Method for monitoring soil adsorbed water and condensed water under different depth conditions

Abstract

The invention discloses a method for monitoring soil adsorbed water and condensed water under different depth conditions, and relates to the technical field of soil monitoring. Comprising the following steps: acquiring in-situ soil samples under different underground water level burial depths and different lithologic conditions; placing the in-situ soil sample in an automatic weighing lysimeter, and setting corresponding temperature and humidity monitoring points according to different heights of the automatic weighing lysimeter; when the height of the in-situ soil sample filled in the automatic weighing type lysimeter reaches a certain temperature and humidity monitoring point position, continuously filling the soil sample until the automatic weighing type lysimeter is full; the weight change of the automatic weighing lysimeter at different heights is observed within a certain time; and classifying temperature and humidity data acquired by the temperature and humidity sensor according to the judgment conditions of the adsorbed water and the condensed water, and distinguishing the generation amounts of the adsorbed water and the condensed water in the automatic weighing lysimeter. According to the invention, based on the underground water burial depth and the water vapor adsorption and condensed water generation rule under different lithologic soil conditions, the quantitative characterization of the water vapor adsorption amount and the condensed water amount is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of soil monitoring, and more particularly to a method for monitoring soil adsorbed water and condensed water under conditions of different depths. Background Art

[0002] Water vapor adsorption and condensation jointly participate in the eco-hydrological cycle in arid and semi-arid areas, and play an important role in maintaining the stability of ecosystem structure and function.

[0003] At present, there is no unified research method for studying the formation law of soil condensation water. Common methods are mainly divided into two categories: model estimation and equipment measurement. Among them: The estimation models mainly include empirical models and physical models. The empirical model requires fewer parameters for calculation, but cannot fully reflect the physical mechanism of condensation formation and has poor calculation accuracy. The physical model is mostly based on the energy balance method and has higher calculation accuracy, but requires more parameters, and some parameters are difficult to obtain, and cannot distinguish between condensation and water vapor adsorption.

[0004] Nowadays, measurement instruments are widely used to analyze condensation formation patterns due to their simplicity. Key measurement methods include the panel method, artificial condensation surface method, leaf moisture sensor method, and micro-lysimeter method. However, these methods, due to their medium materials being significantly different from the soil medium, cannot provide true dew values ​​and cannot distinguish between condensation and water vapor adsorption. The micro-lysimeter method is the most widely used method for observing condensation and provides accurate results. However, most studies have difficulty distinguishing between water vapor adsorption and condensation during measurement.

[0005] In arid and semi-arid areas, water vapor adsorption is very common in the surface soil due to the influence of climate. The amount of water vapor absorbed by the surface soil is even greater than the amount condensed on the ground. The special structure of some plants is also conducive to absorbing water vapor in the atmosphere. However, when water vapor adsorption is included in the category of condensation water, it leads to an over-estimation of condensation water in arid and semi-arid areas.

[0006] Although a few studies have distinguished between the amount of water vapor adsorption and condensation water generated, the basis for the distinction is based on the relationship between surface temperature and dew point temperature. However, the temperature conditions inside the soil are significantly different from the surface temperature conditions. Dividing condensation water and water vapor adsorption only based on surface temperature will result in large errors in condensation water testing in shallow soil profiles. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a method and method for monitoring soil adsorbed water and condensed water under different depth conditions, so as to solve the technical problem of large error in the quantitative characterization test of soil water vapor adsorption and condensed water in the existing technology.

[0008] To achieve the above object, the present invention provides a method for monitoring soil adsorbed water and condensed water under different depth conditions, the monitoring method comprising the steps of: Step S1: obtaining in-situ soil samples under different groundwater depths and different lithologic conditions; Step S2: placing the in-situ soil sample in an automatic weighing lysimeter, and setting corresponding temperature and humidity monitoring points according to different heights of the automatic weighing lysimeter; Step S3: When the height of the in-situ soil sample filled in the automatic weighing lysimeter reaches a certain temperature and humidity monitoring point, after placing the temperature and humidity sensor, continue to fill the soil sample until the automatic weighing lysimeter is filled; Step S4: observing the weight changes of the automatic weighing lysimeters at different heights within a certain period of time; Step S5: Classifying the temperature and humidity data collected by the temperature and humidity sensor according to the discrimination conditions of adsorbed water and condensed water, and then distinguishing the generated amounts of adsorbed water and condensed water in the corresponding automatic weighing lysimeter.

