Method for enhancing phytoremediation of Cd-polluted soil through combination of nano-selenium and aspergillus niger

Abstract

The invention discloses a method for repairing Cd-polluted soil by nano-selenium and aspergillus niger reinforced plants, which comprises the following steps: applying nano-selenium and aspergillus niger agents into the Cd-polluted soil to promote the growth of the plants under Cd stress, relieve the toxic action of Cd on the plants and improve the Cd enrichment and absorption capability of the plants. It is found for the first time that SeNPs and aspergillus niger can promote growth of ryegrass under Cd stress, the content of chlorophyll, glutathione and proline of ryegrass under Cd stress is increased, the toxic effect of Cd on ryegrass is relieved, the enrichment capacity of ryegrass on Cd is improved, and the content of Cd in soil is reduced. The invention provides a new means for repairing the Cd-polluted soil.

Description

Technical Field

[0001] The invention relates to the technical field of soil remediation, in particular to a method for nano-selenium combined with Aspergillus niger to strengthen phytoremediation of Cd-contaminated soil. Background Art

[0002] Cadmium (Cd) is a highly toxic heavy metal with a latent period of up to 10-30 years in the human body. In 1993, the International Agency for Research on Cancer (IARC) listed Cd as a human carcinogen. Studies have shown that exposure to cadmium or its compounds significantly increases the risk of cancer. Cd is mainly released into the environment, especially soil and water bodies, through mining, metallurgy, industrial production and agriculture, and is enriched in plants and endangers human health through the food chain. Due to its non-degradable characteristics, the toxic effect of Cd in plants is continuous, seriously affecting the growth and morphology of plant roots, reducing the absorption and transportation of nutrients by plants, inhibiting photosynthesis, reducing soluble proteins, and reducing the activity of antioxidant enzymes. Therefore, it is urgent to remove Cd pollution in the soil.

[0003] At present, the technologies for soil Cd pollution remediation include physical remediation, chemical remediation, phytoremediation, microbial remediation and combined remediation. Traditional physical remediation methods (electric remediation, electric heat remediation and soil leaching, etc.) usually have large engineering workload, high cost and are difficult to apply on a large scale. Chemical remediation (chemical precipitation, ion exchange and electrolysis, etc.) is complicated to operate, which will destroy the soil structure, lead to a decrease in soil fertility, and there is a risk of secondary pollution. Phytoremediation is considered to be a green and sustainable method for soil heavy metal pollution remediation due to its advantages such as low cost and no secondary pollution. However, due to its limitations such as small biomass and long growth cycle, single phytoremediation often fails to achieve the ideal remediation effect, so combined remediation technology has been widely studied and applied. Summary of the invention

[0004] The purpose of the present invention is to provide a method for strengthening phytoremediation of Cd-contaminated soil by using nano-selenium combined with Aspergillus niger.

[0005] In order to achieve the purpose of the present invention, in a first aspect, the present invention provides a method for strengthening plant repair of Cd contaminated soil by combining nano-selenium with Aspergillus niger. The method comprises: applying nano-selenium and Aspergillus niger fungus agent to Cd contaminated soil to promote the growth of plants under Cd stress, alleviate the toxic effects of Cd on plants, and improve the ability of plants to absorb Cd.

[0006] The method of the present invention is mainly suitable for plants that can absorb heavy metals and grow rapidly, such as ryegrass.

[0007] In a second aspect, the present invention provides a method for repairing Cd-contaminated soil, the method comprising: applying nano-selenium and Aspergillus niger fungus agent to the Cd-contaminated soil, and planting ryegrass.

[0008] In a third aspect, the present invention provides a method for promoting the growth of ryegrass under Cd stress, the method comprising: applying nano-selenium and Aspergillus niger fungus agent to the soil where ryegrass is planted.

[0009] In a fourth aspect, the present invention provides a method for increasing the chlorophyll content of ryegrass under Cd stress, the method comprising: applying nano-selenium and Aspergillus niger fungus agent to the soil where ryegrass is planted.

