Method for measuring nitrogen component amount in soil

Abstract

To provide a method for easily measuring a nitrogen component amount in soil on the spot.SOLUTION: This method for easily measuring the nitrogen component amount in soil uses a gas sensor 100. The gas sensor 100 includes a gas detection unit 110 that introduces a gas to be measured and detects a nitrogen-containing gas contained in the gas to be measured as a measurement target gas, and a heater that heats the gas detection unit 110. The measuring method comprises: an insertion step of inserting the gas detection unit 110 into the desired position of the soil Soil; a decomposition unit of heating the soil Soil contacted with the outer surface of the gas detection unit 110 by the gas detection unit 110 heated by the heater, and thermally decomposing the nitrogen component contained in the soil Soil to generate a nitrogen-containing gas; a detection step of detecting the amount of the generated nitrogen-containing gas by the gas sensor 100; and a calculation step of calculating the nitrogen component amount in the soil Soil on the basis of the detected amount of the nitrogen-containing gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for measuring the amount of nitrogen components in soil. In particular, it relates to a method for measuring the amount of nitrogen components in soil using a gas sensor.

Background Art

[0002] Nitrous oxide N 2 O is a kind of greenhouse gas, and its global warming potential is about 300 times that of typical greenhouse gas carbon dioxide CO 2 (Non-Patent Document 1). Nitrous oxide N 2 O is a gas species whose emissions should be reduced as a measure against global warming, and a reduction target for emissions has also been set.

[0003] About 75% of the emissions of nitrous oxide N 2 O are due to emissions from the agricultural sector (Non-Patent Document 1). Specifically, among the nitrogen fertilizers spread on the soil, the surplus nitrogen fertilizers that are not absorbed by crops such as vegetables and remain in the soil are decomposed by bacteria in the soil, and nitrous oxide N 2 O is generated and emitted into the atmosphere. Therefore, in order to suppress the generation of nitrous oxide N 2 O, it is advisable to maintain the amount of nitrogen components in the soil at an amount suitable for the growth of crops and to ensure that there is no surplus nitrogen fertilizer. For this purpose, it is necessary to measure the amount of nitrogen components in the soil. The appropriate amount of nitrogen components in the soil may vary depending on the type of soil and the crops planted in that soil.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Some methods for measuring the amount of nitrogen components in soil are known. For example, a commonly used soil diagnosis method is to sample soil from the soil for which the nitrogen component amount is to be measured and perform analysis in a laboratory. Although detailed analysis is possible, there are problems that the procedure is complicated and it takes time to obtain results.

[0007] In addition, a simple diagnosis method is also known in which the pH and EC (electric conductivity) in the soil are measured, and the excess or deficiency of nitrogen components in the soil is estimated from these values. However, since pH and EC are also affected by components other than nitrogen components, there is a problem that the measurement accuracy as a measurement of nitrogen components is low.

[0008] In addition, Non-Patent Document 1 shows an idea of installing a plurality of N 2 O sensors in the soil (such as a field) to grasp the spatial distribution of N 2 O emissions into the atmosphere (Figure 8). However, since N 2 O emitted from the soil into the atmosphere diffuses in space and is diluted in the atmosphere, the N 2 O sensor needs to measure N 2 O at an extremely low concentration, and it is considered that the measurement accuracy is low.

[0009] In view of the above problems, an object of the present invention is to provide a method for simply measuring the amount of nitrogen components in soil on-site.

Means for Solving the Problems

[0010] As a result of intensive studies, the present inventors have found a method for measuring the amount of nitrogen components in soil using a gas sensor. The present invention includes the following inventions.

[0011] (1) A method for measuring the amount of nitrogen components in soil using a gas sensor, wherein the gas sensor includes a gas detection unit that introduces a gas to be measured and detects a nitrogen-containing gas in the gas to be measured as a gas to be measured; a heater that heats the gas detection unit; and the measurement method includes an insertion step of inserting the gas detection unit of the gas sensor into a desired position of the soil to be measured; a decomposition step of heating the soil in contact with the outer surface of the gas detection unit by the gas detection unit heated by the heater, and thermally decomposing the nitrogen components contained in the soil to generate a nitrogen-containing gas; a detection step of detecting the amount of the generated nitrogen-containing gas by the gas sensor; a calculation step of calculating the amount of nitrogen components in the soil based on the amount of the detected nitrogen-containing gas. A method for measuring the amount of nitrogen components in soil, including

[0012] (2) The gas sensor includes a long plate-shaped sensor element including an oxygen ion-conductive solid electrolyte, the gas detection unit includes a portion in contact with the gas to be measured on one end side in the longitudinal direction of the sensor element; a gas flow space to be measured formed on the one end side in the longitudinal direction of the sensor element; a measurement pump cell including an in-space measurement electrode disposed in the gas flow space to be measured and a space-outside measurement electrode disposed at a position different from the gas flow space to be measured and corresponding to the in-space measurement electrode; In the detection step, the gas sensor detects the amount of the nitrogen-containing gas in the gas to be measured based on the current flowing through the measurement pump cell. The measurement method according to (1) above.

[0013] (3) In the detection step, the gas sensor detects the amount of nitrogen-containing gas in the gas to be measured based on the current integration value obtained by integrating the current flowing through the measurement pump cell for a predetermined time, according to the measurement method described in (2) above.

[0014] (4) The outer surface of the gas detection part of the gas sensor is maintained at a temperature of 180 °C or higher, according to the measurement method described in any one of (1) to (3) above.

[0015] (5) The outer surface of the gas detection part of the gas sensor is maintained at a temperature of 500 °C or lower, according to the measurement method described in any one of (1) to (4) above.

[0016] (6) The gas detection part of the gas sensor includes a protective cover that protects one end in the longitudinal direction of the sensor element. The outer surface of the protective cover is the outer surface of the gas detection part of the gas sensor, according to the measurement method described in any one of (2) to (5) above.

[0017] (7) The outer surface of the part in contact with the gas to be measured on the side of one end in the longitudinal direction of the sensor element is the outer surface of the gas detection part of the gas sensor, according to the measurement method described in any one of (2) to (5) above.

[0018] (8) In the calculation step, the amount of nitrogen component in the soil is calculated using the amount of nitrogen-containing gas detected by the gas sensor, the correlation between the amount of nitrogen-containing gas detected by the gas sensor obtained in advance, and the amount of nitrogen component in the soil, according to the measurement method described in any one of (1) to (7) above.

[0019] (9) The nitrogen-containing gas as the gas to be measured by the gas sensor is at least one gas selected from the group consisting of nitric oxide NO, nitrogen dioxide NO 2 , and ammonia NH 3 , according to the measurement method described in any one of (1) to (8) above.

[0020] (10-1) A method for determining whether the amount of nitrogen components in soil is excessive using a gas sensor, comprising: The gas sensor includes: A gas detection unit that introduces a gas to be measured and detects a nitrogen-containing gas in the gas to be measured as a gas to be measured; A heater that heats the gas detection unit; And includes: The determination method includes: An insertion step of inserting the gas detection unit of the gas sensor into a desired position of the soil to be measured; A decomposition step of heating the soil in contact with the outer surface of the gas detection unit by the gas detection unit heated by the heater, and thermally decomposing the nitrogen components contained in the soil to generate a nitrogen-containing gas; A detection step of detecting the amount of the generated nitrogen-containing gas by the gas sensor; A determination step of determining that the amount of nitrogen components in the soil is excessive when the detected amount of the nitrogen-containing gas is greater than a predetermined value. A method for determining the amount of nitrogen components in soil.

[0021] (10-2) The gas sensor includes a long plate-shaped sensor element including an oxygen ion-conductive solid electrolyte, The gas detection unit includes: A portion in contact with the gas to be measured on one end side in the longitudinal direction of the sensor element; A gas flow space for the gas to be measured formed on one end side in the longitudinal direction of the sensor element; A measurement pump cell including an in-vacancy measurement electrode disposed in the gas flow space for the gas to be measured, and an out-of-vacancy measurement electrode disposed at a position different from the gas flow space for the gas to be measured and corresponding to the in-vacancy measurement electrode. In the detection step, the gas sensor detects the amount of the nitrogen-containing gas in the gas to be measured based on the current flowing through the measurement pump cell. The determination method according to (10-1) above.

[0022] (10-3) In the detection step, the gas sensor detects the amount of the nitrogen-containing gas in the gas to be measured based on the current integration value obtained by integrating the current flowing through the measurement pump cell for a predetermined time, according to the determination method described in (10-2) above.

[0023] (10-4) The outer surface of the gas detection part of the gas sensor is maintained at a temperature of 180 °C or higher, according to the determination method described in any one of (10-1) to (10-3) above.

[0024] (10-5) The outer surface of the gas detection part of the gas sensor is maintained at a temperature of 500 °C or lower, according to the determination method described in any one of (10-1) to (10-4) above.

[0025] (10-6) The gas detection part of the gas sensor includes a protective cover that protects one end in the longitudinal direction of the sensor element. The outer surface of the protective cover is the outer surface of the gas detection part of the gas sensor, according to the determination method described in any one of (10-2) to (10-5) above.

[0026] (10-7) The outer surface of the part in contact with the gas to be measured on the side of one end in the longitudinal direction of the sensor element is the outer surface of the gas detection part of the gas sensor, according to the determination method described in any one of (10-2) to (10-5) above.

[0027] (10-8) In the determination step, the predetermined value is preset from the correlation between the amount of nitrogen-containing gas detected by the gas sensor and the amount of nitrogen component in the soil, according to the measurement method described in any one of (10-1) to (10-7) above.

[0028] (10-9) The nitrogen-containing gas as the gas to be measured by the gas sensor is at least one gas selected from the group consisting of nitric oxide NO, nitrogen dioxide NO 2 , and ammonia NH 3 and is, according to the measurement method described in any one of (10-1) to (10-8) above.

[0029] (11-1) A gas sensor used for measuring the amount of nitrogen components in soil, The gas sensor includes a gas detection unit that introduces a gas to be measured and detects a nitrogen-containing gas in the gas to be measured as a gas to be measured, a heater that heats the gas detection unit, and a calculation unit that calculates the amount of nitrogen components in the soil, and the gas detection unit is inserted into a desired position of the soil to be measured, the gas detection unit heated by the heater heats the soil in contact with the outer surface of the gas detection unit, thermally decomposes the nitrogen components contained in the soil to generate a nitrogen-containing gas, the gas detection unit detects the amount of the generated nitrogen-containing gas, and the calculation unit calculates the amount of nitrogen components in the soil based on the amount of the detected nitrogen-containing gas. A gas sensor.

