Multifunctional physical-biological combined method for blocking heavy metals

Abstract

The application discloses a kind of multi-functional plant physics-biological combined heavy metal blocking method, belong to combined heavy metal blocking method technical field, screening and cultivating multi-functional plant, the multi-functional plant includes water and soil conservation type plant and heavy metal hyperaccumulation plant, karst hillside is divided into pass, waist and slope foot according to landform feature three regions, and according to the slope of each region, soil condition, soil erosion and heavy metal distribution characteristics configuration multi-functional plant, the joint blocking of physical interception and biological absorption of heavy metal is realized by the multi-functional plant of configuration, wherein, water and soil conservation type plant is held soil and intercepts silt and attached heavy metal by root system formation net structure, hyperaccumulation plant absorbs heavy metal in soil and soil water, the heavy metal content in slope soil and soil water is monitored, and dynamically optimizes plant configuration and planting parameters according to monitoring result.

Description

Technical Field

[0001] This invention relates to the field of soil heavy metal pollution control and ecological restoration technology, and in particular to a multifunctional plant physical-biological combined blocking method for soil erosion and heavy metal migration in karst slopes. Background Technology

[0002] Due to complex terrain, thin soil, and severe soil erosion, sloping farmland in karst regions is prone to the migration of high background levels of heavy metals (such as cadmium, lead, and zinc) from the soil, polluting downstream water bodies and valley soils, threatening the ecological environment and agricultural product safety. Existing remediation methods include chemical passivation, phytoremediation, and engineering interception, but single technologies are insufficient to simultaneously address soil and water conservation and heavy metal control, and there is a lack of technological integration tailored to the unique environment of karst slopes. Developing multifunctional phytoblockance technologies that combine physical interception and biosorption is of great significance for controlling heavy metal migration and protecting the ecological environment. Therefore, a multifunctional phytophysio-biological combined heavy metal blocking method is designed to address the above problems. Summary of the Invention

[0003] The main objective of this invention is to provide a multifunctional plant-based physical-biological method for blocking heavy metals. By screening plants with soil and water conservation and heavy metal accumulation functions, and combining them with geomorphological zoning and dynamic monitoring optimization, a dual blocking mechanism of physical interception and biological absorption of heavy metals can be achieved.

[0004] A multifunctional plant-based physical-biological combined method for blocking heavy metals includes the following steps: Step 1: Screen and cultivate multifunctional plants that have both soil and water conservation functions and heavy metal enrichment functions. The multifunctional plants include soil and water conservation plants and heavy metal hyperaccumulators. Step 2: Divide the karst slope into three areas according to its geomorphological features: pass, hillside, and foot of the slope. Based on the slope, soil conditions, degree of soil erosion, and heavy metal distribution characteristics of each area, configure the multifunctional plants described in Step 1 to form a blocking system that combines physical interception and biological absorption. Step 3: Monitor the heavy metal content in the soil and soil water of the slope, and dynamically optimize the plant configuration and planting parameters based on the monitoring results.

[0005] Preferably, the soil and water conservation plants mentioned in step one are selected from at least one of Napier grass, vetiver grass, and bahia grass; the monitoring results of heavy metal content in slope soil and soil water in step three are used to determine the excessive heavy metal elements that need to be treated; based on the monitoring results, plants with high enrichment capacity for the identified target heavy metals are selected from centipede grass, southeastern sedum, and ageratum (they can be selected individually or in combination) to achieve targeted enrichment and blocking of the heavy metal.

[0006] Preferably, the criteria for dividing the three areas in step two are: a slope of 25-30° and a soil thickness of 20-30cm in the mountain pass area; The slope of the hillside area is 15-25° and the soil thickness is 30-50cm. The slope at the foot of the slope is 5-10°, which is a slightly eroded and deposited area.

[0007] The preferred method for plant configuration in step two is as follows: Water and soil conservation plants were planted in the mountain pass area to form a 1.5m wide plant protection belt; In the hillside area, soil and water conservation plants and heavy metal hyperaccumulators are intercropped in a 1:1 ratio; in the foot of the slope area, heavy metal hyperaccumulators are densely planted.

[0008] Preferably, the cultivation method in step one includes: Seeds were soaked in a nutrient solution with a nitrogen, phosphorus, and potassium ratio of 2:1:1 for 24 hours. Add EDTA or citric acid chelating agents to the planting soil; When the soil pH is <5.5, apply 6 t / ha of lime.

[0009] Preferably, the planting mode in step two is selected from at least one of contour planting strips, composite plant hedges, and high-density restoration patches, wherein the composite plant hedge adopts a structure of dense planting at the front, enrichment in the middle layer, and protection at the top layer.

