CN103616477B - Method for measuring daily mean stable carbon isotope composition of atmospheric carbon dioxide - Google Patents

Abstract

The invention discloses a method for measuring the daily average stable carbon isotope composition of atmospheric carbon dioxide, which is characterized in that: first, sodium bicarbonate produced by different manufacturers is measured as a tracer; The concentration of sodium bicarbonate in the solution was set to 10mM, and the pH was 8.30; thirdly, the above-prepared solution was used to cultivate plants with the same growth cycle at the same time, and after 24 hours of cultivation, the stable carbon isotope composition δ in the two isotope-labeled nutrient solutions was measured respectively. ¹³ C values, which are δ ₁ and δ ₂ values; fourth, put the measured δ _C1 , δ _C2 , δ ₁ and δ ₂ values into the equation , calculate the sodium bicarbonate that adds accounts for the share f _B of total inorganic carbon in the solution; The 5th, judge whether f _B value is less than 0.6, get each measured value that experiment obtains when f _B value is less than 0.60, bring into equation , calculate the average value of inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during the period of δ _a ; sixth, put the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , calculate the daily average stable carbon isotope composition δ _Ca of atmospheric carbon dioxide.

Description

A method for determining the daily average stable carbon isotope composition of atmospheric carbon dioxide

technical field

The invention relates to a method for measuring the daily average stable carbon isotope composition of atmospheric carbon dioxide, which belongs to the field of ecological environment system monitoring, control and restoration.

Background technique

_CO2 concentration has increased by 31% from the start of the Industrial Revolution to the present. There is strong evidence that these increases are largely due to the burning of fossil fuels for human activities such as transportation, heating, and electricity generation. The increase in greenhouse effect caused by _CO2 accounts for two-thirds of the current increase in greenhouse effect. Between 10,000 and 250 years ago, the concentration of CO ₂ in the atmosphere was very stable, maintaining between 260 and 280 ppmv. _CO2 concentrations have increased to 370 ppmv over the past 250 years, with most of the increase occurring in recent decades. Many factors clearly show that human activities are the main reason for the increase of greenhouse gas concentration. For example, there is good agreement between the current rate of increase in greenhouse gas concentrations and the rate of change in human emissions, and this has not been seen in the thousands of years of atmospheric history. In addition, the carbon isotopic composition of atmospheric carbon dioxide and the change trend of carbon dioxide distribution in the atmosphere are consistent with the emission of human activities.

The carbon isotopic composition of carbon dioxide released by the combustion of fossil fuels in human activities such as transportation, heating, and power generation is different from the carbon isotopic composition of carbon dioxide released by organisms, carbonate dissolution, and the atmosphere itself. Revealing the change trend of carbon dioxide in the study area in the past, present and future is of great importance for predicting the impact of human activities on future environmental changes, avoiding and controlling destructive climate and environmental changes, and for governing and restoring the ecological environment and promoting global sustainable development. significance.

In the past, the method of determining the stable carbon isotope composition of carbon dioxide in the atmosphere was mainly to collect the gas in the area to be measured and measure the carbon isotope. Due to the complexity of the gas in the region to be measured and the variability over time, it is difficult to obtain the stable carbon isotope composition values of atmospheric carbon dioxide with regional characteristics; only values at certain time points can be obtained, and these values are due to the gas The complexity brings a certain degree of measurement error. Therefore, it is of great significance to establish a method for determining the stable carbon isotope composition of carbon dioxide in the atmosphere that can represent regional characteristics for the study of global change. The present invention is based on the isotope two-way labeling method and utilizes the characteristic that plants can utilize bicarbonate ions to develop a method for measuring the daily average stable carbon isotope composition of atmospheric carbon dioxide.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for quickly obtaining the average stable carbon isotope composition of atmospheric carbon dioxide by using the two-way carbon isotope labeling technology, so as to overcome the difficulty in obtaining the stable carbon isotope composition value of atmospheric carbon dioxide with regional characteristics in the prior art. It is not enough to get the value of certain time points.

