中文摘要：

温室气体CO_2浓度增长引起的气候变化问题受到全球广泛关注。CO_2的稳定碳同位素特征可为其源汇机制研究提供有力支持,但需要各类污染源排放的碳同位素特征值,尤其是局地或区域特征作为数据基础。CO_2浓度的增长主要来自化石燃料燃烧,机动车排放是一个重要来源。研究应用基于激光的同位素比红外光谱仪（IRIS）,对我国汽油车尾气排放CO_2的稳定碳同位素组成（δ~（13）C）进行了初步的研究,测定结果为（-28.0±0.5）‰。汽油车尾气排放CO_2出现碳同位素分馏现象,其δ~（13）C特征受冷热起动方式影响不大,但与汽油成分、发动机燃烧模式等相关;汽油车尾气排放CO_2的δ18O特征变化较大,同位素分馏更为复杂。化石燃料燃烧产生CO_2的δ~（13）C特征对化石燃料具有较好的指示作用。本研究为碳排放研究提供了重要的数据支持。

英文摘要：

The Problem of climate change caused by the increase of greenhouse gas CO_2 concentration attracts the world＇s attention. Stable carbon isotopic characteristics of CO_2 can provide strong support for the study of source and sink mechanism of CO_2. However, this needs the stable carbon isotope composition of different emission sources, specially local or regional sources as data base. The combustion of fossil fuel contributes a lot to the increase of CO_2 concentration, especially the emission of vehicles. In this study, we used laser-based isotope ratio infrared spectrometer（IRIS） to measure the δ~（13）C characteristics of CO_2 emitted by gasoline vehicles in China, getting its stable carbon isotope composition（δ 13C） of（-28.0 ± 0.5）‰. Carbon isotope fractionation exists in CO_2 emitted by gasoline vehicles. δ~（13）C of CO_2 emitted by gasoline vehicles is not affected by cold start or hot start basically, but the composition of gasoline and engine combustion mode can influence δ~（13）C of CO_2. The δ 18 O characteristics of CO_2 emitted by gasoline vehicles changes a lot, with more complicated isotope fractionation. The δ~（13）C characteristics of CO_2 from combustion processes of fossil fuels can be a good indicator for fossil fuels. The δ~（13）C of CO_2 emitted by gasoline vehicles as representative of China can be obtained from this preliminary study, providing basic foundation for the carbon emissions research in China.