Method for phytoremediation of petroleum-contaminated soil

Abstract

The invention belongs to the field of contaminated soil treatment, and particularly relates to a method for phytoremediation of petroleum-contaminated soil, which comprises the step of planting cornflower and / or aster on the petroleum-contaminated soil for soil remediation. According to the method, the cornflower and / or the radix asteris are / is adopted for remediation of the petroleum-contaminated soil, the degradation rate of petroleum in the petroleum-contaminated soil is high, the degradation rate of petroleum in the soil of 12%, 8% and 4% of the petroleum-contaminated soil and the degradation rate of petroleum in the soil of the radix asteris are 56.94%, 84.72% and 86.33% respectively, and the degradation rate of cornflower to petroleum in the soil is 73.89%, 79.60% and 87.30% respectively and is higher than that of cornflower in most of existing remediation methods. Flowers of the cornflower and the tatarian aster are beautiful and large in biomass and can be planted in a petroleum pollution area to form a flower sea, and the target of petroleum pollution remediation is achieved while viewing is achieved.

Description

Technical Field

[0001] This invention belongs to the field of contaminated soil remediation, specifically relating to a method for phytoremediation of petroleum-contaminated soil. Background Technology

[0002] Oil-contaminated soil is one of the major environmental problems caused by oil extraction, storage, transportation, processing, and spills. Both oil development and utilization can cause soil pollution, with current oil-contaminated soil reaching 100,000 tons (Zhang Jinqiu, 2021). Oil is composed of saturated hydrocarbons, aromatics, colloids, and asphaltenes, with colloid content often exceeding 20% ​​and asphaltenes content reaching 10%-30%. It is characterized by high viscosity, difficulty in degradation, and difficulty in treatment (Hoang et al., 2021). Petroleum hydrocarbon pollutants (such as polycyclic aromatic hydrocarbons, alkanes, and aromatic hydrocarbons) are toxic, persistent, and bioaccumulative, posing a serious threat to soil ecosystems and human health. Currently, remediation technologies for oil-contaminated soil mainly include physicochemical methods (such as thermal desorption, chemical oxidation, and soil leaching) and bioremediation methods (such as microbial remediation and phytoremediation). Among these, phytoremediation has become a research hotspot due to its advantages such as low cost, environmental friendliness, and sustainability.

[0003] Currently, microbial remediation relies on exogenous microorganisms or indigenous microbial communities to degrade petroleum pollutants. However, microbial activity is easily affected by environmental factors (such as temperature, pH, and oxygen content), and the degradation efficiency is low, making it difficult to completely remove high concentrations of petroleum pollution (Ajona and Vasanthi, 2021; Hoang et al., 2021; Wang et al., 2013).

[0004] Currently, the plants commonly used for oil pollution remediation are mostly herbaceous plants, such as ryegrass, alfalfa, reeds, Suaeda salsa, tall fescue, bermudagrass, pigweed, four o'clock flower, alfalfa, oxtail grass, impatiens, morning glory, bulrush, corn, cotton, sedge, long-stemmed clover, calendula, black-eyed Susan, sunflower, morning glory, daylily, iris, willow, tamarisk, etc. (Zhang Jinqiu, 2021; Wang Yanan et al., 2016; Moghadam et al., 2014). However, these plants generally have the following problems: Low tolerance and low degradation rate: While some plants can tolerate petroleum pollution, their ability to degrade hydrocarbon pollutants is limited, resulting in long remediation cycles. Alfalfa ( Alfalfa The degradation rate of petroleum hydrocarbons was 55.24% (Chen Mingzhu et al., 2022); daylily ( Hemerocallis middendorfii ) for 10 and 40 g·kg -1 The removal rates of petroleum hydrocarbons in contaminated soil were 53.7% and 33.4%, respectively (Wang Yanan et al., 2016); Iris ( Yellow flag irisThe removal rates of 10, 20, and 40 g·kg⁻¹ pollution levels were 42.1%, 33.1%, and 31.2%, respectively (Wang Yanan et al., 2016); Suaeda salsa ( Suaeda salsa The degradation rates of 2%, 4% and 6% pollution levels were 39%, 48% and 31% respectively (Yu Yilei et al., 2018); the degradation rates of Changyao Babao for 12, 20 and 39 g·kg⁻¹ pollution levels were 48%, 24% and 23% respectively (Cheng Lijuan and Zhou Qixing, 2014); the removal rates of petroleum hydrocarbons in the rhizosphere soil of Black-eyed Susan in 3%, 6% and 8% oil-contaminated soil were 73%, 81% and 27% respectively (Wang Jincheng et al., 2023).

[0005] Small biomass and shallow root system: Herbaceous plants such as ryegrass have shallow root systems, making it difficult to effectively remediate deeply polluted soil.

