CN116298030A - Method for detecting and estimating atmospheric organic nitrate aerosol - Google Patents

Abstract

The invention provides a detection and estimation method of an atmospheric organic nitrate aerosol, which comprises the following steps: continuously observing organic and inorganic components of the atmospheric non-refractory submicron-level aerosol by using an aerosol mass spectrometer to obtain a concentration time sequence of an organic ion fragment mass spectrum and an inorganic ion fragment; binding NO ⁺ 、NO ₂ ⁺ Time series of mass spectra of fragments and organic ion fragments to establish a mass spectrum containing NO ⁺ 、NO ₂ ⁺ ORG of fragments _NOx A matrix; fixed by NO only ⁺ And NO ₂ ⁺ Inorganic nitrate mass spectrum composed of fragments; ORG pairs using positive definite matrix factor analysis _NOx Analyzing the matrix to obtain a matrix with a predetermined ratio of NO ⁺ And NO ₂ ⁺ INA factor representing inorganic nitrate formed by fragments, and a plurality of independent sources representing different OA emissions and containing NO ⁺ 、NO ₂ ⁺ The OA factor of the fragments; using the concentration of each OA factor and NO in the mass spectrum ⁺ And NO ₂ ⁺ Calculating the ratio of the ion fragments to obtain the concentration of organic nitrate groups; thus, the accuracy of the analysis result of the concentration of the atmospheric organic nitrate can be improved.

Description

Method for detecting and estimating atmospheric organic nitrate aerosol

Technical Field

The invention relates to the technical field of environmental science and protection, in particular to a detection and estimation method of an atmospheric organic nitrate aerosol.

Background

With the implementation of various environmental protection policies, the pollution degree of the atmospheric fine particulate matters in China is continuously lightened in recent years, but the improvement of the pollution problem of the fine particulate matters is still a great challenge in the field of environmental science. The atmospheric fine particles mainly consist of inorganic salts (nitrate, sulfate, ammonium salt, etc.) and organic components, etc., and the nitrate, sulfate, ammonium salt particles are also called secondary inorganic aerosol (SNA), are NO _x 、SO ₂ 、NH ₃ Secondary generation of contaminants from the gaseous precursor; among the Organic Aerosols (OA), there are Secondary Organic Aerosols (SOA) generated through physicochemical processes such as atmospheric oxidation reaction, condensation, coalescence, etc., in addition to Primary Organic Aerosols (POA) directly discharged from pollution sources. Rapid increases in SNA and SOA concentrations are often observed in heavy haze events, with SOAs accounting for up to 90% of OA. The production of SOA is also subject to atmospheric oxidising properties, atmospheric humidity, gaseous pollutants such as NO _x And SNA particulate seeds, which can also generate a plurality of sulfur-containing and nitrogen-containing species during the generation and aging processes, the mechanism has great complexity.

In many urban areas where motor vehicles are active, NO _x The pollution degree with organic gaseous pollutants is serious, and the pollutants interact with each other under illumination, thereby causing SOA and O ₃ Secondary pollution, etc. NO in atmosphere _x Or NO ₃ The precursor such as free radical and the oxidant, when involved in the generation and aging of the SOA, generate organic nitrate (RONO ₂ ) And organic peroxynitrate (RO) ₂ NO ₂ ) Such as Peracetylnitrate (PAN). The contribution of the granular organic nitrogen substances pON (particulate Organic Nitrate) to OA can reach 5% -77%, and massive generation of nitrogen-containing organic substances is observed in heavy haze days in many cities in China. pON is also atmospheric nitroxideImportant sinks of the compounds play a non-negligible role in the circulation of nitrogen oxides; nitrogen-containing organics, also an important component of atmospheric brown carbon (BrC), can have a significant impact on the optical properties of aerosols and the atmospheric radiation balance, further affecting regional as well as global climate. Therefore, detection and quantification of nitrogen-containing organic matters in the atmosphere are of great value for comprehensive understanding of the composition of organic aerosols and deep investigation of the mechanism of secondary organic aerosol generation.