[0030] (11-2) The gas sensor includes a long plate-shaped sensor element including an oxygen ion-conductive solid electrolyte, the gas detection unit includes a portion in contact with the gas to be measured on one end side in the longitudinal direction of the sensor element, a gas to be measured flow cavity formed on the one end side in the longitudinal direction of the sensor element, a measurement pump cell disposed in the gas to be measured flow cavity and including an in-cavity measurement electrode and an out-of-cavity measurement electrode disposed at a position different from the gas to be measured flow cavity and corresponding to the in-cavity measurement electrode, and detects the amount of the nitrogen-containing gas in the gas to be measured based on the current flowing through the measurement pump cell. The gas sensor according to (11-1) above.

[0031] (11-3) Detects the amount of the nitrogen-containing gas in the gas to be measured based on the current integration value obtained by integrating the current flowing through the measurement pump cell for a predetermined time. The gas sensor according to (11-2) above.

[0032] (11-4) The outer surface of the gas detection unit is maintained at a temperature of 180°C or higher, and the gas sensor according to any one of (11-1) to (11-3) above.

[0033] (11-5) The outer surface of the gas detection unit is maintained at a temperature of 500°C or lower, and the gas sensor according to any one of (11-1) to (11-4) above.

[0034] (11-6) The gas detection unit includes a protective cover that protects one end in the longitudinal direction of the sensor element, The outer surface of the protective cover is the outer surface of the gas detection unit, and the gas sensor according to any one of (11-2) to (11-5) above.

[0035] (11-7) The outer surface of the portion in contact with the gas to be measured on the side of one end in the longitudinal direction of the sensor element is the outer surface of the gas detection unit, and the gas sensor according to any one of (11-2) to (11-5) above.

[0036] (11-8) The calculation unit stores in advance the correlation between the amount of nitrogen-containing gas detected by the gas detection unit and the amount of nitrogen component in the soil, and uses the amount of nitrogen-containing gas detected by the gas detection unit and the correlation obtained in advance to calculate the amount of nitrogen component in the soil, and the measurement method according to any one of (11-1) to (11-7) above.

[0037] (11-9) The nitrogen-containing gas as the gas to be measured by the gas sensor is at least one gas selected from the group consisting of nitric oxide NO, nitrogen dioxide NO 2 , and ammonia NH 3 and the measurement method according to any one of (11-1) to (11-8) above.

Advantages of the Invention

[0038] By using the measurement method of the present invention, the amount of nitrogen components in soil can be easily measured on-site. Also, by using the determination method of the present invention, it is possible to easily determine on-site whether the amount of nitrogen components in soil is excessive. By using these measurements and determinations, it is possible to prevent the amount of nitrogen components in soil from becoming excessive, and 2 the N

[0039] Moreover, according to the present invention, it is possible to provide a gas sensor capable of measuring the amount of nitrogen components in soil. By this gas sensor, the amount of nitrogen components in soil can be easily measured on-site.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0041] [Nitrogen components in soil] In the present invention, nitrogen components contained in soil are measured. Soil refers to the outermost layer of the earth's crust, which is a mixture containing inorganic components such as minerals and organic components generated by the decomposition of animals and plants. It is also simply called soil. Soil contains various components, and nitrogen components are one of them. The nitrogen components include nitrogen compounds in various forms (organic nitrogen and inorganic nitrogen). The nitrogen components are also referred to as nitrogen-containing components hereinafter.

[0042] Nitrogen is one of the nutrients essential for plant growth and is one of the so-called three major elements (nitrogen, phosphoric acid, and potassium). Therefore, when growing crops, fertilizers are spread on the soil to supply sufficient nitrogen components for crop growth.

[0043] The nitrogen components in soil include nitrogen-containing components originally present in the soil (mainly organic nitrogen) and nitrogen-containing components given as fertilizers. Fertilizers are roughly classified into chemical fertilizers and organic fertilizers. Chemical fertilizers include single fertilizers and compound fertilizers. Single nitrogen fertilizers (nitrogenous fertilizers) include ammonium sulfate (ammonium sulfide), ammonium chloride, ammonium nitrate, urea, calcium cyanamide, slow-release fertilizers, etc. Slow-release fertilizers are, for example, isobutylaldehyde-treated urea, acetaldehyde-treated urea, formaldehyde-treated urea, coated nitrogen samples, etc. Compound fertilizers include highly compounded fertilizers, ordinary compounded fertilizers, formulated fertilizers, etc. Organic fertilizers include animal fertilizers such as fish meal and bone meal, plant fertilizers such as oil cake, and organic waste fertilizers such as sludge fertilizers. One or more fertilizers are appropriately selected and used according to the type of crops and the original state of the soil, etc.

[0044] The nitrogen components in soil are absorbed by the crops planted in the soil and contribute to the growth of the crops. However, for example, when the amount of fertilizer is excessive, some of the nitrogen components remain in the soil without being absorbed by the crops. When the nitrogen components remaining in the soil are decomposed by microorganisms in the soil, nitrous oxide N 2 O is generated and discharged into the atmosphere. Nitrous oxide N2 O is a greenhouse gas with a global warming potential about 300 times that of carbon dioxide CO 2 Therefore, it is required to suppress the emission of nitrous oxide N 2 O.

[0045] By maintaining the amount of nitrogen components in the soil of farmland, etc. at the amount necessary for the growth of crops and ensuring that excessive nitrogen components do not exist as much as possible, the generation of nitrous oxide N 2 O in the soil can be suppressed, and it is considered possible to reduce the emission amount of nitrous oxide N 2 O from the soil. The amount of nitrogen components in the soil can be adjusted, for example, by the amount of fertilizer. In order to adjust the amount of nitrogen components, it is necessary to measure / estimate and grasp the amount of nitrogen components in the soil. Also, the required amount of nitrogen components can vary depending on the type and growth stage of the crops. Therefore, it is preferable that the amount of nitrogen components can be easily measured on-site as needed in each farmland, etc.

[0046] The soil to be measured in the present invention is not particularly limited. It includes all soils such as farmland like fields and orchards, as well as pastures, forests, grasslands, swamps, sandy lands, etc. It also includes developed lands such as residential areas. For example, as part of environmental surveys, measuring the amount of nitrogen components in the soil, etc. can be considered.

[0047] [Measurement of Nitrogen Components in Soil] The measurement method in the present invention is a method for measuring the amount of nitrogen components in soil using a gas sensor.

[0048] In the present invention, the gas sensor includes a gas detection unit that introduces the gas to be measured and detects the nitrogen-containing gas in the gas to be measured as the gas to be measured, and a heater that heats the gas detection unit.

[0049] In the present invention, the measurement method of the amount of nitrogen components in soil includes an insertion step of inserting the gas detection unit of the gas sensor into a desired position of the soil to be measured. The decomposition step of heating the soil in contact with the outer surface of the gas detection unit by the heater, and thermally decomposing the nitrogen component contained in the soil to generate nitrogen-containing gas; The detection step of detecting the amount of the generated nitrogen-containing gas by the gas sensor; And a calculation step of calculating the amount of the nitrogen component in the soil based on the amount of the detected nitrogen-containing gas. Thus, the measurement method of the present invention is a measurement method of detecting the amount of nitrogen-containing gas generated by thermal decomposition of the nitrogen component in the soil, and estimating the amount of nitrogen component contained in the soil from the detected amount of nitrogen-containing gas.

[0050] In the present invention, the gas detection unit of the gas sensor is directly inserted into the soil, and the soil in contact with the outer surface of the gas detection unit is heated to thermally decompose the nitrogen-containing component contained in the soil. When the nitrogen-containing component is thermally decomposed, at least a part of the nitrogen-containing component is converted into nitrogen-containing gas. As the nitrogen-containing gas, N 2 , N 2 O, NO, NO 2 , NH 3 etc. are considered to be generated. These nitrogen-containing gases generated by thermal decomposition are introduced into the gas detection unit and detected by a gas sensor that uses at least one or more of the nitrogen-containing gases as the measurement target gas.

[0051] The gas sensor only needs to be a gas sensor in which the outer surface of the gas detection unit inserted into the soil is maintained at a temperature sufficient to thermally decompose the nitrogen component in the soil in contact with the outer surface, and the nitrogen-containing gas can be measured. The nitrogen-containing gas as the measurement target gas may be, for example, at least one or more selected from the group consisting of NO, NO 2 , and NH 3 .

[0052] The gas sensor may be, for example, an electrochemical gas sensor using a solid electrolyte. For example, it may be a limiting current type gas sensor using an oxygen ion conductive solid electrolyte (for example, Japanese Patent No. 3050781, etc.), or a mixed potential type gas sensor or the like. Alternatively, it may be a limiting current type gas sensor using a proton conductive solid electrolyte, or a mixed potential type gas sensor or the like. Further, not limited to the gas sensor using a solid electrolyte, other types of gas sensors configured to keep the outer surface of the gas detection unit at a temperature capable of thermally decomposing the nitrogen component in the soil may be used.

[0053] For example, the gas sensor includes a long plate-shaped sensor element including an oxygen ion conductive solid electrolyte. The gas detection unit A portion in contact with the gas to be measured on one end side in the longitudinal direction of the sensor element, A gas flow space for the gas to be measured formed on the one end side in the longitudinal direction of the sensor element, An in-vacuum measurement electrode disposed in the gas flow space for the gas to be measured, and a measurement pump cell including an out-of-vacuum measurement electrode disposed at a position different from the gas flow space for the gas to be measured and corresponding to the in-vacuum measurement electrode. In the detection step, the gas sensor may detect the amount of the nitrogen-containing gas in the gas to be measured based on the current flowing through the measurement pump cell.

[0054] The temperature of the outer surface of the gas detection unit of the gas sensor may be appropriately set to a temperature capable of thermally decomposing the nitrogen component in the soil in contact with the outer surface. The temperature of the outer surface of the gas detection unit may be, for example, 180 °C or higher, 200 °C or higher, 230 °C or higher, 250 °C or higher, 300 °C or higher, 350 °C or higher, etc. Further, the temperature of the outer surface of the gas detection unit may be, for example, 900 °C or lower, 800 °C or lower, 700 °C or lower, 500 °C or lower, 400 °C or lower, etc.