[0009] Preferably, the automatic weighing lysimeter includes a micro lysimeter, a gravity sensor, a main control machine, a solar panel and a battery. The gravity sensor is fixed to the bottom of the micro lysimeter, the solar panel is electrically connected to the battery, and the battery is electrically connected to the gravity sensor and the main control machine respectively.

[0010] Preferably, the micro-lysimeter includes an inner cylinder, an outer cylinder, a weighing sensor, a concrete base and a temperature and humidity sensor; the outer cylinder is fixed on the concrete base, and the inner cylinder is fixed on the weighing sensor; a rubber sealing ring is connected to the top between the inner cylinder and the outer cylinder; the temperature and humidity sensor is used to measure the relative humidity and soil temperature of soil at different depths.

[0011] Preferably, the inner cylinder and the outer cylinder are both made of PVC material.

[0012] Preferably, the height range of the inner cylinder and the outer cylinder is 1-50 cm.

[0013] Preferably, the inner cylinder has a diameter of 10 cm and a thickness of 2 mm, and the outer cylinder has a diameter of 12 cm and a thickness of 2 mm.

[0014] Preferably, in step S2, the installation heights of the automatic weighing lysimeter include 2 cm, 5 cm, 10 cm, 20 cm and 50 cm.

[0015] Preferably, in step S5, the discrimination conditions between the adsorbed water and the condensed water are: When the soil temperature is higher than the dew point temperature and the relative humidity of the soil pores is lower than the relative humidity of the air, water vapor adsorption will occur. At this time, the weight gain of the micro-lysimeter belongs to the amount of adsorbed water generated; When the soil temperature is less than or equal to the dew point temperature, condensation water will be generated in the soil. At this time, the weight increase of the micro-lysimeter belongs to the amount of condensation water generated.

[0016] Preferably, in step S5, the calculation expression of the condensed water amount is: (1) in: The amount of condensed water in 3 hours; It is the mass difference between the total weight of the automatic weighing lysimeter at a certain moment and the previous moment; is the inner barrel radius of the microlysimeter, is the density of water, which is 1g / cm 3 .

[0017] The amount of water vapor adsorption or condensation at depths of 2-5cm, 5-10cm, 10-20cm, and 20-50cm is indirectly calculated using the difference in mass change between two lysimeters over the same time period. Taking 5-10cm as an example, the calculation expression for the amount of water vapor adsorption or condensation at this depth is: (2) in: The amount of condensed water in the soil at a depth of 5-10 cm in 3 hours; The mass difference between the total weight of the 5cm high automatic weighing lysimeter at a certain moment and the previous moment; The mass difference of the 10 cm height automatic weighing lysimeter in the same time period; Preferably, in step S1, the groundwater level is buried at depths of 1 m, 2 m, and 4 m, respectively, and the clays of different lithologies include fine sand, silt sand, and silty clay.

[0018] Compared with the prior art, the present invention has the following advantages and effects: In this application, the monitoring method of soil adsorbed water and condensed water under different depth conditions obtains in-situ soil samples under different groundwater level depths and lithologic conditions, and combines the setting of automatic weighing lysimeter and temperature and humidity monitoring points to achieve accurate monitoring of soil adsorbed water and condensed water; the automatic weighing lysimeter can accurately measure small changes in soil moisture, while the temperature and humidity monitoring points provide detailed environmental parameters. The combination of the two helps to accurately distinguish the amount of adsorbed water and condensed water generated, providing high-precision data support for soil moisture research. In addition, by continuously observing the weight changes of the automatic weighing lysimeter over a certain period of time, and combining the dynamic recording of temperature and humidity data, this method can realize the dynamic analysis of the process of soil adsorbed water and condensed water generation. Researchers can understand the changing trend of soil moisture and the mutual conversion process of adsorbed water and condensed water in different time periods, which provides a dynamic basis for revealing the dynamic balance mechanism of soil moisture and predicting soil moisture changes, and helps to deeply understand the soil moisture cycle process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of a flow chart of a method for monitoring soil adsorbed water and condensed water under different depth conditions according to an embodiment of the present invention; Figure 2 Schematic diagram of the structure of an automatic weighing lysimeter in an embodiment of the present invention; Figure 3 Schematic diagram of the internal structure of a micro-lysimeter in an embodiment of the present invention; Figure 4 Schematic diagram of the curve of the mass change of the micro-lysimeter and the relative humidity saturation / supersaturation time at different depths in an embodiment of the present invention; Figure 5 Schematic diagram of the results of daily average water vapor adsorption and condensation water under different soil types and different groundwater depths in an embodiment of the present invention.

