A method for quantifying water distribution in soil pores based on CT scanning technology

Abstract

The application discloses a method for quantifying water distribution in soil pores based on CT scanning technology, and is characterized in that the method comprises the following steps: using a 2cm outer diameter PVC pipe to prepare undisturbed soil; using a method combining CT scanning and Avizo software to analyze the spatial distribution of soil water; and the specific steps are as follows: performing CT scanning reconstruction on the collected undisturbed soil column to obtain a CT scanning gray scale image; and processing the gray scale image obtained through CT scanning in Avizo software to obtain the accurate distribution of soil water-containing pores. In the application, the distribution state of soil water in soil pores in a natural state is determined by combining a CT scanning instrument with professional three-dimensional analysis software under the condition of undisturbed soil, and three-dimensional quantitative analysis of soil water distribution is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of agricultural engineering, in particular to a method for quantifying water distribution in soil pores based on CT scanning technology. BACKGROUND

[0002] So far, the complete measurement of water distribution in soil pores in a natural state cannot be achieved by experiments. Computed Tomography (CT) is a non-destructive testing technology that obtains the internal tomographic image of an object by detecting the difference in the attenuation coefficient of the rays passing through the object. The imaging process of X-rays is to scan the target object with X-rays, and when the X-rays pass through the internal part of the target object, the intensity of the rays passing through the target object is recorded by a detector, so as to calculate the attenuation coefficient of the X-rays in the target object; then a corresponding algorithm is used to solve the two-dimensional distribution matrix of the attenuation coefficient of the target object on the cross section and convert it into a gray scale distribution image; finally, various reconstruction algorithms are used to inversely solve the overall distribution matrix of the attenuation coefficient of the target object, and the final image is reconstructed. CT has been proposed as a feasible method to quickly and non-destructively visualize the three-dimensional structure of soil, and the porosity and pore morphology can be directly observed using CT images. Currently, some international researchers have used CT scanning as a cutting-edge method for studying the spatial network structure of soil.

[0003] Due to the limited difference in gray value between water and soil pores, it is difficult to directly quantify the distribution of water in soil by relying solely on CT scanning, so in the past, people generally used natural tracers such as ions and isotopes to measure their content, concentration, and spatial distribution over time in soil by directly or indirectly applying scanning instruments. However, the addition of tracers can affect the plant's absorption and utilization of soil water, thereby disrupting the natural state of soil water distribution; in terms of analysis software, the use of professional software such as Avizo (three-dimensional design visualization software) is less common, mainly relying on the built-in software of CT scanners or open-source software such as Image J (image processing software). SUMMARY

[0004] In view of the above technical problems in the related art, the present application provides a method for quantifying water distribution in soil pores based on CT scanning technology, which can overcome the above shortcomings of the prior art.

[0005] To achieve the above technical purposes, the technical solution of the present application is as follows:

[0006] A method for quantifying water distribution in soil pores based on CT scanning technology, comprising the following steps:

[0007] S1 using a 2cm outer diameter PVC pipe to prepare undisturbed soil;

[0008] S2 adopts the method combining CT scanning and Avizo software to analyze the spatial distribution of soil moisture;

[0009] The specific steps of S2 are as follows:

[0010] S21 carries out CT scanning reconstruction on the collected undisturbed soil column to obtain a CT scanning gray image;

[0011] S22 processes the gray image obtained by CT scanning in Avizo software to obtain the accurate distribution of soil water-containing pores:

[0012] S221 utilizes the gray histogram method in the Avizo software to divide the soil sample into soil matrix, soil water-containing pores and soil air-filled pores according to the distribution of the gray value in the gray histogram;

[0013] S222 deletes the pores near the PVC tube that are disturbed by the edge;

[0014] S223 selects the gray value range corresponding to the soil pores and the soil water-containing pores to interpret the soil pores and the soil pore water;

[0015] S224 adopts the Volume Rendering command to obtain the three-dimensional distribution diagram of the interpreted soil pores and soil pore water;

[0016] S225 utilizes the Segmentation module to perform voxel erosion and voxel expansion optimization on the root system to extract the three-dimensional spatial distribution of the root system in the undisturbed soil by using the Volum Rendering command;

[0017] S226 excludes the overlapping part of the interpreted water-containing pores and the root system data by using the And not Image command to obtain the accurate distribution of the soil water-containing pores.

[0018] Further, the root system is interpreted by using the growth method.

[0019] Further, the pore deletion in step S222 utilizes the Volume Edit tool.

[0020] Further, the soil pore and soil pore water interpretation in step S223 utilizes the Interactive Thresholding tool.

[0021] The present application has the beneficial effect that, under the condition of undisturbed soil, the distribution state of soil moisture in soil pores in the natural state is determined by combining the CT scanning instrument with professional three-dimensional analysis software, and three-dimensional quantitative analysis of the distribution of soil moisture is realized. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed in the embodiments will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only are some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art based on the accompanying drawings without creative effort are within the scope of the present application.

[0023] Figure 1 is a flow chart of the method for quantifying water distribution in soil pores based on CT scanning technology according to the embodiment of the present application;

[0024] Figure 2 is a gray scale histogram of the method for quantifying water distribution in soil pores based on CT scanning technology according to the embodiment of the present application;

[0025] Figure 3 is a soil pore three-dimensional visualization containing root system diagram of the method for quantifying water distribution in soil pores based on CT scanning technology according to the embodiment of the present application;

[0026] Figure 4 is a soil pore water distribution three-dimensional visualization containing root system diagram of the method for quantifying water distribution in soil pores based on CT scanning technology according to the embodiment of the present application;

[0027] Figure 5 is a root system three-dimensional visualization diagram of the method for quantifying water distribution in soil pores based on CT scanning technology according to the embodiment of the present application;

[0028] Figure 6 is a soil pore water distribution three-dimensional visualization diagram of the method for quantifying water distribution in soil pores based on CT scanning technology according to the embodiment of the present application;

[0029] Figure 7 is a soil pore water distribution three-dimensional visualization detail diagram of the method for quantifying water distribution in soil pores based on CT scanning technology according to the embodiment of the present application; DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present application.

