Tree species screening method for remediation of heavy metal lead contaminated soil
By screening and evaluating the accumulation and translocation capacity of lead in greening tree species, the problem of the difficulty in completely removing lead pollution in soil using existing technologies has been solved, achieving efficient and low-cost remediation while protecting the soil environment.
Patent Information
- Application Number
- CN202510978649.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-16
- Publication Date
- 2025-11-25
AI Technical Summary
Existing technologies are insufficient to completely remove lead pollution from soil using simple physical or chemical methods, and these methods also involve resource consumption or secondary pollution.
A tree species screening method was adopted, which selected the best tree species for remediation of heavy metal lead-contaminated soil by selecting greening plants with high efficiency, low cost and environmental friendliness, and using a comprehensive evaluation of enrichment and translocation capabilities.
It achieves efficient and low-cost remediation of lead-contaminated soil, avoiding resource consumption and secondary pollution. Green plants can also beautify the environment and protect soil structure.
Smart Images
Figure CN121008007A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ecological remediation technology for heavy metal lead pollution, and in particular to a method for selecting tree species for the remediation of soil contaminated with heavy metal lead. Background Technology
[0002] With the rapid development of urbanization and industrialization, vehicle exhaust emissions have become a serious source of pollution, and transportation is currently one of the main sources of heavy metal pollution in urban soil. Vehicle exhaust emissions and tire wear generate large amounts of heavy metals, which diffuse through the atmosphere and soil, causing soil heavy metal pollution. Soil heavy metals are characterized by their insidious, long-term, cumulative, and irreversible nature, posing a significant and serious potential threat to human safety and becoming an urgent social problem to solve. Currently, the main methods for treating heavy metal pollution are physical remediation and chemical remediation. Physical methods consume a lot of resources, while chemical methods are prone to secondary pollution and damage to the soil's physicochemical properties. Furthermore, heavy metals in soil are often distributed in a vertical gradient, making it difficult to achieve complete removal through simple physical or chemical methods. To address these shortcomings, phytoremediation technology, which boasts advantages such as high efficiency, low cost, and environmental friendliness, has been proposed. This technology utilizes green plants to absorb, accumulate, and transform different heavy metals to effectively treat soil heavy metal pollution. In the process of urban greening, selecting dominant green plants is of great significance for the treatment of soil heavy metal pollution. Summary of the Invention
[0003] Technical problem to be solved: The technical problem to be solved by this application is that the indicator system is too simple and it is difficult to achieve complete removal through simple physical or chemical methods. The application provides a tree species screening method for the remediation of heavy metal lead-contaminated soil, which has the advantages of high efficiency, low cost and environmental friendliness.
[0004] Technical solution:
[0005] To solve the above-mentioned technical problems, the technical solution adopted in this application is as follows:
[0006] Step 1, Sample Selection: Determine the species, soil parameters, and tree parameters of several test tree samples;
[0007] Step 2, leaf sampling: Collect 10 leaves from each plant in the four directions of east, south, west and north.
[0008] Step 3, soil sampling: Randomly collect bare soil and soil samples from the root system of each plant in the test area. Mix the samples on-site to form a mixed sample, put it into a special sampling bag, number it and bring it back to the laboratory.
[0009] Step 4, Sample processing and lead content determination: The collected plant leaves were washed with tap water and deionized water, pressed dry, dried, and crushed. The soil samples were naturally air-dried. The Pb content was determined by atomic absorption spectrometry.
[0010] Step 5, Soil Pb pollution assessment in the experimental area: The single pollution index method is used to evaluate the degree of pollution of soil Pb concentration in the experimental area relative to its environmental quality standard;
[0011] Step Six: Comparison of Pb enrichment capacity: Based on laboratory Pb content measurements, the distribution characteristics of Pb content in each tree species are quantified.
[0012] The differences in the enrichment capacity of heavy metal Pb among green tree species were compared using enrichment coefficients and analysis of variance.
[0013] Step 7, Comparison of heavy metal Pb translocation capacity: The differences in the translocation capacity of each greening tree species for heavy metal Pb are compared using translocation coefficient and variance analysis.
[0014] Step 8: Screening of tree species for remediation of Pb-contaminated soil: Cluster analysis was used to comprehensively evaluate the Pb enrichment and translocation efficiency of greening tree species, and the greening tree species with the best Pb purification effect were screened.
