Method for planting vegetables by combining soil conditioner and heavy metal soil

Abstract

The invention relates to a method for planting vegetables by combining a soil conditioner and heavy metal soil. The method for planting the vegetables by combining the soil conditioner and the heavy metal soil comprises the following steps: mixing a compound fertilizer, the soil conditioner and the heavy metal soil for planting the vegetables, so that heavy metals in the soil can be retained in the soil, the content of the heavy metals in the vegetables can be reduced, and the growth of the vegetables can be promoted; the soil conditioner is composed of dredged sediment and a conditioner. The conditioner is selected from at least one of biomass charcoal, iron powder, bacillus subtilis and humic acid; heavy metal in the heavy metal soil at least comprises nickel and chromium. According to the method, the problem that secondary pollution is easily caused by existing dredged sediment is solved, and meanwhile the problem that existing cultivated land pollution exceeds the standard is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of vegetable planting, and in particular to a method for planting vegetables by combining a soil improver with heavy metal soil. Background Art

[0002] Sediment is a significant factor affecting lake water quality. It deposits a variety of substances in the water and plays a vital role in lake ecosystems. Sediment in many water bodies is contaminated to varying degrees. Extensive research has been conducted both domestically and internationally on the treatment of contaminated sediment, primarily focusing on in-situ treatment techniques, including in-situ passivation, sediment solidification, and bioremediation, and ex-situ treatment, which involves dredging contaminated sediment and then performing appropriate remediation. While in-situ treatment avoids the higher costs of ex-situ treatment, it does not reduce the total amount of pollutants in the sediment. Changes in the water environment can lead to the re-release of pollutants into the overlying water. Furthermore, the in-situ remediation process is susceptible to environmental factors and is difficult to control. Environmentally friendly dredging of sediment is primarily a technical approach used in lake pollution control. To reduce sediment contamination of river and lake water quality, dredging projects have become increasingly widespread, resulting in the generation of large amounts of dredged sludge. Dredged sediment has the physical characteristics of high yield and high water content. Furthermore, it is rich in heavy metals and persistent organic pollutants, posing a significant risk of leaching. If improperly handled, it can easily cause serious secondary pollution to the ecological environment. Furthermore, with growing awareness of ecological and environmental protection, new breakthroughs are urgently needed in the disposal of dredged sediment. Therefore, the proper disposal of the large amount of sediment generated after dredging is a critical issue that needs to be addressed.

[0003] Many arable lands are facing pollution problems. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for growing vegetables by combining a soil conditioner with heavy metal soil, so as to solve the problem that the existing dredged sediment is prone to secondary pollution, and at the same time solve the problem that the existing contaminated soil cannot be used for crop planting.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for growing vegetables by combining a soil conditioner with heavy metal soil comprises the following steps: Mixing compound fertilizer, soil conditioner and heavy metal soil and using them for growing vegetables can retain heavy metals in the soil, thereby reducing the heavy metal content in vegetables and promoting vegetable growth; the soil conditioner is composed of dredged sediment and a conditioner; the conditioner is selected from at least one of biochar, iron powder, Bacillus subtilis and humic acid; the heavy metals in the heavy metal soil include at least nickel and chromium.

[0006] According to the above technical means, compound fertilizer, soil conditioner and heavy metal soil are mixed and used to grow vegetables. The ingredients in the soil conditioner, such as biochar, iron powder, Bacillus subtilis and humic acid, can effectively fix heavy metals (such as nickel and chromium) in the soil, reduce their mobility and bioavailability, thereby reducing the absorption of heavy metals by vegetables, and thus effectively reducing the content of heavy metals in vegetables. It solves the problem that the existing dredged sediment is prone to secondary pollution, and at the same time solves the problem that the existing contaminated soil cannot be used for crop cultivation. At the same time, the addition of compound fertilizer and soil conditioner can also improve the physical structure of the soil, increase the air permeability and water retention of the soil, promote the activity of soil microorganisms, enhance the fertility of the soil, increase the nutrient supply in the soil, provide a better soil environment for the growth of vegetables, and thus effectively promote the growth of vegetables. In summary, the method of the present invention not only effectively reduces the content of heavy metals in vegetables, but also improves the soil environment and increases the nutrient supply, promotes the healthy growth of vegetables, and has significant environmental and economic benefits.

[0007] Preferably, the dredged sludge is dredged sludge from a lake; the dredged sludge has a pH value greater than 7, an organic carbon content greater than 63 g / kg, an alkaline-hydrolyzable nitrogen content greater than 134 mg / kg, an available phosphorus content greater than 12 mg / kg, an available potassium content greater than 33 mg / kg, a total copper content less than 50 mg / kg, a total nickel content less than 78 mg / kg, a total chromium content less than 94 mg / kg, and a total iron content less than 26 g / kg. Preferably, the dredged sludge has a pH value of 7.74, an organic carbon content of 63.36 g / kg, an alkaline-hydrolyzable nitrogen content of 134.75 mg / kg, an available phosphorus content of 13.08 mg / kg, an available potassium content of 33.90 mg / kg, a total copper content of 39.11 mg / kg, a total nickel content of 56.35 mg / kg, a total chromium content of 81.59 mg / kg, and a total iron content of 22.82 g / kg. Preferably, the pH value of the dredged sludge is 7.60, the organic carbon content is 75.55 g / kg, the alkaline nitrogen content is 197.93 mg / kg, the available phosphorus content is 12.92 mg / kg, the available potassium content is 38.25 mg / kg, the total copper content is 49.04 mg / kg, the total nickel content is 77.11 mg / kg, the total chromium content is 93.99 mg / kg, and the total iron content is 25.99 g / kg.

[0008] Preferably, the conditioning agent consists of iron powder, Bacillus subtilis and humic acid. Preferably, the soil conditioner consists of 1 part of dredged sediment, 0.0015-0.006 parts of iron powder, 0.0125-0.05 parts of humic acid and 0.0015-0.006 parts of Bacillus subtilis in parts by mass. Preferably, the soil conditioner consists of 1 part of dredged sediment, 0.0015 parts of iron powder, 0.05 parts of humic acid and 0.0015-0.006 parts of Bacillus subtilis in parts by mass. Preferably, the soil conditioner consists of 1 part of dredged sediment, 0.003 parts of iron powder, 0.025 parts of humic acid and 0.0015-0.006 parts of Bacillus subtilis in parts by mass. Preferably, the soil conditioner consists of 1 part of dredged sediment, 0.006 parts of iron powder, 0.0125 parts of humic acid and 0.0015-0.006 parts of Bacillus subtilis, calculated by mass.

[0009] Preferably, the conditioning agent consists of biochar, iron powder and Bacillus subtilis. Preferably, the soil conditioner consists of 1 part of dredged sediment, 0.0015-0.006 parts of iron powder, 0.0125-0.05 parts of biochar and 0.0015-0.006 parts of Bacillus subtilis in parts by mass. Preferably, the soil conditioner consists of 1 part of dredged sediment, 0.0015 parts of iron powder, 0.05 parts of biochar and 0.0015-0.006 parts of Bacillus subtilis in parts by mass. Preferably, the soil conditioner consists of 1 part of dredged sediment, 0.003 parts of iron powder, 0.025 parts of biochar and 0.0015-0.006 parts of Bacillus subtilis in parts by mass. Preferably, the soil conditioner consists of 1 part of dredged sediment, 0.006 parts of iron powder, 0.0125 parts of biochar and 0.0015-0.006 parts of Bacillus subtilis, calculated by mass.

[0010] Preferably, the biochar is selected from corn straw biochar. The number of viable bacteria per gram of the Bacillus subtilis is 100 billion. The humic acid is selected from mineral-derived potassium fulvate, and the humic acid content is ≥65%. Preferably, the pH value of the heavy metal soil is between 5 and 9, the organic carbon content is between 6 and 33 mg / kg, the alkaline nitrogen content is between 37 and 102 mg / kg, the available phosphorus content is between 5 and 49 mg / kg, the available potassium content is between 58 and 101 mg / kg, the total copper content is between 14 and 58 mg / kg, the total nickel content is between 18 and 87 mg / kg, the total chromium content is between 37 and 122 mg / kg, and the total iron content is between 16 and 39 g / kg. Preferably, the element content in the compound fertilizer is N15-P15-K15. The vegetable is pakchoi.