[0020] Description of reference numerals: 1-Micro-lysimeter; 11-Inner cylinder; 12-Outer cylinder; 13-Weighing sensor; 14-Concrete base; 15-Temperature and humidity sensor; 16-Rubber sealing ring; 2- Gravity sensor; 3- Main control unit; 4- Solar panel; 5- Battery. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention. In describing the present invention, it should be noted that the terms "include" and "comprising" as used herein should be understood as inclusive and open-ended, rather than exclusive. Specifically, when the terms "include" and "comprising" and their synonyms are used in the specification and claims, they indicate the inclusion of the specified features, steps, or components. These terms should not be interpreted as excluding the presence of other features, steps, or components.

[0022] The precipitation in arid and semi-arid areas is far less than the potential evaporation, and condensation water, as an important water input to such areas, provides an important water source for the survival of animals and plants, microbial activities, etc. in arid and semi-arid areas.

[0023] Condensation forms when the surface of leaves or soil cools due to radiation, and the temperature reaches the dew point, or when the relative humidity reaches 100%. Compared to precipitation, condensation has advantages such as high frequency, stable production, and long duration. In some arid regions, the amount of condensation can even exceed precipitation.

[0024] In addition to condensation, adsorbed water also represents a significant water input in arid and semi-arid regions. Soil absorbs water vapor due to electromolecular forces. Water vapor adsorption occurs when the soil temperature is above the dew point and the relative humidity of the soil pores is lower than the relative humidity of the air. This is the key distinction between water vapor adsorption and condensation. The water vapor adsorption process is primarily influenced by the specific surface area of ​​soil particles. Although soil-adsorbed water vapor cannot be absorbed by plants, it plays a crucial role in filling soil moisture gaps in arid and semi-arid regions.

[0025] To solve the above technical problems, please refer to Figure 1 As shown, in one embodiment of the present invention, a method for monitoring soil adsorbed water and condensed water under different depth conditions is provided, and the monitoring method includes the steps of: Step S1: Obtain in-situ soil samples under different groundwater depths and different lithologic clay conditions.

[0026] In this step, soil sampling points at different groundwater depths and lithologic conditions are determined based on research needs. Then, professional sampling equipment, such as soil drills, are used to obtain representative in-situ soil samples to ensure that the collected soil samples can accurately reflect the soil characteristics under different groundwater levels and lithologic conditions. At the same time, during the collection process, the destruction of soil structure and changes in moisture content are avoided as much as possible to ensure the originality of the soil samples.

[0027] Step S2: placing the in-situ soil sample in an automatic weighing lysimeter, and setting corresponding temperature and humidity monitoring points according to the different heights of the automatic weighing lysimeter.

[0028] In this step, according to the height of the automatic weighing lysimeter, multiple temperature and humidity monitoring points are reasonably planned and set up. These monitoring points are distributed at different heights to comprehensively monitor the temperature and humidity changes at different positions inside the automatic weighing lysimeter.

[0029] Step S3: When the height of the in-situ soil sample filled in the automatic weighing lysimeter reaches a certain temperature and humidity monitoring point, after placing the temperature and humidity sensor, continue to fill the soil sample until the automatic weighing lysimeter is filled.

