阅读说明：本技术 一种方解石钝化剂及其应用 (Calcite passivator and application thereof ) 是由 任超 任彧仲 王润涛 康弋 杜倩倩 莘丰培 王铎 李利 成旭鹏 于 2021-09-22 设计创作，主要内容包括：本发明属于钝化剂的技术领域,本发明提供了一种方解石钝化剂及其应用。本发明的方解石钝化剂包括基础组分方解石和辅助组分,所述辅助组分包括熟石灰、沸石粉和生物炭中的一种或几种；所述方解石在方解石钝化剂中的质量占比为7/9～11/12。本发明提供的方解石钝化剂均能显著降低土壤中DTPA浸提态和离子交换态Cd和Pb含量,且可有效抑制土壤中Cd和Pb的生物活性和迁移性。本发明采用的“方解石基组配钝化剂+低积累玉米品种”协同修复模式具有高效、稳定和经济的优点,对中碱性土壤重金属污染农田修复“北方模式”的建立具有重要意义。(The invention belongs to the technical field of passivators, and provides a calcite passivator and application thereof. The calcite passivator comprises a basic component calcite and an auxiliary component, wherein the auxiliary component comprises one or more of hydrated lime, zeolite powder and biochar; the mass ratio of the calcite in the calcite passivator is 7/9-11/12. The calcite passivator provided by the invention can obviously reduce the contents of Cd and Pb in a DTPA leaching state and an ion exchange state in soil, and can effectively inhibit the biological activity and the mobility of Cd and Pb in soil. The 'calcite-based combined passivator + low-accumulation corn variety' collaborative restoration mode adopted by the invention has the advantages of high efficiency, stability and economy, and has important significance for establishing a 'north mode' for restoring heavy metal contaminated farmland in medium-alkali soil.)

1. The calcite passivator is characterized by comprising a basic component calcite and an auxiliary component, wherein the auxiliary component comprises one or more of hydrated lime, zeolite powder and biochar; the mass ratio of the calcite in the calcite passivator is 7/9-11/12.

2. The calcite passivator according to claim 1, wherein the particle size of the calcite and the particle size of the slaked lime are 0.04-0.05 mm independently, and the particle size of the zeolite powder and the biochar are 0.07-0.08 mm independently.

3. The calcite passivator according to claim 1 or 2, wherein when the auxiliary component is hydrated lime, the mass ratio of calcite to hydrated lime is 9-11: 1;

when the auxiliary component is zeolite powder, the mass ratio of calcite to zeolite powder is 9-11: 1;

when the auxiliary component is biochar, the mass ratio of calcite to biochar is 9-11: 1;

when the auxiliary component is a mixture of hydrated lime, zeolite powder and charcoal, the mass ratio of calcite to the hydrated lime, the zeolite powder and the charcoal is 28-32: 1-3: 1-2.

4. The application of the calcite passivator as defined in any one of claims 1 to 3 in repairing cadmium-lead composite polluted farmland soil in combination with cadmium-lead composite low-accumulation crops.

5. The application of the calcite passivator as defined in any of claims 1-3 to the improvement of cadmium-lead composite low-accumulation crop yield.

6. The application of the calcite passivator as defined in any one of claims 1-3 in reducing absorption of cadmium and lead by cadmium-lead composite low-accumulation crops.

7. The use of any one of claims 4 to 6, wherein the cadmium-lead composite low accumulation crop comprises maize.

8. The use according to any one of claims 4 to 6, wherein the calcite passivating agent is applied in an amount of 0.7 to 0.9% of the mass of the layer.

Technical Field

The invention relates to the technical field of passivators, and particularly relates to a calcite passivator and application thereof.

Background

At present, the soil pollution situation of cultivated land in China is totally unpopular, local problems are prominent, and especially heavy metal pollution and the like seriously threaten the quality of agricultural products in partial regions. In recent years, the research on the single technologies of lime regulation, variety adjustment, foliage regulation, optimized fertilization, water regulation, in-situ passivation, microbial remediation, plant extraction and the like in the heavy metal polluted farmland is more, and the research reports of comprehensive treatment technologies are less. Due to the complex and variable field environmental factors and the complexity of soil pollution, the single measure is often difficult to ensure that the content of pollutants at the edible parts of crops reaches the standard, the physical-chemical-biological combined technical measure is integrated and optimized, and the establishment of a farmland safe utilization mode suitable for the local actual situation becomes one of the important subjects of safe utilization, treatment and restoration of the light and medium polluted cultivated land.