The present invention takes following technical scheme: it comprises the following steps:

First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2;

Second, add them to the nutrient solution respectively. The concentration of sodium bicarbonate in the nutrient solution is set to 10 mM, the pH is 8.30, the δ ¹³ C value of the bicarbonate ion in the solution of isotope label 1 is δ _C1 , and the value of isotope label 2 is δ C1 . The hydrogen carbonate ion δ ¹³ C value in the solution is δ _C2 ;

Thirdly, the above-prepared solutions are used to simultaneously cultivate plants with consistent growth cycles. After culturing for 24 hours, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled nutrient solutions are measured respectively, which are δ ₁ and δ ₂ values;

Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate to account for the share f _B of the total inorganic carbon in the solution;

Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained in the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average value of inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during the period of δ _a ;

Sixth, put the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} to calculate the daily average stable carbon isotope composition δ _Ca of atmospheric carbon dioxide.

In the first step, first measure the sodium bicarbonate produced by different manufacturers, select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as the tracers of isotope label 1 and isotope label 2, and add the sodium bicarbonate in the culture medium The larger the difference in the δ ¹³ C value of sodium bicarbonate, the easier it is to identify the effect of carbon dioxide in the air entering the bicarbonate ion in the solution, and it is easier to collect later experimental data.

In the second step, the tracers of isotope label 1 and isotope label 2 were added to the nutrient solution respectively. The δ ¹³ C value of the ion is δ _C1 , and the δ ¹³ C value of the bicarbonate ion in the isotope label 2 solution is δ _C2 . In this step, the prepared sodium bicarbonate concentration is 10 mM, and the pH is 8.30, so that sufficient bicarbonate ions are exchanged with carbon dioxide in the air to ensure that the culture medium is in an alkaline environment, so as to avoid the nutrient solution being caused by the bicarbonate ions in the nutrient solution. Too few ions lead to large measurement errors, or too many bicarbonate ions lead to too much saturation of bicarbonate ions in the solution and it is difficult to exchange with carbon dioxide.

In the third step, the above-prepared culture solution is used to cultivate plants with consistent growth at the same time. After 24 hours of cultivation, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled nutrient solutions are respectively measured, which are δ ₁ and δ ₂ values . In this step, it is ensured that the cultivated plants grow uniformly, and they must be cultivated in the same environment to be tested at the same time.

In the fourth step, the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ are brought into the equation , calculate the added sodium bicarbonate accounted for the total inorganic carbon in the solution f _B .

In the fifth step, it is judged whether the f _B value is less than 0.6, and each measured value obtained by the experiment is taken when the f _B value is less than 0.60, and brought into the equation , calculate the average value δ _a of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period; in this step, the f _B value is required to be less than 0.60, on the one hand to ensure the full exchange of bicarbonate ions and carbon dioxide in the air , which is convenient for later data estimation. On the other hand, it makes the hydrolysis balance of carbon dioxide develop towards the direction of generating bicarbonate, ensuring the value of △ _{CO2(air)- HCO3(aq)} in the later period.

In the sixth step, the calculated δ _a value is brought into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} to calculate the daily average stable carbon isotope composition δ _Ca of atmospheric carbon dioxide. In this step, due to the hydrolysis of carbon dioxide to form bicarbonate ions, there is isotope fractionation, which is about 8.5‰ in the equilibrium state at 25°C. Due to the rapid absorption and utilization of plants, the hydrolysis equilibrium of carbon dioxide develops towards the direction of generating bicarbonate ions. At this time The value of △ _{CO2(air)- HCO3(aq)} is 1.1‰. Therefore, the δ _a value calculated in this experiment is only the average value of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution. Therefore, the daily average stable carbon isotope composition δ _Ca value of atmospheric carbon dioxide is δ _a + 1.1‰.

The advantages of the present invention are as follows:

1) This method can quickly obtain the daily average stable carbon isotope composition of atmospheric carbon dioxide in different environments at different times;

2) This method has few steps and simple calculation;

3) This method can overcome the shortcomings of the existing technology that it is difficult to obtain stable carbon isotope composition values of atmospheric carbon dioxide with regional characteristics, and can only obtain values at certain time points;

4) This method uses the characteristics of plants to quickly absorb and utilize bicarbonate ions, so that the hydrolysis of carbon dioxide into bicarbonate ions is accelerated and unbalanced. On the one hand, it facilitates the hydrolysis of carbon dioxide to form a stable carbon isotope fractionation value of bicarbonate ions On the other hand, it is guaranteed that enough bicarbonate ions come from air carbon dioxide, so the obtained data is reliable.