[0011] Beneficial effects of the present invention: The present invention relates to a method for growing vegetables using a soil conditioner in combination with heavy metal soil. Compound fertilizer, soil conditioner, and heavy metal soil are mixed and then used to grow vegetables. The ingredients in the soil conditioner, such as biochar, iron powder, Bacillus subtilis, and humic acid, can effectively fix heavy metals (such as nickel and chromium) in the soil, reducing their mobility and bioavailability, thereby reducing the absorption of heavy metals by vegetables and, in turn, effectively reducing the heavy metal content in the vegetables. Furthermore, the addition of compound fertilizer and soil conditioner can improve the physical structure of the soil, increase soil aeration and water retention, promote soil microbial activity, enhance soil fertility, increase nutrient supply in the soil, and provide a better soil environment for vegetable growth, thereby effectively promoting vegetable growth. Therefore, the method of the present invention not only effectively reduces the heavy metal content in vegetables, but also improves the soil environment and increases nutrient supply, promoting the healthy growth of vegetables. It has significant environmental and economic benefits, has important application value in solving the problem of growing vegetables in heavy metal-contaminated soil, and has widespread application value in the field of vegetable cultivation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Map of sampling points for dredged sediment from Jianhu Lake; Figure 2 This is the test result diagram of soil pH value in the experimental field; Figure 3 This is the test result of soil pH value in potted plant experiment; Figure 4 This is the test result of soil organic carbon in the experimental field; Figure 5 This is the test result of soil organic carbon in potted plant experiment; Figure 6 This is the test result of alkaline nitrogen in the experimental field soil; Figure 7 This is the test result of alkaline nitrogen in the pot test soil; Figure 8 This is the test result of available phosphorus in the experimental field soil; Figure 9 This is the test result of available phosphorus in the soil of potted plant experiment; Figure 10 This is the test result of available potassium in the experimental field soil; Figure 11 This is the test result of available potassium in the soil of potted plant experiment; Figure 12 This is the morphological result of heavy metals in the sediment-amended soil after adding different amounts of conditioners on the 7th day of the experimental field experiment; Figure 13 This is the morphological result of heavy metals in the sediment-amended soil after adding different amounts of conditioners on the 63rd day of the experimental field experiment; Figure 14 This is the result of the proportion of each form of heavy metal BCR in the soil before sowing in the pot experiment; Figure 15 This is the result of the proportion of each form of heavy metal BCR in the soil after the pot experiment was harvested; Figure 16 This is a graph showing the changes in nitrogen, phosphorus and potassium in plants after adding different amounts of conditioners in the experimental field test; Figure 17 This is a graph showing the changes in nitrogen content in plants after adding various types of conditioners in the pot experiment; Figure 18 This is a graph showing the changes in heavy metal Cu in plants under various treatments in the experimental field test; Figure 19 This figure shows the effects of different conditioning agents on the Cu content in plants in potted experiments. DETAILED DESCRIPTION

[0013] The following will describe the embodiments of the present invention with reference to preferred embodiments. Those skilled in the art will readily appreciate the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are intended only to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0014] The dredged sediments in the following examples were all taken from Jianhu Lake in Yunnan Province. The sampling points are as follows: Figure 1 shown. Figure 1 The properties of the dredged sediment from Points 1 and 2 are shown in Table 1. The biochar used in the following examples was corn straw biochar; iron powder was sourced from Daguang Welding Materials Co., Ltd.; Bacillus subtilis was used, with a viable count of 100 billion per gram; humic acid was mineral-derived potassium fulvate, with a humic acid content of ≥65%; compound fertilizer (N15-P15-K15) was used; and the cabbage varieties were Yunlong 58, a first-generation hybrid cabbage (field test) and four-season Chinese cabbage (potted). The soil properties used in the following examples are shown in Table 2.

[0015] Table 1 Properties of dredged sediment Table 2 Basic properties of the tested soil Example 1 A method for combining soil amendments with heavy metal-containing soil for vegetable cultivation includes the following steps: eight 4m x 5m rectangular plots were used as experimental plots. The soil in each plot was excavated 30 cm below the surface, lined with plastic film to prevent seepage, and then backfilled with 20 cm of soil. Foreign matter and weeds were removed. Adjacent experimental plots were separated by ridges, which were then wrapped with film. A 10 cm layer of soil amendments (as listed in Table 3) was applied to the upper surface of each experimental plot and mixed evenly with the underlying 20 cm layer of soil. One rectangular plot was left untreated and served as a blank control. Another rectangular plot was treated only with dredged sediment No. 1 and served as a control. All materials were added at once before sowing and mixed evenly using a rotary tiller (or plowing). Simultaneously, 50 kg / mu of compound fertilizer (N15-P15-K15) was applied. The sowing period for Chinese cabbage is early March, with a seed rate of 2-3 grams per square meter. Watering should be done promptly after sowing, generally every 3-5 days, to keep the soil moist for seed germination and emergence. The Chinese cabbage used in this example is the first-generation hybrid Chinese cabbage Yunlong 58; the soil used is No. 1 soil; and the soil conditioner used is composed of dredged sediment and a conditioner, with the dredged sediment being No. 1 dredged sediment. The conditioner composition and dosage are shown in Table 3.

[0016] Table 3 shows the dosage of soil conditioner Note: The dredged sediment thickness in Table 3 is the thickness of the soil amendment. The amounts of iron powder, humic acid, biochar, and Bacillus subtilis are all compared to the amount of dredged sediment. Since the amount of iron powder, humic acid, biochar, and Bacillus subtilis added has little effect on the overall thickness of the soil amendment, they are ignored.

[0017] In Table 3, F, B, T and K represent humic acid, biochar, iron powder and Bacillus subtilis, respectively, and they are the group without sediment and conditioner (CK), the group with only sediment addition (D), the group with sediment, iron powder, humic acid and Bacillus subtilis addition (T1F3, T2F2, T3F1), and the group with sediment, iron powder, biochar and Bacillus subtilis addition (T1B3, T2B2, T3B1).

[0018] Example 2 A method for growing vegetables using a soil conditioner in combination with heavy metal-containing soil comprises the following steps: 12 flower pots (specifications: upper diameter 21.5 cm, lower diameter 17.5 cm, pot height 15 cm) are filled with 2 kg of test soil for a potted experiment. The test soil is a mixture of air-dried No. 2 dredged sediment and air-dried soil at a mass ratio of 1:2. 0.5 g / kg of compound fertilizer (N15-P15-K15) is applied to each pot as a base fertilizer, and no further fertilizer is applied. The conditioner, base fertilizer, and test soil listed in Table 4 are mixed and then placed in separate pots. Air-dried soil without any sediment is used as a blank control. The moisture content of each pot is adjusted to 23%. Deionized water is added by gravimetric method once daily. After 7 days of equilibration, pakchoy seeds are evenly sown in the pots and soaked for 30 minutes to facilitate germination. Ten seeds were sown per pot. When the seeds germinated and grew to a height of approximately 2 cm, the first thinning was performed, leaving 6 plants with good growth and uniform size. When the pakchoy cabbage was approximately 5 cm tall, the second thinning was performed, leaving 3 plants per pot. The flower pots were randomly arranged during the experiment and the positions of the flower pots were rotated every two days to avoid differences in light exposure. The pakchoy cabbage used in this example was four-season pakchoy; the soil used was soil No. 2; the conditioner used and dredged sediment No. 2 together formed the soil amendment; the conditioner is shown in Table 4.

[0019] Table 4 shows the designed dosage of the conditioning agent. Note: In Table 4, the percentage of iron powder is the percentage of the amount of sediment used, the percentage of humic acid and biochar is the percentage of the amount of potting soil used, and the content of Bacillus subtilis is the percentage of the amount of potting soil used.