[0031] As shown in Figure 1 the method for quantifying water distribution in soil pores based on CT scanning technology according to the embodiment of the present application, the steps of the method are as follows:

[0032] Because the soil moisture without tracer is not much different from the soil pore gray value, in order to ensure that the soil moisture is in a natural state, the diameter of the sampling sample is reduced and the resolution is improved, and a 2 cm outer diameter PVC pipe is used to prepare the undisturbed soil. The CT scanning and Avizo software are combined to analyze the spatial distribution of soil moisture. First, the undisturbed soil column collected is CT scanned and reconstructed to obtain a CT scanning gray image. Then, the gray image obtained by CT scanning is processed in Avizo software:

[0033] 1. The histogram of the gray value obtained by scanning the soil column sample is presented in the Project project management) interface Properties page Histogram, and the soil sample can be divided into soil matrix, soil water-containing pore and soil aerated pore according to the distribution of the gray value. However, a certain amount of roots are also included in the soil sample, and the gray value of the roots coincides with that of the soil water-containing pore, as shown in Figure 2 Therefore, the influence of the roots on the soil water-containing pore needs to be excluded by selecting the gray value range (threshold method).

[0034] 2. The pores near the PVC pipe disturbed by the edge are deleted by using the Volume Edit tool.

[0035] 3. The Interactive Thresholding command is used to select the gray value range (threshold method) corresponding to the soil pore and the soil water-containing pore, so as to interpret the soil pore and the soil pore moisture.

[0036] 4. The Volume Rendering command is used to obtain the three-dimensional distribution diagram of the soil pore and the soil pore moisture interpreted, as shown in Figure 3 、 4 .

[0037] 5. The Segmentation module is used to select the roots by using the magic wand tool, perform voxel erosion and voxel expansion (Selection-Grow / Shrink) to optimize the root extraction effect, and apply Volum Rendering to obtain the three-dimensional spatial distribution of the roots in the undisturbed soil, as shown in Figure 5 .

[0038] 6. The And not Image command is used to exclude the overlapping part of the interpreted water-containing pore and the root data, so as to obtain the accurate distribution of the soil water-containing pore, as shown in Figure 6 、 7 .

[0039] Computed Tomography (CT) is a non-destructive testing technology that obtains the internal tomographic image of an object by detecting the difference of the attenuation coefficient of the ray passing through the object. The imaging process of X-ray is to scan the target object with X-ray, and when the X-ray passes through the internal part of the target object, the intensity of the ray passing through the target object is recorded by the detector, so as to measure the attenuation coefficient of the X-ray in the target object; then a corresponding algorithm is used to solve the two-dimensional distribution matrix of the attenuation coefficient of the target object on the cross section and convert it into a gray distribution image; finally, various reconstruction algorithms are used to solve the overall distribution matrix of the attenuation coefficient of the target object, and the final image is reconstructed. The soil sample is composed of soil matrix, soil moisture, soil air and root system. Among them, the soil matrix, soil moisture and soil air are solid, liquid and gas respectively, so the attenuation coefficients obtained by CT scanning are different, and the gray value ranges corresponding to the reconstructed images are also different. In the case, 0-4500 is the soil aerated pore, 4500-8500 is the soil moisture, and above 8500 is the soil matrix.

[0040] In summary, by means of the above technical scheme of the present application, under the condition of undisturbed soil, the distribution state of soil moisture in soil pores in the natural state is determined by combining the CT scanning instrument with professional three-dimensional analysis software, and three-dimensional quantitative analysis of the distribution of soil moisture is realized.

[0041] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for quantifying water distribution in soil pores based on CT scanning technology, characterized in that, The method comprises the following steps: S1: using a 2cm outer diameter PVC pipe to prepare undisturbed soil; S2: using a CT scan combined with Avizo software to analyze the spatial distribution of soil moisture; The specific steps of S2 are as follows: S21: performing CT scan reconstruction on the collected undisturbed soil column to obtain a CT scan grayscale image; S22: processing the grayscale image obtained by CT scan in Avizo software to obtain the accurate distribution of soil water-containing pores: S221: using the grayscale histogram method in Avizo software to divide the soil sample into soil matrix, soil water-containing pores and soil air-filled pores according to the distribution of the grayscale value in the grayscale histogram; S222: deleting the pores near the PVC pipe that are disturbed by the edge; S223: selecting the grayscale value range corresponding to the soil pores and soil water-containing pores to interpret the soil pores and soil pore water; S224: using the Volume Rendering command to obtain the three-dimensional distribution map of the interpreted soil pores and soil pore water; S225: using the Segmentation module to perform voxel erosion and voxel expansion optimization on the root system to improve the extraction effect, and using the Volum Rendering to obtain the three-dimensional spatial distribution of the root system in the undisturbed soil; S226: excluding the overlapping part of the interpreted water-containing pores and root system data by using the And not Image command to obtain the accurate distribution of the soil water-containing pores.

2. The method for quantifying water distribution in soil pores based on CT scanning technology according to claim 1, characterized in that, The root system is interpreted by using the growth method.

3. The method for quantifying water distribution in soil pores based on CT scanning technology according to claim 1, characterized in that, In step S222, the pore deletion uses the Volume Edit tool.

4. The method for quantifying water distribution in soil pores based on CT scanning technology according to claim 1, characterized in that, In step S223, the soil pore and soil pore water interpretation uses the Interactive Thresholding tool.

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