Currently, for organic nitrate groups NO in pON material _{3 organic matter} The more common methods include: directly measured by thermal dissociation laser induced fluorescence spectrum or thermal eroder aerosol mass spectrometer, or ionized into NO by inorganic nitrate and organic nitrate in High Resolution Time-of-flight aerosol mass spectrometer (High-Resolution Time-of-Flight Aerosol Mass Spectrometer, HR-ToF-AMS) ⁺ And NO ₂ ⁺ The difference of the fragment ratio to estimate the organic nitrate ratio or the NO observed by AMS ⁺ And NO ₂ ⁺ Fragments were added to the organic component mass spectrum and then analyzed for inorganic and organic nitrates using positive matrix factorial analysis (PMF). The latter two methods are simple and convenient, have high detection time resolution for organic nitrate, and can be used for further analyzing the generation and change of the organic nitrate, but the two methods have certain uncertainty for the estimation and analysis of the organic nitrate. For example, PMF methods often involve NO in the inorganic nitrate factor when resolving nitrogen-containing organic factors and inorganic nitrate factors ⁺ /NO ₂ ⁺ Fragment ratio and NO after pure nitrate is broken up in AMS ⁺ /NO ₂ ⁺ Under the condition of different fragment proportions, a small part of organic matter fragments remain in the inorganic nitrate factor, so that the distinction and analysis of organic and inorganic nitrate are greatly deviated, and the result of the concentration of the organic nitrate is inaccurate.

Disclosure of Invention

In order to solve the technical problems, the invention provides a detection and estimation method of an atmospheric organic nitrate aerosol, which can improveThe accuracy of the analysis result of the concentration of the atmospheric organic nitrate helps us to know the pollution degree of the atmospheric organic nitrate and the high time resolution change process of the atmospheric organic nitrate in heavy pollution days more clearly, and to explore the generation and aging mechanism of the nitrogen-containing organic aerosol, the organic precursor and NO deeply _x And the influence and action among inorganic pollutants.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

the invention provides a detection and estimation method of an atmospheric organic nitrate aerosol, which comprises the following steps:

s1, continuously observing organic components and inorganic components of an atmospheric non-refractory submicron-level aerosol by using an aerosol mass spectrometer AMS to obtain a high-resolution organic ion fragment mass spectrum concentration time sequence and an inorganic ion fragment concentration time sequence;

s2 binding to NO ⁺ 、NO ₂ ⁺ Time series of ion fragments and organic ion fragment mass spectra to establish a mass spectrum containing NO ⁺ 、NO ₂ ⁺ The organic ion fragment concentration matrix of the ion fragments is ORG _NOx A matrix;

s3, setting a fixed inorganic nitrate mass spectrum which is only composed of NO ⁺ And NO ₂ ⁺ Ion fragments are formed and fixed in proportion;

s4 PMF-to-ORG analysis Using positive definite matrix factor _NOx Analyzing the matrix to obtain a matrix with a predetermined ratio of NO ⁺ And NO ₂ ⁺ INA factor representing inorganic nitrate formed by fragments, and several independent sources representing different OA emissions and containing small amounts of NO ⁺ 、NO ₂ ⁺ The OA factor of the fragments;

s5 utilizing the concentration of each OA factor obtained in the step S4 and NO in the mass spectrum thereof ⁺ And NO ₂ ⁺ Calculating the ratio of the ion fragments to obtain the organic nitrate radical NO _{3 organic matter} Is a concentration of (3).

The invention provides a detection and estimation method of an atmospheric organic nitrate aerosol, which can improve the accuracy of an atmospheric organic nitrate concentration analysis resultThereby helping us to know the pollution degree of the atmospheric organic nitrate and the high time resolution change process of the atmospheric organic nitrate in heavy pollution days more clearly and to explore the generation and aging mechanism of the nitrogen-containing organic aerosol, the organic precursor and NO deeply _x And the influence and action among inorganic pollutants.

As a preferred embodiment, the ORG established in step S2 _NOx The matrix (t×m) has t rows, t is the total number of data points, namely the total observation time, ORG _NOx NO observed from each row of the matrix at the time corresponding to that row ⁺ 、NO ₂ ⁺ Ion fragments and the concentration of m-2 organic ion fragments with different mass-to-charge ratios.

As a preferable embodiment, NO in the inorganic nitrate mass spectrum set in step S3 ⁺ And NO ₂ ⁺ The ratio of the ion fragments is 2.3-2.5.

