Lead-zinc tolerant synechococco sp. sk-5 and its application in heavy metal contaminated water purification or soil remediation

Abstract

The application provides a lead and zinc tolerant Microsphaeridium SK-5, which is preserved in the China Center for Type Culture Collection on June 9, 2023, and has a preservation number of CCTCC NO: M 2023971. The application also provides application of the lead and zinc tolerant Microsphaeridium SK-5 in purifying lead and / or zinc in a polluted water body, in repairing a polluted soil containing lead and / or zinc, and in promoting planting, growth and absorption and transportation of lead and / or zinc of plants in the polluted soil containing lead and / or zinc. The lead and zinc tolerant Microsphaeridium SK-5 has a significant advantage in absorption and transportation of lead and / or zinc in a polluted water body and tailings compared to existing algae, can quickly reduce the content of lead and / or zinc in the water body or soil, and can promote planting and growth of plants in the polluted soil and promote absorption and transportation of lead and / or zinc of plants, thereby providing a new idea for promoting plant repair of the polluted soil.

Description

Technical Field

[0001] This invention patent relates to the field of microbial and environmental engineering technology, and in particular to a lead- and zinc tolerant algae SK-5 and its application in the purification of heavy metal polluted water or soil remediation. Background Technology

[0002] Lead and zinc are common environmental pollutants, widely present in industrial, metallurgical, mining, and agricultural activities. Lead and zinc pollution has serious impacts on the environment and biological systems. Their accumulation can lead to soil and water pollution, damage soil texture and structure, reduce soil fertility, inhibit plant growth, and threaten human and animal health. China is one of the world's major lead and zinc producing regions. Long-term large-scale mining and smelting activities have led to the accumulation and spread of lead and zinc pollution in the soil. Wastewater discharge from lead and zinc smelters and related industrial facilities is also a significant source of lead and zinc pollution.

[0003] Common methods for remediating lead and zinc pollution in water bodies include using precipitants (such as hydroxides, carbonates, and phosphates) to convert heavy metal ions into insoluble precipitates, which are then removed from the water body through sedimentation; immobilizing heavy metal ions on the surface of adsorbents (such as activated carbon, zeolites, polymers, and nanomaterials); and utilizing the physiological and metabolic processes of organisms (such as plants and microorganisms) to reduce heavy metal pollution in water bodies. Methods for remediating lead and zinc pollution in soil include physical remediation (such as deep tillage and topsoil covering), chemical remediation (electrochemical remediation, solidification and stabilization), phytoremediation (phytoextraction, fixation, and evaporation), and microbial remediation.

[0004] Bioremediation is an ideal method for remediating lead and zinc pollution due to its strong sustainability, wide applicability, significant economic benefits, and ability to restore biodiversity in polluted environments. Among these methods, algae have broad application potential in lead and zinc pollution control and remediation. Due to their unique physiological and ecological characteristics, algae's cell walls, extracellular polymeric substances (EPS), and intracellular structures have the ability to adsorb lead and zinc ions, fixing them on the cell surface or inside the cell through adsorption, thus reducing their toxicity to the environment. Algae can also convert lead and zinc ions into insoluble precipitates such as carbonates, phosphates, and sulfates through biotransformation processes, thereby reducing their toxicity and mobility. In addition to reducing heavy metal concentrations and bioavailability, algae can effectively promote soil ecological restoration and subsequent plant growth. Algae can improve soil structure and properties, increase soil organic matter content, and enhance soil water retention and aeration. Algal growth can also promote soil microbial activity, enhancing the stability and function of the soil ecosystem. Simultaneously, algae are one of the main sources of soil nitrogen, and their nitrogen fixation can significantly strengthen the soil nitrogen cycle. Therefore, using algae to treat lead and zinc polluted water and soil is a very promising technology.

