Gas measuring device

Abstract

Evaluate the soil. [Solution] A gas measuring device for measuring a target gas present in soil is provided, comprising one or more suction units buried in the soil for drawing in gas, and a concentration measuring unit for measuring the concentration of the target gas contained in the gas drawn in by the suction units. The device further comprises a heating unit that heats at least a portion of the area in the soil from which the suction units draw in the gas, and the suction units may draw in the gas in the soil heated by the heating unit.

Description

Technical Field

[0001] The present invention relates to a gas measuring device.

Background Art

[0002] Conventionally, a method for calculating the fixed amount of carbon dioxide has been known (see, for example, Patent Document 1). Patent Document 1: Japanese Patent Application Laid-Open No. 2004-279073

Summary of the Invention

Problems to be Solved by the Invention

[0003] Easily measure the target gas contained in the soil.

Means for Solving the Problems

[0004] In order to solve the above problems, in one aspect of the present invention, a gas measuring device for measuring a target gas present in soil is provided. The gas measuring device may be buried in the soil and include one or more suction parts for sucking gas. Any of the gas measuring devices may include a concentration measuring part for measuring the concentration of the target gas contained in the gas sucked by the suction part.

[0005] Any of the gas measuring devices may include a heating part for heating at least a part of the region in the soil where the suction part sucks the gas. The suction part of any of the gas measuring devices may suck the gas in the soil heated by the heating part.

[0006] The heating part of any of the gas measuring devices may be buried in the soil and have an optical fiber for heating the soil by irradiating laser light.

[0007] Any of the gas measuring devices may include a control part for calculating the amount of the target gas fixed in the soil based on the temporal change in the concentration of the target gas.

[0008] The suction portion of any of the above gas measuring devices may have a head portion made of a hydrophobic and porous material. The suction portion of any of the above gas measuring devices may have a suction tube connected to the head portion for drawing in the gas that has passed through the head portion.

[0009] The suction unit of any of the above-mentioned gas measuring devices may return the gas, after it has been measured by the concentration measuring unit, to the soil.

[0010] The suction portion of any of the above gas measuring devices may have a head portion formed of a hydrophobic and porous material. The suction portion of any of the above gas measuring devices may have a suction tube connected to the head portion for drawing in the gas that has passed through the head portion. The suction portion of any of the above gas measuring devices may have a return tube connected to the head portion for returning the gas that has passed through the head portion back to the soil.

[0011] The head portion of any of the above gas measuring devices may have a suction cavity to which the suction tube is connected. The head portion of any of the above gas measuring devices may have a return cavity to which the return tube is connected. In any of the above gas measuring devices, a hydrophobic and porous material may be provided between the suction cavity and the return cavity.

[0012] The suction cavity of any of the above gas measuring devices may extend toward the return cavity. The return cavity of any of the above gas measuring devices may extend toward the suction cavity. The end of the suction cavity and the end of the return cavity of any of the above gas measuring devices may be positioned opposite each other.

[0013] In any of the above gas measuring devices, the material between the suction cavity and the return cavity may be different from the material in other areas of the head portion.

[0014] Any of the above gas measuring devices may include a pH measuring unit that measures the pH value of the soil in at least a portion of the area in which the suction unit draws in the gas.

[0015] Any of the above gas measuring devices may include an electrical conductivity measuring unit for measuring the electrical conductivity of the soil in at least a portion of the area in which the suction unit draws in the gas.

[0016] Any of the above gas measuring devices may include a plurality of suction units. Any of the above gas measuring devices may include a pump unit that is provided in common to the plurality of suction units and causes the gas to be drawn into the suction units. Any of the above gas measuring devices may include a plurality of valve units that are provided for each of the suction units and allow selection of which suction unit to draw in the gas.

[0017] Any of the above gas measuring devices may be provided with a plurality of suction units. Any of the above gas measuring devices may be provided with a heating unit for each of the suction units.

[0018] Any of the above gas measuring devices may be provided with a plurality of suction units. Any of the above gas measuring devices may be provided with a pH measuring unit for each of the suction units.

[0019] Any of the above gas measuring devices may be provided with a plurality of suction units. Any of the above gas measuring devices may be provided with an electrical conductivity measuring unit for each of the suction units.

[0020] Any of the above gas measuring devices may include an evaluation tank for containing the soil.

[0021] In any of the above-described gas measuring devices, the multiple suction units may be provided at different positions in the depth direction of the soil.

[0022] The above summary of the invention does not enumerate all of its features. Furthermore, subcombinations of these features may also constitute an invention.

