Method for combined remediation of cadmium-contaminated soil by using oilseed rape and sulfur nanoparticles

Abstract

The invention relates to the technical field of environmental protection, and discloses a method for jointly repairing cadmium-polluted soil by using oilseed rape and sulfur nanoparticles. Compared with a traditional remediation method, the sulfur nanoparticle-rape combined remediation method for farmland cadmium pollution, which is easy to popularize in a large area and is simple and efficient, is created by introducing the nanoparticles of the nutrient element sulfur necessary for plants, selecting cadmium accumulation type rape varieties mainly planted in the middle and lower reaches of the Yangtze River for matching and selecting a proper rape harvesting period. According to a specific oilseed rape seedling transplanting mode, sulfur nanoparticles with a certain concentration are applied, and the oilseed rape is harvested in time when the oilseed rape buds, so that the soil cadmium pollution remediation efficiency is greatly improved, the situation that cadmium absorbed by leaves on the overground part of the oilseed rape falls off due to natural maturity and is re-discharged into the soil environment is also remarkably reduced, and the secondary pollution of farmland is reduced. The remediation method can be applied to the technical field of environmental protection, is particularly applied to plant remediation of light and moderate cadmium contaminated soil in the middle and lower reaches of the Yangtze River, and is easy and convenient to operate and wide in application range.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, and to a method for remediating cadmium-contaminated soil using rapeseed and sulfur nanoparticles. Background Technology

[0002] Cadmium (Cd) is a highly toxic heavy metal that is widely found in nature. Currently, cadmium pollution continues to seriously threaten agricultural production, the ecological environment, and human health, making it one of the most important environmental problems facing the world. The Yangtze River Delta region, as an important agricultural production base and a renowned commodity grain base in my country, accounts for more than 12% of the country's total annual agricultural output and grain production. However, in recent years, the soil environment of farmland in the Yangtze River Delta region has become increasingly concerning, with Jiangsu, Zhejiang, Shanghai, and Anhui provinces showing the highest levels of cadmium (Cd) accumulation in their farmland soils. Phytoremediation technology, utilizing hyperaccumulating plants to remediate contaminated soil, is considered a promising green method for controlling heavy metal pollution in soil due to its advantages such as no secondary pollution, low investment, and no damage to the ecological environment. However, currently, there are very few applicable hyperaccumulating plant resources for remediation that have been discovered domestically and internationally. Moreover, most discovered hyperaccumulating plants generally suffer from slow growth, small biomass, poor remediation depth, and low efficiency, hindering the application and rapid development of this technology. Utilizing fast-growing, high-biomass, and heavy metal-tolerant accumulating plants or crops to enhance their remediation efficiency through exogenous (substance) enhancement and genetic modification has become a new research hotspot in the field of phytoremediation, and is considered an important way to solve the bottlenecks that limit the application of phytoremediation technology.

[0003] Rapeseed is a major oilseed crop widely cultivated throughout my country, with the largest planting area and total output in the world. Its greatest advantage lies in its broad adaptability to production and its strong ability to accumulate the heavy metal cadmium. Although there have been reports on using EDTA and microbial agents to enhance the remediation of cadmium-contaminated soil with rapeseed, the rapeseed varieties used are not regionally specific, have low yields, and are not the main local varieties. Furthermore, the enhancers are relatively expensive, resulting in high costs for large-scale application to cadmium-contaminated farmland, and some enhancers pose a risk of secondary pollution. More importantly, existing technologies for rapeseed remediation all involve harvesting rapeseed after it has matured. However, the cadmium absorbed by the rapeseed after harvesting is returned to the field in the form of fallen leaves, flowers, and stubble. In particular, the cadmium accumulation in fallen leaves is much higher than that in the other above-ground parts of the rapeseed, which not only reduces the remediation efficiency but also causes secondary pollution.