[0020] As shown in Table 4, a total of 12 groups were set up in the pot experiment, with 4 replicates in each group, namely, control group (CK), iron powder group (T), humic acid group (F), biochar group (B), Bacillus subtilis group (K), iron powder + biochar group (TB), iron powder + humic acid group (TF), iron powder + Bacillus subtilis group (TK), biochar + Bacillus subtilis group (BK), humic acid + Bacillus subtilis group (FK), iron powder + biochar + Bacillus subtilis group (TBK) and iron powder + humic acid + Bacillus subtilis group (TFK).

[0021] Detection and Analysis Soil sample collection and preparation: The experimental field test in Example 1 was conducted from May 3 to July 5, 2024. 0-20 cm soil was collected from each experimental field every 7 days by diagonal sampling method, and naturally air-dried. Gravel and plant and animal residues were picked out, and the soil was passed through 10-mesh, 20-mesh and 100-mesh sieves in turn and put into sealed bags. The potted experimental soil in Example 2 was collected in the early stage (September 11, 2024), mid-term (October 12, 2024) and harvest period (December 16, 2024) of the experiment. Soil samples were collected from multiple sampling points in the pot, mixed, and then naturally air-dried to remove impurities. They were passed through 10-mesh, 20-mesh and 100-mesh sieves in turn and preserved for testing. 1) Determination of soil physical and chemical properties: The method for determining soil physical and chemical properties was referred to "Soil Agrochemical Analysis" (Bao Shidan 2000). The soil pH was measured with a pH meter using a soil-water ratio of 1:2.5. The results are as follows Figure 2 and Figure 3 ; Soil organic carbon was determined by externally heated potassium dichromate oxidation method, and the results were as follows Figure 4 and Figure 5 ; Soil alkaline nitrogen was determined by alkaline diffusion method, and the results were as follows Figure 6 and Figure 7 Soil available phosphorus was determined by 0.5 mol / L sodium bicarbonate extraction-molybdenum antimony colorimetric method. The results are as follows: Figure 8 and Figure 9 Soil available potassium was determined by 1 mol / L ammonium acetate extraction-flame atomic absorption spectrometry. The results are as follows: Figure 10 and Figure 11 .

[0022] from Figure 2 As shown, the addition of soil amendments increased soil pH on day 7, and over time, the soil pH gradually decreased compared to the CK group. The addition of dredged sediment No. 1 alone significantly decreased soil pH, but the application of soil amendments increased it somewhat. Group D, which only added sediment, had the lowest pH on days 14, 28, and 49. Compared to Group D, the addition of iron powder and humic acid (T1F3, T2F2, and T3F1) increased soil pH by 0.06, 0.10, and 0.26 units, respectively, on day 63. The highest pH was achieved in Group T3F1 on days 35, 49, and 63. Compared to Group D, the addition of iron powder and biochar (T1B3, T2B2, and T3B1) significantly increased soil pH by 0.35, 0.19, and 0.22 units on day 63.

[0023] from Figure 3It was found that the addition of conditioners increased soil pH after application of Dredged Sediment No. 2. The humic acid-containing group significantly increased soil pH during the pakchoy sowing period, growth, and post-harvest. After harvest, soil pH increased by 0.43, 0.38, 0.54, and 0.45 units, respectively, compared to the CK group. The FK group showed a significantly higher improvement than the other three groups. Soil pH in the T, B, TK, TB, BK, and TBK groups was significantly higher than that in the CK group before and after sowing. Pre-sowing, pH increased by 0.10, 0.16, 0.10, 0.17, 0.16, and 0.17 units, respectively, and after harvest, by 0.15, 0.18, 0.19, 0.20, 0.20, and 0.16 units, respectively.

[0024] from Figure 4 It can be seen that the addition of dredged sediment No. 1 alone reduced the organic carbon content in the soil, while the addition of the conditioner significantly increased the soil organic carbon. The soil organic carbon content of Group D was significantly lower than that of Group CK during the experimental period. Compared with Group D, the soil organic carbon content of Groups T3F1, T1B3, T2B2, and T3B1 increased significantly and was significantly higher than that of Group CK. The soil organic carbon content of Groups T1F3 and T2F2 was significantly lower than that of Group D on the 7th and 28th days of the experiment, while that of Group T1F3 was significantly higher than that of Group D on the 14th and 63rd days of the experiment. Among the three groups with iron powder and humic acid addition, Group T3F1 had the highest organic carbon content, while among the three groups with iron powder and biochar addition, Group T1B3 had the highest organic carbon content.

[0025] from Figure 5 It can be seen that before sowing, the addition of conditioners increased the content of organic carbon in the soil. The TB group had the highest soil organic carbon content, which increased by 41.17% compared with the CK group. During growth, the T, K, and FK groups significantly reduced the organic carbon content in the soil. After harvest, the F and B groups significantly increased the soil organic carbon content by 23.14% and 31.05%, respectively. Among the two conditioners, the organic carbon content of the TF, TB, BK, and FK groups was significantly higher than that of the CK. The organic carbon content of the TFK and TBK groups, which were applied with all three conditioners, was also significantly higher than that of the CK treatment.

[0026] from Figure 6 It can be seen that the addition of dredged sediment No. 1 significantly reduced the alkaline nitrogen content in the soil. The alkaline nitrogen content of the soil in group D was significantly lower than that in group CK on the 7th and 63rd days. The addition of conditioners increased the alkaline nitrogen content in the soil compared to the treatment with only dredged sediment No. 1. The alkaline nitrogen content of group T1B3 was significantly higher than that of group D on the 7th, 28th, 35th, 49th and 63rd days of the experiment, and was significantly higher than that of group CK on the 49th day. The alkaline nitrogen content of groups T2B2 and T3B1 was significantly lower than that of group CK on the 7th, 14th, 35th and 63rd days. The alkaline nitrogen content of group T3F1 was significantly higher than that of group D on the 28th and 35th days.

[0027] from Figure 7 It can be seen that the addition of conditioners before sowing significantly increased the content of alkaline-hydrolyzable nitrogen in the soil. The alkaline-hydrolyzable nitrogen content in the T and F groups was significantly higher than that in the CK group, increasing by 23.01% and 56.43%, respectively. The alkaline-hydrolyzable nitrogen content in the TF group was significantly higher than that in the T group. The alkaline-hydrolyzable nitrogen content in the B and K groups was higher than that in the CK group, while the alkaline-hydrolyzable nitrogen content in the BK group was significantly higher than that in the CK group. The alkaline-hydrolyzable nitrogen content in the TFK group was significantly lower than that in the TF group but higher than that in the K group.

[0028] from Figure 8 As shown, the addition of soil amendments on the 7th day of the experiment significantly reduced the available phosphorus content in the soil compared to the CK. The available phosphorus content in the T3F1, T1B3, T2B2, and T3B1 groups was significantly lower than that in the D and CK groups. As the experiment progressed, the available phosphorus content in the D group gradually became significantly higher than that in the CK group after the 35th day. The available phosphorus content in the T3F1, T1B3, T2B2, and T3B1 groups remained lower than that in the CK group throughout the experiment. On the 7th day of the experiment, the T2F2 group significantly increased the available phosphorus content in the soil compared to the D group. After the 35th day of the experiment, the available phosphorus content in the T1F3 and T2F2 groups was significantly lower than that in the D group. On the 49th day of the experiment, the alkaline nitrogen content in the T1F3 and T2F2 groups was significantly higher than that in the CK group.

[0029] from Figure 9 It can be seen that before sowing, the TBK group significantly reduced the content of available phosphorus in the soil compared with the CK group. The content of available phosphorus in the soil was significantly reduced after the combination of iron powder, biochar and Bacillus subtilis. The content of available phosphorus in the TBK group was significantly lower than that in the T, B, K, TB, TK and BK groups. During the growth period, the addition of conditioners significantly reduced the available phosphorus in the soil. Except for the B, TK and BK groups, the available phosphorus content was not significant compared with the CK, the other groups were significantly lower than the CK. The available phosphorus content in the TK group was significantly increased compared with the T and K groups, and was also significantly higher than the TFK and TBK groups. After harvest, the BK group significantly increased the available phosphorus content in the soil, and the available phosphorus content in the soil of T, FK, TFK and TBK was significantly lower than that of the CK group. The available phosphorus content in the soil after the combination of the three conditioners was significantly lower than that after single application and the combination of the two.