[0010] Preferably, in step three, an XRF analyzer is used to monitor the heavy metal content, and the heavy metal migration rate is calculated using a Python-based real-time data processing module.

[0011] Preferably, when the heavy metal migration rate is >20%, the planting ratio of heavy metal hyperaccumulating plants is increased from the initial 50% to 70%.

[0012] Preferably, the total amount of heavy metals blocked is calculated using the following formula: ; in, ; n is the total number of different plant species i that are mixed-planted for soil and water conservation and heavy metal blocking; The proportion of the planting area for plant i; This represents the annual soil erosion when there is no vegetation. Cs represents the average concentration of heavy metals in the soil. The soil and water conservation capacity coefficient of plant i; B i Let i be the annual biomass of plant i; The concentration of heavy metals accumulated in the aboveground parts of plant i.

[0013] Preferably, the process also includes plant harvesting and disposal steps: regularly harvesting the above-ground parts of plants that are hyperaccumulating heavy metals and disposing of them through centralized incineration or resource utilization to avoid secondary pollution.

[0014] Beneficial technical effects of the present invention: This invention provides a multifunctional plant-based physical-biological combined method for blocking heavy metals, overcoming the limitations of single technologies and achieving a synergistic effect of "interception-absorption" dual blocking. Traditional remediation methods often only address localized heavy metal pollution, failing to effectively control the spread of pollutants caused by soil erosion, and unable to simultaneously purify and remove heavy metals from the soil. This invention innovatively combines and spatially optimizes the configuration of soil and water conservation plants with hyperaccumulating plants, constructing a complete integrated prevention and control technology system for heavy metal pollution on slopes.

[0015] Specifically, the advantages of this invention are reflected in the following four aspects: This invention innovatively combines soil and water conservation plants such as Napier grass with hyperaccumulating plants such as Centipede Grass and Sedum aizoon, forming a dual-blocking system of "physical barrier + biological purification." Napier grass hedges, through their extensive root system forming a dense network structure, effectively intercept sediment particles and their attached heavy metals, increasing the heavy metal deposition rate on slopes by over 70%, thus controlling the spread of heavy metals caused by soil erosion at its source. Simultaneously, hyperaccumulating plants actively remove heavy metals from the soil and soil water through biological absorption. This synergistic system can reduce the total cadmium migration by over 60%, achieving a treatment effect far exceeding any single technology.

[0016] To address the challenges of complex karst topography (slope 5-30°), uneven soil thickness (20-50cm), and significant differences in heavy metal migration patterns, this invention proposes a scientific geomorphological zoning planting strategy. In the mountain pass area (slope 25-30°), a 1.5m wide protective belt of *Pennisetum alopecuroides* is planted, intercepting over 75% of sediment and significantly reducing the annual sediment loss from 45t / ha to 12t / ha. Based on a soil heavy metal content of 6 mg / kg, this is equivalent to blocking 198g / ha of heavy metal migration. In the hillside area (slope 15-25°), a 1:1 intercropping pattern of *Pennisetum alopecuroides* hedges and *Ageratum conyzoides* is used, combining interception and absorption functions to reduce cadmium migration by 65%. In the foothill sedimentary area (cadmium content 4-8 mg / kg), dense planting of hyperaccumulating plants can significantly reduce the soil cadmium concentration from 5.2 mg / kg to 4.9 mg / kg within one year. This zoning strategy fully considers the environmental characteristics and pollution risks of different slopes, avoids the inefficiency of "one-size-fits-all" treatment, and makes the blocking effect more stable and reliable.

[0017] The plant-based technology employed in this invention boasts significant advantages such as low cost, environmental friendliness, and no secondary pollution. Compared to engineering measures, it eliminates the need for large-scale earthwork, significantly reducing construction and maintenance costs. Compared to chemical passivation technology, it eliminates the risk of secondary pollution and simultaneously achieves the dual functions of soil and water conservation and soil remediation. Furthermore, this technology offers multiple ecological benefits, including improving soil structure, increasing organic matter, and restoring biodiversity, thus achieving a balance between environmental and economic benefits.

[0018] 4. Dynamically Adjustable Precision Governance Model This invention establishes a dynamic control mechanism based on real-time monitoring. By periodically monitoring the heavy metal content in soil and water, and using a data analysis platform to calculate the heavy metal migration rate, the system automatically adjusts the multifunctional plant configuration scheme when the cadmium migration rate exceeds 20%, such as increasing the planting ratio of Ageratum conyzoides from 50% to 70%. This closed-loop management approach of "monitoring-evaluation-control" ensures that the remediation system can automatically optimize operating parameters according to environmental changes and remediation progress, greatly improving the accuracy and long-term effectiveness of the remediation efforts.