[0015] As a preferred technical solution of the present invention: the test area in step one is soil with slight heavy metal lead (Pb) pollution, and the Pb concentration is higher than the background value of soil in Huai'an City; the test tree samples are of at least 6 varieties, which can grow normally in heavy metal polluted soil and have strong tolerance; the parameters of the test trees are: similar tree size and crown size, and healthy samples without diseases and pests.
[0016] As a preferred technical solution of the present invention: the test tree samples are common greening tree species along the roadside of the Ninglian Highway in Huai'an.
[0017] As a preferred technical solution of the present invention: the species of the test tree samples in step one are one or more of camphor, willow, ginkgo, goldenrain tree, photinia and osmanthus.
[0018] As a preferred technical solution of the present invention: the leaves collected in step two are required to be free from pests and diseases, grow well and have intact leaves, and the leaves of the same plant are mixed together to form one sample number and brought back to the laboratory.
[0019] As a preferred technical solution of the present invention: in step three, leaf samples and rhizosphere soil samples are collected correspondingly, and in step four, atomic absorption spectrometry is used to determine the Pb content of leaves and soil.
[0020] As a preferred embodiment of the present invention: in step five, the formula for calculating the single pollution index used to evaluate the Pb pollution status of the soil in the experimental area is as follows:
[0021] P ij =C ij / S ij
[0022] In the formula, P ij C represents the individual pollution index of pollutant i at the j-th sampling point; ij S represents the measured value of pollutant i at the j-th sampling point; ij The evaluation standard value for pollutant i; when P ij ≤1.0 indicates cleanliness, 1.0 < P ij ≤2.0 indicates light pollution, 2.0 < P ij ≤3.0 indicates moderate pollution, P ij A value greater than 3.0 indicates severe pollution.
[0023] As a preferred embodiment of the present invention: in step six, the formula for the bioaccumulation coefficient is:
[0024] BCF=C i / S i
[0025] In the formula, BCF is the enrichment coefficient; C i S represents the heavy metal element content of the i-th leaf sample, in mg / kg; i The BCF value corresponds to the heavy metal content in the rhizosphere soil sample, expressed in mg / kg. A higher BCF value indicates a stronger ability of the plant to accumulate heavy metals.
[0026] As a preferred embodiment of the present invention: in step seven, the formula for the heavy metal transport coefficient is:
[0027] BTF=C i / R i
[0028] In the formula, BTF is the translocation coefficient; C i R represents the heavy metal element content of the i-th leaf sample, in mg / kg. i The BTF represents the heavy metal content in the roots of plant samples, expressed in mg / kg. A higher BTF indicates a stronger ability of the plant to transfer heavy metals from its roots.
[0029] As a preferred technical solution of the present invention: in step eight, the K-means clustering analysis method is used to comprehensively evaluate the enrichment and translocation capacity of greening tree species for heavy metal Pb, and to screen out the tree species with the best soil heavy metal Pb purification efficiency.
[0030] Beneficial Effects: Compared with existing technologies, the tree species selection method for remediation of lead-contaminated soil described in this application has the following technical advantages:
[0031] 1. It solves the technical problems of a single indicator system, making it difficult to achieve complete removal through simple physical or chemical methods, and has the characteristics of high efficiency, low cost and environmental friendliness;
[0032] 2. It breaks away from the limitations of physical methods which consume a lot of resources and chemical methods which are prone to secondary pollution and damage the physical and chemical properties of soil. Using green tree species to purify soil heavy metals has the advantages of being economical, simple, easy to identify, having a long life cycle, not damaging the soil structure, and not easily causing secondary pollution.
[0033] 3. As an important part of urban construction, green plants not only beautify the environment, but also protect the topsoil and reduce soil erosion after forming vegetation.
[0034] 4. This invention proposes a tree species selection method for the remediation of heavy metal lead pollution. First, the preparatory work before tree species selection is determined. The purification efficiency of greening tree species on soil heavy metal lead is comprehensively evaluated by enrichment capacity and translocation capacity. The calculation process is simple and easy to operate, which makes it convenient for managers to quickly select suitable tree species for lead pollution remediation, thereby efficiently treating polluted areas. Attached Figure Description
[0035] Figure 1 This is a graph showing the differences in heavy metal Pb content in the leaves of different greening tree species in this application;
[0036] Figure 2 This is a diagram showing the enrichment capacity of the greening tree species in this application for the heavy metal Pb.
[0037] Figure 3 This is a diagram showing the translocation capacity of the greening tree species for the heavy metal Pb in this application.
