JP6556866B2 - Method for precise measurement of carbonic acid parameters in seawater and measuring apparatus used in the method - Google Patents

Description

Cross reference

  This application claims priority based on Japanese Patent Application No. 2015-253030 filed in Japan on December 25, 2015, the contents of which are incorporated herein by reference. Moreover, the content described in the patent quoted in this application, a patent application, and literature is used for this specification.

  The present invention relates to a precise measurement method of carbonic acid parameters of seawater and a measurement apparatus used in the method.

  Global warming due to an increase in the concentration of carbon dioxide in the atmosphere is an important issue for humankind to solve. With the increase of carbon dioxide in the atmosphere, it is predicted that the pH of the ocean will decrease from 8.3 before the Industrial Revolution to 8.2 until now and to 8.0 to 7.8 by the 21st century Yes, ocean acidification is progressing reliably. When oceanic acidification reduces the carbonate ion concentration in the sea and reduces calcium carbonate saturation, calcification of calcified organisms is also suppressed, and finally calcification organisms begin to dissolve. In particular, corals, pteropods, sea urchins, and foraminifera and lime algae having a high Mg calcite skeleton, which are more easily dissolved than calcite, are strongly affected by ocean acidification. In addition, since pH controls various physiological processes of living organisms, ocean acidification has a significant impact on the growth and reproduction of all living organisms in the ocean, not just the calcified organisms. On the other hand, the increase in carbon dioxide in the sea also has the effect of promoting photosynthesis, and the composition of the primary producers of the ocean, the food chain, and the ecosystem will change drastically, which may reduce the diversity of marine organisms. .

  The ocean absorbs approximately one-third of the carbon dioxide released by mankind due to the burning of fossil fuels, etc., and evaluating and strengthening the absorption capacity is the key to solving the above problems. In order to evaluate the carbon dioxide absorption capacity of the ocean, precise measurement of the marine carbonic acid system is required, in which carbon dioxide dissolved in the ocean hydrates and dissociates into bicarbonate ions and carbonate ions. There are four measurable quantities of marine carbonic acid parameters: pH, carbon dioxide partial pressure, total carbonic acid concentration and total alkalinity. If two of these quantities are determined, other carbonic acid parameters can be determined by an equilibrium equation.

  Among the carbonic acid parameters required for evaluating the carbon dioxide absorption capacity of the ocean, the pH can be continuously measured most easily by a glass electrode or a colorimetric method. However, high-precision measurement of pH is extremely difficult and cannot be used to know the state of carbonic acid in the ocean. Carbon dioxide partial pressure can be continuously measured by a seawater-gas phase equilibrator and a non-dispersive infrared measuring instrument. However, since a gas-liquid equilibrator is required and it is a trace component in the carbonic acid system and fluctuates in correlation with pH, an error in the carbonic acid system parameter obtained from the carbon dioxide partial pressure and pH becomes extremely large.

  On the other hand, total alkalinity and total carbonic acid concentration can be obtained with high accuracy by coulometric / potentiometric titration by collecting seawater and adding an acid to each sample. From this, it is considered that obtaining the total alkalinity and the total carbonic acid concentration among the carbonic acid parameters of the ocean is superior to obtaining the pH and the carbon dioxide partial pressure. About the method for calculating | requiring the total alkalinity and total carbonic acid density | concentration of seawater, it is disclosed by the nonpatent literature 1 and the patent document 1, for example.

Hideshi Saito, Satoshi Wada, Kazunobu Noyo and Shinji Masuda (2015): Observation of total carbonic acid concentration and total alkalinity at the Japan Meteorological Agency. Weather Report Vol. 82 Special Issue 2015, S81-S97

JP 2009-264913 A

  However, the conventional technique has the following problems. First, the method disclosed in Non-Patent Document 1 is a batch-type measurement method, not a continuous measurement method. In the batch method, many samples are required, and much time is required to measure one sample. In shallow water and breeding experiments such as coral reefs where biological activity and seawater exchange are active, there are large temporal and spatial fluctuations in pH and total alkalinity. There is a problem that it takes labor and cost to measure. In addition, in the method disclosed in Non-Patent Document 1, when measuring the total alkalinity, the pH before and after the addition of acid is measured by the absorbance method, so that the measuring device becomes large and in-situ measurement of the ocean cannot be performed. Next, since the method disclosed in Patent Document 1 is a batch-type measurement method similar to the method disclosed in Non-Patent Document 1, it is not suitable for in-situ measurement of the ocean. Moreover, since it is necessary to measure pH before and after acid addition when determining the total alkalinity, it is difficult to measure the total alkalinity with high accuracy.

  The present invention has been made in order to solve the above-described problems, and is capable of continuous measurement by flowing a small amount of sample seawater, and is capable of highly accurate and long-term measurement. It aims at providing the measuring apparatus used for this method.

  The precise measurement method of seawater carbonic acid parameters according to an embodiment for achieving the above object is a method of measuring the carbonic acid parameters of seawater, wherein the total alkalinity and total carbonic acid concentration of the carbonic acid parameters are Prepare at least two types of standard seawater, each value of which is specified, flow each type of standard seawater separately into the main channel, and merge the acid solution from the middle of the main channel, During the flow of the standard mixture flow step and the standard mixture flow step, the voltage of various standard seawater before mixing the acid solution and the voltage of the standard mixture after mixing the acid solution A standard voltage measuring step for measuring each of the above, and preparing at least one sample seawater whose carbonaceous parameters are not specified, and allowing each sample seawater to flow in the main flow path, The sample solution before the acid solution is mixed in the sample mixture flow step in which the acid solution is joined from the middle of the flow path and the sample mixture of various sample seawater and acid solution flows, and the sample mixture flow step Sample voltage measurement step for measuring the voltage of the seawater and the voltage of the sample mixture after mixing the acid solution, and the total alkalinity of each of at least two standard seawater and the voltage of each standard mixture are one of the variables Using the proportional relationship with the calculated value, using the total alkalinity calculating step for calculating the total alkalinity of the sample seawater from the voltage of the sample mixture, and using the proportional relationship between the pH and voltage of each standard seawater, The pH calculation step for calculating the pH of the sample seawater from the voltage of the sample seawater, the total alkalinity of the sample seawater calculated by the total alkalinity calculation step, and the pH calculation Using the pH of the sample seawater calculated by the step, a total carbonic acid concentration calculation step for calculating at least the total carbonic acid concentration of the total carbonic acid concentration and the carbon dioxide partial pressure, which are carbonic acid parameters of the sample seawater, .

