Method for determining salinity in coastal salinized soil by adopting ultrasonic extraction method

Abstract

The invention discloses a method for determining salinity in coastal saline soil by adopting an ultrasonic extraction method. The method comprises the following steps: (1) determining optimal extraction parameters through experiments; (2) weighing the air-dried coastal salinized soil which is quantitatively sieved, putting the air-dried coastal salinized soil into a conical flask, and adding distilled water into the conical flask according to a water-soil mass ratio; (3) sealing the conical flask, and performing ultrasonic extraction treatment; (4) sucking 40 ml of the turbid liquid from the conical flask into a centrifugal tube, setting centrifugal parameters, and carrying out centrifugal treatment to prepare a clarified leaching solution; (5) accurately measuring an upper-layer clarified leaching solution from the centrifugal tube, evaporating the upper-layer clarified leaching solution to dryness in a ceramic evaporation dish, and continuously drying in a drying oven until the weight is constant; and (6) calculating the salt content in the coastal saline soil according to the mass of the dried residual solid. The method provided by the invention solves the problems of insufficient extraction and low separation efficiency of salt in the coastal salinized soil in a traditional method, and can rapidly and accurately measure the salt content in the coastal salinized soil.

Description

TECHNICAL FIELD

[0001] The application relates to a method for measuring the salt content of coastal saline soil by ultrasonic extraction, and belongs to the technical field of soil detection. BACKGROUND

[0002] Soil salinization has become an important factor endangering the health of land, and the detection of the degree of soil salinization is increasingly valued. At present, the soil salt content determination methods for forests and farmland are mostly based on the water-soluble salt content of soil. Compared with the conventional soil structure of forests and farmlands, the coastal saline soil has heavy texture, tight soil structure, and smaller soil particle size, and the particles have strong adhesion. The salt is more adsorbed or fixed on the surface of clay particles or in the soil structure. According to the soil characteristics (heavy texture, tight structure, and strong salt adsorption) of saline soil, the conventional water-soluble salt content determination method cannot meet the requirements of soil salt content determination of coastal saline soil, and it is difficult to fully extract the salt attached to the surface or structure of saline soil, and the slow quantitative filter paper cannot guarantee the preparation of sufficient clear extraction solution, resulting in inaccurate determination results. Therefore, in view of the soil characteristics of coastal saline soil, a new soil salt content determination method is needed to solve the problems of difficult salt extraction and inaccurate determination results in coastal saline soil. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the application provides a method for measuring the salt content of coastal saline soil by ultrasonic extraction, which uses ultrasonic extraction and centrifugal method to prepare the determination technology of the extraction solution, solves the problems of insufficient extraction of salt in coastal saline soil and low separation efficiency of traditional methods. By adopting a double-frequency alternating ultrasonic treatment mode, the extraction efficiency of salt in different particle size soils is significantly improved. The water-soil mass ratio is accurately set, and the method is widely applicable to the determination of salt content in light and heavy saline soil. The centrifugal method is used instead of the traditional suction filtration and filter paper filtration, which can quickly separate the fine particles suspended in the solution, and quickly and accurately determine the total salt content of the extraction solution.

[0004] To achieve the above purpose, the application provides the following technical scheme: a method for measuring the salt content of coastal saline soil by ultrasonic extraction, comprising the following steps:

[0005] (1) determining the optimal extraction parameters of ultrasonic extraction of coastal saline soil through experiments, the extraction parameters including ultrasonic frequency and extraction time;

[0006] (2) weighing 10g of air-dried coastal saline soil passing through a 1mm sieve and placing it in a conical flask, and adding distilled water into the conical flask according to the water-soil mass ratio;

[0007] (3) sealing the conical flask and placing it in an ultrasonic cleaner for ultrasonic extraction treatment;

[0008] (4) After the ultrasonic extraction is completed, 40ml of the suspension liquid is sucked from the conical flask into a centrifugal tube, and centrifugal parameters are set to perform centrifugal treatment to prepare a clear extraction liquid;

[0009] (5) After the centrifugal treatment is completed, the clear extraction liquid is accurately taken from the centrifugal tube into a porcelain evaporating dish, and a water bath method is used to evaporate the liquid to dryness, and then the liquid is placed into an oven to continue drying until a constant weight is obtained.

[0010] (6) The salt content in the coastal saline soil is calculated according to the residual solid mass after drying.

[0011] Preferably, in step (1), the ultrasonic extraction treatment is performed in two stages by using a double-frequency alternating ultrasonic treatment method.

