Gas measurement device

Abstract

Provided is a gas measurement device for measuring a target gas present in soil. The gas measurement device comprises: one or more suction units that are buried in the soil and suck in gas; and a concentration measurement unit that measures concentration of the target gas contained in the gas that has been sucked in by the suction units. The gas measurement device also comprises a heating unit that heats at least a portion of a region in the soil from which the suction units suck in the gas, and the suction units may suck in the gas in the soil heated by the heating unit.

Description

Gas Measuring Device

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

[0002] Conventionally, a method for calculating the amount of fixed carbon dioxide has been known (see, for example, Patent Document 1). Problem to be solved

[0003] Easily measure target gases contained in soil. General disclosure

[0004] In order to solve the above problem, one aspect of the present invention provides a gas measurement device for measuring a target gas present in soil. The gas measurement device may include one or more suction units that are buried in the soil and suck in gas. Any of the gas measurement devices may include a concentration measurement unit that measures the concentration of the target gas contained in the gas sucked in by the suction units.

[0005] Any of the gas measurement devices described above may include a heating unit that heats at least a part of an area in the soil from which the suction unit suctions the gas. The suction unit of any of the gas measurement devices described above may suction the gas in the soil heated by the heating unit.

[0006] The heating unit of any of the gas measurement devices described above may include an optical fiber that is buried in the soil and heats the soil by irradiating it with laser light.

[0007] Any of the gas measurement devices described above may include a control unit that calculates the amount of the target gas fixed in the soil based on the change in concentration of the target gas over time.

[0008] The suction unit of any of the gas measurement devices described above may have a head portion formed of a hydrophobic and porous material, and the suction unit of any of the gas measurement devices described above may have a suction tube connected to the head portion and configured to suck in the gas that has permeated the head portion.

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

[0010] The suction unit of any of the gas measurement devices described above may have a head portion formed of a hydrophobic and porous material. The suction unit of any of the gas measurement devices described above may have a suction tube connected to the head portion and configured to suck in the gas that has permeated the head portion. The suction unit of any of the gas measurement devices described above may have a return tube connected to the head portion and configured to return the gas that has permeated the head portion to the soil.

[0011] The head portion of any of the above gas measurement devices may have a suction cavity to which the suction tube is connected. The head portion of any of the above gas measurement devices may have a return cavity to which the return tube is connected. In any of the above gas measurement 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 gas measurement devices may extend toward the return cavity. The return cavity of any of the gas measurement devices may extend toward the suction cavity. In any of the gas measurement devices, an end of the suction cavity and an end of the return cavity may be disposed opposite each other.

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

[0014] Any of the gas measurement devices described above may include a pH measurement unit that measures a pH value of the soil in at least a part of the region into which the suction unit sucks the gas.

[0015] Any of the gas measurement devices described above may include an electrical conductivity measurement unit that measures the electrical conductivity of the soil in at least a part of the region where the suction unit suctions the gas.

[0016] Any of the above gas measurement devices may include a plurality of the suction units. Any of the above gas measurement devices may include a pump unit that is provided in common to the plurality of suction units and causes the suction units to suck the gas. Any of the above gas measurement devices may include a plurality of valve units that are provided corresponding to the respective suction units and select which of the suction units is to suck the gas.

[0017] Any of the above gas measurement devices may include a plurality of the suction units, and the heating unit may be provided for each of the suction units.

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

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

[0020] Any of the gas measurement devices described above may include an evaluation tank that contains the soil.

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

[0022] The above summary of the invention does not list all of the features of the present invention, and subcombinations of these features may also constitute inventions.

[0023] 1 is a diagram illustrating an example of a gas measurement device 100 according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a method for heating soil 14 by a heating unit 170. FIG. 3 is a diagram illustrating another example of the gas measurement device 100. FIG. 4 is a diagram illustrating an example of the configuration of the suction unit 110. FIG. 5 is a diagram illustrating an example of the internal structure of the head unit 112. FIG. 6 is a diagram illustrating an end 115 of the suction cavity 114 on the end face of the head unit 112. FIG. 7 is a diagram illustrating another example of the configuration of the suction unit 110. FIG. 8 is a diagram illustrating an example of the internal structure of the head unit 112. FIG. 9 is a diagram illustrating an end 115 of the suction cavity 114 on the surface of the head unit 112. FIG. 10 is a diagram illustrating another example of the configuration of the suction unit 110. FIG. 11 is a diagram illustrating an example of the internal structure of the head unit 112. FIG. 12 is a diagram illustrating another example of the configuration of the suction unit 110. FIG. 13 is a diagram illustrating an example of the internal structure of the head unit 112. FIG. 14 is a diagram illustrating another example of the internal structure of the head unit 112. FIG. 15 is a diagram illustrating another example of the suction cavity 114 and the return cavity 122. FIG. 16 is a diagram illustrating another example of the suction cavity 114 and the return cavity 122. FIG. 17 is a diagram illustrating another example of the configuration of the head unit 112. 10A and 10B are diagrams illustrating an example of the operation of the control unit 150. FIG. 10C are diagrams illustrating another example of the operation of the control unit 150.

