Method for reducing migration of pesticide in soil and device for simulating migration of pesticide in soil

Abstract

The invention relates to a method for reducing migration of pesticide in soil and a device for simulating migration of pesticide in soil. According to the method for reducing migration of the pesticide in the soil, biochar is adopted as an adsorbent for controlling pesticide migration in the soil, the biochar is added to fix the pesticide in the soil when the pesticide is used, and the adding amount of the biochar is 0.5%-3% of the weight of the soil. According to the method for reducing migration of the pesticide in the soil, the biochar is adopted as an adsorbent for controlling pesticide migration in the soil, and the biochar is used for improvement in the soil, so that fixation of the pesticide in the soil can be effectively controlled, pesticide migration is prevented, and harm of the pesticide to the environment is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of pesticide migration, and in particular to a method for reducing pesticide migration in soil and a device for simulating pesticide migration in soil. Background Art

[0002] As an important means to ensure food security, a large number of different types of pesticides are continuously added to farmland soil every year. However, these pesticides are directly related to human food and life and health safety. Many pesticides not only kill non-target targets, but also cause immeasurable harm to insects, animals and plants. It is reported that a variety of pesticides have been detected in soil, groundwater, surface water and sediments. Surface runoff caused by irrigation and rainfall can cause pesticide migration, causing greater environmental harm.

[0003] At present, although a large number of scholars have studied pesticides, little is known about their behavior in the real rice field environment. The fate of pesticides after entering the soil depends on different environmental processes, including adsorption / desorption, transport and degradation. Accurately understanding the migration patterns of pesticides in the soil environment is crucial to guiding the use and prevention of pesticides. The sprayed pesticides are washed away by rainwater in the water and on the leaves, resulting in surface runoff and causing huge environmental damage. However, existing methods still cannot effectively control the fixation of pesticides in the soil.

[0004] Therefore, it is necessary to improve the existing technology. Summary of the invention

[0005] In the prior art, the adsorption mechanism and migration law between biochar and pesticides in real soil still need to be further studied. Therefore, the present invention provides a method for reducing the migration of pesticides in soil and a device for simulating the migration of pesticides in soil.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for reducing the migration of pesticides in soil, which uses biochar as an adsorbent for controlling the transfer of pesticides in soil, and adds the biochar when using pesticides to fix the pesticides in the soil, wherein the amount of the biochar added is 0.5% to 3% of the weight of the soil.

[0007] In one implementation, the biochar is plant-derived biochar produced by high-temperature pyrolysis, and the biochar includes any one or more of wood biochar, agricultural waste biochar, fruit shell biochar, herbaceous plant biochar and bark biochar.

[0008] In one implementation, the pesticide includes a thiamethoxam solution and / or a clothianidin solution.

[0009] In one implementation, the pesticide is used at a concentration of 50 mg / L to 200 mg / L.

[0010] In one implementation, the particle size of the biochar is 0.1 mm to 2 mm.

[0011] In a second aspect, the present invention further provides a device for simulating the migration of pesticides in soil, which is used to simulate any of the above methods for reducing the migration of pesticides in soil, and determine the amount of biochar added according to the soil, comprising: A sample pool, used to provide pesticide samples; A peristaltic pump connected to the sample pool and used to continuously provide the required pesticide samples and ultrapure water; A PMMA column is connected to the peristaltic pump, and quartz sand, a soil sample and quartz sand are sequentially installed in the column from top to bottom; the soil sample includes mixed biochar and soil; A collector, connected to the PMMA column, for collecting the effluent of the PMMA column; The quartz sand was soaked in 10% hydrochloric acid for 1 hour to remove surface impurities, then rinsed with ultrapure water to remove residual hydrochloric acid, and finally dried in an oven at 60 degrees.

[0012] In one implementation, the soil is collected from a rice field, air-dried in a cool condition, and then passed through a 20-mesh nylon sieve.