[0005] The induction of biocrusts through cyanobacterial inoculation to restore the ecology of arid and semi-arid regions has been widely applied in northern China, and excellent algal species such as *Microcoleis sheathellae*, *Nostoc*, and *Pseudocladophyta* have been screened. However, for lead- and zinc-contaminated soils, there is still a lack of superior algal species with rapid growth rates, large biomass, strong adaptability, and high tolerance to lead and zinc. Mature technical routes for the screening, large-scale cultivation, field inoculation, and post-cultivation maintenance of target algal species have not yet been established. Furthermore, the extent to which target algal species can restore the ecology of contaminated soils in practical applications, including reducing heavy metal stress, improving soil properties, and promoting subsequent plant colonization, remains to be explored. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems existing in the prior art. Therefore, in a first aspect, the present invention provides a lead-zinc tolerant algae SK-5, which was deposited at the China Center for Type Culture Collection on June 9, 2023, with accession number CCTCC NO:M 2023971.

[0007] The 16S rDNA sequence of the lead-zinc tolerant herpessimum SK-5 is shown in SEQ ID NO.1.

[0008] In a second aspect, the present invention provides the application of the lead- and zinc-tolerant algae SK-5 described in the first aspect of the present invention in purifying lead and / or zinc in polluted water.

[0009] Preferably, the polluted water contains lead and zinc, and the concentrations of both lead and zinc are less than 100 mg / L.

[0010] In a third aspect, the present invention provides the application of the lead- and zinc-tolerant herbarium SK-5 described in the first aspect of the present invention in the remediation of soil contaminated with lead and / or zinc.

[0011] Preferably, the contaminated soil contains lead and zinc, with each concentration of lead and zinc being 4000-5000 mg / kg.

[0012] In a fourth aspect, the present invention provides a method for remediating contaminated soil containing lead and / or zinc, comprising the following steps:

[0013] Step 1): Spray the lead-zinc tolerant fine-sheathed filamentous algae SK-5 as described in claim 1 into the contaminated soil;

[0014] Step 2): Add culture medium and water to the contaminated soil, and set up a shade net on the contaminated soil.

[0015] Preferably, after step 2), the method further includes step 3): spreading plant debris on the contaminated soil.

[0016] Preferably, in step 1), the lead-zinc tolerant herbarium SK-5 is in a stable phase; in step 2), the culture medium is BG-11 culture medium.

[0017] Preferably, in step 3), the plant waste is selected from at least one of sow thistle waste and beggar-ticks waste, and the sowing density of the plant waste is 0.48-0.52 kg / m². 2 .

[0018] In a fifth aspect of the invention, the invention provides the use of the lead- and zinc-tolerant fine-sheathed filamentous algae SK-5 described in the first aspect of the invention in promoting the establishment, growth, absorption, and translocation of lead and / or zinc in contaminated soils containing lead and / or zinc.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. This invention provides a lead- and zinc tolerant algae, SK-5, which is green and environmentally friendly, has no risk of secondary pollution, and is economical. Compared with existing algae, it has significant advantages in the absorption and transport of lead and / or zinc in polluted water bodies and tailings. Using this lead- and zinc tolerant algae SK-5 to achieve the absorption and transport of lead and / or zinc results in lower remediation costs for polluted water bodies and tailings compared to physical / chemical methods.

[0021] 2. This invention provides the application of the aforementioned lead- and zinc-tolerant *Gnaphalium affine* SK-5 in purifying lead and / or zinc in polluted water bodies and in remediating contaminated soil containing lead and / or zinc. The aforementioned lead- and zinc-tolerant *Gnaphalium affine* SK-5 can rapidly reduce the lead and / or zinc content in water or soil. Specifically, it rapidly (within 90 days) forms a crust on the surface of tailings, reducing lead and / or zinc content, and promotes plant colonization and growth, facilitates plant absorption and translocation of lead and / or zinc, and increases plant biomass and diversity, achieving tailings revegetation and reducing the risk of tailings dust and water erosion.