At present, the 'VIP + n' comprehensive treatment technology is relatively mature, and cadmium reduction products or technologies (n) such as a soil conditioner, a passivator, a leaf surface regulator, an organic fertilizer and the like are additionally applied (adopted) on the basis of adjusting the soil acidity (P) by a low-cadmium rice variety (V), flooding irrigation (I) and applying lime and the like. The technology overcomes the defects that the single treatment technology has low treatment efficiency in the treatment of the polluted farmland and can influence the normal crop planting and the grain production, has better application prospect, is mainly suitable for the south acidic Cd-polluted rice field, and has not been established in a north mode aiming at the remediation of the alkaline soil heavy metal-polluted farmland.

Calcite is carbonate mineral, has stable structure and single component, has the purity of 99 percent, can not introduce impurity ions when applied to soil, realizes stable passivation mainly through surface adsorption, dissolution precipitation and isomorphous substance substitution, has small influence on the pH value of the soil, and has obvious advantages when used as a main material of a composition. Hydrated lime is an alkaline substance, the activity of heavy metals is reduced by mainly increasing the pH value of soil and increasing negative charges on the surface of colloid to form insoluble precipitates, the passivation effect is rapid and obvious, but the lime has the defect of short persistence, the pH value of the soil is increased too high due to the large or long-term application of lime, the adverse effect is brought to the soil structure and the nutrient condition, and the hydrated lime is preferably added in a small amount under the conditions of neutral and alkaline soil in the north. The zeolite is an alkaline porous silicate mineral, has large specific surface area and pores and large cation exchange capacity, has certain water and fertilizer retention effects on soil, inhibits the migration of heavy metals in the soil and reduces the effectiveness through the effects of ion exchange, complex adsorption, alkalization precipitation and the like, but the specific adsorption sites are easy to adsorb and exchange and have the phenomenon of unstable passivation. The biochar directly adsorbs and fixes heavy metals in soil through action mechanisms such as electrostatic adsorption, ion exchange, functional group complexation and precipitation, and the like, and can indirectly influence the physical and chemical properties (pH, OM, Eh and the like) of the soil, so that the form of the heavy metals in the soil is influenced. At present, the field test research on the passivating agent prepared by combining calcite, hydrated lime, zeolite powder and charcoal has not been reported at home and abroad.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a calcite passivator and application thereof.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a calcite passivator which comprises a basic component calcite and an auxiliary component, wherein the auxiliary component comprises one or more of hydrated lime, zeolite powder and biochar; the mass ratio of the calcite in the calcite passivator is 7/9-11/12.

Preferably, the particle sizes of the calcite and the hydrated lime are 0.04-0.05 mm independently, and the particle sizes of the zeolite powder and the biochar are 0.07-0.08 mm independently.

Preferably, when the auxiliary component is hydrated lime, the mass ratio of calcite to hydrated lime is 9-11: 1;

when the auxiliary component is zeolite powder, the mass ratio of calcite to zeolite powder is 9-11: 1;

when the auxiliary component is biochar, the mass ratio of calcite to biochar is 9-11: 1;

when the auxiliary component is a mixture of hydrated lime, zeolite powder and charcoal, the mass ratio of calcite to the hydrated lime, the zeolite powder and the charcoal is 28-32: 1-3: 1-2.

The invention also provides application of the calcite passivator and the cadmium-lead composite low-accumulation crops in repairing cadmium-lead composite polluted farmland soil.

The invention also provides application of the calcite passivator in improving the yield of cadmium-lead composite low-accumulation crops.

The invention also provides application of the calcite passivator in reducing absorption of cadmium and lead by cadmium-lead composite low-accumulation crops.

Preferably, the cadmium-lead composite low-accumulation crop comprises corn.

Preferably, the application amount of the calcite passivator is 0.7-0.9% of the mass of the plough layer.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, calcite which is stable in passivation effect and has small influence on the pH value of weakly alkaline soil is taken as a main passivation material, and a small amount of hydrated lime, zeolite and biochar are compounded to form different calcite-based passivators, so that the interaction among the passivation materials is fully exerted. Experiments show that the calcite passivator provided by the invention can obviously reduce the content of Cd and Pb in a DTPA leaching state and an ion exchange state in soil, and can effectively inhibit the bioactivity and the mobility of Cd and Pb in soil. The 'calcite-based combined passivator + low-accumulation corn variety' collaborative restoration mode adopted by the invention has the advantages of high efficiency, stability and economy, and has important significance for establishing a 'north mode' for restoring heavy metal contaminated farmland in medium-alkali soil.