[0038] Figure 4 This is a comprehensive cluster analysis diagram of the enrichment and translocation of heavy metal Pb in green tree species in this application;
[0039] Figure 5 These are photographs of the samples collected and preprocessed for this application. Detailed Implementation
[0040] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and not for limiting the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims. With the rapid development of urbanization and industrialization, motor vehicle exhaust emissions have become a serious source of pollution. Transportation is currently one of the main sources of heavy metal pollution in urban soil. Heavy metal pollution in soil poses a huge and serious potential threat to human and environmental safety and has become an urgent social problem to be solved. Physical and chemical methods for treating heavy metal pollution in soil have disadvantages such as resource consumption, secondary pollution, and damage to the soil's physicochemical properties, while greening plants have advantages such as high efficiency, low cost, and environmental friendliness. Therefore, the use of greening tree species for the remediation of heavy metal pollution in soil has gradually become a research hotspot. This invention can provide a reference for the selection of greening tree species for the remediation of lead pollution in urban roadside soil.
[0041] Example 1
[0042] A method for selecting tree species for remediation of lead-contaminated soil includes the following steps:
[0043] Step 1, Sample Selection: Determine the species, soil parameters, and tree parameters for several test trees; the soil in the test area is slightly contaminated with lead (Pb), and the Pb concentration exceeds the background value of soil in Huai'an City; the test trees must be of at least 6 species, capable of growing normally and resilient in heavy metal contaminated soil; the parameters of the test trees are: similar tree size and crown width, healthy and free from pests and diseases; the test trees are the main greening tree species at the intersection of Ninglian Highway and Meigao Road, and the species are one or more of camphor, willow, ginkgo, goldenrain tree, photinia, and osmanthus. Three test plots are set up for each greening tree species, and 5 healthy trees with basically the same diameter at breast height (DBH) and crown width are selected for replication in each plot, for a total of 90 sample trees; the DBH and crown width of each greening tree species are measured with a tape measure, and the tree height of each sample tree is measured with an ultrasonic height measuring device, and recorded separately;
[0044] Table 1 Basic Information on Sampled Tree Species
[0045] species Latin name academic name Generic name Tree height / m Stem breast / cm Crown width / m camphor Cinnamomumcamphora Lauraceae genus Cinnamomum 8.1～14.8 27.5～35.5 4.41～4.5 Photinia Photiniaserratifolia Rosaceae Photinia 3.5～4.2 20.0～23.0 2.9～3.2 Osmanthus fragrans Osmanthusfragrans Oleaceae Osmanthus 2.8～3.2 15～18 2.0～4.4 weeping willow Salixbabylonica Salicaceae Salix 19.5～21.3 34.0～36.0 11.2～12.7 Goldenrain tree Koelreuteriapaniculata Sapindaceae genus Luan 6.3～7.3 19.0～22.0 3.2～5.4 ginkgo Ginkgobiloba Ginkgoaceae Ginkgo genus 4.5～7.6 21.0～25.0 4.1～5.7
[0046] Step 2, Leaf Sample Collection: The weather should be sunny and have a light breeze (wind speed less than 3.4 m / s) on the day of collection. -1 In addition, there should be no rain or strong winds within 7 days before the sample collection; a total of 90 sample plants of 6 greening tree species were collected, and leaves were collected from the east, south, west and north directions of the canopy, with 10 leaves collected from each direction; the collected leaves should be free of pests and diseases, grow well and be intact, and the leaves of the same plant should be mixed together as one sample number and brought back to the laboratory.
[0047] Step 3, soil sampling: Nine random sampling points were selected in the test area to collect bare soil (0-20cm) to evaluate the Pb pollution status of the soil in the test area, and soil samples (0-20cm) were collected from the root system of each plant. The soil samples from each sampling point and plant were mixed on-site to form a mixed sample. Approximately 500g of soil sample was taken using the quartering method, placed in a soil sampling bag, numbered, and brought back to the laboratory.
[0048] Step 4, Sample processing and lead content determination: The collected leaves were cleaned with tap water and deionized water, classified and numbered, and laid on absorbent paper for water absorption. After pressing dry, the water-absorbed leaf samples were placed into kraft paper envelopes, labeled, and placed in an oven to dry. In the oven, the samples were first blanched at 105℃ for 30 minutes, and then dried at 80℃ to constant weight. The dried samples were then crushed and passed through a 60-mesh nylon sieve, and then placed into sealed bags and labeled.
[0049] Place the collected soil samples in a ventilated place, mark them, spread them out on newspaper, let them air dry naturally, grind them through a 100-mesh nylon sieve, and then grind them into powder multiple times. Mark the powdered samples and put them into sealed bags.