[0024] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention. Furthermore, not all of the 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 designated by the same reference numerals to avoid redundant description, and elements not directly related to the present invention are not shown. Furthermore, in one drawing, elements having the same function and configuration may be designated by a representative reference numeral, and the reference numerals for other elements may be omitted.

[0025] In this specification, when terms such as "same" or "equal" are used, it may include cases where there is an error due to manufacturing variations, etc. The error is, for example, within 10%. Furthermore, in this specification, when terms such as "upper" or "lower" are used, they may refer to the upper and lower sides in the direction of gravity.

[0026] FIG. 1 is a diagram showing an example of a gas measurement device 100 according to an embodiment of the present invention. The gas measurement device 100 measures a target gas present in soil 14. The gas measurement device 100 may measure the concentration or amount of the target gas present in soil 14. The gas measurement device 100 may measure the concentration or amount of the target gas present as a gas in soil 14, may measure the concentration or amount of the target gas including components fixed in soil 14, or may measure the concentration or amount of the target gas including components emitted by microorganisms present in soil 14. Fixation of the target gas refers to preventing the target gas from being released into the air by some method. For example, the target gas is fixed by adsorbing or adhering to other substances contained in soil 14.

[0027] The soil 14 to be measured may be present as part of land, or may be contained in some kind of container. The container may or may not seal the soil 14. The soil 14 may be in a state where plants are planted, or may not be planted. The soil 14 may be in a state before plants are planted, a state where plants are planted and growing, a state where plants have withered, or a state where plants have been removed. The soil 14 may contain gravel in addition to soil. In FIG. 1, gravel contained in the soil 14 is represented by a circle or an oval.

[0028] The target gases are, for example, but not limited to, greenhouse gases. ２ and N ２ The target gas may be O, both O and O, or another gas. By measuring the target gas present in the soil 14, the soil 14 can be evaluated. Furthermore, when a plant is planted in the soil 14, the effect of the plant on the soil 14 can be evaluated by measuring the target gas in the soil 14 at multiple different times.

[0029] Gas measurement device 100 includes one or more suction units 110 and concentration measurement units 130. Gas measurement device 100 may further include at least one of one or more valve units 142, 144, pump units 140, control units 150, and heating and measurement units 160.

[0030] The suction unit 110 is buried in the soil 14 and sucks gas. The suction unit 110 may suck gas from the soil 14 through a filter or the like that is impermeable to liquids and solids but permeable to gas. The filter may be a membrane or the like formed primarily from a hydrophobic porous material. The porous material is, for example, a fluorine-based resin such as polytetrafluoroethylene (PTFE). The porous material has pores that allow gas molecules to pass through. The diameter of the pores is generally, but not limited to, 5 μm or more and 20 μm or less. The average diameter of the pores in the suction unit 110 may be 5 μm or more and 20 μm or less.

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

[0032] The pump unit 140 causes each suction unit 110 to suck gas from the soil 14. The pump unit 140 is connected to the suction unit 110 by a tube or the like. The pump unit 140 sucks gas from the soil 14 through the tube or the like, causing the suction unit 110 to suck gas from the soil 14.