[0012] Preferably, the double-frequency alternating ultrasonic treatment uses a 20KHz low-frequency ultrasonic wave to destroy larger soil particles in the first stage, and uses a 40KHz high-frequency ultrasonic wave to enhance the extraction capacity of salt in the adsorption state of small particles in the second stage.

[0013] Preferably, the double-frequency alternating ultrasonic treatment sets the ultrasonic frequency to 20KHz in the first stage, and sets the ultrasonic extraction time to 4min; and sets the ultrasonic frequency to 40KHz in the second stage, and sets the ultrasonic extraction time to 4min.

[0014] Preferably, in step (2), the water-soil mass ratio is 8:1, and the corresponding volume of distilled water added is 80ml.

[0015] Preferably, in step (4), the centrifugal parameters are set as follows: the centrifugal speed is 5000r / min, and the centrifugal time is 15min.

[0016] Preferably, in step (5), the clear extraction liquid is taken in an amount of 20ml.

[0017] Preferably, in step (5), the drying temperature of the oven is 90℃, and the drying time is 2h.

[0018] The present application has the following beneficial effects:

[0019] The double-frequency alternating ultrasonic treatment mode is adopted, first, the 20KHz low-frequency ultrasonic wave is used to destroy the larger soil particles, and then the 40KHz high-frequency ultrasonic wave is used to enhance the extraction capacity of salt in the adsorption state of small particles, and the double-frequency ultrasonic synergistic effect significantly improves the extraction efficiency of salt in different particle size soils, and is more suitable for the determination of salt in coastal saline soil. In the process of determining the salt content of coastal saline soil, if the water-soil mass ratio is too large, it is not conducive to the subsequent operation, and if it is too small, it may lead to insufficient extraction of salt, and the water-soil mass ratio of the present application is 8:1, which is widely applicable to the determination of salt content of mild and severe saline soil. Compared with the conventional suction filtration and filter paper filtration, the centrifugal method can quickly separate the small particles suspended in the solution, prepare clear leaching solution, avoid impurity interference, and accurately determine the total salt content of the leaching solution. The amount of leaching solution will affect the measurement result, too much will cause the salt to be difficult to weigh to a constant weight due to water absorption, and too little will cause the measurement result error to be too large, and the amount of leaching solution in the present application is 20ml, which can ensure the accuracy of the salt content determination result. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The turbidity change of the leaching solution under different centrifugal parameters of the present application;

[0021] Figure 2 The influence of the centrifugal parameter of the present application on the salt content of saline soil;

[0022] Figure 3 The influence of the water-soil mass ratio of the present application on the salt content of soil with different degrees of salinization;

[0023] Figure 4 The influence of different leaching solution suction amounts of the present application on the salt content of the test soil;

[0024] Figure 5 The influence of ultrasonic extraction of the present application on the salt content of moderate saline soil. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] The present application provides a method for determining the salt content of coastal saline soil by ultrasonic extraction, comprising:

[0027] Centrifugal parameter experiment design

[0028] The centrifugal parameters are divided into two factors of rotation speed and time. The centrifugal parameters are set as 3000 r / min, 4000 r / min, 5000 r / min and 6000 r / min, and the centrifugal time is set as 5 min, 10 min, 15 min and 20 min, which are 4 gradients in total. The above is 16 treatments, each with 6 repetitions. The selected experimental soil is moderate saline soil. After centrifugation, the turbidity of the leaching liquid is determined. Except that the centrifugal method is used instead of the traditional filtration or filtration method, the rest of the experimental steps are in accordance with the traditional weight method for determining the salt content of soil. The optimal centrifugal parameters and time are selected according to the experimental results.

[0029] As shown in Figure 1 With the increase of centrifugal speed and centrifugal time, the turbidity of the leaching liquid gradually decreases. When the centrifugal speed is 3000 r / min, the turbidity of the leaching liquid under different centrifugal time treatments is the highest, indicating that the leaching liquid contains more impurities at this time, which affects the accuracy of the salt measurement results. When the centrifugal time reaches 15 min or more, the turbidity of the leaching liquid under the centrifugal speed of 5000 and 6000 r / min is basically stable. And under the same treatment time, the turbidity of the leaching liquid of the two does not change significantly, indicating that the impurities in the leaching liquid are basically removed and reach a clear state.

[0030] As shown in Figure 2 With the increase of centrifugal time, the determination results of soil salt content under different centrifugal speed treatments show a trend of first decreasing and then increasing. When the centrifugal time reaches 15 min or more, the soil salt content under the centrifugal speed of 4000 r / min, 5000 r / min and 6000 r / min does not change significantly, and the determination value tends to be stable.