As a preferred embodiment, in step S4, the positive definite matrix factor analysis method PMF versus ORG is used _NOx Analyzing the matrix to obtain a matrix with a predetermined ratio of NO ⁺ And NO ₂ ⁺ INA factor representing inorganic nitrate formed by fragments, and several independent sources representing different OA emissions and containing small amounts of NO ⁺ 、NO ₂ ⁺ The OA factor of the fragments specifically comprises the following steps:

s401 building ORG _NOx A two-dimensional bilinear model of the matrix and limiting mass spectra of INA factors representing inorganic nitrates in the mass spectrum matrix of the model;

s402, carrying out weighted least square analysis on the model established in the step S401, enabling the square sum Q value of weighted residual errors to be smaller through continuous iteration, and when the Q value reaches the minimum, ORG _NOx All elements in the matrix conform to their expected errors to obtain an expected value Q of the Q value _exp A value;

s403 artificially selecting the total number of factors P by using the Q value and Q _exp And (3) evaluating the quality of the PMF analysis result by the positive definite matrix factor analysis method by the ratio of the values to finally obtain 1 inorganic nitrate INA factor, P-1 OA factor, a mass spectrum matrix and a concentration time sequence matrix.

As a preferable embodiment, step S401 contains NO ⁺ 、NO ₂ ⁺ Organic ion fragment concentration matrix ORG of ion fragments _NOx Is:

ORG _NOx ＝TS _NOx ×MS _NOx +E _NOx

TS in the above equation _NOx The matrix (t multiplied by p) is formed by a concentration time sequence of 1 inorganic nitrate I NA factor and p-1 OA factors, and t is the total number of data points, namely the total observation time; MS (MS) _NOx The matrix (p×m) consists of mass spectra of 1 inorganic nitrate factor I NA and p-1 OA factors; e (E) _NOx The matrix (t×m) is a residual matrix; ORG (optical fiber glass) _NOx Each element org in the matrix _ij Is composed of:

org in the above formula _ij Is ORG _NOx The elements of row i, column j of the matrix, i.e. the observed mass concentration of ion fragments j at time i, include NO ⁺ 、NO ₂ ⁺ Fragments and all organic ion fragments; ts _ip For a matrix TS _NOx The elements in the ith row and the p th column, namely the mass concentration of a given factor p at time I, comprise inorganic nitrate INA factors and other OA factors; ms of _pj For matrix MS _NOx The p-th row, j-th column elements of (i.e. the ratio of ion fragments j in all ion fragments in mass spectrum given a factor p), including NO ⁺ 、NO ₂ ⁺ Fragments and all organic ion fragments, including inorganic nitrate ina factor and other OA factors; e, e _ij For matrix E _NOx The elements of the ith row and the jth column, namely fitting residual errors of the ion fragments j at the time i; p is the total number of factors, P-1 is the total number of OA pollution sources; wherein, the mass spectrum of P-1 OA factors is not limited, and the mass spectrum of inorganic nitrate I NA factors takes the fixed inorganic nitrate mass spectrum set in the step S3, and sets a variable range:

f in the above formula _j,INA The ratio of any ion fragment j in the inorganic nitrate I NA factor mass spectrum analyzed for PMF to all ion fragments; f (f) _j,NO3 The ratio of any ion fragment j in all ion fragments in the fixed inorganic nitrate mass spectrum set in the step S3; a is the maximum amplitude of variation of the mass spectral fragment fractions that allows adjustment.

As a preferred technical solution, in step S402, weighted least squares analysis is performed on the model created in step S401, taking notice of the ORG _NOx Is positive definite matrix, mass spectrum (MS _NOx ) And Time Series (TS) _NOx ) Each element in the matrix is also non-negative; the weighted residual square sum Q value is reduced through continuous iteration, and the calculation formula of the Q value is as follows:

sigma in the above formula _ij Is ORG _NOx Org in matrix _ij Standard deviation of the element; e, e _ij For matrix E _NOx The elements of the ith row and the jth column, namely fitting residual errors of the ion fragments j at the time i; when the Q value reaches a minimum, all elements in the matrix conform to their expected errors, i.e. |e _ij |/σ _ij About 1 to obtain the expected value Q of the Q value _exp Expected value Q of Q value _exp The calculation formula is as follows:

Q _exp ＝(t×m)-P×(t+m)

t in the above formula is ORG _NOx The number of rows of the matrix; m is ORG _NOx Column number of the matrix; p is the total number of factors.