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

[0034] The concentration measurement unit 130 measures the concentration of the target gas contained in the gas sucked by the suction unit 110. Unless otherwise specified, the gas concentration in this specification is a volume concentration. In this example, the concentration measurement unit 130 is provided between the suction unit 110 and the pump unit 140, and the gas sucked by the pump unit 140 is supplied. The concentration measurement unit 130 may measure the concentration of the target gas contained in the gas using laser absorption spectroscopy (LAS). In laser absorption spectroscopy, the concentration of the target gas is measured by comparing the incident intensity of a wavelength component corresponding to the target gas in a laser irradiated onto the gas with the emitted intensity of the corresponding wavelength component in the laser that has passed through the gas. The concentration of the target gas contained in the gas can be calculated from the attenuation of the emitted intensity relative to the incident intensity and the optical path length of the laser passing through the gas to be measured. The concentration measurement unit 130 may use a quantum cascade laser (QCL) as a light source for laser absorption spectroscopy. A quantum cascade laser can sweep its oscillation wavelength by controlling the current. The wavelength sweep range of the quantum cascade laser includes CO ２ and N ２ Since the wavelengths to which O is sensitive are included, it is suitable for measuring these target gases.

[0035] The valve unit 144 switches whether or not to introduce a reference gas into the concentration measurement unit 130. The reference gas may be a gas having a known concentration of the target gas, or may be another gas. The reference gas may be used to calibrate the concentration measurement unit 130. 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. The valve units 142 and 144 are, for example, but are not limited to, solenoid valves.

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

[0037] The heating and measuring unit 160 includes at least one of a heating unit 170, a pH measuring unit 180, and an 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 region of the soil 14 from which the suction unit 110 suctions the gas. The suction unit 110 may suction the gas in the soil heated by the heating unit 170. By heating the soil 14, the target gas fixed in the soil 14 can be converted into a gas that can be suctioned. This allows the gas measuring device 100 to measure the concentration or amount of the target gas in the soil 14, including the components 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 increases. The temperature measuring unit described above may measure the temperature of the surface 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 increase reaches a set temperature. The increase in temperature of the surface of the suction unit 110 caused by the heating unit 170 may be 5°C or more, or may be 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 of the surface of the suction unit 110 caused by the heating unit 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 over a set measurement period. The heating unit 170 may heat the soil 14 so that the temperature measured by the temperature measurement unit during the measurement period is maintained at a predetermined set value. The concentration measurement unit 130 may measure the concentration of the target gas at multiple times during the period in which the heating unit 170 is heating the soil 14. The increase in the amount of target gas that is gasified over time varies depending on 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 manner in which the concentration of the target gas changes. For example, it can be estimated that the faster the change in the concentration of the target gas, the greater the total amount of target gas fixed in the soil 14.

[0040] If the soil 14 contains microorganisms that generate a target gas, the amount of target gas generated by the microorganisms varies depending on the temperature of the soil 14. For example, the higher the temperature of the soil 14, the more activated the microorganisms may be, resulting in a greater amount of target gas generated. The concentration measurement unit 130 may measure the concentration of the target gas contained in the gas sucked 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 concentration of the target gas for each temperature. For example, the greater the increase in the concentration of the target gas with an increase in temperature, the greater the amount of microorganisms contained in the soil 14 can be estimated to be.

[0041] The pH measurement unit 180 measures the pH value of the soil 14 in at least a portion of the region where the suction unit 110 suctions the gas. The pH measurement unit 180 may measure the pH value of the soil 14 in the region that contacts 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 gasifies, the activity of microorganisms, or their reactivity 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 more accurately.

[0042] The EC measuring unit 190 measures the electrical conductivity (EC) of the soil 14 in at least a portion of the region where the suction unit 110 suctions the gas. The EC measuring unit 190 may measure the electrical conductivity of the soil 14 in the region that contacts 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 gasifies, the activity of microorganisms, or their reactivity 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 more accurately.

[0043] 1 , when a plurality of suction units 110 are provided, the heating unit 170 may be provided for each suction unit 110. The pH measurement unit 180 may also be provided for each suction unit 110. The EC measurement unit 190 may also be provided for each suction unit 110. The other measurement units included in the heating / measurement unit 160 may also be provided for each suction unit 110.

[0044] FIG. 2 is a diagram illustrating an example of a method for heating the soil 14 using the heating unit 170. The heating unit 170 in this example has an optical fiber 172. The optical fiber 172 is buried in the soil 14 and heats the soil 14 by irradiating it with laser light. The optical fiber 172 locally heats at least a portion of the region 111 in the soil 14 from which the suction unit 110 sucks gas by irradiating the laser light to the region 111. By using laser light, the region to be heated can be precisely controlled. Furthermore, because laser light allows for localized heating, it is possible to reduce the influence on the concentration measurement of the target gas by other suction units 110.