Brief Description of the Drawings

[0023] [Figure 1] It is a diagram showing an example of the gas measurement device 100 according to one embodiment of the present invention. [Figure 2] It is a diagram for explaining an example of the method of heating the soil 14 by the heating unit 170. [Figure 3] It is a diagram showing another example of the gas measurement device 百. [Figure 4] It is a diagram showing a configuration example of the suction unit 110. [Figure 5] It is a diagram showing an example of the internal structure of the head unit 112. [Figure 6] It is a diagram showing the end portion 115 of the suction cavity 114 on the end face of the head unit 112. [Figure 7] It is a diagram showing another configuration example of the suction unit 110. [Figure 8] It is a diagram showing an example of the internal structure of the head unit 112. [Figure 9] It is a diagram showing the end portion 115 of the suction cavity 114 on the surface of the head unit 112. [Figure 10] It is a diagram showing another configuration example of the suction unit 110. [Figure 11] It is a diagram showing an example of the internal structure of the head unit 112. [Figure 12] It is a diagram showing another configuration example of the suction unit 110. [Figure 13] It is a diagram showing an example of the internal structure of the head unit 112. [Figure 14] It is a diagram showing another example of the suction cavity 114 and the return cavity 122. [Figure 15] It is a diagram showing another example of the suction cavity 114 and the return cavity 122. [Figure 16] It is a diagram showing another example of the suction cavity 114 and the return cavity 122. [Figure 17] It is a diagram showing another structural example of the head unit 112. [Figure 18] It is a diagram for explaining an operation example of the control unit 150. [Figure 19] This diagram illustrates another example of operation of the control unit 150. [Modes for carrying out the invention]

[0024] The present invention will be described below through embodiments of the invention, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustration. In addition, in a single drawing, elements having the same function and configuration may be denoted by a representative reference numeral, while reference numerals are omitted for others.

[0025] In this specification, when we refer to "identical" or "equal," we may include cases where there are errors due to manufacturing variations, etc. Such errors are, for example, within 10%. Also, in this specification, when we refer to "up" or "down," we may refer to up and down in the direction of gravity.

[0026] Figure 1 shows an example of a gas measuring device 100 according to one embodiment of the present invention. The gas measuring device 100 measures a target gas present in soil 14. The gas measuring device 100 may measure the concentration or amount of the target gas present in soil 14. The gas measuring device 100 may measure the concentration or amount of the target gas present as a gas in soil 14, the concentration or amount of the target gas including components fixed in soil 14, or the concentration or amount of the target gas including components emitted by microorganisms present in soil 14. Fixation of the target gas refers to a state in which the target gas is not released into the air by some means. As an example, the target gas is fixed by adsorption or fixation to other substances contained in soil 14.

[0027] The soil 14 to be measured may exist as part of the land, or it may be contained in some kind of container. The container may or may not seal the soil 14. The soil 14 may have plants planted in it, or it may not have plants planted in it. The soil 14 may be in a state before plants are planted, in a state where plants are planted and growing, in a state where plants have withered, or in a state where plants have been removed. The soil 14 may contain gravel and other materials in addition to soil. In Figure 1, the gravel contained in the soil 14 is represented by circles or ellipses.

[0028] The target gas is, for example, a greenhouse gas, but is not limited to this. The target gas may be CO2, N2O, both, or other gases. By measuring the target gas present in the soil 14, the soil 14 can be evaluated. Furthermore, when plants are planted in the soil 14, the effect of plants on the soil 14 can be evaluated by measuring the target gas in the soil 14 at multiple different time points.

[0029] The gas measuring device 100 comprises one or more suction units 110 and concentration measuring units 130. The gas measuring device 100 may further comprise at least one of the following components: one or more valve units 142, valve unit 144, pump unit 140, control unit 150, and heating / measuring unit 160.

[0030] The suction unit 110 is buried in the soil 14 and sucks in gas. The suction unit 110 may suck in gas from the soil 14 through a filter or the like that does not allow liquids and solids to pass through but allows gases to pass through. The filter may be a membrane or the like formed mainly from a hydrophobic porous material. The porous material is a fluororesin such as polytetrafluoroethylene (PTFE). The porous material has voids through which gas molecules can pass. The diameter of the voids is generally 5 μm or more and 20 μm or less, but is not limited thereto. The average diameter of the voids in the suction unit 110 may be 5 μm or more and 20 μm or less.

[0031] The gas measuring device 100 may have a plurality of suction units 110. The plurality of suction units 110 may be arranged at different positions in the depth direction perpendicular to the surface (ground) of the soil 14. This allows for measurement of the distribution of the target gas in the depth direction. The plurality of suction units 110 may also be arranged at different positions in the horizontal direction parallel to the surface of the soil 14.

[0032] The pump unit 140 draws gas from the soil 14 into each of the suction units 110. The pump unit 140 is connected to the suction units 110 by tubes or the like. As the pump unit 140 draws gas through the tubes or the like, the suction units 110 draw gas from the soil 14.