[0055] An embodiment of a method for measuring the amount of nitrogen components in soil using a gas sensor will be described below with reference to the drawings. FIG. 1 is a schematic explanatory diagram of a state in which the gas detection unit 110 of the gas sensor 100 of this embodiment is inserted into the soil Soil to be measured. FIG. 2 is a partial cross-sectional schematic diagram showing an example of the schematic configuration of the gas detection unit 110 of the gas sensor 100. FIG. 3 is a vertical cross-sectional schematic diagram in the longitudinal direction of the sensor element 101 showing an example of the schematic configuration of the gas sensor 100. The internal structure of the sensor element 101 is shown in detail in FIG. 3, and the internal structure of the sensor element 101 is omitted in FIG. 2. In the following, with reference to FIG. 3, up and down refer to the upper side of FIG. 3 as up and the lower side as down, the left side of FIG. 3 as the tip side, and the right side as the rear end side. Also, with reference to FIG. 3, the front side perpendicular to the paper surface is the right side, and the back side is the left side. In FIG. 2, when corresponding to FIG. 3, the left side of FIG. 1 is up, the right side is down, the lower side of FIG. 2 is the tip side, and the upper side is the rear end side. In this embodiment, as the gas sensor 100, a case where a limit current type gas sensor for measuring NOx (NO + NO 2 ) and NH 3 in the gas to be measured will be described as an example.

[0056] <Gas sensor> As shown in FIG. 1, the gas sensor 100 includes a gas detection unit 110 that introduces the gas to be measured and detects the nitrogen-containing gas in the gas to be measured as the gas to be measured, a stopper 130 provided on the rear end side of the gas detection unit 110, a body portion 140, a control device 150, and a lead wire 160 that electrically connects between the body portion 140 and the control device 150. Further, the gas sensor 100 includes a long plate-shaped sensor element 101 containing an oxygen ion conductive solid electrolyte. As shown in FIG. 2, the gas detection unit 110 includes a part on the tip side of the sensor element 101 and a protective cover 120 that protects the tip of the sensor element 101. In this embodiment, the outer surface of the protective cover 120 is the outer surface of the gas detection unit 110. Also, referring to FIGS. 2 and 3, a part of the tip side of the sensor element 101 included in the gas detection unit 110 includes a gas flow space 15 to be described later and a measurement pump cell 41.

[0057] The stopper 130 is a disc-shaped component having a diameter larger than that of the gas detection unit 110, and the sensor element 101 penetrates through its central axis. The stopper 130 fixes the sensor element 101 and ensures airtightness between the front end side and the rear end side of the sensor element 101. The stopper 130 functions as a positioning means when inserting the gas detection unit 110 into the soil. The rear end side of the sensor element 101 is accommodated inside the body portion 140. The lead wire 160 drawn out from the rear end of the body portion 140 is arranged to electrically connect each electrode (to be described later) of the sensor element 101 and the control device 150. In the present embodiment, each electrode of the sensor element 101 and the control device 150 are wired-connected by a lead wire, but they may be wirelessly connected at least partially.

[0058] (Sensor element) As shown in FIG. 3, the sensor element 101 is a long plate-shaped element including a base portion 102 having a structure in which a plurality of oxygen ion conductive solid electrolyte layers are laminated. The long plate shape also means a long plate shape or a strip shape. The base portion 102 includes a first substrate layer 1, a second substrate layer 2, a third substrate layer 3, a first solid electrolyte layer 4, a spacer layer 5, and a second solid electrolyte layer 6, each of which is made of an oxygen ion conductive solid electrolyte layer such as zirconia (ZrO 2 ). These six layers are laminated in this order from the lower side in the drawing view. The solid electrolyte forming these six layers is dense and airtight. The six layers may all have the same thickness, or may have different thicknesses for each layer. The layers are adhered to each other via an adhesive layer made of a solid electrolyte, and the base portion 102 includes the adhesive layer. In FIG. 3, the layer configuration consisting of the six layers is illustrated, but the layer configuration in the present invention is not limited to this, and any number of layers and layer configuration may be used.

[0059] Such a sensor element 101 is manufactured, for example, by performing predetermined processing and printing a circuit pattern on ceramic green sheets corresponding to each layer, then laminating them, and further firing and integrating them.

[0060] On one end side in the longitudinal direction of the sensor element 101, a measured gas flow passage 15 is formed. One end on the side where the measured gas flow passage 15 is formed is referred to as the tip hereinafter. At the tip portion in the longitudinal direction of the sensor element 101, a gas inlet 10 is formed between the lower surface of the second solid electrolyte layer 6 and the upper surface of the first solid electrolyte layer 4. The measured gas flow passage 15, that is, the measured gas flow portion, is formed in a mode in which, in the longitudinal direction from the gas inlet 10, a first diffusion rate-limiting portion 11, a buffer space 12, a second diffusion rate-limiting portion 13, a first internal space 20, a third diffusion rate-limiting portion 30, a second internal space 40, a fourth diffusion rate-limiting portion 60, and a third internal space 61 communicate in this order.

[0061] The gas inlet 10, the buffer space 12, the first internal space 20, the second internal space 40, and the third internal space 61 are spaces inside the sensor element 101 that are partitioned by the lower surface of the second solid electrolyte layer 6 for the upper part provided in a mode of punching out the spacer layer 5, the upper surface of the first solid electrolyte layer 4 for the lower part, and the side surface of the spacer layer 5 for the side part.

[0062] Each of the first diffusion rate-limiting portion 11, the second diffusion rate-limiting portion 13, and the third diffusion rate-limiting portion 30 is provided as two horizontally long slits (the opening has a longitudinal direction in a direction perpendicular to the drawing in FIG. 3). Each of the first diffusion rate-limiting portion 11, the second diffusion rate-limiting portion 13, and the third diffusion rate-limiting portion 30 may be in any form that imparts a desired diffusion resistance, and the form is not limited to the slit.

[0063] The fourth diffusion rate-limiting portion 60 is provided between the spacer layer 5 and the second solid electrolyte layer 6 as one horizontally long slit (the opening has a longitudinal direction in a direction perpendicular to the drawing in FIG. 3). The fourth diffusion rate-limiting portion 60 may be in any form that imparts a desired diffusion resistance, and the form is not limited to the slit.

[0064] Also, at a position farther from the tip side than the measured gas flow space 15, a reference gas introduction space 43 is provided between the upper surface of the third substrate layer 3 and the lower surface of the spacer layer 5, at a position where the side portion is partitioned by the side surface of the first solid electrolyte layer 4. The reference gas introduction space 43 has an opening at the other end (hereinafter referred to as the rear end) of the sensor element 101. In the reference gas introduction space 43, for example, air is introduced as the reference gas when measuring the concentration of NOx and NH 3 When measuring the concentration of, for example, air is introduced as the reference gas.

[0065] The air introduction layer 48 is a layer made of porous alumina, and the reference gas is introduced into the air introduction layer 48 through the reference gas introduction space 43. Also, the air introduction layer 48 is formed so as to cover the reference electrode 42.

[0066] The reference electrode 42 is an electrode formed in a manner sandwiched between the upper surface of the third substrate layer 3 and the first solid electrolyte layer 4. As described above, an air introduction layer 48 connected to the reference gas introduction space 43 is provided around it. That is, the reference electrode 42 is disposed so as to be in contact with the reference gas through the porous air introduction layer 48 and the reference gas introduction space 43. Also, as will be described later, it is possible to measure the oxygen concentration (oxygen partial pressure) in the first internal space 20, the second internal space 40, and the third internal space 61 using the reference electrode 42. The reference electrode 42 is formed as a porous cermet electrode (for example, a cermet electrode of Pt and ZrO 2 and).

[0067] In the measured gas flow space 15, the gas inlet 10 is a portion that opens to the external space, and the measured gas is taken into the sensor element 101 from the external space through the gas inlet 10.

[0068] In this embodiment, the measured gas flow space 15 is configured such that the measured gas is introduced from the gas inlet 10 that opens to the tip surface of the sensor element 101. However, the present invention is not limited to this configuration. For example, the recess of the gas inlet 10 may not exist in the measured gas flow space 15. In this case, the first diffusion rate-limiting section 11 substantially serves as the gas inlet.

[0069] Also, for example, the measured gas flow space 15 may be configured to have an opening that communicates with a position near the buffer space 12 or the buffer space 12 of the first internal space 20 on a side surface along the longitudinal direction of the base portion 102. In this case, the measured gas is introduced from the side surface along the longitudinal direction of the base portion 102 through the opening.

[0070] Also, for example, the measured gas flow space 15 may be configured such that the measured gas is introduced through a porous body.

[0071] The first diffusion rate-limiting section 11 is a part that imparts a predetermined diffusion resistance to the measured gas taken in from the gas inlet 10.

[0072] The buffer space 12 is a space provided to guide the measured gas introduced from the first diffusion rate-limiting section 11 to the second diffusion rate-limiting section 13.

[0073] The second diffusion rate-limiting section 13 is a part that imparts a predetermined diffusion resistance to the measured gas introduced from the buffer space 12 into the first internal space 20.

[0074] As a result, it is sufficient that the amount of the measured gas introduced into the first internal space 20 is within a predetermined range. That is, it is sufficient that a predetermined diffusion resistance is imparted from the tip of the sensor element 101 to the entire second diffusion rate-limiting section 13. For example, the first diffusion rate-limiting section 11 may directly communicate with the first internal space 20, that is, there may be no buffer space 12 and second diffusion rate-limiting section 13.

[0075] The buffer space 12 is a space provided to mitigate the impact of pressure fluctuations of the gas to be measured on the detected value when the pressure of the gas to be measured fluctuates.

[0076] When the gas to be measured is introduced from outside the sensor element 101 into the first internal cavity 20, the gas to be measured that is rapidly taken into the sensor element 101 from the gas inlet 10 due to pressure fluctuations of the gas to be measured in the external space (if the gas to be measured is the exhaust gas of an automobile, the pulsation of the exhaust pressure) is not directly introduced into the first internal cavity 20. Instead, after the pressure fluctuations of the gas to be measured are canceled through the first diffusion rate-limiting section 11, the buffer space 12, and the second diffusion rate-limiting section 13, it is introduced into the first internal cavity 20. As a result, the pressure fluctuations of the gas to be measured introduced into the first internal cavity 20 are negligible.

