CN102632074A - Method for repairing heavy metal polluted soil by using radix achyranthis bidentatae as manganese hyperaccumulator - Google Patents

Abstract

The invention relates to a technology for repairing heavy metal polluted soil, and in particular relates to a method for repairing heavy metal polluted soil by using radix achyranthis bidentatae as a manganese hyperaccumulator. The radix achyranthis bidentatae belongs to a renascent herb, and found by field investigation, the radix achyranthis bidentatae has strong tolerance and enrichment capacity on manganese. Indoor culture experiments prove that the radix achyranthis bidentatae is planted in manganese polluted soil, absorbs manganese from the soil by roots, and transports the manganese to an overground part for accumulation; and when growing to maturity, the radix achyranthis bidentatae is harvested and duly handled, thus the purpose of removing excessive manganese from the soil is achieved. Through a mode of continuously planting the radix achyranthis bidentatae on the manganese polluted soil and continually harvesting the radix achyranthis bidentatae, the manganese in the polluted soil is continuously extracted until the content of the manganese in the soil reaches the standard of environmental safety. The method is used for repairing the manganese polluted soil, and is a green and safe polluted soil treatment method.

Description

A method for remediating heavy metal-contaminated soil using a manganese hyperaccumulator plant Achyranthes bidentata

technical field

The invention relates to the technical field of phytoremediation of heavy metal-contaminated soil, in particular to a method for remediating heavy metal-contaminated soil by using a manganese hyperaccumulator plant Achyranthes bidentata.

Background technique

Chongqing is rich in manganese ore resources, but the environmental pollution caused by manganese ore mining and processing is also very serious. Among them, Xiushan County of Chongqing City, Huayuan County of Hunan Province, and Songtao County of Guizhou Province are called the "Golden Triangle" of China's manganese ore due to their rich manganese ore resources. All". Xiushan County started to develop the manganese industry in 2001, and the contribution rate of the manganese industry to the local finance reached 70%. But at the same time of rapid economic development, the local ecological environment has also suffered serious pollution and damage. During the mining and processing of manganese ore, due to backward technology, poor equipment, and poor management, waste water and waste gas are discharged randomly, and waste residues are piled up in the field without treatment, resulting in the pollution of local rivers and acid mist. A large area of crops and wild vegetation died under the erosion of manganese poisoning, and a large number of fertile fields lost their original ecological functions and production capacity due to manganese pollution. Therefore, how to control and reduce the environmental pollution and harm of manganese poisoning has become an increasingly prominent problem. However, the conventional methods of remediation of contaminated soil, such as soil replacement method, leaching method, heat treatment, curing, etc., have many problems in large-scale promotion due to their high technical requirements, high economic costs, or serious damage to soil structure. Phytoremediation technology is a new type of new technology that uses hyperaccumulator plants to remove heavy metal pollutants from polluted environmental media or reduce the risk of heavy metal pollution. It can not only repair heavy metal polluted land, but also improve the ecological environment of mining areas. High-grade tailings or precious metals are enriched in the land, realizing the unity of land environmental protection and efficient recycling of metal mineral resources. Compared with traditional governance methods, this technology has shown great vitality due to its potential advantages of high efficiency, economy and its ecological coordination.

Phytoremediation in a broad sense refers to the technology of using plants (including grasses, shrubs, and trees) to remove heavy metals in polluted soil and wastewater, including phytoextraction, rhizosphere filtration, plant volatilization, and phytofixation. The most promising of these are phytoextracts, commonly referred to as phytoremediation. Phytoextraction technology refers to a method that uses the roots of metal-enriched plants or hyper-accumulated plants to extract metals from the soil and transport them to the aboveground parts of plants, and remove heavy metals in the soil by harvesting the aboveground materials. Hyperaccumulator plants are the basis of phytoremediation, and finding and developing hyperaccumulator plants with large biomass and strong ability to accumulate heavy metals is the primary task of phytoremediation technology towards engineering applications. At present, the measurement standards for manganese hyperaccumulator plants include three indicators: one is the critical content characteristics, the manganese content in the leaves or shoots (dry weight) of manganese hyperaccumulator plants reaches 10000 mg/kg; the other is the transfer characteristics, The content of manganese in the aboveground part of the plant is greater than that in the root; the third is that the hyperaccumulator has the characteristics of tolerance and enrichment. The use of hyperaccumulators to remediate heavy metal-contaminated soils is currently the most researched and most promising method.