[0050] After digestion, the supernatant was collected, and the Pb content was determined by atomic absorption spectrometry. Each sample was measured three times. Step five: Soil Pb pollution assessment in the experimental area: Based on the Pb content in the bare soil samples of the experimental area, the soil pollution status was evaluated using the single-item pollution index method. The calculation formula is as follows:
[0051] P ij =C ij / S ij
[0052] In the formula, P ij C represents the individual pollution index of pollutant i at the j-th sampling point; ij S represents the measured value of pollutant i at the j-th sampling point; ij The evaluation standard value for pollutant i; when P ij ≤1.0 indicates cleanliness, 1.0 < P ij ≤2.0 indicates light pollution, 2.0 < P ij ≤3.0 indicates moderate pollution, P ij A value greater than 3.0 indicates severe pollution.
[0053] Table 2 Analysis of heavy metal content in soil and pollution assessment
[0054]
[0055] Table 2 shows that the heavy metal Pb content in the bare soil of the experimental area exceeded the background value of soil in Huai'an City, and the single pollution index P iThe value was 1.83, which falls within the range (1,2], indicating that the soil Pb in the experimental area was slightly polluted.
[0056] Step Six: Comparison of Heavy Metal (Pb) Accumulation Capacity: Based on laboratory measurements of Pb content, the distribution characteristics of heavy metal content in each tree species are quantified. The differences in heavy metal accumulation capacity among greening tree species are compared using bioaccumulation coefficients and analysis of variance. The formula for the bioaccumulation coefficient is:
[0057] BCF=C i / S i
[0058] In the formula, BCF is the enrichment coefficient; C i S represents the heavy metal element content of the i-th leaf sample, in mg / kg; i The BCF value corresponds to the heavy metal content in the rhizosphere soil sample, expressed in mg / kg. A higher BCF value indicates a stronger ability of the plant to accumulate heavy metals.
[0059] Step 7, Comparison of heavy metal Pb translocation capacity: The translocation coefficient and variance analysis are used to compare the differences in translocation capacity among tree species. The formula for the heavy metal translocation coefficient is:
[0060] BTF=C i / R i
[0061] In the formula, BTF is the translocation coefficient; C i R represents the heavy metal element content (mg / kg) of the i-th leaf sample; i The BTF represents the heavy metal content in the roots of plant samples, expressed in mg / kg. A higher BTF indicates a stronger ability of the plant to transfer heavy metals from its roots.
[0062] Step 8, Screening of tree species for remediation of heavy metal Pb contaminated soil: K-means cluster analysis was used to comprehensively evaluate the enrichment and translocation capacity of greening tree species for heavy metal Pb, and the greening tree species with the best heavy metal Pb purification effect were screened.
[0063] Figure 1 The results showed that the overall trend of heavy metal Pb content in the leaves of the six greening tree species was Photinia > Ginkgo > Willow > Osmanthus > Goldenrain Tree > Camphor Tree, and there were significant differences in Pb content among the tree species.
[0064] Figure 2 The results showed that the enrichment capacity of the six greening tree species for heavy metal Pb was as follows: Ginkgo > Photinia > Willow > Osmanthus > Goldenrain Tree > Camphor Tree, and there were significant differences in the enrichment capacity of each tree species for Pb.
[0065] Figure 3 The results showed that the six tree species had different transport capacities for the heavy metal Pb, with the overall trend being: Photinia > Osmanthus > Ginkgo > Willow > Goldenrain Tree > Camphor Tree.
[0066] Figure 4 The results show that cluster analysis comprehensively evaluated the enrichment and translocation capabilities of six greening tree species, classifying them into three categories: Category I is Photinia, Category II is Osmanthus, and Category III includes Camphor Tree, Goldenrain Tree, Willow, and Ginkgo. This indicates that Photinia has the strongest Pb purification capacity, followed by Osmanthus, while Camphor Tree, Goldenrain Tree, Willow, and Ginkgo have the weakest. Therefore, Photinia can be considered the optimal choice for greening tree species to control heavy metal pollution along roads.
[0067] The specific embodiments described herein are merely illustrative examples of the present invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, but without departing from the spirit of the present invention or exceeding the scope defined by the appended claims.