[0030] In this step, when the soil sample reaches a pre-set temperature and humidity monitoring point, the temperature and humidity sensor is accurately placed to ensure stability and that it does not affect the natural state of the soil sample. The soil sample is then added until the entire lysimeter is completely filled, while ensuring that the uniformity and density of the soil sample in the lysimeter are consistent with the original situ position.

[0031] Step S4: observing the weight changes of the automatic weighing lysimeters at different heights within a certain period of time; In this step, the weighing system of an automatic lysimeter is used to continuously record the weight change data at set intervals. The weighing system must be highly accurate and stable to accurately capture the subtle weight changes during the formation of soil water adsorption and condensation. The entire observation process should maintain relatively stable environmental conditions to avoid external factors such as airflow and sudden temperature fluctuations that may interfere with the weighing results. This ensures that the weight change data accurately and reliably reflects the dynamic changes in soil moisture.

[0032] Step S5: Classifying the temperature and humidity data collected by the temperature and humidity sensor according to the discrimination conditions of adsorbed water and condensed water, and then distinguishing the generated amounts of adsorbed water and condensed water in the corresponding automatic weighing lysimeter.

[0033] In this step, temperature and humidity data collected by the temperature and humidity sensors are combined with weight change data recorded by the automatic weighing lysimeter. This data is scientifically classified based on criteria for determining adsorbed and condensed water, such as temperature, humidity thresholds, and weight change rate. An established data model or discrimination algorithm is used to distinguish the amount of adsorbed and condensed water generated within the lysimeter at different heights. In-depth analysis of this data reveals the formation patterns and interrelationships of adsorbed and condensed water in soils at different groundwater depths and clay lithologies.

[0034] This monitoring method, by obtaining in-situ soil samples at varying groundwater depths and soil lithology, combined with an automatic gravimetric lysimeter and temperature and humidity monitoring stations, enables precise monitoring of both adsorbed and condensed water in the soil. The automatic gravimetric lysimeter accurately measures minute changes in soil moisture, while the temperature and humidity monitoring stations provide detailed environmental parameters. This combination helps accurately distinguish between adsorbed and condensed water production, providing high-precision data support for soil moisture research.

[0035] Furthermore, by continuously observing the weight changes of an automatic weighing lysimeter over a certain period of time, combined with dynamic recording of temperature and humidity data, this method enables dynamic analysis of the formation of soil adsorbed and condensed water. This allows researchers to understand the changing trends of soil moisture and the mutual conversion process between adsorbed and condensed water over different time periods. This provides a dynamic basis for revealing the dynamic balance mechanism of soil moisture and predicting soil moisture changes, contributing to a deeper understanding of the soil water cycle.

[0036] Specifically, see Figure 2 As shown, the automatic weighing lysimeter includes a micro lysimeter 1, a gravity sensor 2, a main control machine 3, a solar panel 4 and a battery 5. The gravity sensor 2 is fixed to the bottom of the micro lysimeter 1, the solar panel 4 is electrically connected to the battery 5, and the battery 5 is electrically connected to the gravity sensor 2 and the main control machine 3 respectively.

[0037] After the micro-lysimeter 1 is filled with an in-situ soil sample, the gravity sensor 2 monitors the micro-lysimeter 1's weight changes in real time and converts the weight data into electrical signals. These signals are transmitted via a connecting cable to the main control unit 3, which receives and stores the weight data and performs preliminary data processing, such as data correction and format conversion. During the day, the solar panel 4 converts solar energy into electricity to charge the battery 5. The battery 5 stores this energy and, when needed, provides a stable power supply to the main control unit 3 and gravity sensor 2, ensuring proper operation even in dark conditions such as at night or on cloudy days. The data processing software built into the main control unit 3 analyzes the collected weight data and, combined with environmental data collected by the temperature and humidity sensors, determines the production of adsorbed and condensed water in the soil. Based on pre-set procedures and criteria, the main control unit 3 automatically identifies the amount of adsorbed and condensed water produced and stores or transmits the results to a remote monitoring center.

