Method for repairing soil cadmium pollution based on willow-microorganisms

Abstract

The invention provides a method for repairing cadmium-polluted soil based on willow-microorganisms, and belongs to the technical field of soil heavy metal pollution remediation, and after willow is cultured by adopting trichoderma harzianum root soaking, the willow is planted into the cadmium-polluted soil. According to the method, the salix cheilophila is selected as a tree species to repair the cadmium-contaminated soil, the salix cheilophila is a fast-growing and high-biomass excellent clonal system and shows high cadmium resistance, meanwhile, all tissues can efficiently enrich cadmium, and the cadmium transfer coefficient is larger than that of the salix cheilophila; according to the method, the willows are cultured by adopting microbial root soaking, the influence of soil environment factors on microorganisms in a microbial remediation method is avoided, and the cadmium enrichment capacity of the willows can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of soil heavy metal pollution remediation, and specifically is a method for remediating soil cadmium pollution based on willow-microorganisms. Background Art

[0002] Cadmium deposition in the atmosphere, the use of pesticides, fertilizers and plastic films, sewage irrigation, sludge fertilization, the accumulation of heavy metal wastes, and acidic wastewater pollution in metal mines can easily cause cadmium pollution in the soil. Cadmium pollution in the soil will destroy the microbial community structure of the soil. For crops, soil cadmium pollution will lead to reduced yields and seriously affect the quality of agricultural products. Cadmium will accumulate in the edible parts of plants, such as leafy vegetables. Cadmium pollution will reduce the content of nutrients such as vitamins and proteins in vegetables. At the same time, it may also produce some substances that are harmful to the human body, affecting the safety and nutritional value of agricultural products. Cadmium in the soil will be transmitted to animals and humans through the food chain, causing damage to the liver and kidneys of animals and humans, affecting the normal metabolism and detoxification function of the liver and kidneys. Therefore, the remediation of soil cadmium pollution is very necessary.

[0003] The methods for controlling soil cadmium pollution include physical control methods, chemical control methods and biological control methods.

[0004] Among the physical treatment methods, the soil removal method is to remove the contaminated soil. However, this method is costly, requires a large amount of high-quality soil, and will produce a large amount of contaminated soil that needs to be treated, which may cause secondary pollution to other areas. The deep tillage method mixes the surface contaminated soil with the deep uncontaminated soil through deep tillage, thereby reducing the cadmium concentration in the surface soil. This method can be used in some farmlands with mild cadmium contamination. However, this method may cause deep soil to be contaminated, and it is not effective for deep cadmium-contaminated soil.

[0005] Among chemical treatment methods, chemical precipitation refers to adding chemical agents to contaminated soil to make cadmium form insoluble precipitates. For example, adding lime (CaO), the calcium ions (Ca 2+ ) and cadmium ions (Cd 2+ ) to form insoluble precipitates such as cadmium hydroxide (Cd(OH)2). This method is relatively simple to operate and has low cost. However, it may change the chemical properties of the soil, such as pH, and affect other biological and chemical processes in the soil. Moreover, the precipitate may dissolve again over time, causing cadmium to be released into the soil again. This method has little effect on the physical and chemical properties of the soil, but the capacity of the ion exchanger is limited and needs to be replaced regularly, which is costly.

[0006] Among the biological treatment methods, phytoremediation uses the absorption and enrichment ability of certain plants to remove cadmium from the soil. Microbial remediation uses certain microorganisms to reduce the toxicity or mobility of cadmium in the soil through biotransformation and biosorption. This method has the advantages of in-situ remediation and does not damage the soil structure, but the growth and activity of microorganisms are greatly affected by soil environmental factors (such as temperature, humidity, pH, etc.).

[0007] The use of phytoremediation to remove cadmium from the soil is relatively low-cost, easy to implement, and has little secondary damage to the soil, but the most difficult part is the selection of plants and how to improve the plant's enrichment and isolation performance. Willow is suitable for a variety of ecological environments, and can grow in mountains, plains, sand dunes, and polar regions. It can also grow in places with harsh ecological conditions, and it is extremely easy to survive by cutting. The present invention selects willow as a plant for phytoremediation to explore how to improve the repair capacity of soil cadmium pollution. Summary of the invention

[0008] In order to solve the problems in the prior art, the present invention proposes a method for repairing soil cadmium pollution based on willow-microorganisms.

[0009] Technical solution: A willow-microorganism-based method for remediating cadmium-contaminated soil, in which willows are cultured with Trichoderma harzianum roots and then planted in cadmium-contaminated soil.

[0010] Furthermore, after the willow trees were cultured by root immersion in a plant culture solution containing Trichoderma harzianum, the willow trees were planted in cadmium-contaminated soil.

