and copper polluted soil by combining with an agricultural measure.

Preferably, the application amount of the passivation material accounts for 0.2-0.6 percent of the mass percentage of the plough layer soil within 17cm, the pH value of the cadmium-copper polluted soil is 5.56, and the volume weight is 1.31g/cm³。

And after the passivation material is applied, the plant planting or sowing is completed within 0-3 days of soil balance.

Preferably, the planted plants are pennisetum sinese roxb, and the density is 60 × 80 cm.

The plant cultivation method comprises the steps of spreading flat culture, spreading ridge culture or ridge culture, wherein the ridge width of the ridge culture planting is 40cm, the ridge interval is 40cm, and the ridge height is 30 cm; the step of spreading and leveling comprises the steps of land preparation, spreading of passivation materials, plowing, stirring, leveling and planting of plants; the step of spreading the ridge culture comprises the steps of preparing soil, spreading a passivator, then turning over, stirring and ridging, wherein the ridge width is 40cm, the ridge interval is 40cm, and the ridge height is 30 cm; the ridge planting step comprises the steps of land preparation, ploughing, ridge forming and ridge applying of a passivator, wherein the ridge width is 40cm, the ridge interval is 40cm, and the ridge height is 30 cm.

Preferably, the soil moisture after cultivation is controlled to be 40-60 wt% of the maximum moisture capacity in the field.

The experimental result shows that the application amount of the passivation material is 0.2-0.6% of the soil mass of a plough layer of 17cm, the soil moisture is controlled to be 40-60% of the maximum water holding capacity in the field, a ridge-applying and ridge-planting cultivation mode is adopted, and the planting density of the pennisetum giganteum is that the plant spacing is multiplied by the row spacing to be 60cm multiplied by 80 cm. The combined remediation method can promote the soil heavy metals cadmium and copper to be converted from the available state to the potential available state and the unavailable state, namely from the exchangeable state to the carbonate combined state, the iron-manganese oxide combined state, the organic combined state and the residue state, plays a role in stabilizing/solidifying heavy metals Cd and Cu, effectively remediates the heavy metal cadmium-copper contaminated soil, can improve the pH value of the soil and increase elements such as phosphorus and silicon in the soil, promotes the growth of plants, and is beneficial to ecological restoration.

In conclusion, the biomass power plant ash, the lime, the apatite and the fermented cow dung are prepared into particles according to a certain proportion and used as a passivation material for repairing the heavy metal cadmium copper polluted soil, and a reasonable agricultural regulation and control technology is combined, so that the problem that the powdery material is difficult to broadcast and apply is solved, the problems of long-term stability repair and nutrition improvement of the heavy metal cadmium copper polluted soil are solved, the problem of post-treatment of industrial and agricultural and livestock wastes is relieved, and the development of natural minerals and negative environmental effects brought by the development of the natural minerals are reduced.

The mechanism for repairing and improving the heavy metal cadmium copper polluted soil passivation material is as follows: the alkaline biomass power plant ash has the effects of supplementing elements such as potassium and silicon in soil and improving the pH value of the soil, and the main component of the alkaline biomass power plant ash is exchanged with cadmium and copper ions to effectively passivate the activity of heavy metals in acid soil; the lime can effectively improve the pH value of the acid soil and activate Ca²⁺Forming a metal hydroxide precipitate by a coprecipitation reaction; the apatite is a common base fertilizer, can increase the phosphorus content of the soil, improve the pH value of the soil, and increase the negative charge on the surface of the soil through the surface adsorption and complexation of the apatite, so that the adsorption quantity of heavy metals is increased; the fermented cow dung can improve the contents of organic matters, quick-acting nitrogen, phosphorus and potassium in acid soil, obviously improve the pH value and the fertility of the soil, and a large amount of mineral components contained in the fermented cow dung are easy to form precipitates with heavy metal pollutants. The method is characterized in that the ash of the biomass power plant, lime, apatite and fermented cow dung are prepared into a round granular passivation material according to a certain proportion for application, and a reasonable regulation and control technology is adopted to effectively improve the pH value of soil, supplement soil nutrients, promote the conversion of cadmium and copper to a potential utilizable state and a potential non-utilizable state, stabilize/solidify the activity of heavy metals, reduce the toxicity of the heavy metals, promote the growth of plants and the accumulation of biomass, and take away more heavy metals.