[0010] In a fifth aspect, the present invention provides a method for increasing the glutathione content of ryegrass under Cd stress, the method comprising: applying nano-selenium and Aspergillus niger fungus agent to the soil where ryegrass is planted.

[0011] In a sixth aspect, the present invention provides a method for increasing the proline content of ryegrass under Cd stress, the method comprising: applying nano-selenium and Aspergillus niger fungus agent to the soil where ryegrass is planted.

[0012] In the aforementioned method, the soil is Cd-contaminated soil.

[0013] Furthermore, the Cd in the Cd-contaminated soil exists in the form of Cd(II), and the concentration of Cd(II) in the soil is ≤5 mg / kg.

[0014] Further, the Aspergillus niger agent is added to the soil at a mass ratio of (3g-5g) to soil: 2kg; preferably, the Aspergillus niger agent is added to the soil at a mass ratio of 4g to soil: 2kg. The amount of nano-selenium applied to the soil is 0.5-1.0 mg / kg, preferably 0.5 mg / kg and 1 mg / kg.

[0015] Wherein, the bacterial content of the Aspergillus niger agent is 10 8 Spores / mg.

[0016] Preferably, the Aspergillus niger has a deposit number of CCTCCAF.91004.

[0017] The present invention provides a method for repairing Cd-contaminated soil by using nano-selenium (SeNPs) in combination with Aspergillus niger to strengthen ryegrass, which is to apply SeNPs, Aspergillus niger and ryegrass to repair Cd-contaminated soil. The present invention firstly finds that SeNPs combined with Aspergillus niger can promote the growth of ryegrass under Cd stress, increase the content of chlorophyll, glutathione and proline of ryegrass under Cd stress, alleviate the toxic effect of Cd on ryegrass, improve the enrichment and absorption capacity of ryegrass for Cd, and reduce the content of Cd in soil. The present invention provides a new means for repairing Cd-contaminated soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is a diagram showing the effects of different treatments on ryegrass stem length in a preferred embodiment of the present invention.

[0019] Figure 2 This is a diagram showing the effects of different treatments on ryegrass root length in a preferred embodiment of the present invention.

[0020] Figure 3 This is a graph showing the effects of different treatments on the chlorophyll a content of ryegrass in a preferred embodiment of the present invention.

[0021] Figure 4 This is a graph showing the effects of different treatments on the chlorophyll b content of ryegrass in a preferred embodiment of the present invention.

[0022] Figure 5 This is a graph showing the effects of different treatments on the GSH content of ryegrass in a preferred embodiment of the present invention.

[0023] Figure 6 This is a diagram showing the effects of different treatments on PRO content in ryegrass in a preferred embodiment of the present invention.

[0024] In the figure, different letters such as a, b, and c indicate the significant differences among different treatments. DETAILED DESCRIPTION

[0025] The present invention aims to provide a method for repairing Cd-contaminated soil by using nano-selenium (Selenium nanoparticles, SeNPs) in combination with Aspergillus niger to enhance ryegrass.

[0026] The present invention finds that applying nano-selenium (SeNPs) alone, inoculating Aspergillus niger alone, or applying SeNPs in combination with Aspergillus niger all promotes the growth of ryegrass under Cd pollution stress, and can increase the content of chlorophyll, glutathione, and Aspergillus niger in ryegrass, alleviate the toxic effect of Cd on ryegrass, improve the enrichment and absorption capacity of ryegrass to Cd, reduce the content of Cd in soil, and the treatment effect of SeNPs in combination with Aspergillus niger is the best. Therefore, SeNPs combined with Aspergillus niger help to strengthen the repair effect of ryegrass on Cd-contaminated soil.

[0027] The present invention adopts the following technical solution:

[0028] The present invention provides application of SeNPs combined with Aspergillus niger in promoting plant growth under Cd stress.

[0029] The Aspergillus niger Y-98-4 used in the present invention is purchased from China Center for Type Culture Collection, where it is preserved with the preservation number CCTCC AF.91004. The public can obtain the strain from China Center for Type Culture Collection (CCTCC).