  Moreover, the precise measurement method of the carbonic acid parameter of seawater according to another embodiment prepares two types of the above-mentioned standard seawater, and performs the above-mentioned total alkalinity calculation step with the total alkalinity of each of the two types of standard seawater. And a step of calculating the total alkalinity of the sample seawater corresponding to the voltage of the sample mixed solution on a straight line having the above calculated values as coordinates, and the pH calculation step described above for each of the two types of standard seawater. It is good also as a step which calculates pH of sample seawater corresponding to a voltage of sample seawater on a straight line which uses pH of each and each voltage as a coordinate.

  Moreover, the precise measurement method of the seawater carbonic acid system parameter according to another embodiment may be configured such that the standard voltage measurement step or the sample voltage measurement step described above is a step of measuring the voltage a plurality of times at predetermined time intervals.

  Moreover, the measuring device according to an embodiment is a measuring device that measures the carbonic acid parameter of seawater, and at least two types of carbonic acid parameters in which the values of total alkalinity and total carbonic acid concentration are specified. Standard seawater, acid solution, at least one sample seawater whose carbon dioxide parameters are not specified, various standard seawater and acid solution standard mixtures, and various sample seawater and acid solution sample mixtures A substrate provided with a flow path, a seawater supply pump for supplying standard seawater and sample seawater to a part of the flow path, an acid solution supply pump for supplying an acid solution to a part of the flow path, a measuring instrument provided for the substrate, and the same And a controller for receiving a signal or information from outside and specifying a carbonic acid parameter, and the substrate is a main channel through which standard seawater and sample seawater flow, and a channel through which an acid solution flows. A first voltage sensor, which is one of the measuring devices provided on the upper stream side from the junction of the sub-flow path joining the middle of the main flow path and the sub-flow path in the main flow path, and the sub-flow path in the main flow path A second voltage sensor that is one of the measuring devices provided downstream from the junction, and the control unit receives a signal from the central processing unit and the first voltage sensor and the second voltage sensor. The central processing unit is a voltage obtained by measuring the standard seawater with the first voltage sensor, a voltage obtained by measuring the standard mixed solution with the second voltage sensor, a voltage obtained by measuring the sample seawater with the first voltage sensor, Using the voltage measured by the second voltage sensor, the total alkalinity of the standard seawater, and the total carbonic acid concentration of the sample liquid mixture, the total carbonic acid concentration and carbon dioxide partial pressure, which are carbonic acid system parameters of the sample seawater, are used. At least the total carbonic acid concentration It is a device that out.

  In the measuring device according to another embodiment, at least one of the first voltage sensor and the second voltage sensor described above may be an ion response field effect transistor type voltage sensor.

  In the measuring device according to another embodiment, at least one of the seawater supply pump and the acid solution supply pump described above may be a piezo micropump.

  According to the present invention, it is possible to provide a precise measurement method for seawater carbonic acid parameters and a measurement device used in the method, which can continuously measure by flowing a small amount of sample seawater and enable high-precision and long-term measurement. .

FIG. 1 shows a schematic diagram of a measuring apparatus according to an embodiment of the present invention. 2 shows a configuration when attention is paid to the function of the central processing unit (CPU) in FIG. 1 and an example of a calculation formula stored in the storage unit in FIG. FIG. 3 shows a flow of processing of an example of a precise measurement method of seawater carbonic acid parameters according to an embodiment of the present invention. FIG. 4 is a diagram (4B) for explaining the process of calculating the total alkalinity of the sample seawater by inputting the voltage of the sample mixture into the linear equation (I) (4A) and the linear equation (I). Respectively. FIG. 5 shows a diagram (5B) for explaining a process for calculating the pH of the sample seawater by inputting the voltage of the sample seawater to the example (5A) of the linear formula (II) and the linear formula (II). .

1 Measuring device 10 Plate (substrate)
13, 15, 16, 17, 19, 21 Channel 14 First voltage sensor (an example of a measuring instrument, ion-responsive field-effect transistor type voltage sensor)
18 Subchannel (an example of a channel)
20 Second voltage sensor (an example of a measuring instrument, ion response field effect transistor type voltage sensor)
25 Main channel (part of channel)
31 Seawater supply pump (piezo micro pump)
32 Acid solution supply pump (piezo micro pump)
40 Control units 41, 42 Voltage signal receiving unit 45 CPU (Central Processing Unit)
70, 71 Standard seawater 72 Sample seawater 80 Acid solution M Confluence

  Next, each embodiment of the precise measurement method of the carbonic acid parameter of seawater and the measurement apparatus used in the method according to the present invention will be described with reference to the drawings. Each embodiment described below does not limit the invention according to the scope of claims, and all the elements and combinations thereof described in each embodiment are included in the present invention. It is not always essential to the solution.

<1. Configuration of measuring device>
FIG. 1 shows a schematic diagram of a measuring apparatus according to an embodiment of the present invention.

  Measuring device 1 concerning this embodiment is a measuring device which measures the carbonic acid system parameter of seawater. In the present application, the carbonic acid parameter of seawater means four types of parameters that can be measured: “pH”, “carbon dioxide partial pressure”, “total alkalinity”, and “total carbonic acid concentration” in seawater. The measuring device 1 includes at least a plate 10 serving as a place for flowing seawater, a pump module 30, and a control unit 40. The pump module 30 is driven and controlled by a pump driving device 60 connected thereto.

(1) Plate The plate 10 has specified at least two types of standard seawater 70, 71, acid solution 80, and carbonic acid parameters in which the values of total alkalinity and total carbonic acid concentration among the carbonic acid parameters are specified. The substrate includes a flow path through which at least one kind of sample seawater 72, various standard seawaters 70 and 71 and a standard mixed solution of the acid solution 80, and various sample seawater 72 and the sample mixed solution of the acid solution 80 flow. . In this embodiment, a substrate (more specifically, referred to as miniTAS Flow Plate) in which a liquid flow path is formed inside a transparent resin plate is used as the plate 10. The acid solution 80 may be a liquid containing at least an acid, such as only an acid or an acid + water. In this embodiment, an aqueous hydrochloric acid solution is used as the acid solution 80.

