CN102590457A - Method for identifying stable carbon isotope composition of isoprene in atmosphere - Google Patents

Abstract

The invention discloses a method for determining stable carbon isotope composition of isoprene in atmosphere, comprising the following steps: step I: determining the stable carbon isotope composition of 2-methyl butantetraol in aerosol; step B: determining an isotopic fractionation constant of 2-methyl butantetraol generated by isoprene through photochemical reaction; and step C: calculating the stable carbon isotope composition of the isoprene in the atmosphere. The method can be used for analyzing a source of the isoprene in the atmosphere, discussing a migration and transfer rule, and researching and exploring distribution of vegetations (C3, C4 and CAM) with different photosynthesis types in an environment. The method solves the difficult problem that the stable carbon isotope composition of the active volatile organic compound in the atmosphere is hard to determine accurately and establishes a method foundation for explaining generation, migration, transfer and trend rules of the isoprene in nature.

Description

Identify the method that atmosphere isoprene stable carbon isotope is formed

Technical field

The present invention relates to a kind of method of identifying that atmosphere isoprene stable carbon isotope is formed, belong to the environmental monitoring technology field.

Background technology

Isoprene is a non-methane hydrocarbon important in the ambient atmosphere, and it is easy to and OH, O ₃, NOx reacts, and is the important as precursors thing that ozone generates, thereby influence the oxidation characteristic of atmosphere.2-methyl butantetraol is the molecular marker of isoprene atmosphere photooxidation reaction.The δ that adopts methyl-boric acid derivant stable carbon isotope analytical approach to measure 2-methyl butantetraol in the varying environment gasoloid is intended in this research ¹³C forms, according to the δ of 2-methyl butantetraol ¹³C information is further inquired into the δ of its precursor isoprene ¹³C forms, and this method can be used for the origin analysis of zones of different atmosphere isoprene and the discussion that the isoprene aerial migration is shifted to new management mechanisms.

The source of isoprene is complicated, and natural origin and artificial source are arranged.It is the most important source of atmosphere isoprene that plant discharges, and the volatilization total amount is about 500Tg C/Yr.In addition, the isoprene of soil and atmosphere exchange estimates at 20TgC/Yr; The isoprene of ocean volatilization has 1TgC/Yr approximately; Animal, plant, microorganism decomposition, human body respiration, chemical industry, smoking, doughnut, trash burning etc. also can produce isoprene.Rudolph etc. and Iannone etc. have set up one and have been directed to the analytical approach that atmosphere isoprene stable carbon isotope is measured; Sample through the atmospheric sampling jar; Pre-concentration sample introduction, GC/C/IRMS analytical technology; They have measured the stable carbon isotope composition of isoprene in several ambient atmosphere samples, and the distribution range of its value is-29 ‰ to-16 ‰.

Gas chromatography/burning/isotope ratio mass-spectrometric technique (gas chromatography/combustion/isotope ratio mass spectrometry; GC/C/IRMS) be a kind of separation of carbon compound and analytical approach that stable carbon isotope is measured of being widely used in; Free carbon isotope analysis (compound-specific isotope analysis; CSIA) become an effective instrument; Be applied to organic stable carbon isotope composition analysis under the varying environment system, for we understand in depth this organism in the source of occurring in nature, distribute and return and become to establishing scientific basic.Directly measure the stable carbon isotope of atmosphere isoprene and form a kind of method and the approach that the exploration atmosphere isoprene of can yet be regarded as is originated and moved transformation rule in surrounding air.

But because isoprene has very high reactivity in atmosphere, the isoprene stable carbon isotope is formed relevant with its volatile source and the RT of isoprene in atmosphere in the ambient atmosphere.Rudolph etc. [1] propose to form according to the stable carbon isotope of isoprene and calculate its degradation time in atmosphere, and its concrete computing formula is following:

δ _z＝(t _av ^*OHk ₁₂*[OH] _av) ^*OH _iε _KIE+ ⁰δ _z (1)

According to (1), by the mensuration δ of isoprene ¹³C forms (δ _z) with the δ in its source ¹³The C composition ( ⁰δ _z), OH and isoprene atmospheric reaction speed ( ^OH _ik ₁₂), isotope fractionation (Kinetic isotope effect, the KIE) coefficient of isoprene and OH reaction ^OH _iε _KIEAnd average OH concentration ([OH] in the atmosphere _Av), can calculate and confirm the actual residence time of isoprene in atmosphere, also be the atmosphere degradation time (t of isoprene _Av).