Claims
1. A method for selecting tree species for remediation of lead-contaminated soil, characterized in that, The method includes the following steps: Step 1, Sample Selection: Determine the species, soil parameters, and tree parameters of several test tree samples; Step 2, leaf sampling: Collect 10 leaves from each plant in the four directions of east, south, west and north. Step 3, soil sampling: Randomly collect bare soil and soil samples from the root system of each plant in the test area. Mix the samples on-site to form a mixed sample, put it into a special sampling bag, number it and bring it back to the laboratory. Step 4, Sample processing and lead content determination: The collected plant leaves were washed with tap water and deionized water, pressed dry, dried, and crushed. The soil samples were naturally air-dried. The Pb content was determined by atomic absorption spectrometry. Step 5, Soil Pb pollution assessment in the experimental area: The single pollution index method is used to evaluate the degree of pollution of soil Pb concentration in the experimental area relative to its environmental quality standard; Step 6, Comparison of heavy metal Pb enrichment capacity: Based on the laboratory Pb content determination, the distribution characteristics of Pb content in each tree species are quantified, and the differences in the heavy metal Pb enrichment capacity of greening tree species are compared using enrichment coefficient and variance analysis. Step 7, Comparison of heavy metal Pb translocation capacity: The differences in the translocation capacity of each greening tree species for heavy metal Pb are compared using translocation coefficient and variance analysis. Step 8: Screening of tree species for remediation of Pb-contaminated soil: Cluster analysis was used to comprehensively evaluate the Pb enrichment and translocation efficiency of greening tree species, and the greening tree species with the best Pb purification effect were screened.
2. The method for selecting tree species for remediation of lead-contaminated soil according to claim 1, characterized in that: The test area described in step one is soil with mild lead (Pb) pollution, and the Pb concentration is higher than the background value of soil in Huai'an City; the test tree samples are of at least 6 species, which can grow normally in heavy metal polluted soil and have strong tolerance; the parameters of the test trees are: similar tree size and crown size, and healthy samples without diseases or pests.
3. The method for tree species selection for remediation of lead-contaminated soil according to claim 2, characterized in that: The tested tree samples were common roadside greening tree species along the Ninglian Highway within Huai'an.
4. The method for tree species selection for remediation of lead-contaminated soil according to claim 2, characterized in that: The tested tree specimens are one or more of the following species: camphor tree, willow, ginkgo, goldenrain tree, photinia, and osmanthus.
5. The method for selecting tree species for remediation of lead-contaminated soil according to claim 1, characterized in that: In step two, the collected leaves must be free from pests and diseases, grow well, and be intact. Leaves from the same plant should be mixed together and numbered as one sample to be brought back to the laboratory.
6. The method for tree species selection for remediation of lead-contaminated soil according to claim 1, characterized in that: In step three, leaf samples from the plant specimens were collected in correspondence with rhizosphere soil samples, while samples from bare soil were collected at randomly selected points.
7. The method for tree species selection for remediation of lead-contaminated soil according to claim 1, characterized in that: In step five, the formula for calculating the soil single pollution index is: P ij =C ij / S ij In the formula, P ij C represents the individual pollution index of pollutant i at the j-th sampling point; ij S represents the measured value of pollutant i at the j-th sampling point; ij The evaluation standard value for pollutant i; when P ij ≤1.0 indicates cleanliness, 1.0 < P ij ≤2.0 indicates light pollution, 2.0 < P ij ≤3.0 indicates moderate pollution, P ij A value greater than 3.0 indicates severe pollution.
8. The method for tree species selection for remediation of lead-contaminated soil according to claim 1, characterized in that: In step six, the formula for the bioaccumulation factor is: BCF=C i / S i In the formula, BCF is the enrichment coefficient; C i S represents the heavy metal element content of the i-th leaf sample, in mg / kg; i The BCF value corresponds to the heavy metal content in the rhizosphere soil sample, expressed in mg / kg. A higher BCF value indicates a stronger ability of the plant to accumulate heavy metals.
9. The method for selecting tree species for remediation of lead-contaminated soil according to claim 1, characterized in that: In step seven, the formula for the heavy metal transport coefficient is: BTF=C i / R i In the formula, BTF is the translocation coefficient; C i R represents the heavy metal element content of the i-th leaf sample, in mg / kg. i The BTF represents the heavy metal content in the roots of plant samples, expressed in mg / kg. A higher BTF indicates a stronger ability of the plant to transfer heavy metals from its roots.
10. The method for tree species selection for remediation of lead-contaminated soil according to claim 1, characterized in that: In step eight, K-means cluster analysis is used to comprehensively evaluate the enrichment and translocation capacity of heavy metal Pb by greening tree species.