Basic principle of the present invention is:

The strong fractionation signature of stable carbon isotopes is the basis for identifying different sources of inorganic carbon. There are two stable isotopes of carbon in nature: ¹² C and ¹³ C, and their natural average abundances are 98.89% and 1.11%, respectively. The stable carbon isotopic composition is usually represented by δ ¹³ C (‰), and the variation of δ ¹³ C in nature is -90‰ ~ +20‰. The strong fractionation signature of stable carbon isotopes facilitates the identification of different inorganic carbon sources. Mass balance principles, together with isotope mixing models and chemometric methods, are the basis for the quantitative identification of different inorganic carbon sources.

The isotope mixing model of the two-terminal can be expressed as:

δ _i = δ _Ca - f _Bi δ _a + f _Bi δ _ci (1)

Here δ _i is the δ ¹³ C value of inorganic carbon in the culture solution after cultivating plants for a certain period of time, δ _a is the δ ¹³ C value of carbon dioxide dissolved in the air into the culture solution, and δ _ci is the bicarbonate ion in the initial culture solution δ ¹³ C value of , f _Bi is the proportion of exogenous bicarbonate ions in the culture solution to the total inorganic carbon source in the culture solution after cultivating plants for a certain period of time.

Obviously, δ _ci , δ _i and f _Bi must be known before δ _a can be obtained. Therefore, the present invention uses two kinds of sodium bicarbonate with large difference in δ ¹³ C values as markers to be added respectively in the nutrient solution and at the same time to be tested Cultivate plants with consistent growth in the environment, and use the two-way labeling stable carbon isotope technique to estimate the proportion of labeled bicarbonate ions in the total inorganic carbon in the solution, calculate δ _a from this, and then calculate the daily average stable carbon of atmospheric carbon dioxide based on δ _a isotopic composition.

  For isotope label 1, equation (1) expresses the following formula:

δ ₁ = δ _Ca - f _B1 δ _a + f _B1 δ _C1 (2)

Here δ ₁ is the δ ¹³ C value in the nutrient solution after adding the first sodium bicarbonate with known δ ¹³ C value to the nutrient solution to cultivate plants for a certain period of time, and δ _a is the carbon dioxide in the atmosphere entering the culture solution during this period The average value of inorganic carbon δ ¹³ C in δ 13 C, δ _C1 is the δ ¹³ C value of the first sodium bicarbonate, f _B1 is the percentage of the first exogenous bicarbonate ion added in the culture solution after cultivating plants for a certain period of time share of total inorganic carbon sources.

For isotope label 2, equation (1) is expressed as follows:

δ ₂ = δ _Ca - f _B2 δ _a + f _B2 δ _C2 (3)

Here δ ₂ is the δ ¹³ C value in the nutrient solution after adding the second sodium bicarbonate with known δ ¹³ C value to the nutrient solution to cultivate plants for a certain period of time, and δ _a is the carbon dioxide in the atmosphere entering the culture solution during this period The average value of inorganic carbon δ ¹³ C, δ _C2 is the δ ¹³ C value of the second sodium bicarbonate, f _B2 is the second added exogenous bicarbonate ion in the culture solution after cultivating plants for a certain period of time. share of total inorganic carbon sources.

In the two equations (2) and (3), f _B = f _B1 = f _B2 , (2) and (3) are solved simultaneously

(4)

The f _B value calculated here is the share of the exogenous bicarbonate ions added in the culture solution to the total inorganic carbon source in the culture solution after cultivating plants in the culture solution for a certain period of time.

The f _B value is between 0 and 1. The larger the f _B is, the less carbon dioxide in the air enters the culture solution, and the less carbon dioxide enters the culture solution, it is difficult to accurately measure the carbon dioxide in the atmosphere during this period. Average value of inorganic carbon δ ¹³ C entering the culture medium (δ _a ). The smaller f _B is, the more carbon dioxide in the air enters the culture solution, and the more carbon dioxide enters the culture solution, the more convenient and accurate the measurement of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period is. Mean value (δ _a ). Therefore, we choose to cultivate plants that can quickly utilize bicarbonate ions in order to allow more carbon dioxide in the air to enter the culture solution. Through multiple experiments, it is determined that the critical value of f _B is 0.6. When f _B is less than 0.6, the above data can be brought into equation (5).