Contents of the invention

The object of the present invention is to provide a kind of method utilizing manganese super-enrichment plant Achyranthes bidentata to restore heavy metal-contaminated soil, the method does not destroy soil original structure, under the situation of keeping soil microbial activity, Achyranthes bidentata is planted on the manganese-contaminated soil, The root system of Achyranthes bidentata is used to absorb a large amount of manganese from the soil and transport it to the aboveground part for accumulation. After the plant matures, it is harvested and removed from the soil to achieve the purpose of restoration. The method is green and safe, and has the advantages of low input cost, small engineering quantity, no secondary pollution, and reduced soil erosion.

To achieve the above object, the technical scheme of the present invention is as follows:

The manganese hyperaccumulator plant Achyranthes bidentata was used to remediate heavy metal-contaminated soil. Achyranthes bidentata was planted on the manganese-contaminated soil. After the Achyranthes bidentata plant grew and matured, the whole plant was removed from the contaminated soil and properly treated to achieve the purpose of restoration.

The plant Achyranthes bidentata used in the present invention is propagated by seeds, and the plants belong to manganese-enriched plants.

The plant Achyranthes bidentata used in the present invention soaks the seeds in warm water at 30°C for 8-12 hours before sowing, removes them and puts them in a container, covers them with a damp cloth to keep them moist, and when 50% of the seeds germinate, takes them out and mixes them with an appropriate amount of fine soil, and spreads them .

Plant Achyranthes bidentata used in the present invention, plant Achyranthes bidentata on manganese-contaminated soil, Achyranthes bidentata absorbs manganese from polluted soil and transfers to above-ground part, after Achyranthes bidentata plant grows mature, whole plant is removed from polluted soil, By continuously planting Achyranthes bidentata, the above operations are repeated until the manganese content in the soil reaches the environmental safety standard.

The plant used in the present invention is Achyranthes bidentata: Achyranthes bidentata , a perennial herb with a height of 70-120cm. Roots are slender, yellowish-white, fleshy. Stem ribbed, sparsely pilose, nodes swollen like knees. The leaves are opposite, oval or needle-shaped, sparsely pubescent on both sides, and denser along the main vein. Spikes are terminal and axillary, the peduncle is elongated after flowering, and the flowers are folded downward and close to the total flower; bract 1, membranous, broadly ovate, apex acuminate, bracteole 2, spiny, long About 3 mm, with 1 egg-shaped membrane on both sides of the base, about 0.3 mm long, bracts and bracteoles without ciliates; perianth segments 5, green, mostly with 1 vein; stamens 5, filaments connate at the lower part, degenerated Stamens shorter than filaments, ligulate, top rounded or shallowly wavy; ovary superior. Utricle oblong. The flowering period is from July to September, and the fruiting period is from September to October.

The advantages that the present invention has:

1. The plant Achyranthes bidentata adopted in the present invention has large biomass, rapid growth, strong fecundity, and strong tolerance, absorption and super-enrichment ability to manganese. Achyranthes knuckles are planted in manganese-contaminated soil, and a large amount of manganese is absorbed from the soil through the plant roots and transported to the ground. After the plant matures, the whole plant is removed from the soil and treated properly, so as to achieve fast, effective, green and safe. The purpose of remediating manganese-contaminated soil.

2. The present invention uses Achyranthes bidentata to restore manganese-contaminated soil, which is green and safe, and has the advantages of low input cost, small engineering volume, no secondary pollution, and reduced soil erosion.

Description of drawings

Figure 1 is the detection chart of Achyranthes knuckle biomass treated with different concentrations of manganese

Figure 2 is the detection chart of root length and plant height of Achyranthes knuckle treated with different concentrations of manganese

Figure 3 is the detection chart of manganese content in Achyranthes knuckle treated with different concentrations of manganese

Figure 4 is the detection chart of manganese accumulation in Achyranthes knuckle treated with different concentrations of manganese.