[0031] In summary, according to the change of leaching liquid turbidity and salt content, the optimal centrifugal parameters are centrifugal speed of 5000 r / min and centrifugal time of 15 min.

[0032] Water-soil mass ratio experimental design

[0033] The water-soil mass ratio is set as 5:1, 6:1, 8:1 and 10:1, and three different salinization degrees of experimental soil with salt content of 0-1 g / kg, 1-2 g / kg and 2-4 g / kg are selected. The above is 12 treatments, each with 6 repetitions. According to the experimental results of Example 1, the centrifugal method is used to set the centrifugal speed of 5000 r / min and the centrifugal time of 15 min to prepare the leaching liquid. The rest of the experimental steps are in accordance with the traditional weight method for determining the salt content. The optimal water-soil mass ratio is selected according to the experimental results.

[0034] As shown in Figure 3As shown in the table, the salt content determination results of different degrees of salinization soil showed a trend of first increasing and then decreasing with the increase of water-soil mass ratio. When the water-soil mass ratio increased from 6:1 to 8:1, the salt content determination results of non-saline soil and light salinization soil changed significantly; when the water-soil mass ratio increased from 8:1 to 10:1, the salt content determination values of the three test soils changed insignificantly.

[0035] In summary, for salinized soil, the optimal water-soil mass ratio is 8:1, and the soil salt content determination result is more accurate.

[0036] Extraction solution uptake experiment design

[0037] The extraction solution uptake was set to 10ml, 20ml, 30ml, 40ml, a total of 4 gradients, and three different salinization degrees of experimental soil with salt content of 0-1g / kg, 1-2g / kg, 2-4g / kg were selected, a total of 12 treatments, each treatment with 6 replicates. The optimal water-soil mass ratio in Example 2 and the optimal centrifugation parameters in Example 1 were used to prepare the extraction solution. The rest of the experimental steps for determining the salt content remained unchanged from the traditional gravimetric method. The optimal extraction solution uptake was selected according to the experimental results.

[0038] Please refer to Figure 4 As shown in the table, when the extraction solution uptake increased from 10ml to 20ml, the salt content determination results of the three experimental soils showed a significant decreasing trend. When the extraction solution uptake increased from 20ml to 40ml, the salt content determination values of the three experimental soils did not change significantly, and the determination results tended to be stable.

[0039] In summary, to ensure the accuracy of the experimental results, the optimal uptake of the extraction solution is 20ml.

[0040] Ultrasonic extraction experiment design

[0041] The ultrasonic frequency of the ultrasonic wave was set to 20KHz, 40KHz, and 20+40KHz mixed, a total of 3 gradients, and the time was set to 4min, 6min, 8min, 10min, a total of 4 gradients, a total of 12 treatments, each treatment with 6 replicates. The optimal water-soil mass ratio in Example 2, the optimal centrifugation parameters in Example 1, and the optimal extraction solution uptake in Example 3 were used to prepare the extraction solution, and the rest of the experimental steps for determining the salt content were consistent with the traditional gravimetric method. The optimal ultrasonic frequency and time were selected according to the experimental results.

[0042] Please refer to Figure 5As shown, the measured value of salt content of the experimental soil increases with the increase of ultrasonic frequency at the same ultrasonic extraction time. When the ultrasonic extraction time reaches 4 min and 6 min, the measured value of salt content under the condition of 20+40KHz double-frequency alternating treatment is significantly higher than that under the condition of 20KHz and 40KHz treatment, and the effect of salt extraction is better than that of the former two, and the measured value of salt content is not significantly different from that under the condition of 60KHz treatment, and the extraction effect is consistent. When the treatment time reaches 8 min or more, the measured value of salt content of each treatment basically remains unchanged, maintaining a stable state. The effect of 20+40KHz and 60KHz treatment is consistent, indicating that the extraction of salt is more sufficient. It can be seen that the effect of 20+40KHz double-frequency alternating treatment is better.

[0043] In summary, the optimal ultrasonic extraction parameters are: the first stage ultrasonic frequency is 20KHz, and the extraction time is 4min; the second stage ultrasonic frequency is 40KHz, and the extraction time is 4min.