Has the advantages that: 1) the raw materials of the invention have wide sources, are easy to obtain, have low price, and the solid wastes in the industry and the agriculture and livestock industry are recycled to prepare ecological, economic and multifunctional green materials; 2) the production process is simple and easy to implement, and overcomes the difficulty that the powdery material is difficult to spread; 3) the organic fertilizer utilizes cow dung, and compared with pig dung generated in a large-scale pig farm (containing high heavy metal and not suitable for a comprehensive conditioner for repairing polluted soil), the organic fertilizer has low heavy metal content, and can obviously improve the contents of organic matters, quick-acting nitrogen, phosphorus and potassium in acid soil, the pH value and the fertility of the soil and the passivation and adsorption capacity of heavy metal in the soil; 4) is suitable for in-situ remediation and improvement of large-range heavy metal copper and cadmium polluted soil. Therefore, the combined remediation method of the passivation material combined with the agronomic regulation and control measures ensures that the remediation effect of the cadmium-copper polluted soil is remarkable, the soil property can be improved, the soil productivity can be improved, and the ecological benefit, the economic benefit, the remediation effect and the social popularization value are integrated.

Drawings

FIG. 1 is a graph showing the effect of different passivation materials on soil pH and the content of Cd and Cu in an active state; wherein (A) is the content of Cu in an effective state of soil; (B) the content of Cd in the soil active state is obtained; (C) is the soil pH.

FIG. 2 is a graph showing the influence of different passivation materials on the height, tillering number and biomass of a pennisetum hydridum plant; wherein (A) is the height of the pennisetum hydridum; (B) the tillering number of the Jujun grass is obtained; (C) is the biomass of the pennisetum hydridum.

FIG. 3 is a diagram showing the influence of different passivation materials on the Cd content in different chemical forms in soil; wherein (A) is exchangeable Cd content; (B) is the content of Cd in a carbonate bonding state; (C) the content of Cd in the oxidation state of ferro-manganese; (D) the content of Cd in an organic binding state; (E) the content of Cd in the residue state.

FIG. 4 is a graph of the effect of different passivation materials on Cu content for different chemical morphologies. Wherein (A) is exchangeable Cu content; (B) is the carbonate bound Cu content; (C) is the Cu content of iron and manganese in oxidation state; (D) cu content in organic bonding state; (E) the Cu content is in the form of residue.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

EXAMPLE 1 passivation Material culture experiment

And collecting the polluted soil in the soil of a typical cadmium and copper soil polluted farmland. As a Control (CK), farmland soil to which no passivation material was applied included biomass power plant ash (D), apatite (L), lime (S), cow dung (O), biomass power plant ash: apatite: lime 6:1:1 mass ratio composite (DLS), biomass power plant ash: apatite: lime: cow dung-composite (DLSO) at a mass ratio of 6:2:1:1 for a total of 7 treatments, each of which was repeated 3 times. And (3) sieving the air-dried farmland soil by a 10-mesh sieve, adding 2g of passivation materials into every 1kg of soil, namely, uniformly mixing the passivation materials accounting for 0.2 percent of the soil by mass. The soil pH and the content of available Cu and Cd were measured on days 7, 14, 28, 42 and 77 respectively after continuous culture for 77 days at constant temperature and humidity (temperature 25 ℃ and humidity 40%), and the results are shown in tables 1, 2 and 3.