[0077] The first internal cavity 20 is provided as a space for adjusting the oxygen partial pressure in the gas to be measured introduced through the second diffusion rate-limiting section 13. Such oxygen partial pressure is adjusted by the operation of the main pump cell 21.

[0078] The main pump cell 21 is an electrochemical pump cell composed of an inner main pump electrode 22 having a ceiling electrode portion 22a provided on substantially the entire lower surface of the second solid electrolyte layer 6 facing the first internal cavity 20, an outer pump electrode 23 provided in a manner exposed to the external space in a region corresponding to the ceiling electrode portion 22a on the upper surface of the second solid electrolyte layer 6, and the second solid electrolyte layer 6 sandwiched between these electrodes.

[0079] The inner main pump electrode 22 is disposed facing the first internal cavity 20 on the inner surface of the measured gas flow space 15. That is, the inner main pump electrode 22 is formed across the upper and lower solid electrolyte layers (the second solid electrolyte layer 6 and the first solid electrolyte layer 4) that partition the first internal cavity 20 and the spacer layer 5 that provides side walls. Specifically, a ceiling electrode portion 22a is formed on the lower surface of the second solid electrolyte layer 6 that provides the ceiling surface of the first internal cavity 20, a bottom electrode portion 22b is formed on the upper surface of the first solid electrolyte layer 4 that provides the bottom surface, and side electrode portions (not shown) are formed on the side wall surfaces (inner surfaces) of the spacer layer 5 that constitute both side wall portions of the first internal cavity 20 so as to connect the ceiling electrode portion 22a and the bottom electrode portion 22b, and are disposed in a structure in a tunnel form at the disposed positions of the side electrode portions.

[0080] The inner main pump electrode 22 and the outer pump electrode 23 are formed as porous cermet electrodes (for example, a cermet electrode of Pt containing 1% Au and ZrO 2 with). Note that the inner main pump electrode 22 that contacts the measured gas is formed using a material with reduced reduction ability for NOx components in the measured gas.

[0081] In the main pump cell 21, a desired pump voltage Vp0 is applied between the inner main pump electrode 22 and the outer pump electrode 23 by the variable power supply 24, and a pump current Ip0 is passed between the inner main pump electrode 22 and the outer pump electrode 23 in the positive or negative direction, so that oxygen in the first internal cavity 20 can be pumped out to the external space, or oxygen in the external space can be pumped into the first internal cavity 20.

[0082] Also, in order to detect the oxygen concentration (oxygen partial pressure) in the atmosphere in the first internal cavity 20, an electrochemical sensor cell, that is, a main pump control oxygen partial pressure detection sensor cell 80 is constituted by the inner main pump electrode 22, the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, the third substrate layer 3, and the reference electrode 42.

[0083] By measuring the electromotive force (voltage V0) in the oxygen partial pressure detection sensor cell 80 for main pump control, the oxygen concentration (oxygen partial pressure) in the first internal cavity 20 can be known. Further, the pump current Ip0 is controlled by feedback - controlling the pump voltage Vp0 so that the voltage V0 becomes constant. Thereby, the oxygen concentration in the first internal cavity 20 can be maintained at a predetermined constant value.

[0084] The third diffusion - rate - determining section 30 is a portion that imparts a predetermined diffusion resistance to the gas to be measured whose oxygen concentration (oxygen partial pressure) is controlled by the operation of the main pump cell 21 in the first internal cavity 20, and guides the gas to be measured to the second internal cavity 40.

[0085] The second internal cavity 40 is provided as a space for more precisely adjusting the oxygen partial pressure in the gas to be measured introduced through the third diffusion - rate - determining section 30. Such an oxygen partial pressure is adjusted by the operation of the auxiliary pump cell 50.

[0086] In the second internal cavity 40, after the oxygen concentration (oxygen partial pressure) has been adjusted in the first internal cavity 20 in advance, the oxygen partial pressure of the gas to be measured introduced through the third diffusion - rate - determining section 30 is further adjusted by the auxiliary pump cell 50. Thereby, the oxygen concentration in the second internal cavity 40 can be maintained at a constant value with high precision, so that highly accurate concentration measurement is possible in such a gas sensor 100.

[0087] The auxiliary pump cell 50 is an auxiliary electrochemical pump cell composed of an auxiliary pump electrode 51 having a ceiling electrode portion 51a provided substantially over the entire lower surface of the second solid electrolyte layer 6 facing the second internal cavity 40, an outer pump electrode 23 (not limited to the outer pump electrode 23, and any appropriate electrode at a position different from the inside of the gas - to - be - measured flow cavity 15, for example, outside the sensor element 101 is sufficient), and the second solid electrolyte layer 6.

[0088] The auxiliary pump electrode 51 is disposed at a position on the inner surface of the measured gas flow space 15 that is far from the one end (tip end) in the longitudinal direction of the base portion 102 (sensor element 101) than the inner main pump electrode 22.

[0089] Such an auxiliary pump electrode 51 is disposed in the second internal space 40 in a structure having a tunnel form similar to that of the inner main pump electrode 22 provided in the previous first internal space 20. That is, a ceiling electrode portion 51a is formed on the second solid electrolyte layer 6 that provides the ceiling surface of the second internal space 40, and a bottom electrode portion 51b is formed on the first solid electrolyte layer 4 that provides the bottom surface of the second internal space 40. And side electrode portions (not shown) that connect the ceiling electrode portion 51a and the bottom electrode portion 51b are formed on both wall surfaces of the spacer layer 5 that provides the side walls of the second internal space 40, respectively, in a tunnel form structure.

[0090] Note that the auxiliary pump electrode 51 is also formed using a material with a reduced reduction ability for NOx components in the measured gas, similar to the inner main pump electrode 22.

[0091] In the auxiliary pump cell 50, by applying a desired pump voltage Vp1 between the auxiliary pump electrode 51 and the outer pump electrode 23 by the variable power supply 52, oxygen in the atmosphere in the second internal space 40 can be pumped out to the external space, or pumped into the second internal space 40 from the external space.

[0092] Also, in order to control the oxygen partial pressure in the atmosphere in the second internal space 40, an electrochemical sensor cell, that is, an oxygen partial pressure detection sensor cell 81 for auxiliary pump control, is constituted by the auxiliary pump electrode 51, the reference electrode 42, the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, and the third substrate layer 3.

[0093] Based on the electromotive force (voltage V1) detected by the oxygen partial pressure detection sensor cell 81 for controlling the auxiliary pump, the auxiliary pump cell 50 performs pumping by the variable power supply 52 whose voltage is controlled. As a result, the oxygen partial pressure in the atmosphere within the second internal cavity 40 is controlled to a low partial pressure that has substantially no influence on the measurement of NOx and NH 3 and is controlled to a low partial pressure that has substantially no influence on the measurement of NOx and NH

[0094] At the same time, the pump current Ip1 is used to control the voltage V0 of the oxygen partial pressure detection sensor cell 80 for controlling the main pump. Specifically, the pump current Ip1 is input as a control signal to the oxygen partial pressure detection sensor cell 80 for controlling the main pump, and by controlling the voltage V0 thereof, the gradient of the oxygen partial pressure in the measurement gas introduced from the third diffusion rate-limiting section 30 into the second internal cavity 40 is always kept constant. When used as a NOx·NH 3 sensor, due to the functions of the main pump cell 21 and the auxiliary pump cell 50, the oxygen concentration in the second internal cavity 40 is maintained at a constant value of about 0.001 ppm.

[0095] The fourth diffusion rate-limiting section 60 is a site that imparts a predetermined diffusion resistance to the measurement gas in which the oxygen concentration (oxygen partial pressure) is further lowered by the operation of the auxiliary pump cell 50 in the second internal cavity 40, and guides the measurement gas to the third internal cavity 61.

[0096] The third internal cavity 61 is provided as a space for measuring the NOx and NH 3 concentrations in the measurement gas introduced through the fourth diffusion rate-limiting section 60. The concentration of NOx+NH 3 is measured by the operation of the measurement pump cell 41.

[0097] The measurement pump cell 41 measures NOx+NH in the measurement gas within the third internal cavity 61 3The concentration is measured. The measurement pump cell 41 includes an in-vacancy measurement electrode (measurement electrode 44 in this embodiment) disposed within the measured gas flow cavity 15 (inner surface of the measured gas flow cavity 15), and an out-of-vacancy measurement electrode corresponding to the inner measurement electrode (outer pump electrode 23 in this embodiment) disposed at a position different from the measured gas flow cavity 15 of the base body portion 102. The in-vacancy measurement electrode is disposed within an internal cavity into which the measured gas is introduced through a diffusion rate-limiting portion within the measured gas flow cavity 15.

[0098] That is, in this embodiment, the measurement pump cell 41 is an electrochemical pump cell composed of a measurement electrode 44 provided on the upper surface of the first solid electrolyte layer 4 facing the third internal cavity 61, an outer pump electrode 23 (not limited to the outer pump electrode 23, and any appropriate electrode outside the measured gas flow cavity 15, for example, outside the sensor element 101 is sufficient), a second solid electrolyte layer 6, a spacer layer 5, and the first solid electrolyte layer 4.

[0099] The measurement electrode 44 is a porous cermet electrode. The measurement electrode 44 also functions as a NOx reduction catalyst for reducing NOx present in the atmosphere within the third internal cavity 61. For example, in this embodiment, the measurement electrode 44 is a porous cermet electrode of Pt and Rh and ZrO 2 and.

[0100] In the measurement pump cell 41, oxygen generated by the decomposition of nitrogen oxides in the atmosphere around the measurement electrode 44 can be pumped out, and the generated amount can be detected as the pump current Ip2.

[0101] Also, in order to detect the oxygen partial pressure around the measurement electrode 44, an electrochemical sensor cell, that is, a measurement pump control oxygen partial pressure detection sensor cell 82, is constituted by the first solid electrolyte layer 4, the third substrate layer 3, the measurement electrode 44, and the reference electrode 42. The variable power supply 46 is controlled based on the electromotive force (voltage V2) detected by the measurement pump control oxygen partial pressure detection sensor cell 82.