Directly measure the stable carbon isotope of atmosphere isoprene and form, thereby judge that its source and degraded go through the footpath, exists three bottleneck difficult problems culverts to be solved: the one, the RT of isoprene in atmosphere is limited; Reaction velocity is very fast; In the limited transmission time, the distance of transmission is also limited, therefore; The isoprene of test determination must be the isoprene that produces in the certain limit, can't form from the main source of judgement this area isoprene in the big zone; The 2nd, isoprene gets into atmosphere certainly and in transmission course, isotopics constantly change, δ ¹³The variation of C value will cause making more accurately its source infers; The 3rd, measuring the isotopics of atmosphere isoprene needs expensive low temperature pre-concentration sample introduction equipment, and the method difficulty is high.Above-mentioned many reasons, the certain degree limit directly differentiate isoprene source The Application of Technology through the free carbon isotope technology.

Summary of the invention

Technical matters to be solved by this invention is that the deficiency that is directed against prior art provides a kind of method of identifying that atmosphere isoprene stable carbon isotope is formed; Stable carbon isotope through measuring gasoloid phase 2-methyl butantetraol is formed, and the stable carbon isotope of indirect determination atmosphere isoprene is formed.

A kind of method of identifying that atmosphere isoprene stable carbon isotope is formed may further comprise the steps:

Steps A: the stable carbon isotope composition measuring of 2-methyl butantetraol in the gasoloid;

Step B: the isoprene photochemical reaction generates the isotope fractionation constant measuring of 2-methyl butantetraol;

Step C: the calculating of the stable carbon isotope value of ambient atmosphere isoprene;

Described method, the assay method of said steps A is:

The collection of A1, environment aerosol particle thing sample;

The extraction of A2, particle sample Semi-polarity material;

A3, methyl-boric acid derivative reaction;

A4, GC/C/IRMS measure the δ of 2-methyl butantetraol methyl boron acid esters ¹³The C value;

A5, calculate the stable carbon isotope that obtains 2-methyl butantetraol according to the stable carbon isotope value of the stable carbon isotope value of the 2-methyl butantetraol methyl boron acid esters of measuring and known methyl-boric acid and form.

Described method, the assay method of said step B is:

B1, laboratory photochemical reaction: get 5～10ml isoprene solution and evenly mix, add 1M H with the hydrogen peroxide solution of different amounts ₂SO ₄1～2, regulating the pH value is 1～2; Under strong sunlight, carry out stirring reaction, reaction time 1～6h does not wait;

B2, reactant liquor dry up under soft nitrogen; Add methyl-boric acid and carry out derivative reaction; Inject GC/C/IRMS subsequently and measure the wherein stable carbon isotope composition of 2-methyl butantetraol methyl boron acid esters, and push back the stable carbon isotope composition that calculates 2-methyl butantetraol;

The stable carbon isotope of B3, isoprene is measured and is adopted headspace sampling-GC/C/IRMS method for measuring to measure its stable carbon isotope composition;

B4, form and the Changing Pattern of the stable carbon isotope composition value of product 2-methyl butantetraol, confirm the photochemically reactive KIE constant of isoprene according to the stable carbon isotope of reactant isoprene.

Described method, the assay method of said step C is:

C1, in Atmospheric particulates samplings, use the photosynthetically active radiation appearance to measure the photosynthetically active radiation value on the same day, and use atmospherium to measure the variation of the environment weather factors such as environment temperature, relative humidity, wind speed, wind direction;

C2, sample area are mainly discharged the affirmation of isoprene seeds drainage rate and draining period;

C3, the estimation of different survey region discharging isoprene phytomass.

C4, according to survey region isoprene volatile quantity during the Guenther light warm therapy calculating sampling;

C5, form value, calculate the stable carbon isotope that obtains regional implants discharging isoprene and form by the stable carbon isotope of 2-methyl butantetraol in the photochemically reactive KIE constant of known isoprene, survey region isoprene volatile quantity and the gasoloid.