[0004] Therefore, how to provide an efficient and safe phytoremediation technology for cadmium-contaminated soil is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, and in response to the shortcomings of current phytoremediation methods for heavy metal contaminated soil, this invention provides a highly efficient and safe method for remediating cadmium-contaminated soil by combining novel environmentally friendly sodium-sulfur nanoparticles with a special rapeseed variety. This method is effective in remediating cadmium-contaminated soil, has strong applicability, and is simple and environmentally friendly.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for remediating cadmium-contaminated soil using rapeseed and sulfur nanoparticles includes the following steps:

[0008] 1) Land preparation: Deep plow the cadmium-contaminated farmland to a depth of 20-30cm, apply base fertilizer, harrow and level the land to make ridges, with a ridge width of 1-1.2m, a ridge height of 15-20cm, and a ridge spacing of 25-30cm;

[0009] 2) Seedling raising: In late September, sow seeds directly in cadmium-contaminated farmland. Prepare 0.1 mu of land per mu of farmland for seedling raising. Sow rapeseed seeds evenly in shallow furrows, cover with soil and water.

[0010] 3) Transplanting: Transplant seedlings at a spacing of 30×30cm from the end of October to the beginning of November. When transplanting, first apply sulfur nanoparticles to the hole. Mix the sulfur nanoparticles with vermiculite and sprinkle them into the hole. Water thoroughly after transplanting.

[0011] 4) Field management: Weeding and watering should be carried out in accordance with the conventional field management of rapeseed. In early January of the following year, apply topdressing fertilizer, with 10-15 kg of urea per mu.

[0012] 5) Harvesting: Harvest the entire rapeseed plant in mid-to-late March, from the budding stage to the initial flowering stage.

[0013] As a further limitation and supplement to the above technical solution, the farmland soil is a low to medium cadmium polluted farmland soil with a cadmium concentration not exceeding 10 mg / kg.

[0014] As a further limitation and supplement to the above technical solution, in step 1), the base fertilizer is potassium chloride compound fertilizer with a nitrogen-phosphorus-potassium ratio of 15-15-15, at 25-30 kg per mu, and boron fertilizer, at 0.4-0.5 kg per mu.

[0015] As a further limitation and supplement to the above technical solution, in step 2), the rapeseed variety is cadmium-accumulating rapeseed and the main variety planted in the middle and lower reaches of the Yangtze River is "Qinyou 10". The sowing depth is 1-2cm, the row spacing is 20-30cm, and the seeding rate is 300-400g per mu in the seedbed.

[0016] As a further limitation and supplement to the above technical solution, in step 3), the seedlings are 40-45 days old, have 6-7 green leaves, and are 15-20 cm tall.

[0017] As a further limitation and supplement to the above technical solution, in step 3), the sulfur nanoparticles have a particle size of 30-50 nm, a purity of >95%, and an application rate of 10-20 kg / mu.

[0018] As a further limitation and supplement to the above technical solution, in step 5), timely harvesting means that the rapeseed begins to be harvested as soon as it begins to bud and flower, so as to avoid the cadmium absorbed by the leaves returning to the farmland after the leaves fall off naturally in the later stage of reproductive growth.

[0019] As a further limitation and supplement to the above technical solution, in step 5), the whole plant is harvested by mechanically or manually pulling out the shallow-rooted rapeseed along with its roots to harvest as much as possible.

[0020] Compared with existing technologies, this invention discloses a method for remediating cadmium-contaminated soil using rapeseed and sulfur nanoparticles, which has the following beneficial effects:

[0021] 1) High operability: Compared with Cd hyperaccumulators that have low biomass, slow growth and weak adaptability, rapeseed has a wide planting area, strong adaptability, fast growth, large biomass and strong heavy metal accumulation capacity, and is easy to promote and apply on a large scale, making it highly operable.

[0022] 2) High efficiency: Using sulfur nanoparticles assisted in the remediation of rapeseed using this method can increase the biomass of the aboveground parts and roots of rapeseed by 42% and 46% and the Cd accumulation by 80% and 118%, respectively, which greatly improves the remediation efficiency.

[0023] 3) High safety: Traditional rapeseed remediation involves harvesting the above-ground parts after the rapeseed has fully matured. On the one hand, the remaining stems and seeds after maturity have very low Cd content; on the other hand, all leaves fall off after maturity, and since leaves are the main site of Cd accumulation, their shedding means that the Cd absorbed by the rapeseed leaves returns to the farmland, inevitably causing secondary pollution. This technology, however, begins harvesting when the rapeseed shows budding and initial flowering, completely avoiding the aforementioned shortcomings of the original technology. Furthermore, sulfur itself is an essential nutrient element for plants, and there is no safety risk associated with using it for rapeseed remediation. Therefore, the timely harvesting technology and sulfur nanotechnology of this method ensure its safety. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1This is a map of an experimental plot in cadmium-contaminated farmland.