[0030] from Figure 10 It can be seen that the available potassium content in the soil in the experimental field experiment first increased and then decreased with time. The addition of conditioners will reduce the available potassium content in the soil improved by dredged sediment at Site 1. The available potassium content in the T1F3 and T2F2 groups was significantly lower than that in the CK and D groups on the 7th day of the experiment, and significantly lower than that in the D group on the 14th day. The available potassium content in the T3F1 treatment was significantly lower than that in the CK and D groups on the 28th and 35th days, and significantly lower than that in the D group on the 14th and 49th days of the experiment. The available potassium content in the T1B3, T2B2, and T3B1 groups was significantly lower than that in the D group on the 7th, 14th, 35th, and 49th days of the experiment. On the 63rd day of the experiment, the available potassium content in the T1B3 group was the lowest.

[0031] from Figure 11 It can be seen that the available potassium content in the potted soil gradually increased with the extension of the experimental time. Before sowing, the available potassium content of the CK group, which only added the dredged sediment from site 2, was the highest. The addition of the conditioner reduced the available potassium content in the soil improved by the sediment. During the growth period, the available potassium content of the soil improved by the dredged sediment from site 2 did not increase significantly after the addition of the conditioner. The available potassium content of the T, F, TF, and TFK groups was significantly lower than that of the CK group, decreasing by 13.81%, 25.02%, 20.44%, and 20.54% compared with CK. The available potassium content of the K group was significantly higher than that of the T, F, TF, FK, and TFK groups.

[0032] 2) Determination of heavy metal content in soil (1) Determination of total heavy metal content in soil: Use hydrochloric acid, nitric acid, hydrofluoric acid, and perchloric acid to digest the soil, and determine it by inductively coupled plasma optical emission spectrometry (ICP-OES). Weigh 0.2-0.3g (accurate to 0.1mg) of sample into a polytetrafluoroethylene crucible, moisten it with a small amount of water, add hydrochloric acid, and heat at 100℃ to initially decompose the sample. When the digestate evaporates to about 3mL, add 9mL of nitric acid and continue heating until there are no obvious particles. Add 5mL of hydrofluoric acid and heat at 120℃ for 30min. After cooling slightly, add 2mL of perchloric acid and heat at 170℃ until white smoke appears. When the content appears to be a non-flowing liquid droplet, add 3mL of nitric acid solution (1+99), dissolve the soluble residue with warm water, transfer the entire amount to a 25mL volumetric flask, and adjust the volume with nitric acid solution. After adjusting the volume, filter the solution with a 0.45μm filter membrane into a 10mL centrifuge tube for determination. (2) Determination of soil heavy metal forms: The BCR extraction method was used to determine the forms of heavy metals in the soil. The heavy metals in the soil were divided into weak acid extraction state, reducible state, oxidizable state and residual state. The specific determination method is as follows: Weak acid extraction state: Weigh 0.5g (accurate to 0.1mg) of soil sample into a 50mL centrifuge tube, add 20mL of 0.11mol / L acetic acid solution, shake while adding, cover the lid and extract at 200r / min at 25℃ for 16h. After the shaking is completed, centrifuge at 4000r / min for 15min, and take the supernatant for determination. Add 15mL of ultrapure water to the centrifuge tube containing the residue, cover the lid and shake, shake at 200r / min for 15min, and then centrifuge at 4000r / min for 15min. Discard the washing solution and the residual sample in the centrifuge tube for the next extraction. Reducible Form: Add 20 mL of 0.5 mol / L hydroxylamine hydrochloride solution to the centrifuge tube containing the solid residue sample from the previous step. Shake well while adding. Cover and extract at 200 rpm at 25°C for 16 h. Centrifuge at 4000 rpm for 15 min. Filter the supernatant through a 0.45 μm filter into a 50 mL volumetric flask and bring to volume for analysis. Add 15 mL of ultrapure water to the centrifuge tube containing the residue, cover and shake well. Shake well at 200 rpm for 15 min, then centrifuge at 4000 rpm for 15 min. Discard the wash solution and use the remaining sample in the centrifuge tube for the next extraction. Oxidizable Form: Add 5 mL of hydrogen peroxide to the centrifuge tube containing the solid residue sample from the previous step. Cover but loosely cap. Digest at room temperature for 1 h, shaking manually every 10 min. Continue digestion in an 85°C water bath for 1 h, shaking manually every 10 min. Uncover and heat until the volume is less than 3 mL.Remove the centrifuge tube and cool it. Slowly add 5mL of hydrogen peroxide, lightly cover the lid, and digest in an 85°C constant-temperature water bath for 1 hour. Uncover and continue heating until the volume reaches approximately 1mL. Remove and cool. After cooling, add 25mL of 1mol / L ammonium acetate solution (adjust the pH to 2 with HNO3), shake well, cover, and extract at 25°C with shaking at 200r / min for 16 hours. After shaking, centrifuge at 4000r / min for 15 minutes. Filter the supernatant through a 0.45μm filter membrane and transfer it to a 50mL volumetric flask, bringing it to volume for analysis. Residual state: The residual state content is calculated by subtracting the weak acid extractable, reducible, and oxidizable states from the total amount of heavy metals measured. The results are as follows. Figures 12 to 15 shown.

[0033] from Figure 12 As can be seen, the weakly acid-extractable Cu content was extremely low, with the T2F2 group having the highest proportion of weakly acid-extractable Cu at 2%. Compared to CK, the addition of dredged sediment No. 1 significantly increased the content of reducible Cu, with the proportion of reducible Cu in Group D increasing by 5%. Group T1B3 transformed weakly acid-extractable and reducible Cu into oxidizable and residual states. Group T1B3 significantly reduced the content of reducible Cu to less than 1% of the total, while significantly increasing the content of oxidizable and residual Cu. The remaining groups all had higher reducible Cu content and lower residual Cu content than CK. Similar to Cu, the T1B3 group also significantly reduced the content of weakly acid-extractable and reducible Ni, shifting it toward oxidizable and residual states. The weakly acid-extractable Cr content was extremely low, with the oxidizable and residual states accounting for over 92%. Group T1B3 transformed reducible and residual Cr into oxidizable Cr, with the proportion of oxidizable Cr reaching 83%. Iron in soil exists primarily in reducible and residual forms, with weakly acid-extractable and oxidizable forms accounting for less than 1%. The T1B3 group converted reducible Fe into residual Fe, reducing the proportion of reducible Fe by 11% and increasing the proportion of residual Fe by 10%.

[0034] from Figure 13The addition of Dredged Sediment No. 1 increased the contents of weakly acid-extractable and reducible Cu in the soil. In Group D, weakly acid-extractable Cu accounted for 2%, and reducible Cu increased by 4%. Groups T1F3 and T2F3 shifted Cu from residual to reducible forms, while Group T3F1 showed no such shift. Group T1B3 exhibited the lowest Cu activity, with oxidizable and residual forms accounting for 99%. Ni activity in soils amended with Dredged Sediment No. 1 and conditioners was lower than in Group CK, with a significant increase in the proportion of residual Ni. The residual Ni content in Group T2B2 increased by 10% compared to Group CK. The content of oxidizable Ni in Group T1B3 was significantly higher than in Group CK, while the application of other conditioners reduced oxidizable Ni in the soil. Cr in the soil was primarily present in the residual form. Group T1B3 significantly reduced the content of reducible Cr, and the residual Cr content also decreased by 8% compared to Group CK, while the oxidizable Cr content increased by 11%. Fe in the soil exists primarily in two forms: reducible and residual. The T1B3 group shifted the reducible form to the residual form, with the residual Fe accounting for 98%. The addition of dredged sediment No. 1 and conditioning agent increased the proportion of reducible Fe in the soil and correspondingly decreased the proportion of residual Fe.