[0102] The measurement gas guided into the second internal space 40 reaches the measurement electrode 44 in the third internal space 61 through the fourth diffusion rate-limiting section 60 under the condition where the oxygen partial pressure is controlled. Nitric oxide NO in the measurement gas reaches the measurement electrode 44 without being decomposed at the main pump electrode 22 and the auxiliary pump electrode 51. Also, nitrogen dioxide NO 2 and ammonia NH 3 are converted to nitric oxide NO at the inner main pump electrode 22 and / or the auxiliary pump electrode 51, and the converted nitric oxide NO reaches the measurement electrode 44. Thus, NO, NO 2 and ammonia NH 3 all reach the measurement electrode 44 as NO.

[0103] Nitrogen oxides (present here as nitric oxide NO) in the measurement gas around the measurement electrode 44 are reduced (2NO → N 2 +O 2 ) to generate oxygen. Then, the generated oxygen is pumped by the measurement pump cell 41. At this time, the pump voltage Vp2 of the variable power supply 46 is controlled so that the voltage V2 detected by the oxygen partial pressure detection sensor cell 82 for controlling the measurement pump becomes constant. The amount of oxygen generated around the measurement electrode 44 is proportional to the concentration of nitrogen oxides (nitric oxide NO) in the measurement gas that has reached the measurement electrode 44. As described above, the nitrogen oxides (nitric oxide NO) in the measurement gas that have reached the measurement electrode 44 include NO converted from nitrogen dioxide NO 2 and / or ammonia NH 3 and the NO that originally existed as nitric oxide NO. Therefore, the concentration of NO in the measurement gas that has reached the measurement electrode 44 is considered to correspond to the total concentration of NO, NO 2 , and NH 3 in the measurement gas. The pump current Ip2 in the measurement pump cell 41 is a current value corresponding to the total amount of NO, NO 2 , and NH 3 in the measurement gas. Therefore, based on the pump current Ip2, NO, NO 2 , and NH in the measurement gas3 The total amount (total concentration) can be calculated.

[0104] Further, an electrochemical sensor cell 83 is constituted by the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, the third substrate layer 3, the outer pump electrode 23, and the reference electrode 42. The oxygen partial pressure in the gas to be measured outside the sensor can be detected by the electromotive force (voltage Vref) obtained by this sensor cell 83.

[0105] Furthermore, the sensor element 101 includes a heater unit 70 that plays a role in temperature adjustment for heating and keeping warm the sensor element 101 in order to enhance the oxygen ion conductivity of the solid electrolyte. The heater unit 70 includes a heater electrode 71, a heater 72, a heater lead 76, a through hole 73, a heater insulating layer 74, and a pressure dissipation hole 75.

[0106] The heater electrode 71 is an electrode formed in a manner of contacting the lower surface of the first substrate layer 1. By connecting the heater electrode 71 to an external power source, power can be supplied to the heater unit 70 from the outside.

[0107] The heater 72 is an electrical resistor formed in a manner of being sandwiched from above and below by the second substrate layer 2 and the third substrate layer 3. The heater 72 is connected to the heater electrode 71 through the heater lead 76 that is connected to the heater 72 and extends to the rear end side in the longitudinal direction of the sensor element 101 and the through hole 73, and generates heat by being supplied with power from the outside through the heater electrode 71, thereby heating and keeping warm the solid electrolyte forming the sensor element 101.

[0108] Further, the heater 72 is embedded across the entire area from the first internal cavity 20 to the third internal cavity 61, and it is possible to adjust the temperature of the entire sensor element 101 to the temperature at which the solid electrolyte is activated. It is only necessary that the temperature be adjusted so that the main pump cell 21, the auxiliary pump cell 50, and the measurement pump cell 41 can operate. It is not necessary for the entire area to be adjusted to the same temperature, and there may be a temperature distribution in the sensor element 101. For example, the sensor element 101 may be heated so that the temperature of the solid electrolyte and each electrode around the measured gas flow cavity 15 is about 750°C to about 900°C.

[0109] The protective cover 120 is configured to be heated by the sensor element 101 heated by the heater 72. That is, the heater 72 heats the entire gas detection unit 110 including a part on the tip side of the sensor element 101 and the protective cover 120, and functions as the heater in the present invention. The heater 72 may heat the gas detection unit 110 so that the outer surface of the gas detection unit 110, that is, the outer surface of the protective cover 120, reaches a temperature at which the nitrogen component in the soil in contact with the outer surface can be thermally decomposed.

[0110] In the sensor element 101 of the present embodiment, the heater 72 is embedded in the base portion 102, but the present invention is not limited to this embodiment. The heater 72 may be disposed so as to heat the base portion 102. That is, the heater 72 may be any heater that can heat the sensor element 101 to such an extent that the oxygen ion conductivity for the operation of the main pump cell 21, the auxiliary pump cell 50, and the measurement pump cell 41 described above is exhibited. For example, it may be embedded in the base portion 102 as in the present embodiment. Alternatively, for example, the heater portion 70 may be formed as a heater substrate separate from the base portion 102 and disposed at an adjacent position to the base portion 102.

[0111] In addition, in the gas sensor 100 of the present embodiment, the heater 72 heats the entire gas detection unit 110 composed of a part on the tip side of the sensor element 101 and the protective cover 120, but it is not limited thereto. In addition to the heater 72 that heats the sensor element 101, a heater for heating the protective cover 120 may be provided separately. By controlling the temperature of each of the plurality of heaters, each position of the gas detection unit 110 may be maintained at a desired temperature.

[0112] The heater insulating layer 74 is an insulating layer formed of an insulator such as alumina on the upper and lower surfaces of the heater 72 and the heater lead 76. The heater insulating layer 74 is formed for the purpose of obtaining electrical insulation between the second substrate layer 2 and the heater 72 and the heater lead 76, and electrical insulation between the third substrate layer 3 and the heater 72 and the heater lead 76.

[0113] The pressure release hole 75 penetrates the third substrate layer 3 and is formed so that the heater insulating layer 74 communicates with the reference gas introduction space 43. The pressure release hole 75 can relieve the increase in internal pressure accompanying the temperature rise in the heater insulating layer 74. Note that a configuration without the pressure release hole 75 may be employed.

[0114] Also, a range of a predetermined length in the longitudinal direction from the tip of the surface of the sensor element 101 may be covered with a porous protective layer (not shown). The porous protective layer is formed to protect the region where the internal cavity and electrodes exist in the sensor element 101 from thermal shock caused by, for example, splashing water. The porous protective layer is composed of, for example, ceramics such as alumina and preferably has a thickness of about 10 μm to 2000 μm. Also, it is preferably formed so as to withstand a force of up to about 50 N. Typically, the porous protective layer is formed on the surface of the sensor element 101 in a manner of being in close contact with the base portion 102.

[0115] The above-described sensor element 101 is incorporated into the gas sensor 100 in such a manner that the tip of the sensor element 101 is in contact with the gas to be measured, and the rear end of the sensor element 101 is in contact with the reference gas. The tip of the sensor element 101 is accommodated in the internal space of the protective cover 120 as shown in FIG. 2. Further, the rear end of the sensor element 101 is accommodated inside the body portion 140. The rear end of the sensor element 101 accommodated inside the body portion 140 is made to be in contact with the reference gas (for example, air).

[0116] (Gas detection unit) The gas detection unit 110 of the present embodiment is a portion in contact with the gas to be measured on the side of one end (tip) in the longitudinal direction of the sensor element 101, a gas flow passage 15 for the gas to be measured formed on the tip side of the sensor element, a measurement electrode 44 disposed in the gas flow passage 15 for the gas to be measured, and an outer measurement electrode (outer pump electrode 23) disposed at a position different from the gas flow passage 15 for the gas to be measured and corresponding to the measurement electrode 44 in the gas flow passage 15, and includes a measurement pump cell 41 including the same.

[0117] In the present embodiment, the gas detection unit 110 further includes a protective cover 120 that protects the tip of the sensor element 101. The protective cover 120 may be a bottomed cylindrical metal member that covers the tip side of the sensor element 101. The protective cover 120 is usually provided with a space through which the gas to be measured flows between the protective cover 120 and the sensor element 101. The protective cover 120 is indirectly heated by a heater 72 embedded in the sensor element 101, and the heat decomposes the nitrogen component in the soil in contact with the outer surface of the protective cover 120. The protective cover 120 has a vent hole 121 for introducing the nitrogen-containing gas generated by the thermal decomposition. The position, size, shape, number, etc. of the vent hole 121 are not limited to the example of FIG. 2 and may be appropriately selected. The vent hole 121 may be arranged so that the gas flows smoothly inside the protective cover 120 and the soil does not enter.

[0118] The temperature of the outer surface of the protective cover 120, that is, the outer surface of the gas detection unit 110, may be appropriately set as described above so as to be able to thermally decompose the nitrogen components in the soil in contact with the outer surface. In the present embodiment, the protective cover 120 is heated by the sensor element 101 heated by the heater 72. The temperature of the outer surface of the protective cover 120 can be adjusted to a desired temperature depending on, for example, the diameter, length, material, plate thickness, etc. of the protective cover 120. Further, for example, the temperature of the outer surface of the protective cover 120 may be adjusted according to the temperature of the sensor element 101 (that is, the heating temperature of the heater 72).

[0119] The gas detection unit 110 is inserted into a desired position of the soil Soil to be measured, The gas detection unit 110 heated by the heater 72 heats the soil Soil in contact with the outer surface of the gas detection unit, thermally decomposes the nitrogen components contained in the soil Soil, and generates nitrogen-containing gas, The gas detection unit 110 detects the amount of nitrogen-containing gas generated by thermal decomposition (in this embodiment, the total amount of NO, NO 2 , and NH 3 ).

[0120] (Control device) The gas sensor 100 of the present embodiment includes a control device 150 that controls the sensor element 101. In the gas sensor 100, the electrodes 22, 23, 51, 44, 42 of the sensor element 101 are electrically connected to the control device 150 via the lead wires 160, respectively. The control device 150 includes a general-purpose or dedicated computer. Control of the sensor element 101, detection of the gas to be measured, calculation of the amount of nitrogen components, etc. are realized by the CPU, memory, etc. mounted on the computer. The control device 150 may include the variable power supplies 24, 46, and 52 described above. In the present embodiment, the control device 150 operates each pump cell 22, 50, 41, and each sensor cell 80, 81, 82, 83 as described above, and controls the gas detection unit 110 to detect the gas to be measured.