  The flow path includes standard seawater 70 and 71, sample seawater 72, a liquid obtained by mixing the standard seawater 70 and 71 and the acid solution 80 (hereinafter referred to as “standard mixed liquid”), and the sample seawater 72 and the acid solution 80. The main flow path 25 through which the mixed liquid (hereinafter referred to as “sample mixed liquid”) flows and the sub flow path 18 through which the acid solution 80 flows and merges in the middle of the main flow path 25 are included. The main channel 25 includes a channel 13, a channel 15, a channel 16, a channel 17, a channel 19, and a channel 21. The flow path 13 and the flow path 15 are flow paths that are continuously formed with the first voltage sensor 14 interposed therebetween, and are the flow paths through which the standard seawater 70 and 71 or the sample seawater 72 flows. The flow path 16 is a flow path formed by merging the sub-flow path 18 at a confluence point M in the middle, and the standard seawater 70 and 71 or the sample seawater 72 flows above the merge point M, and the merge point. On the downstream side of M, there is a flow path through which the standard mixed solution or the sample mixed solution flows. The channel 17 is a channel through which the standard mixed solution or the sample mixed solution flows, and also has a function as a mixer. The channel 19 and the channel 21 are channels that are continuously formed with the second voltage sensor 20 interposed therebetween, and are channels through which a standard mixed solution or a sample mixed solution flows.

  The plate 10 includes a first hole portion 11 and a second hole portion 12 that function as tube connectors at starting points on the most upstream side of the main flow path 25 and the sub flow path 18 respectively. The first hole portion 11 is a hole connected from the outside of the plate 10 to the internal flow path 13 and serves as an inlet for supplying the standard seawater 70 and 71 or the sample seawater 72 to the main flow path 25. The second hole portion 12 is a hole connected from the outside of the plate 10 to the internal sub-channel 18 and serves as an inlet for supplying the acid solution 80 to the sub-channel 18. Further, the plate 10 includes a third hole portion 22 that functions as a tube connector at a return point on the most downstream side of the main flow path 25. The third hole portion 22 is a hole connected from the outside of the plate 10 to the internal flow path 21 and serves as an outlet for discharging the standard mixed solution or the sample mixed solution to the outside.

  The first voltage sensor 14 is a sensor for measuring each voltage of the standard seawater 70 and 71 or the sample seawater 72 before being mixed with the acid solution 80. The second voltage sensor 20 measures each voltage of the standard seawater 70 and 71 (that is, the standard mixed solution) after being mixed with the acid solution 80 or the sample seawater 72 (that is, the sample mixed solution) after being mixed with the acid solution 80. It is a sensor for measuring. The first voltage sensor 14 and the second voltage sensor 20 are preferably ion response field effect transistor type voltage sensors (ISFET sensors). By using the ISFET sensor, it is easy to incorporate the first voltage sensor 14 and the second voltage sensor 20 into the plate 10, and the size of the measurement and flow system can be reduced, and thus the size of the measuring apparatus 1 can be reduced. It is most preferable that both the first voltage sensor 14 and the second voltage sensor 20 are ISFET sensors, but only one of the first voltage sensor 14 and the second voltage sensor 20 is an ISFET sensor. You can also.

  The first voltage sensor 14 is connected to the control unit 40 by a source line 51 and a drain line 52. Each voltage of the standard seawater 70 and 71 or the sample seawater 72 flowing through the main flow path 25 on the upper stream side from the junction M is detected by the first voltage sensor 14. The sensing time interval of the voltage by the first voltage sensor 14 can be set as desired, and in this embodiment, it is set at an interval of 1 second. The second voltage sensor 20 is connected to the control unit 40 by a source line 55 and a drain line 56. Each voltage of the standard mixed solution or the sample mixed solution flowing in the main flow path 25 on the downstream side from the junction M is detected by the second voltage sensor 20. The voltage sensing time interval by the second voltage sensor 20 can also be set as desired, similarly to the first voltage sensor 14, and in this embodiment, it is set at an interval of 1 second. The control unit 40 includes a reference electrode 54 connected to the reference line 53 and a reference electrode 58 connected to the reference line 57. The reference electrode 54 is in contact with the flow path 13, and the reference electrode 58 is in contact with the flow path 21. As a result, accurate voltage measurement using the first voltage sensor 14 and the second voltage sensor 20 becomes possible.

(2) Pump module The pump module 30 includes a seawater supply pump 31 and an acid solution supply pump 32. The seawater supply pump 31 is a pump that supplies the standard seawater 70 and 71 and the sample seawater 72 to the main flow path 25 (corresponding to a part of the flow path formed in the plate 10). The acid solution supply pump 32 is a pump that supplies the acid solution 80 to the auxiliary flow path 18 (corresponding to a part of the flow path formed in the plate 10) 18. The seawater supply pump 31 includes standard seawaters 70 and 71 and an inlet 31 a for sample seawater 72, and standard seawaters 70 and 71 and an outlet 31 b for sample seawater 72. The inlet 31 a is connected to a tube 74 for sucking the standard seawater 70, the standard seawater 71, or the sample seawater 72 from the first container 73 containing the standard seawater 70, the standard seawater 71, or the sample seawater 72 into the seawater supply pump 31. The The outlet 31 b is connected to a tube 35 for sending the standard seawater 70, the standard seawater 71 or the sample seawater 72 from the seawater supply pump 31 to the first hole portion 11 of the plate 10. The acid solution supply pump 32 includes an inlet 32 a for the acid solution 80 and an outlet 32 b for the acid solution 80. The inlet 32 a is connected to a tube 84 for sucking the acid solution 80 from the second container 83 containing the acid solution 80 to the acid solution supply pump 32. The outlet 32 b is connected to a tube 36 for sending the acid solution 80 from the acid solution supply pump 32 to the second hole portion 12 of the plate 10.

  When the seawater supply pump 31 is driven, the standard seawater 70, the standard seawater 71 or the sample seawater 72 in the first container 73 enters the seawater supply pump 31 from the inlet 31a via the tube 74, and passes through the tube 35 from the outlet 31b. And enters the first hole section 11. When the acid solution supply pump 32 is driven, the acid solution 80 in the second container 83 enters the acid solution supply pump 32 from the inlet 32a via the tube 84 and passes through the tube 36 from the outlet 32b to the second. Enter the hall section 12. The seawater supply pump 31 and the acid solution supply pump 32 are preferably piezo micro pumps. By using a piezo micropump, the flow system can be downsized, and thus the measuring apparatus 1 can be downsized. It is most preferable that both the seawater supply pump 31 and the acid solution supply pump 32 are piezo micropumps, but only one of the seawater supply pump 31 and the acid solution supply pump 32 is a piezo micropump. You can also. As the piezo micro pump, for example, “APP-20KG” manufactured by Takasago Electric Co., Ltd. can be used.

