Application of Sulfur-Iron Modified Biochar in Maintaining Soil Nitrogen Content

Abstract

The present invention discloses the application of ferrous sulfide modified biochar in maintaining soil nitrogen content, and the application includes maintaining the nitrogen content in the soil and inhibiting the production of nitrate nitrogen in the soil. The ferrous sulfide modified biochar can inhibit the nitrification process of composite polluted soil and the growth and reproduction of AOA and AOB, especially the AOB-amoA gene inhibition effect is significant, which helps to inhibit the loss of nitrogen in the soil, improve the utilization efficiency of nitrogen fertilizer, and have a positive impact on soil health and crop growth. The ferrous sulfide modified biochar can improve composite polluted soil on the one hand, and has the potential to improve the effectiveness of nitrogen in polluted soil on the other hand.

Description

Technical Field

[0001] The invention belongs to the field of agriculture and environmental protection, and relates to the application of ferrous sulfide-modified biochar in maintaining soil nitrogen content. Background Art

[0002] Nitrogen is one of the mineral nutrients necessary for crop growth and development. In agricultural production, the abundance and supply of nitrogen in the soil is one of the important factors affecting crop growth and development, and it also has a significant effect on improving crop quality. The nitrogen cycle in the soil ecosystem mainly includes four processes driven by microorganisms, namely microbial nitrogen fixation, ammoniation, nitrification and denitrification. Among them, nitrification refers to the process in which ammonia in the soil is oxidized to form nitrates under the action of nitrifying microorganisms. Although nitrate nitrogen can improve the efficiency of nitrogen utilization by plants, nitrate nitrogen is difficult to be effectively adsorbed by soil colloids due to its chemical properties and is easily lost in the soil. When the nitrogen in the soil accumulates to a certain level and the crops fail to absorb and utilize it in time, the nitrogen leaches downward and gradually leaves the root zone of the plant and enters the groundwater system, causing nitrate pollution problems and leaching to produce NO2 - , N2O, etc. This process not only results in ineffective use of nitrogen, but also poses a potential threat to groundwater quality. Therefore, reducing nitrate leaching is of great significance for protecting water resources and promoting sustainable agricultural development. In addition, nitrification inhibitors are often used in agriculture to control the nitrification reaction rate, reduce nitrogen loss and avoid environmental pollution.

[0003] The traditional nitrification process includes two steps. The first step is the ammonia oxidation process catalyzed by ammonia oxidizing microorganisms encoding the amoA gene, among which ammonia oxidizing bacteria include ammonia oxidizing archaea (AOA) and bacteria (AOB). The second step is the nitrite oxidation process catalyzed by nitrite oxidizing bacteria (NOB). Therefore, inhibiting the activity of AOA and AOB can effectively inhibit nitrification in the soil.

[0004] When the soil is contaminated by heavy metal ions and antibiotics, the activity of AOA and AOB will increase significantly, thereby accelerating the conversion of ammonium nitrogen to nitrate nitrogen. At this time, a nitrification inhibitor is needed that can reduce the effectiveness of heavy metal ions in the soil while inhibiting the growth and reproduction of AOA and AOB.

[0005] Invention patent CN 107236545A discloses a sulfur-based-iron-based composite modified biochar. The modified biochar disclosed in the invention can reduce the effectiveness of cadmium ions in the soil, but does not disclose its application in maintaining nitrogen content in the soil, inhibiting the growth and reproduction of AOA and AOB in the soil, and inhibiting soil nitrification reactions. Summary of the invention

[0006] In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide an application of ferrous sulfide-modified biochar in maintaining soil nitrogen content. On the one hand, ferrous sulfide-modified biochar can inhibit the nitrification process of the soil; on the other hand, biochar has a rich pore structure that can "capture" nitrates. Retained in the pores of biochar, it affects nitrogen transformation in the soil.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] The first aspect of the present invention provides the use of ferrous sulfide-modified biochar in the following (1) and (2):

[0009] (1) Maintain nitrogen content in the soil;

[0010] (2) Inhibit the production of nitrate nitrogen in the soil.

[0011] Preferably, the sulfide-iron modified biochar inhibits the production of nitrate nitrogen in the soil by inhibiting the growth and reproduction of ammonia-oxidizing archaea and ammonia-oxidizing bacteria in the soil.

[0012] Preferably, the preparation method of the ferrous sulfide modified biochar is as follows:

[0013] (1) NaOH and CS2 are mixed in a volume ratio of (1-2):3, stirred, ultrasonicated, stirred in a water bath and filtered to obtain a sulfur-alkali modified solution;

[0014] (2) mixing the biochar after passing through a 100-mesh sieve with the sulfur-alkali modified solution, stirring, and drying to obtain sulfur-modified biochar;

[0015] (3) The sulfur-modified biochar and ferrous sulfite solution are mixed in a ratio of 1 g: (5-8) ml, stirred, filtered and dried to obtain sulfur-ferrous modified biochar.