[0030] The plants include, but are not limited to, ryegrass.

[0031] The present invention also provides the use of SeNPs in combination with Aspergillus niger to increase the chlorophyll content of plants under Cd stress.

[0032] The present invention also provides the use of SeNPs in combination with Aspergillus niger to increase the glutathione content of plants under Cd stress.

[0033] The present invention also provides the use of SeNPs in combination with Aspergillus niger in increasing the proline content of plants under Cd stress.

[0034] The Cd stress means that the concentration of Cd(II) is ≤5 mg / kg.

[0035] The present invention also provides a method for using SeNPs and Aspergillus niger to strengthen ryegrass to repair Cd-contaminated soil, which is to use SeNPs and Aspergillus niger to strengthen ryegrass to repair Cd-contaminated soil. The method comprises: adding SeNPs solution and Aspergillus niger fungus agent to Cd-contaminated soil to promote the growth of ryegrass, increase the chlorophyll, glutathione and proline content of ryegrass and improve the ability of ryegrass to enrich Cd.

[0036] The Cd(II) concentration in Cd-contaminated soil is ≤5 mg / kg.

[0037] Preferably, SeNPs are applied to adjust the concentration to a set value, and the Aspergillus niger inoculant is added to the soil at a mass ratio of 3 g:2 kg to 5 g:2 kg (preferably 4 g:2 kg).

[0038] The present invention also provides a method for remediating Cd(II) contaminated soil by using SeNPs in combination with Aspergillus niger to strengthen ryegrass, and the specific steps are as follows:

[0039] 1) Select the well-growing A. niger Y-98-4 slant, inoculate the strain on a sterilized flat solid culture medium, and culture at 28°C for 7 days. Rinse the plate thoroughly with sterile saline, filter the rinsed spore solution with sterile absorbent cotton, collect it in a sterile triangular flask, and shake it in a shaker at 28°C and 130r / min for 2h to finally obtain a spore suspension. After counting with a hemocytometer, the spore solution concentration is 10 7 spores / mL and stored in a 4°C refrigerator for later use.

[0040] 2) Weigh 10% trehalose and 10% skim milk by mass, dissolve in distilled water, stir evenly, sterilize in a high-pressure steam autoclave at 121°C for 30 min for later use. Use the malt extract liquid culture medium group as the proliferation culture medium, take out the prepared spore suspension, mix it according to the volume ratio of spore liquid: culture medium = 1mL: 10mL, inoculate it into a 500mL Erlenmeyer flask, place it in a shaker at 28°C and a speed of 150r / min, and culture it for 72h. Vacuum filter the culture solution and discard the supernatant. Crush it with a homogenizer, add an equal amount of protective agent to the bacteria, shake it thoroughly to disperse the bacteria, 2000r / min, homogenize for 1-2min, mix it evenly with the protective agent, pre-freeze it at -80°C for 12h, and then vacuum freeze-dry it for 36h. Finally, Aspergillus niger freeze-dried powder is obtained. The Aspergillus niger spore content in the dry powder is 10 8 spores / mg and store them in a sealed container in a 4°C refrigerator for later use.

[0041] 3) The concentration of nano-selenium (SeNPs) was 143.83 mg / L, which was synthesized by physical method and provided by Hefei Institutes of Physical Science, Chinese Academy of Sciences.

[0042] 4) Wash the ryegrass seeds, remove the empty shells and poorly developed seeds, add 10% hydrogen peroxide solution to soak and disinfect for 15 minutes to remove the bacteria attached to the surface, rinse with sterile water 3-5 times, and soak overnight. Spread the seeds evenly on a tray filled with clean soil, add appropriate amount of water, and grow seedlings in a constant temperature incubator at 25℃ for 2 weeks.