[0035] from Figure 14 Before sowing, the heavy metals Cu, Ni, Cr, and Fe were not highly active and existed primarily in a residual form. The residual form of Cr accounted for over 93% of the total, and the residual form of the other heavy metals also accounted for over 70%. The weakly acid-extractable form of Cu was approximately 1% in all groups except the K group. The reducible form increased by 3% in the T group and decreased by 3% in the FK group. For the heavy metal Ni, the oxidizable form increased by 2% in the K group and by 2% in the TB group. The weakly acid-extractable form of Cr was extremely low, less than 1% of the total, but the addition of a soil conditioner increased the oxidizable form. Both the weakly acid-extractable and oxidizable forms of Fe accounted for less than 1% of the total, while the reducible and residual forms of Fe in the soil accounted for over 99% of the total. The addition of a soil conditioner increased the reducible Fe content, with increases of 7%, 11%, 6%, 6%, 9%, and 7% in the T, TF, TK, TFK, and TBK groups, respectively.

[0036] from Figure 15It can be seen that the activity of heavy metals Cu, Ni, Cr and Fe is still not high after harvest, and the proportion of residual content in the total is above 76%, 71%, 92% and 84% respectively. The weak acid extractable content of Cu accounts for about 1%; the proportion of reducible Cu is greatly affected by the conditioning agent. The addition of humic acid can reduce the content of reducible Cu, which is mainly converted into residual Cu. For heavy metal Ni, the proportion of weak acid extractable in treatment B increased by 2% compared with treatment CK; the proportion of reducible Ni in each group was about 12%; the addition of iron powder converted oxidizable Ni into residual Ni. The oxidizable Ni in groups T, TF, TK, TB, TFK and TBK was lower than that in group CK, and the corresponding residual content increased. The weak acid extractable content of Cr is extremely low, and it mainly exists in the residual state. The weak acid extractable and oxidizable content of Fe are extremely low. The addition of iron powder as a conditioning agent increases the proportion of reducible Fe and reduces the proportion of residual Fe.

[0037] (2) Determination of plant indicators: In both Examples 1 and 2, the cabbage was uprooted and separated into the aboveground part and the underground part when it was harvested. After the cabbage was harvested, the total height of the plant was measured with a ruler and regarded as the plant height, and the length of the widest part of the plant was measured and regarded as the plant width. Fresh weight: After the plant samples were collected, they were washed with deionized water, the surface moisture of the plant was absorbed by filter paper, and the aboveground part and the underground part were weighed separately using an electronic balance. Dry weight: The cabbage was placed in a drying oven, blanched at 105°C for 30 minutes, and then dried at 75°C to constant weight. The dry weight of the aboveground part and the underground part was weighed separately. Chlorophyll (SPAD): The chlorophyll content was measured using a chlorophyll content meter. The results are shown in Tables 5 and 6.

[0038] Table 5 shows the plant height, plant width, biomass and SPAD values ​​of the experimental plants in the experimental field Table 5 shows that the addition of Dredged Sediment No. 1 significantly increased plant height, plant width, biomass, and SPAD values. The plant width, biomass, and SPAD values ​​of the group that added iron powder and humic acid to the Dredged Sediment No. 1-amended soil were significantly different from those of the CK and D groups. Adding iron powder and biochar to the Dredged Sediment No. 1-amended soil promoted plant growth.

[0039] Table 6 shows the plant height, plant width, biomass and SPAD values ​​of the potted plants Table 6 shows that among the four groups treated with only one conditioner, group K significantly increased aboveground biomass, group B significantly increased plant width and aboveground biomass by 24.30% and 101.48%, respectively, and group F significantly reduced the SPAD of the plants compared to the CK group. Among the groups treated with two conditioners, group TF significantly increased plant height by 23.66% and significantly decreased SPAD compared to the CK group. Group TB significantly increased plant height, plant width, and biomass by 89.25%, 94.38%, and 223%, respectively, compared to the CK group. Both groups BK and FK increased plant biomass compared to the CK group, with the BK group also significantly increasing plant width compared to the CK group. The TBK and TFK groups, treated with three conditioners, had significant effects on plant growth. The TBK group showed significantly higher plant height, plant width, and aboveground biomass than the CK group, with increases of 21.51%, 34.54%, and 53.33%, respectively. The plant height, plant width and biomass of the TFK group increased significantly by 65.46% and 117% compared with those of the CK group. The plant height, plant width and biomass of the TB group were the highest and significantly higher than those of the other groups.

[0040] Determination of nitrogen, phosphorus and potassium content in plants: Weigh about 0.2000g of plant sample and place it at the bottom of a 50mL digestive tube. Moisten it with a small amount of ultrapure water and add 5mL of concentrated sulfuric acid. Shake gently and let it stand overnight. Preheat to 160℃ until the sulfuric acid emits white smoke, then increase the temperature. When the solution is uniform brown-black, remove it and cool it slightly. Add 6 drops of H2O2 and boil it for 15 minutes. Remove it and cool it slightly, and continue to add 6 drops of H2O2 to boil it. Repeat this several times. The amount of H2O2 added is gradually reduced until the solution becomes colorless or clear. Continue heating for 10 minutes to remove the remaining H2O2, remove it and cool it. After cooling to room temperature, adjust the volume to 50mL, filter it and store it for testing. Use a flow analyzer to determine the total nitrogen and total phosphorus of the filtrate, and a flame atomic absorption spectrometer to determine the total potassium. The test results are as follows: Figure 16 and Figure 17 shown.

[0041] from Figure 16 (a) It can be seen that the addition of soil amendments affected the nitrogen content in plants. The nitrogen content of plants in the T1F3 and T2F2 groups was 22.53% and 24.92% higher than that in the CK group, respectively. The nitrogen content in plants in the T1B3 group was the highest. Figure 16 (b) It can be seen that the total phosphorus content of plants changed after the addition of soil amendments. The phosphorus content in the plants of group T1B3 was the highest, increasing by 49.08% compared with the CK group and 25.76% compared with the D group. The phosphorus content of plants in groups D, T1F3, T2F2, T3F1, and T3B1 was higher than that in the CK group. Figure 16(c) As shown, the addition of Dredged Sediment No. 1 increased plant potassium content. The T3F1 group significantly increased plant potassium content, achieving the highest level among all groups, with a 33.38% increase compared to the CK group. Plant potassium content significantly decreased in the groups treated with iron powder and biochar, with the T2B2 treatment having the lowest plant potassium content. Plant potassium content in the T1B3 and T2B2 groups was 13.43% and 30.65% lower than in the CK group, respectively.

[0042] from Figure 17 (a) It can be seen that the nitrogen content of plants decreased after the addition of the conditioner, and the nitrogen content of plants in the iron powder group was lower than that of the control group. The nitrogen content of plants in the T, TF, TK, TB and TBK groups was 22.46%, 20.87%, 23.70%, 16.92% and 16.63% lower than that of the CK treatment, respectively. The nitrogen content of plants in group B was 19.10% lower than that of the CK treatment. Figure 17 (b) It can be seen that the total phosphorus content of the plants in the group containing humic acid was higher than that of the control. The total phosphorus content of the plants in the F, TF, FK and TFK groups was 15.58%, 62.61%, 67.83% and 26.09% higher than that in the CK group, respectively. The phosphorus content of the plants in the groups after the application of iron powder and other conditioning agents was higher than that in the group with iron powder alone. The phosphorus content of the plants in the T group decreased by 26.09% compared with the CK group. Figure 17 (c) As shown, the CK group had the highest plant potassium content in the experiment, and the addition of the conditioning agents reduced the total potassium content in the plants to varying degrees. Except for the K group, the potassium content of the conditioning agent alone and the TF group was lower than that of the other two conditioning agent combination groups and the TFK group. The F and TF groups had the lowest potassium content. The FK and TFK treatments had higher potassium contents than the T, F, and TF groups, but there was no significant difference between them. The K and TB groups had potassium contents second only to the CK group, and the TBK group had a lower potassium content than the K and TB groups.

[0043] The heavy metal content in plants was digested using mixed acid (HNO3:HClO4). Weigh 0.2000 g of sample (accurate to 0.0001 g) into a 50 mL conical flask, add 10 mL of mixed acid (HNO3:HClO4 = 9:1), shake well and place overnight, then digest at 180 ° C for 5 hours, adding mixed acid appropriately during the digestion until the sample is digested to colorless and transparent. After the digestion is completed, cool to room temperature and transfer the digestion solution to a 50 mL volumetric flask. Rinse the conical flask with deionized water in small amounts several times to the scale line, shake well and filter with a 0.45 μm filter membrane for testing. The results are as follows Figure 18 and 19 shown.