(3) Control part The control part 40 receives the signal or information from the 1st voltage sensor 14 and the 2nd voltage sensor 20 as a measuring instrument with which the plate 10 is provided, and those other than those, and receives the carbonic acid system parameter of seawater. It is a component for specifying. The control unit 40 includes at least a central processing unit (CPU) 45 and voltage signal receiving units 41 and 42 that receive signals from the first voltage sensor 14 and the second voltage sensor 20, respectively. In the voltage signal receiving unit 42, the source line 55, the drain line 56, and the reference line 57 are connected to the plate 10 side at points P, Q, and R in FIG. In this embodiment, the control unit 40 preferably includes A / D converters 43 and 44, a storage unit 46, and a battery 47 in addition to the above-described components. Each component in the control unit 40 is electrically connected to each other via a communication line called a bus.

  The A / D converter 43 is a component that converts an analog signal of the voltage from the first voltage sensor 14 into a digital signal. The A / D converter 44 is a component that converts an analog signal of a voltage from the second voltage sensor 20 into a digital signal. The storage unit 46 is a variety of information, for example, the value of each voltage measured by the first voltage sensor 14 and the second voltage sensor 20, a calculation formula for calculating one or more of the carbonic acid parameters, seawater temperature, At least part or all of values such as the temperature of the measurement site, the pH and concentration of the acid solution 80, the flow rate of flowing the standard seawater 70, 71 or the sample seawater 72 to the main channel 25, the flow rate of flowing the acid solution 80 to the subchannel 18 Is a component in which is stored. The storage unit 46 also stores a control program for the CPU 45. The storage unit 46 is preferably configured to be able to read and write various types of information. However, the storage unit 46 may include a RAM capable of reading and writing information and a ROM capable of only reading. As the storage unit 46, for example, a hard disk, an EEPROM, or the like can be employed. The battery 47 is a power source for supplying power to the control unit 40 and various measuring instruments on the plate 10 (including the first voltage sensor 14 and the second voltage sensor 20).

  The CPU 45 measures the standard seawater 70, 71 with the voltage measured by the first voltage sensor 14, the standard mixed solution with the voltage measured with the second voltage sensor 20, the sample seawater 72 with the voltage measured with the first voltage sensor 14, Using the voltage measured by the second voltage sensor 20, the total alkalinity of the standard seawater 70 and 71, and the total carbonic acid concentration, the total carbonic acid concentration and the carbon dioxide as the carbonic acid parameters of the sample seawater 72 are used. At least the total carbonic acid concentration within the carbon partial pressure can be calculated. The processing of the CPU 45 will be described in detail later.

(4) Pump Drive Device The pump drive device 60 includes a pump driver 61 and a battery 62. The pump driver 61 is a driver circuit that drives and controls the seawater supply pump 31 and the acid solution supply pump 32. In this embodiment, the pump driver 61 is preferably a piezo pump driver circuit. The battery 62 is a power source for supplying power to at least the pump driver 61 among the pump driver 61, the seawater supply pump 31 and the acid solution supply pump 32.

(5) Container The first container 73 is a container for separately containing the standard seawater 70, the standard seawater 71, or the sample seawater 72 (collectively referred to as “seawater”). The first container 73 is provided with a tube 74 inserted so as to be in contact with the seawater contained therein.

  The second container 83 is a container for containing the acid solution 80. The second container 83 is provided with a tube 84 inserted so as to be in contact with the acid solution 80 put therein.

  The third container 93 is a container for storing waste liquid (standard mixed liquid or sample mixed liquid) outside the plate 10 through the flow path 21. A tube 94 connected to the third hole portion 22 is inserted into the third container 93 and receives waste liquid sent from the flow path 21 via the tube 94.

<2. Measurement principle>
Next, based on the known carbonic acid parameters of the standard seawaters 70 and 71 and the voltage before and after the mixing of the acid solution 80 of the standard seawaters 70 and 71 and the sample seawater 72, the unknown carbonic acid parameters of the sample seawater 72 are specified. A method will be described.

Inorganic carbonic acid in seawater mainly takes the form of CO ₂ (= H ₂ CO ₃ ), HCO ₃ ⁻ , CO ₃ ²⁻ , and an equilibrium as shown in the formula (1) is established.
CO ₂ + H ₂ O⇔HCO ₃ ⁻ + H ⁺ ⇔CO ₃ ²⁻ + 2H ⁺ (1)
At this time, the following relationship is established via the equilibrium coefficients K ₁ and K ₂ .
K ₁ = [HCO ₃ ⁻ ] [H ⁺ ] / [CO ₂ ] (2)
K ₂ = [CO ₃ ²⁻ ] [H ⁺ ] / [HCO ₃ ⁻ ] (3)
Further, the following relationship holds as the equilibrium of H ₂ O.
K _W = [H ⁺ ] [OH ⁻ ] (4)

In order to determine the carbonic acid system parameter of seawater, it is necessary to measure at least two of measurable total alkalinity (A _T ), total carbonic acid concentration (C _T ), pH, and carbon dioxide partial pressure (pCO ₂ ). There is. A _T , C _T and pH are respectively defined as follows (DOE, 1994).
A _T = [HCO ₃ ⁻ ] +2 [CO ₃ ²⁻ ] + [B (OH) ₄ ⁻ ] + [OH ⁻ ] − [H ⁺ ] + minor components ([HPO ₄ ²⁻ ] +2 [PO ₄ ³⁻ ] + [H ₃ SiO ₄ ⁻ ] + [NH ₃ ] + [HS ⁻ ] − [HSO ₄ ⁻ ] − [HF] − [H ₃ PO ₄ ]) (5)
C _T = [CO ₂ ] + [HCO ₃ ⁻ ] + [CO ₃ ²⁻ ] (6)
pH = −log ₁₀ [H ⁺ ] (7)

For boron (B), the following relationship holds (Millero, 1979).
K _B = [B (OH) ₄ ⁻ ] [H ⁺ ] / [B (OH) ₃ ] (8)
B _T = [B (OH) ₃ ] + [B (OH) ₄ ⁻ ]
= 1.212 * 10 ⁻⁵ S (mol kg ⁻¹ ) (9)
Here, S is salt content.
Millero, F.M. J. et al. (1979) The thermodynamics of the carbonate system in sea water. Ceochimi. Cosmochimi. Acta, Vol. 43, p. 1651-1661.
(Above equilibrium constant _{K 1, K 2, K W} , K B are determined by temperature and salinity and pressure.)