[0043] 5) Weigh the contaminated soil sample, apply SeNPs to adjust it to the set concentration, add the freeze-dried powder of Aspergillus niger to the test soil at a ratio of 4g:2kg, maintain the soil moisture content at 60%, and stabilize for 3 days. Select the ryegrass seedlings with uniform growth, transplant them into the soil rhizosphere bag containing the test soil and pot them. Plant 10 ryegrasses in each pot with 500g of soil, and cultivate them in a greenhouse at 26℃, with 14h light and 10h dark per day, and a light intensity of 300μmol / (m 2 ·s), add appropriate amount of water every two days to make its water holding capacity reach 60%.

[0044] The first harvest was made at 30 days of cultivation, and the second harvest was made at 60 days of cultivation, and the biomass, physiological indicators, and Cd content in plants and soil were measured. The results showed that compared with the case without the addition of SeNPs and Aspergillus niger, the addition of nano-selenium and Aspergillus niger promoted the growth of ryegrass, increased the chlorophyll, glutathione, and proline content of ryegrass, alleviated the toxic effect of Cd(II) on ryegrass, and improved the enrichment capacity of ryegrass for Cd(II).

[0045] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

[0046] Example 1 Method for repairing Cd-contaminated soil by using nano-selenium (SeNPs) and Aspergillus niger to enhance ryegrass

[0047] 1. Experimental Materials

[0048] The tetraploid annual ryegrass Dongmu 70 was purchased from Jilin Kaiyuan Seed Co., Ltd.

[0049] The strain is Aspergillus niger Y-98-4 (A. niger Y-98-4) with a deposit number of CCTCC AF.91004.

[0050] The concentration of nano-selenium (SeNPs) was 143.83 mg / L. It was synthesized by physical method and provided by Hefei Institutes of Physical Science, Chinese Academy of Sciences.

[0051] The soil was collected from Nongcui Garden of Anhui Agricultural University. It was the surface soil (0-20cm). The physical and chemical properties of the soil were as follows: pH value was 6.37, total nitrogen was 3.39g / kg, total phosphorus was 0.58g / kg, total potassium was 65.30g / kg, and organic matter was 29.30g / kg. The soil samples were air-dried and ground, then passed through a 100-mesh sieve, and after removing plant root tissues and gravel, fertilized at a ratio of 1.28g urea, 0.66g superphosphate, and 0.47g potassium chloride per kilogram of soil, and Cd(NO3)2 was added to make the soil Cd concentration reach 5mg / kg for later use.

[0052] Select the well-growing A. niger Y-98-4 slope, inoculate the strain on a sterilized flat solid medium, and culture at 28°C for 7 days. Rinse the plate thoroughly with sterile saline, filter the rinsed spore liquid with sterile absorbent cotton, collect it in a sterile triangular flask, and shake it in a shaker at 28°C and 130r / min for 2h to finally obtain a spore suspension. After counting with a hemocytometer, the spore liquid concentration is 10 7 spores / mL and stored in a 4°C refrigerator for later use.

[0053] Weigh 10% trehalose and 10% skim milk by mass, dissolve in distilled water, stir evenly, and sterilize in a high-pressure steam sterilizer at 121°C for 30 minutes for later use. Use the malt extract liquid culture medium group as the proliferation culture medium, take out the prepared spore suspension, mix it according to the volume ratio of spore liquid: culture medium = 1mL: 10mL, inoculate it into a 500mL conical flask, place it in a shaker at 28°C and a speed of 150r / min, and culture it for 72h. Vacuum filter the culture solution and discard the supernatant. Crush it with a homogenizer, add an equal amount of protective agent to the bacteria, shake it thoroughly to disperse the bacteria, 2000r / min, homogenize for 1-2min, mix it evenly with the protective agent, pre-freeze it at -80°C for 12h, and then vacuum freeze-dry it for 36h. Finally, Aspergillus niger freeze-dried powder is obtained. The content of Aspergillus niger spores in the dry powder is 10 8 spores / mg and store them in a sealed container in a 4°C refrigerator for later use.

[0054] 2. Experimental design

[0055] Wash the ryegrass seeds, remove the empty shells and poorly developed seeds, add 10% hydrogen peroxide solution to soak and disinfect for 15 minutes to remove the bacteria attached to the surface, rinse with sterile water 3-5 times, and soak overnight. Spread the seeds evenly on a tray filled with clean soil, add appropriate amount of water, and grow seedlings in a constant temperature incubator at 25℃ for 2 weeks.