[0016] Preferably, in step (1), the stirring time is 3-4 h, the ultrasonic time is 20-30 min, and the water bath stirring time is 12-16 h;

[0017] In step (2), the stirring time is 4-8 hours, the stirring temperature is 40-45°C, and the drying temperature is 40-45°C;

[0018] In step (3), the stirring time is 14-16 hours, the stirring temperature is 40-45°C, and the drying temperature is 40-45°C.

[0019] A second aspect of the present invention provides a nitrification inhibitor, wherein the nitrification inhibitor comprises the ferrous sulfide-modified biochar according to claim 1.

[0020] A third aspect of the present invention provides a method for inhibiting the production of nitrate nitrogen in soil, comprising applying the above-mentioned ferrous sulfide-modified biochar to the soil.

[0021] Preferably, the application amount of the ferrous sulfide modified biochar is 1-3% of the soil mass. Beneficial effects of the present invention:

[0022] The invention discloses the application of ferrous sulfide modified biochar in inhibiting the nitrification process of composite polluted soil and the growth and reproduction of AOA and AOB. The modified biochar has a significant inhibitory effect on the AOB-amoA gene, helps to inhibit the loss of nitrogen in the soil, improves the utilization efficiency of nitrogen fertilizer, and has a positive impact on soil health and crop growth. The ferrous sulfide modified biochar can improve composite polluted soil on the one hand, and has the potential to improve the effectiveness of nitrogen in polluted soil on the other hand. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 :Scanning electron microscope image of biochar;

[0024] Figure 2 : Fourier transform infrared spectrum of biochar;

[0025] Figure 3 : Soil in different treatment groups -N content;

[0026] Figure 4 : Abundance of AOA-amoA genes (a) and AOB-amoA genes (b) in soils with different treatments. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0028] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0029] Example 1: Preparation of ferrous sulfur-modified biochar.

[0030] (1) The wheat straw biochar was sieved through a 100-mesh plastic sieve and set aside.

[0031] (2) 400 ml of 0.40 mol / l NaOH and 600 ml of CS2 were stirred at room temperature using a magnetic stirrer (DF-101Z) in a volume ratio of 2:3 for 4 h, ultrasonicated for 30 min, and then stirred in a water bath at 40°C for 16 h using a magnetic stirrer. The mixture was naturally cooled to room temperature and filtered with a 0.45 μm organic phase filter to obtain a sulfur-alkali modified mixed solution.

[0032] (3) The sieved wheat straw biochar and the sulfur-alkali modified mixed solution were mixed in a ratio of 0.1 g:1 ml to prepare a biochar suspension, which was stirred at 45 °C for 8 h using a magnetic stirrer. After filtering the suspension, it was dried at 40 °C to obtain sulfur-modified biochar.

[0033] (4) 1 g of sulfur-modified biochar was mixed with 5 ml of 1.50 mol / L ferrous sulfate solution and stirred at 40 °C for 16 h using a magnetic stirrer. The mixture was naturally cooled to room temperature and filtered using a 0.45 μm organic phase filter membrane. The filtered biochar was stored at 40 °C and dried to obtain sulfur-iron-modified biochar.

[0034] The surface morphology and pore structure of wheat straw biochar (BC) and ferrous sulfur modified biochar (SFeB) were characterized by electron scanning microscopy-energy dispersive spectrometer (SEM-EDS). Figure 1 ). It can be observed that the surface of BC has a clear pore structure, while the surface of SFeB is relatively rough, with obvious granular block structures attached, and the biochar is fragmented to form a larger specific surface area. According to energy spectrum analysis (EDS), the mass fractions of N and O elements contained in SFeB are lower than those of BC to varying degrees, and the S and Fe elements are increased to varying degrees. The contents of the two elements are 7.55% and 13.38%, respectively, which are 7.17% and 13.13% higher than those of BC, respectively, confirming the successful attachment of sulfur and iron to the surface of wheat straw biochar.

[0035] According to Fourier transform infrared spectroscopy (FTIR) analysis ( Figure 2 ), the modified biochar was compared with CB at 605.94, 1086.10, 1621.40, and 3378.01 cm -1 The peak intensity at 605.94cm -1 The absorption vibration peak of C=S is 1086.10cm -1 Nearby is the absorption vibration peak of CS, 1621.40cm -1 Nearby is the absorption vibration peak of CO, which is observed at 3378.01 cm-1 by SFeB treatment. -1 The peak at 2918.07 cm-1 is greatly enhanced, mainly due to the formation of Fe-OH complex on the BC surface. -1) intensity decreased, indicating that the sulfur-iron modified biochar contained less -CH2 than the wheat straw biochar.

[0036] Example 2: Study on the nitrogen fixation effect of modified biochar on soil contaminated by cadmium and oxytetracycline hydrochloride.

[0037] (1) Test method

[0038] Soil pre-culture: Collect fresh soil and pass it through a 2mm sieve to determine the water content in the soil. Adjust the soil moisture content of the soil sample to 40% of the field moisture content and mix it evenly. Store it in a PVC pot and pre-culture it in a 25°C incubator under dark conditions for 10 days to restore the activity of soil microorganisms.