[0019] In summary, this invention, through the organic combination of a dual-blocking mechanism, a zoned configuration strategy, a balance between ecological and economic considerations, and a dynamic regulation system, forms a complete, efficient, and stable solution for the treatment of heavy metal pollution on slopes, providing reliable technical support for the prevention and control of heavy metal pollution in karst areas. Attached Figure Description

[0020] Figure 1 This is a system flowchart of a preferred embodiment of a multifunctional plant physical-biological combined method for blocking heavy metals according to the present invention.

[0021] Figure 2 This is a schematic diagram of the plant protection strip layout according to a preferred embodiment of a multifunctional plant physical-biological combined method for blocking heavy metals according to the present invention.

[0022] Figure 3 This is a flowchart of a preferred embodiment of a multifunctional plant physical-biological combined blocking method for heavy metals according to the present invention. Detailed Implementation

[0023] To enable those skilled in the art to understand the technical solution of the present invention more clearly, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0024] The process includes the following steps: Multifunctional plant screening and cultivation: Screening for soil and water conservation plants with well-developed root systems and strong erosion resistance (such as Napier grass and vetiver) and heavy metal hyperaccumulators (such as centipede grass, Ageratum conyzoides, and Sedum aizoon).

[0025] The soil and water conservation effect after planting vegetation is as follows: Equation (1); Soil loss after planting: Equation (2); Therefore, the reduction in soil erosion is: Equation (3); The reduction in heavy metal content in the soil (assuming an average soil heavy metal concentration of Cs mg / kg) is the water and soil conservation blocking amount: Equation (1); In formula (1), η represents the overall soil and water conservation effect, which is related to the types and proportions of plants; n represents the total number of different plant species planted together for soil and water conservation and heavy metal blocking; x i : The proportion of plant area of ​​plant i (∑x i =1), dimensionless; Pwsc,i is the soil and water conservation capacity coefficient of plant i, (0-1), dimensionless; in formula (2), S0 is the annual soil loss when there is no vegetation. (t / ha); S The soil loss after planting (t / ha); in equation (3), ΔS is the reduced soil loss (t / ha); in equation (4), Bwsc The amount of heavy metals blocked by soil erosion by soil-conserving plants (mg / ha); Cs is the average concentration of heavy metals in the soil (mg / kg).

[0026] Annual heavy metal absorption per unit area of ​​plants: Equation (5); Among them: B i : Annual biomass of plant i (t / ha); The concentration of heavy metals in the aboveground parts of plant i (mg / kg) is then considered; therefore, the total bioblocking capacity is: Equation (6); Cultivation method: Soak seeds in nutrient solution (containing nitrogen, phosphorus and potassium in a ratio of 2:1:1) for 24 hours to increase the germination rate to over 90%.

[0027] By adding chelating agents such as EDTA and citric acid, the absorption of cadmium by Sedum aizoon was increased by 140%.

[0028] When the soil pH is less than 5.5, applying lime (6 t / ha) can increase the absorption efficiency of centipede grass by 15-20%.

[0029] b. Geomorphological zoning and vegetation configuration: The karst slope is divided into three areas according to geomorphological characteristics: mountain pass, hillside and foot of slope. The multifunctional plants are configured according to the slope, soil conditions, soil erosion and heavy metal distribution characteristics of each area. Pass: slope 25-30°, soil thickness 20-30cm, water flow velocity 0.5-1m / s; Mountainside: Slope 15-25°, soil thickness 30-50cm, severe silt erosion; Toe of the slope: Slope of 5-10°, a zone of slight erosion and deposition.

[0030] Optimization measures: Adjust irrigation frequency (1-2 times per week) according to soil moisture content (target 20-30%).

[0031] Based on the probability of local rainfall intensity (>50mm / d is considered high intensity), increase the planting density of Napier grass (reduce plant spacing to 15cm).

[0032] Appendix Figure 2 ( Figure 2 ): A schematic diagram of the layout of the vegetation protection zone, indicating the types and densities of plants at the mountain pass, hillside, and foot of the slope.

[0033] Appendix Figure 3 ( Figure 3 ( ): A flowchart of a combined physical-biological blocking process, including planting, interception, absorption, harvesting, and regulation steps.

[0034] The XRF analyzer was used to monitor the heavy metal content in soil and multifunctional plants; the heavy metal migration rate was calculated using a Python-based real-time data processing module; and the plant configuration and planting parameters were dynamically optimized based on the monitoring results.