2-methyl butantetraol is a kind of Secondary Organic thing that in the ambient atmosphere particle, monitors at present.It has the parent carbon-chain structure identical with isoprene, and the atmosphere photooxidation reaction that its formation mechanism is isoprene generates through heterogeneous delivering path and the middle mutually hydrogen peroxide oxidation reaction of particle with isoprene and oxidation product thereof.2-methyl butantetraol is a kind of organic mark of gasoloid of extensive existence, is the molecular marker of isoprene photooxidation reaction product.This research is attempted from measuring the molecular marker of isoprene photo-oxidation product---and the stable carbon isotope composition of 2-methyl butantetraol is started with; Form from the stable carbon isotope of measuring the 2-methyl butantetraol that obtains; The counter stable carbon isotope of calculating the atmosphere isoprene that pushes away is formed, thereby realizes seeking migration transformation rule in its source and the environment.

Description of drawings

Fig. 1 is the technology path figure of the inventive method;

Fig. 2 is the photochemically reactive KIE constant calculations of an isoprene flow process;

Fig. 3 is the calculation process of survey region isoprene volatile quantity E.

Embodiment

Below in conjunction with specific embodiment, the present invention is elaborated.

With reference to the technology path figure of figure 1 the inventive method, identify the method that atmosphere isoprene stable carbon isotope is formed, may further comprise the steps A-step C.

Steps A: the stable carbon isotope composition measuring of 2-methyl butantetraol in the gasoloid;

The collection of A1, environment aerosol particle thing sample;

The extraction of A2, particle sample Semi-polarity material;

A3, methyl-boric acid derivative reaction;

A4, GC/C/IRMS measure the δ of 2-methyl butantetraol methyl boron acid esters ¹³The C value;

A5, calculate the stable carbon isotope that obtains 2-methyl butantetraol according to the stable carbon isotope value of the stable carbon isotope value of the 2-methyl butantetraol methyl boron acid esters of measuring and known methyl-boric acid and form.

Its concrete computing formula is following:

δ ¹³C _boronate＝f _MBAδ ¹³C _MBA+f _2MTsδ ¹³C _2MTs (2)

In the following formula, f _MBA, f _2MTsBe respectively in the derivative products ratio that accounts for the total number of carbon atoms in the product borate molecule from the carbon number of methyl-boric acid and 2-methyl butantetraol.In 2-methyl butantetraol derivative reaction, f _MBA=2/7, f _2MTs=5/7.

Step B: the isoprene photochemical reaction generates the isotope fractionation constant (KIE constant) of 2-methyl butantetraol and measures;

B1, laboratory photochemical reaction: get 5～10ml isoprene solution and evenly mix, add 1M H with the hydrogen peroxide solution of different amounts ₂SO ₄1～2, regulating the pH value is 1～2; Under strong sunlight, carry out stirring reaction, reaction time 1～6h does not wait.

B2, reactant liquor dry up under soft nitrogen; Add methyl-boric acid and carry out derivative reaction; Inject GC/C/IRMS afterwards and measure the wherein stable carbon isotope composition of 2-methyl butantetraol methyl boron acid esters; And the stable carbon isotope that pushes back calculating 2-methyl butantetraol is formed the same A5 of concrete computation process.

The stable carbon isotope of B3, isoprene is measured and is adopted headspace sampling-GC/C/IRMS method for measuring to measure its stable carbon isotope composition.

B4, form and the Changing Pattern of the stable carbon isotope composition value of product 2-methyl butantetraol, confirm the photochemically reactive KIE constant of isoprene (seeing accompanying drawing 2) according to the stable carbon isotope of reactant isoprene.

Particularly,

${\mathrm{\δ}}_{2\mathrm{MTs}}-{\mathrm{\δ}}_{\mathrm{isoprene}}{=}^{\mathrm{OH}}{\mathrm{\δ}}_{\mathrm{KIE}}\mathrm{In}\frac{P_i}{P_0}{=}^{\mathrm{OH}}{\mathrm{\δ}}_{\mathrm{KIE}}\mathrm{In}\frac{P^{*}}{P_0}{+}^{\mathrm{OH}}{\mathrm{\δ}}_{\mathrm{KIE}}\mathrm{Inx}---\left(3\right)$

In the following formula, ^OHδ _KIEBe the photochemically reactive isotopic power effect of isoprene OH constant (KIE constant); δ _2MTsAnd δ _IsopreneBe respectively the photooxidation reaction δ of 2-methyl butantetraol afterwards ¹³The δ of isoprene before C value and the reaction ¹³The C value; P _i, P ₀The equilibrium partial pressure of unreacted isoprene in gas phase when being respectively reaction beginning, reaction end.