[0045] The range of region 111 may vary depending on the size of suction unit 110, the suction pressure of the gas by pump unit 140, etc. Region 111 is the region where the present gas is sucked by suction unit 110, but a range whose distance from suction unit 110 is within five times the maximum width W of the portion of suction unit 110 made of porous material may also be considered to be region 111. Heating unit 170 may locally heat at least a portion of this range in the vicinity of suction unit 110.

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

[0047] Fig. 3 is a diagram showing another example of gas measurement device 100. Gas measurement device 100 of this example differs from the example described in Figs. 1 and 2 in that it further includes evaluation tank 10 that contains soil 14. The other structure is similar to either example described in Figs. 1 and 2.

[0048] The evaluation tank 10 of this example contains soil 14, a gas sensor 16, a plant 18, a water supply pipe 20, and a drainage pipe 22. The plant 18 has roots in the soil 14 and grows stems and leaves above the soil 14. The plant 18 produces CO2 through photosynthesis. ２ is fixed in the body, and CO ２ In one example, plants 18 excrete CO in the form of cellulose.２ The plants 18 include various plants such as vegetables, shrubs, and trees. The plants 18 grow by photosynthesis and respiration inside the evaluation tank 10. That is, the plants are grown in soil in the evaluation tank 10 of 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. The gas sensor 16 in this example measures CO ２ Measure the concentration of.

[0050] The water supply pipe 20 is provided 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 drains excess water (hereinafter, sometimes referred to as drainage) from inside the evaluation tank 10. A liquid sensor 24 that measures 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 that can control the wavelength and intensity of light. The light source 26 can, for example, create an environment that simulates alternating day and night.

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

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

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

[0054] The evaluation tank 10 may provide a closed system environment. The closed system may be a system in which no substances other than the target gas are exchanged between the system and the outside, or a system in which no substances other than the target gas and water supply / drainage are exchanged between the system and the outside.

[0055] FIG. 4 is a diagram showing an example of the configuration of the suction unit 110. The suction unit 110 of this example has a head unit 112 and a suction tube 113. The head unit 112 is formed of a hydrophobic and porous material. As described above, one example of the porous material is PTFE. The head unit 112 may be entirely buried in the soil 14. Although the head unit 112 of this example has a cylindrical shape, the shape of the head unit 112 is not limited thereto. Gas in the soil 14 permeates 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 sucks gas that has passed through the head portion 112. In this example, the suction tube 113 is connected to one end surface of the cylindrical head portion 112. The suction tube 113 may 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] 5 is a diagram showing an example of the internal structure of the head unit 112. The head unit 112 of this example has a suction cavity 114 connected to a suction tube 113 inside. 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 opposite to the end 115, and a side surface 117 between the end 115 and the end 116. The suction tube 113 is connected to the end 115.

[0060] The suction cavity 114 in this example is provided to extend in the longitudinal direction of the head portion 112. The suction cavity 114 does not pass through the head portion 112, and an end portion 116 is provided inside the head portion 112.

[0061] The pump unit 140 sucks gas through the suction tube 113, causing the gas in 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 measurement unit 130 through the suction tube 113.

[0062] The suction cavity 114 may be provided 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 extension direction of the suction cavity 114 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 surface 117 and the surface of the head portion 112. This allows gas around the head portion 112 to be evenly sucked in. If the distance r between the side surface 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. Average values ​​may also be used for other distances, lengths, widths, etc. described in this specification.

[0063] 6 is a view showing an end 115 of the suction cavity 114 on the end face of the head portion 112. The end 115 may be provided at the center of the end face.

[0064] Fig. 7 is a diagram showing another example of the configuration of the suction unit 110. The suction unit 110 of this example differs from the example shown in Fig. 4 in the shape of the head unit 112. The other structures are the same as any of the examples described with reference to Figs. 4 to 6.

[0065] The head portion 112 in this example has a spherical shape. The suction tube 113 in this example is connected to any position on the surface of the spherical head portion 112. The suction tube 113 may 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] 8 is a diagram showing an example of the internal structure of the head portion 112. The head portion 112 of this example is also provided with a suction cavity 114 connected to a suction tube 113, similar to the example of FIG.

[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 area where 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 an end portion 116 is provided 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 the gas around the head portion 112 to be evenly sucked in.