[0121] The control device 150 also includes a calculation unit 151. The calculation unit 151 calculates the amount of nitrogen components in the soil Soil. The calculation unit 151 is configured to calculate the amount of nitrogen components in the soil Soil based on the amount of nitrogen-containing gas detected by the gas detection unit 110 (in this embodiment, the total amount of NO, NO 2 , and NH 3 ).

[0122] For example, the calculation unit 151 may store in advance the correlation between the amount of nitrogen-containing gas detected by the gas detection unit 110 of the gas sensor 100 and the amount of nitrogen components in the soil, and use the amount of nitrogen-containing gas detected by the gas detection unit 110 and the previously obtained correlation to calculate the amount of nitrogen components in the soil.

[0123] In this embodiment, the calculation unit 151 acquires the amount of nitrogen-containing gas detected by the gas detection unit 110, calculates the amount of nitrogen components in the soil based on the correlation between the amount of nitrogen-containing gas detected by the gas sensor 100 stored in advance and the amount of nitrogen components in the soil, and outputs it as a measurement value of the gas sensor 100. The correlation is stored in advance in the memory of the control device 150 that functions as the calculation unit 151. The correlation may be stored, for example, as an approximation formula or its coefficient, or as a map showing the correlation. It may generally be what is called a calibration curve. The correlation may be the same regardless of the soil to be measured, or may vary depending on the soil to be measured, the type of fertilizer used, etc. Since the behavior of thermal decomposition can vary depending on the state of the soil and the type of fertilizer used (form of nitrogen component), it would be better to obtain the correlation for each soil to be measured and the type of fertilizer used. For example, measurements may be made with the gas sensor 100 on a plurality of model soils with different nitrogen component contents (each nitrogen component amount is known), and the correlation between the amount of nitrogen-containing gas detected by the gas sensor 100 and the amount of nitrogen components in the soil may be obtained.

[0124] <Measurement> An example of a method for measuring the amount of nitrogen components in soil using the above gas sensor 100 will be described. The measurement method of the present invention includes an insertion step, a decomposition step, a detection step, and a calculation step. FIG. 4 is a schematic diagram showing the procedure for inserting the gas sensor 100 into the soil Soil. FIG. 5 is a schematic diagram showing an example of the time change of the pump current Ip2 during soil measurement.

[0125] First, an insertion step of inserting the gas detection unit 110 of the gas sensor 100 into a desired position of the soil Soil to be measured is performed. In the present embodiment, as shown in FIG. 4(1), a hole for inserting the gas detection unit 110 is made at a desired position of the soil Soil to be measured. When the gas detection unit 110 is inserted, it is preferable that the soil Soil to be measured is in contact with the outer surface of the gas detection unit 110. Therefore, a hole having approximately the same shape as the outer shape of the gas detection unit 110 may be made. For example, a cylindrical jig having the same or substantially the same outer diameter as the outer diameter of the gas detection unit 110 may be inserted to the same or substantially the same depth as the insertion depth of the gas detection unit 110 to make a hole. Then, the gas detection unit 110 is inserted into the previously made hole as shown in FIG. 4(2). Alternatively, the gas detection unit 110 may be directly inserted into a desired position of the soil Soil to be measured without previously making a hole as shown in FIG. 4(1). Making a hole in advance as shown in FIG. 4(1) is more preferable because soil is less likely to enter the inside of the gas detection unit 110 (the inside of the protective cover 120 in the present embodiment) compared to the case where the gas detection unit 110 is directly inserted. Also, in the case where the soil Soil is hard, deformation of the gas detection unit 110 can be prevented by making a hole in advance.

[0126] The gas sensor 100 may be inserted into the soil Soil to be measured in a driven state, that is, in a state where the gas sensor 100 is detecting a nitrogen-containing gas as the gas to be measured. Alternatively, the gas sensor 100 may be driven after being inserted into the soil Soil to be measured. It is more preferable to insert the gas detection unit 110 into the soil Soil after the gas sensor 100 is driven and the temperature of the gas detection unit 110 and the control of each pump cell 21, 50, 41 reach a steady state, because nitrogen-containing gas can be detected quickly and accurately after insertion.

[0127] Next, the gas detection unit 110 heated by the heater 72 heats the soil in contact with the outer surface of the gas detection unit 110, and performs a decomposition step of thermally decomposing the nitrogen component contained in the soil to generate nitrogen-containing gas. In a state where the gas sensor 100 is driven, the outer surface of the gas detection unit 110 (the outer surface of the protective cover 120) is maintained at a temperature sufficient to thermally decompose the nitrogen component in the soil Soil. Therefore, the soil in contact with the outer surface of the gas detection unit 110 is heated by the gas detection unit 110, and the nitrogen component (nitrogen-containing component) contained in the soil is thermally decomposed to generate nitrogen-containing gas.

[0128] The soil in contact with the outer surface of the gas detection unit 110 includes the soil directly in contact with the outer surface of the gas detection unit 110 and the soil existing in the vicinity of the outer surface of the gas detection unit 110. The vicinity of the outer surface means the range of the soil where the nitrogen component decomposes when the soil is heated by the gas detection unit 110. The vicinity of the outer surface may be, for example, within a range of 2 mm or less, 5 mm or less, 1 cm or less, 5 cm or less, etc. from the outer surface of the gas detection unit 110. Since the decomposition temperature may vary depending on the type of nitrogen component (for example, the type of fertilizer used), the range in the vicinity of the outer surface of the gas detection unit 110 may vary. Also, since the way heat is transmitted may vary depending on the nature of the soil to be measured, the range in the vicinity of the outer surface of the gas detection unit 110 may vary. The range in the vicinity of the outer surface of the gas detection unit 110 can be adjusted according to the temperature of the outer surface of the gas detection unit 110. For example, in the soil to be measured, the range in the vicinity of the outer surface of the gas detection unit 110 may be adjusted in advance on site.

[0129] Next, a detection step is performed in which the amount of nitrogen-containing gas generated by pyrolysis is detected by the gas sensor 100. When the gas detection unit 110 is inserted into the soil Soil, the inside of the gas detection unit 110 (inside the protective cover 120) is usually filled with air. In the decomposition step, the nitrogen-containing gas generated by pyrolysis flows into the protective cover 120 through the vent holes 121 of the protective cover 120 by diffusion, and reaches the gas inlet 10 of the sensor element 101 as the gas to be measured in a state mixed with the air originally present. Then, as described above, the pump current Ip2 flowing through the measurement pump cell 41 is detected. Since the pump current Ip2 is a current that flows according to the total amount (total concentration) of NO, NO 2 , and NH 3 in the gas to be measured, it is possible to detect the amount of nitrogen-containing gas generated by pyrolysis based on this pump current Ip2.

[0130] In the detection step, the gas sensor 100 may detect the amount of nitrogen-containing gas in the gas to be measured (in this embodiment, the total amount of NO, NO 2 and NH 3 ) based on the pump current Ip2 flowing through the measurement pump cell 41.

[0131] For example, in the detection step, the gas sensor 100 may detect the amount of nitrogen-containing gas in the gas to be measured (in this embodiment, the total amount of NO, NO 2 and NH 3 ) based on the current integration value obtained by integrating the pump current Ip2 flowing through the measurement pump cell 41 for a predetermined time.

[0132] An example of the pump current Ip2 detected in the detection process is shown in FIG. 5. The horizontal axis in FIG. 5 represents time [seconds], and the vertical axis represents the pump current Ip2 [A]. When the gas detection unit 110 is inserted into the soil while the gas sensor 100 is being driven (time t1), nitrogen components in the soil near the outer surface of the gas detection unit 110 are thermally decomposed to generate nitrogen-containing gas (decomposition process), and the generated nitrogen-containing gas increases the pump current Ip2 (detection process). Since the nitrogen-containing gas generated by thermal decomposition is sequentially detected, as the thermal decomposition progresses, the pump current Ip2 increases. When substantially all of the nitrogen components in the soil near the outer surface of the gas detection unit 110 are thermally decomposed, the pump current Ip2 decreases and becomes almost zero (only almost the offset current) (time t2). Thus, the pump current Ip2 detected in the detection process flows as a current having a peak value with respect to the passage of time.

[0133] As described above, the pump current Ip2 is the current that flows due to oxygen when NO in the gas to be measured and NO 2 and NH 3 converted from are reduced. Therefore, the time integral value of the pump current Ip2 (current integral value), that is, the area A of the hatched portion in FIG. 5 corresponds to the total amount of NO, NO 2 and NH 3 detected by the gas sensor 100. That is, the time integral value of the pump current Ip2 (current integral value) is considered to correspond to the total amount (number of gas molecules) of NO, NO 2 and NH 3 generated when substantially all of the nitrogen components in the soil near the outer surface of the gas detection unit 110 are thermally decomposed. Therefore, as a detection value representing the amount of nitrogen-containing gas in the gas to be measured (in this embodiment, the total amount of NO, NO 2 and NH 3 ), the time integral value of the pump current Ip2 (current integral value) may be detected. For example, the time integral value of the pump current Ip2 (current integral value) from time t1 to time t2 in FIG. 5 may be detected as the detection value. The pump current Ip2 is used as the nitrogen-containing gas concentration in the gas to be measured (in this embodiment, NO, NO 2 and NH 3It may be converted into the total concentration) and the time integral value of the concentration may be detected as a detection value.

[0134] Further, the peak current value of the pump current Ip2, the average current value while the pump current Ip2 is flowing, or their concentration conversion values, etc., are used as the detection value representing the amount of the nitrogen-containing gas in the gas to be measured (in this embodiment, NO, NO 2 and NH 3 total amount).

[0135] Next, a calculation step of calculating the amount of nitrogen components in the soil is performed based on the amount of the nitrogen-containing gas detected in the detection step (for example, the time integral value of the pump current Ip2). The calculation unit 151 acquires the amount of the nitrogen-containing gas detected by the gas detection unit 110, and calculates the amount of nitrogen components in the soil based on the correlation between the amount of the nitrogen-containing gas detected by the gas sensor 100 stored in advance and the amount of nitrogen components in the soil, and outputs it as a measurement value of the gas sensor 100. As the amount of the nitrogen-containing gas, for example, the time integral value (current integral value) of the pump current Ip2 may be acquired. In this case, the correlation between the time integral value (current integral value) of the pump current Ip2 and the amount of nitrogen components in the soil may be obtained in advance, and the correlation may be stored in the calculation unit 151 in advance. For example, for a plurality of model soils with different nitrogen component contents (each nitrogen component amount is known), the time integral value (current integral value) of the pump current Ip2 may be measured respectively, and the correlation between the time integral value (current integral value) of the pump current Ip2 and the amount of nitrogen components in the soil may be obtained in advance.