[0022] 3. This invention improves the heavy metal content and translocation coefficient of the aboveground parts of enriching plants, providing a new approach to promoting the remediation of tailings through plant extraction. It is an innovative, environmentally friendly, and highly promising tailings treatment technology. Attached Figure Description

[0023] Figure 1 This is a flowchart of the purification and screening process for the algal strain in Example 1;

[0024] Figure 2 This is a flowchart of the preferred screening process for the algal strains in Example 1;

[0025] Figure 3Phylogenetic tree of Leptolyngbya sp. SK-5;

[0026] Figure 4 The growth of algal strains (SK-1, SK-3, SK-5, WQ) under low concentrations (1 mg / L, 4 mg / L, 16 mg / L) of Pb stress is shown.

[0027] Figure 5 The growth of algal strains (SK-1, SK-3, SK-5, WQ) under low concentrations (1 mg / L, 4 mg / L, 16 mg / L) of Zn stress is shown.

[0028] Figure 6 Comparison of lead-zinc tailings remediation site conditions between Group C and Group CK; among them... Figure 6 The left image shows a comparison of the SK-5 (Group C) sample plot at 90 days after remediation of lead-zinc tailings with the control group (CK) at 90 days. Figure 6 The right side shows the sample plot conditions of SK-5 (Group C) for remediation of lead-zinc tailings at 10 days and 90 days.

[0029] Figure 7 This is a sample plot of lead-zinc tailings 120 days after sowing sow thistle and beggar-ticks. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the methods used are conventional methods known in the art, and the consumables and reagents used are commercially available. Unless otherwise stated, the technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be applied to the present invention.

[0031] Example 1: Screening of algal strains

[0032] (1) Purification and screening of algae

[0033] The purification and screening process for algal strains is as follows: Figure 1The specific steps are as follows: 10g of naturally grown algal crust from the Shenxiandong lead-zinc tailings mine in Jianshui County, Yunnan Province, was placed in an Erlenmeyer flask containing sterile BG-11 culture medium and cultured in a light incubator for 14 days. Following the dilution plating method, the diluted solution was evenly spread onto the culture medium using a sterile plating stick, with each treatment repeated three times. The sealed BG-11 plates were then placed in a light incubator. When green algae growth was observed on the BG-11 plates, the plates were removed, and each algae strain was streaked using BG-11 culture medium until only one type of algae was observed under a microscope. Sixteen purified algal strains were obtained for subsequent analysis. The light incubator conditions were: temperature 25℃, light-dark cycle 14h:10h.

[0034] (2) Selection and screening of algal strains

[0035] The optimal screening process for algal strains is as follows: Figure 2 Specifically, the high growth rate and biomass of algae are prerequisites for their large-scale application. Extracellular polymers play an important role in the adsorption and removal of heavy metals by algae, and the nitrogen fixation capacity of cyanobacteria can effectively improve soil fertility and promote plant growth. To further optimize the 16 initially screened algal strains, the following tests were conducted: (i) The purified algal strains were streaked into BG-11 culture medium and cultured to the logarithmic growth phase before being transferred to a new culture medium. The initial chlorophyll a content was 2 mg / L, and the chlorophyll a content of the algal solution was measured after 7 days. The preferred culture conditions were: temperature 28℃, light intensity 200 μmol photons / (m²). 2 •s), light-dark cycle 22h:8h, shake well every 8 hours. Chlorophyll a content was determined by ethanol extraction to represent algal biomass. (ii) The algal solution cultured to the end of the logarithmic growth phase was filtered to obtain algal cells. The total EPS of the algal cells was determined by the diphenylamine blue (DBA) method. The algal cells were dried at 80℃ to constant weight and the dry weight of the algal cells was determined to obtain the EPS content of the algal cells. (iii) The purified algal cells were streaked onto BG-11 medium plates without sodium nitrate and the growth of the algal cells was observed after 30 days. The screening results are shown in Table 1. Based on the growth rate, EPS content and nitrogen fixation capacity of the algal cells, 7 algal cells SK-1, 3, 5, 9, 10, 13 and 14 were further selected for subsequent analysis.