[0044] from Figure 18 (a) It can be seen that the application of the conditioner increased the copper content in the plants. The copper content in the plants of the T2F2, T3F1 and T2B2 groups increased significantly by 25.15%, 28.12% and 28.31% respectively compared with the CK treatment. Figure 18 (b) It can be seen that the Ni content in plants did not increase significantly after the addition of dredged sediment No. 1. After the simultaneous application of the conditioning agent iron powder, humic acid and dredged sediment No. 1, the Ni content in plants showed two changes. The Ni content in the T2F2 group decreased by 87.35% compared with the CK group, and the Ni content in the T3F1 group increased by 128.97% compared with the CK group. Among the groups with biochar added, the Ni content in the plants in the T1B3 and T3B1 groups was significantly reduced compared with the CK and D groups. Figure 18 (c) It can be seen that the Cr content in plants after the addition of No. 1 dredged sediment was not significantly different from that in the CK group. The addition of the conditioner significantly reduced the Cr content in plants. The Cr content in plants in the T2F2, T1B3, and T3B1 groups was significantly reduced compared to the CK group, with the T2F2 group having the lowest Cr content. Figure 18 (d) It can be seen that the Fe content in the plants of group D was 179.00% higher than that of group CK. After the application of iron powder and other conditioning agents, the Fe content in the plants of group T1F3 was significantly higher than that of group CK by 155.38%.

[0045] from Figure 19 (a) It can be seen that the Cu content of plants in groups T, K and B, which were treated with a single conditioner, was lower than that in group CK. The Cu content of plants in group F was higher than that in group CK. The Cu content of plants in groups TF and FK was higher, and the Cu content of group FK was higher than that of groups F and TF. The Cu content of plants in groups B, TB and TBK was significantly lower than that in group CK and other conditioner groups. The Cu content of plants in groups treated with two or three conditioners was significantly lower than that in group CK. Figure 19 (b) It can be seen that the Ni content in the plants of the K and B groups was significantly reduced. The Ni content in the plants further decreased significantly after the two were applied together. The Ni content in the BK group decreased by 43.86% compared with the CK group, and decreased by 16.20% and 18.02% compared with the K and B groups, respectively. The TFK group made the Ni content in the plants significantly lower than that of the F, TF, FK and CK groups. The Ni content in the TB group was significantly lower than that of the T and B groups that were applied with the conditioner alone, and the Ni content was the lowest. Figure 19 (c) It can be seen that the Cr content of plants in the F, TF and FK groups was higher than that in the CK group, while the Cr content of plants in the TFK group was lower than that in the CK, F, TF and FK groups. Compared with the CK group, the T and B groups increased and decreased the Cr content in plants, respectively. The TB group made the Cr content in plants lower than that in the CK group and the content was the lowest. Both the B and K groups reduced the Cr content in plants. The Cr content in the BK group, which was a combination of the two, was significantly lower than that in the B and K groups. The TBK group made the Cr content in plants significantly lower than that in the CK group, but significantly increased compared with the TB group. Figure 19(d) As shown, the effects of the F, TF, and FK groups on plant Fe content were similar to those of the Cu, Ni, and Cr groups, all resulting in higher Fe content in plants than in the CK group, with the FK group having the highest Fe content. The Fe content in the TFK group was lower than in the CK group and also lower than in the other groups supplemented with humic acid. In the treatments where the conditioning agent was applied alone, the T, K, and B groups all significantly reduced Fe content in plants, with the order T>K>B being significantly different among the three groups. The Fe content in the TK group was lower than in the T and CK groups, but higher than in the K group. The Fe content in the TB and BK groups was lower than in the T, B, and K groups, and also lower than in the CK group. The Fe content in the TBK group was higher than in the TB and BK groups, but lower than in the T and CK groups.

[0046] 3) Heavy metal stability: I R Represents heavy metal stability, I R The higher the value, the stronger the binding of heavy metals to the soil, and the less likely it is for plants to absorb it. The calculation formula is shown in Formula I: In formula I: i represents the number of consecutive extractions (i=1, 2, 3, 4); F i represents the relative content of the i-th form of the heavy metal element; k = 4. The heavy metal stability results of each group on the 63rd day of the experimental field test are shown in Table 7.

[0047] Table 7 Results of soil heavy metal stability after the experimental field test As shown in Table 7, the stability of Cu in the T3F1 group increased from 0.7740 to 0.8046 compared with the D group. The T1B3, T2B2 and T3B1 groups improved the stability of Cu in the soil after the addition of No. 1 dredged mud. Among them, the stability of Cu in the T1B3 group was the highest. Compared with the CK group, R The value increased from 0.8158 to 0.9087. Adding conditioners can improve the stability of Ni in soil. Compared with the CK group, the stability of Ni in other groups is higher, and the stability of Ni in the T1B3 group is the highest. The I value of Ni in the T1F3 and T2F2 treatments is higher than that in the T3B1 group with biochar added. R The values ​​were similar. Overall, the combination of iron powder and biochar was more conducive to Ni stabilization. The stability of Cr in the soil reached above 0.9. The stability of heavy metals in the soil after harvest in the pot experiment is shown in Table 8.

[0048] Table 8 Results of soil heavy metal stability after pot experiment As shown in Table 8, the addition of humic acid can enhance the stability of Cu in soil. RThe value was higher than that of CK group. The stability of Cu in soil was the highest in FK group, followed by F group. Adding iron powder and humic acid could improve the stability of Ni in soil. R The values ​​increased from 0.8172 to 0.8306 and 0.8331. R The values ​​were higher than those in the CK group. Among them, the stability of Ni in the soil of the TFK group was the highest. The stability of Cr in the soil was greater than that of Cu and Ni.

[0049] 4) THQ (target hazard quotient) is used to assess the health risks of consuming vegetables. A THQ value less than 1 indicates no significant health risk to humans, while a THQ value greater than 1 indicates a potential health risk. Higher THQ values ​​increase the risk. When multiple contaminants are present, the total target hazard quotient (TTHQ) can be used for assessment.

[0050] The relevant standards for heavy metals in vegetables are calculated based on fresh weight. The heavy metal content of vegetables in this article is calculated based on dry weight. Therefore, the heavy metal content is converted according to the water content of the vegetables before health risk assessment. The conversion formula is shown in Formula II: ; In formula II: W f represents the mass fraction of heavy metals in fresh vegetables (mg / kg); W d represents the mass fraction of heavy metals in the dried sample (mg / kg); r represents the moisture content of the vegetable.

[0051] The calculation formulas for THQ and TTHQ are as follows: ; ; In formula III: EF r is the exposure frequency, 365 d / a; ED is the exposure years, which is 70 years based on the average human lifespan; FIR is the vegetable intake rate (g / d), which is 230 g for children (3-12 years old), 345 g for young adults (14-45 years old), and 375 g for the middle-aged and elderly (> 45 years old) according to age; C is the heavy metal content in vegetables (mg / kg); R f D is the oral reference dose, Cu, Ni and Cr are 4×10 -2 , 2×10 -2 and 3×10 -2mg / (kg·d); BW is average body weight (32 kg for children, 60 kg for young adults, and 58 kg for the elderly); AT is the average duration of non-carcinogenic exposure, ED × 365 days. In Formula IV, TTHQ ≤ 1 indicates no significant adverse effects on humans; TTHQ > 1 indicates a high likelihood of adverse effects; and TTHQ > 10 indicates the presence of chronic toxic effects on human health.

[0052] The data used in this article were collated using Microsoft Excel 2019, and IBM SPSS Statistics 19 software was used for statistical analysis of significant differences. The Ducan multiple comparison method was used for significance analysis. The significance mentioned in the article is P <0.05, Spearman was used for correlation analysis, and Origin Pro 2022 software was used for graphics.

[0053] To assess whether heavy metals in sediment-amended soil would enter vegetables through root absorption and accumulate in the edible parts of vegetables, thereby threatening human health, the THQ and TTHQ values ​​of heavy metal intake through vegetables for children, young adults, and middle-aged and elderly people were calculated according to formulas (III) and (IV). The calculation results are shown in Table 9.