[0038] Specifically, see Figure 3As shown, the micro-lysimeter 1 includes an inner cylinder 11, an outer cylinder 12, a weighing sensor 13, a concrete base 14 and a temperature and humidity sensor 15; the outer cylinder 12 is fixed on the concrete base 14, and the inner cylinder 11 is fixed on the weighing sensor 13; a rubber sealing ring 16 is connected to the top between the inner cylinder 11 and the outer cylinder 12; the temperature and humidity sensor is used to measure the relative humidity and soil temperature of the soil at different depths.

[0039] The collected in-situ soil samples are layered into the inner cylinder 11. Each layer is compacted appropriately to achieve a density close to the actual in-situ soil. During the filling process, be careful not to touch or damage the probe of the temperature and humidity sensor 15. When the soil sample is filled to near the top of the inner cylinder 11, a final leveling process is performed to ensure that the surface of the soil sample is flat and in close contact with the rubber sealing ring 16 at the top of the inner cylinder 11. The weighing sensor 13 monitors the weight changes of the inner cylinder 11 and the soil sample inside in real time and converts the weight data into electrical signals. These electrical signals are transmitted via connecting lines to the main control computer 3, which receives and stores the weight data and processes and analyzes the data. The temperature and humidity sensors measure the relative humidity and temperature of the test soil at different depths. These sensors regularly collect data and transmit it to the main control computer 3. The main control computer 3 integrates and analyzes the temperature and humidity data and, combined with the weight data, uses it to determine the generation of adsorbed water and condensed water in the soil. The main control unit 3 compiles the collected weight, temperature, and humidity data and transmits them to the remote monitoring center via wired or wireless communication methods (such as GPRS and Wi-Fi). At the remote monitoring center, researchers can view the micro-lysimeter monitoring data in real time and remotely analyze and manage soil moisture dynamics.

[0040] In a preferred embodiment of the present invention, both the inner cylinder 11 and the outer cylinder 12 are made of PVC. PVC has excellent chemical resistance and is resistant to corrosion from various chemical substances in the soil, such as acids, bases, and salts. This makes the inner cylinder 11 and the outer cylinder 12 less susceptible to corrosion during long-term soil monitoring, ensuring the service life of the equipment and measurement accuracy.

[0041] In a preferred embodiment of the present invention, the height range of the inner cylinder 11 and the outer cylinder 12 is 1-50 cm, so that the micro-lysimeter can adapt to the soil monitoring needs of different depths.

[0042] As a preferred embodiment of the present invention, the heights of the inner tube 11 and the outer tube 12 include five types: 2 cm, 5 cm, 10 cm, 20 cm, and 50 cm.

[0043] In a preferred embodiment of the present invention, the inner cylinder 11 has a diameter of 10 cm and a thickness of 2 mm, and the outer cylinder 12 has a diameter of 12 cm and a thickness of 2 mm.

[0044] In a preferred embodiment of the present invention, in step S2, the installation heights of the automatic weighing lysimeter include 2 cm, 5 cm, 10 cm, 20 cm and 50 cm.

[0045] In a preferred embodiment of the present invention, in step S5, the discrimination conditions between adsorbed water and condensed water are: When the soil temperature is higher than the dew point temperature and the relative humidity of the soil pores is lower than the relative humidity of the air, water vapor adsorption will occur. At this time, the weight gain of the micro-lysimeter belongs to the amount of adsorbed water generated; When the soil temperature is less than or equal to the dew point temperature, condensation water will be generated in the soil. At this time, the weight increase of the micro-lysimeter belongs to the amount of condensation water generated.

[0046] Therefore, by setting clear criteria for distinguishing between adsorbed and condensed water, it is possible to accurately distinguish whether the micro-lysimeter weight gain is due to water vapor adsorption or condensation. This helps improve the accuracy of soil moisture monitoring, deepens understanding of the formation mechanisms and changes in different forms of water in the soil, and provides reliable data support for soil moisture research.

[0047] In a preferred embodiment of the present invention, in step S5, the calculation expression of the condensed water amount is: (1) in: The amount of condensed water in 3 hours; It is the mass difference between the total weight of the automatic weighing lysimeter at a certain moment and the previous moment; is the inner barrel radius of the microlysimeter, is the density of water, which is 1g / cm 3 .