[0013] Beneficial effects: The method for reducing the migration of pesticides in soil provided by the present invention adopts biochar as an adsorbent for controlling the transfer of pesticides in soil. The use of biochar improvement in soil can effectively control the fixation of pesticides in soil, prevent the transfer of pesticides, and reduce the harm of pesticides to the environment. At the same time, the present invention also provides a simulation device for the migration of pesticides in soil, provides an effective simulated soil column, can simulate the migration process of pesticides in real soil under different scenarios, effectively evaluate the migration of pesticides in real soil, and determine the amount of biochar required for different soils, thereby reducing the migration of pesticides in soil and optimizing the use of biochar in soil remediation. It has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the pesticide migration simulation device in soil provided by the present invention; Figure 2 This is the adsorption kinetic curve of thiamethoxam fitted by the second-order kinetic model; Figure 3 This is the adsorption kinetic curve of clothianidin fitted by the second-order kinetic model; Figure 4 is the adsorption isotherm of thiamethoxam; Figure 5is the adsorption isotherm of clothianidin; Figure 6 It is the normalized result of the pesticide residue in the soil profile after the migration test; Among them, the symbols in the figure are as follows: 1. Sample pool; 2. Peristaltic pump; 3. Quartz sand; 4. Soil sample; 5. Quartz sand; 6. Collector.

[0015] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the description of the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" described below means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms is not necessarily for the same embodiment or example. Moreover, the technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0017] In the first aspect, the present invention provides a method for reducing the migration of pesticides in soil, which uses biochar as an adsorbent for controlling the transfer of pesticides in the soil, and adds the biochar to fix the pesticides in the soil when the pesticides are used, wherein the amount of the biochar added is 0.5% to 3% of the weight of the soil. By adding 0.5% to 3% of biochar to the soil, the adsorption capacity of the soil for pesticides can be significantly improved, thereby reducing the migration of pesticides. As an adsorbent, biochar can fix pesticides in the soil, reduce their loss and the risk of contamination to groundwater, and improve the utilization efficiency of pesticides.

[0018] Specifically, the biochar is a plant-derived biochar obtained by high-temperature pyrolysis, and the biochar includes any one or more of wood biochar, agricultural waste biochar, fruit shell biochar, herbaceous plant biochar and bark biochar. Among them, the wood biochar is obtained by high-temperature pyrolysis of wood or sawdust, such as pine charcoal, oak charcoal, bamboo charcoal, etc. The agricultural waste biochar is obtained by high-temperature pyrolysis of agricultural waste such as rice husks, wheat straw, corn stalks, cotton stalks, peanut shells, etc. The fruit shell biochar is obtained by high-temperature pyrolysis of fruit shells such as coconut shells, walnut shells, almond shells, etc. The herbaceous plant biochar is obtained by high-temperature pyrolysis of herbaceous plants such as elephant grass, bagasse, reeds, etc. The bark biochar is obtained by high-temperature pyrolysis of barks such as eucalyptus bark, oak bark, etc. The biochar also includes other plant-derived biochar, such as high-temperature pyrolysis of seaweed, ferns, etc.

[0019] By using plant-derived biochar, especially wood biochar, agricultural waste biochar, fruit shell biochar, herbaceous plant biochar and bark biochar, their porous structure and large specific surface area help improve the adsorption capacity of pesticides. This not only utilizes renewable resources and has environmental significance, but also the biochar prepared by high-temperature pyrolysis has stable chemical properties and can play a long-term adsorption role.

[0020] Therefore, fixing pesticides in the soil through biochar can reduce the risk of pesticides polluting the surrounding environment such as groundwater by reducing their migration and leaching in the soil; it can help delay the degradation of pesticides so that they can continue to play a role in preventing and controlling pests and diseases for a longer period of time and improve the efficiency of pesticide use; it can reduce the toxicity of pesticides to beneficial microorganisms in the soil, maintain the stability and diversity of soil microbial communities, and ensure the ecological health of the soil; it can improve the soil structure and fertility to a certain extent, which is conducive to the better growth and development of crops.

