CN113477702A

CN113477702A - Method for extracting heavy metal cadmium in soil

Info

Publication number: CN113477702A
Application number: CN202110631440.7A
Authority: CN
Inventors: 陈金峰; 邹春萍
Original assignee: Environmental Horticulture Institute of Guangdong Academy of Agricultural Sciences
Current assignee: Environmental Horticulture Institute of Guangdong Academy of Agricultural Sciences
Priority date: 2021-06-07
Filing date: 2021-06-07
Publication date: 2021-10-08

Abstract

The invention discloses a method for extracting heavy metal cadmium from soil, which comprises the following steps: 1) applying bociclib as a base fertilizer in soil, and planting vetiver grass seedlings after 2 weeks; 2) planting vetiver grass for 50-70 days, and spraying benomyl; 3) after the benomyl is sprayed for 20-40 days, topdressing with bocasi; 4) spraying a heavy metal bioavailability reinforcing agent after topdressing for 10-20 days; 5) spraying benomyl for the second time 10-20 days after spraying the heavy metal bioavailability reinforcing agent; 6) spraying a heavy metal bioavailability reinforcing agent again after spraying benomyl for 10-20 days for the second time; and 7) spraying the heavy metal bioavailability reinforcing agent again for 40-60 days, and harvesting the vetiver to obtain the vetiver. The method can improve the absorption, transportation and enrichment efficiency of the vetiver grass on the heavy metal cadmium in the soil, thereby improving the remediation efficiency of the vetiver grass on the heavy metal polluted soil to a greater extent.

Description

Method for extracting heavy metal cadmium in soil

Technical Field

The invention relates to the technical field of heavy metal extraction, in particular to a method for extracting heavy metal cadmium (Cd) in soil and application thereof in repairing soil polluted by the heavy metal cadmium.

Background

Along with the rapid development of social economy in China, the diffusion, sedimentation and accumulation of waste residues and waste gases containing heavy metals generated in the industrial and mining industry and the irrigation of agriculture and forestry by the waste water containing heavy metalsThe heavy metal pollution of soil in China is caused by the large use of the field and heavy metal containing pesticide and phosphate fertilizer. Song Wei et al^【1】According to measurement, the probability of heavy metal pollution of soil in cultivated land of China is 16.67%, and the cultivated land occupies 1/6% of the total area of cultivated land of China. The soil heavy metal pollution in south China is more prominent, and 50% of farmlands in partial cities in south China are polluted by heavy metals such As Cd, As, Hg and the like.

Remediation of heavy metal contaminated soil is a very challenging problem. The conventional physical or chemical heavy metal polluted soil treatment technology has the problems of high treatment cost, secondary release of heavy metals or secondary pollution. The phytoremediation technology can extract or stabilize heavy metals in soil through plants, has the characteristics of low cost and environmental friendliness, and is increasingly receiving wide attention at present. Some plants can be enriched with heavy metals in vivo, and the heavy metals in the soil can be permanently removed by artificial harvesting, but the method of phytoremediation generally takes a long time and is low in remediation efficiency because: 1. under the stress of heavy metals, the plant grows slowly, the biomass is small, and a large amount of heavy metals cannot be extracted in a short period; 2. the heavy metal availability of the plant rhizosphere is poor (namely, the biological effectiveness is poor), so that the heavy metal cannot be fully absorbed by the plant; 3. the efficiency of transferring heavy metals absorbed by root systems to the overground part by plants is not high; therefore, the efficiency of phytoremediation can be improved by means of promoting plant growth, enhancing the bioavailability of plant rhizosphere heavy metals and improving the transport efficiency.

Vetiver grass (Chrysopogon zizanioides) is a perennial, strong herb of the genus vetiver of the family gramineae, distributed mainly in tropical and subtropical regions. The overground part is 150-250 cm high, the stems are clustered, the leaves are linear, and the flowers are brown-purple; the root depth can reach 2-4 m. The vetiver grass has low requirements on soil, and can produce 100-200 tons of fresh grass and 40-80 tons of hay per hectare every year according to growth environment conditions (moisture and nutrition). The vetiver grass has the characteristics of large biomass, barren resistance, acid and alkali resistance, drought resistance and the like, is widely applied to the heavy metal polluted soil treatment, the restoration of damaged habitats such as abandoned fields of mines, side slopes of river channels and the like, and has good environmental treatment or restoration effect. But because: 1. the soil of the heavy metal polluted land is very poor and the environment of the land is poor, so that the vetiver grass grows badly; 2. low bioavailability of heavy metals; 3. the vetiver grass root system is infected by a large amount of cluster mycorrhiza (AMF), the AMF holds and promotes the root system to hold heavy metal, the mobility of the heavy metal is limited, and the defects that the vetiver grass grows badly and the biomass advantage is limited in practical application are caused by the AMF; and because the existence of AMF makes heavy metal concentrate in the root, restricted the transportation, the rhizosphere heavy metal availability is not big again, finally leads to the actual extraction efficiency of vetiver grass to heavy metal not high.

