Carbon isotope analyses of n-alkanes in dust from the lower atmosphere over the central eastern Atlantic
Carbon isotope analyses of n-alkanes in dust from the lower atmosphere over the central eastern Atlantic
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DOI：
10.1016/s0016-7037(02)01414-x
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发表时间：
2003-05
影响因子：
5
通讯作者：
E. Schefuß;V. Ratmeyer;J. Stuut;J. Jansen;Jaap S. Sinninghe Damsté
中科院分区：
文献类型：
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作者：
E. Schefuß;V. Ratmeyer;J. Stuut;J. Jansen;Jaap S. Sinninghe Damsté
沿着西非海岸横断面收集的大气尘埃样本已被研究其脂质含量和特定化合物的稳定碳同位素组成。有机溶剂提取物的饱和烃馏分主要由来自陆生植物表皮蜡层的长链正烷烃组成。使用全球大气环流模型计算每个采样日和地点的后向轨迹。主要的大气输送发生在低层信风层，但南部地区除外，那里发生了对流层中部的远距离输送。正构烷烃同系物链长分布的变化可能与干旱有关，而不是与温度或植被类型有关。叶蜡正烷烃的碳偏好表现出显着的变化，这归因于化石燃料或海洋来源的脂质的不同贡献。然而，这种非蜡贡献对气溶胶中两种主要正构烷烃（n-C29 和 n-C31 烷烃）的 δ13C 值的影响并不显着。它们的 δ13C 值被转换为 C4vs 的百分比。 C3植物类型贡献，使用具有文献中同位素端元值的二组分混合方程。数据表明，只有以 C4 型植被为主的地区，即撒哈拉、萨赫勒和加蓬，才向尘埃有机物提供源自 C4 植物的脂质。气溶胶中叶蜡脂的稳定碳同位素组成主要反映了其运输路径上的现代植被类型。叶表面蜡颗粒的风磨损，通过喷砂效应增强，很可能是陆源脂质形成气溶胶的主要过程。
Atmospheric dust samples collected along a transect off the West African coast have been investigated for their lipid content and compound-specific stable carbon isotope compositions. The saturated hydrocarbon fractions of the organic solvent extracts consist mainly of long-chain n-alkanes derived from epicuticular wax coatings of terrestrial plants. Backward trajectories for each sampling day and location were calculated using a global atmospheric circulation model. The main atmospheric transport took place in the low-level trade-wind layer, except in the southern region, where long-range transport in the mid-troposphere occurred. Changes in the chain length distributions of the n-alkane homologous series are probably related to aridity, rather than temperature or vegetation type. The carbon preference of the leaf-wax n-alkanes shows significant variation, attributed to a variable contribution of fossil fuel- or marine-derived lipids. The effect of this nonwax contribution on the δ13C values of the two dominant n-alkanes in the aerosols, n-C29and n-C31alkane, is, however, insignificant. Their δ13C values were translated into a percentage of C4vs. C3plant type contribution, using a two-component mixing equation with isotopic end-member values from the literature. The data indicate that only regions with a predominant C4type vegetation, i.e. the Sahara, the Sahel, and Gabon, supply C4plant-derived lipids to dust organic matter. The stable carbon isotopic compositions of leaf-wax lipids in aerosols mainly reflect the modern vegetation type along their transport pathway. Wind abrasion of wax particles from leaf surfaces, enhanced by a sandblasting effect, is most probably the dominant process of terrigenous lipid contribution to aerosols.