[0039] Formal culture: After the pre-culture, weigh a soil sample equivalent to 100g of dry soil weight and add it to a 250ml serum bottle, and add cadmium chloride (CdCl2·2H2O) and oxytetracycline hydrochloride (C 22 H 24 N2O9·HCl) as the pollution source and cadmium as the pollution substrate, with a concentration of 5 mg kg -1 , oxytetracycline hydrochloride concentration is 30 mg kg -1 , combined pollution, recorded as O30, added sulfur-iron modified biochar (SFeB), the addition amount was 1% of the dry weight of the soil sample, the specific treatment is shown in Table 1.

[0040] Table 1. Composite pollution concentration and biochar addition amount

[0041]

[0042] The pollutants were added separately and the soil moisture content was adjusted to 60% of the field water holding capacity using deionized water. After mixing evenly, the mixture was cultured at 25°C in the dark for 45 days. The soil moisture content was maintained by weighing during the culture period. content and AOB-amoA gene abundance.

[0043] The content is determined by:

[0044] Weigh 2.5 g of fresh soil sample and place it in a 50 ml centrifuge tube. Add 1 mol·L -1 After shaking for 30 min, 25 ml of KCl extract was filtered through a 0.45 μm filter into a 15 ml centrifuge tube and the content of content.

[0045] Fluorescence real-time quantitative PCR was used to quantitatively analyze ammonia oxidizing microorganisms. The measuring instrument was a fluorescence quantifier (BioER 9600plus). The primer sequences are shown in Table 2.

[0046] Table 2 Quantitative PCR and primers

[0047]

[0048]

[0049] (2) Test results

[0050] The soil of each treatment group Dynamic changes in content such as Figure 3 CK and O30 treated The content on the 45th day increased significantly compared with the 0th day, increasing by 81.48% and 65.21% respectively. There was no obvious trend fluctuation in the content from day 0 to day 45, indicating that SFeB significantly inhibited accumulation.

[0051] The abundance of AOA-amoA genes in contaminated and remediated soils Figure 4 a. The AOA-amoA gene copy numbers in CK, O30, and SFeO30B treatments were 1.17×10 9 , 1.19×10 9 , 1.02×10 9 copies g -1 Compared with the CK treatment, the SFeO30B treatment significantly inhibited the activity of AOA, and the activity of AOA decreased by 12.75%.

[0052] The abundance of AOB-amoA genes in contaminated and remediated soils Figure 4 b. The AOB-amoA gene copy numbers in CK, O30, and SFeO30B treatments were 3.34×10 7 , 3.53×10 7 , 2.43×10 7 copies g -1 Compared with the CK treatment, the SFeO30B treatment significantly inhibited the activity of AOB, decreasing it by 27.22%.

[0053] After SFeB treatment, the abundance of ammonia-oxidizing bacteria in the composite-contaminated soil decreased. The addition of biochar changed the abundance of AOA and AOB-amoA in the composite-contaminated soil.

[0054] The above experiments all indicate that the ferrous sulfide-modified biochar provided by the present invention can inhibit the accumulation of nitrate nitrogen, inhibit the growth and reproduction of AOA and AOB, and maintain the nitrogen content in the soil.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the implementation and application of the present invention. Any modifications, equivalent substitutions, etc. made in the implementation and application within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Application of ferrous sulfur modified biochar in the preparation of a product for simultaneously inhibiting the growth and reproduction of AOA and AOB in composite contaminated soil; characterized in that: The ferrous sulfide modified biochar is prepared by the following method: (1) The wheat straw biochar was sieved through a 100-mesh plastic sieve and set aside; (2) 400 ml of 0.40 mol / l NaOH and 600 ml of CS2 were stirred at room temperature for 4 h, ultrasonicated for 30 min, and then stirred for 16 h in a water bath at 40° C., cooled naturally to room temperature, and the solution was filtered with a 0.45 μm organic phase filter to obtain a sulfur-alkali modified mixed solution; (3) The sieved wheat straw biochar and the sulfur-alkali modified mixed solution were mixed in a ratio of 0.1 g:1 ml to prepare a biochar suspension, and the mixture was stirred at 45 °C for 8 h using a magnetic stirrer. After filtering the suspension, the suspension was dried at 40 °C to obtain sulfur-modified biochar; (4) 1 g of sulfur-modified biochar was mixed with 5 ml of 1.50 mol / L ferrous sulfate solution and stirred at 40 °C for 16 h using a magnetic stirrer, cooled naturally to room temperature, filtered using a 0.45 μm organic phase filter membrane, and the filtered biochar was stored at 40 °C and dried to obtain sulfur-iron modified biochar; The composite contaminated soil is soil compositely contaminated by cadmium chloride and oxytetracycline hydrochloride.

2. The use according to claim 1, characterized in that: In the ferrosulfide modified biochar, the S element content is 7.55%, and the Fe element content is 13.38%.

3. The use according to claim 1, characterized in that: In the composite contaminated soil, the concentration of cadmium chloride is 5 mg / kg, and the concentration of oxytetracycline hydrochloride is 30 mg / kg.

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