[0011] Furthermore, the willow tree is a willow of the family Psoralea corylifolia.

[0012] Further, in the plant culture solution containing Trichoderma harzianum, the concentration of Trichoderma harzianum is 10 8 CFU ml -1 -10 16 CFU ml -1 .

[0013] Furthermore, the root immersion culture time is 72 hours.

[0014] Furthermore, the plant culture solution is Hoagland's solution.

[0015] Beneficial effects:

[0016] 1. The present invention selects Salix babylonica as the tree species to repair cadmium-contaminated soil. Salix babylonica is a fast-growing, high-biomass, excellent asexual system that exhibits strong cadmium resistance. At the same time, each tissue can efficiently enrich cadmium, and the cadmium transport coefficient is greater than 1, indicating that Salix babylonica is an excellent candidate tree species for repairing cadmium-contaminated soil.

[0017] 2. The present invention uses microorganisms to immerse the roots of willows for cultivation. Unlike the microbial remediation method where the microorganisms are affected by soil environmental factors, the ability of willows to enrich cadmium can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the process of inoculating Trichoderma harzianum in the willow of the embodiment.

[0019] Figure 2 Schematic diagram of plant height, fresh weight and dry weight of the treated cuttings in the embodiment; wherein A is the plant height of the cuttings, B is the fresh weight of the cuttings, and C is the dry weight of the cuttings.

[0020] Figure 3 is the cadmium content and cadmium transport coefficient of the roots, stems and leaves of the cuttings after treatment in the embodiment. Wherein, A is the concentration of Trichoderma harzianum (10 8 CFU ml -1 , 10 16 CFU ml -1 Comparative analysis results of cadmium concentration in roots, stems and leaves of cuttings treated with Trichoderma harzianum (10 8 CFU ml -1 , 10 16 CFU ml -1 , 0) treated with three groups of Trichoderma harzianum (10 8 CFU ml -1 , 10 16 CFU ml -1 , 0) treated cuttings of cadmium transport coefficient. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is described in detail below through embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0022] Example 1

[0023] 1. Willow cutting materials:

[0024] Select branches of the willow of Yangzhou University that have the same growth rate and cut them into 12cm long cuttings. In order to make the root system develop better, the cuttings are placed in half-strength Hogland nutrient solution for rooting. After 33 days of hydroponics, when the cuttings have roots about 8-12cm long, select the cuttings that have the same growth rate and prepare for transplanting.

[0025] 2. Use natural cadmium-contaminated soil to cultivate cuttings:

[0026] Natural cadmium-contaminated soil (6.35 mg / kg Cd) was collected from the Changshu Research Base of Jiangsu Academy of Forestry, China (120°38'9"E, 31°43'23"N).

[0027] Place the rooted cuttings in a low concentration (10 8 CFU ml -1 ), high concentration (10 16 CFU ml -1 )-Hoagland solution and a control group (the control group was Hoagland solution without inoculum), with 8 replicates per group, left for 72 hours, and then planted in pots with cadmium-contaminated soil.

[0028] Greenhouse conditions were set as follows: natural light period, 70% humidity, and day and night temperatures of 28°C and 22°C, respectively.

[0029] Water the plant once every 3 days to maintain a certain humidity in the planting pot. When the willow branches grow to a point where the leaves turn yellow (after about 8 months of maintenance, the leaves of the willow branches begin to turn yellow, and sampling is performed before the leaves fall off), sampling is performed. The process is as follows: Figure 1 shown.

[0030] 3. Sample collection and biomass measurement:

[0031] The roots of S. truncatula were carefully rinsed in 20 mM EDTA-Na2 for 10 min and washed with deionized water to remove surface Cd. Plants were photographed using a digital camera. To determine biomass, roots, stems, and leaves of seedlings were collected, dried at 70 °C for 3 days, and then weighed. Seven biological replicates were analyzed to assess the dry weight of tissue for each genotype and treatment.

[0032] 4. Determination of Cd content:

[0033] The roots, stems and leaves of Ligustrum lucidum were ground into powder in a mill. The samples (0.05 g) were transferred to a mixture of 3 mL ultrapure water and 5 mL concentrated HNO3 and then heated at 180 °C for 40 min in a microwave cooker (MARS5, CEM, USA). After cooling, the supernatants were mixed, diluted to 10 mL with ultrapure water, and filtered through a 0.22 μm cellulose acetate membrane filter. Standard Cd solution (GBW(E)080119, China Institute of Metrology) was used for quality control. Inductively coupled plasma optical emission spectrometry (ICPOES, iCAP6300, Thermo Scientific, MA, USA) was used to analyze the Cd content in the samples. All steps were carried out according to the manufacturer's instructions, and three replicates were determined for each genotype and treatment.

