| 玉米秸秆烟尘中正构脂肪酸的分子与碳同位素组成 |
| 摘要点击 1504 全文点击 990 投稿时间：2016-03-25 修订日期：2016-05-13 |
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| 中文关键词 玉米秸 烟尘 正构脂肪酸 分子组成 碳同位素 |
| 英文关键词 maize straw smoke n-alkanoic acid molecular composition carbon isotope |
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| 中文摘要 |
| 在模拟的明火燃烧和闷烧条件下对4种玉米秸秆进行了焚烧试验，用GC/MS和GC/C/IRMS分别测定烟尘中正构脂肪酸的分子与碳同位素组成.结果表明，在明火烟尘中正构脂肪酸由C7~C34组成，其平均总含量为13895.0 mg·kg-1.其低碳数（≤C16）与高碳数（>C16）正构脂肪酸的含量比（L/H）平均值为1.1.C18/C16、C24/C16、C24/C18、C24/（C22+C26）（CAR）的平均值分别为0.33、0.17、0.50、1.2.正构脂肪酸单体表现出以C16、C24为主、次峰碳数的双峰式分布模式.其碳优势指数（CPI）的平均值为4.5.在闷烧烟尘中正构脂肪酸由C6~C34组成，其平均总含量为50183.7 mg·kg-1.L/H、C18/C16、C24/C16、C24/C18、CAR的平均值分别为1.3、0.33、0.20、0.60、1.6.也具有与明火烟尘相同的分布模式.其CPI的平均值为6.1.明火烟尘中C14~C26单体的δ13 C平均值在-21.0‰~-24.8‰之间变化，总平均值为-23.5‰.该值与玉米秸秆中对应值之差（Δ13 C）达-0.7‰.闷烧烟尘中C14~C26单体δ13C平均值的变化范围为-21.8‰~-25.4‰，总平均值为-23.3‰.其Δ13 C值达-0.5‰.与玉米秸秆相比，两种烟尘中正构脂肪酸的分子组成和碳同位素组成均发生了明显的改变.L/H、C24/C16、C24/C18、CAR、δ13 C等指标可用于识别大气气溶胶中玉米秸秆燃烧来源的正构脂肪酸. |
| 英文摘要 |
| Four cultivars of maize straw were burned under flaming and smoldering conditions. Smoke samples were colleted and analyzed by GC/MS and GC/C/IRMS to determine molecular and stable carbon isotopic compositions of n-alkanoic acids in them. The results showed that n-alkanoic acids in flaming smoke were composed of C7 to C34, with a mean total content of 13895.0 mg·kg-1. The average ratio values of the content for homologues with lower carbon number (≤C16) to that for ones with higher carbon number (>C16) (L/H), C18/C16, C24/C16, C24/C18, and C24/(C22+C26) (CAR) were 1.1, 0.33, 0.17, 0.50, and 1.2, respectively. Moreover, the acids exhibited a bimodal profile with peaks at C16 and C24, respectively. They had evident even to odd carbon number predominance (mean CPI: 4.5). In smoldering smoke the acids were consisted of C6 to C34, with an average total content of 50183.7 mg·kg-1. The mean ratios of L/H, C18/C16, C24/C16, C24/C18, and CAR were 1.3, 0.33, 0.20, 0.60, and 1.6, respectively. In addition, the homologues had the same distribution pattern as in flaming smoke and even to odd carbon number predominance (mean CPI=6.1). The mean carbon isotopic ratio (δ13 C) values for individual n-alkanoic acids (C14 to C26) in flaming smoke ranged from -21.0‰ to -24.8‰, the overall average of which was -23.5‰. The difference between mean δ13 C values of n-fatty acids in flaming smoke and the straw (Δ13 C) was -0.7‰. In smoldering smoke, the mean δ13 C values for the compounds varied from -21.8‰ to -25.4‰, with an overall average of -23.3‰. The Δ13 C value was up to -0.5‰. The molecular and carbon isotopic compositions of n-alkanoic acids in smoke were significantly different from those in straw matter. L/H, C24/C16, C24/C18, CAR, and δ13 C might be useful proxies to discriminate the organic pollutants in atmospheric aerosols derived from maize straw combustion. |
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