[0033] In this example, the pump unit 140 is provided in common for multiple suction units 110. In this example, a valve unit 142 is provided for each suction unit 110, and the multiple valve units 142 select which suction unit 110 will draw in the gas.

[0034] The concentration measuring unit 130 measures the concentration of the target gas contained in the gas drawn in by the suction unit 110. Unless otherwise specified, the gas concentration in this specification is the volume concentration. In this example, the concentration measuring unit 130 is provided between the suction unit 110 and the pump unit 140, and the gas drawn in by the pump unit 140 is supplied to it. The concentration measuring unit 130 may measure the concentration of the target gas contained in the gas by laser absorption spectroscopy (LAS). In laser absorption spectroscopy, the concentration of the target gas is measured by comparing the incident intensity of the wavelength component corresponding to the target gas in the laser irradiated onto the gas with the exit intensity of the same wavelength component in the laser after it has passed through the gas. The concentration of the target gas contained in the gas can be calculated from the attenuation of the exit intensity relative to the incident intensity and the optical path length through which the laser passed through the gas being measured. The concentration measuring unit 130 may use a quantum cascade laser (QCL) as the light source for laser absorption spectroscopy. The oscillation wavelength of a quantum cascade laser can be swept by controlling the current. Since the wavelength sweep range of the quantum cascade laser includes wavelengths to which CO2 and N2O are sensitive, it is suitable for measuring these target gases.

[0035] Valve 144 switches whether or not to introduce a reference gas to the concentration measuring unit 130. The reference gas may be a gas whose concentration is known, or it may be any other gas. The concentration measuring unit 130 may be calibrated by using the reference gas. The reference gas may be a gas in the space directly above the soil 14. In this case, the concentration of the target gas in the space can be compared with the concentration of the target gas in the soil 14. Valve 142 and valve 144 are, for example, solenoid valves, but are not limited to these.

[0036] The control unit 150 controls each component of the gas measuring device 100. For example, the control unit 150 may control multiple valve units 142 and 144, control the concentration measuring unit 130, or control the heating and measuring unit 160. The control unit 150 may also receive measurement results and operation results from each component of the gas measuring device 100. The control unit 150 may display these results to the user.

[0037] The heating and measuring unit 160 comprises at least one of the heating unit 170, the pH measuring unit 180, and the EC measuring unit 190. The heating and measuring unit 160 may further include a temperature measuring unit and a humidity measuring unit.

[0038] The heating unit 170 heats at least a portion of the area in the soil 14 where the suction unit 110 draws in gas. The suction unit 110 may draw in gas in the soil heated by the heating unit 170. By heating the soil 14, the target gas that was fixed in the soil 14 can be changed into a gas that can be drawn in. This allows the gas measuring device 100 to measure the concentration or amount of the target gas in the soil 14, including the components that were fixed in the soil 14. The heating unit 170 may heat the soil 14 so that the temperature of the soil 14 in contact with the surface of the suction unit 110 rises. The temperature measuring unit described above may measure the surface temperature of the suction unit 110. The heating unit 170 may heat the soil 14 so that the temperature measured by the temperature measuring unit, or the temperature rise, reaches a set temperature. The temperature rise of the surface of the suction unit 110 by the heating unit 170 may be 5°C or more, or 10°C or more. Even a temperature increase of about 5°C can vaporize at least a portion of the fixed target gas. The temperature increase on the surface of the suction section 110 due to the heating section 170 may be 30°C or less, 20°C or less, or 10°C or less.

[0039] The heating unit 170 may heat the soil 14 for a set measurement period. The heating unit 170 may heat the soil 14 so that the temperature measured by the temperature measuring unit is maintained at a predetermined set value during the measurement period. The concentration measuring unit 130 may measure the concentration of the target gas at multiple timings during the period when the heating unit 170 is heating the soil 14. The amount of gaseous increase over time of the target gas changes according to the total amount of target gas fixed in the soil 14 in the area heated by the heating unit 170. The control unit 150 may estimate the total amount of target gas fixed in the soil 14 from the pattern of change in the concentration of the target gas. For example, the faster the change in the concentration of the target gas, the greater the estimated total amount of target gas fixed in the soil 14.

[0040] If the soil 14 contains microorganisms that produce the target gas, the amount of the target gas produced by the microorganisms changes depending on the temperature of the soil 14. For example, the higher the temperature of the soil 14, the more active the microorganisms become, and the more target gas may be produced. The concentration measuring unit 130 may measure the concentration of the target gas contained in the gas drawn in by the suction unit 110 for each temperature of the soil 14. The control unit 150 may estimate the amount of microorganisms contained in the soil 14 by comparing the concentrations of the target gas for each temperature. For example, the greater the increase in the concentration of the target gas with increasing temperature, the greater the estimated amount of microorganisms contained in the soil 14.