Detailed ways

The experimental soil type is purple soil, and each pot contains 2 kg of soil. According to the nutrient requirements of potted crops (N 200 mg·kg ^-1 , P ₂ O ₅ 100 mg·kg ^-1 , K ₂ O 150—200 mg·kg ^-1 ) Add 400, 200, 300 mg·kg ^-1 of urea, potassium dihydrogen phosphate and potassium sulfate respectively. A total of 8 treatments were set up in the experiment, namely: CK (control, no manganese added), 3000, 4000, 5000, 6000, 7000, 8000, 9000 and 10000 mg/kg, added in the form of MnCl ₂ .4H ₂ O, each 3 replicates per treatment. After equilibrating for 1 week, soak the seeds in warm water at 30°C for 8-12 hours, remove them and put them in a container, cover them with a damp cloth to keep them moist, and when 50% of the seeds germinate, take them out and mix them with an appropriate amount of fine soil, and spread them on the surface of the manganese-contaminated soil. After the seedlings have emerged, thin the seedlings, leaving 1 plant in each pot. According to the soil water shortage in the pot, water it from time to time to keep the soil water content at about 75-80% of the field water holding capacity. Place a plastic tray under the pot and pour the soil moisture seepage back into the pot. The plant growth time is 3 months.

The harvested Achyranthes bidentata samples were repeatedly rinsed with tap water to remove the soil and dirt adhering to the plant samples, then rinsed with deionized water, and the surface water was blotted dry with absorbent paper. Divide the samples into aerial part and root system, and measure the plant height, root length and fresh weight of each part. Fresh samples were killed at 105°C for 30 minutes, then dried at 70°C to constant weight, and the dry matter was measured. Grind with a stainless steel pulverizer and pass through a 60-mesh nylon mesh sieve for analysis and determination. The plant samples were digested with HNO ₃ -HClO ₄ and the manganese content was determined by atomic absorption spectrophotometer.

Microsoft Excel 2003 was used to calculate the mean value and standard deviation, expressed in the form of mean ± standard deviation, and the least significant difference test (LSD test) was used to test the significance of the difference between plant samples.

The experimental results are as follows:

Effects of manganese pollution on the growth and development of Achyranthes knuckles. Referring to Figure 1 and Figure 2, it can be seen that with the increase of manganese concentration in the medium, except for the root length of Achyranthes bidentata, the root, aboveground biomass and plant height were all significantly reduced (p<0.01), indicating that adding Manganese inhibits the growth and development of Achyranthes knuckles. Compared with the control, when the manganese concentration was 3000 mg/kg, aboveground and root biomass decreased by 43% and 66%, respectively, and plant height decreased by 24%. The root biomass decreased by 90% and 84%, respectively, and the plant height decreased by 67%. After exceeding 4000 mg/kg, Achyranthes bidentata could no longer survive.

Absorption of manganese by Achyranthes knuckles. Referring to Figure 3, it can be seen that the manganese content in the aerial part of Achyranthes knuckles increased with the increase of manganese supply level (p<0.01), and the manganese content in the roots also increased (p<0.05). When the manganese concentration was 4000 mg/kg, the manganese content in the aerial part of Achyranthes bidentata was 18809.91 mg/kg, far exceeding the critical content of 10000 mg/kg in manganese hyperaccumulator plants.

Referring to Table 1, it can be seen that Achyranthes bidentata has a strong ability to absorb and enrich manganese. The bioconcentration coefficient refers to the ratio of the content of a certain heavy metal in the plant to the content of the same heavy metal in the soil, reflecting the enrichment of heavy metal elements in the soil by plants. The higher the enrichment factor, the stronger the ability of plants to absorb and accumulate heavy metals, which is more conducive to the extraction and restoration of heavy metal-contaminated soil by plants. When the manganese concentration was 3000 and 4000 mg/kg, the bioaccumulation coefficients were 1.79 and 2.55, respectively, both greater than 1, indicating that Achyranthes bidentata possessed the characteristics of the enrichment coefficient of manganese hyperaccumulator plants.

