AMS radiocarbon measurements of individual organic molecules : making preparative capillary GC system and its application to geochemical samples

采用制备型毛细管气相色谱（PCGC）和加速器质谱（AMS）对半城市气溶胶样品进行了单个脂肪酸的化合物特异性放射性碳分析。气溶胶脂肪酸（C16 ~ C34）呈典型的双峰分布，在C16和C26处有两个最大值。它们的碳同位素组成范围为-30.3‰（C26） ~ -23.3‰（C18），表明它们来源于陆生高等植物和海洋植物。C16-C22脂肪酸的放射性碳测量显示了现代的14C年龄，这表明这些酸是由现存的高等植物释放的，也可能来自海洋生物。另一方面，具有陆生植物蜡质特征的C24-C26脂肪酸的14C年龄为5860 （EA200）年。这表明，高分子量脂肪酸的一部分已经储存在地球化学储存库，如土壤中至少数百年至数千年，然后排放到大气中。这些老化的脂肪酸可以通过大气从亚洲大陆长途运输。

Compound-specific radiocarbon analysis of individual fatty acids was conducted for a semi-urban aerosol sample using a preparative capillary gas chromatography (PCGC) system and an accelerator mass spectrometry (AMS). The aerosol fatty acids (C16 to C34) showed a typical bimodal distribution with two maxima at C16 and C26. Their carbon isotopic compositions ranged from -30.3 ‰ (C26) to -23.3 ‰ (C18), suggesting that they are derived from terrestrial higher plants and marine sources. Radiocarbon measurements of C16-C22 fatty acids showed modern 14C ages, suggesting that the acids are emitted from living higher plants and possibly from marineorganisms. On the other hand, C24-C26 fatty acids that arecharacteristic to terrestrial plant waxes showed 14C ages of 5860 (EA200) years. This suggests that some portion of higher molecular weight fatty acids have been stored in geocnemical reservoirs such as soils at least for hundreds to thousands of years arid then emitted to the atmosphere. These aged fatty acids could be in part transported long distances from the Asian continent through the atmosphere.