[0041] The pH measuring unit 180 measures the pH value of the soil 14 in at least a portion of the area where the suction unit 110 draws in gas. The pH measuring unit 180 may also measure the pH value of the soil 14 in the area in contact with the suction unit 110. Depending on the pH value of the soil 14, the ease with which the target gas fixed in the soil 14 can be vaporized, the activity level of microorganisms, or their responsiveness to temperature increases may change. Therefore, by measuring the concentration of the target gas in the soil 14 along with the pH value of the soil 14, the soil 14 can be evaluated with greater accuracy.

[0042] The EC measuring unit 190 measures the electrical conductivity (EC) of the soil 14 in at least a portion of the area where the suction unit 110 draws in gas. The EC measuring unit 190 may measure the electrical conductivity of the soil 14 in the area in contact with the suction unit 110. Depending on the electrical conductivity of the soil 14, the ease with which the target gas fixed in the soil 14 can be vaporized, the activity level of microorganisms, or their responsiveness to temperature increases may change. Therefore, by measuring the concentration of the target gas in the soil 14 along with the electrical conductivity of the soil 14, the soil 14 can be evaluated with greater accuracy.

[0043] As shown in Figure 1, if multiple suction sections 110 are provided, a heating section 170 may be provided for each suction section 110. A pH measuring section 180 may also be provided for each suction section 110. An EC measuring section 190 may also be provided for each suction section 110. Other measuring sections of the heating and measuring section 160 may also be provided for each suction section 110.

[0044] Figure 2 illustrates an example of a method for heating soil 14 using a heating unit 170. In this example, the heating unit 170 has an optical fiber 172. The optical fiber 172 is embedded in the soil 14 and heats the soil 14 by irradiating it with laser light. In the soil 14, the optical fiber 172 irradiates at least a portion of the region 111 in which the suction unit 110 sucks in gas with laser light, thereby locally heating the region 111. By using laser light, the area to be heated can be controlled with high precision. In addition, since laser light enables localized heating, the influence on the concentration measurement of the target gas by other suction units 110 can be reduced.

[0045] The extent of region 111 may vary depending on the size of the suction section 110, the gas suction pressure by the pump section 140, etc. Region 111 is the area in which the existing gas is sucked in by the suction section 110, but region 111 may also be considered to be an area within a distance from the suction section 110 that is within 5 times the maximum width W of the part of the suction section 110 formed of porous material. The heating section 170 may locally heat at least a portion of this area in the vicinity of the suction section 110.

[0046] The optical fiber 172 may be fixed to the suction section 110. This makes it easier to heat the area near the suction section 110. The pH measuring section 180 and the EC measuring section 190 may also be fixed to the suction section 110. The heating section 170 may have a heater, such as an electric heating wire that converts electricity into heat, instead of the optical fiber 172.

[0047] Figure 3 shows another example of the gas measuring device 100. This example of the gas measuring device 100 differs from the example described in Figures 1 and 2 in that it further includes an evaluation tank 10 for containing soil 14. The other structures are the same as those of either example described in Figures 1 and 2.

[0048] The evaluation tank 10 in this example contains soil 14, a gas sensor 16, plants 18, a water supply pipe 20, and a drainage pipe 22. The plants 18 have roots in the soil 14 and stems and leaves growing above the soil 14. The plants 18 fix CO2 in their bodies through photosynthesis and release CO2 through respiration. As an example, plants 18 fix CO2 in their bodies in the form of cellulose. The plants 18 include various plants such as vegetables, ornamental plants, and trees. The plants 18 perform photosynthesis and respiration and grow inside the evaluation tank 10. In other words, so-called soil cultivation is carried out in the evaluation tank 10 in this example.

[0049] The gas sensor 16 measures the concentration of the target gas in the space above the soil 14 (above the ground) in the evaluation tank 10. In this example, the gas sensor 16 measures the concentration of CO2.

[0050] The water supply pipe 20 is located below the evaluation tank 10 and supplies water and nutrient solution (hereinafter sometimes collectively referred to as water supply) from the outside. The drain pipe 22 discharges excess water and other liquids (hereinafter sometimes referred to as drainage) from inside the evaluation tank 10. A liquid sensor 24 for measuring the carbon dioxide concentration in the liquid may be attached to the drain pipe 22. The evaluation tank 10 may also be provided with a light source 26 whose wavelength and intensity of light can be controlled. The light source 26 can, for example, simulate an environment that alternates between day and night.

[0051] Similar to the examples in Figures 1 and 2, one or more suction units 110 are buried in the soil 14. Multiple suction units 110 may be provided at different positions in the depth direction of the soil 14. With this configuration, the concentration of the target gas in the soil 14 can be measured while plants 18 are being cultivated. In the evaluation tank 10, plants 18 are cultivated for a predetermined period of time. For example, plants 18 may be cultivated from the seed stage until they wither. The gas measuring device 100 may measure the target gas at multiple timings during the cultivation period of the plants 18. This makes it possible to measure the effect of the plants 18 on the soil 14 according to the state of the plants 18. The gas measuring device 100 may measure the target gas at predetermined intervals throughout the entire cultivation period. This makes it possible to calculate the time change in the concentration of the target gas (e.g., the time derivative of the concentration) over any given period.