Table 1 Enrichment coefficient, transfer coefficient and extraction rate of manganese in Achyranthes bidentata under different manganese treatment concentrations

Manganese treatment concentration (mg/kg) Enrichment factor transfer coefficient Extraction rate (%) CK the 2.13 0.15 3000 1.79 7.46 0.72 4000 2.55 9.07 0.19

The biotransfer coefficient refers to the ratio of the heavy metal content in the aboveground part of the plant to the heavy metal content in the root, which is used to evaluate the ability of the plant to transport and accumulate heavy metals from the root system to the aboveground part. The higher the biological transfer coefficient, the stronger the transport capacity of heavy metals from underground to aboveground organs. Referring to Table 1, it can be seen that when the manganese concentration was 3000 and 4000 mg/kg, the biotransfer coefficients were 7.46 and 9.07, respectively, both greater than 1, which conformed to the general characteristics of metal accumulation in hyperaccumulator plants. The distribution of manganese in Achyranthes bidentata shoots and root system was significantly different, and more than 95% of the manganese absorbed by the whole plant was distributed in the shoot, indicating that the manganese absorbed by Achyranthes bidentata root system had a strong ability to transport to the shoot.

The extraction rate of heavy metals refers to the ratio of the accumulation of heavy metals in plants to the content of heavy metals in soil. Referring to Table 1, it can be seen that when the manganese concentration is 3000 and 4000 mg/kg, the extraction rate is 0.72% and 0.19%, respectively, and the extraction rate decreases with the increase of manganese concentration in the soil.

Referring to Figure 4, it can be seen that the manganese accumulation in the aerial part of Achyranthes knuckles (ug/pot) is much greater than that in the root (p<0.01). When the manganese concentration is 3000 mg/kg, the manganese accumulation in the aerial part and root are 77439.19 and 1463.61 ug respectively / basin, the shoot is 52.91 times that of the root. When the concentration of manganese is 4000 mg/kg, the accumulation of manganese in the shoot and root is reduced to 26521.98 and 1098.67 ug/basin, respectively, and the shoot is 24.14 times that of the root. Therefore, by harvesting the above-ground parts of the plants, the purpose of removing manganese pollution in the soil can also be achieved.

Show by above-mentioned experimental result, plant Achyranthes bidentata adopted in the present invention has very strong enrichment and accumulation ability to manganese, Achyranthes bidentata is planted on the manganese polluted soil, when manganese addition concentration is 4000 mg/kg in the soil, Achyranthes bidentata above ground The local manganese concentration was 18809.91 mg/kg, which far exceeded the critical content of 10000 mg/kg for manganese hyperaccumulator plants. At this time, the biotransfer coefficient and enrichment coefficient were 9.07 and 2.55, respectively, which reached the standard of manganese hyperaccumulator plants. . When the achyranthes is mature, remove excess manganese from the soil by removing the entire plant from the soil and disposing of it properly. Achyranthes bidentata was planted continuously on the manganese-contaminated soil, and the whole plant was harvested continuously and the soil was removed until the manganese content in the soil reached the environmental safety standard. By adopting the invention, the soil polluted by heavy metals can be repaired and the environment can be beautified, and it is a cheap, green and safe soil treatment technology.

Claims (4)

1. A method of utilizing manganese hyperaccumulation plant Achyranthes bidentata to repair heavy metal-contaminated soil, characterized in that: plant Achyranthes bidentata on manganese-contaminated soil, and when the Achyranthes bidentata plant is ripe, whole plant is removed from the polluted soil, So as to achieve the purpose of remediating manganese-contaminated soil. 2. The method for repairing heavy metal-contaminated soil by using the manganese hyperaccumulator plant Achyranthes bidentata according to claim 1, characterized in that: the plant Achyranthes bidentata is propagated by seeds, and the plant is a manganese-enriched plant. 3. The method for repairing heavy metal-contaminated soil using the manganese hyperaccumulator plant Achyranthes bidentata according to claim 1, wherein the seeds are soaked in warm water at 30°C for 8-12 hours before sowing, then taken out and put into a container , Cover with a damp cloth to keep it moist, and when 50% of the seeds germinate, take it out and mix in an appropriate amount of fine soil for spreading. 4. the method for utilizing manganese hyperaccumulator plant Achyranthes bidentata to repair heavy metal-contaminated soil according to claim 1, is characterized in that: plant Achyranthes bidentata on manganese-contaminated soil, Achyranthes bidentata absorbs manganese from polluted soil and transfers to above-ground part , when the Achyranthes bidentata plant grows mature, the whole plant is removed from the polluted soil, and the above operation is repeated through continuous planting of Achyranthes bidentata until the manganese content in the soil reaches the environmental safety standard.

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