[0036] Table 1 Results of optimized screening of purified algal strains

[0037]

[0038]

[0039] (3) Lead and zinc tolerance screening of algal strains

[0040] The lead and zinc tolerance of algal strains is a crucial factor determining their applicability in the remediation of lead- and zinc-contaminated environments. Therefore, the lead and zinc tolerance of seven algal strains was further determined. Algal strains in the logarithmic growth stage were transferred to culture media containing 1 mg / L lead and zinc, respectively, with an initial chlorophyll a content of 2 mg / L. Chlorophyll a content was measured after 7 days (see Table 2). The results showed that algal strains SK-1, 3, and 5 exhibited stronger tolerance to lead and zinc, and 1 mg / L lead and zinc promoted the growth of algal strains SK-3 and SK-5.

[0041] Phylogenetic identification revealed that algal strain SK-1 belongs to the genus *Rhodobacter* (Proteobacteria phylum), while strains SK-3 and SK-5 belong to the genus *Leptolyngbya* (Cyanobacteria phylum). Large-scale culture of the algal strains was conducted using 10L glass bottles and 50L transparent polyethylene containers. Optimal culture conditions included: aeration with an air pump to reduce algal coagulation; dark, non-aerated treatment of the algal solution every 3 days to allow sedimentation; breaking up clumps of algae; and other conditions identical to those used for the selection and culture of the algal strains.

[0042] Table 2 Results of screening for lead and zinc tolerance of algal strains

[0043]

[0044] Example 2: Treatment of lead-zinc wastewater by algal strains

[0045] The red bacteria SK-1, the fine-sheathed algae SK-3 and SK-5 obtained from Example 1, and the sheathed microsheathed algae (WQ) (from the Algal Culture Collection Center of the Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan), which are widely used for artificially inducing crust formation in arid areas, were selected to compare their remediation effects on wastewater contaminated with different concentrations of lead and zinc.

[0046] (1) Algal growth and heavy metal removal in low-concentration lead-zinc wastewater

[0047] Algae can survive and proliferate in lead-zinc wastewater at low concentrations. As their biomass increases, more heavy metals are absorbed and adsorbed by the algae, and the removal of aggregated algae ultimately achieves water remediation. Therefore, algal strains cultured to the logarithmic growth phase were inoculated into lead-zinc wastewater at concentrations of 1, 4, and 16 mg / L, with an initial chlorophyll a content of 2 mg / L. The biomass of the algae and the lead-zinc removal rate were then measured. Changes in algal biomass are shown in [Figure showing changes in biomass]. Figure 4 and Figure 5 , Figure 4 The growth of algal strains (SK-1, SK-3, SK-5, WQ) under low concentrations (1 mg / L, 4 mg / L, 16 mg / L) of Pb stress is shown. Figure 5The growth of algal strains (SK-1, SK-3, SK-5, and WQ) under low concentrations (1 mg / L, 4 mg / L, and 16 mg / L) of Zn stress is shown in Table 3. The biomass of the algal strains and the removal rates of lead and zinc in the wastewater 10 days after inoculation are also presented. The results indicate that *Gnaphalium spp.* SK-5 exhibited significantly higher biomass (1.04-20.6 times) in low-concentration lead-zinc wastewater compared to other strains, with a biomass increase of 1.8-6.6 times after 10 days. This was particularly evident in higher concentrations (16 mg / L) of zinc-containing wastewater, where the biomass was 1.2-27 times that of other strains. *Gnaphalium spp.* SK-5 also demonstrated superior removal of lead and zinc compared to other strains, achieving removal rates of 99.2% and 99.5% of lead and zinc, respectively, at a concentration of 16 mg / L. This is attributed to the high biomass and EPS content of this algal strain.

[0048] Table 3 Results of algal growth and heavy metal removal in low-concentration lead-zinc wastewater (10 days)

[0049]

[0050] (2) Adsorption and removal of high-concentration lead-zinc wastewater by algae

[0051] Algae growth is inhibited or even impossible in high-concentration lead-zinc wastewater, but algae, especially EPS (excessive peroxidase), can rapidly adsorb and remove heavy metals. Algal strains cultured to the stable phase were inoculated into lead-zinc wastewater with concentrations of 50 and 100 mg / L, with an initial chlorophyll a content of 20 mg / L. Lead-zinc removal rates were measured after 2 hours. As shown in Table 4, algal strain SK-3 achieved removal rates of 97.5% and 95.2% for 50 mg / L lead-zinc, and 84.2% and 88.1% for 100 mg / L lead-zinc, respectively, which is significantly higher than other algal strains.