[0052] The gas measuring device 100 may record information indicating the state of the plant 18 in association with the measurement results of the target gas. Information indicating the state of the plant 18 may be information regarding the size of the plant 18, such as the depth of the roots, the number of roots, the thickness of the roots, the depth of the stem, the thickness of the stem, the number of leaves, and the total area of ​​the leaves. The gas measuring device 100 may also record an image of the plant 18 as information indicating the state of the plant 18. Information indicating the state of the plant 18 may also be the period since cultivation of the plant 18 began.

[0053] The gas measuring device 100 may record information indicating the cultivation environment of the plant 18 in association with the measurement results of the target gas. Information indicating the cultivation environment may include, for example, the intensity of light irradiated by the light source 26, the temperature and humidity inside the evaluation chamber 10, and the measurement results from the gas sensor 16.

[0054] The evaluation tank 10 may provide a closed system environment. A closed system is a system in which there is no exchange of substances other than the target gas between the system and the outside, and a system in which there is no exchange of substances other than the target gas and feedwater / wastewater between the system and the outside.

[0055] Figure 4 shows an example of the configuration of the suction unit 110. In this example, the suction unit 110 has a head unit 112 and a suction tube 113. The head unit 112 is made of a hydrophobic and porous material. As mentioned above, the porous material is PTFE as an example. The head unit 112 may be entirely buried in the soil 14. In this example, the head unit 112 is cylindrical, but the shape of the head unit 112 is not limited to this. Gases in the soil 14 permeate from the surface of the head unit 112 into the interior of the head unit 112.

[0056] The suction tube 113 is connected to the head portion 112. The suction tube 113 draws in the gas that has passed through the head portion 112. In this example, the suction tube 113 is connected to one end face of the cylindrical head portion 112. The suction tube 113 may also be inserted inside the head portion 112.

[0057] The maximum width of the head portion 112 (in this example, the length in the longitudinal direction of the cylindrical shape) may be 10 cm or less. The maximum width of the head portion 112 may also be 5 cm or less.

[0058] Figure 5 shows an example of the internal structure of the head portion 112. Inside the head portion 112 of this example, a suction cavity 114 is provided, which is connected to a suction tube 113. The tip of the suction tube 113 may be inserted into the suction cavity 114. However, at least a portion of the suction cavity 114 is an area into which the suction tube 113 is not inserted.

[0059] The suction cavity 114 has an end 115 exposed on the surface of the head portion 112, an end 116 on the opposite side of the end 115, and a side surface 117 between the end 115 and the end 116. A suction tube 113 is connected to the end 115.

[0060] In this example, the suction cavity 114 is provided extending in the longitudinal direction of the head portion 112. The suction cavity 114 does not penetrate the head portion 112, and its end portion 116 is provided inside the head portion 112.

[0061] The pump unit 140 draws in gas through the suction tube 113, causing the gas from the soil 14 to permeate from the surface of the head unit 112 to the suction cavity 114. The gas that reaches the suction cavity 114 is supplied to the concentration measuring unit 130 through the suction tube 113.

[0062] The suction cavity 114 may be located at the center of the head portion 112 in a cross-section perpendicular to the extension direction of the suction cavity 114. In this specification, the direction in which the suction cavity 114 extends may be referred to as the extension direction, and the direction perpendicular to the extension direction may be referred to as the radial direction. The distance r between the end portion 116 and the surface of the head portion 112 may be equal to the distance r between the side portion 117 and the surface of the head portion 112. This allows for uniform suction of gas around the head portion 112. If the distance r between the side portion 117 and the surface of the head portion 112 is not uniform, the average value of the distance r over the entire head portion 112 may be used. Similarly, the average value may be used for other distances, lengths, widths, etc., described in this specification.

[0063] Figure 6 shows the end portion 115 of the suction cavity 114 at the end face of the head portion 112. The end portion 115 may be located at the center of the end face.

[0064] Figure 7 shows another example of the suction unit 110 configuration. In this example, the shape of the head unit 112 differs from the example shown in Figure 4. The other structures are the same as those described in any of the examples from Figures 4 to 6.

[0065] The head portion 112 in this example is spherical. The suction tube 113 in this example is connected to one of the positions on the surface of the spherical head portion 112. The suction tube 113 may also be inserted inside the head portion 112.

[0066] The diameter of the head portion 112 may be 10 cm or less. The diameter of the head portion 112 may be 5 cm or less.