[0006] Poor ecological adaptability: Some remediation plants have high requirements for soil environment and are difficult to grow in arid, saline-alkali or barren oil-contaminated soils.

[0007] The main difficulties in solving the above problems are as follows: (1) It is difficult to screen plants that have high tolerance, rapid growth ability and efficient degradation of petroleum pollutants.

[0008] (2) The efficiency of phytoremediation is greatly affected by soil physicochemical properties (such as pH and organic matter content) and climate conditions (such as temperature and precipitation), making it difficult to achieve stable and efficient remediation results.

[0009] (3) Existing restoration plants often lack landscape beautification value and are difficult to improve the land reuse value while restoring pollution.

[0010] References Chen Mingzhu, Shi Chong, He Feiyan, Luo Yi, Dong Ding. Screening of plants for remediation of petroleum-contaminated soil in Karamay Oilfield [J]. Guangdong Chemical Industry, 2022, 49(04):129-132. Wang Yanan, Cheng Lijuan, Zhou Qixing. Rhizosphere mechanism and root metabolomics analysis of Hemerocallis fulva in remediation of petroleum hydrocarbon-contaminated soil [J]. Environmental Science, 2016a, 37(05):1978-1985. Wang Yanan, Cheng Lijuan, Zhou Qixing. Remediation of petroleum hydrocarbon-contaminated soil by iris and analysis of root metabolism [J]. Environmental Science, 2016b, 37(04):1531-1538. Liu Zili, Wang Hongqi, Kong Dekang, et al. Degradation of petroleum hydrocarbons under different plant-microbe co-remediation systems [J]. Journal of Environmental Engineering, 2018, 12(1):8. Wang Lili, Yang Qian. Inoculation with Bacillus subtilis and arbuscular mycorrhizal fungi promotes the remediation of petroleum-contaminated soil by red clover [J]. Jiangsu Agricultural Sciences, 2016, 44(5):4. Yang Xuelian, Li Fengmei, Liu Wanting, et al. Screening and degradation characteristics of highly efficient petroleum-degrading bacteria [J]. Journal of Agricultural Environmental Science, 2008(1):230-233. Yu Yilei, Ma Muyuan, Xu Weigang, et al. Experimental study on the remediation of crude oil contaminated soil in the Yellow River Delta using Suaeda salsa [J]. Journal of Ecology and Environment, 2018, 27(10): 1958-1965. Cheng Lijuan, Zhou Qixing. Study on the remediation of petroleum hydrocarbon-contaminated soil by wild ornamental plant *Gnaphalium affine* [J]. Journal of Environmental Sciences, 2014, 34(04): 980-986. Wang Haifeng, Bao Mutai, Han Hong, et al. Isolation and identification of a strain of Bacillus subtilis and its degradation characteristics of heavy oil [J]. Journal of Shenzhen University (Science and Engineering Edition), 2009, 26(03):221-227. Zhang Jinqiu. Research on plant-microbial remediation of petroleum-contaminated soil [D]. Yanshan University. 2021. Wang Xinwei, Cai Ting, Liu Yu. Research progress on microbial degradation of heavy components in heavy oil [J]. Journal of Ecology and Environment, 2013, 22(7): Wang Jincheng, Jing Mingbo, Zhang Wei, Zhang Gaosen, Zhang Binglin, Liu Guangxiu. 2023. Phytoremediation effect of Black-eyed Susan (Rudbeckia hirta) on oil-contaminated soil in the Loess Plateau of Longdong. Journal of Ecology, 42(4): 933-945, 1255-1262. Hoang SA, Lamb D, Seshadria B, et al. Rhizoremediation as a green technology for the remediation of petroleum hydrocarbon-contaminated soils[J]. Journal of Hazardous Materials, 2021,401:123282. Ajona M, Vasanthi P. Bioremediation of petroleum contaminated soils-Areview[J]. Materials Today: Proceedings, 2021,45:7117-7122. Nwaogu, LA, Onyeze, GOC, Nwabueze, R N. Degradation of diesel oil in a polluted soil using Bacillus subtilis[J]. African Journal ofBiotechnology, 2008,7(12):1939-1943. Panchenko L, Muratova A, Dubrovskaya E, et al. Natural and Technical Phytoremediation of Oil-Contaminated Soil[J]. Life. 2023; 13(1):177. https: / / doi.org / 10.3390 / life13010177 Liu Huan, Huang Xin, Fan Xiaoru, et al. Phytoremediation of crude oil-contaminated sediment using Suaeda heteroptera enhanced by Nereissuccineaand oil-degrading bacteria[J]. International Journal of Phytoremediation, 2023, 25(3): 322-328. DOI:10.1080 / 15226514.2022.2083576. Summary of the Invention To address the aforementioned technical problems, this invention aims to screen plants with the following characteristics for the remediation of petroleum-contaminated soil: (1) High tolerance: Previous studies have found that the concentration of petroleum in soil remediation plants is 0.5%-10%, and there are no reports of remediation plants that can tolerate higher concentrations.