Drawings

Figure 1 is calcite XRD diffraction results;

FIG. 2 shows XRD diffraction results of zeolite;

FIG. 3 is a graph showing the effect of different treatment groups on thousand kernel weight of corn (note: different lower case letters indicate significant differences between treatments (P < 0.05), the same applies below);

FIG. 4 is a graph of the effect of different treatment groups on corn yield;

FIG. 5 is a graph showing the effect of different treatment groups on the content of Cd in the soil in a DTPA leaching state;

FIG. 6 is a graph showing the effect of different treatment groups on the leached Pb content of DTPA in soil;

FIG. 7 is a graph showing the effect of different treatment groups on the content of Cd in the soil in an ion-exchange state;

FIG. 8 is a graph of the effect of different treatment groups on the ion-exchanged Pb content of the soil;

FIG. 9 is a graph showing the effect of different treatment groups on the Cd content in corn stems and leaves;

FIG. 10 is a graph of the effect of different treatment groups on the Pb content of maize stems and leaves;

FIG. 11 is a graph of the effect of different treatment groups on the Cd content of corn kernels;

FIG. 12 is a graph of the effect of different treatment groups on the Pb content of corn kernels;

FIG. 13 is a correlation coefficient between the Cd content of corn stems and leaves and the content of 2 extraction states in soil;

FIG. 14 is a correlation coefficient of the Pb content of corn stems and leaves and the content of 2 extraction states in soil;

FIG. 15 is a correlation coefficient of the Cd content of corn grains and the content of 2 extraction states in soil;

FIG. 16 is a correlation coefficient of Pb content of corn kernels and content of 2 extraction states in soil.

Detailed Description

The invention provides a calcite passivator which comprises a basic component calcite and an auxiliary component, wherein the auxiliary component comprises one or more of hydrated lime, zeolite powder and biochar; the mass ratio of the calcite in the calcite passivator is 7/9-11/12.

In the invention, the mass ratio of the calcite in the calcite passivator is 7/9-11/12, and more preferably 6/7.

In the invention, the particle sizes of the calcite and the hydrated lime are preferably 0.04-0.05 mm independently, more preferably 0.048mm independently, and the particle sizes of the zeolite powder and the biochar are preferably 0.07-0.08 mm independently, more preferably 0.075 mm.

In the invention, when the auxiliary component is hydrated lime, the mass ratio of calcite to hydrated lime is preferably 9-11: 1, and more preferably 10: 1;

when the auxiliary component is zeolite powder, the mass ratio of calcite to zeolite powder is preferably 9-11: 1, and more preferably 10: 1;

when the auxiliary component is biochar, the mass ratio of calcite to biochar is preferably 9-11: 1, and more preferably 10: 1;

when the auxiliary component is a mixture of hydrated lime, zeolite powder and charcoal, the mass ratio of calcite to the hydrated lime, zeolite powder and charcoal is preferably 28-32: 1-3: 1-2, and more preferably 30:2:2: 1.

The calcite passivator provided by the invention is prepared by preferably mixing calcite and one or more of hydrated lime, zeolite powder and biochar according to a mass ratio by using a stirrer.

The invention also provides application of the calcite passivator and the cadmium-lead composite low-accumulation crops in repairing cadmium-lead composite polluted farmland soil, wherein the combination refers to the application of the calcite passivator in the cadmium-lead composite low-accumulation crops in the field.

The invention also provides application of the calcite passivator in improving the yield of cadmium-lead composite low-accumulation crops.

The invention also provides application of the calcite passivator in reducing absorption of cadmium and lead by cadmium-lead composite low-accumulation crops.

In the present invention, the cadmium-lead composite low-accumulation crop preferably comprises corn.

In the invention, the application amount of the calcite passivator is preferably 0.7-0.9% of the mass of the plough layer, and more preferably 0.8%.

The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.

