Tracing The Sources Of Amines In The Atmosphere By Compound-specific Nitrogen Isotope Analysis （CSIA）

As a kind of important nitrogenous compounds,amines are easy to be released from the matrix into the environment,causing extensive pollution in each layer.Traditional concentration analysis methods can not provide accurate information about the source and degree of degradation.Compound-specific Stable Isotope Analysis（CSIA）can be used to analyze the Stable Isotope composition of specific elements（such as nitrogen）in amines,which can overcome the deficiency of quantitative Analysis of concentration and effectively trace the source and pollution process of amines from the perspective of isotopes.Compound-specific stable nitrogen isotope analysis technology started late.And the traditional stable nitrogen isotope tracer is usually the characteristic stable nitrogen isotope of nitrogen-containing substances in the mixture,so it is impossible to analyze and study the stable nitrogen isotope of a single compound.Moreover,there are many pretreatment steps for sample determination,which requires high concentration of nitrogen-containing substances in the sample.Due to the limitation of Compound-specific stable nitrogen isotope analysis methods,there are no reports on compound-specific nitrogen isotope data of amines from different sources.In this study,the concentration distribution characteristics of amines in atmospheric particulate matter(PM₁₀)in Guangzhou were analyzed in winter,spring,summer and autumn.On this basis,the Compound-specific stable nitrogen isotope analysis method was established,which successfully realized the separation and analysis of stable nitrogen isotope of organic amine monomer in the sample.The database of amine monomer nitrogen isotope was established initially,providing scientific basis for tracing the source of amine.The conclusions of this study are as follows:（1）Concentration distribution characteristics of organic amines in typical atmospheric particles:Amines in particulate matter samples were determined by gas chromatography-mass spectrometry（GC-MS）.MA（Methylamine）,DMA（Dimethylamine）,DEA（Diethylamine）,Pr A（Propylamine）,1-BA（1-butylamine）and ANL（Aniline）,were found in the particulate matter samples of the three typical emission sources.The mean values of the sum of the six amines in PM₁₀ from different sampling areas showed the variation characteristics of marine source（50.5±37.6ng/m~3）>municipal solid waste sanitary landfill（48.8±37.5 ng/m~3）>traffic sources（36.2±16.2 ng/m~3）.MA and DMA concentrations accounted for more than 75%of the total amine concentration,and were the main amines enriched on PM₁₀.The mean value of the sum of the six amines concentrations in PM₁₀ in different seasons was winter>summer>spring>autumn.Environmental factors including temperature and atmospheric relative humidity（RH）are related to the enrichment of amines on particulate matter.（2）Application and determination of amineδ¹⁵N in particulate matter by compound-specific nitrogen isotope analysis（CSIA）:1)In this study,the instrument parameters（reaction furnace temperature,carrier gas flow,sample size,derivatization,gas chromatographic column）on gas chromatography-combustion-isotope ratio mass spectrometry（GC-C-IRMS）were optimized to achieve accurate and accurate isotopic determination of amines.The results show that the accurate and reliableδ¹⁵N can be obtained with the error（1σ）of isotope analysis greater than 0.5‰when the sample amount is not less than 19.19 ng N（1.62 nmol N）.The isotopic composition of amines can be accurately measured by the derivatization reagent IBCF.Elemental analysis-isotope ratio mass spectrometer（EA-IRMS）was used for N isotope analysis of underived amines,and the standard deviation of N isotope analysis of all amines was better than 0.3‰.The standard deviation of N isotope analysis of all amines was better than 0.5‰when GC system was used for N isotope analysis of underived amines.The stable nitrogen isotope values of aminated amines measured by GC-C-IRMS were in good agreement with the true values of the standard organic amines（EA-IRMS）,and the mean absolute difference was 0.16‰,which was far less than the instrumental error of±0.5‰.It can be seen that the derivatization process does not cause the fractionation of nitrogen isotopes.（2）The compound-specific nitrogen isotope analysis（CSIA）was used to study the characteristic values of nitrogen isotopes of amines in atmospheric particulate matter in Guangzhou.The results showed that:（1）Theδ¹⁵N-MA andδ¹⁵N-1-BA from different sources are significantly different.The isotopic composition of MA measured can basically represent the isotopic composition of MA from municipal solid waste sanitary landfill sources(δ¹⁵N=-34.02--19.12‰)and traffic sources(δ¹⁵N=-20.99--3.49‰).The measured 1-BA isotopic composition can basically represent the 1-BA isotopic composition of municipal solid waste sanitary landfill sources(δ¹⁵N=-23.92--6.26‰)and marine sources(δ¹⁵N=-3.86-+4.80‰).（2）Theδ¹⁵N-MA andδ¹⁵N-1-BA showed obvious seasonal variation.Theδ¹⁵N value was lighter in winter when the concentration of amine was high,and heavier in summer when the concentration of amine was low.The stable nitrogen isotopic composition of amine showed a certain correlation with its concentration.It is concluded that the compound-specific nitrogen isotope analysis（CSIA）developed in this study can be used as an important tool to identify the source of amine pollution and transformation pathway,and has higher accuracy and precision.