[0011] (2) Ornamental flowers: In the past, the plants used for soil oil pollution remediation were mostly weeds, which had weak ornamental value and lacked landscape beautification value, making it difficult to improve the land reuse value while remediating pollution.

[0012] To address the aforementioned technical problems, this invention provides a method for phytoremediation of petroleum-contaminated soil, comprising the step of planting cornflowers and / or aster on petroleum-contaminated soil for soil remediation.

[0013] In the above method, the seeds of cornflower and / or aster can be directly sown on petroleum-contaminated soil or seedlings can be raised first and then transplanted onto petroleum-contaminated soil.

[0014] In the above method, the oil-contaminated soil is soil with an oil mass percentage higher than 0%, such as soil with an oil mass percentage of 4-12%. In the embodiments of the present invention, soil with an oil mass percentage of 12%, soil with an oil mass percentage of 8%, and soil with an oil mass percentage of 4% are involved.

[0015] This invention achieves low-cost, green, and sustainable remediation of petroleum-contaminated soil by screening flowering plants with the ability to efficiently degrade petroleum hydrocarbon pollutants. It is applicable to the ecological management and remediation of contaminated sites during petroleum extraction, storage, transportation, and processing.

[0016] The beneficial effects of using cornflower and / or aster for the remediation of petroleum-contaminated soil in this invention are: (1) High degradation rate. For petroleum-contaminated soils of 12%, 8%, and 4%, the degradation rates of petroleum in the soil by Aster tataricus were 56.94%, 84.72%, and 86.33%, respectively, while those by Cornflower were 73.89%, 79.60%, and 87.30%, respectively. This invention is superior to most existing remediation methods. Cornflower is more effective than Aster tataricus.

[0017] (2) High ornamental value. Cornflowers and asters have beautiful flowers and large biomass. They can be planted in oil-polluted areas to form a sea of ​​flowers, achieving the goal of oil pollution remediation while providing aesthetic enjoyment.

[0018] (3) Easy to cultivate. Cornflower and aster are preferred varieties for horticultural planting. The seedling and cultivation techniques are mature and easy to promote. Attached Figure Description

[0019] Figure 1 This is a comparison chart of the germination rates of different plants under different concentrations of petroleum pollution in Example 1 of the present invention.

[0020] Figure 2 The degradation rates of Aster tataricus, Cornflower, and Black-eyed Susan in different petroleum-contaminated soils in Example 1 of this invention are shown. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. All quantitative experiments in the following examples were performed in triplicate, and the results were averaged.

[0023] The cornflower in the following examples ( Cornflower L. is a variety of the genus Cornflower in the family Asteraceae, purchased from the online store Anhui Fuyang Xiangcaowu Horticulture.

[0024] The aster in the following examples ( Tatarian aster L. f. is a plant variety of the genus Aster in the family Asteraceae, purchased from the online store Shanghai Yujia Garden.

[0025] Black-eyed Susans in the following examples ( Black-eyed Susan L. is a plant variety of the genus *Asteraceae* in the family Asteraceae, purchased from Beijing Garden Horticulture.

[0026] Margaret in the following embodiments ( Paris daisy This is a plant variety belonging to the genus Chrysanthemum in the family Asteraceae, purchased from Sisi Seedlings in Yancheng, Jiangsu.

[0027] The following examples of *Chrysanthemum morifolium* ( Brachyscome angustifolia A.Cunn. ex DC. is a plant variety of the genus A.Cunn. in the family Asteraceae, purchased from Zanfei Seed Industry in Yancheng, Jiangsu Province.

[0028] Example 1 Ornamental plants were screened using contaminated soil with a 12% petroleum content. The remediation capacity of the plants was characterized by germination rate and soil petroleum degradation rate. The specific experimental process is as follows: From 2024 to 2025, preliminary and formal experiments were conducted in the laboratory of the East Campus of China University of Petroleum (Beijing). The soil used in the formal experiment was soil with different degrees of petroleum contamination, and the oil content was found to be 4%, 8%, and 12% (84g / 700g), respectively.

[0029] Various plants to be screened were planted on soils with different degrees of oil contamination. The specific plants to be screened were: Aster, Cornflower, Black-eyed Susan, Marguerite, and Dwarf Daisy.

