主要人为排放源中氮氧化物^(15)N自然丰度的测定  

Determination of ^(15)N Natural Abundance in Nitrogen Oxides from Major Anthropogenic Emission Sources

作　　者：王曦[1] 遆超普[1] 罗永霞[1] 孙晓丽[1] WANG Xi TI Chaopu LUO Yongxia SUN Xiaoli(State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China)

机构地区：[1]土壤与农业可持续发展国家重点实验室(中国科学院南京土壤研究所),南京210008

出　　处：《土壤学报》2016年第6期1552-1562,共11页Acta Pedologica Sinica

基　　金：土壤与农业可持续发展国家重点实验室分析技术方法研究项目(Y412010010)资助~~

摘　　要：氮氧化物(NO_x=NO+NO_2)因其对环境和人类健康的威胁,成为大气中需要严格控制的一种痕量组分。首次运用化学转化法,通过将主要人为排放源废气中的氮氧化物(NO_x)转化为氧化亚氮(N_2O),测定气体中NO_x的15N自然丰度,即氮稳定同位素比值(δ15N-NO_x)。利用酸性氧化剂将NO_x氧化为硝酸(NO_3^-),并通过三氯化钒(VCl_3)和叠氮钠(NaN_3)的共同作用将其转化为N_2O,利用带有自动预浓缩装置的稳定同位素比值质谱计(PT-IRMS)测定δ15N-NO_x。该方法的测量精度可达0.09‰,所需样品量仅为7μg(以氮计),对火力发电站、机动交通工具等人为排放源均适用,测量精度和准确度可满足NOx相关研究的需求。【Objective】 Nitrogen oxides（NO_x = NO and NO_2）are now a critical kind of trace component that calls for strict control,for they threaten the environment and human health. As NO_x has its unique isotope signature that varies with its source,the technique of stable isotope analysis can be used to investigate its origin and pathways. This study is to introduce a new method,chemical conversion process,for determination of 15 N natural abundance（δ15N）of the nitrogen oxides from major anthropogenic sources. With the aid of this method,it is feasible for us to gradually understand the problem caused by NO_xemissions and hence to design appropriate relevant strategies to manage it.【Method】Based mainly on the technique of isotopic analysis of nitrous oxide（N2O）,the chemical conversion method is first to oxidize NO_x into nitrate（NO_3^-）withhydrogen peroxide（H2O2）in an acid condition.The resultant NO_3^- was then converted into N_2O under the joint effect of vanadium（Ⅲ）chloride（VCl3）and sodium azide（Na N3）in a strongacid condition.The newly formed N_2O is trapped in an automatic cryogenic system and then diverted into a gas chromatographic column for analysis. The isolated nitrous oxide is analyzed in a stable isotope mass spectrometer under the continuous flowing mode for determination of δ15N,which is then converted into that of the initial NO_x using an equation. While testing this method,some other tests were carried out to optimize the experimental conditions for this method. After these tests,eventually NO_x in gas samples of different sources can be trapped completely in the absorption solution,with absorption rate reaching as high as 99%. At this time,fractionation of stable isotopeis inhibited due to incomplete absorption. As conversion of NO_xinto NO_3^- takes place in the absorption solution,it is possible to use standard nitrate solutions to simulate the absorption solutions that contained NO_x standard gas sample. Usgs32 and usgs34 are mixed at different volume rati

关 键 词：氮氧化物 氧化亚氮 15N自然丰度 化学转化法 

分 类 号：X132[环境科学与工程—环境科学] O615.45[理学—无机化学]