  Next, with reference to the above formulas (1) to (9), a sample whose carbonic acid parameters are unknown using two types of standard seawaters 70 and 71 whose total alkalinity and total carbonic acid concentration are known. The carbonic acid parameter of the seawater 72 is calculated.

(1) Identification of total alkalinity When a certain amount of hydrochloric acid or aqueous hydrochloric acid solution (hereinafter simply referred to as “hydrochloric acid”) is added to standard seawater 70, 71 (A _T = A _T1 , A _T = A _T2 ). It is assumed that the voltage V ′ measured by the second voltage sensor 20 is (V ′ ₁ , V ′ ₂ ). At that time, there is linearity between _AT and 10 ^{(V ′ / (RTln10 / F))} (where R = 8.3145, T = 273.15 + t (measured temperature ° C.), F = 96485). ). Therefore, the coordinates of the standard seawater 70 (10 ^{(V′1 / (RTln10 / F))} , A _T1 ) and the coordinates of the standard seawater 71 (10 ^{(V′2 / (RTln10 / F))} , A _T2 ) Obtaining the linear equation (I) from two points and substituting the voltage (V′x) of the sample seawater 72 after the addition of hydrochloric acid into the linear equation (I), the total alkalinity (A _Tx ) of the sample seawater 72 is obtained. Can do.

(2) Identification of total carbonic acid concentration Next, the pH of the sample seawater 72 (because it is a pH determined by calculation, it is referred to as “calc.pH”).

First, the _{A T} and _{C T} from a known standard seawater 70 and 71, solves the equilibrium formula below, calculate each pH standard seawater 70 and 71.
From DOE (1994), for _{A T} and _{C T,} which consists the following relationship.
A _T = [CO ₂ ] (K ₁ / [H ⁺ ] + 2K ₁ K ₂ / [H ⁺ ] ² )
+ B _T K _B / (K _B + [H ⁺ ]) + K _W / [H ⁺ ] − [H ⁺ ] (10)
C _T = [CO ₂ ] (1 + K ₁ / [H ⁺ ] + K ₁ K ₂ / [H ⁺ ] ² ) (11)

When the above (10) and (11) are arranged, the following equation (12) is established.
C _T (K ₁ / [H ⁺ ] + 2K ₁ K ₂ / [H ⁺ ] ² )
= (A _T -B _T K _B / (K _B + [H ⁺ ])
^{_{-K W / [H +] +}} [H +]) (1 + K 1 / [H +] + K 1 K 2 / [H +] 2) ··· (12)

When the above equation (12) is further developed, a quintic equation of the following equation (13) is obtained.
^{_{[H +] 5 + (A}} T + K B + K 1) [H +] 4 + {- K W (K B + K 1) + K 1 (K B (A T -B T -C T) + K B K 1 + K ^{_{1 K 2} [H +]}} 3 + {- K W (K B + K 1) + K 1 [K B (A T -B T -C T) + (A T -2C T) K 2] + K B K 1 ^{_{K 2} [H +] 2}} + {- K W K 1 (K B + K 2) + K B K 1 K 2 (A T -2C T -B T)} [H +] -K W K B K 1 K ₂
= 0 (13)

Solving the above equation (13) provides one positive solution and four negative solutions, but the positive solution is [H ⁺ ]. The pH can be obtained by substituting into the above equation (7) (DOE (1994), Handbook of Methods for the Analysis of the Various Parameters of the Carbon Dioxide System in the World. G. and Goyet, C., ORNL / CDIAC-74.).

Calc. Calculated for standard seawater 70, 71. There is linearity between pH (calc.pH ₁ , calc.pH ₂ ) and the voltage V (V ₁ , V ₂ ) measured by the first voltage sensor 14 of the standard seawater 70, 71. For this reason, a linear equation (II) is obtained from two points of the coordinates (V ₁ , calc.pH ₁ ) of the standard seawater 70 and the coordinates (V ₂ , calc.pH ₂ ) of the standard seawater 71, and the linear equation (II ) Is substituted for the voltage (Vx) of the sample seawater 72 before the addition of hydrochloric acid, the calc. pH _x can be determined.

Next, the total alkalinity (A _Tx ) of the sample seawater 72 and calc. From the pH _x , the calc. C _Tx is obtained.

From the above equation (10), the following relationship is established, and [CO ₂ ] can be obtained.
[CO ₂ ]
_{= (A T -B T K B} / (K B + [H +]) - K W / [H +] + [H +]) / (K 1 / [H +]
+ 2K ₁ K ₂ / [H ⁺ ] ² ) (14)

On the other hand, the following formula (15) is established from the above formulas (2), (3), and (6).
[CO ₂ ] = C _T / (1 + K ₁ / [H ⁺ ] + K ₁ K ₂ / [H ⁺ ] ² ) (15)
Therefore, C _T (= calc.C _Tx ) of the sample seawater 72 can be calculated by substituting [CO ₂ ] obtained by the above formula (14) into the following formula (16). At the same time, the partial pressure of carbon dioxide can be obtained.
C _T = [CO ₂ ] (1 + K ₁ / [H ⁺ ] + K ₁ K ₂ / [H ⁺ ] ² ) (16)
Note that the total carbonic acid concentration (calc.C _Tx ) of the sample seawater 72 may be obtained before the total alkalinity (A _Tx ) of the sample seawater 72.

<3. Arithmetic processing of CPU of measuring device>
2 shows a configuration when attention is paid to the function of the central processing unit (CPU) in FIG. 1 and an example of a calculation formula stored in the storage unit in FIG.

  The CPU 45 includes an information storage unit (also referred to as information storage unit) 101, an information reading unit (also referred to as information reading unit) 102, a total alkalinity calculation unit (also referred to as total alkalinity calculation unit) 103, and a pH calculation unit ( Functions as a total carbonic acid concentration calculation unit (also referred to as total carbonic acid concentration calculation unit) 105 and a carbon dioxide partial pressure calculation unit (also referred to as carbon dioxide partial pressure calculation unit) 106. The storage unit 46 can store the following expressions (17) and (18) in addition to the expressions (1) to (16).