 (5)

Therefore, by measuring the δ ¹³ C value δ _C1 of the bicarbonate ion labeled with isotope 1 and the δ ¹³ C value δ _C2 of the bicarbonate ion labeled with isotope 2, the culture medium added with the corresponding labeled bicarbonate ion can be determined simultaneously The value of δ ¹³ C in the solution after cultivating plants for a period of time, i.e. the measured values of δ ₁ and δ ₂ , can calculate the amount of inorganic carbon δ ¹³ C in the atmosphere carbon dioxide entering the culture solution during this period according to the formula (5) Mean δ _a .

Add δ _a to convert it into the average stable carbon isotope composition of atmospheric carbon dioxide δ _Ca . The conversion expression is:

δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} (6)

In (6), δ _Ca is the average stable carbon isotope composition of atmospheric carbon dioxide, and △ _{CO2(air)- HCO3(aq) is} the carbon isotope fractionation value from bicarbonate ion to carbon dioxide under non-equilibrium state. △ _{CO2(air)- HCO3(aq)} is about 8.5‰ in the equilibrium state. Due to the rapid absorption and utilization of plants, the hydrolysis balance of carbon dioxide has been developing towards the direction of generating bicarbonate. Therefore, △ _{CO2(air)- HCO3(aq )} takes 1.1‰.

Detailed ways

Example of the present invention: it comprises the following steps:

First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2;

Second, the tracers of isotope label 1 and isotope label 2 were added to the nutrient solution respectively, the concentration of sodium bicarbonate in the nutrient solution was set to 10 mM, the pH was 8.30, and the bicarbonate ion δ in the nutrient solution of isotope label 1 The value of ¹³ C is δ _C1 , and the value of δ ¹³ C of bicarbonate ion in the nutrient solution labeled with isotope 2 is δ _C2 ;

Thirdly, the above-prepared nutrient solution is used to simultaneously cultivate plants with the same growth cycle in the environment to be tested. After 24 hours of cultivation, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled nutrient solutions are respectively measured, which are recorded as δ ₁ and δ ₂ values;

Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate accounts for the share f _B of the total inorganic carbon in the nutrient solution;

Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained in the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average δ _a of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period;

Sixth, bring the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , that is, δ _Ca = δ _a + 1.1‰. , to calculate the daily average stable carbon isotopic composition δ _Ca of atmospheric carbon dioxide.

Example 1

First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2;

Second, the tracers of isotope label 1 and isotope label 2 were added to the Hoagland nutrient solution respectively. The concentration of sodium bicarbonate in the nutrient solution was set at 10 mM, and the pH was 8.30. The value of δ ¹³ C is δ _C1 , and the value of δ ¹³ C of bicarbonate ion in the nutrient solution labeled with isotope 2 is δ _C2 ;

Thirdly, the above-prepared nutrient solution was simultaneously cultivated with the same growth cycle of Zhuge Cai under the test environment 1. After culturing for 24 hours, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled Hoagland nutrient solutions were measured respectively, Recorded as δ ₁ and δ ₂ values respectively;

Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate accounts for the share f _B of the total inorganic carbon in the nutrient solution;

Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained in the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average δ _a of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period;

Sixth, bring the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , that is, δ _Ca = δ _a + 1.1‰. , to calculate the daily average stable carbon isotopic composition δ _Ca of atmospheric carbon dioxide.

Example 2

First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2;

Second, the tracers of isotope label 1 and isotope label 2 were added to the Hoagland nutrient solution respectively. The concentration of sodium bicarbonate in the nutrient solution was set at 10 mM, and the pH was 8.30. The value of δ ¹³ C is δ _C1 , and the value of δ ¹³ C of bicarbonate ion in the nutrient solution labeled with isotope 2 is δ _C2 ;

Thirdly, culture Brassica napus with the same growth cycle in the nutrient solution prepared above under the environment 2 to be tested. After 24 hours of cultivation, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled Hoagland nutrient solutions were measured respectively. , respectively denoted as δ ₁ and δ ₂ values;

Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate accounts for the share f _B of the total inorganic carbon in the nutrient solution;

Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained in the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average δ _a of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period;

Sixth, bring the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , that is, δ _Ca = δ _a + 1.1‰. , to calculate the daily average stable carbon isotopic composition δ _Ca of atmospheric carbon dioxide.