[0021] Furthermore, the pesticide includes thiamethoxam solution and / or clothianidin solution. The method provided by the present invention can specifically control the migration of specific pesticides in the soil, has stronger specificity and effect, and is particularly important for the management of these two common pesticides and environmental protection.

[0022] Specifically, the pesticide is used at a concentration of 50 mg / L to 200 mg / L. By limiting the pesticide concentration to 50 mg / L to 200 mg / L, it is ensured that the test and application are carried out within a reasonable pesticide concentration range. This can not only ensure the effectiveness of the pesticide, but also prevent environmental pollution problems caused by excessively high concentrations, further optimizing the use effect of the pesticide and environmental protection.

[0023] Furthermore, the particle size of the biochar is 0.1 mm to 2 mm. By limiting the particle size range of the biochar (0.1 mm to 2 mm), it can be ensured that the biochar has suitable adsorption performance and distribution characteristics in the soil. The smaller particle size increases the specific surface area of ​​the biochar, thereby improving the adsorption efficiency of the pesticide, and can optimize the balance between the adsorption effect of the biochar and the physical properties of the soil to a certain extent, improve the fixation efficiency of the pesticide, and reduce its migration.

[0024] Combined with reference Figure 1 , Figure 1 The present invention also provides a device for simulating the migration of pesticides in soil, comprising: Sample pool 1, used for providing pesticide samples; A peristaltic pump 2, connected to the sample pool, for continuously providing the required pesticide samples and ultrapure water; A PMMA column connected to the peristaltic pump, wherein quartz sand 3, soil sample 4 and quartz sand 5 are sequentially installed from top to bottom; A collector 6, connected to the PMMA column, for collecting the effluent of the PMMA column; Wherein, the quartz sand is soaked in 10% hydrochloric acid for 1 hour to remove surface impurities, washed with ultrapure water to remove residual hydrochloric acid, and finally dried in a 60-degree oven. The soil is collected from a paddy field, air-dried under cool conditions, and then passed through a 20-mesh nylon sieve. Wherein, the design of the PMMA column enables the experimental device to be layered with quartz sand and soil samples, which helps to simulate the migration of pesticides in an actual soil environment. The treated quartz sand can remove surface impurities to avoid interfering with the experimental results, while ensuring the purity and consistency of the quartz sand. The selection of paddy field soil can represent a certain type of agricultural soil environment, making the experimental results more valuable for practical applications. Air drying under cool conditions can avoid the effects of high temperature on organic matter and biological activity in the soil, and maintain the natural state of the soil. Passing through a 20-mesh nylon sieve can remove large particles and impurities, making the soil sample more uniform, thereby reducing the error caused by soil heterogeneity during the experiment. Most of the existing technologies focus on pollutant migration experiments in quartz sand media, lacking pollutant migration in real soil. The processing method of this application provides good soil samples for the experiment, ensuring the controllability of experimental conditions and the accuracy of results. In addition, the pesticide migration simulation device in soil can determine the dosage of the biochar according to different soils through simulation experiments, providing a more accurate method for reducing pesticide migration in soil.

[0025] The following verification experiment of the method for reducing the migration of pesticides in soil provided by the present invention comprises the following steps: Soil preparation: Soil from paddy fields was collected and air-dried in a cool environment. The soil used in the adsorption kinetics and adsorption isotherm tests was passed through a 100-mesh nylon sieve, and the soil used in the migration test was passed through a 20-mesh nylon sieve; Biochar preparation: The biochar was ground in an agate mortar and passed through a 300-mesh nylon sieve; Preparation of pesticides: Weigh powdered thiamethoxam and clothianidin and dissolve them in ultrapure water to prepare a stock solution with a concentration of 250 mg / L; Preparation of clean quartz sand: Soak the quartz sand in 10% hydrochloric acid for 1 hour to remove surface impurities, rinse with ultrapure water to remove residual hydrochloric acid, and finally dry the quartz sand in an oven at 60 degrees; Preparation of soil mixed with biochar: Biochar was mixed with soil sieved through a 2 mm sieve, with the biochar ratio being 0.5%, 1%, and 3% of the soil weight; Use of Migration Devices: Figure 1 The pesticide migration simulation device in soil shown in the figure, wherein the column diameter and length of the PMMA column are 1.5 cm and 20 cm respectively, a peristaltic pump is used to continuously provide the required pesticide sample and ultrapure water, and an external automatic partial collector is used to collect the effluent.