P ^*Definite formula following:

$\frac{P_i\×V_g}{\mathrm{RT}}+\frac{P_i}{101325}\×H_i\×V_l=N_{\mathrm{isoprene}}\×x---\left(4\right)$

In the following formula, V _gAnd V _l(unit is: m to be respectively the volume of gas and solution in the reaction bulb ³); T is a temperature of reaction; H _iHenry's constant for isoprene; N _IsopreneFor participating in the molal quantity of the isoprene that reacts, x reacts when finishing the residual rate of isoprene.

Step C: the calculating of the stable carbon isotope value of ambient atmosphere isoprene;

C1, in Atmospheric particulates samplings, use the photosynthetically active radiation appearance to measure the photosynthetically active radiation value on the same day, and use atmospherium to measure the variation of the environment weather factors such as environment temperature, relative humidity, wind speed, wind direction;

C2, sample area are mainly discharged the affirmation of isoprene seeds drainage rate and draining period;

C3, the estimation of different survey region discharging isoprene phytomass;

At first adopt distribution kind, the quantity of main discharging isoprene seeds in the quadrat method investigation zone; Calculate total biomasss of this kind trees in the whole sample prescription according to the leaf leaf quality of typical sizes trees, finally gather total biomass of the trees of volatilization isoprene in the sample prescription.

According to remote sensing photo and ArcGIS software analysis; Confirm survey region different vegetation types area; And combine different types vegetation sample prescription data measured to calculate the biological total amount of discharging isoprene in the sample prescription, finally gather the biological total amount of calculating discharging isoprene vegetation in the whole zone.

C4, according to survey region isoprene volatile quantity E during the Guenther light warm therapy calculating sampling;

Calculation process is seen accompanying drawing 3, specifically has:

$E=\underset{i}{\mathrm{\Σ}}{E}_i=\underset{i}{\mathrm{\Σ}}{E}_{0i}\·{\mathrm{\δ}}_i\·{\mathrm{\γ}}_i\·B_{\mathrm{li}}---\left(5\right)$

In the formula, E _iIsoprene discharge capacity for the i seeds; E _OiBe standard temperature (T=303K) and etalon optical power (PAR=1000 μ mol (m ²S) ^-1Down, i seeds isoprene drainage rate, unit are μ g (gh) ^-1γ is the discharging active factors, and it is Ye Wen (unit K) and photosynthetically active radiation (PPFD, the μ mol (m of unit ²S) ^-1) function.B _LiBe leaf biomass, δ _iBe to consider the active control variable of long-term discharging.

The computing formula of γ value is following:

$\mathrm{\γ}=C_L{C}_T=\left(\frac{\mathrm{\α}{c}_{L1}L}{\sqrt{1+{\mathrm{\α}}^2{L}^2}}\right)\left(\frac{\exp \left(\frac{c_{T1}(T-T_s)}{{\mathrm{RT}}_{s}T}\right)}{1+\exp \left(\frac{c_{T2}(T-T_M)}{{\mathrm{RT}}_{s}T}\right)}\right)---\left(6\right)$

In the following formula, T _sBe the Ye Wen under the standard conditions, be 300K; T is the leaf temperature, and unit is K.α＝0.0027，c _L1＝1.066；c _T1＝95000J·mol ^-1，C _T2＝2300J·mol ^-1，T _M＝314K。This is the experience factor that is the basis with 3 kind of plant (eucalyptus, white poplar, soybean) measurement result.Research shows that these constants can be widely used in various plant.

δ _iValue calculate by formula (7):

$\mathrm{\&delta;}=\left(\begin{array}{cc}0,& J<J_0,J>(J_0+J_D);\\ \sin (J-J_0)/J_D,& J_0\&le;J\&le;(J_0+J_D).\end{array}\right)---\left(7\right)$

Wherein, on behalf of discharge capacity, J calculate the same day, J ₀It is row's date beginning of plant isoprene in the middle of a year; J _DIt is the discharging fate of plant isoprene in the middle of a year.