As a preferred technical solution, the total number of artificial selection factors P in step S403 is such that the final MS _NOx An inorganic nitrate INA factor can be obtained in the matrix, the mass spectrum of the factor is in the variable range of the fixed mass spectrum set in the step S3 and does not contain organic matter fragments, and other P-1 OA factors areThe method can judge the organic aerosol pollution source represented by the method, the Q value is as small as possible, and the Q/Q is continuously increased when the total number of factors is increased _exp The decrease in value is no longer significant, a factor may be split into two factors with stronger collinearity; TS at this time _NOx The matrix shows the time series of the concentration of the individual factors.

As a preferable technical scheme, the concentration of the P-1 OA factors obtained in the step S4 and the NO in the mass spectrum thereof are utilized in the step S5 ⁺ And NO ₂ ⁺ Calculating the ratio of the ion fragments to obtain the organic nitrate radical NO _{3 organic matter} Concentration of organic nitrate groups NO _{3 organic matter} The concentration calculation formula of (2) is as follows:

NO in the above formula _{3 organic, i} Is NO _{3 organic matter} Mass concentration at time i; ts _ip The mass concentration at time i for a given OA factor p; ms of _pNO In mass spectra for a given OA factor p, NO ⁺ The ratio of ion fragments; ms of _pNO2 In mass spectra for a given OA factor p, NO ₂ ⁺ The ratio of ion fragments;

concentration of INA factor and NO _{3 organic matter} And (3) obtaining the total concentration of inorganic nitrate and organic nitrate after concentration addition, comparing the total concentration with the concentration of inorganic nitrate obtained in the AMS data processing process of the traditional aerosol mass spectrometer, and verifying the analysis result.

The method for detecting and estimating the aerosol of the atmospheric organic nitrate has the following beneficial effects: to bind NO ⁺ 、NO ₂ ⁺ The AMS-PMF (aerosol mass spectrometer-positive definite matrix factor analysis) analysis method of ion fragments and organic ion fragments is improved, and the mass spectrum composition of inorganic nitrate in the analysis process of fixed PMF (positive definite matrix factor analysis) is used for reducing the uncertainty of inorganic nitrate factors analyzed by PMF (positive definite matrix factor analysis), so that the accuracy of the analysis result of the concentration of the atmospheric organic nitrate is improvedIs beneficial to more clearly understanding the high time resolution change process of atmospheric organic nitrate pollution and deeply exploring the generation and aging mechanism of nitrogen-containing organic aerosol, organic precursor and NO _x And the influence and action among inorganic pollutants.

Detailed Description

Preferred embodiments of the present invention are described in detail below.

It will be appreciated that the present invention achieves the objects of the invention by some embodiments. The invention provides a detection and estimation method of an atmospheric organic nitrate aerosol, which comprises the following steps:

s1, selecting a representative observation station according to research requirements, continuously observing non-infusible submicron-level aerosol NR-PM in the atmosphere by using an aerosol mass spectrometer AMS without obvious pollution sources and shielding objects around the observation station _1.0 The organic component and the inorganic component of the mass spectrum of the organic ion fragments and the concentration time sequence of the inorganic ion fragments with high time resolution are obtained; typically, a set of mass spectral data is selected per minute, typically 15 to 30 days during the observation season or continuous observations for the contamination process;

s2 binding to NO ⁺ 、NO ₂ ⁺ Time series of ion fragments and organic ion fragment mass spectra to establish a mass spectrum containing NO ⁺ 、NO ₂ ⁺ The organic ion fragment concentration matrix of the ion fragments is ORG _NOx The matrix comprises the following specific steps:

since the AMS instrument (aerosol mass spectrometer) breaks up all molecules during electron bombardment at 70eV when measuring the aerosol composition, nitrate NO of inorganic nitrate ₃ ^- And nitrate radical NO in nitrogen-containing organic matter _{3 organic matter} Will be broken into NO ⁺ And NO ₂ ⁺ Ion fragments; however, in processing AMS observations, it is generally believed that all NO ⁺ And NO ₂ ⁺ The ion fragments are all from inorganic nitrate, and then inorganic nitrate NO is calculated ₃ ^- This results in an overestimation of the inorganic nitrate concentration and an omission of the organic nitrate;therefore, we will have all NO ⁺ And NO ₂ ⁺ The ion fragments and the organic ion fragments are combined and analyzed, and an ion fragment concentration matrix ORG is established _NOx T rows (t×m) are provided, t is the total number of data points, i.e. the total observation time, and each row of the matrix is observed by NO at the time corresponding to the row ⁺ (mass-to-charge ratio m/z is 29.99799), NO ₂ ⁺ (mass to charge ratio m/z is 45.99290) ion fragments and concentration of m-2 organic ion fragments of different mass to charge ratios;

s3, setting a fixed inorganic nitrate mass spectrum which is only composed of NO ⁺ (mass-to-charge ratio m/z is 29.99799) and NO ₂ ⁺ (mass-to-charge ratio m/z is 45.99290) ion fragments, and NO ⁺ And NO ₂ ⁺ The ratio of ion fragments was 2.4, as the results of prior studies indicate that NO was measured after breaking up the pure ammonium nitrate aerosol in AMS ⁺ /NO ₂ ⁺ The ratio is about 2.4; the ion fragment ratio of other mass-to-charge ratios is 0;

s4 PMF-to-ORG analysis Using positive definite matrix factor _NOx Analyzing the matrix to obtain a matrix with a predetermined ratio of NO ⁺ And NO ₂ ⁺ The INA factor representing inorganic nitrate and several independent sources representing different OA emissions and containing small amounts of NO ⁺ 、NO ₂ ⁺ The OA factor of the fragments is specifically as follows:

establishing a two-dimensional bilinear model

ORG _NOx ＝TS _NOx ×MS _NOx +E _NOx (1)

TS in equation (1) _NOx The matrix (t multiplied by p) is formed by a concentration time sequence of 1 inorganic nitrate I NA factor and p-1 OA factors, and t is the total number of data points, namely the total observation time; MS (MS) _NOx The matrix (p×m) consists of mass spectra of 1 inorganic nitrate factor I NA and p-1 OA factors; e (E) _NOx The matrix (t×m) is a residual matrix; ORG (optical fiber glass) _NOx Each element org in the matrix _ij Is composed of:

org in equation (2) _ij Is ORG _NOx The elements of row i, column j of the matrix, i.e. the observed mass concentration of ion fragments j at time i, include NO ⁺ 、NO ₂ ⁺ Fragments and all organic ion fragments; ts _ip For a matrix TS _NOx The elements in the ith row and the p th column, namely the mass concentration of a given factor p at time I, comprise inorganic nitrate INA factors and other OA factors; ms of _pj For matrix MS _NOx The p-th row, j-th column elements of (i.e. the ratio of ion fragments j in all ion fragments in mass spectrum given a factor p), including NO ⁺ 、NO ₂ ⁺ Fragments and all organic ion fragments, including inorganic nitrate ina factor and other OA factors; e, e _ij For matrix E _NOx The elements of the ith row and the jth column, namely fitting residual errors of the ion fragments j at the time i; p is the total number of factors, P-1 is the total number of OA pollution sources; the mass spectrum of the P-1 OA factors is not limited, and the mass spectrum of the inorganic nitrate I NA factors is taken as the fixed mass spectrum set in the step S3, and a certain variable range is set:

f in formula (3) _j,INA The ratio of any ion fragment j in the inorganic nitrate I NA factor mass spectrum analyzed for PMF to all ion fragments; f (f) _j,NO3 The ratio of any ion fragment j in all ion fragments in the fixed mass spectrum set in the step S3; a is the maximum variation amplitude of the mass spectrum fragment ratio which is allowed to be adjusted, and generally, the value of a can be 10%;

further, weighted least squares analysis is performed on the model, noting the ORG _NOx Is positive definite matrix, mass spectrum (MS _NOx ) And Time Series (TS) _NOx ) Each element in the matrix is also non-negative; making the weighted residual square sum Q variable by successive iterationsThe calculation formula of the Q value is small:

sigma in formula (4) _ij Is ORG _NOx Org in matrix _ij Standard deviation of the element; when the Q value reaches a minimum, all elements in the matrix conform to their expected errors, i.e. |e _ij |/σ _ij Approximately 1, the expected value Q of Q at this time _exp The calculation formula of (2) is as follows:

Q _exp ＝(t×m)-P×(t+m) (5)

t in formula (5) is ORG _NOx The number of rows of the matrix; m is ORG _NOx Column number of the matrix; p is the total number of factors;

by Q/Q _exp The ratio is used for evaluating the quality of a PMF analysis result; artificially selecting the total number of factors P such that the final MS _NOx The matrix can obtain an inorganic nitrate I NA factor (the mass spectrum of which does not contain organic fragments within the changeable range of the fixed mass spectrum set in the step S3), other P-1 OA factors can also judge the organic aerosol pollution source represented by the inorganic nitrate I NA factor, the Q value is as small as possible, and the Q/Q is increased when the total number of factors is continuously increased _exp The decrease in value is no longer significant, a factor may be split into two factors with stronger collinearity; TS at this time _NOx The matrix gives the concentration time series of each factor; in general, the above-described factor resolution process can be implemented by PMF toolkit (PMF Evaluation Toolkit, PET, version 3.04) and multiple linear model tool (multilinear engine (ME-2) actualization);

s5 utilizing the concentration of the P-1 OA factors obtained in the step S4 and NO in the mass spectrum thereof ⁺ And NO ₂ ⁺ Calculating the ratio of the ion fragments to obtain the organic nitrate radical NO _{3 organic matter} The specific method is as follows:

the P-1 OA factors obtained in step S4 are the organic components of the aerosol observed by AMS, and small amounts of NO are still present in the mass spectrum ⁺ And NO ₂ ⁺ Ion fragments, this part of NO ⁺ And NO ₂ ⁺ Ion fragments are believed to be derived from organic nitrogen species; thus, according to the NO in each OA factor mass spectrum ⁺ And NO ₂ ⁺ The ratio of the ion fragments and the concentration of the OA factor are calculated to obtain NO at each moment _{3 organic matter} Mass concentration, organic nitrate radical NO _{3 organic matter} The concentration calculation formula of (2) is as follows:

NO in formula (6) _{3 organic, i} Is NO _{3 organic matter} Mass concentration at time i; ts _ip The mass concentration at time i for a given OA factor p; ms of _pNO In mass spectra for a given OA factor p, NO ⁺ The ratio of ion fragments; ms of _pNO2 In mass spectra for a given OA factor p, NO ₂ ⁺ The ratio of ion fragments; further, the total mass concentration of the granular organic nitrogen sol pON can also be calculated by adopting the relative molecular mass empirical value of pON of 200-300 g/mol;

in addition, the INA factor obtained in step S4 represents the inorganic nitrate component of the aerosol observed by AMS, which does not contain organic fragments in the mass spectrum, and NO in the mass spectrum ⁺ And NO ₂ ⁺ Ion fragments are believed to all be from inorganic nitrate salts; can be used for concentrating INA factor and NO _{3 organic matter} The total concentration of inorganic nitrate and organic nitrate is obtained after the concentration addition and is compared with the inorganic nitrate NO obtained in the traditional AMS data processing process ₃ ^- And comparing the concentrations, and verifying the analysis result.

The method for detecting and estimating the aerosol of the atmospheric organic nitrate has the following beneficial effects: to bind NO ⁺ 、NO ₂ ⁺ The AMS-PMF (aerosol mass spectrometer-positive definite matrix factor analysis) analysis method of ion fragments and organic ion fragments is improved, and the mass spectrum composition of inorganic nitrate in the process of fixed PMF (positive definite matrix factor analysis) analysis is adopted, so that the inorganic nitrate analyzed by PMF (positive definite matrix factor analysis) is reducedThe uncertainty of the acid salt factor improves the accuracy of the analysis result of the concentration of the atmospheric organic nitrate, which is beneficial to the clearer understanding of the high time resolution change process of the atmospheric organic nitrate pollution and the deep exploration of the generation and aging mechanism of the nitrogen-containing organic aerosol, the organic precursor and NO _x And the influence and action among inorganic pollutants.