The result shows that the ash, the apatite and the lime of the biomass power plant can obviously improve the pH value of the soil and reduce the Cu and Cd contents of the effective state of the soil within 77 days of continuous culture, but the effect of prolonging the cow dung with a single material is not obvious. The order of the magnitude of the heavy metal passivation effect of the four single materials is lime > apatite > biomass power plant ash > cow dung (tables 1, 2 and 3). However, the application of lime in large amount or for a long time not only causes soil hardening but also strengthens the soil re-acidification degree, and also causes imbalance of the balance of 3 elements of calcium, potassium and magnesium in the soil. On the contrary, studies have shown that apatite is more stable in increasing soil pH and passivating heavy metals than lime, and has the effect of supplementing phosphorus, calcium and magnesium in soil. Although the effect of improving the soil pH and stabilizing Cd and Cu by using the biomass power plant ash made of a single material is relatively smaller than that of lime and apatite, the biomass power plant ash can supplement potassium and silicon elements in soil and has obvious price advantage. In addition, although the effect of passivating the heavy metals in the soil by the organic fertilizer cow dung is relatively small, the organic fertilizer cow dung can improve the contents of organic matters, quick-acting nitrogen, phosphorus and potassium in the soil and improve the fertility of the soil. Therefore, the cheap industrial waste biomass power plant ash can be used as a main raw material, and the composite material is prepared by properly adding lime, apatite and organic fertilizer, so that the defect of a single repairing material can be overcome, and the dual purposes of soil repairing and improving are achieved.

In the treatment of the composite material, the DLS and DLSO materials both obviously improve the pH value of the soil and reduce the content of Cd and Cu in the effective state of the soil, and the repairing effects of the DLS and DLSO materials are not obviously different and are both obviously larger than that of the biomass power plant ash made of a single material. In terms of material cost, the cost price of DLS and DLSO is 170 and 246 respectively according to the biomass power plant ash of 60 yuan/ton, the apatite of 500 yuan/ton, the lime of 500 yuan/ton and the cow dung of 600 yuan/tonYuan/ton. While the cost of the passivation material DLSO is high, it is only one-half of the cost of lime. In terms of ecological benefit, the main nutrient elements of DLS are phosphorus and silicon accounting for 26 percent (P)₂O₅ 7％+SiO₂19 percent) and DLSO is rich in organic matters, phosphorus, calcium and silicon, and the mass percent of the DLSO reaches 38 percent (the organic matter is 14 percent + P)₂

O

₅ 4％+CaO 7％+SiO₂13% in total). Therefore, the DLSO material can effectively passivate heavy metals copper and cadmium in soil, and can also effectively solve the problems of lack of organic matters in acid soil, low content of effective calcium and magnesium and the like. In terms of environmental benefits, DLSO makes full use of industrial and agricultural and livestock wastes, and reduces ecological environment damage caused by the mining and exploiting processes of natural minerals.

In conclusion, the passivation material DLSO can solve the problems of remediation and improvement of heavy metal contaminated soil, can relieve the problem of post-treatment of industrial and agricultural and livestock wastes, reduces development of natural minerals and negative environmental effects brought by the development of natural minerals, and has great ecological benefit, economic benefit and soil remediation application value.

TABLE 1 Effect of different passivating materials on the pH of contaminated soil

Note: d represents biomass power plant ash; l represents apatite; s represents lime; o represents fermented cow dung; DLS denotes biomass power plant ash: apatite: lime is a composite material with the mass ratio of 6:1: 1; DLSO represents biomass power plant ash: apatite: lime: cow dung is 6:2:1:1 mass ratio of the composite material; different lower case letters indicate that there is a significant difference between treatments, and the same lower case letters indicate that there is no significant difference between treatments. The same applies below.

TABLE 2 influence of different passivating materials on the available Cu content of the contaminated soil

TABLE 3 influence of different passivating materials on the available Cd content of the contaminated soil

EXAMPLE 2 preparation of passivation Material

1. Passivation material: the composite material is prepared from biomass power plant ash, lime, apatite and organic fertilizer without adding any adhesive, wherein the mass percent of each material is as follows: 60% of biomass power plant ash, 20% of lime, 10% of apatite and 10% of organic fertilizer, wherein the pH value is 10-13, and the particle size is less than or equal to 3 mm.