[0048] The amount of water vapor adsorption or condensation at depths of 2-5cm, 5-10cm, 10-20cm, and 20-50cm is indirectly calculated using the difference in mass change between two lysimeters over the same time period. Taking 5-10cm as an example, the calculation expression for the amount of water vapor adsorption or condensation at this depth is: (2) in: The amount of condensed water in the soil at a depth of 5-10 cm in 3 hours; The mass difference between the total weight of the 5cm high automatic weighing lysimeter at a certain moment and the previous moment; The mass difference of the 10 cm height automatic weighing lysimeter in the same time period; Since the direct observation data for water vapor adsorption and condensation are weight, formula (1) can be used to convert weight data into condensation expressed as height. By using formula (1) to calculate condensation, the weight change of the automatic weighing lysimeter can be accurately converted into condensation. This quantification method improves the measurement accuracy of condensation generation and enables researchers to more accurately understand the formation of condensation in soil.

[0049] In a preferred embodiment of the present invention, in step S1, the groundwater level is buried at depths of 1 m, 2 m, and 4 m, respectively, and the different lithologic clays include fine sand, silt sand, and silty clay.

[0050] Therefore, by setting different groundwater level depths (1m, 2m, 4m) and different lithologic clay conditions (fine sand, silt sand, and silty clay), more comprehensive and diverse soil moisture data can be obtained, which helps to gain a deeper understanding of the formation laws and dynamic change characteristics of soil adsorbed water and condensed water under different environmental conditions.

[0051] To further verify the accuracy of the monitoring method for soil adsorbed water and condensed water under conditions of different depths, the embodiment of the present invention selected a water environment monitoring station in a certain city and deployed 9 automatic weighing lysimeters with a depth of 10 cm and 9 automatic weighing lysimeters with a depth of 5 cm. These automatic weighing lysimeters were respectively deployed in soil columns with different groundwater levels (groundwater depths of 1m, 2m, and 4m) and different lithologies (fine sand, silt sand, and silty clay). A three-day monitoring period was carried out to explore the accuracy of the device under different groundwater levels and lithology conditions.

[0052] It is important to note that based on the monitoring data, the amounts of adsorbed and condensed water within the ranges of 0–5 cm, 5–10 cm, and 0–10 cm in different soil columns were distinguished, and the increased mass of the micro-lysimeter when the relative humidity of the soil was less than 100% was used as the amount of water vapor adsorption in the soil.

[0053] See Figure 4 As shown in the figure, in terms of generation time, based only on the total weight data of the 0-10 cm micro-lysimeter, it was found that except for the 4.5 m silty clay, which had 0.06 mm water vapor adsorption from 22:00 on August 21 to 1:00 the next day, there was no water vapor adsorption in other soil columns.

[0054] Larger differences were found when the analysis was based on the 0-5 cm and 5-cm microlysimeter data.

[0055] Overall, the 0-5cm water vapor adsorption time is mainly concentrated from 19:00 to 1:00 the next day, and the 5-10cm water vapor adsorption time is mainly from 10:00 to 13:00 during the day. The time difference between the two is exactly about 12 hours, and the frequency of water vapor adsorption at a depth of 5-10cm in each soil column is significantly lower than that at 0-5cm.

[0056] When calculating water vapor adsorption, the average value of water vapor adsorption on each day is calculated as follows: The average water vapor adsorption at a depth of 0-5 cm is 0.10 mm / d, and the average water vapor adsorption at a depth of 5-10 cm is 0.06 mm / d. Therefore, the water vapor adsorption and occurrence frequency at a depth of 0-5 cm are both higher than those at 5-10 cm.

[0057] The main reason is that the 0-5cm layer is more affected by evaporation, has a low moisture content, and is more susceptible to water vapor adsorption.

[0058] Secondly, based on the changes in lysimeter mass and the relative humidity saturation / supersaturation time at different depths (a fine sand 1m, b) the following results were obtained: Based on the 0-10cm and 5-10cm water vapor adsorption data, it was found that when the groundwater level was 1m, fine sand and silt sand rarely adsorbed water vapor, which could be ignored, and silty clay did not adsorb any water vapor; and based on the 0-5cm data analysis, it was found that the water vapor adsorption of silt sand in the shallow surface layer was much greater than that of fine sand and silty clay.