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

[0070] 10 is a diagram showing another example of the configuration of the suction unit 110. The suction unit 110 of this example returns the gas measured by the concentration measurement unit 130 to the soil 14. The measured gas may be supplied to the suction unit 110 by the pump unit 140. When 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 another example, 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 of this example further includes a return tube 118 compared to the examples described with reference to Figures 4 to 9. Other structures are similar to any of the examples described with reference to Figures 4 to 9. The return tube 118 is connected to the head portion 112 and passes through the head portion 112 to return the gas to the soil 14. The return tube 118 of this example is connected to the end face of the cylindrical head portion 112 on the opposite side to the suction tube 113. The return tube 118 may be inserted inside the head portion 112.

[0072] 11 is a diagram showing an example of the internal structure of the head portion 112. In addition to the suction cavity 114, a return cavity 122 is provided inside the head portion 112 of this example. 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 opposite to the end 119, and a side surface 121 between the end 119 and the end 120. The return tube 118 is connected to the end 119.

[0074] In this example, the return cavity 122 extends 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. That is, in this example, the suction cavity 114 and the return cavity 122 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 regions of the head portion 112.

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

[0076] The pump unit 140 may simultaneously suck gas through the suction tube 113 and return gas through the return tube 118. By sucking gas through the suction tube 113, the gas permeates from the surface of the head unit 112 to the suction cavity 114. By returning gas through the return tube 118, the gas permeates from the return cavity 122 to the surface of the head unit 112. Furthermore, a portion of the gas returned through the return tube 118 permeates from the return cavity 122 to the suction cavity 114. In other words, the pump unit 140 may circulate a portion of the gas through the suction unit 110.

[0077] According to this example, the gas to be measured can be circulated while partially exchanging the gas in the soil 14 with the circulating gas. This makes it possible to measure temporal fluctuations in the concentration of the target gas in the soil 14 in real time while preventing a significant loss of the target gas in the soil 14 due to concentration measurement.

[0078] The distance between end 116 and end 120 in the extension direction is defined as L. The mixing ratio of the gas circulating from return cavity 122 to suction cavity 114 to the gas sucked from soil 14 can be adjusted by distance L and distance r. Increasing distance L decreases the ratio of circulating gas, while decreasing distance L increases the ratio of circulating gas. Increasing distance r decreases the ratio of gas sucked from soil 14, while decreasing distance r increases the ratio of gas sucked from soil 14. Distances L and r may be determined according to the mixing ratio to be achieved. Distance L may be greater than, smaller than, or the same as distance r.

[0079] Fig. 12 is a diagram showing another example of the configuration of the suction unit 110. The suction unit 110 of this example differs from the example shown in Fig. 10 in that the shape of the head unit 112 is spherical. The other structures are the same as either of the examples described in Fig. 10 and Fig. 11.

[0080] Fig. 13 is a diagram showing an example of the internal structure of the head portion 112. The head portion 112 of this example is also provided with a return cavity 122 connected to the return tube 118, similar to the example of Fig. 11 .

[0081] Figure 14 is a diagram showing 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 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 both the suction cavity 114 and 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 is a diagram showing 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 any of the examples described in Figures 10 to 13. The end 116 of the suction cavity 114 in this example has a tapered shape, the diameter of which decreases as it approaches the return cavity 122. Similarly, the end 120 of the return cavity 122 in this example has a tapered shape, the diameter of which decreases 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 inclination of the tapered shape.

[0083] Figure 16 is a diagram showing 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 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, as in the example of Figure 15, and their tips are connected by a connecting cavity 123. This structure also makes it possible to adjust the amount of gas circulating from the return cavity 122 to the suction cavity 114.

[0084] Fig. 17 is a diagram showing another example of the structure of the head portion 112. The head portion 112 of this example 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 any of the examples described with reference to Figs. 10 to 17.

[0085] The gap portion 125 is a region in the head portion 112 between the suction cavity 114 and the return cavity 122. A 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 a region in the head portion 112 other than the gap portion 125.

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

[0087] 18 is a diagram illustrating an example of the operation of the control unit 150. In this example, the concentration measurement 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 the target gas fixed in the soil 14 based on the change in the concentration of the target gas over time.

[0088] As described above, the target gas fixed in the soil 14 is gasified by heating the soil 14. The more target gas fixed in the soil 14, the more target gas is gasified by heating. Therefore, the amount of target gas fixed in the soil 14 can be estimated from the change in the concentration of the target gas over time (slope Δ). The change in the concentration of the target gas over time (slope Δ) may be a value obtained a predetermined time after 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 experimentally obtained in advance.