2. The preparation of the repair material comprises the following steps:

(1) drying raw materials: drying the raw materials of each component until the water content of the raw materials does not exceed 1 wt.% so as to keep the inherent activity of the raw materials of each component;

(2) sieving: all materials are respectively sieved by a 60-mesh sieve so as to be uniformly mixed;

(3) preparing materials: weighing the materials according to the mass ratio, placing the materials in a stirrer, and stirring for 2-3 min to mix uniformly;

(4) and (3) granulation: a centrifugal granulator and a rounding machine are utilized, the temperature is controlled to be 50-60 ℃, the rotating speed is controlled to be 20r/min, the water content is controlled to be 40%, and the spherical shape with the particle size being less than or equal to 3mm is formed;

(5) and (3) drying: and after granulation, drying at the temperature of 70-150 ℃ until the water content is less than or equal to 10%, and then bagging and sealing for storage.

Example 3 soil moisture control experiment

0.8g of passivation material with the grain diameter less than or equal to 3mm is evenly mixed with 200g of polluted farmland soil, and the soil humidity is controlled. Soil moisture set 5 treatment levels: the soil moisture accounts for 20%, 40%, 60%, 80% and 100% of the maximum field water capacity, and the culture is carried out for 7 days at constant temperature and humidity. The soil pH, the content of available Cu and Cd were then determined, see table 4.

The result shows that the passivation material obviously improves the pH value of the soil and effectively passivates heavy metals Cd and Cu in the soil. Soil moisture of 40%, 60% and 80% treated soil pH was significantly higher than 20% and 100% treated; the effective Cd and Cu contents are obviously reduced by treating the soil with the humidity of 40%, 60% and 80%, and the reduction range is obviously larger than that of treating the soil with 20% and 100%; the differences between the pH value of the soil treated by the soil humidity of 40%, 60% and 80% and the contents of Cu and Cd in the effective state are not obvious. In addition, the water content of the soil suitable for plant growth in dry land is 40-60%. Therefore, the soil humidity is controlled to be 40-60%, the pH value of the soil can be obviously increased, heavy metals can be effectively passivated, and the method is suitable for the growth of dry land plants.

TABLE 4 Effect of moisture control on soil pH, available Cu and Cd content

Note: different lower case letters indicate that there is a significant difference between treatments, and the same lower case letters indicate that there is no significant difference between treatments.

Example 4 passivation Material equilibration time experiment

0.4g of passivation material with the grain diameter less than or equal to 3mm and 200g of contaminated farmland soil are uniformly mixed and put into a flowerpot (10cm multiplied by 10m), and the farmland soil without the passivation material is used as a Control (CK). The passivation material equilibration times were set at 0, 3, 7 days, two plants were grown for 6 treatments, 3 replicates each. Then, the corn and the water spinach are respectively sown in the flowerpot. Thinning the plants after the plants are exposed on the soil surface for 5 days, and reserving 3 seedlings in each flowerpot. Samples were taken on day 70 of sowing and the soil pH, active Cd and Cu content and swamp cabbage and corn biomass were determined, see table 5.

TABLE 5 Effect of equilibration time on soil pH, available Cd and Cu content and plant growth

The results show that the passivation material can significantly increase the soil pH and reduce the contents of Cd and Cu in the active state, and the balance time has no influence on the stabilization of heavy metals by the passivation material and the increase of the soil pH (Table 5). The control treated corn and water spinach can germinate and expose on the ground, but cannot grow and die slowly. The passivation material promoted swamp growth and biomass accumulation, while treatments at equilibrium for 0 and 3 days were significantly greater than those at equilibrium for 7 days (table 5). The plant height and biomass of maize planted at the passivation

material equilibrium days

0, 3 and 7 were significantly greater than the control, with a trend of increasing and then decreasing (table 5). Therefore, plants can be planted on the ridges immediately after the passivating material is applied, but the planting or sowing of the plants is preferably completed within 0-3 days of soil balance.