Reference documents:

1. song Wei, Chen Bai Ming, Liulin, soil heavy metal pollution general [ J ] of cultivated land in China, water and soil conservation research, 2013,20(2): 293-.

Disclosure of Invention

Based on the problems, the invention aims to overcome the defects of the prior art and provide the method for more efficiently extracting the heavy metal cadmium in the soil, and the method can be used for improving the repairing efficiency of the vetiver to the soil polluted by the heavy metal cadmium to a greater extent.

In order to achieve the purpose, the invention adopts the technical scheme that: a method for extracting heavy metal cadmium from soil, comprising the following steps:

1) applying bociclib as a base fertilizer in soil, and planting vetiver grass seedlings after 2 weeks;

2) spraying benomyl to the vetiver 50-70 days after the vetiver seedlings are planted;

3) after the benomyl is sprayed for 20-40 days, topdressing with bocasi;

4) after 10-20 days of topdressing, spraying a heavy metal bioavailability reinforcing agent on the vetiver grass;

5) spraying benomyl to the vetiveria zizanioides for the second time after spraying the heavy metal bioavailability reinforcing agent for 10-20 days;

6) spraying the heavy metal bioavailability reinforcing agent on the vetiver again 10-20 days after spraying the benomyl for the second time; and

7) and spraying the heavy metal biological effectiveness reinforcing agent for 40-60 days again, and then harvesting the vetiver to obtain the vetiver.

Wherein, bocasi (bokashi) is an organic fertilizer with rich nutrition, has quick fertilizer efficiency and balanced nutrition, and is very favorable for promoting the growth of crops on barren soil. The plant material for preparing bocasi has rich source, can be obtained from local materials, and saves cost. Benomyl has good inhibitory action on AMF fungi, can relieve the limitation of heavy metal transfer of plants to a certain extent, and promotes the transfer of heavy metals.

Preferably, bocacacy is applied to the soil in a broadcast fashion and then the soil is thoroughly mixed within 10cm of the surface layer.

Preferably, the 50-70 days in the step 2) can be 50, 55, 60, 65 or 70 days, and more preferably 60 days; the 20-40 days in the step 3) can be 20, 25, 30, 35 or 40 days, and more preferably 30 days; the 10-20 days in the steps 4), 5) and 6) can be 10, 12, 15, 18 or 20 days, and more preferably 15 days; the 40-60 days in the step 7) can be 40, 45, 50, 55 or 60 days, and more preferably 50 days.

As a further optimization of the scheme, the dosage of the bocacacil in the step 1) is 2g/kg of soil.

As a further optimization of the scheme, the dosage of bocacin in the step 3) is 1g/kg of soil.

As a further optimization of the scheme, the dosage of benomyl in the steps 2) and 5) is 20mg/kg of soil.

As a further optimization of the above scheme, the heavy metal bioavailability enhancer is a mixture of oxalic acid and citric acid. Preferably, the molar concentration ratio of the oxalic acid to the citric acid is 2:1 or 1: 2. more preferably, the dosage of the oxalic acid is 10-20 mM/kg of soil, and the dosage of the citric acid is 10-20 mM/kg of soil.

In some embodiments, the mole ratio of oxalic acid to citric acid is adjusted according to the occurrence of heavy metals in the soil, for example, the mole ratio of oxalic acid to citric acid is preferably 2:1 when the reducible state ratio exceeds 50%, and the mole ratio of oxalic acid to citric acid is preferably 1:2 when the reducible state ratio is less than 20%.

The oxalic acid and the citric acid are small molecular organic acids which effectively improve the bioavailability of the soil heavy metal, have the effects of dissolving and chelating the soil heavy metal and increasing the bioavailability (availability) of the soil heavy metal of a plant root system, are easy to degrade due to natural existence, have the characteristics of small influence on the soil aggregate structure and nutrition, soil environment friendliness and the like, and are promising heavy metal bioavailability enhancers.