[0052] Based on the above screening results, *Leptolyngbya* sp. SK-5 (lead-zinc tolerant *Leptolyngbya* sp. SK-5) exhibits rapid growth, large biomass, high EPS content and nitrogen fixation capacity, and good tolerance and removal effect on lead and zinc. It can be considered an ideal algal strain for the ecological remediation of lead-zinc polluted water and soil. The 16S rDNA sequence of *Leptolyngbya* sp. SK-5 (lead-zinc tolerant *Leptolyngbya* sp. SK-5) is shown in SEQ ID NO.1. This strain was deposited at the China Center for Type Culture Collection (Wuhan) on June 9, 2023, with accession number CCTCC NO: M 2023971. The phylogenetic tree of *Leptolyngbya* sp. SK-5 (lead-zinc tolerant *Leptolyngbya* sp. SK-5) is shown below. Figure 3 As shown.

[0053] Table 4 Results of Algal Adsorption and Removal of High Concentrations of Lead and Zinc in Water (1 h)

[0054]

[0055] Example 3: Restoration of lead-zinc tailings ecology using *Synystoma SK-5*

[0056] (1) Plot overview and experimental setup

[0057] From July to September 2022, an on-site remediation experiment was conducted at the Shenxiandong lead-zinc tailings dam in Jianshui County, Honghe Prefecture, Yunnan Province (23°34′2″N, 102°52′16″, altitude 1461.2m). The Shenxiandong tailings dam is located in the subtropical plateau monsoon climate of South Asia. The dam contains lead-zinc ore sand with lead and zinc concentrations between 4000-5000 mg / kg.

[0058] Four 1m × 1m quadrats were selected at flat locations within the tailings dam for each treatment. 10L of water was sprayed to bring the moisture content of each quadrat to approximately 20% to reduce algal loss from subsequent inoculation. The experimental group (Cyanobacteria inoculation group, group C) was sprayed with 15L of stable-phase (approximately 150mg / L) *Cyanobacteria SK-5* algal solution (lead-zinc tolerant *Cyanobacteria SK-5*), while the control group (CK group) received no additional materials. Ten days after inoculation, each quadrat was supplemented with 200mL of BG-11 culture medium and 5L of water daily in the evening. During the experimental period, the quadrat was covered 30cm above the quadrat with a shade net to ensure suitable temperature, humidity, and light conditions for the growth of *Cyanobacteria SK-5*. After sample collection, the surface crust was separated for determining the chlorophyll a content of *Cyanobacteria SK-5*, and the remaining samples were used to determine soil properties.

[0059] (2) Growth of *Spiritia spp.* SK-5

[0060] The chlorophyll a content of *Syngonium SK-5* scabies chlorophyll a was measured in the sample plots at days 0, 10, 45, and 90 after inoculation (ethanol extraction method, see Table 5). The plot conditions at day 90 are shown in [Table 5]. Figure 6 . Figure 6 The image on the left shows a comparison of the plot conditions of SK-5 (lead-zinc tolerant algae SK-5) (Group C) after 90 days of remediation of lead-zinc tailings with the control group (CK) after 90 days. Figure 6The right side shows the plot conditions of SK-5 (Group C) after 10 and 90 days of remediation of lead-zinc tailings. As can be seen from the figure, after supplementing water and nutrients and providing suitable environmental conditions, the chlorophyll a content in Group CK was extremely low, and no visible organisms appeared, indicating that the establishment of biocrusts in tailings soil under natural conditions is extremely slow. *Gnaphalium spp.* SK-5 (lead-zinc tolerant *Gnaphalium spp.* SK-5) was able to adapt to the tailings environment and form obvious biocrusts after inoculation. Its biomass increased by 14.1% and 21.7% at 45 and 90 days after inoculation, respectively, indicating that *Gnaphalium spp.* SK-5 inoculation can significantly accelerate crust formation.