[0034] 5. Determination results of Cd content:

[0035] The root culture of willow cuttings with Trichoderma harzianum has a significant effect on improving the cadmium enrichment of willow. Cadmium content and cadmium transport coefficient are important indicators of the cadmium enrichment capacity of willow in cadmium-contaminated soil.

[0036] 1) Compared with the control group (CK), the root culture of willow cuttings with Trichoderma harzianum increased plant height and biomass. Figure 2 As shown, low concentration (10 8 CFU ml -1 ) The total fresh weight of the willow of Trichoderma harzianum inoculated was increased by 13.86% and the plant height was increased by 34.90% compared with the control group; high concentration (10 16 CFU ml -1 ) The total fresh weight of willows inoculated with Trichoderma harzianum increased by 41.11% and the plant height increased by 50.76% compared with the control group. 16 CFU ml -1 ) Trichoderma harzianum can more effectively increase the biomass and plant height of plants.

[0037] 2) Compared with the control group (CK), Figure 3 As shown in A and B, low concentration (10 16 CFU ml -1 ) The cadmium content in the roots of the willow inoculated with Trichoderma harzianum increased by 12.07%, the stems increased by 26.04%, and the leaves increased by 34.94%; the cadmium content in the roots of the willow inoculated with high concentrations of Trichoderma harzianum decreased by 18.92%, increased by 34.41% in the stems, and increased by 24.93% in the leaves. It can be seen that low concentrations of Trichoderma harzianum can effectively improve the root's ability to absorb cadmium, and the cadmium content in the stems and leaves increased by more than 25% compared with the control group. At the same time, compared with the high concentration of Trichoderma harzianum inoculated with low concentrations of Trichoderma harzianum, the cadmium content in the stems increased by 8.37% and the cadmium content in the leaves increased by 10.01%. It is worth noting that the cadmium content in the roots of the willow inoculated with high concentrations of Trichoderma harzianum has been significantly reduced. It is possible that too high a concentration of Trichoderma harzianum will accelerate the ability of the roots to transport cadmium online.

[0038] 3) The transport coefficient (TF) is an indicator for evaluating the ability of plants to transport and accumulate heavy metals from underground to aboveground parts. In this example, the cadmium transport coefficient of the control group of Ligustrum lucidum was 1.6878, and the low concentration (10 8 CFU ml -1 ) The cadmium transport coefficient of the schisandra chinensis inoculated with Trichoderma harzianum was 2.4857, and the high concentration (10 16 CFU ml -1) The cadmium transport coefficient of Trichoderma harzianum inoculated with the lily of the valley was 1.7325. Compared with the control group, the cadmium transport coefficient increased by 47.27% at low concentrations and by 2.64% at high concentrations. This data shows that low concentrations (10 8 CFU ml -1 ) The cadmium transport capacity of willow inoculated with Trichoderma harzianum was increased by 47.27% compared with the cadmium accumulation capacity of willow without the addition of Trichoderma harzianum, which effectively improved the cadmium accumulation capacity of willow and ensured the normal growth of the plant through a variety of physiological effects, which is of great significance for enhancing the phytoremediation effect of cadmium-contaminated soil.

[0039] The results of this example show that soaking seeds with Trichoderma harzianum can improve the Cd transport capacity of willow trees. 8 CFUml -1 ) The willow inoculated with Trichoderma harzianum increased the cadmium transport coefficient by 47.27%, which is more than double the 20% expected in the experiment, indicating that the willow-microorganism remediation system obtained in this embodiment is efficient and feasible. Moreover, the Trichoderma harzianum used in this embodiment is a product officially sold on the market, with low price and stable performance, and can become the preferred microbial agent for the remediation of cadmium-contaminated soil.

[0040] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention.

Claims

1. A method for remediating cadmium-contaminated soil based on willow-microorganisms, characterized in that: After willow trees were cultured with Trichoderma harzianum root soaking, they were planted in cadmium-contaminated soil.

2. The method according to claim 1, characterized in that After willow trees were cultured by dipping their roots in a plant culture solution containing Trichoderma harzianum, they were planted in cadmium-contaminated soil.

3. The method according to claim 2, characterized in that The willow tree is Willow of the Safflower.

4. The method according to claim 2 or 3, characterized in that: In the plant culture solution containing Trichoderma harzianum, the concentration of Trichoderma harzianum is 10 8 CFU ml -1 -10 16 CFU ml -1 .

5. The method according to claim 2, characterized in that: The root immersion culture time is 72 hours.

6. The method according to claim 2, characterized in that The plant culture solution is Hoagland's solution.

Images