A _T = a * 10 ^{(V ′ / (RTln10 / F))} + b (17)
calc. pH = c * V + d (18)

  In the above equation (17), the variable a represents the slope of the linear equation (I), and the variable b represents the intercept of the linear equation (I). In the above equation (18), the variable c represents the slope of the linear equation (II), and the variable d represents the intercept of the linear equation (II).

  The information storage unit 101 is a part that performs processing for storing each voltage measured by the first voltage sensor 14 and the second voltage sensor 20 and other information input from the outside in the storage unit 46. The information reading unit 102 is a part that performs processing for reading information such as various data, various programs, various formulas, and the like from the storage unit 46.

The total alkalinity calculation unit 103 uses the total alkalinity (A _T1 , A _T2 ) of each of the standard seawaters 70 and 71 and the voltage (V ′ ₁ , V ′ ₂ ) of each standard mixed solution as part of the variables. Processing for calculating the total alkalinity (A _Tx ) of the sample seawater 72 from the voltage (V′x) of the sample mixed solution using the proportional relationship with the calculated value (10 ^{(V ′ / (RTln10 / F))} ) It is a part to do. Specifically, the total alkalinity calculating unit 103 adds the total alkalinity A _Tx (A _T1 , A _T2 ) of each of the standard seawaters 70 and 71 to the equation (17) read by the information reading unit 102, respectively. Substituting the voltage V ′ (V ′ ₁ , V ′ ₂ ) of the standard mixture solution, the variables a and b are obtained, and the linear equation (I) is obtained. The total alkalinity calculation unit 103 calculates the total alkalinity (A _Tx ) of the sample seawater 72 by substituting the voltage (V′x) of the sample mixed solution into the linear equation (I).

The pH calculation unit 104 calculates the proportional relationship between the pH (calc. pH ₁ , calc. pH ₂ ) of the standard seawater 70 and 71 and the voltage V (V ₁ , V ₂ ) before the addition of the acid solution 80. This is a part that performs processing for calculating the pH (= calc.pH _x ) of the sample seawater 72 from the voltage Vx of the sample seawater 72. Specifically, the pH calculation unit 104 adds each pH (calc.pH ₁ , calc.pH ₂ ) and each acid of the standard seawater 70 and 71 to the equation (18) read by the information reading unit 102. Substituting the voltage V (V ₁ , V ₂ ) before the addition of the solution 80, the variables c and d are obtained, and the linear equation (II) is obtained. The pH calculation unit 104 calculates the pH (calc.pH _x ) of the sample seawater 72 by substituting the voltage Vx of the sample seawater 72 into the linear equation (II). The pH calculation unit 104 uses Equation (7) and Equation (13) at a minimum to calculate the respective pH (calc.pH ₁ , calc.pH ₂ ) of the standard seawater 70 and 71. In addition, the pH calculation unit 104 may use other expressions among the expressions (1) to (18).

The total carbonic acid concentration calculation unit 105 includes the total alkalinity (A _Tx ) of the sample seawater 72 calculated by the total alkalinity calculation unit 103 and the pH of the sample seawater 72 calculated by the pH calculation unit 104 (= calc.pH _x ) To calculate a total carbonic acid concentration (C _Tx ), which is one of the carbonic acid parameters of the sample seawater 72. The total carbonic acid concentration calculation unit 105 uses Equation (14) and Equation (16) at a minimum to calculate the total carbonic acid concentration (C _Tx ) of the sample seawater 72. In addition, the total carbonic acid concentration calculation unit 105 may use other expressions among the expressions (1) to (18).

The carbon dioxide partial pressure calculation unit 106 uses the total alkalinity (A _Tx ) of the sample seawater 72 and the pH (= calc.pH _x ) of the sample seawater 72 calculated by the pH calculation unit 104, This is a part for performing a process of calculating a carbon dioxide partial pressure, which is one of 72 carbonic acid parameters. The carbon dioxide partial pressure calculation unit 106 uses Equation (16) at a minimum to calculate the carbon dioxide partial pressure of the sample seawater 72. Note that the carbon dioxide partial pressure calculation unit 106 may use other expressions among the expressions (1) to (18). Further, the carbon dioxide partial pressure calculation unit 106 may not be provided, and the total carbon dioxide concentration calculation unit 105 may have the function of the carbon dioxide partial pressure calculation unit 106 exhibited. In that case, the total carbonic acid concentration calculation unit 105 is a part that performs processing for calculating both the total carbonic acid concentration (C _T ) and the carbon dioxide partial pressure. This is because if the pH and total alkalinity of the four types of carbonic acid parameters are determined, both the total carbonic acid concentration and the carbon dioxide partial pressure can be calculated by the equations (14) and (16). .

<4. Precision measurement method for carbonic acid parameters in seawater>
Next, a precise measurement method of seawater carbonic acid parameters using the measuring apparatus 1 will be described.

  FIG. 3 shows a flow of processing of an example of a precise measurement method of seawater carbonic acid parameters according to an embodiment of the present invention.

  The precise measurement method of seawater carbonic acid parameters according to this embodiment includes a standard mixture flow step, a standard voltage measurement step, a sample mixture flow step, a sample voltage measurement step, a total alkalinity calculation step, A pH calculation step and a total carbonic acid concentration calculation step are included.

(1) Standard liquid mixture flow step (S201, S203)
This step prepares at least two types of standard seawater 70 and 71 in which the total alkalinity and total carbonic acid concentration values of the carbonic acid parameters are specified, and the various standard seawaters 70 and 71 are separately supplied to the main flow path. 25, the acid solution 80 is joined from the middle of the main flow path 25, and the standard mixed solution of various standard seawaters 70 and 71 and the acid solution 80 is caused to flow.

(2) Standard voltage measurement step (S202, S204)
This step is a step of measuring the voltage of various standard seawaters 70 and 71 before mixing of the acid solution 80 and the voltage of the standard mixture after mixing of the acid solution 80 during the flow in the standard mixture flow step. is there.

(3) Sample mixture flow step (S205)
This step prepares at least one type of sample seawater 72 for which the carbonic acid parameter is not specified, causes the sample seawater 72 to flow into the main flow path 25, joins the acid solution 80 from the middle of the main flow path 25, and In this step, the sample mixed solution of the sample seawater 72 and the acid solution 80 is flowed.

(4) Sample voltage measurement step (S206)
This step is a step of measuring the voltage of the sample seawater 72 before mixing the acid solution 80 and the voltage of the sample mixture after mixing the acid solution 80 during the flow of the sample mixture flow step.