[0067] Figure 8 shows an example of the internal structure of the head portion 112. Similar to the example in Figure 5, the head portion 112 in this example is also provided with a suction cavity 114 that is connected to the suction tube 113.

[0068] In this example, the suction cavity 114 extends from the surface of the head portion 112 toward the center of the head portion 112. The region in which the suction cavity 114 is provided may include the center of the head portion 112. The suction cavity 114 does not penetrate the head portion 112, and its end portion 116 is located inside the head portion 112. The distance r between the end portion 116 and the surface of the head portion 112 may be equal to the distance r between the side surface 117 and the surface of the head portion 112. This allows for uniform suction of gas around the head portion 112.

[0069] Figure 9 shows the end portion 115 of the suction cavity 114 on the surface of the head portion 112. As shown in Figure 8, the suction cavity 114 may be provided extending in a direction perpendicular to the surface of the head portion 112.

[0070] Figure 10 shows another example of the configuration of the suction unit 110. In this example, the suction unit 110 returns the gas measured by the concentration measuring unit 130 to the soil 14. The measured gas may be supplied to the suction unit 110 by the pump unit 140. If multiple suction units 110 are provided, the suction unit 110 that sucks in the gas and the suction unit 110 to which the gas is returned may be the same. In other words, the measured gas may be returned to its original position in the soil 14. In other examples, the suction unit 110 that sucks in the gas and the suction unit 110 to which the gas is returned may be different.

[0071] The suction unit 110 in this example further includes a return tube 118 compared to the example described in Figures 4 to 9. The other structures are the same as those of any of the examples described in Figures 4 to 9. The return tube 118 is connected to the head unit 112 and returns the gas to the soil 14 by passing it through the head unit 112. In this example, the return tube 118 is connected to the end face of the cylindrical head unit 112 opposite to the suction tube 113. The return tube 118 may also be inserted inside the head unit 112.

[0072] Figure 11 shows an example of the internal structure of the head portion 112. In this example, the head portion 112 is provided with a return cavity 122 in addition to the suction cavity 114. The tip of the return tube 118 may be inserted into the return cavity 122. However, at least a portion of the return cavity 122 is an area into which the return tube 118 is not inserted.

[0073] The return cavity 122 has an end 119 exposed on the surface of the head portion 112, an end 120 on the opposite side of the end 119, and a side surface 121 between the end 119 and the end 120. A return tube 118 is connected to the end 119.

[0074] In this example, the return cavity 122 is provided extending in the longitudinal direction of the head portion 112. In this example, a hydrophobic and porous material is provided between the suction cavity 114 and the return cavity 122. In other words, the suction cavity 114 and the return cavity 122 in this example are not connected. The material between the suction cavity 114 and the return cavity 122 may be the same as or different from the material in other areas of the head portion 112.

[0075] In this example, the suction cavity 114 extends from its end 115 toward the return cavity 122. The return cavity 122 extends from its end 119 toward the suction cavity 114. The end 116 of the suction cavity 114 and the end 120 of the return cavity 122 may be positioned opposite each other in the direction of extension of each cavity.

[0076] The pump unit 140 may simultaneously draw in gas through the suction tube 113 and recirculate gas through the return tube 118. By drawing in gas through the suction tube 113, gas permeates from the surface of the head unit 112 to the suction cavity 114. By recirculating gas through the return tube 118, gas permeates from the return cavity 122 to the surface of the head unit 112. In addition, some of the gas recirculated by the return tube 118 permeates from the return cavity 122 to the suction cavity 114. In other words, the pump unit 140 may circulate some of the gas through the suction unit 110.

[0077] In this example, the gas to be measured can be circulated while partially exchanging the gas in the soil 14 with the circulating gas. Therefore, it is possible to measure the temporal fluctuations of the target gas concentration in the soil 14 in real time while preventing a large amount of the target gas from being lost in the soil 14 due to concentration measurement.

[0078] Let L be the distance between end 116 and end 120 in the extension direction. The mixing ratio of the gas circulating from the return cavity 122 to the suction cavity 114 and the gas drawn in from the soil 14 can be adjusted by the distance L and the distance r. Increasing the distance L decreases the proportion of circulating gas, and decreasing the distance L increases the proportion of circulating gas. Similarly, increasing the distance r decreases the proportion of gas drawn in from the soil 14, and decreasing the distance r increases the proportion of gas drawn in from the soil 14. The distances L and r may be determined according to the mixing ratio to be achieved. The distance L may be greater than, less than, or the same as the distance r.

[0079] Figure 12 shows another example of the suction unit 110 configuration. The suction unit 110 in this example differs from the example shown in Figure 10 in that the shape of the head portion 112 is spherical. The other structures are the same as those of either example described in Figures 10 and 11.

[0080] Figure 13 shows an example of the internal structure of the head portion 112. In this example, the head portion 112 is also provided with a return cavity 122 that is connected to the return tube 118, similar to the example in Figure 11.