C5, by the photochemically reactive KIE constant of known isoprene ^OHδ _KIE, (survey region isoprene volatile quantity on average volatilizees total amount C in the daytime _Iso, minimum volatile quantity C of time-division at dusk _{0, iso}) and the gasoloid of above mensuration in the stable carbon isotope of 2-methyl butantetraol form (δ _2-MTs) stable carbon isotope that calculate to obtain regional implants discharging isoprene forms δ _Isoprene

Particularly,

${\mathrm{\&delta;}}_{2\mathrm{MTs}}-{\mathrm{\&delta;}}_{\mathrm{isoprene}}{=}^{\mathrm{OH}}{\mathrm{\&delta;}}_{\mathrm{KIE}}\mathrm{In}\frac{C_{0,\mathrm{iso}}}{C_{\mathrm{iso}}}---\left(8\right)$

In the following formula, δ _2MTs, ^OHδ _KIE, C _{0, iso}, C _IsoNumerical value all can obtain through experiment, according to known δ _2MTs, ^OH,δ _KIE, C _{0, iso}, C _Iso, can calculate the stable carbon isotope composition value δ that obtains local isoprene discharging _Isoprene

Should be understood that, concerning those of ordinary skills, can improve or conversion, and all these improvement and conversion all should belong to the protection domain of accompanying claims of the present invention according to above-mentioned explanation.

Claims (4)

1. a method of identifying that atmosphere isoprene stable carbon isotope is formed is characterized in that, may further comprise the steps: steps A: the stable carbon isotope composition measuring of 2-methyl butantetraol in the gasoloid;

Step B: the isoprene photochemical reaction generates the isotope fractionation constant measuring of 2-methyl butantetraol;

Step C: the calculating of the stable carbon isotope value of ambient atmosphere isoprene.

2. method according to claim 1 is characterized in that, the assay method of said steps A is:

The collection of A1, environment aerosol particle thing sample;

The extraction of A2, particle sample Semi-polarity material;

A3, methyl-boric acid derivative reaction;

A4, GC/C/IRMS measure the δ of 2-methyl butantetraol methyl boron acid esters ¹³The C value;

A5, calculate the stable carbon isotope that obtains 2-methyl butantetraol according to the stable carbon isotope value of the stable carbon isotope value of the 2-methyl butantetraol methyl boron acid esters of measuring and known methyl-boric acid and form.

3. method according to claim 1 is characterized in that, the assay method of said step B is:

B1, laboratory photochemical reaction: get 5～10ml isoprene solution and evenly mix, add 1M H with the hydrogen peroxide solution of different amounts ₂SO ₄1～2, regulating the pH value is 1～2; Under strong sunlight, carry out stirring reaction, reaction time 1～6h does not wait;

B2, reactant liquor dry up under soft nitrogen; Add methyl-boric acid and carry out derivative reaction; Inject GC/C/IRMS subsequently and measure the wherein stable carbon isotope composition of 2-methyl butantetraol methyl boron acid esters, and push back the stable carbon isotope composition that calculates 2-methyl butantetraol;

The stable carbon isotope of B3, isoprene is measured and is adopted headspace sampling-GC/C/IRMS method for measuring to measure its stable carbon isotope composition;

B4, form and the Changing Pattern of the stable carbon isotope composition value of product 2-methyl butantetraol, confirm the photochemically reactive KIE constant of isoprene according to the stable carbon isotope of reactant isoprene.

4. method according to claim 1 is characterized in that, the assay method of said step C is:

C1, in Atmospheric particulates samplings, use the photosynthetically active radiation appearance to measure the photosynthetically active radiation value on the same day, and use atmospherium to measure the variation of the environment weather factors such as environment temperature, relative humidity, wind speed, wind direction;

C2, sample area are mainly discharged the affirmation of isoprene seeds drainage rate and draining period;

C3, the estimation of different survey region discharging isoprene phytomass;

C4, according to survey region isoprene volatile quantity during the Guenther light warm therapy calculating sampling;

C5, form value, calculate the stable carbon isotope that obtains regional implants discharging isoprene and form by the stable carbon isotope of 2-methyl butantetraol in the photochemically reactive KIE constant of known isoprene, survey region isoprene volatile quantity and the gasoloid.

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