[0056] 3. Processing group settings

[0057] Six treatments were set up, including (1) control (CK); (2) 0.5 mg / kg Se treatment (S0); (3) 1 mg / kg Se treatment (S1); (4) A. niger Y-98-4 treatment (A); (5) A. niger + 0.5 mg / kg Se treatment (AS0); (6) A. niger + 1 mg / kg Se treatment (AS1), with three parallel groups for each treatment. 500 g of soil sample with a Cd concentration of 5 mg / kg was weighed, and SeNPs were applied to adjust it to the set concentration. A freeze-dried powder of A. niger was prepared and evenly added to the test soil at a ratio of 4 g: 2 kg. The soil water content was maintained at 60% and stabilized for 3 days. The uniformly growing ryegrass seedlings were selected and transplanted into soil rhizosphere bags containing the experimental soil and potted. Ten ryegrass plants were planted in each pot with 500 g of soil. The pots were cultured in a greenhouse at 26 °C with 14 h of light and 10 h of darkness per day and a light intensity of 300 μmol / (m 2 ·s), add appropriate amount of water every two days to make its water holding capacity 60%, harvest for the first time after 30 days of cultivation, and harvest for the second time after 60 days of cultivation. Collect plant samples, rinse repeatedly with sterile water, and measure.

[0058] 4. Determination method

[0059] (1) Determination of ryegrass root and stem length

[0060] The harvested ryegrass was repeatedly washed with distilled water, and 10 seedlings with good growth were selected from each group to measure their root length and stem length.

[0061] (2) Determination of chlorophyll content in ryegrass

[0062] Chlorophyll a content (mg / kg) = Ca (mg / L) × V × n / m

[0063] =(13.95A 665 -6.88A 649 )×V×n / m

[0064] Chlorophyll b content (mg / kg) = Cb (mg / L) × V × n / m

[0065] =(24.96A 649 -7.32A 665 )×V×n / m

[0066] Among them, A 665 and A 649 is the absorbance at wavelengths of 665nm and 649nm, V represents the total volume of the extract (mL), n represents the dilution factor of the extract, and m represents the fresh weight of the leaves (g). The photosynthetic fluorescence efficiency of ryegrass was measured using a chlorophyll fluorescence meter PAM-2500. The Ft value was adjusted, and the ryegrass was bagged and dark treated for 1h. The leaves were clamped with a light adaptation clamp to measure the Fv / Fm value.

[0067] (3) Determination of glutathione (GSH) content in ryegrass

[0068] Determination principle: DTNB (2-nitrobenzoic acid) reacts with GSH to form a complex with a characteristic absorption peak at 412nm, and its absorbance is proportional to the GSH concentration.

[0069] GSH was determined using a kit: 0.20 g of plant tissue was taken, 2 mL of extract was added, and homogenized in an ice bath, then centrifuged at 8000 g for 10 min at 4 °C, and the supernatant was placed on ice for testing. DTNB was added to the supernatant to react with GSH to form a complex, and the absorbance was measured at 412 nm using a UV spectrophotometer.

[0070] (4) Determination of proline content in ryegrass

[0071] Determination principle: Use sulfosalicylic acid (SA) to extract PRO (proline) in the supernatant. After heating treatment, PRO reacts with acidic ninhydrin to generate red with a characteristic absorption peak at 520nm.

[0072] PRO was determined using a kit: 0.20 g of plant tissue was taken, 2 mL of extract was added, and ice bath homogenization was performed. Then, the mixture was placed in boiling water for 10 min of shaking extraction, and centrifuged at 10,000 g for 10 min. The supernatant extract was taken and cooled for later use. PRO in the supernatant was extracted with sulfosalicylic acid (SA). After heating, PRO reacted with acidic ninhydrin to generate red color. After extraction with toluene, the absorbance was measured at 520 nm using a UV spectrophotometer.