Example 3

First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2;

Second, the tracers of isotope label 1 and isotope label 2 were added to the Hoagland nutrient solution respectively. The concentration of sodium bicarbonate in the nutrient solution was set at 10 mM, and the pH was 8.30. The value of δ ¹³ C is δ _C1 , and the value of δ ¹³ C of bicarbonate ion in the nutrient solution labeled with isotope 2 is δ _C2 ;

Thirdly, the above-prepared nutrient solution was simultaneously cultivated with the same growth cycle of Zhuge Cai under the test environment 3. After culturing for 24 hours, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled Hoagland nutrient solutions were measured respectively, Recorded as δ ₁ and δ ₂ values respectively;

Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate accounts for the share f _B of the total inorganic carbon in the nutrient solution;

Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained in the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average δ _a of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period;

Sixth, bring the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , that is, δ _Ca = δ _a + 1.1‰. , to calculate the daily average stable carbon isotopic composition δ _Ca of atmospheric carbon dioxide.

Example 4

First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2;

Second, the tracers of isotope label 1 and isotope label 2 were added to the Hoagland nutrient solution respectively. The concentration of sodium bicarbonate in the nutrient solution was set at 10 mM, and the pH was 8.30. The value of δ ¹³ C is δ _C1 , and the value of δ ¹³ C of bicarbonate ion in the nutrient solution labeled with isotope 2 is δ _C2 ;

Thirdly, the above-prepared nutrient solution was simultaneously cultivated with the same growth cycle of Zhuge Cai under the test environment 4. After culturing for 24 hours, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled Hoagland nutrient solutions were measured respectively, Recorded as δ ₁ and δ ₂ values respectively;

Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate accounts for the share f _B of the total inorganic carbon in the nutrient solution;

Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained by the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average δ _a of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period;

Sixth, bring the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , that is, δ _Ca = δ _a + 1.1‰. , to calculate the daily average stable carbon isotopic composition δ _Ca of atmospheric carbon dioxide.

Example 5

First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2;

Second, the tracers of isotope label 1 and isotope label 2 were added to the Hoagland nutrient solution respectively. The concentration of sodium bicarbonate in the nutrient solution was set at 10 mM, and the pH was 8.30. The value of δ ¹³ C is δ _C1 , and the value of δ ¹³ C of bicarbonate ion in the nutrient solution labeled with isotope 2 is δ _C2 ;

Thirdly, culture Brassica napus with the same growth cycle in the nutrient solution prepared above under the test environment 5. After culturing for 24 hours, measure the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled Hoagland nutrient solutions respectively , respectively denoted as δ ₁ and δ ₂ values;

Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate accounts for the share f _B of the total inorganic carbon in the nutrient solution;

Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained in the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average δ _a of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period;

Sixth, bring the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , that is, δ _Ca = δ _a + 1.1‰. , to calculate the daily average stable carbon isotopic composition δ _Ca of atmospheric carbon dioxide.

Example 6

First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2;

Second, the tracers of isotope label 1 and isotope label 2 were added to the Hoagland nutrient solution respectively. The concentration of sodium bicarbonate in the nutrient solution was set at 10 mM, and the pH was 8.30. The value of δ ¹³ C is δ _C1 , and the value of δ ¹³ C of bicarbonate ion in the nutrient solution labeled with isotope 2 is δ _C2 ;

Thirdly, the above-prepared nutrient solution was used to simultaneously cultivate Brassica napus with the same growth cycle under the test environment 6, and after 24 hours of cultivation, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled Hoagland nutrient solutions were respectively measured , respectively denoted as δ ₁ and δ ₂ values;

Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate accounts for the share f _B of the total inorganic carbon in the nutrient solution;

Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained by the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average δ _a of the inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during this period;

Sixth, bring the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , that is, δ _Ca = δ _a + 1.1‰. , to calculate the daily average stable carbon isotopic composition δ _Ca of atmospheric carbon dioxide.