[0061] Table 5. Chlorophyll a content of CK group and C group on days 0, 10, 45 and 90.

[0062]

[0063] (3) Improvement of tailings soil properties

[0064] Ninety days after inoculation, the soil properties of the tailings were determined (Table 6). Available lead and zinc were determined by DTPA extraction-atomic flame absorption spectrometry; total organic carbon was determined by potassium dichromate oxidation method; ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen content in the leachate were determined after potassium chloride extraction; and available phosphorus content was determined by molybdenum sulfate antimony colorimetric method. Inoculation with *Gnaphalium spp. SK-5 (lead-zinc tolerant *Gnaphalium spp. SK-5*) reduced the soil's available lead content by 19.3% and available zinc content by 11.3%.

[0065] Tailings are extremely nutrient-poor, but inoculation with *Synostemma pentaphyllum* SK-5 effectively increases soil nutrients, including key plant growth elements such as carbon, nitrogen, and phosphorus. The normally dead *Synostemma pentaphyllum* SK-5 algae and their metabolites can increase the total organic carbon content of the soil and enhance soil microbial activity. *Synostemma pentaphyllum* SK-5 is one of the most important nitrogen-fixing organisms, and it has a significant effect on improving the content of the three types of inorganic nitrogen, especially ammonia nitrogen and nitrate nitrogen. The reduction in heavy metal content and the increase in soil carbon and nitrogen can significantly enhance soil microbial activity, including microorganisms capable of phosphorus solubilization, thereby increasing the available phosphorus content in the soil.

[0066] Table 6. Changes in soil properties 90 days after lead-zinc tailings inoculation.

[0067]

[0068] Example 4: Enhancing Plant Extraction with *Phyllostachys SK-5* (Lead-Zinc Tolerant *Phyllostachys SK-5*)

[0069] (1) Experimental setup

[0070] Plant extraction removes heavy metals by absorbing them from the plants and harvesting the plants. Sow thistle and Bidens trifoliata, with their rapid growth rate, high biomass, and strong lead and zinc absorption capacity, are widely studied plant extract species and were also the dominant species at the experimental site (Shenxiandong tailings mine, Jianshui County). Plant debris (containing a large amount of seed stock) from the Sow thistle and Bidens trifoliata communities was collected from the tailings slope, mixed in a 1:1 weight ratio, and crushed to obtain inoculation debris. Based on Example 2, 90 days after inoculation with *Gnaphalium spp.* (lead- and zinc-tolerant *Gnaphalium spp.*), 0.5 kg of debris was evenly sown in each plot. Post-sowing care is described in Example 3.

[0071] (2) Plant growth

[0072] At 10, 60, and 120 days after sowing the waste, the number of plants, leaf cover, and plant height in the plots were recorded visually. The results are shown in Table 7. The plot conditions at 120 days are also shown in Table 7. Figure 7 From Table 7 and Figure 7 It was found that 60 days after sowing, the number of plants and leaf cover in group C (inoculated with *Synostemma pentaphyllum* SK-5) were 3.14 and 4.74 times that of group CK (control group), respectively. 120 days after sowing, the number of plants and leaf cover were 4.13 and 8.93 times, respectively. Inoculation with *Synostemma pentaphyllum* SK-5 significantly reduced soil heavy metal availability, improved soil nutrition (Example 2), and improved soil structure, water and fertilizer retention capacity, and increased soil microbial and enzyme activity, all of which provided favorable conditions for subsequent plant establishment. Fertilizer application can improve soil fertility in the short term, but nutrient content will decrease over time. The crust formed by *Synostemma pentaphyllum* SK-5 can continuously provide essential elements such as carbon, nitrogen, and phosphorus to the tailings soil, forming a complete nutrient cycle. The difference in leaf cover between group C and group CK reached its peak 120 days after sowing, possibly because group C could continuously supply nutrients, while the initial nutrient solution supplemented to group CK was almost exhausted.