[0073] (5) Determination of Cd content in soil

[0074] Weigh 0.10g of air-dried soil sample accurately, grind it and put it into a digestion tube, add HClO4 and concentrated HNO3 solution with a volume ratio of 1:9, and let it stand overnight for 12h. Put the digestion tube into a graphite furnace digestion instrument, continue digestion at 180℃ until the solution is clear, transfer the solution, make it constant to 50mL, filter it with a 0.22μm filter head, take the filtrate, and determine the Cd content with an atomic absorption spectrophotometer.

[0075] 5. Results and Analysis

[0076] Effects of SeNPs combined with Aspergillus niger on ryegrass growth under Cd stress: Effects of different treatments on the root and stem length of ryegrass Figure 1 , Figure 2 As shown. The rhizome length of ryegrass grown for 60 days was higher than that of 30 days, and the rhizome length of AS1 group was the largest at 30 days and 60 days. The stem lengths of A, S0, S1, AS0, and AS1 at 30 days were 32.50, 25.16, 30.99, 33.51, and 34.28 cm, respectively, which were 52.58%, 18.12%, 45.49%, 57.32%, and 60.94% higher than those of the CK treatment group; the root lengths were 4.59, 5.13, 5.20, 6.14, and 9.30 cm, respectively, which were 15.04%, 28.57%, 30.33%, 53.88%, and 133.08% higher than those of the CK treatment group. The 60d stem lengths of A, S0, S1, AS0, and AS1 were 49.23, 36.13, 48.97, 48.67, and 53.07 cm, respectively, which were 36.37%, 0.08%, 35.65%, 34.82%, and 47.01% higher than those of the CK treatment group; the root lengths were 13.30, 10.37, 12.97, 14.23, and 16.13 cm, respectively, which were 51.14%, 17.84%, 47.39%, 61.70%, and 83.30% higher than those of the CK treatment group. Under stress conditions, the stem length and root length of plants can most directly reflect the growth status of plants. In this experiment, the addition of SeNPs and Aspergillus niger increased the stem and root lengths of ryegrass under Cd stress, and the combined treatment increased the most.

[0077] Effects of SeNPs combined with Aspergillus niger on chlorophyll content of ryegrass under Cd stress: Effects of different treatments on chlorophyll content of ryegrass Figure 3 , Figure 4 As shown. The chlorophyll a content of ryegrass grown for 60 days increased compared with that of 30 days. The groups with the highest chlorophyll a and chlorophyll b content at 30 days and 60 days were both AS1. The chlorophyll a content of A, S0, S1, AS0, and AS1 at 30 days were 2.67, 2.47, 2.97, 3.38, and 4.35 mg / kg, respectively, which were 25.49%, 16.00%, 39.55%, 58.85%, and 104.12% higher than that of the CK group, respectively. The chlorophyll b content was 0.84, 0.78, 0.98, 1.06, and 1.30 mg / kg, respectively, which were 21.15%, 12.16%, 41.01%, 52.26%, and 87.07% higher than that of the CK group, respectively. The 60d chlorophyll a contents of A, S0, S1, AS0 and AS1 were 3.51, 3.41, 4.05, 4.58 and 4.83 mg / kg, respectively, which were 56.32%, 52.15%, 80.68%, 104.16% and 115.45% higher than those of CK group; the chlorophyll b contents were 1.54, 1.42, 1.72, 1.78 and 1.90 mg / kg, respectively, which were 33.39%, 22.73%, 48.46%, 53.56% and 63.90% higher than those of CK group. The addition of SeNPs and Aspergillus niger increased the chlorophyll a and chlorophyll b contents of ryegrass, and the composite treatment increased the chlorophyll content of ryegrass the most.