[0089] As described above, when the soil 14 is heated, the target gas fixed in the soil 14 is gasified, and the amount of target gas emitted by the 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. On the other hand, the increase in the gas emitted by the microorganisms due to heating is observed relatively late after the start of heating.

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

[0091] FIG. 19 is a diagram illustrating an example of the operation of the control unit 150. In this example, the concentration measurement unit 130 detects the concentration of the target gas by repeatedly heating the soil 14 with the heating unit 170 and not heating it. The control unit 150 may estimate the amount of microorganisms present in the soil 14 based on the increase ΔD in the concentration of the target gas at the time when the second period T2 has elapsed since the start of heating. The increase ΔD may be the increase in the concentration of the target gas relative to the concentration at the start of heating. As described above, the second period T2 may be longer than the first period T1. The second period T2 is preferably long enough so that the measured value of the concentration of the target gas converges to a constant value. The control unit 150 may acquire the increase ΔD multiple times by repeatedly heating the soil 14 and not heating it 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 the soil 14 is heated to a predetermined temperature and the amount of microorganisms may 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 and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0093] 10: Evaluation tank, 14: Soil, 16: Gas sensor, 18: Plant, 20: Water supply pipe, 22: Drain pipe, 24: Liquid sensor, 26: Light source, 100: Gas measurement device, 110: Suction section, 111: Area, 112: Head section, 113: Suction tube, 114: Suction cavity, 115: End, 116: End, 117: Side, 118: Return tube, 119: End, 120: End, 121: Side, 122: Return cavity, 123: Connection cavity, 124: Main section, 125: Gap section, 130: Concentration measurement section, 140: Pump section, 142, 144: Valve section, 150: Control section, 160: Heating / measurement section, 170: Heating section, 172: Optical fiber, 180: pH measurement section, 190: EC measurement section

Claims

1. A gas measurement device for measuring a target gas present in soil, comprising: one or more suction units that are buried in the soil and suck in gas; and a concentration measurement unit that measures the concentration of the target gas contained in the gas sucked in by the suction units.

2. The gas measuring device according to claim 1, further comprising a heating unit that heats at least a portion of the area in the soil where the suction unit suctions the gas, and the suction unit suctions the gas in the soil heated by the heating unit.

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

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

5. A gas measuring device according to claim 1, wherein the suction section has a head section formed of a hydrophobic and porous material, and a suction tube connected to the head section for suctioning the gas that has permeated the head section.

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

7. A gas measuring device as described in claim 6, wherein the suction section has: a head section formed of a hydrophobic and porous material; a suction tube connected to the head section for sucking in the gas that has passed through the head section; and a return tube connected to the head section for passing the gas through the head section and returning it to the soil.

8. A gas measuring device as described in claim 7, wherein the head portion includes a suction cavity to which the suction tube is connected and a return cavity to which the return tube is connected, and a hydrophobic and porous material is provided between the suction cavity and the return cavity.

9. A gas measuring device as described in claim 8, wherein the suction cavity extends toward the return cavity, the return cavity extends toward the suction cavity, and an end of the suction cavity and an end of the return cavity are arranged opposite each other.

10. The gas measurement device of claim 8, wherein the material between the suction cavity and the return cavity is different from the material in other areas of the head portion.

11. The gas measuring device according to claim 1, further comprising a pH measuring unit for measuring the pH value of the soil in at least a part of the area into which the suction unit sucks the gas.

12. The gas measuring device according to claim 1, further comprising an electrical conductivity measuring unit that measures the electrical conductivity of the soil in at least a portion of the region where the suction unit sucks the gas.

13. A gas measuring device according to claim 1, further comprising: a pump unit provided in common to the plurality of suction units and causing the suction units to suck the gas; and a plurality of valve units provided for each of the suction units and selecting which of the suction units will suck the gas.

14. The gas measuring device according to claim 2, wherein a plurality of the suction sections are provided, and the heating section is provided for each of the suction sections.

15. The gas measuring device according to claim 11, comprising a plurality of suction sections, each of which is provided with a pH measuring section.

16. The gas measuring device according to claim 12, comprising a plurality of suction sections, and wherein the electrical conductivity measuring section is provided for each of the suction sections.

17. The gas measurement device according to any one of claims 1 to 16, further comprising an evaluation tank for containing the soil.

18. The gas measuring device according to claim 17, wherein a plurality of the suction sections are provided at different positions in the depth direction of the soil.

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