[0136] Before measuring the amount of nitrogen components in the soil, a standard measurement process for obtaining the correlation between the amount of nitrogen-containing gas detected by the gas sensor 100 in advance and the amount of nitrogen components in the soil may be performed. The acquisition of the correlation (creation of a calibration curve) may be performed, for example, as follows. As the model soil for standard measurement, a plurality of model soils with different nitrogen component contents (each nitrogen component amount is known) may be used. Measure the plurality of model soils with the gas sensor 100, and detect the amount of nitrogen-containing gas [for example, the time integral value of the pump current Ip2 (current integral value)]. Thereby, the correlation between the amount of nitrogen components in each model soil and the amount of nitrogen-containing gas detected by the gas sensor 100 may be obtained. As the model soil, any soil may be sampled and used. In this case, for example, the amount of nitrogen components may be measured in advance by a conventional method. Commercially available culture soil or the like with a known nitrogen component amount may be used. More preferably, for example, for the soil to be measured, a plurality of model soils with different addition amounts of fertilizers used in the soil may be prepared and used.

[0137] In the gas sensor 100, the control device 150 of the gas sensor 100 includes a calculation unit 151, and the gas sensor 100 is configured to output the amount of nitrogen components in the soil, but is not limited thereto. The gas sensor 100 may be configured to output the pump current Ip2 (or its concentration-converted value), or the time integral value of the pump current Ip2 (or the time integral value of the concentration-converted value). In that case, an external calculation device (such as a computer) may be used to calculate the time integral value and / or the amount of nitrogen components in the soil.

[0138] The measurement position when measuring the soil (the position where the gas detection unit 110 of the gas sensor 100 is inserted) may be any position. The appropriate amount of nitrogen components in the soil is considered to vary depending on the type of crop. Therefore, for example, for each type of crop, the soil in which the crop is planted may be measured. Also, it may be measured in advance before planting the crop. Since the appropriate amount of nitrogen components in the soil may also vary depending on the growth stage of the crop, it is advisable to determine the measurement position in advance and perform fixed-point measurement by measuring at the right time according to the growth process of the crop.

[0139] [Method for Determining Nitrogen Component Content in Soil] Moreover, it is also possible to determine whether the nitrogen component content in the soil is excessive. When the nitrogen component content in the soil is excessive, there is a concern that the emission of N 2 O will increase. If it can be determined that the nitrogen component content in the soil is excessive, measures such as not applying fertilizer for a certain period can be taken, which is useful for reducing the emission of N 2 O. Since soil with excessive nitrogen component content can be identified, it will also be useful as an environmental survey of the soil.

[0140] The determination method of the present invention is a determination method for determining whether the nitrogen component content in the soil is excessive using a gas sensor, wherein the gas sensor comprises a gas detection unit that introduces the gas to be measured and detects the nitrogen-containing gas in the gas to be measured as the gas to be measured, a heater that heats the gas detection unit, and the determination method comprises an insertion step of inserting the gas detection unit of the gas sensor into a desired position of the soil to be measured, a decomposition step of heating the soil in contact with the outer surface of the gas detection unit by the gas detection unit heated by the heater, and thermally decomposing the nitrogen component contained in the soil to generate a nitrogen-containing gas, a detection step of detecting the amount of the generated nitrogen-containing gas by the gas sensor, and a determination step of determining that the nitrogen component content in the soil is excessive when the amount of the detected nitrogen-containing gas is greater than a predetermined value.

[0141] <Gas Sensor> In the determination method, the gas sensor, similar to the case of the above measurement method, has the outer surface of the gas detection unit inserted into the soil maintained at a temperature sufficient to thermally decompose the nitrogen component in the soil in contact with the outer surface, and any gas sensor capable of measuring the nitrogen-containing gas may be used. The nitrogen-containing gas as the gas to be measured is, for example, NO, NO 2 , and NH 3It may be at least one or more selected from the group consisting of.

[0142] <Judgment method> The insertion step, the decomposition step, and the detection step may be performed in the same manner as in the above-described measurement method. When the amount of the nitrogen-containing gas detected is greater than a predetermined value (reference value), a judgment step of judging that the amount of nitrogen components in the soil is excessive is performed.

[0143] For example, the calculation unit 151 of the gas sensor 100 described above may function as a judgment unit that performs the above judgment step. For example, the calculation unit 151 acquires the amount of the nitrogen-containing gas detected by the gas detection unit 110, and when the amount of the nitrogen-containing gas is greater than a reference value stored in advance, judges that the amount of nitrogen components in the soil is excessive, and may output (display, alarm, etc.) that it is excessive. The reference value may be stored in advance in the memory of the control device 150 that functions as the calculation unit 151 of the gas sensor 100.

[0144] The predetermined value (reference value) in the judgment step may be set in advance from the correlation between the amount of nitrogen-containing gas detected by the gas sensor 100 and the amount of nitrogen components in the soil. For example, the correlation between the amount of nitrogen-containing gas detected by the gas sensor 100 and the amount of nitrogen components in the soil is obtained in advance, and the amount of nitrogen-containing gas corresponding to the amount of nitrogen components to be judged as excessive is set as the predetermined value (reference value) in the judgment step. When the amount of nitrogen-containing gas detected by the gas sensor 100 is greater than this reference value, it may be judged that the amount of nitrogen components in the soil is excessive.

[0145] The amount of nitrogen components to be judged as excessive in the soil may vary depending on the properties of the soil to be measured, the type and growth stage of the crops planted (planted) in the soil, etc. Therefore, considering these, it may be appropriately set by a person involved in crop cultivation. Also, considering the emission regulation value of NO, etc., it may be appropriately set. 2 O, etc., it may be appropriately set.

[0146] In the determination process, the predetermined value (reference value) may be a single value regardless of the soil to be measured, or may be set respectively according to the type of soil and the type of crop planted in the soil.

[0147] Before performing the above-described determination method, a setting process of setting a reference value in advance may be performed. Similar to the standard measurement process in the above-described measurement method, a correlation relationship between the amount of nitrogen-containing gas detected by the gas sensor 100 and the amount of nitrogen component in the soil may be obtained. Then, the amount of nitrogen-containing gas corresponding to the amount of nitrogen component in the soil that has been studied and set in advance and is determined to be excessive may be set as the reference value.

[0148] Also, in the setting process, a model soil in which the amount of nitrogen component is adjusted in advance to the amount of nitrogen component that should be determined to be excessive in the soil is prepared, and the amount of nitrogen-containing gas detected when this model soil is measured by the gas sensor 100 [for example, the time integral value of the pump current Ip2 (current integral value)] may be set as the reference value. Alternatively, the reference value may be set based on the amount of nitrogen-containing gas detected in the model soil adjusted to an appropriate amount of nitrogen component (for example, by multiplying by a predetermined ratio). As the model soil, commercially available culture soil or the like with a known amount of nitrogen component may be used. More preferably, for example, for the soil to be measured, a soil obtained by adding the fertilizer used in that soil to adjust the amount of nitrogen component may be used.

[0149] [Application to good growth of agricultural crops] The above-described method for measuring and determining the amount of nitrogen component in the soil can also be applied to the good growth of agricultural crops. By supplying an appropriate amount of nitrogen component according to the growth stage of the agricultural crop, it can contribute to the good growth of the agricultural crop.

[0150] For example, the following method for growing agricultural crops can be cited.

[0151] A method for growing agricultural crops, measuring the amount of nitrogen component in the soil using a gas sensor, calculating the amount of fertilizer to be added to the soil based on the measured nitrogen component amount; The gas sensor includes a gas detection unit that introduces a gas to be measured and detects a nitrogen-containing gas in the gas to be measured as a gas to be measured; a heater that heats the gas detection unit; and the measurement of the nitrogen component amount includes an insertion step of inserting the gas detection unit of the gas sensor into a desired position of the soil to be measured; a decomposition step of heating the soil in contact with the outer surface of the gas detection unit by the gas detection unit heated by the heater, thermally decomposing the nitrogen component contained in the soil, and generating a nitrogen-containing gas; a detection step of detecting the amount of the generated nitrogen-containing gas by the gas sensor; and a calculation step of calculating the amount of the nitrogen component in the soil based on the detected amount of the nitrogen-containing gas. A method for growing crops.

[0152] A method for growing crops, judging whether the amount of the nitrogen component in the soil is appropriate using a gas sensor, in the judgment, when it is judged that the amount of the nitrogen component in the soil is insufficient, adding fertilizer to the soil, and when it is judged that the amount of the nitrogen component in the soil is appropriate or excessive, not adding fertilizer to the soil; the gas sensor includes a gas detection unit that introduces a gas to be measured and detects a nitrogen-containing gas in the gas to be measured as a gas to be measured; a heater that heats the gas detection unit; and the judgment of the nitrogen component amount includes an insertion step of inserting the gas detection unit of the gas sensor into a desired position of the soil to be measured; a decomposition step of heating the soil in contact with the outer surface of the gas detection unit by the gas detection unit heated by the heater, thermally decomposing the nitrogen component contained in the soil, and generating a nitrogen-containing gas; A detection step of detecting the amount of nitrogen-containing gas generated by the gas sensor, When the amount of the detected nitrogen-containing gas is within a predetermined range, it is determined that the amount of nitrogen components in the soil is appropriate. When the amount of the detected nitrogen-containing gas is less than the lower limit of the predetermined range, it is determined that the amount of nitrogen components in the soil is insufficient. When the amount of the detected nitrogen-containing gas is greater than the upper limit of the predetermined range, it is determined that the amount of nitrogen components in the soil is excessive. A determination step, a method for growing crops including.