[0026] Filling and stabilization of the packed column: Slowly drip deionized water from the tube wall until the column is full, close the valve for 24 hours to stabilize the soil particles, and then continue to slowly add deionized water until no soil particles can be monitored to flow out, indicating that the balance is complete; Extraction of pesticides in soil: The obtained soil samples were freeze-dried, ground and passed through a 100-mesh nylon sieve. 1 g of soil was weighed and soaked in 1 ml of water for 10 min. Thiamethoxam and clothianidin were shaken with 10 ml of acetonitrile for 30 min, ultrasonicated for 10 min, and centrifuged (8000 rpm, 5 min) to obtain the supernatant. This was repeated 3 times. The supernatants were combined and filtered through a 0.45 um organic nylon membrane filter and analyzed using HPLC.

[0027] Analysis of pesticides: Pesticides in soil and water were analyzed using high performance liquid chromatography (HPLC). HPLC (LC-1260, Agilent) was equipped with an Agilent C18 column (150×4.6 mm inner diameter, 5 μm particle size, Phenomenex) for analysis. 50% methanol and 50% formic acid water (0.2% formic acid) were used as mobile phases, passing through the column at a flow rate of 0.8 mL / min. The UV monitoring wavelengths for thiamethoxam and clothianidin were both 254 nm. The retention times of thiamethoxam and clothianidin were 2.61 min and 3.92 min, respectively.

[0028] This experiment mainly evaluated the adsorption and fixation performance of biochar mixed soil through adsorption kinetics test, adsorption isotherm test and migration experiment.

[0029] Adsorption kinetics test: The adsorption kinetics experiment was to add pesticides to the mixture of biochar and soil. The mixture of biochar and soil was dissolved in ultrapure water and sonicated at 25kHz for 10 minutes before use. The proportion of biochar was 0.5%, 1%, and 3% of the soil weight, and the final concentration of pesticide was 50mg / L. After mixing, the mixture was continuously shaken for 8 hours at 200rmp and 25℃ in the dark in a constant temperature incubator. 0.5ml of supernatant was collected at 2, 5, 10, 15, 20, 30, 40, 60, 120, 240, 360, and 480min, respectively, and filtered using a 0.45um PES needle filter. The content of pesticides was determined using high performance liquid chromatography (HPLC). The adsorption kinetics results were fitted using pseudo-first-order kinetic model and pseudo-second-order kinetic model.

[0030] Pseudo-first-order kinetic model: ; Pseudo-second-order kinetic model: ; Among them, t (min) is the contact time, q t and q e (mg / g) are the pesticide adsorption amounts at time t and equilibrium, respectively. k1 (min-1) and k2 (g / mg / min) are the adsorption rate constants of the pseudo-first-order and pseudo-second-order models, respectively.

[0031] In the chart, S stands for soil and BC stands for biochar.

[0032] Table 1. Adsorption kinetic model fitting parameters Combined with reference Figure 2 and Figure 3 , Figure 2 3 is the adsorption kinetic curve of thiamethoxam fitted by the second-order kinetic model, and 4 is the adsorption kinetic curve of clothianidin fitted by the second-order kinetic model. Figure 2 and Figure 3 The adsorption of pesticides in biochar treated soils was shown t As time goes by, it can be seen that the adsorption of all treatments tends to be dynamically stable after 120 min, while q t The size of changes over time is S+3%BC>S+1%BC>S+0.5%BC, indicating that the original soil has a weak adsorption capacity for pesticides. Adding biochar can significantly increase the soil's adsorption capacity for thiamethoxam and clothianidin. The pseudo-first-order and pseudo-second-order kinetic models (Table 1) were used to fit the experimental data, and it was found that the adsorption process of thiamethoxam and clothianidin in the soil with added biochar was more consistent with the pseudo-second-order kinetic model (R 2>0.998), which indicates that the adsorption process of thiamethoxam and clothianidin by biochar mainly relies on chemical adsorption, and the stronger adsorption capacity of pesticides is attributed to more adsorption sites. The higher the content of biochar, the faster the surface adsorption rate and the stronger the adsorption capacity.