[0054] Table 9 Human health risk assessment of vegetables treated in the experimental field test Table 9 shows that the THQ and TTHQ values ​​for individual heavy metals, Cu, Ni, and Cr, were all less than 1 for children, young adults, and middle-aged and elderly people, indicating that vegetables grown in soils amended with sediment do not pose a significant health risk. TTHQ values ​​for heavy metals in vegetables across different populations were highest in children and lowest in young adults. The TTHQ values ​​for each treatment followed the order T3F1 > CK > T1F3 > D > T2B2 > T1B3 > T3B1 > T2F2. Among the three population groups, vegetables in the T3F1 group had the highest TTHQ values ​​(0.3044 for children, 0.2435 for young adults, and 0.2738 for middle-aged and elderly people, respectively). Vegetables in the T2F2 group had the lowest TTHQ values ​​(0.0573 for children, 0.0459 for young adults, and 0.0516 for middle-aged and elderly people, respectively). By comparing the THQ values ​​of various heavy metals in vegetables under different treatments, it was found that the THQ values ​​of vegetables in CK, D, T1F3 and T2B2 groups were Cr>Ni>Cu, among which the THQ values ​​of Cu, Ni and Cr in T2B2 group were the lowest; the THQ values ​​of vegetables in T1B3 and T3B1 groups were Cr>Cu>Ni, among which the THQ values ​​of Cu, Ni and Cr in T3B1 group were even lower; the THQ values ​​of vegetables in T2F2 group were Cu>Cr>Ni; and the THQ values ​​of vegetables in T3F1 group were Ni>Cr>Cu. Effects of sediment and conditioners on soil properties These results indicate that mixing dredged sediment with soil not only increases soil organic matter and nutrient content, but also significantly reduces pH, alkaline-hydrolyzable nitrogen, organic carbon, and available potassium compared to farmland soil. The organic carbon and alkaline-hydrolyzable nitrogen contents in the sediment were higher than those in the experimental farmland soil.

[0055] The results of the pot experiment showed that adding iron powder, humic acid and biochar to the mixed sediment soil can significantly increase the soil pH. After the iron powder is added, it reacts chemically with H2O and O2 in the soil to generate Fe (III), which releases OH - This increases the soil pH. Biochar is alkaline and contains a large amount of carbonates, organic anions, and inorganic bases. The pH of humic acid conditioners is also alkaline in the range of 8-11, so adding biochar and humic acid can increase the soil pH. The soil cation exchange capacity is an influencing factor of pH. Biochar and humic acid can combine with various cations in the soil to increase the soil cation exchange capacity, thereby improving the acid-base buffering properties of the soil. Both biochar and humic acid are alkaline, and the amount used affects the size of the soil pH. Studies have found that the effect of adding high amounts of humic acid on improving soil pH over time is lower than that of adding low and medium amounts of humic acid. This may be related to the fact that humic acid will gradually be decomposed by microorganisms in the soil, reducing its effect. In addition, the amount of iron powder applied with low and medium amounts of humic acid is higher, which will further increase the soil pH.

[0056] In the potted experiment, humic acid can significantly increase the content of soil organic carbon and alkaline nitrogen; biochar significantly increased the amount of organic carbon. When the two were applied together with iron powder and Bacillus subtilis, the organic carbon and alkaline nitrogen were significantly increased, and the available phosphorus and available potassium were significantly reduced. This is similar to the results of the plot experiment: the combination of iron powder + biochar + Bacillus subtilis significantly increased organic carbon and reduced available phosphorus and available potassium; in the combination of iron powder + humic acid + Bacillus subtilis, the combination of high iron powder and low humic acid significantly increased organic carbon and alkaline nitrogen and reduced available phosphorus and available potassium. Humic acid contains rich organic matter and active functional groups, which can react with nitrogen in the soil, promote the mineralization and transformation of nitrogen, and improve the organic carbon and nitrogen utilization of the soil. The fact that iron powder reduces the content of available phosphorus and available potassium in the soil may be related to the oxidation products of iron powder (such as Fe 3+ ) and phosphate ions in the soil (PO4 3- ) to form an insoluble iron phosphate precipitate, which absorbs K in the soil + related.

[0057] The addition of dredged sediment increased the amount of reducible Cu in the soil and reduced the amount of weakly acid extractable and reducible Ni in the soil. The heavy metal stability assessment further verified this result. The correlation analysis results showed that the weakly acid extractable and reducible Cu content in the soil was significantly negatively correlated with soil pH, alkaline nitrogen and organic carbon, and significantly positively correlated with the reducible Fe content. The addition of sediment significantly increased the Fe content in the mixed soil. During the oxidation process of Fe in the soil, it reacts with metal cations, and Cu is mainly adsorbed on the surface of Fe oxide in the form of Cu (II) and a small amount of Cu (I). The adsorption of Ni on the surface of iron oxide is less affected by pH and competing ions. After the addition of sediment, the newly formed Fe 2+ It is possible that Ni can be fixed by coprecipitation or adsorption, reducing the proportion of its active form.

[0058] In the pot experiment, humic acid can reduce the activity of Cu and Ni in the soil. The heavy metal stability index of the treatment containing humic acid is higher. When iron powder and Bacillus subtilis are mixed with humic acid and biochar respectively, the stability of Ni is higher. Humic acid has a variety of active functional groups that can bind to heavy metal ions. Iron powder has reducing properties and can reduce the Ni originally adsorbed in the soil. 2+ Reduced to a more stable form, reducing the activity of Ni. The process of valence change of iron powder in the soil will continue to adsorb metal cations in the soil. Bacillus subtilis can secrete extracellular polymers. These polymers have the ability to bind to heavy metals and can bind to Ni through various mechanisms such as adsorption, complexation, precipitation, redox, electrostatic interaction and ion exchange, thereby reducing the biological effectiveness of Ni. When humic acid or biochar and iron powder are applied with bacterial agents, biochar and humic acid increase the organic matter content in the soil, provide more adsorption sites for heavy metals, and increase the reduction effect of iron powder. Organic matter can also promote the formation of soil aggregates, wrap heavy metals inside the aggregates, and reduce their mobility; it can also increase soil permeability, facilitate the activity of microorganisms, and promote the transformation of heavy metals by microorganisms.

[0059] Field trials in which the conditioning agents iron powder and Bacillus subtilis were mixed with humic acid and biochar in varying amounts revealed that the resulting conditioning agents had varying effects on Cu, Ni, and Cr in the soil. Among the conditioning agents mixed with biochar, high biochar and low iron powder levels showed the best stability for Cu and Ni, significantly increasing the residual state of Cu and Ni in the soil and shifting the residual state of Cr to an oxidizable state. Conditioning agents mixed with humic acid exhibited opposite effects on the heavy metals Cu, Ni, and Cr. High iron powder and low humic acid levels stabilized Cu more effectively, but less effectively Ni and Cr. Medium iron powder and humic acid levels stabilized Ni and Cr more effectively, but less effectively Cu.

[0060] The addition of dredged sediment promotes plant growth, significantly increasing plant height, plant width, biomass, and SPAD values. It also increases nitrogen, phosphorus, and potassium content in plants. The addition of sediment increases soil porosity and loosens the soil, which is beneficial for plant root growth and development. In pot experiments, plant biomass significantly increased in both biochar and Bacillus subtilis treatments, demonstrating that biochar and Bacillus subtilis promote plant growth. The addition of conditioning agents significantly impacts nitrogen, phosphorus, and potassium content in plants. In pot experiments, humic acid significantly increased plant phosphorus content, while iron powder significantly decreased it. The addition of iron powder significantly decreased available phosphorus in the soil. This nutrient deficiency inhibited plant growth and affected phosphorus uptake. Field trials showed that a combination of low iron powder and high biochar application (T1B3) promoted nitrogen and phosphorus accumulation in plants but inhibited potassium production. High-content biochar may adsorb ammonium nitrogen and available phosphorus in the soil through its porous structure, reduce nutrient leaching, and release them slowly for plant absorption, while the adsorption sites of medium-content biochar may be occupied by other ions (such as Ca 2+ Mg 2+ and K + ) is occupied, resulting in insufficient adsorption capacity for nitrogen and phosphorus and inability to effectively release them slowly, reducing the content of potassium available to plants in the soil and reducing the absorption of potassium by plants.