The test fields of the following examples are located in SBG-17 polluted farmland of stone valley in Koelken, Luoyang, Henan province, and are divided into 4 test areas, and each test area collects 0-20 cm mixed soil samples according to a quincunx five-point method, wherein the soil samples are brown soil and sandy loam soil. As the invention is a field test condition, the physicochemical properties of the soil and the pollution degree of Cd and Pb are different between the areas T1-T4, and the physicochemical properties of the soil to be tested and the heavy metal content in each test area are shown in Table 1.

TABLE 1 physicochemical Properties and heavy Metal contents of soil tested in each test area

Note: pH is dimensionless, CEC is in cmol kg^-1OM, N, K and P in g.kg^-1The unit of alkaline hydrolysis nitrogen, available phosphorus, quick-acting potassium, full Cd, full Pb, available cadmium and available lead is mg.kg^-1

The passivator materials tested in the following examples were calcite, slaked lime, zeolite and biochar. Wherein the calcite is purchased from Yuxing century mining industry development Limited liability company in south-south City of Henan province, has a particle size of 0.048mm and a price of 220 Yuan.t^-1(ii) a The slaked lime is purchased from Daxin environmental protection science and technology Limited company in Xinxiang city of Henan province, with particle size of 0.048mm and price of 800 Yuan.t^-1(ii) a Zeolite is purchased from Jun Chuang perlite factory in Xinyang city, Henan province, with particle size of 0.075mm and price of 385 Yuan.t^-1(ii) a The biochar is purchased from Hubei Jinri ecological energy resources Co Ltd, has the granularity of 0.075mm and the price of 2200 Yuan t^-1. The heavy metal content of the passivates tested is shown in table 2, and the X-ray diffraction results for calcite and zeolite are shown in figures 1 and 2.

TABLE 2 passivating agent for test heavy metal content/mg-kg^-1

The cadmium-lead composite low-accumulation crop in the following examples is corn, and the specific variety is firstly corn 335.

Example 1

Uniformly mixing calcite and hydrated lime according to the mass ratio of 10:1 by adopting a stirrer, bagging to obtain a calcite passivator, and then applying the calcite passivator to the soil surface of a corn field according to the application amount of 1650kg per mu.

Example 2

Uniformly mixing calcite and zeolite powder according to the mass ratio of 10:1 by using a stirrer, bagging to obtain a calcite passivator, and then spraying the calcite passivator on the soil surface of a corn field according to the application amount of 1650kg per mu.

Example 3

Uniformly mixing calcite and biochar according to a mass ratio of 10:1 by using a stirrer, bagging to obtain a calcite passivator, and then applying the calcite passivator to the soil surface of a corn field according to the application amount of 1650kg per mu.

Example 4

Uniformly mixing calcite, hydrated lime, zeolite powder and charcoal according to a mass ratio of 30:2:2:1 by using a stirrer, bagging to obtain a calcite passivator, and then applying the calcite passivator to the soil surface of a corn field according to an application amount of 1750kg per mu.

The test field is divided into 4 test areas which are respectively T1, T2, T3 and T4, each test area is provided with 1 passivant treatment (comparative example) and 1 group of passivant treatments (3 times of repetition), the total number of the test areas is 16, and the adjacent test areas are separated by a ridge of 1.2 m. The 4 passivator treatments were: calcite + hydrated lime (example 1), calcite + zeolite powder (example 2), calcite + biochar (example 3) and calcite + hydrated lime + zeolite powder + biochar (example 4), wherein the compounded passivator is added in an application amount of 0.8% (mass percentage of soil plough layer accounting for 0-20 cm of soil), and the specific settings of each group are shown in table 3. The compounded passivator is uniformly mixed by a stirrer and then packaged, is transported to the field and then uniformly spread on the soil surface of each test unit, and is simultaneously applied with commercial organic fertilizer (made of sheep manure) 375 t.km^-2(250 kg. mu.m)^-1) And ploughing by using rotary tillage equipment for more than 3 times, and fully and uniformly mixing the passivation material with 0-20 cm plough layer soil. Planting corn variety Yu 335, applying 75 t.km before sowing^-2(50 kg. mu.m)^-1) Diammonium phosphate is used as base fertilizer, the row spacing of sowing is 40cm, the plant spacing is 30cm, and additional application is carried out for 45 t.km in large-horn-mouth period^-2(30 kg. mu.m)^-1) Diammonium phosphate and 30 t.km^-2(20 kg. mu.m)^-1) Urea. The field management of each test plot is consistent with the planting habit of local farmers.