[0081] Figure 14 shows another example of the suction cavity 114 and the return cavity 122. The structure other than the suction cavity 114 and the return cavity 122 is the same as in any of the examples described in Figures 10 to 13. In this example, the suction cavity 114 and the return cavity 122 are connected by a connecting cavity 123. However, the diameter of the connecting cavity 123 is smaller than that of either the suction cavity 114 or the return cavity 122. By adjusting the length and diameter of the connecting cavity 123, the amount of gas circulating from the return cavity 122 to the suction cavity 114 can be adjusted.

[0082] Figure 15 shows another example of the suction cavity 114 and return cavity 122. The structure other than the suction cavity 114 and return cavity 122 is the same as in any of the examples described in Figures 10 to 13. In this example, the end 116 of the suction cavity 114 has a tapered shape, decreasing in diameter as it approaches the return cavity 122. Similarly, the end 120 of the return cavity 122 in this example has a tapered shape, decreasing in diameter as it approaches the suction cavity 114. The amount of gas circulating from the return cavity 122 to the suction cavity 114 can also be adjusted by adjusting the length and angle of the tapered shape.

[0083] Figure 16 shows another example of the suction cavity 114 and the return cavity 122. The structure other than the suction cavity 114 and the return cavity 122 is the same as in any of the examples described in Figures 10 to 13. In this example, the end 116 of the suction cavity 114 and the end 120 of the return cavity 122 have a tapered shape, similar to the example in Figure 15, and their ends are connected by a connecting cavity 123. This structure also allows for adjustment of the amount of gas circulating from the return cavity 122 to the suction cavity 114.

[0084] Figure 17 shows another example of the structure of the head portion 112. In this example, the head portion 112 has a gap portion 125 and a main portion 124. The structure other than the gap portion 125 and the main portion 124 is the same as in any of the examples described in Figures 10 to 17.

[0085] The gap portion 125 is the region in the head portion 112 between the suction cavity 114 and the return cavity 122. The portion of the head portion 112 that overlaps with the region between the suction cavity 114 and the return cavity 122 in the radial direction may also be included in the gap portion 125. The main portion 124 is the region in the head portion 112 other than the gap portion 125.

[0086] The material of the gap section 125 may be different from the material of the main section 124. By adjusting the material of the gap section 125, the amount of gas circulating from the return cavity 122 to the suction cavity 114 can be adjusted. The average diameter of the voids in the gap section 125 may be different from the average diameter of the voids in the main section 124, and the density of the voids in the gap section 125 may be different from the density of the voids in the main section 124. By reducing the average diameter or density of the voids in the gap section 125, the amount of gas circulating from the return cavity 122 to the suction cavity 114 can be reduced, and by increasing the average diameter or density of the voids in the gap section 125, the amount of gas circulating from the return cavity 122 to the suction cavity 114 can be increased.

[0087] Figure 18 illustrates an example of the operation of the control unit 150. In this example, the concentration measuring unit 130 detects the concentration of the target gas while the soil 14 is heated by the heating unit 170. The control unit 150 calculates the amount of target gas fixed in the soil 14 based on the time change in the concentration of the target gas.

[0088] As described above, the target gas fixed in the soil 14 is vaporized by heating the soil 14. The more target gas fixed in the soil 14, the more target gas will be vaporized by heating. Therefore, the amount of target gas fixed in the soil 14 can be estimated from the time change (slope Δ) of the target gas concentration. The time change (slope Δ) of the target gas concentration may be the value obtained after a predetermined time has elapsed since the start of heating. The relationship between the slope Δ when the soil 14 is heated to a predetermined temperature and the amount of target gas may be obtained experimentally in advance.

[0089] As described above, when soil 14 is heated, the target gas fixed in soil 14 becomes a gas, and the amount of target gas emitted by microorganisms may also increase. On the other hand, the gasification of the target gas due to heating is observed relatively early after the start of heating. In addition, the increase in microbial emissions due to heating is observed relatively late after the start of heating.

[0090] The control unit 150 may estimate the amount of target gas fixed in the soil 14 from the time change (slope Δ) of the concentration of the target gas at the point when a predetermined first period T1 has elapsed from the start of heating of the soil 14. The control unit 150 may estimate the amount of microorganisms present in the soil 14 from the increase in the concentration of the target gas at the point when a predetermined second period has elapsed from the start of heating of the soil 14. This increase may be, for example, the increase from the concentration of the target gas at the start of heating. The second period is longer than the first period T1. For example, the first period T1 may be 10 seconds or less, or 1 minute or less. The second period may be 10 minutes or more, or 1 hour or more.