[0073] Table 7 Plant growth after spreading withering materials

[0074]

[0075] (3) Absorption and transport of heavy metals in plants

[0076] Dominant species *Sonchus oleraceus* and *Bidens trifoliata* were selected from the sample plots. The heavy metal content in the aboveground and underground parts of the plants was determined by aqua regia reflux digestion-atomic absorption spectrometry, and the translocation coefficients were calculated. The results are shown in Table 8. The table shows that the lead content in the aboveground parts of *Sonchus oleraceus* and *Bidens trifoliata* in group C increased by 195% and 266% respectively compared to the control group (CK), while the zinc content in the aboveground parts of *Bidens trifoliata* increased by 79% compared to the CK group. The crust formation of *Syngonium stenoptera* SK-5 increased the absorption of heavy metals by the aboveground parts of the plants, especially lead. The translocation coefficients of heavy metals by plants were consistent with the heavy metal content in the aboveground parts. The translocation coefficients of lead in *Sonchus oleraceus* and *Bidens trifoliata* in group C increased by 124% and 521% respectively compared to the CK group, while the zinc content in the aboveground parts of *Bidens trifoliata* increased by 91% compared to the CK group.

[0077] Phytoremediation involves the absorption and accumulation of heavy metals by plants, followed by harvesting the plants to remove heavy metals from tailings. Sow thistle and Bidens trifoliata, with their high growth rates and biomass, high heavy metal absorption capacity, and high translocation coefficients, are ideal species for phytoremediation. Inoculation with *Hymenopterus xanthipes* SK-5 effectively promoted plant growth and the absorption of heavy metals, especially by the aboveground parts, significantly improving the removal efficiency of lead.

[0078] Table 8 Effects of *Spiritiformis* SK-5 inoculation on heavy metal uptake and transport in plants.

[0079]

[0080] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention, all of which should be included within the protection scope of the present invention.

Claims

1. A lead- and zinc-tolerant herbaceous algae SK-5, characterized in that, Lead- and zinc tolerant fine-sheathed filamentous algae SK-5 ( Leptolyngbya sp. SK-5 was deposited at the China Center for Type Culture Collection on June 9, 2023. The accession number is CCTCC NO: M 2023971.

2. The application of the lead- and zinc-tolerant herbaceous algae SK-5 as described in claim 1 in the purification of lead and / or zinc in polluted water.

3. The application according to claim 2, characterized in that, The polluted water contains lead and zinc, with concentrations of both less than 100 mg / L.

4. The application of the lead- and zinc-tolerant herbarium SK-5 as described in claim 1 in the remediation of soils contaminated with lead and / or zinc.

5. The application according to claim 4, characterized in that, The contaminated soil contained lead and zinc, with concentrations of 4000-5000 mg / kg for both.

6. A method for remediating contaminated soil containing lead and / or zinc, characterized in that, Includes the following steps: Step 1): Spray the lead-zinc tolerant fine-sheathed filamentous algae SK-5 as described in claim 1 into the contaminated soil; Step 2): Add culture medium and water to the contaminated soil, and set up a shade net on the contaminated soil.

7. The method for remediating lead- and / or zinc-contaminated soil according to claim 6, characterized in that, Following step 2), step 3) is also included: spreading plant debris on the contaminated soil.

8. The method for remediating contaminated soil containing lead and / or zinc according to claim 6, characterized in that, In step 1), the lead-zinc tolerant hernia SK-5 is in a stable phase; in step 2), the culture medium is BG-11 culture medium.

9. The method for remediating contaminated soil containing lead and / or zinc according to claim 7, characterized in that, In step 3), the plant droplets are selected from at least one of sow thistle droplets and Bidens trifoliata droplets, and the sowing density of the plant droplets is 0.48-0.52 kg / m². 2 .

10. The application of the lead- and zinc-tolerant fine-sheathed filamentous algae SK-5 of claim 1 in promoting the establishment, growth, absorption and translocation of lead and / or zinc in contaminated soil containing lead and / or zinc, wherein the plant is sow thistle or beggar-ticks.

Images