TABLE 3 different treatment group settings

Collecting and processing samples:

and cooperatively collecting a soil sample and a mature corn plant sample in 10 months in 2020. And (3) respectively collecting 1 group of surface layer (0-20 cm) mixed soil samples by each test unit according to a plum blossom 5-point method, and totaling 16 groups of soil samples. The soil sample is naturally dried, coarsely ground (through a 2mm nylon sieve) and finely ground (through 1mm and 0.15mm nylon sieves) for later use. Each test unit is used for cooperatively collecting 1 group of corn stems and leaves and seeds, 16 groups of corn stem and leaf samples and 16 groups of corn seed samples. And washing a corn plant sample by using deionized water, naturally airing, grinding to a size of 0.25-0.4 mm by using a nylon sieve, and uniformly mixing for later use.

Measurement items and methods:

basic physicochemical properties of soil: the pH value adopts a glass electrode method, the mechanical composition adopts a densitometer method, the organic matter adopts a potassium dichromate volumetric method, the cation exchange amount adopts an ammonium chloride-ammonium acetate exchange method, the total nitrogen adopts a Kjeldahl method, the total phosphorus and the total potassium adopt a tetraacid digestion-inductively coupled plasma emission spectrometry (ICP-OES), the alkaline hydrolysis nitrogen adopts an alkaline hydrolysis-diffusion method, the effective phosphorus adopts a sodium bicarbonate digestion-inductively coupled plasma emission spectrometry, and the quick-acting potassium adopts an ammonium acetate digestion-inductively coupled plasma emission spectrometry. The method is characterized in that the content of all cadmium and all lead in the soil is determined by an inductively coupled plasma mass spectrometry (ICP-MS), the content of effective states of Cd and Pb in the soil is determined by a diethylenetriaminepentaacetic acid (DTPA) leaching-inductively coupled plasma emission spectrometry, the content of exchange states of Cd and Pb is determined by a Tessier correction sequence seven-step extraction-inductively coupled plasma mass spectrometry, and the mineral component in the passivator is determined by an XRD diffractometer (X, PertPro).

Data statistical analysis:

the test detection data adopts Excel 2019, Origin 2018 and SPSS 26 analysis software to carry out data sorting, statistical analysis and drawing analysis on the treatment effect of different passivators.

The reduction rate (K) is adopted to judge the stabilizing effect of the passivation material on the heavy metal, and the enrichment coefficient (BCF) is adopted to judge the accumulation degree of the crop on the heavy metal.

Reduction ratio K (%) ═ 1-C_e/C_i

In the formula, C_eThe content of a certain metal element in an extraction state after the polluted soil is passivated and balanced; c_iThe content of a certain metal element in an extraction state before the polluted soil is passivated.

Enrichment factor BCF ═ C_plant/C_soil

In the formula, C_plantThe content of a certain metal element in a certain part of a plant; c_soilIs a metal elementContent of elements in plant soil.

Experimental example 1

The effect of different treatment groups on thousand kernel weight and yield of corn was studied and the results are shown in fig. 3 and 4.

As can be seen from FIGS. 3 and 4, the thousand kernel weights of the corn of the control example (i.e., control group, the same below) and the corn of the example (i.e., test group, the same below) in the T1 zone were 372g and 372g, respectively, and the yield was 730 kg/mu, respectively^-1784 kg/mu^-1(ii) a The thousand kernel weight of corn in the control example and the example in the T2 area is 366g and 377g respectively, and the yield is 693 kg/mu respectively^-1And 750kg per mu^-1(ii) a The thousand kernel weights of the corn in the control example and the example in the T3 area are 377g and 382g respectively, and the yield is 776 kg-mu respectively^-1And 815kg per mu^-1(ii) a The thousand kernel weights of the corn of the control example and the example in the T4 area are 348g and 362g respectively, and the yield is 714 kg-mu^-1And 728kg per mu^-1. Therefore, the thousand seed weight and the yield per mu of corn can be improved by different calcite-based passivator treatments in the embodiments 1 to 4 of the invention compared with the comparative examples 1 to 4.

Experimental example 2

The effect of different treatment groups on the physicochemical properties of the soil was studied and the results are shown in table 4.