It will be understood that the invention has been described in terms of several embodiments, and that various changes and equivalents may be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all modifications and equivalents falling within the scope of the claims of the present application. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (8)

1. The method for detecting and estimating the atmospheric organic nitrate aerosol is characterized by comprising the following steps of:

s1, continuously observing organic components and inorganic components of an atmospheric non-refractory submicron-level aerosol by using an aerosol mass spectrometer AMS to obtain a high-resolution organic ion fragment mass spectrum concentration time sequence and an inorganic ion fragment concentration time sequence;

s2 binding to NO ⁺ 、NO ₂ ⁺ Time series of ion fragments and organic ion fragment mass spectra to establish a mass spectrum containing NO ⁺ 、NO ₂ ⁺ The organic ion fragment concentration matrix of the ion fragments is ORG _NOx A matrix;

s3, setting a fixed inorganic nitrate mass spectrum, wherein the mass spectrum is onlyFrom NO ⁺ And NO ₂ ⁺ Ion fragments are formed and fixed in proportion;

s4 PMF-to-ORG analysis Using positive definite matrix factor _NOx Analyzing the matrix to obtain a matrix with a predetermined ratio of NO ⁺ And NO ₂ ⁺ INA factor representing inorganic nitrate formed by fragments, and several independent sources representing different OA emissions and containing small amounts of NO ⁺ 、NO ₂ ⁺ The OA factor of the fragments;

s5 utilizing the concentration of each OA factor obtained in the step S4 and NO in the mass spectrum thereof ⁺ And NO ₂ ⁺ Calculating the ratio of the ion fragments to obtain the organic nitrate radical NO _{3 organic matter} Is a concentration of (3).

2. The method for detecting and estimating an aerosol of atmospheric organic nitrate according to claim 1, wherein the ORG established in step S2 _NOx The matrix (t×m) has t rows, t is the total number of data points, namely the total observation time, ORG _NOx NO observed from each row of the matrix at the time corresponding to that row ⁺ 、NO ₂ ⁺ Ion fragments and the concentration of m-2 organic ion fragments with different mass-to-charge ratios.

3. The method for detecting and estimating an atmospheric organic nitrate aerosol according to claim 1, wherein NO of the inorganic nitrate mass spectrum set in step S3 ⁺ And NO ₂ ⁺ The ratio of the ion fragments is 2.3-2.5.

4. The method for detecting and estimating an aerosol of atmospheric organic nitrate according to claim 1, wherein the step S4 is performed by using positive definite matrix factor analysis (PMF) on ORG _NOx Analyzing the matrix to obtain a matrix with a predetermined ratio of NO ⁺ And NO ₂ ⁺ INA factor representing inorganic nitrate formed by fragments, and several independent sources representing different OA emissions and containing small amounts of NO ⁺ 、NO ₂ ⁺ The OA factor of the fragments specifically comprisesThe method comprises the following steps:

s401 building ORG _NOx A two-dimensional bilinear model of the matrix and limiting mass spectra of INA factors representing inorganic nitrates in the mass spectrum matrix of the model;

s402, carrying out weighted least square analysis on the model established in the step S401, enabling the square sum Q value of weighted residual errors to be smaller through continuous iteration, and when the Q value reaches the minimum, ORG _NOx All elements in the matrix conform to their expected errors to obtain an expected value Q of the Q value _exp A value;

s403 artificially selecting the total number of factors P by using the Q value and Q _exp And (3) evaluating the quality of the PMF analysis result by the positive definite matrix factor analysis method by the ratio of the values to finally obtain a mass spectrum matrix and a concentration time sequence matrix of 1 inorganic nitrate INA factor and P-1 OA factor.

5. The method for detecting and estimating an aerosol of organic nitrate in the atmosphere according to claim 4, wherein step S401 comprises NO ⁺ 、NO ₂ ⁺ Organic ion fragment concentration matrix ORG of ion fragments _NOx Is:

ORG _NOx ＝TS _NOx ×MS _NOx +E _NOx

TS in the above equation _NOx The matrix (t multiplied by p) is composed of a concentration time sequence of 1 inorganic nitrate INA factor and p-1 OA factors, and t is the total number of data points, namely the total observation time; MS (MS) _NOx The matrix (p×m) consists of mass spectra of 1 inorganic nitrate INA factor and p-1 OA factors; e (E) _NOx The matrix (t×m) is a residual matrix; ORG (optical fiber glass) _NOx Each element org in the matrix _ij Is composed of:

org in the above formula _ij Is ORG _NOx The elements of row i, column j of the matrix, i.e. the observed mass concentration of ion fragments j at time i, include NO ⁺ 、NO ₂ ⁺ Fragments and all organic ion fragments; ts _ip For a matrix TS _NOx The elements of row i and column p, namely the mass concentration of a given factor p at time i, include inorganic nitrate INA factors and other OA factors; ms of _pj For matrix MS _NOx The p-th row, j-th column elements of (i.e. the ratio of ion fragments j in all ion fragments in mass spectrum given a factor p), including NO ⁺ 、NO ₂ ⁺ Fragments and all organic ion fragments, including inorganic nitrate INA factors and other OA factors; e, e _ij For matrix E _NOx The elements of the ith row and the jth column, namely fitting residual errors of the ion fragments j at the time i; p is the total number of factors, P-1 is the total number of OA pollution sources; wherein, the mass spectrum of P-1 OA factors is not limited, and the mass spectrum of inorganic nitrate INA factors takes the fixed inorganic nitrate mass spectrum set in the step S3, and sets a variable range:

f in the above formula _j,INA The ratio of any ion fragment j in the inorganic nitrate INA factor mass spectrum analyzed for PMF to all ion fragments; f (f) _j,NO3 The ratio of any ion fragment j in all ion fragments in the fixed inorganic nitrate mass spectrum set in the step S3; a is the maximum amplitude of variation of the mass spectral fragment fractions that allows adjustment.

6. The method for detecting and estimating an aerosol of organic nitrate in the atmosphere according to claim 4, wherein the model created in step S401 is subjected to weighted least squares analysis in step S402, taking care of ORG _NOx Is positive definite matrix, mass spectrum (MS _NOx ) And Time Series (TS) _NOx ) Each element in the matrix is also non-negative; the weighted residual square sum Q value is reduced through continuous iteration, and the calculation formula of the Q value is as follows:

sigma in the above formula _ij Is ORG _NOx Org in matrix _ij Standard deviation of the element; e, e _ij For matrix E _NOx The elements of the ith row and the jth column, namely fitting residual errors of the ion fragments j at the time i; when the Q value reaches a minimum, all elements in the matrix conform to their expected errors, i.e. |e _ij |/σ _ij About 1 to obtain the expected value Q of the Q value _exp ，Q _exp The calculation formula of (2) is as follows:

Q _exp ＝(t×m)-P×(t+m)

t in the above formula is ORG _NOx The number of rows of the matrix; m is ORG _NOx Column number of the matrix; p is the total number of factors.

7. The method for detecting and estimating an aerosol of organic nitrates in the atmosphere according to claim 4, wherein the total number of artificial selection factors P in step S403 is such that the final MS _NOx An inorganic nitrate INA factor can be obtained in the matrix, the mass spectrum of the inorganic nitrate INA factor is in the variable range of the fixed mass spectrum set in the step S3 and does not contain organic matter fragments, other P-1 OA factors can also judge the organic aerosol pollution source represented by the inorganic nitrate INA factor, the Q value is as small as possible, and the Q/Q is when the total number of factors is continuously increased _exp The decrease in value is no longer significant, a factor may be split into two factors with stronger collinearity; TS at this time _NOx The matrix shows the time series of the concentration of the individual factors.

8. The method for detecting and estimating an aerosol of organic nitrate in the air according to claim 1, wherein the concentration of P-1 OA factors obtained in step S4 and the NO in the mass spectrum thereof are used in step S5 ⁺ And NO ₂ ⁺ Calculating the ratio of the ion fragments to obtain the organic nitrate radical NO _{3 organic matter} Concentration of organic nitrate groups NO _{3 organic matter} The concentration calculation formula of (2) is as follows:

NO in the above formula _{3 organic, i} Is NO _{3 organic matter} Mass concentration at time i; ts _ip The mass concentration at time i for a given OA factor p; ms of _pNO In mass spectra for a given OA factor p, NO ⁺ The ratio of ion fragments; ms of _pNO2 In mass spectra for a given OA factor p, NO ₂ ⁺ The ratio of ion fragments;

concentration of INA factor and NO _{3 organic matter} And (3) obtaining the total concentration of inorganic nitrate and organic nitrate after concentration addition, comparing the total concentration with the concentration of inorganic nitrate obtained in the AMS data processing process of the traditional aerosol mass spectrometer, and verifying the analysis result.