[0035] Let the total amount of heavy metal blockage per unit area in the previous year be... It consists of two parts: Equation (7); Equation (8); Combine summation terms: Equation (9); make: Equation (10); but: Equation (11); Maximize the total amount of heavy metals blocked; Equation (12); Constraints: Equation (13); Solution: Since it is a linear function, the optimal solution is to choose Z.i The largest plant, let it be x i =1, the rest are 0.

[0036] If mixed planting is required, please follow Z. i Size allocation for multifunctional plant planting ratios.

[0037] By selecting specific multifunctional plants, optimizing planting zones in karst slope topography, and integrating physical-biological combined blocking processes, we can achieve efficient control of heavy metal migration and soil remediation.

[0038] The synergistic effect of plant protection strips and hyperaccumulating plants achieves a seamless integration of physical interception and biological absorption. Highly efficient blocking: Through a combined physical-biological mechanism, the proportion of heavy metals migrating with soil and water loss is significantly reduced (experimental data show that cadmium migration is reduced by more than 60%).

[0039] An experiment was conducted on a 100㎡ slope in Hechi City, Guangxi Province, with a slope of 20°. The cadmium content in the soil was 5.2 mg / kg, which exceeds the standard for risk control of soil pollution in agricultural land (GB15618-2018) by approximately three times. Soil volume: 1.3 g / cm³ (1300 t / ha·20cm); topsoil weight (calculated at 20cm): 2600 t / ha; initial soil erosion modulus: approximately 45 t / (ha·year) (no vegetation cover).

[0040] Multifunctional plant screening and cultivation; Plant species selection: Soil and water conservation type (physical interception): Pennisetum purpureum, root depth 50-80cm, formation density 0.5–1kg / m³ 3 Its mesh structure has strong erosion resistance and a sediment interception rate of 75% (after 12 months, the sediment loss decreased from 45t / ha to 12t / ha). Hyperaccumulating plants: Ageratum conyzoides (cadmium enrichment coefficient 6-20) and Sedumalfredii (cadmium enrichment coefficient 10-80). Plant harvesting and safe disposal: The above-ground parts should be centrally incinerated or utilized for resource recovery to avoid secondary pollution.

[0041] Appendix Figure 1 ( Figure 1 ): A multifunctional plant screening flowchart that includes steps for seed screening, nutrient regulation, field trials, and enrichment coefficient determination.

[0042] Topographic zoning and vegetation configuration; Pass: Plant Napier grass with a row spacing of 30cm and a plant spacing of 20cm to form a 1.5m wide plant protection belt with a sediment interception rate of ≥70%; On the hillside: intercropping Napier grass and Ageratum conyzoides in a 1:1 ratio with a row spacing of 40cm achieves synergistic interception and absorption, reducing cadmium migration by ≥65%; At the foot of the slope: densely plant Ageratum conyzoides and Sedum sarmentosum, with a plant spacing of 15cm.

[0043] Optimization strategy: When the cadmium migration rate is >20%, increase the proportion of Sedum aizoon and Ageratum praecox (e.g., from 50% to 70%).

[0044] Table 1. Annual cumulative dry weight, cadmium content and annual cadmium removal of hyperaccumulating plants;

[0045] Cadmium loss reduced due to soil and water conservation; Erosion reduction: (45→10).

[0046] Corresponding reduction in cadmium loss: .

[0047] Total annual cadmium blocking amount; .

[0048] Total cadmium content in the topsoil; .

[0049] Annual concentration decrease rate; .

[0050] Soil cadmium concentration two years later (conservatively decreasing). First year: .

[0051] Second year (considering a slight decrease in absorption efficiency, a 5% reduction is taken): .

[0052] Cumulative decline: approximately 11% (from Down to ).

[0053] Governance effectiveness; Soil erosion: erosion modulus from Reduce to ,reduce Soil erosion.

[0054] Cadmium blocking: Approximately [amount missing] cadmium is blocked annually through vegetation absorption and erosion reduction. Cadmium accounts for approximately 5.8% of the total cadmium in the topsoil.

[0055] Soil cadmium concentration: decreased after two years The cumulative reduction is approximately 11%.

[0056] Ecological benefits: Soil and water conservation plants form a stable root network to prevent slope collapse; hyperaccumulating plants enable controlled harvesting and centralized treatment of cadmium, reducing the risk of secondary pollution.

[0057] A zoned planting strategy tailored to the landform characteristics of karst slopes improves technological adaptability and governance efficiency. Highly adaptable to various landforms: The zoned planting strategy optimizes the configuration for the complex terrain of karst slopes, enhancing the stability and targeted effectiveness of the barrier effect.

[0058] The dynamic control mechanism ensures the stability of the technology under different environmental conditions.