As can be seen from Table 4, the treatment of the different examples has a certain effect of raising the pH of the soil compared with the control example, and the pH of the zones T1-T4 is raised by 0.46, 0.25, 0.12 and 0.13 units respectively. The different example treatments sequence the soil pH rise as: example 1 > example 2 > example 4 ≈ example 3. Sequencing the lifting amplitude of the single passivator to the pH value of the soil according to the early pilot plant stage as follows: slaked lime > zeolite > biochar > calcite, the influence of the whole compounded passivator of the embodiment 1-4 on the pH value of soil is small, and the lifting amplitude is lower than 0.5 unit. The slight difference of the calcite-based combined passivator of the examples 1-4 in the soil pH increase amplitude mainly depends on the influence of the compound materials of hydrated lime, zeolite and biochar on the soil pH value. The treatment of different calcite-based passivators has no obvious rule with the influence of the contents of field soil organic matters, total nitrogen, total phosphorus, total potassium, alkaline hydrolysis nitrogen, available phosphorus and available potassium, and has no statistical significance and no obvious correlation (P is more than 0.05) compared with a control group. This indicates that the calcite-based compounded passivator does not affect the soil fertility index, which corresponds to the results of no significant change in corn yield in different treatment test areas.

TABLE 4 variation of pH and fertility indices of soils of different treatment groups

Experimental example 3

The influence of different treatment groups on the Cd and Pb contents in the leaching state of DTPA in soil is researched, and the results are shown in FIGS. 5 and 6.

As can be seen from FIGS. 5 and 6, the contents of the soils ω (effective state Cd) in the control examples and examples in the zones T1 to T4 were 0.318 to 0.835 mg-kg^-1And 0.284 to 0.423 mg/kg^-1The reduction rates of heavy metal Cd in soil treated by different embodiments are sequenced as follows: example 4 (49.36%) > example 1 (38.25%) > example 3 (14.44%) > example 2 (10.69%). The soil omega (available Pb) of the control examples and the examples in the T1-T4 regions is 30.05-144.50 mg/kg^-1And 20.26 to 39.66 mg/kg^-1The sequences of the reduction rates of heavy metal Pb in the soil treated by different examples are as follows: example 4 (72.55%) > example 1 (38.65%) > example 3 (25.84%) > example 2 (22.87%). Therefore, the calcite passivator disclosed by the invention shows high-efficiency passivation efficiency under field test conditions.

Experimental example 4

The influence of different treatment groups on the content of Cd and Pb in the soil in the ion exchange state is studied, and the results are shown in FIGS. 7 and 8.

As can be seen from FIGS. 7 and 8, the concentrations of soil ω (ion-exchanged Cd) in the control examples and examples in the zones T1 to T4 were 0.164 to 0.536 mg/kg^-1And 0.161-0.253 mg/kg^-1The reduction rates of heavy metal Cd in soil treated by different embodiments are sequenced as follows: example 4 (55.39%) > example 1 (36.61%) > example 3 (12.33%) > example 2 (2.16%). The contents of the soils omega (ion-exchanged Pb) in the control examples and examples in the T1-T4 regions were 0.090-0.506 mg-kg^-1And 0.056 to 0.109 mg/kg^-1Is not limited toThe sequences of the reduction rates of heavy metal Pb in the soil treated by the same example are as follows: example 4 (78.52%) > example 1 (37.28%) > example 2 (26.52%) ≈ example 3 (26.01%). Therefore, the calcite passivator disclosed by the invention shows high-efficiency passivation efficiency under field test conditions.

Experimental example 5

The effect of different treatment groups on the absorption of Cd and Pb by corn stems and leaves is studied, and the results are shown in FIGS. 9 and 10.

As can be seen from FIGS. 9 and 10, the amounts of the low-accumulation corn stems and leaves omega (Cd) in the control examples and the examples in the T1-T4 regions were 0.450-0.955 mg/kg^-1And 0.385 to 0.640 mg/kg^-1The enrichment coefficients of the stem leaf Cd are 0.315-0.531 and 0.375-0.501 respectively. The low-accumulation corn stem leaf Cd content reduction rate processed by different embodiments is ranked as follows: example 4 (45.93%) > example 3 (25.99%) > example 1 (22.94%) > example 2 (14.38%). The low-accumulation corn stem and leaf omega (Pb) in the comparison examples and the examples of the T1-T4 areas is 3.194-11.010 mg/kg^-13.062-3.852 mg/kg^-1The Pb enrichment coefficients of stem leaves are 0.012-0.022 and 0.013-0.021 respectively, and the reduction rates of the Pb content of the low-accumulation corn treated by different examples are ranked as follows: example 4 (67.00%) > example 1 (22.17%) > example 3 (4.12%) > example 2 (0.56%). Therefore, the calcite passivator disclosed by the invention can effectively inhibit the biological activity and the mobility of Cd and Pb in soil, and the Cd and Pb composite low-accumulation corn variety Yu 335 shows a stable low-accumulation characteristic in a heavy metal polluted farmland.