As a further optimization of the above scheme, the rice chaff in boccasi: bean pulp: the mass ratio of the fish meal is 6:2:2 or 6:3: 1. more preferably, the boccaro rice chaff: bean pulp: the mass ratio of the fish meal is 6:2: 2.

as a further optimization of the above solution, the method comprises the steps of:

1) applying bocac in the soil as a base fertilizer in the middle ten days of 3 months, and planting vetiver grass seedlings in the beginning of 4 months;

2) spraying benomyl at the beginning of 6 months;

3) topdressing with bocasi in the beginning of 7 months;

4) in 7, in the middle of the month, a mixture of oxalic acid and citric acid is sprayed;

5) spraying benomyl for the second time at the beginning of 8 months;

6)8, spraying the mixture of the oxalic acid and the citric acid again in the middle of the month; and

7) and (5) harvesting the vetiver grass at the beginning of 10 months.

Preferably, the middle ten days of the month can be any day from 11 to 20 of the month; the beginning of the month can be any day of the month 1-10.

As another aspect of the invention, the invention also provides application of the method in repairing soil polluted by heavy metal cadmium.

In conclusion, the beneficial effects of the invention are as follows:

the invention relates to a method for jointly using organic fertilizer boccasi, oxalic acid, citric acid solubilizer and benomyl fungistat, which can improve the absorption, transportation and enrichment efficiency of vetiver to heavy metal cadmium (Cd) in soil by using substances to regulate the growth and absorption conditions of the vetiver at different stages of growth and development of the vetiver, thereby improving the remediation efficiency of the vetiver to the heavy metal polluted soil to a greater extent.

Drawings

FIG. 1 is a schematic flow chart of the method for extracting heavy metal cadmium from soil according to the invention.

Detailed Description

The invention discloses a comprehensive agronomic measure method for strengthening heavy metal cadmium polluted soil extracted from vetiver grass, which comprises the following steps of: the bocasi microbial organic fertilizer is used for improving the heavy metal polluted barren soil and promoting the growth of vetiver grass; oxalic acid and citric acid are utilized to enhance the bioavailability of vetiver rhizosphere cadmium; the benomyl is utilized to inhibit the AMF mycorrhiza infection of the root system of the vetiver, and the transport efficiency of the vetiver to Cd is improved.

In some embodiments, the method of the present invention comprises the steps of: in 3-month middle ten days, the bocac basic fertilizer is used for two weeks before the vetiver grass is fixedly planted; planting vetiver grass in the early 4 months; spraying benomyl at the beginning of 6 months; topdressing bocasi in the beginning of 7 months; in 7, in the middle of the month, mixed acid of oxalic acid and citric acid is sprayed; spraying benomyl again at the beginning of 8 months; spraying mixed acid of oxalic acid and citric acid again in 8 middle of the month; and (4) harvesting vetiver grass at the beginning of 10 months, and analyzing the growth condition and the heavy metal cadmium absorption amount of the vetiver grass. The method can promote the biomass accumulation of the vetiver grass in the heavy metal polluted soil and promote the absorption and transportation of the vetiver grass to cadmium, thereby increasing the enrichment amount of the vetiver grass to the cadmium and finally improving the repair efficiency of the vetiver grass to the heavy metal cadmium polluted soil.

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments. The materials and reagents of the present invention are commercially available unless otherwise specified. Unless otherwise specified, all reagents/substances used in the present invention are in mass units. Unless otherwise specified, the experimental procedures used in the present invention are all general/routine in the art.

1. The material and the method are as follows:

1.1 materials

The seedling of Vetiveria zizanioides is bred in a tillering propagation mode, and the specific preparation method of the seedling comprises the following steps: digging out the whole mature vetiver (with the height of 150-.

Bocasi is a microbial organic fertilizer with high nitrogen content and capable of quickly releasing nutrients, and mainly comprises the following materials: organic materials such as rice chaff, bean pulp, fish meal and the like and zymophyte agents; the manufacturing method comprises the following steps: 6 parts of rice chaff, 2-3 parts of soybean meal and 2-1 parts of fish meal (mass ratio) are fully mixed, then a zymophyte agent is added, the water content of the mixture is adjusted to 35-40%, the mixture is fermented in a closed manner at 25-35 ℃ for 2-4 weeks, and fermentation is successful when the fermented product has sweet and sour fermentation fragrance with slight wine taste. The bocasi fertilizer contains C40-50 wt%, N4-4.8 wt%, P0.8-1.2 wt% and C/N ratio 10-13. Wherein the fermentation inoculum is prepared from EM1 microbial environment modifier seed liquid (EM research institution of Kabushiki Kaisha), molasses and warm water (50 ℃), and the volume ratio is 1:1: 100; and (3) standing the prepared bacterial liquid for 2-3 days, and performing amplification culture on the bacterial liquid for bocacin fermentation.