Example 5 cultivation mode experiment

The number of the cultivation modes is set to 4, including contrast treatment without applying the passivation material, and the cultivation modes applying the passivation material are divided into broadcasting flat planting, broadcasting ridge planting and ridge planting. The amount of passivating material applied is 0.4% of the soil percentage, i.e. per 667m²600kg of the passivation material was applied to the acid soil. Plants were planted on days 0-3 of the application of the passivation material. The spreading and leveling process comprises land preparation, spreading passivator, plowing, stirring, leveling and planting; the process of spreading the ridge culture comprises the steps of land preparation, spreading the passivation material, plowing, stirring, ridging and ridge planting; the ridge applying and ridge planting process comprises soil preparation, turning, ridging, ridge applying of passivation materials and ridge planting. The ridge width is multiplied by the ridge height and the ridge spacing is 40cm multiplied by 30cm multiplied by 40cm, and the planting density is multiplied by the row spacing is 60cm multiplied by 80 cm. And measuring the plant height, tillering number and biomass of the Jujun grass after 6 months of planting, the pH of soil and the contents of Cd and Cu in the effective state.

The result shows that compared with the control, the passivation material obviously promotes the growth of the pennisetum sinese roxb and the biomass accumulation, and obviously reduces the content of Cd and Cu in the effective state of the soil. The differences of the plant height, tillering number and Cd and Cu contents in soil effective states of the Jujun grass treated by different cultivation methods are not obvious; the soil pH for the broadcast ridge treatment was minimal but not significantly different from the broadcast crop levelness (table 6). However, compared with ridge culture, the phenomenon of lodging of the pennisetum hydridum is obvious in the flat culture. In conclusion, the passivation material can effectively passivate heavy metals Cd and Cu, and although the cultivation mode has no influence on the growth and biomass of the Jujun grass, the sowing and ridge planting is better for preventing the later-stage Jujun grass from lodging and saving labor force.

TABLE 6 Effect of different cultivation methods on soil pH, effective Cd and Cu content and Megaku growth

Example 6 passivation material application dose experiment

Applying a passivation material DLSO with the particle size of less than or equal to 3mm into a heavy metal polluted farmland community with the area of 3 multiplied by 5m². Setting passivation material accounting for 0%, 0.1%, 0.2%, 0.4%, 0.6% and 0.8% of the surface layer 17cm soil mass for 6 treatments, each treatment having 3 repeated subdistricts. Then, the pennisetum hydridum is sown in ridge culture and planted, after the pennisetum hydridum grows for 6 months, a sample is taken, and the height, tillering number and biomass of the pennisetum hydridum, the pH of soil and the contents of Cu and Cd in an effective state are measured and shown in a table 7.

The results show that the passivating materials with different dosages can obviously improve the pH value of the soil, reduce the content of Cu and Cd in the effective state of the soil, and increase the plant height, tillering number and biomass accumulation of the Jujun grass. The contents of Cd and Cu in the effective state of the soil treated by the application amounts of 0.6% and 0.8% are both obviously greater than those treated by 0.1%, but the difference between the treatment amounts of 0.6% and 0.8% is not obvious; the tillering number and biomass of the treated pennisetum sinese which is more than or equal to 0.2 percent of the consumption of the passivation material are both obviously more than 0.1 percent of the consumption of the passivation material, the plant heights and tillering numbers which are 0.4 percent and 0.6 percent of the consumption are both obviously more than 0.2 percent of the consumption, but the differences of the plant heights, tillering numbers and biomass which are 0.6 percent and 0.8 percent of the consumption are not obvious (Table 7). Therefore, the application amount of the passivation material is 0.2-0.6%, so that the pH of the polluted soil can be effectively increased, the Cd and Cu in the soil can be passivated, and the growth of plants and the accumulation of biomass can be promoted.