[0091] Figure 19 is a diagram illustrating an example of the operation of the control unit 150. In this example, the concentration measuring unit 130 detects the concentration of the target gas by repeatedly switching between a state in which the soil 14 is heated by the heating unit 170 and a state in which it is not heated. The control unit 150 may estimate the amount of microorganisms present in the soil 14 based on the increase in the concentration of the target gas ΔD at the time a second period T2 has elapsed since the start of heating. The increase ΔD may be the increase relative to the concentration of the target gas at the start of heating. As described above, the second period T2 may be longer than the first period T1. It is preferable that the second period T2 is long enough for the measured value of the concentration of the target gas to converge to a constant value. The control unit 150 may obtain the increase ΔD multiple times by repeatedly switching between a state in which the soil 14 is heated and a state in which it is not heated multiple times. The control unit 150 may estimate the amount of microorganisms present in the soil 14 from the average value of the increase ΔD. The relationship between the increase ΔD when soil 14 is heated to a predetermined temperature and the amount of microorganisms can be experimentally obtained in advance.

[0092] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention. [Explanation of Symbols]

[0093] 10...Evaluation tank, 14...Soil, 16...Gas sensor, 18...Plants, 20...Water supply pipe, 22...Drainage pipe, 24...Submersible sensor, 26...Light source, 100...Gas measuring device, 110...Suction section, 111...Area, 112...Head section, 113...Suction tube, 114...Suction cavity, 115...End, 116...End, 117...Side, 118...Return tube Tube, 119...end, 120...end, 121...side, 122...return cavity, 123...connecting cavity, 124...main section, 125...gap section, 130...concentration measuring section, 140...pump section, 142, 144...valve section, 150...control section, 160...heating and measuring section, 170...heating section, 172...optical fiber, 180...pH measuring section, 190...EC measuring section

Claims

1. A gas measuring device for measuring target gases present in soil, The aforementioned soil is buried and includes one or more suction units for drawing in gas, The suction unit includes a concentration measuring unit that measures the concentration of the target gas contained in the gas aspirated by the suction unit. A gas measuring device equipped with the following features.

2. The soil further comprises a heating unit that heats at least a portion of the area in which the suction unit draws in the gas, The suction unit sucks the gas from the soil heated by the heating unit. The gas measuring device according to claim 1.

3. The heating unit is embedded in the soil and has an optical fiber that heats the soil by irradiating it with laser light. The gas measuring device according to claim 2.

4. The system further includes a control unit that calculates the amount of the target gas fixed in the soil based on the time change in the concentration of the target gas. The gas measuring device according to claim 2.

5. The suction section is A head portion formed from a hydrophobic and porous material, A suction tube connected to the head portion for drawing in the gas that has passed through the head portion, A gas measuring device according to claim 1, having the following features.

6. The suction unit returns the gas, which has been measured by the concentration measuring unit, to the soil. The gas measuring device according to claim 1.

7. The suction section is A head portion formed from a hydrophobic and porous material, A suction tube connected to the head portion for drawing in the gas that has passed through the head portion, A return tube connected to the head portion, which allows the gas to pass through the head portion and return it to the soil. A gas measuring device according to claim 6, having the following features.

8. The head portion is, A suction cavity to which the aforementioned suction tube is connected, The return tube is connected to the return cavity and Includes, A hydrophobic and porous material is provided between the suction cavity and the return cavity. The gas measuring device according to claim 7.

9. The suction cavity extends toward the return cavity, The return cavity extends toward the suction cavity, The end of the suction cavity and the end of the return cavity are positioned opposite each other. The gas measuring device according to claim 8.

10. The material between the suction cavity and the return cavity is different from the material in other areas of the head portion. The gas measuring device according to claim 8.

11. The suction unit further comprises a pH measuring unit for measuring the pH value of the soil in at least a portion of the area where the suction unit draws in the gas. The gas measuring device according to claim 1.

12. The suction unit further comprises an electrical conductivity measuring unit for measuring the electrical conductivity of the soil in at least a portion of the area where the suction unit draws in the gas. The gas measuring device according to claim 1.

13. The system comprises multiple suction units, A pump unit is provided in common to multiple suction units and causes the gas to be drawn into the suction units, A plurality of valves are provided for each of the aforementioned suction sections, which are used to select which of the aforementioned suction sections will draw in the gas. The gas measuring device according to claim 1, further comprising:

14. The system comprises multiple suction units, The heating section is provided for each of the suction sections. The gas measuring device according to claim 2.

15. The system comprises multiple suction units, The pH measuring section is provided for each of the suction sections. The gas measuring device according to claim 11.

16. The system comprises multiple suction units, The electrical conductivity measuring unit is provided for each of the aforementioned suction units. The gas measuring device according to claim 12.

17. The facility further comprises an evaluation tank for containing the aforementioned soil. A gas measuring device according to any one of claims 1 to 16.

18. Multiple suction units are provided at different positions in the depth direction of the soil. The gas measuring device according to claim 17.

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