[0061] The addition of sediment and conditioning agents significantly affected the concentrations of Cu, Ni, Cr, and Fe in plants. Pot experiments showed that the addition of humic acid alone significantly increased the concentrations of Cu, Ni, Cr, and Fe in plants, while the application of Bacillus subtilis or biochar alone inhibited the accumulation of Cu, Ni, and Cr in plants. Low concentrations of humic acid promoted the uptake of Cu and Ni by plants. Bacillus subtilis can adsorb and immobilize heavy metals in the soil, reducing their concentration in the soil solution and thus reducing their uptake by plants. Biochar, with its porous structure and large specific surface area, can adsorb heavy metals in the soil, reducing their mobility and bioavailability in the soil, thereby inhibiting their uptake by plants. Plot experiments revealed that different combinations of iron powder and humic acid had different effects on Ni, Cr, and Fe in plants. Plants treated with medium amounts of iron powder and humic acid (T2F2) had the lowest Ni, Cr, and Fe concentrations.

[0062] The soil conditioner of the present invention has the following advantages: (1) the addition of sediment significantly reduces the soil pH, alkaline nitrogen, organic carbon and available potassium content, and significantly increases the available phosphorus content in the soil. After the addition of the conditioner, the pH, alkaline nitrogen and organic carbon of the mixed sediment soil can be increased, and the content of available potassium and available phosphorus can be reduced. The pot experiment showed that humic acid and biochar have a significant effect on improving pH, organic carbon and alkaline nitrogen, while reducing the content of available phosphorus and available potassium. The addition of high iron powder, low biochar and Bacillus subtilis (T3F1) and the addition of low iron powder, high biochar and Bacillus subtilis (T1B3) significantly increased the soil pH, alkaline nitrogen and organic carbon of the mixed sediment, and significantly reduced the content of available phosphorus in the soil. T1B3 significantly reduced the content of available potassium in the soil. (2) After the addition of sediment and conditioner, the soil fertility level can reach a fertile level. The soil comprehensive fertility levels of the treatments with only sediment addition (D), low iron powder and high humic acid addition (T1F3), and medium iron powder and medium biochar addition (T2B2) were the same as those of the control treatment. The order of soil comprehensive fertility index was CK (1.86) > D (1.69) > T1F3 (1.62) > T2B2 (1.60). (3) After adding sediment and conditioners, the heavy metals Cu, Ni, and Cr in the soil mainly existed in the residual state, and the weak acid extractable state accounted for a very low proportion. The pot experiment showed that the residual Cr accounted for more than 90%, and the residual Cu and Ni accounted for more than 70%. The results of the heavy metal stability assessment showed that the application of humic acid and iron powder alone could improve the stability of Ni in the soil, and the application of humic acid alone was beneficial to the stability of Cu. The combination of low iron powder and high biochar (T1B3) increased the stability of Cu and Ni in the soil. The combined application of iron powder and humic acid (T3F1) increased the stability of Cu in the mixed sediment soil from 0.7740 to 0.8046. (4) The addition of sediment and conditioners can significantly promote plant growth and reduce the accumulation of heavy metals Ni and Cr in plants. The content of heavy metals Ni and Cr in plants meets the standards of "Limits of Contaminants in Food" (GB2762-2017). The addition of sediment significantly increased plant height, plant width, biomass and SPAD value by 14.31%, 27.53%, 58.89% and 49.26%, respectively. The combined application of iron powder and biochar (TB) can significantly promote plant growth and reduce the content of heavy metals in plants. The plant width, biomass, SPAD, and N and P contents in plants in the T1B3 treatment were significantly higher than those in the control treatment. The T1B3 and T3B1 treatments significantly reduced the content of Ni and Cr in plants. The present invention utilizes dredged sediment and conditioners in a coordinated manner for agricultural land use. The effective content of heavy metals in the soil is extremely low and mainly exists in the form of residues. The risk of heavy metal pollution in the soil is low. The addition of sediment and conditioners helps the growth of cabbage, and the content of heavy metals Cr and Ni in the cabbage meets the "Limits of Contaminants in Food" standard (GB2762-2017).

[0063] In summary, the method of combining the soil conditioner with heavy metal soil for growing vegetables of the present invention is to mix compound fertilizer, soil conditioner and heavy metal soil and then use them to grow vegetables. The ingredients in the soil conditioner, such as biochar, iron powder, Bacillus subtilis and humic acid, can effectively fix heavy metals (such as nickel and chromium) in the soil, reduce their mobility and bioavailability, thereby reducing the absorption of heavy metals by vegetables, and thus effectively reducing the content of heavy metals in vegetables. At the same time, the addition of compound fertilizer and soil conditioner can also improve the physical structure of the soil, increase the aeration and water retention of the soil, promote the activity of soil microorganisms, enhance the fertility of the soil, increase the nutrient supply in the soil, provide a better soil environment for the growth of vegetables, and thus effectively promote the growth of vegetables. Therefore, the method of the present invention not only effectively reduces the content of heavy metals in vegetables, but also improves the soil environment and increases the nutrient supply, promotes the healthy growth of vegetables, has significant environmental and economic benefits, has important application value in solving the problem of planting in heavy metal contaminated soil, and has promotion and application value in the field of vegetable planting technology.

[0064] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A method for growing vegetables by combining a soil conditioner with heavy metal soil, characterized in that: The following steps are involved: Mixing compound fertilizer, soil conditioner and heavy metal soil and using them for growing vegetables can retain heavy metals in the soil, thereby reducing the content of heavy metals in vegetables and promoting vegetable growth; The soil improver consists of dredged sludge and a conditioner; The conditioning agent is selected from at least one of biochar, iron powder, Bacillus subtilis and humic acid; The heavy metals in the heavy metal soil include at least nickel and chromium.

2. The method according to claim 1, characterized in that The dredged sediment is the dredged sediment of a lake; The pH value of the dredged sludge is greater than 7, the organic carbon content is greater than 63g / kg, the alkaline nitrogen content is greater than 134mg / kg, the available phosphorus content is greater than 12mg / kg, the available potassium content is greater than 33mg / kg, the total copper content is less than 50mg / kg, the total nickel content is less than 78mg / kg, the total chromium content is less than 94mg / kg, and the total iron content is less than 26g / kg.

3. The method according to claim 1, characterized in that The conditioner consists of iron powder, bacillus subtilis and humic acid.

4. The method according to claim 3, characterized in that The soil conditioner consists of 1 part of dredged sediment, 0.0015-0.006 parts of iron powder, 0.0125-0.05 parts of humic acid and 0.0015-0.006 parts of Bacillus subtilis, calculated by mass.

5. The method according to claim 1, wherein The conditioning agent consists of biomass charcoal, iron powder and bacillus subtilis.

6. The method according to claim 5, characterized in that The soil conditioner consists of 1 part of dredged sediment, 0.0015-0.006 parts of iron powder, 0.0125-0.05 parts of biochar and 0.0015-0.006 parts of Bacillus subtilis, calculated by mass.

7. The method according to claim 1, characterized in that The biomass charcoal is selected from corn straw biochar; and / or, the number of viable bacteria per gram of the Bacillus subtilis is 100 billion; And / or, the humic acid is selected from mineral-derived potassium fulvic acid, and the humic acid content is ≥65%.

8. The method according to claim 1, characterized in that The pH value of the heavy metal soil is between 5 and 9, the organic carbon content is between 6 and 33 mg / kg, the alkaline nitrogen content is between 37 and 102 mg / kg, the available phosphorus content is between 5 and 49 mg / kg, the available potassium content is between 58 and 101 mg / kg, the total copper content is between 14 and 58 mg / kg, the total nickel content is between 18 and 87 mg / kg, the total chromium content is between 37 and 122 mg / kg, and the total iron content is between 16 and 39 g / kg.

9. The method according to claim 1, characterized in that The element content in the compound fertilizer is N15-P15-K15.

10. The method according to claim 1, characterized in that The vegetable is Chinese cabbage.

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