[0059] This is because the moisture content of the deeper layer of silt, such as at a depth of 15 cm, is greater than that of silty clay, which can provide more water vapor. Although its moisture content is lower than that of the fine sand column, the smaller particles of silt result in a lower capillary water rising rate than that of fine sand, making the surface soil of the silt sand drier. Therefore, the silt sand column adsorbs more water vapor than other rock soil columns. Under this groundwater depth condition, the water vapor adsorption is determined by both the groundwater depth and the soil properties.

[0060] Finally, as the groundwater depth increases, the amount of water vapor adsorption generally shows an increasing trend.

[0061] Compared with the groundwater depth of 1.0m, the average daily water vapor adsorption of fine sand and silty clay 0-5cm increased by 0.10mm and 0.21mm respectively when the groundwater depth was 4.5m. The water vapor adsorption of silt sand was the largest when the groundwater depth was 1m and 2.5m. At the groundwater depth of 4.5m, no water vapor adsorption occurred in the silt sand 0-5cm, and the water vapor adsorption of silt clay was the largest.

[0062] The water vapor adsorption of fine sand at a depth of 5-10 cm is still zero, while the water vapor adsorption of silt sand and silty clay increases significantly. Under the same groundwater level and depth, the water vapor adsorption of silt sand is the largest.

[0063] Although the water vapor adsorption capacity of 0-10 cm fine sand and silt is still very small, the water vapor adsorption capacity of 0-10 cm silty clay has a relatively large increase when the groundwater depth is 4.5 m.

[0064] Therefore, the response of water vapor adsorption of fine sand to changes in groundwater depth is mainly concentrated in the shallow surface layer of 0-5 cm, and the response of water vapor adsorption of silt sand and silty clay to changes in groundwater depth is obvious in the range of 0-10 cm.

[0065] See also Figure 5 As shown in the figure, the water vapor adsorption of 5-10 cm silt sand and silty clay increased at the burial depth of 2.5 m and 4.5 m, respectively. This is mainly because the water content of silt sand soil decreases significantly with the increase of groundwater burial depth, resulting in the silt sand water vapor adsorption at this layer responding more promptly to the changes in groundwater level.

[0066] The condensation time of 0cm water vapor is mainly between 00:40 and 7:00 in the morning. With the increase of groundwater depth, the condensation time at 5cm of each soil column (except for 4.5m silt sand) is shortened. Condensation water is generated only around 5-8am in the 4.5m fine sand soil column, and the duration is about 1 / 3 of that of the 1.0m fine sand soil column. No condensation water is generated at 5cm and 10cm in the 4.5m silty clay. There is no obvious pattern in the condensation time at 10cm of each soil column.

[0067] The main sources of water vapor for soil condensation are atmospheric water vapor and soil water vapor. The above rule is mainly due to the fact that the increase in groundwater depth causes a decrease in the amount of water vapor supplied by groundwater and soil, thus reducing the condensation time.

[0068] When the groundwater depth is the same, except for the 4.5m column of silty clay where coagulation only occurs at 0cm, the overall trend is that the finer the particles, the longer the coagulation time.

[0069] In terms of condensation water generation, the order of soil lithology is silty clay > silt sand > fine sand. The order of groundwater depth is 1.0m > 2.5m ≳ 4.5m. The order of condensation water generation depth is 0-5cm > 0-10cm > 5-10cm.

[0070] Taking the groundwater depth of 2.5m as an example, the average daily generation of condensation water in fine sand, silt sand and silty clay soil columns in the depth range of 0-10cm is 0.03mm, 0.08mm and 0.09mm respectively.

[0071] When the lithology is constant, although the amount of condensation water will decrease with the decrease of groundwater depth, the condensation water generation at 2.5 and 4.5 m in the range of 0-10 cm and 0-5 cm is very similar, indicating that the water vapor flux of condensation water from soil pores under these two burial depth conditions is similar, that is, the maximum depth of groundwater providing water vapor for groundwater when the groundwater level is 4.5 m.