Implementation effect of the present invention is as follows:

Sodium bicarbonate with δ ¹³ C of -28.87‰ and -1.53‰ (PDB) was added to the improved Hoagland nutrient solution to prepare isotope-labeled 1 nutrient solution and isotope-labeled 2 nutrient solution. Sow the seeds of Zhugecai and mustard-type rapeseed on the hole tray, and after the two plants germinate and grow to 4 true leaves, use isotope-labeled 1 culture solution and isotope-labeled 2 nutrient solution respectively to cultivate Zhugecai and mustard-type rapeseed with the same growth. rape. After culturing for 24 hours, the carbon isotope δ ¹³ C values of the nutrient solutions corresponding to the two isotope labels were measured respectively. The bicarbonate ion added in the nutrient solution accounted for the share f _B of the total inorganic carbon source in the nutrient solution after the method of the present invention was investigated to cultivate the plants for 24 hours, and finally the atmospheric carbon dioxide daily average stable carbon isotope composition δ _Ca was calculated, as shown in the following table shown (Table 1).

It can be seen from Table 1 that the daily average stable carbon isotope composition of atmospheric carbon dioxide in the 6 different environments to be measured is significantly different, and the environment 1 to be measured is least affected by human activities, so its daily average stable carbon isotope composition of atmospheric carbon dioxide is close to Atmospheric CO ₂ carbon isotope δ ¹³ C average value (≈-8 ‰), the test environment 2 is more affected by human activities than the test environment 1 is smaller than the test environment 3,4,5,6, so its atmospheric carbon dioxide daily The average stable carbon isotope composition is less than the average value of atmospheric CO ₂ carbon isotope δ ¹³ C (≈-8 ‰), which is -11.30‰. Test environment 3 and test environment 4 are the same environment, and the daily average stable carbon isotope composition of atmospheric carbon dioxide measured is not much different, which are -14.80‰ and -15.43‰ respectively; test environment 5 and test environment 6 are also the same Environment, the measured daily average stable carbon isotope composition values of atmospheric carbon dioxide are very close, which are -14.59‰ and -14.55‰ respectively. The environments 3, 4, 5, and 6 to be tested are greatly affected by human activities, and human respiration causes their daily average stable carbon isotope composition values of atmospheric carbon dioxide to be more negative than the average value of atmospheric CO ₂ carbon isotope δ ¹³ C. These results are in line with reality.

It can be seen from the above data that it is reliable to use the present invention to obtain the daily average stable carbon isotope composition of atmospheric carbon dioxide in different environments. The invention establishes an effective method to obtain the daily average stable carbon isotope composition of atmospheric carbon dioxide, the experimental process is simple, and the change of stable carbon isotope composition of atmospheric carbon dioxide under different environments can be detected, which is convenient and quick.

Claims (1)

1. A method for measuring atmospheric carbon dioxide daily average stable carbon isotope composition, characterized in that: First, determine the sodium bicarbonate produced by different manufacturers, and select two kinds of sodium bicarbonate whose δ ¹³ C value difference is greater than 10‰ as tracers for isotope label 1 and isotope label 2; Second, add them to the nutrient solution respectively. The concentration of sodium bicarbonate in the nutrient solution is set to 10 mM, the pH is 8.30, the δ ¹³ C value of the bicarbonate ion in the solution of isotope label 1 is δ _C1 , and the value of isotope label 2 is δ C1 . The hydrogen carbonate ion δ ¹³ C value in the solution is δ _C2 ; Thirdly, the above-prepared solutions are used to simultaneously cultivate plants with consistent growth cycles. After culturing for 24 hours, the stable carbon isotope composition δ ¹³ C values in the two isotope-labeled nutrient solutions are measured respectively, which are δ ₁ and δ ₂ values; Fourth, put the measured values of δ _C1 , δ _C2 , δ ₁ and δ ₂ into the equation , calculate the added sodium bicarbonate to account for the share f _B of the total inorganic carbon in the solution; Fifth, judge whether the f _B value is less than 0.6, take the measured values obtained in the experiment when the f _B value is less than 0.60, and bring them into the equation , calculate the average value of inorganic carbon δ ¹³ C of carbon dioxide in the atmosphere entering the culture solution during the period of δ _a ; Sixth, put the calculated δ _a value into the equation δ _Ca = δ _a + △ _{CO2(air)- HCO3(aq)} , and take the value of △CO ₂ (air)- HCO ₃ (aq) as 1.1‰ to calculate the atmospheric The daily average stable carbon isotopic composition of carbon dioxide δ _Ca .