[0033] Adsorption isotherm test: Pesticides were added to the biochar and soil mixture. The biochar ratio was 0.5%, 1%, and 3% of the weight of the soil (1 g), and the final concentration of the pesticide was 0, 10, 20, 30, 40, and 60 mg / L in a 10 mM NaNO3 electrolyte solution. The samples were shaken at 200 rpm for 24 h in a 25 ° C dark incubator. After centrifugation, the collected supernatant was filtered using a 0.45 um PES needle filter, and the pesticide content was determined using high performance liquid chromatography (HPLC). The adsorption isotherm data were fitted with the Langmuir model.

[0034] Among them, the Langmuir model: ; In the above formula, q e (mg / g) is the coverage of pesticide on the soil surface, q m (mg / g) is the maximum coverage of pesticide on the soil surface, K L (L / mg) is a constant related to the free energy of adsorption.

[0035] Freundlich Model: K F (mg g -1 )(mg L -1 )1 / n) is the Freundlich constant related to the adsorption capacity of the adsorbent, and n is the Freundlich coefficient.

[0036] Table 2. Adsorption isotherm model fitting parameters Combined with reference Figure 4 , Figure 5 and Table 2, where Figure 4 is the adsorption isotherm of thiamethoxam, Figure 5 is the adsorption isotherm of clothianidin. Among them, both the Langmuir and Freundlich models can fit the adsorption isotherm curves of thiamethoxam and clothianidin well (R 2 =0.85~0.99), while the Freundlich model can better fit the results of soil adsorption of mixed biochar.

[0037] from Figure 4 , Figure 5The results in Table 2 and Table 2, as well as the shape of the adsorption isotherms and the fitting analysis with the Langmuir, Freundlich and other models, show that the adsorption of pesticides on the biochar surface mainly occurs through multilayer adsorption. Among them, the soil has a weak adsorption of thiamethoxam and clothianidin, with the maximum adsorption amounts of 0.047 and 0.249 mg / g, respectively; the soil with biochar added has a strong adsorption effect on thiamethoxam and clothianidin, and the soil containing a higher proportion of biochar has a stronger adsorption amount and adsorption stability for thiamethoxam. This is due to the strong adsorption of biochar on thiamethoxam and clothianidin, with the maximum adsorption amounts of 27 and 24 mg / g, respectively. The lower unit adsorption amount and stable adsorption amount of low biochar addition are attributed to other substances in the soil (such as metal ions, organic matter, etc.) occupying the effective sites of biochar.

[0038] Migration assay: The migration test was carried out in a 1.5*20cm PMMA column, and the pesticides were migrated by gravity. The bottom of the column was filled with 1cm 30-50 mesh clean quartz sand, and then 20g of soil samples mixed with biochar were filled into the column respectively. Deionized water was added to fill the column for 24 hours to stabilize the soil particles. Then deionized water was added continuously until the outflow of soil particles could not be monitored before further experiments. In order to investigate the migration of exogenously added pesticides, 50ml of 50mg / l pesticide sample solution was continuously added to the column until the solution completely flowed out, and then deionized water was continuously added to elute the pesticides. Potassium bromide was used as a tracer, and every 5ml of the outflowing liquid was used as a sample. After the transfer experiment, the soil in the column was divided into 5 parts, and acetonitrile was used to extract the residual pesticides in the soil. After obtaining the concentration, the retention curve was drawn to analyze the retention law of the pesticide in the soil profile.