[0026] Figure 2 The images show the rapeseed at the initial flowering stage (suitable harvest period) and the silique stage (when all leaves have fallen off and harvest is not advisable).

[0027] Figure 3 This is a diagram showing the distribution of Cd accumulation in different parts of the aboveground plant after rapeseed matures.

[0028] Figure 4 The figure shows the effect of different SNP concentrations on Cd accumulation in the aboveground parts and roots of rapeseed during the budding and early flowering stages.

[0029] Figure 5 The figure shows the effect of different SNP concentrations on the aboveground and root biomass of rapeseed at the budding and early flowering stage. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention provides a method for remediating cadmium-contaminated soil using rapeseed and sulfur nanoparticles, which is of great significance for the effective treatment of Cd-contaminated farmland soil in my country.

[0032] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0033] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0034] Example

[0035] This example uses a cadmium-contaminated farmland plot as a case study. The cadmium concentration in the farmland was 6.04 mg / kg, approximately 10 times the national screening value for Cd-contaminated agricultural land. The planting results are shown in [the provided text]. Figure 1 The specific method is as follows:

[0036] 1) Seedling raising: On September 22, 2024, seedling raising was carried out directly in cadmium-contaminated farmland in southern Jiangsu. 0.1 mu of land per mu of farmland was prepared for seedling raising. 30g of cadmium-accumulating rapeseed "Qinyou 10" seeds were evenly sown in shallow furrows at an average depth of 1.5cm and a row spacing of 25cm. The seeds were then covered with soil and watered.

[0037] 2) Land preparation: On October 26, 2024, the cadmium-contaminated farmland was deeply plowed to a depth of 25cm, and potassium chloride compound fertilizer with a nitrogen-phosphorus-potassium ratio of 15-15-15 was applied at a rate of 25kg per mu, as well as boron fertilizer at a rate of 0.4kg per mu. The land was then harrowed, leveled, and raised into beds with a width of 1.2m, a height of 20cm, and a spacing of 30cm between beds.

[0038] 3) Transplanting: On November 5, 2024, when the seedlings are about 40 days old, have 6-7 green leaves, and are 15-20cm tall, they should be transplanted to the field at a spacing of 30×30cm. When transplanting, sulfur nanoparticles should be applied to the planting hole first. The SNPs should have a particle size of 47nm and a purity of >95%. The sulfur nanoparticles and vermiculite should be mixed evenly and then sprinkled into the planting hole. The application rates of sulfur nanoparticles are 0, 5, 10, 20, and 30 kg / mu, respectively. After transplanting, water thoroughly to settle the roots.

[0039] 4) Field management: Weeding and watering shall be carried out in accordance with the conventional field management of rapeseed. On January 12, 2025, apply urea fertilizer at a rate of 15 kg per mu.

[0040] 5) Harvesting: On March 20, 2025, the entire rapeseed plant was harvested from the budding stage to the initial flowering stage, and the aboveground biomass and Cd accumulation were measured. On May 16, 2025, after the rapeseed matured, the Cd accumulation in the aboveground stems, grains and fallen leaves was measured.

[0041] The technology of this invention is demonstrated using real-world repair examples; specific experimental results can be found in the appendix to the specification. Figure 1 ~Attached Figure 5 .

[0042] The results of rapeseed harvesting after maturity indicate that ( Figure 3 The distribution of Cd accumulation in different parts of rapeseed after maturity shows that the highest Cd accumulation is found in fallen leaves, accounting for 84% of the total Cd accumulation in all above-ground parts of rapeseed. Therefore, harvesting rapeseed after maturity not only results in low Cd accumulation in the harvestable stems and seeds, but also returns the Cd absorbed in the leaves to the farmland due to natural maturation and shedding.

[0043] The results of harvesting rapeseed before leaf fall indicate that ( Figure 4 Compared with the control Cd-contaminated soil without SNPs, the addition of 10-30 kg / mu of SNPs to Cd-contaminated soil promoted the accumulation of Cd in the aboveground parts and roots of rapeseed during the budding stage to varying degrees. It can be seen that the application of SNPs can effectively improve the efficiency of rapeseed in remediating Cd-contaminated farmland soil.