  In the process of FIG. 3, step S201 and step S202 are performed first, then step S203 and step S204 are performed, and then step S205 and step S206 are performed. However, the order of steps S201 and S202, steps S203 and S204, and steps S205 and S206 may be changed. For example, step S203 and step S204 may be performed first, then step S201 and step S202 may be performed, and then step S205 and step S206 may be performed. Alternatively, step S205 and step S206 may be performed first, followed by step S203 and step S204, and then step S201 and step S202.

(5) Linear equation (I) calculation step (S301)
This step is a step executed by the total alkalinity calculation unit 103, and is a step for obtaining the linear equation (I) read from the storage unit 46, that is, the equation (17).

(6) Total alkalinity calculation step (S302)
This step is a step executed by the total alkalinity calculating unit 103, and includes a total alkalinity of at least two standard seawaters 70 and 71 and a calculated value in which the voltage of each standard mixture is one of the variables. This is a step of calculating the total alkalinity of the sample seawater 72 from the voltage of the sample mixture using the proportional relationship. In this embodiment, an example of the “calculated value” is 10 ^{(V ′ / (RTln10 / F))} . Specifically, the total alkalinity calculating step calculates the total alkalinity of the sample seawater 72 by inputting the voltage of the sample mixture into the linear equation (I).

  FIG. 4 is a diagram (4B) for explaining the process of calculating the total alkalinity of the sample seawater by inputting the voltage of the sample mixture into the linear equation (I) (4A) and the linear equation (I). Respectively.

Linear equation (I) connecting the coordinates (10 ^{(V1 ′ / (RTln10 / F))} , A _T1 ) of the standard seawater 70 and the coordinates (10 ^{(V2 ′ / (RTln10 / F))} , A _T2 ) of the standard seawater 71 ) is obtained, (the I), ^'10 was calculated on the basis of ^(Vx' voltage _{V x} of the sample mixture ^{/ (RTln10 / F)} linear equation ^{substituting),} it is possible to calculate the total carbonate concentration _{a Tx} .

(7) Linear equation (II) calculation step (S303)
This step is a step executed by the pH calculation unit 104, and is a step for obtaining the linear equation (II) read from the storage unit 46, that is, the equation (18).

(8) pH calculation step (S304)
This step is a step executed by the pH calculation unit 104, and uses the proportional relationship between the pH and voltage of each of the standard seawaters 70 and 71 to determine the pH of the sample seawater 72 from the voltage of the sample seawater 72 (= calc). , PH _x ). Specifically, the pH calculation step calculates the pH (= calc.pH _x ) of the sample seawater 72 by inputting the voltage of the sample seawater 72 into the linear equation (II).

  FIG. 5 shows a diagram (5B) for explaining a process for calculating the pH of the sample seawater by inputting the voltage of the sample seawater to the example (5A) of the linear formula (II) and the linear formula (II). .

A linear equation (II) connecting the coordinates (V ₁ , calc.pH ₁ ) of the standard seawater 70 and the coordinates (V ₂ , calc.pH ₂ ) of the standard seawater 71 is obtained, and the sample seawater 72 is obtained as the linear equation (II). substituting the voltage _{V x,} calc sample seawater 72. pH _x can be calculated.

(9) Total carbonic acid concentration calculation step (S305)
This step is a step executed by the total carbonic acid concentration calculation unit 105. The total alkalinity of the sample seawater 72 calculated by the total alkalinity calculation step and the pH of the sample seawater 72 calculated by the pH calculation step are calculated. This is a step of calculating at least the total carbonic acid concentration of the total carbonic acid concentration and the carbon dioxide partial pressure, which are the carbonic acid parameters of the sample seawater 72, by using.

  Note that the order of S301 to S305 is not limited to the order of FIG. 3, and may be changed in any order. For example, the processing may be performed in the order of S303, S304, S305, S301, and S302. Moreover, you may process in order of S301, S303, S302, S304, and S305.

In this embodiment, two types of standard seawater are prepared, and the total alkalinity calculation step includes the total alkalinity (A _T1 , A _T2 ) of each of the two types of standard seawater 70 and 71 and the calculated values (10 ^{( V1 ′ / (RTln10 / F))} , 10 ^{(V2 ′ / (RTln10 / F))} ) on the straight line whose coordinates are the steps of calculating the total alkalinity of the sample seawater 72 corresponding to the voltage of the sample mixture It is said. However, three or more types of standard seawater are prepared, and a straight line closest to three or more coordinates on the 10 ^{(V ′ / (RTln10 / F))} - _AT coordinate system is obtained by the least square method, and the straight line is used. Thus, the total alkalinity of the sample seawater 72 may be calculated. In such a case, it is not necessary to store the straight line expression of Expression (17) in the storage unit 46, and instead, an expression for obtaining a straight line closest to each coordinate by the least square method is stored in the storage unit 46. Is preferred. Three or more types of standard seawater are prepared, and V-calc. A straight line closest to three or more coordinates on the pH coordinate system may be obtained by the least square method, and the pH of the sample seawater 72 may be calculated using the straight line. In such a case, it is not necessary to store the straight line expression of the equation (18) in the storage unit 46. Instead, an expression or a program for obtaining a straight line closest to each coordinate by the least square method is stored in the storage unit 46. Preferably stored. Furthermore, instead of the least square method, polynomial approximation (curve approximation) may be performed. In that case, it is preferable to store an expression or a program for performing polynomial approximation in the storage unit 46.

  The standard voltage measurement step or the sample voltage measurement step is a step of measuring each voltage of the standard seawater 70, 71 or the sample seawater 72 a plurality of times every predetermined time, but may be measured only once instead of a plurality of times. .

  In contrast to the conventional batch method, which requires a minimum of 100 ml per sample, the continuous flow method of the present embodiment requires that the sample seawater 72 is flowed at 1 ml / min and the acid solution 80 is added per sample. Measurement is possible with 5 ml. Moreover, the measurement accuracy can be as high as 2 μmol / kg, which is equivalent to the conventional titration. In addition, the measurement apparatus 1 according to the present embodiment is mounted on a buoy, and automatic operation for one month is possible. Furthermore, the measuring device 1 is a small power consumption type and lightweight device with a power consumption of 40 W and a weight of 5 kg.

<5. Example of measurement of carbonic acid parameters in seawater>
Next, the carbonic acid parameters of the sample seawater were calculated from the voltages before and after the addition of the acid solution of the sample seawater using the known carbonic acid parameters in the two types of standard seawater and the values of the voltages before and after the addition of the acid solution. An example will be described.