[0039] Figure 6 It is the normalized result of the residual pesticide in the soil profile after the migration test. Figure 6 From the results, it can be seen that in the soil without biochar, the pesticides almost all migrated out of the soil column, while no pesticides were detected in the soil. The retention rate of the two pesticides in the soil mixed with biochar was about 100%. Compared with 0.5% biochar, 1% biochar had a better interception effect. 0.5% biochar was mainly retained in 0-4cm (greater than 93%), and 1% was mainly retained in 0-2cm (greater than 97%). The upper layer where pesticides are retained in the soil is usually beneficial to degradation, because it is the most active part of soil microorganisms and contains rich organic matter, nutrients, plant roots, etc., which is also conducive to in situ remediation of soil pollutants.

[0040] The above test shows that biochar-amended soil greatly improves the soil's adsorption speed and capacity for pesticides. The higher the biochar content, the more obvious the adsorption capacity improvement. Among them, in the migration test, 0.5% and 1% biochar-amended soil can fix all the pesticides that enter the soil in the soil column, and most of them are fixed in the top layer. The higher the biochar content, the higher the top layer fixation ratio. Therefore, using biochar to improve the soil can effectively control the fixation of pesticides in the soil, prevent pesticide transfer, and reduce the harm of pesticides to the environment.

[0041] In summary, the method for reducing the migration of pesticides in soil provided by the present invention adopts biochar as an adsorbent for controlling the transfer of pesticides in soil. The use of biochar improvement in soil can effectively control the fixation of pesticides in soil, prevent the transfer of pesticides, and reduce the harm of pesticides to the environment. At the same time, the present invention also provides a simulation device for the migration of pesticides in soil, provides an effective simulated soil column, can simulate the migration process of pesticides in real soil under different scenarios, and effectively evaluate the migration of pesticides in real soil, thereby reducing the migration of pesticides in soil and optimizing the use of biochar in soil remediation. It has a wide range of applications.

[0042] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for reducing the migration of pesticides in soil, characterized in that: Biochar is used as an adsorbent for controlling pesticide transfer in the soil. When the pesticide is used, the biochar is added to fix the pesticide in the soil, wherein the addition amount of the biochar is 0.5% to 3% of the soil weight.

2. The method for reducing the migration of pesticides in soil according to claim 1, characterized in that: The biochar is plant-derived biochar produced by high-temperature pyrolysis, and the biochar includes any one or more of wood biochar, agricultural waste biochar, fruit shell biochar, herbaceous plant biochar and bark biochar.

3. The method for reducing the migration of pesticides in soil according to claim 1, characterized in that: The pesticide includes thiamethoxam solution and / or clothianidin solution.

4. The method for reducing the migration of pesticides in soil according to claim 1, characterized in that: The pesticide is used at a concentration of 50 mg / L to 200 mg / L.

5. The method for reducing the migration of pesticides in soil according to claim 2, characterized in that: The particle size of the biochar is 0.1 mm to 2 mm.

6. A device for simulating the migration of pesticides in soil, characterized in that: The method for simulating the method for reducing the migration of pesticides in soil according to any one of claims 1 to 5, and determining the dosage of the biochar according to the soil, comprising: A sample pool, used to provide pesticide samples; A peristaltic pump connected to the sample pool and used for continuously providing the required pesticide samples and ultrapure water; A PMMA column is connected to the peristaltic pump, and quartz sand, a soil sample and quartz sand are sequentially installed in the column from top to bottom; the soil sample includes mixed biochar and soil; A collector, connected to the PMMA column, for collecting the effluent of the PMMA column; The quartz sand was soaked in 10% hydrochloric acid for 1 hour to remove surface impurities, then rinsed with ultrapure water to remove residual hydrochloric acid, and finally dried in an oven at 60 degrees.

7. The device for simulating pesticide migration in soil according to claim 1, characterized in that: The soil samples were collected from rice fields, air-dried in a cool environment, and then passed through a 20-mesh nylon sieve.

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