TABLE 7 Effect of different dosages of passivating materials on soil pH, effective Cd and Cu content and Megazobium giganteum growth

Example 7 in situ repair test of different passivation materials

DLS (D: L: S mass ratio 6:1:1) and DLSO (D: L: S: O mass ratio 6:2:1:1) passivation materials with the particle size of less than or equal to 3mm and lime are uniformly mixed with heavy metal contaminated soil according to the proportion of 0.2 wt%, a cell without the passivation materials is used as a Control (CK), 4 treatments are carried out totally, each treatment is carried out on 3 repeated cells, and the area of each cell is 3 multiplied by 5m². The giant fungus grass is planted by adopting a broadcast ridge planting cultivation mode. After the planted megaterium japonicum grows for 6 months, a sample is taken, the height, the tillering number and the biomass of the megaterium japonicum are measured, the pH value of soil, the contents of Cd and Cu in an effective state and the contents of Cd and Cu in different chemical forms are measured, and the measurement results are shown in figures 1, 2, 3 and 4.

The results show that the passivation materials DLS, DLSO and lime can obviously increase the pH value of soil, the growth and the tillering number of the Jujun grass and obviously reduce the contents of Cd and Cu in the effective states of the soil (figures 1 and 2). Different passivation materials obviously reduce the content of exchangeable Cd and Cu in soil, the content of Cd and Cu in a carbonate combined state, a ferro-manganese oxide combined state and an organic combined state is obviously increased, the content of Cd and Cu in a residue state is not obviously changed, and the content difference of Cd and Cu in different chemical forms of the soil treated by the three passivation materials is not obvious (figures 3 and 4). However, a great deal of research proves that the application of lime in a large amount or for a long time can not only cause soil hardening but also strengthen the soil re-acidification degree, and can also cause imbalance of 3 elements of calcium, potassium and magnesium in the soil. On the contrary, the DLSO material is rich in organic matters, phosphorus, calcium and silicon, the mass percentage of the released main nutrients is 14 percent of the organic matters, and the P content is 14 percent of the organic matters₂O₅ 4％，CaO 7％，SiO₂13 percent, can make up the problems of lack of organic matters in acid soil, less contents of effective calcium and magnesium and the like, and promote the growth of plants and ecological restoration. The passivation material DLS can only supplement DLSOIs filled with soil nutrient elements of phosphorus and silicon, because the mass percentage of the main nutrient released by DLS is P₂O₅7% and SiO₂19 percent. From the economic benefit, the cost of DLSO is 246 yuan/ton, which is 170 yuan/ton higher than that of DLS serving as passivation material, but is only half of the cost of lime. In terms of environmental benefits, DLSO makes full use of industrial and agricultural and livestock wastes, reduces ecological environment damage caused by the mining and exploiting processes of natural minerals, and promotes plant growth and ecological restoration. In conclusion, the DLSO passivation material can effectively repair and improve typical cadmium and copper polluted soil, and integrates soil repair, improvement, economic benefit and ecological benefit.

Claims

1. The application of the passivation material combined with the agricultural measures in repairing the cadmium-copper polluted soil in south China Yangtze river is characterized in that the passivation material comprises the following components in percentage by mass: 60% of biomass power plant ash, 20% of lime, 10% of apatite and 10% of organic fertilizer, wherein the pH value is 10-13, and the particle size is less than or equal to 3 mm; contains organic matter, phosphorus, calcium and silicon, and the mass percent of the organic matter is 14 percent, and P₂O₅4%, CaO 7% and SiO₂13 percent; the organic fertilizer is fermented cow dung; the application amount of the passivation material accounts for 0.6 percent of the mass percentage of the plough layer soil within 17cm, the pH value of the cadmium-copper polluted soil is 5.56, and the volume weight is 1.31g/cm³After the passivation material is applied, plant planting or sowing is finished within 0-3 days of soil balance, the planted plants are Jujun grass, the density is plant spacing multiplied by row spacing =60 multiplied by 80cm, and the soil moisture after cultivation is controlled to be 40-60 wt% of the maximum water holding capacity in the field.