[0044] Furthermore, the effects of different SNP concentrations on Cd accumulation capacity and biomass in rapeseed showed that ( Figures 4-5The highest Cd accumulation in the aboveground parts and roots of rapeseed was observed under SNP exposure of 20 kg / mu, while the Cd accumulation under SNP exposure of 30 kg / mu was comparable to that under SNP exposure of 10 kg / mu. Before rapeseed leaves fell off, the Cd accumulation in the aboveground parts and roots of rapeseed exposed to 20 kg / mu SNP increased by 80% and 118% respectively compared to the control without SNP application, while the aboveground and root biomass increased by 42% and 46% respectively. Therefore, it is recommended that an addition rate of 10-20 kg / mu be set as the concentration range for SNP combined with rapeseed to remediate Cd-contaminated soil.

[0045] In summary, this invention provides a safe and efficient method for remediating Cd-contaminated farmland soil using SNPs in conjunction with rapeseed, providing technology and methods for the remediation of Cd-contaminated farmland in my country.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for remediating cadmium contaminated soil using a combination of Brassica juncea and sulfur nanoparticles, characterized in that, Comprising the following steps: 1) land consolidation: deep plowing 20-30 cm of cadmium contaminated farmland, and spreading base fertilizer, raking and leveling to make ridges; 2) seedling raising: direct seeding and seedling raising in cadmium contaminated farmland in late September, 0.1 mu of land per mu of farmland is prepared for seedling raising, shallow trench is opened, rape seeds are evenly sown and covered with soil and watered; 3) transplanting: seedling transplanting is carried out at the end of October to the beginning of November, planting is carried out according to 30x30cm plant spacing, sulfur nanoparticles are hole applied before planting, sulfur nanoparticles and vermiculite are mixed and then spread into the hole, and timely watering is carried out after planting to fix the root; 4) field management: weed control and watering are carried out according to the conventional field management of rape, and winter fertilizer is applied in early January of the next year; 5) harvesting: in mid to late March, the whole plant is harvested in time at the present budding stage to the early flowering stage of rape.

2. The method for repairing cadmium contaminated soil by using oilseed rape and sulfur nanoparticles according to claim 1, characterized in that, In step 1), the base fertilizer is potassium chloride compound fertilizer with nitrogen, phosphorus and potassium ratio of 15-15-15, 25-30 kg / mu, and boron fertilizer, 0.4-0.5 kg per mu.

3. The method for repairing cadmium contaminated soil by using oilseed rape and sulfur nanoparticles according to claim 1, characterized in that, In step 2), the variety of the rape is cadmium accumulating rape and the Yangtze River middle and lower reaches main variety "Qinyou No. 10", the seeding depth is 1-2 cm, the trench spacing is 20-30 cm, and the seed bed uses 300-400 g per mu.

4. The method for repairing cadmium contaminated soil by using oilseed rape and sulfur nanoparticles according to claim 1, characterized in that, In step 3), the seedling age is 40-45 days, the green leaf is 6-7 pieces, and the plant height is 15-20 cm.

5. The method for repairing cadmium contaminated soil by using oilseed rape and sulfur nanoparticles according to claim 1 or 4, characterized in that, In step 3), the particle size of the sulfur nanoparticles is 30-50 nm, the purity is >95%, and the application amount is 10-20 kg / mu.

6. The method for repairing cadmium contaminated soil by using oilseed rape and sulfur nanoparticles according to claim 1, characterized in that, In step 4), the winter fertilizer is urea, 10-15 kg / mu.

7. The method for repairing cadmium contaminated soil by using oilseed rape and sulfur nanoparticles according to claim 1, characterized in that, In step 5), the timely harvesting refers to harvesting as soon as the rape begins to appear present budding and early flowering, avoiding the natural shedding of leaves after the reproductive growth period, which causes cadmium absorbed by the leaves to return to the farmland. 8.The method of claim 1, wherein the method is characterized by, In step 5), the whole plant is harvested by mechanical harvesting or manual harvesting to pull out the shallow root system of the rape to harvest all.

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