As standard seawater, two types of seawater in which total alkalinity (A _T ) and total carbonic acid concentration (C _T ) were specified were used. Information on the standard seawater used is shown in Table 1. Table 2 shows the voltages measured before and after adding the acid solution to the standard seawater.

Three types of seawater were used as the sample seawater for calculation of carbonic acid parameters. Table 3 shows each voltage measured before and after adding the acid solution to each sample seawater, calculated total alkalinity (calc.A _T ) calculated using information on standard seawater in Tables 1 and 2, and calculation Total carbonic acid concentration (calc.C _T ), calculated pH (calc.pH), “Alternative method A _T ”, “Alternative method C _T ”, alternative method _AT and alternative method C _T “Alternative pH” calculated from the above and the salinity are shown. Here, the “alternative method” for measuring the total carbonic acid concentration is that by adding phosphoric acid to the seawater, all the carbonate-based dissolved species dissolved in the seawater are converted into gas phase carbon dioxide, and NDIR (LI It means a method of obtaining the C _T by measuring the carbon dioxide concentration using -820). The “alternative method” for measuring the total alkalinity means a method for obtaining the total alkalinity by titration with hydrochloric acid using a total alkalinity measuring instrument (ATT-05, Kimoto). Furthermore, “another method” for obtaining pH means a method for calculating pH from the total alkalinity and the total carbonic acid concentration previously measured by another method.

  As a result of measuring and calculating the voltage for the sample seawater 1 to 3, the calculated alkalinity, the calculated total carbonic acid concentration, and the calculated pH according to this method are the alkalinity of the alternative method and the total of the alternative method, respectively. It was found to be very close to the carbonic acid concentration and the alternative pH. Therefore, it is considered that the measurement reliability of the present invention is very high.

  The present invention can be used for high-accuracy measurement of carbonic acid parameters of seawater.

Claims (6)

A method for measuring carbonic acid parameters of seawater,
Preparing at least two types of standard seawater in which each value of total alkalinity and total carbonic acid concentration of the carbonic acid system parameters is specified, and causing each of the various standard seawaters to flow separately into the main flow path; A standard mixed solution flow step in which the acid solution is joined from the middle, and a standard mixed solution of various standard seawater and the acid solution is flowed,
A standard voltage measuring step for measuring various voltages of the standard seawater before mixing of the acid solution and voltages of the standard mixture after mixing of the acid solution during the flow in the standard mixture flow step;
Preparing at least one kind of sample seawater in which the carbonic acid parameter is not specified, causing the various types of sample seawater to flow into the main flow path, and joining the acid solution from the middle of the main flow path; A sample mixture flow step for flowing a sample mixture of seawater and the acid solution; and
A sample voltage measuring step for measuring a voltage of the sample seawater before mixing of the acid solution and a voltage of the sample mixture after mixing of the acid solution during the flow of the sample mixture flow step;
By utilizing the proportional relationship between the total alkalinity of each of the at least two standard seawaters and the calculated value with the voltage of each of the standard mixed liquids as one of the variables, the total voltage of the sample seawater is calculated from the voltage of the sample mixed liquid. A total alkalinity calculating step for calculating alkalinity;
A pH calculating step of calculating the pH of the sample seawater from the voltage of the sample seawater using the proportional relationship between the pH and voltage of each of the standard seawater;
The carbonic acid parameter of the sample seawater using the total alkalinity of the sample seawater calculated by the total alkalinity calculation step and the pH of the sample seawater calculated by the pH calculation step. A total carbonic acid concentration calculating step for calculating at least the total carbonic acid concentration of the total carbonic acid concentration and the carbon dioxide partial pressure;
Method for precise measurement of carbonic acid parameters in seawater containing water. Prepare two types of standard seawater,
In the total alkalinity calculating step, the total alkalinity of the sample seawater corresponding to the voltage of the sample mixed solution on a straight line having the total alkalinity of each of the two types of standard seawater and the calculated value as coordinates As a step to calculate the degree,
The pH calculation step is a step of calculating the pH of the sample seawater corresponding to the voltage of the sample seawater on a straight line having coordinates of the pH and voltage of each of the two types of standard seawater. 2. A precise measurement method for carbonic acid parameters of seawater according to 1.   The precise measurement method of the carbonic acid system parameter of seawater according to claim 1 or 2, wherein the standard voltage measurement step or the sample voltage measurement step is a step of measuring the voltage a plurality of times at predetermined time intervals. A measuring device for measuring carbonic acid parameters of seawater,
At least two types of standard seawater in which the values of total alkalinity and total carbonic acid concentration in the carbonic acid parameters are specified, acid solutions, at least one sample seawater in which the carbonic acid parameters are not specified, A substrate provided with a flow path for flowing a standard mixed solution of the standard seawater and the acid solution and a sample mixed solution of various sample seawater and the acid solution;
A seawater supply pump for supplying the standard seawater and the sample seawater to a part of the flow path;
An acid solution supply pump for supplying the acid solution to a part of the flow path;
A control unit for identifying the carbonic acid parameter by receiving a signal or information from the measuring instrument provided on the substrate and other external devices;
With
The substrate is
A main channel through which the standard seawater and the sample seawater flow;
A sub-flow path in which the acid solution flows and joins in the middle of the main flow path;
A first voltage sensor that is one of the measuring devices provided on the upper stream side from the junction with the sub-flow path in the main flow path;
A second voltage sensor that is one of the measuring devices provided on the downstream side from the junction with the sub-flow path in the main flow path;
With
The controller is
A central processing unit;
A voltage signal receiving unit for receiving signals from the first voltage sensor and the second voltage sensor;
Comprising at least
The central processing unit measures the voltage obtained by measuring the standard seawater using the first voltage sensor, the voltage obtained by measuring the standard mixed solution using the second voltage sensor, and the sample seawater measured using the first voltage sensor. Using the voltage, the voltage measured by the second voltage sensor for the sample mixture, the total alkalinity and the total carbonic acid concentration of the standard seawater, the total carbonic acid concentration that is the carbonic acid parameter of the sample seawater And a measuring device for calculating at least the total carbonic acid concentration of carbon dioxide partial pressure.   The measurement apparatus according to claim 4, wherein at least one of the first voltage sensor and the second voltage sensor is an ion response field effect transistor type voltage sensor.   6. The measuring apparatus according to claim 4, wherein at least one of the seawater supply pump and the acid solution supply pump is a piezo micro pump.