[0030] 1. Preliminary Experiment: Direct seed planting: 25 fresh seeds of each plant species to be screened (Aster, Cornflower, Black-eyed Susan, Marguerite, and Dwarf Daisy) were selected and placed in plastic cups containing soil with petroleum content of 0%, 3%, 6%, 9%, 12%, and 15%, respectively. The mouths of the plastic cups were covered with newspaper to keep them moist and warm, and several small holes were poked for ventilation. A germination rate planting experiment was conducted for 42 days, with appropriate watering provided daily to keep the soil moist.

[0031] Germination rate was calculated, and the results are shown in [the original text]. Figure 1 According to Table 1, Aster, Cornflower, and Black-eyed Susan had higher germination rates and were selected for the formal experiment.

[0032] Table 1. Significance Test Levels for Germination Rate

[0033] Note: The average value of each group in the homogeneous subset will be displayed. a. Using the harmonic mean, sample size = 6.000.

[0034] 2. Formal Experiment: 1) Seedling transplanting: Experiments were conducted using soils with different levels of petroleum contamination. The petroleum content of the soils was found to be 4%, 8%, and 12% (84g / 700g), respectively.

[0035] Twelve seedlings of each of the selected plant species (Aster, Cornflower, and Black-eyed Susan) of similar size, weight, growth, and health, and free from pests, were selected for experiments with petroleum concentrations of 0%, 4%, 8%, and 12%. Each concentration experiment was conducted in triplicate. One plant was planted in each pot, with the soil removed from the root surface before transplanting. Each plant was then placed in a pot containing oil-containing soil. Temperature and light were managed according to the plant's specific light and light preferences, as detailed below: Aster: Prefers full sun to partial shade, cold-resistant (can overwinter at temperatures above -15℃).

[0036] Cornflower: Prefers full sunlight and is cold-hardy (can overwinter at temperatures above -10℃). High temperatures (>30℃) may affect flowering.

[0037] Black-eyed Susan: Prefers full sunlight, drought-tolerant, and extremely cold-hardy.

[0038] 2) Water and fertilizer management Watering: Keep the soil moist but not waterlogged. Increase watering appropriately during dry summer months.

[0039] Fertilization: Mix in well-rotted organic fertilizer or slow-release fertilizer before sowing.

[0040] During the growing season, apply diluted liquid fertilizer (such as fish fertilizer or compound fertilizer) every 2-3 weeks.

[0041] 3) Degradation effect determination After 70 days of flower cultivation, the soil petroleum degradation rate was tested using an extraction method, as follows: Roll filter paper soaked and dried in dichloromethane into a cylindrical sleeve and tie it tightly with thread. Place soil samples from flowerpots into the sleeve one by one. Place the sleeve into the extraction tube containing dichloromethane, ensuring the top end covers the soil sample but does not exceed the siphon tube. Connect the bottom end to a round-bottom flask containing pure dichloromethane. Plug the top end with a wad of cotton soaked and dried in dichloromethane. Siphon for several hours until the solution color no longer changes. Remove the solution from the round-bottom flask and transfer it to a weighing bottle. Let it stand for one day to allow the dichloromethane to completely evaporate. Weigh the total mass of the petroleum hydrocarbons and the weighing bottle.

[0042] The degradation rate was calculated using the gravimetric method according to Formula 1: Formula 1 Test results are shown Figure 2 Table 2 shows that both cornflower and aster have highly efficient remediation capabilities for petroleum-contaminated soil. For petroleum-contaminated soils with concentrations of 12%, 8%, and 4%, the degradation rates of petroleum in the soil by aster were 56.94%, 84.72%, and 86.33%, respectively, while the degradation rates by cornflower were 73.89%, 79.60%, and 87.30%, respectively. This invention surpasses most existing remediation methods. Cornflower is more effective than aster.

[0043] Table 2. Comparison of the significance level of degradation rate of different plant rhizospheres at different concentrations

[0044] Note: The average value of each group in the homogeneous subset will be displayed. a. Using the harmonic mean, sample size = 3.000.

[0045] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.

Claims

1. A method for phytoremediation of petroleum-contaminated soil, characterized by: The method includes the step of planting cornflowers and / or aster on oil-contaminated soil for soil remediation.

2. The method according to claim 1, characterized in that: The seeds of the cornflower and / or aster are sown directly onto oil-contaminated soil.

3. The method according to claim 1, characterized in that: The cornflowers and / or asters were first cultivated as seedlings and then transplanted onto petroleum-contaminated soil.

4. The method according to any one of claims 1-3, characterized in that: The oil-contaminated soil refers to soil with an oil mass percentage higher than 0%.

5. The method according to any one of claims 4, characterized in that: The oil-contaminated soil refers to soil with an oil content of 4-12% by mass.

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