[0044] The method is compared with the traditional gravimetric method. Three different salt content of coastal saline soil samples A, B and C are selected, dried by air, ground and passed through a 1mm sieve, and the true salt content is 2.55g / kg, 3.60g / kg and 4.20g / kg respectively. The salt content of A, B and C coastal saline soil samples is determined by using the traditional gravimetric method and the method of the application respectively, and the determination results of the two methods are compared.

[0045] The implementation steps are as follows:

[0046] (1) 10g of air-dried soil sample passing through a 1mm sieve is weighed and placed in a conical flask, and 80ml of distilled water is added to the conical flask according to the water-soil mass ratio of 8:1.

[0047] (2) After the conical flask is sealed, it is placed in an ultrasonic cleaner, and ultrasonic extraction treatment is carried out in a 20+40KHz double-frequency alternating mode. First, the ultrasonic frequency is set to 20KHz for 4min in the first stage, and then the ultrasonic frequency is adjusted to 40KHz for 4min in the second stage.

[0048] (3) After ultrasonic extraction, 40ml of the suspension liquid is sucked from the conical flask into a centrifugal tube, and centrifugal treatment is carried out at a centrifugal speed of 5000r / min for 15min to obtain a clear extraction liquid.

[0049] (4) After centrifugation, 20ml of the upper clear extraction liquid is sucked from the centrifugal tube into a porcelain evaporating dish, and evaporated to near dryness by water bath method, and then placed in a 90℃ oven for further drying for 2h.

[0050] (5) The salt content in the soil sample is calculated by the mass of the residual solid after drying.

[0051] Table 1 Comparison of determination results of different salt content saline soil under traditional mass method and the method of the application

[0052]

[0053] As shown in Table 1, the experimental results show that the determination results of the method of the application are closer to the true value, and the relative error is much lower than that of the traditional mass method. It shows that the method of the application is more sufficient in extracting the salt content of coastal saline soil, and can more accurately detect the salt content of coastal saline soil.

Claims

1. A method for determining the salinity in coastal saline soil using ultrasonic extraction, characterized in that, Includes the following steps: (1) The optimal extraction parameters for ultrasonic extraction treatment of coastal saline soil were determined by experiment. The extraction parameters included ultrasonic frequency and extraction time. (2) Weigh a certain amount of sieved, air-dried coastal saline soil and put it into a conical flask. Add distilled water into the conical flask according to the water-soil mass ratio. (3) After sealing the conical flask, put it into an ultrasonic cleaner, set the extraction parameters, and perform ultrasonic extraction treatment. (4) After ultrasonic extraction, 40 ml of suspension was taken from the conical flask into a centrifuge tube, centrifuged according to the centrifugation parameters, and a clear extract was prepared. (5) After centrifugation, accurately measure the clear extract from the centrifuge tube into a porcelain evaporating dish, evaporate it to dryness using a water bath, and then put it into an oven to continue drying until constant weight. (6) Calculate the salt content in coastal saline soil by measuring the mass of the residual solids after drying.

2. The method for determining the salinity in coastal saline soil using ultrasonic extraction according to claim 1, characterized in that, In step (1), the optimal extraction parameters are divided into two stages, using a dual-frequency alternating ultrasonic treatment method.

3. The method for determining the salinity in coastal saline soil using ultrasonic extraction according to claim 2, characterized in that, The dual-frequency alternating ultrasonic treatment method is as follows: in the first stage, 20KHz low-frequency ultrasound is used to destroy larger soil particles, and in the second stage, 40KHz high-frequency ultrasound is used to enhance the extraction ability of salt adsorbed in fine particles.

4. The method for determining the salinity in coastal saline soil using ultrasonic extraction according to claim 2, characterized in that, The first stage was set with an ultrasonic frequency of 20 kHz and an ultrasonic extraction time of 4 min; the second stage was set with an ultrasonic frequency of 40 kHz and an ultrasonic extraction time of 4 min.

5. The method for determining the salinity in coastal saline soil using ultrasonic extraction according to claim 1, characterized in that, In step (2), the sieve aperture is 1 mm and the water-to-soil mass ratio is 8:

1.

6. The method for determining the salinity in coastal saline soil using ultrasonic extraction according to claim 1, characterized in that, In step (4), the centrifugation parameters are set as follows: centrifugation speed 5000 r / min, centrifugation time 15 min.

7. The method for determining the salinity in coastal saline soil using ultrasonic extraction according to claim 1, characterized in that, In step (4), the amount of the clarified extract taken is 20 ml.

8. The method for determining the salinity in coastal saline soil using ultrasonic extraction according to claim 1, characterized in that, In step (5), the drying temperature is 90°C and the drying time is 2 hours.

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