The oxalic acid and the citric acid are commercially produced oxalic acid (the content is more than or equal to 99%) and citric acid (the content is more than or equal to 99%).

Benomyl is a wettable powder with a content of 50%.

The soil is contaminated by heavy metal Cd, and is divided into high reducible state Cd contaminated soil (the content of the combined state Cd of the iron and manganese oxides is more than or equal to 50%) and low reducible state Cd contaminated soil (the content of the combined state Cd of the iron and manganese oxides is less than or equal to 20%) according to the content of the reducible state Cd contaminated soil (also called the combined state Cd of the iron and manganese oxides, which can be reduced and dissolved by small molecular carboxylic acid such as oxalic acid, so as to release the heavy metal combined on the iron and manganese oxides and increase the bioavailability of the heavy metal in the soil).

The pH of the test soil A is 5.04, the organic matter content is 1.4%, the total nitrogen content is 0.12%, the available phosphorus content is 23.6mg/Kg, the total Cd content is 9.30mg/Kg, wherein the acetic acid content is 12%, the reducible state is 53%, the organic combination state is 14%, and the residue state is 21%, and the test soil A belongs to the highly reducible state Cd polluted soil.

Acetic acid extraction state: the heavy metal components which can be extracted from the soil by weak acid mainly comprise heavy metals in a water soluble state, an exchangeable state and a weak acid combined state, and the heavy metals have the highest biological effectiveness;

reducible state: the heavy metal components bound on the iron-manganese oxide can be released into the soil solution when the iron-manganese oxide is reduced;

organic binding state: the heavy metal component is a component which is combined with macromolecular organic matters and can be released into a soil solution when the organic matters are oxidized;

residue state: heavy metal components which are difficult to release by redox are generally difficult to dissolve and have the lowest bioavailability.

The pH of the test soil B is 5.79, the organic matter content is 1.6%, the total nitrogen content is 0.15%, the available phosphorus content is 15.4mg/kg, the total Cd content is 10.56mg/kg, wherein the content of acetic acid in an extraction state is 39%, the content of the organic binding state is 16%, the content of the organic binding state is 17%, and the content of the residue in the residue state is 28%, and the test soil B belongs to the soil polluted by low reducible Cd.

1.2 implementation method:

the method comprises the following steps of (1) using bocac fertilizer to improve soil 2 weeks before planting vetiver grass, wherein the dosage of bocac fertilizer is 200 g/square meter or 2g/kg soil (calculated by 10cm depth of a plough layer); bocacacil is applied to the soil in a broadcast manner and then the soil on the surface layer of 10cm is mixed thoroughly.

Beginning to plant vetiver seedlings 2 weeks after bocac application: seedlings of vetiver grass (stem: 15-20 cm; root: 5-10cm) are planted in plastic buckets containing 15kg of the soil A or B, and the seedlings are generally planted in the beginning of 4 months.

Each soil is treated in two ways: agronomic treatment (bocasi + benomyl + organic acid) and control treatment (no agronomic treatment except for equal watering).

Wherein the comprehensive agronomic measures of soil a are shown in table 1 below:

TABLE 1

Note: in table 1, the biomass of vetiver grass is measured by harvesting and weighing for analyzing the growth of vetiver grass, and the heavy metal absorption is measured by an atomic absorption method for analyzing the heavy metal absorption.

The general agronomic measures for soil B are shown in table 2 below:

TABLE 2

Note: in table 2, the biomass of vetiver grass is measured by harvesting and weighing for analyzing the growth of vetiver grass, and the heavy metal absorption is measured by an atomic absorption method for analyzing the heavy metal absorption.