[0059] Low cost and eco-friendly: Compared to engineering measures, plant-based technology does not require large-scale earthwork, has low maintenance costs, and combines ecological restoration and landscape value.

[0060] Short treatment cycle: The synergistic effect of multifunctional plants increases the overall absorption efficiency by more than 30%, shortening the treatment cycle.

[0061] Highly scalable: The technical solution is simple to operate and applicable to sloping farmland in other karst regions, with broad application prospects.

[0062] Replacing plant species with other plants with well-developed root systems (such as alfalfa) or hyperaccumulating plants (such as Sedum aizoon) can also achieve physical-biological blocking, but the planting density and intercropping ratio need to be re-optimized.

[0063] Introducing small ecological filters (such as bamboo interception nets) to assist plant protection strips in physical blocking can enhance the effect of sediment interception, but may increase initial investment costs.

[0064] The microbial-plant co-remediation technology enhances plant absorption efficiency by adding heavy metal adsorbing bacteria (such as Bacillus subtilis), but additional control of the survival conditions of the microbial community is required.

[0065] The above description is merely a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A multifunctional plant-based physical-biological combined method for blocking heavy metals, characterized in that: Includes the following steps: Step 1: Screen and cultivate multifunctional plants that have both soil and water conservation functions and heavy metal enrichment functions. The multifunctional plants include soil and water conservation plants and heavy metal hyperaccumulators. Step 2: Divide the karst slope into three areas according to its geomorphological features: pass, hillside, and foot of the slope. Based on the slope, soil conditions, degree of soil erosion, and heavy metal distribution characteristics of each area, configure the multifunctional plants described in Step 1 to form a blocking system that combines physical interception and biological absorption. Step 3: Monitor the heavy metal content in the soil and soil water of the slope, and dynamically optimize the plant configuration and planting parameters based on the monitoring results; The soil and water conservation plants mentioned in step one are selected from at least one of Napier grass, vetiver grass, and bahia grass; the monitoring results of heavy metal content in slope soil and soil water in step three are used to determine the excessive heavy metal elements that need to be treated; based on the monitoring results, plants with high enrichment capacity for the identified target heavy metals are selected from centipede grass, southeastern sedum, and ageratum to achieve targeted enrichment and blocking of the heavy metals. The criteria for dividing the three areas mentioned in step two are: the slope of the mountain pass area is 25-30° and the soil thickness is 20-30cm; The slope of the hillside area is 15-25° and the soil thickness is 30-50cm. The slope at the foot of the slope is 5-10°, which is a zone of slight erosion and deposition; The configuration of multifunctional plants in step two is selected from at least one of contour planting strips, composite plant hedges, and high-density restoration patches. The composite plant hedges adopt a structure of dense planting at the front, enrichment in the middle layer, and protection at the top layer. In step three, an XRF analyzer is used to monitor the heavy metal content, and the heavy metal migration rate is calculated using a Python-based real-time data processing module. When the heavy metal migration rate is >20%, increase the planting ratio of heavy metal hyperaccumulating plants from the initial 50% to 70%; The total amount of heavy metals blocked is calculated using the formula: ； in, ; n is the total number of different plant species i that are mixed-planted for soil and water conservation and heavy metal blocking; The proportion of the planting area for plant i; This represents the annual soil erosion when there is no vegetation. Cs represents the average concentration of heavy metals in the soil. The soil and water conservation capacity coefficient of plant i; B i Let i be the annual biomass of plant i; The concentration of heavy metals accumulated in the aboveground parts of plant i.

2. The multifunctional plant physical-biological combined method for blocking heavy metals according to claim 1, characterized in that: The plant arrangement method for step two is as follows: Water and soil conservation plants were planted in the mountain pass area to form a 1.5m wide plant protection belt; In the hillside area, soil and water conservation plants and heavy metal hyperaccumulators are intercropped in a 1:1 ratio; in the foot of the slope area, heavy metal hyperaccumulators are densely planted.

3. The multifunctional plant physical-biological combined method for blocking heavy metals according to claim 1, characterized in that: The cultivation methods in step one include: Seeds were soaked in a nutrient solution with a nitrogen, phosphorus, and potassium ratio of 2:1:1 for 24 hours. Add EDTA or citric acid chelating agents to the planting soil; When the soil pH is <5.5, apply 6 t / ha of lime.

4. The multifunctional plant physical-biological combined method for blocking heavy metals according to claim 1, characterized in that: It also includes plant harvesting and disposal steps: regularly harvesting the above-ground parts of plants that are hyperaccumulating heavy metals and disposing of them through centralized incineration or resource utilization to avoid secondary pollution.

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