[0078] Effects of SeNPs combined with Aspergillus niger on glutathione content of ryegrass under Cd stress: Effects of different treatments on glutathione content of ryegrass Figure 5 As shown. At 60 days, the GSH content of AS1 group was the highest, which was 205.20 μmol / g. The GSH content of A, S0, S1, AS0, and AS1 groups increased to varying degrees compared with the CK group, among which S1, AS0, and AS1 increased significantly by 45.40%, 74.55%, and 99.35% compared with the CK group, respectively. Therefore, SeNPs and Aspergillus niger increased the glutathione content of ryegrass, alleviated Cd stress, and enhanced the Cd resistance of ryegrass. Aspergillus niger increased more than SeNPs treatment, and the composite treatment had the best effect.

[0079] Effects of SeNPs combined with Aspergillus niger on the proline content of ryegrass under Cd stress: Effects of different treatments on the proline content of ryegrass Figure 6As shown. At 60 days, the PRO content in the AS1 group was the highest, at 16.86 U / g. The PRO content in the S0, S1, AS0, and AS1 groups increased to varying degrees compared with the CK group, increasing by 16.55%, 40.11%, 35.16%, and 44.60%, respectively, with AS1 being significant (p<0.05). It can be seen that SeNPs and Aspergillus niger increased the proline content in ryegrass under Cd stress.

[0080] Effects of SeNPs and Aspergillus niger combined with ryegrass on Cd concentration in soil: The effects of different treatments on Cd concentration in soil are shown in Table 1. At 60 days, the soil Cd concentrations of CK, S0, S1, AS0, and AS1 were reduced by 9.88%, 9.36%, 9.62%, 12.96%, and 16.00%, respectively, compared with the original soil concentrations.

[0081] Table 1 Effects of different treatments on total Cd concentration in soil

[0082]

[0083] The above results show that nano-selenium combined with Aspergillus niger promoted the growth of ryegrass under Cd stress, increased the contents of chlorophyll, glutathione and proline in ryegrass under Cd stress, alleviated the toxic effect of Cd(II) on ryegrass, improved the enrichment capacity of ryegrass for Cd(II), and reduced the concentration of heavy metals in the soil.

[0084] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. Method for strengthening phytoremediation of Cd-contaminated soil by nano-selenium combined with Aspergillus niger. It is characterized in that The method comprises: applying nano-selenium and niger fungus agent to Cd-contaminated soil to promote the growth of plants under Cd stress, alleviate the toxic effect of Cd on plants, and improve the ability of plants to enrich and absorb Cd.

2. The method according to claim 1, It is characterized in that The plants include ryegrass.

3. A method for remediating Cd-contaminated soil, It is characterized in that The method comprises: applying nano-selenium and black aspergillus fungus agent in Cd-contaminated soil, and planting ryegrass.

4. A method for promoting the growth of ryegrass under Cd stress, It is characterized in that The method comprises: applying nano-selenium and black aspergillus fungus agent to the soil where ryegrass is planted; The soil is Cd-contaminated soil.

5. A method for increasing the chlorophyll content of ryegrass under Cd stress, It is characterized in that The method comprises: applying nano-selenium and black aspergillus fungus agent to the soil where ryegrass is planted; The soil is Cd-contaminated soil.

6. A method for increasing the glutathione content of ryegrass under Cd stress, It is characterized in that The method comprises: applying nano-selenium and black aspergillus fungus agent to the soil where ryegrass is planted; The soil is Cd-contaminated soil.

7. A method for increasing the proline content of ryegrass under Cd stress, It is characterized in that The method comprises: applying nano-selenium and black aspergillus fungus agent to the soil where ryegrass is planted; The soil is Cd-contaminated soil.

8. The method according to any one of claims 1 to 7, It is characterized in that The Cd in the Cd-contaminated soil exists in the form of Cd(II), and the concentration of Cd(II) in the soil is ≤5 mg / kg.

9. The method according to claim 8, It is characterized in that The Aspergillus niger fungus agent is added to the soil according to the mass ratio of Aspergillus niger fungus agent to soil (3g-5g):2kg; the amount of nano-selenium applied to the soil is 0.5-1.0mg / kg; Wherein, the bacterial content of the Aspergillus niger agent is 10 8 Spores / mg.

10. The method according to claim 9, It is characterized in that The deposit number of the Aspergillus niger is CCTCCAF.91004.

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