Example 1

In 3 days of middle of the month, adding 2g/kg of base fertilizer into the soil A (rice chaff: soybean meal: fish meal: 6:2: 2);

at the beginning of 4 months, 15kg of topdressing soil A is used as a culture medium, and 3 vetiver grass seedlings with the stem length of 15-20cm and the root length of 5-10cm are planted;

spraying benomyl in the amount of 20mg/kg soil in the beginning of 6 months;

in the beginning of 7 months, 1g/kg of soil is used for chasing bocasi, and the soil layer surface is uniformly mixed within 5 cm;

and 7, spraying mixed organic acid in the middle of the month: oxalic acid 20mM/kg soil, citric acid 10mM/kg soil;

spraying benomyl again at the dosage of 20mg/kg soil at the beginning of 8 months;

and 8, spraying mixed organic acid again in the middle ten days of the month: oxalic acid 20mM/kg soil, citric acid 10mM/kg soil;

and (5) harvesting vetiver grass at the beginning of 10 months, and analyzing the heavy metal absorption condition.

Through the agricultural measures, the biomass of the upper part of the vetiver grassland is increased by 59 percent compared with the control group, the Cd concentration of the upper part of the vetiver grassland is increased by 2.58 times compared with the control group, and the actual Cd extraction efficiency is increased by 4.7 times.

Example 2

In 3 days of middle of the month, adding 2g/kg of base fertilizer into the soil A (rice chaff: soybean meal: fish meal: 6:3: 1);

spraying benomyl in the amount of 20mg/kg soil in the beginning of 6 months;

Through the agricultural measures, the biomass of the upper part of the vetiver grassland is increased by 53 percent compared with the control group, the Cd concentration of the overground part is increased by 2.34 times compared with the control group, and the actual Cd extraction efficiency is increased by 4.1 times.

Example 3

In 3 days of middle of the month, adding 2g/kg of base fertilizer into the soil B (rice chaff: soybean meal: fish meal: 6:2: 2);

at the beginning of 4 months and at the beginning of 4 months, taking 15kg of soil B which has been fertilized as a culture medium, and planting 3 vetiver seedlings with the stem length of 15-20cm and the root length of 5-10 cm;

spraying benomyl in the amount of 20mg/kg soil in the beginning of 6 months;

and 7, spraying mixed organic acid in the middle of the month: oxalic acid 10mM/kg soil, citric acid 20mM/kg soil;

and 8, spraying mixed organic acid again in the middle ten days of the month: oxalic acid 10mM/kg soil, citric acid 20mM/kg soil;

Through the agricultural measures, the biomass of the upper part of the vetiver grassland is increased by 85 percent compared with the control group, the concentration of Cd on the upper part of the vetiver grassland is increased by 76 percent compared with the control group, and the actual extraction efficiency of Cd is increased by 2.26 times.

Example 4

In 3 days of middle of the month, adding 2g/kg of base fertilizer into the soil B (rice chaff: soybean meal: fish meal: 6:3: 1);

spraying benomyl in the amount of 20mg/kg soil in the beginning of 6 months;

Through the agricultural measures, the biomass of the upper part of the vetiver grassland is increased by 137 percent compared with the control group, the concentration of Cd on the overground part is increased by 55 percent compared with the control group, and the actual extraction efficiency of Cd is increased by 2.31 times.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. The method for extracting the heavy metal cadmium in the soil is characterized by comprising the following steps:

3) after the benomyl is sprayed for 20-40 days, topdressing with bocasi;

2. The method as claimed in claim 1, wherein the bocacacil is used in step 1) in an amount of 2g/kg soil.

3. The method as claimed in claim 1, wherein the bocacacil is used in step 3) in an amount of 1g/kg soil.

4. The method as claimed in claim 1, wherein the benomyl is used in the steps 2) and 5) in an amount of 20mg/kg soil.

5. The method of claim 1, wherein the heavy metal bioavailability enhancer is a mixture of oxalic acid and citric acid.

6. The method according to claim 5, wherein the molar concentration ratio of oxalic acid to citric acid is 2:1 or 1: 2.

7. the method of claim 5, wherein the oxalic acid is used in an amount of 10 to 20mM/kg of soil, and the citric acid is used in an amount of 10 to 20mM/kg of soil.

8. The method as claimed in claim 1, wherein the rice chaff: bean pulp: the mass ratio of the fish meal is 6:2:2 or 6:3: 1.

9. method according to claim 1, characterized in that it comprises the following steps:

2) spraying benomyl at the beginning of 6 months;

3) topdressing with bocasi in the beginning of 7 months;

5) spraying benomyl for the second time at the beginning of 8 months;

7) and (5) harvesting the vetiver grass at the beginning of 10 months.

10. Use of the method of any one of claims 1 to 9 for remediation of soil contaminated with heavy metal cadmium.