[0072] Although the present invention is disclosed as above, the scope of protection disclosed by the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for monitoring soil adsorbed water and condensed water at different depths, characterized in that: The monitoring method comprises the steps of: Step S1: obtaining in-situ soil samples under different groundwater depths and different lithologic conditions; Step S2: placing the in-situ soil sample in an automatic weighing lysimeter, and setting corresponding temperature and humidity monitoring points according to different heights of the automatic weighing lysimeter; Step S3: When the height of the in-situ soil sample filled in the automatic weighing lysimeter reaches a certain temperature and humidity monitoring point, after placing the temperature and humidity sensor, continue to fill the soil sample until the automatic weighing lysimeter is filled; Step S4: observing the weight changes of the automatic weighing lysimeters at different heights within a certain period of time; Step S5: Classifying the temperature and humidity data collected by the temperature and humidity sensor according to the discrimination conditions of adsorbed water and condensed water, and then distinguishing the generated amounts of adsorbed water and condensed water in the corresponding automatic weighing lysimeter.

2. The method for monitoring soil adsorbed water and condensed water under different depth conditions according to claim 1, characterized in that: The automatic weighing lysimeter includes a micro lysimeter, a gravity sensor, a main control machine, a solar panel and a battery. The gravity sensor is fixed to the bottom of the micro lysimeter, the solar panel is electrically connected to the battery, and the battery is electrically connected to the gravity sensor and the main control machine respectively.

3. The method for monitoring soil adsorbed water and condensed water under different depth conditions according to claim 2, characterized in that: The micro-lysimeter includes an inner cylinder, an outer cylinder, a weighing sensor, a concrete base and a temperature and humidity sensor; the outer cylinder is fixed on the concrete base, and the inner cylinder is fixed on the weighing sensor; a rubber sealing ring is connected to the top between the inner cylinder and the outer cylinder; the temperature and humidity sensor is used to measure the relative humidity and soil temperature of soil at different depths.

4. The method for monitoring soil adsorbed water and condensed water under different depth conditions according to claim 3, characterized in that: The inner cylinder and the outer cylinder are both made of PVC material.

5. The method for monitoring soil adsorbed water and condensed water under different depth conditions according to claim 3, characterized in that: The height range of the inner cylinder and the outer cylinder is 1-50 cm.

6. The method for monitoring soil adsorbed water and condensed water under different depth conditions according to claim 3, characterized in that: The inner cylinder has a diameter of 10 cm and a thickness of 2 mm, and the outer cylinder has a diameter of 12 cm and a thickness of 2 mm.

7. The method for monitoring soil adsorbed water and condensed water at different depths according to claim 1, characterized in that: In step S2, the automatic weighing lysimeter is installed at heights including 2 cm, 5 cm, 10 cm, 20 cm and 50 cm.

8. The method for monitoring soil adsorbed water and condensed water at different depths according to claim 1, characterized in that: In step S5, the discrimination conditions between the adsorbed water and the condensed water are: When the soil temperature is higher than the dew point temperature and the relative humidity of the soil pores is lower than the relative humidity of the air, water vapor adsorption will occur. At this time, the weight gain of the micro-lysimeter belongs to the amount of adsorbed water generated; When the soil temperature is less than or equal to the dew point temperature, condensation water will be generated in the soil. At this time, the weight increase of the micro-lysimeter belongs to the amount of condensation water generated.

9. The method for monitoring soil adsorbed water and condensed water at different depths according to claim 1, characterized in that: In step S5, the calculation expression of the condensed water amount is: （1） in: The amount of condensed water in 3 hours; It is the mass difference between the total weight of the automatic weighing lysimeter at a certain moment and the previous moment; is the inner barrel radius of the microlysimeter, is the density of water, which is 1g / cm 3 .

10. The method for monitoring soil adsorbed water and condensed water at different depths according to claim 6, characterized in that: In step S1, the groundwater level is buried at depths of 1 m, 2 m, and 4 m, respectively, and the different lithologic clays include fine sand, silt sand, and silty clay.

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