[0153] [Modification example] FIG. 6 is a partial cross-sectional schematic view showing an example of the schematic configuration of the gas detection unit 210 of the gas sensor 200 of the modification example. In FIG. 6, the same components as those in FIG. 2 are denoted by the same reference numerals. The gas detection unit 110 of the above-described gas sensor 100 had a protective cover 120 for protecting the tip of the sensor element 101, but the gas detection unit of the present invention is not limited thereto. A configuration may be adopted in which there is no protective cover and the tip side of the sensor element 101 is exposed, as in the gas detection unit 210 of the gas sensor 200 of the modification example. In this case, the outer surface of the sensor element 101 is the outer surface of the gas detection unit 210. In this way, the temperature of the outer surface of the gas detection unit 210 can be made higher, the amount of soil in which nitrogen components are thermally decomposed can be increased, and the generation amount of nitrogen-containing gas can be increased, so that the measurement accuracy can be further improved. In this case, it is preferable that the surface of the sensor element 101 is covered with the above-described porous protective layer. When the gas inlet 10 is covered with the porous protective layer, it is considered that it is possible to prevent soil from entering the gas inlet 10 and causing clogging when inserted into the soil.

Example

[0154] Hereinafter, examples will be described. Note that the present invention is not limited to the following examples.

[0155] [Thermal decomposition test] The pyrolysis characteristics of multiple culture soils and nitrogen fertilizers were measured. The measurement was carried out by thermogravimetry-differential thermal analysis and mass spectrometry (TG-DTA-MS).

[0156] The following five samples were prepared. Sample 1: Culture soil 1 (organic culture soil; "Organic Soil" manufactured by Sakata Seed) Sample 2: Culture soil 2 (culture soil containing chemical fertilizer; "Vegetable Delight" manufactured by Sakata Seed) Sample 3: Chisso fertilizer 1 [chemical fertilizer: ammonium sulfate; "Ube Ammonium Sulfate" manufactured by Ube Industries] Sample 4: Chisso fertilizer 2 [chemical fertilizer: urea; "Urea Granular" manufactured by Mitsui Chemicals] Sample 5: Chisso fertilizer 3 (organic; "Oil Cake" manufactured by Daiso Industries)

[0157] Thermal analysis by TG-DTA-MS was performed on Samples 1 to 5. The measurement conditions were as follows.

[0158] Temperature range: room temperature to 500 °C Heating rate: 10 °C / min Gas atmosphere: 20%-O 2 Containing He atmosphere Gas flow rate: 300 mL / min Ionization method: EI method (electron ionization method) Mass range: m / z 10 - 210 Sample container: Al 2 O 3 Apparatus: Thermogravimetry-Mass Spectrometer Thermo Mass Photo manufactured by Rigaku

[0159] The generation of NO and NH as nitrogen-containing gases 3 was confirmed. The generation amounts and generation temperatures are shown in Table 1.

[0160]

Table 1

[0161] As shown in Table 1, for the nitrogen fertilizers of Samples 3 to 5, the generation of nitric oxide NO and ammonia NH 3 was confirmed. The generation temperatures of NO and NH 3 were different depending on the type of nitrogen fertilizer. For Samples 3 and 4, when comparing the nitrogen component amount with the generation amounts of NO and NH 3 , about 1 / 4 of the nitrogen component amount was detected as NO and NH 3 . It was confirmed that the nitrogen component amount could be calculated from the amounts of NO and NH 3 .

[0162] For the culture soils of Samples 1 to 2, it was below the detection limit (0.1 wt.%). According to the component table of the culture soil, the nitrogen content was about 500 ppm (0.05 wt.%), so it is considered that the generation amounts of NO and NH 3 were below the detection limit.

[0163] [Measurement Using Gas Sensor] Measurements were performed using the gas sensor 100 described in FIGS. 1 to 3. The gas sensor 100 was configured to output the concentration conversion value [ppm] of the pump current Ip2 as the sensor output value. When driving the gas sensor 100, the temperature of the outer surface of the gas detection unit 110 (the outer surface of the protective cover 120) was set to 500°C. As the soil to be measured, the above-mentioned Sample 2 (culture soil 2: containing chemical fertilizer) was used. According to the component table, the culture soil 2 was a soil with a nitrogen content of about 500 ppm.

[0164] An alumina crucible filled with the culture soil 2 was prepared. The gas sensor 100 was driven, and the gas detection unit 110 of the gas sensor 100 was inserted into the culture soil 2 in the alumina crucible. A thermometer was placed in the culture soil 2 near the gas detection unit 110. Then, the sensor output value of the gas sensor 100 and the output value of the thermometer (soil temperature) were monitored. The results of monitoring from 4 seconds before the insertion of the gas detection unit 110 into the soil to 30 seconds are shown in FIG. 7.

[0165] When the gas detection unit 110 is inserted into the culture soil 2 (for 4 seconds), the temperature of the culture soil 2 near the outer surface of the gas detection unit 110 (soil temperature) gradually rises and finally becomes almost the same as the temperature of the outer surface of the gas detection unit 110 (500 °C) (at 27 seconds). When the soil temperature reaches approximately 200 °C, the sensor output value begins to increase, takes a peak value (at 12 seconds), and then decreases to almost zero. Thus, it was confirmed that even for a culture soil with a nitrogen content of about 500 ppm, the gas sensor 100 can detect the nitrogen-containing gas generated by the thermal decomposition of the nitrogen component.

[0166] As described above, according to the present invention, by using a gas sensor, the amount of nitrogen component in the soil can be easily measured in situ. In addition, by using a gas sensor, it is also possible to easily determine whether the amount of nitrogen component in the soil is excessive in situ. By using these measurements and determinations, it is possible to prevent the amount of nitrogen component in the soil from becoming excessive, and the N 2 O emission can be reduced.

Description of Symbols

[0167] 10 Gas inlet 15 Measured gas flow space 23 Outer pump electrode 44 Measuring electrode 72 Heater 100 Gas sensor 101 Sensor element 110 Gas detection unit 120 Protective cover 130 Stopper 140 Body part 150 Control device 151 Calculation unit 160 Lead wire Siol Soil

Claims

1. A method for measuring the amount of nitrogen components in soil using a gas sensor, comprising: The gas sensor includes: A gas detection unit that introduces a gas to be measured and detects a nitrogen-containing gas in the gas to be measured as a gas to be measured; A heater that heats the gas detection unit; The measuring method includes: An insertion step of inserting the gas detection unit of the gas sensor into a desired position of the soil to be measured; A decomposition step of heating the soil in contact with the outer surface of the gas detection unit by the gas detection unit heated by the heater, and thermally decomposing the nitrogen components contained in the soil to generate a nitrogen-containing gas; A detection step of detecting the amount of the generated nitrogen-containing gas by the gas sensor; A calculation step of calculating the amount of nitrogen components in the soil based on the detected amount of the nitrogen-containing gas. A method for measuring the amount of nitrogen components in soil.

2. The gas sensor includes a long plate-shaped sensor element including an oxygen ion-conductive solid electrolyte, The gas detection unit includes: A portion in contact with the gas to be measured on one end side in the longitudinal direction of the sensor element; A gas flow space for the gas to be measured formed on one end side in the longitudinal direction of the sensor element; A measurement pump cell including an in-vacuum measurement electrode disposed in the gas flow space for the gas to be measured, and an out-of-vacuum measurement electrode disposed at a position different from the gas flow space for the gas to be measured and corresponding to the in-vacuum measurement electrode. In the detection step, the gas sensor detects the amount of the nitrogen-containing gas in the gas to be measured based on the current flowing through the measurement pump cell. The measurement method according to claim 1.

3. In the detection step, the gas sensor detects the amount of the nitrogen-containing gas in the gas to be measured based on the current integration value obtained by integrating the current flowing through the measurement pump cell for a predetermined time. The measurement method according to claim 2.

4. The outer surface of the gas detection unit of the gas sensor is maintained at a temperature of 180°C or higher. The measurement method according to claim 1.

5. The outer surface of the gas detection unit of the gas sensor is maintained at a temperature of 500°C or lower. The measurement method according to claim 1.

6. The gas detection unit of the gas sensor includes a protective cover that protects one end in the longitudinal direction of the sensor element, The outer surface of the protective cover is the outer surface of the gas detection unit of the gas sensor. The measurement method according to claim 2.

7. ​ The outer surface of the portion of the sensor element that is in contact with the gas to be measured on the side of one end in the longitudinal direction is the outer surface of the gas detection portion of the gas sensor. The measurement method according to claim 2.

8. In the calculating step, using the amount of nitrogen-containing gas detected by the gas sensor, the correlation between the amount of nitrogen-containing gas detected by the gas sensor obtained in advance, and the amount of nitrogen component in the soil, the amount of nitrogen component in the soil is calculated. The measurement method according to claim 1.

9. The nitrogen-containing gas as the gas to be measured by the gas sensor is at least one gas selected from the group consisting of nitric oxide NO, nitrogen dioxide NO ２ , and ammonia NH ３ The measurement method according to claim 1, which is at least one gas selected from the group consisting of

10. A determination method for determining whether the amount of nitrogen component in soil is excessive using a gas sensor, wherein the gas sensor comprises a gas detection portion that introduces a gas to be measured and detects nitrogen-containing gas in the gas to be measured as a gas to be measured, a heater that heats the gas detection portion, and the determination method includes an insertion step of inserting the gas detection portion of the gas sensor into a desired position of the soil to be measured, a decomposition step of heating the soil in contact with the outer surface of the gas detection portion by the gas detection portion heated by the heater, and thermally decomposing the nitrogen component contained in the soil to generate nitrogen-containing gas, a detection step of detecting the amount of the generated nitrogen-containing gas by the gas sensor, and a determination step of determining that the amount of nitrogen component in the soil is excessive when the detected amount of nitrogen-containing gas is greater than a predetermined value. A method for determining the amount of nitrogen component in soil.

11. A gas sensor used for measuring the amount of nitrogen component in soil, wherein the gas sensor comprises a gas detection portion that introduces a gas to be measured and detects nitrogen-containing gas in the gas to be measured as a gas to be measured, a heater that heats the gas detection portion, and a calculation portion that calculates the amount of nitrogen component in soil, and the gas detection portion is inserted into a desired position of the soil to be measured, the gas detection portion heated by the heater heats the soil in contact with the outer surface of the gas detection portion, and thermally decomposes the nitrogen component contained in the soil to generate nitrogen-containing gas, the gas detection portion detects the amount of the generated nitrogen-containing gas, and the calculation portion calculates the amount of nitrogen component in the soil based on the detected amount of nitrogen-containing gas. A gas sensor.

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