Experimental example 6

The influence of different treatment groups on the absorption of Cd and Pb by corn kernels is researched, and the results are shown in FIGS. 11 and 12.

As can be seen from FIGS. 11 and 12, the low-accumulation corn kernels omega (Cd) in the control examples and the examples in the areas T1-T4 are 0.0099-0.0149 mg/kg^-1And 0.0087-0.0122 mg.kg^-1The enrichment coefficients of Cd in the grains are respectively 0.005-0.011 and 0.008-0.010. The method for sequencing the reduction rate of the Cd content of the low-accumulation corn grains by the treatment of different embodiments comprises the following steps: example 4 (25.17%) > example 1 (22.69%) > example 3 (18.12%) > example 2 (12.12%). Comparison examples and examples in the T1-T4 region low accumulation jadeThe omega (Pb) of the rice seeds is 0.0081-0.0414 mg-kg^-1And 0.0066 to 0.0221 mg/kg^-1The Pb enrichment coefficients of the grains are 0.00004-0.00007 and 0.00004-0.00007 respectively, and the reduction rate of the Pb content of the low-accumulation corn grains treated by different embodiments is sequenced as follows: example 4 (46.62%) > example 3 (32.53%) > example 1 (18.52%) > example 2 (0%). Therefore, the content of Cd and Pb absorbed by corn kernels is further reduced under the treatment conditions of different groups of passivators, which shows that the transfer and the transportation of heavy metals Cd and Pb in soil can be effectively reduced by the treatment of the calcite passivator.

Experimental example 7

The relationship between the Cd and Pb contents of the corn plants and the contents of 2 kinds of extraction states of soil is researched, and the results are shown in fig. 13, fig. 14, fig. 15 and fig. 16.

In order to further research the influence of the contents of Cd and Pb in various extraction states in the soil after the application of the calcite-based composite passivator on the contents of Cd and Pb in corn plants, the invention respectively carries out correlation analysis on the contents of Cd and Pb in corn stems and leaves and grains and the extraction state (DTPA) and the ion exchange state (Ex) of Cd and Pb in the soil. As can be seen from FIGS. 13 and 14, the 2 kinds of extraction state contents of Cd in the soil and the Cd content in the corn stems and leaves all show very significant positive correlation (r_DTPA-Cd＝0.768**、r_Ex-Cd0.792), the Pb content in the soil and the Pb content in the corn stem and leaf all show a very significant positive correlation (r)_DTPA-Pb＝0.922**、r_Ex-Pb0.889). As can be seen from FIGS. 15 and 16, the 2-extraction-state contents of Cd in the soil and the Cd content in the corn grains all show very significant positive correlation (r_DTPA-Cd＝0.730**、r_Ex-Cd0.751), the Pb content in the soil and the Pb content in the corn kernel all show extremely obvious positive correlation (r)_DTPA-Pb＝0.838**、r_Ex-Pb＝0.767**)。

In conclusion, under the condition that the corn variety Yu 335 is polluted soil which is not treated by the passivant, the content and enrichment coefficient of Cd and Pb in corn grains are maintained at a low level, and the stability of the variety Cd and Pb low accumulated in the field is shown. Because the heavy metal pollution degree of the field soil has certain heterogeneity and complexity due to the difference of soil environments, the contents of Cd and Pb of soil pollutants in a T4 test area are higher than those in T1-T3 test areas, the passivation efficiency of the T4 area on Cd and Pb is the maximum under the treatment of the embodiment 4, and the reduction rate of the contents of Cd and Pb absorbed by corn stems, leaves and seeds is the maximum, which indicates that the calcite-based passivation material has better passivation effect under the condition of relatively higher contents of Cd and Pb in soil. The invention preliminarily verifies that the 'calcite-based combined passivator + low-accumulation corn variety' synergistic remediation technical mode has the advantages of high efficiency, stability and economy, and has a certain reference value for establishing a 'northern mode' for remediation of heavy metal contaminated farmland in medium-alkaline soil.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.