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首页> 外文期刊>Environmental Science & Technology >Carbon Isotope Fractionation during Diffusion and Biodegradation of Petroleum Hydrocarbons in the Unsaturated Zone: Field Experiment at Vaerlose Airbase, Denmark, and Modeling
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Carbon Isotope Fractionation during Diffusion and Biodegradation of Petroleum Hydrocarbons in the Unsaturated Zone: Field Experiment at Vaerlose Airbase, Denmark, and Modeling

机译：碳氢化合物在不饱和区的扩散和生物降解过程中的碳同位素分馏：丹麦Vaerlose空军基地的野外实验和建模

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A field experiment was conducted in Denmark in order to evaluate the fate of 13 volatile organic compounds (VOCs) that were buried as an artificial fuel source in the unsaturated zone. Compound-specific isotope analysis showed distinct phases in the ~(13)C/~(12)C ratio evolution in VOC vapors within 3 m from the source over 114 days. At day 3 and to a lesser extent at day 6, the compounds were depleted in ~(13)C by up to -5.7% with increasing distance from the source compared to the initial source values. This trend can be explained by faster outward diffusion of the molecules with ~(12)C only compared to molecules with a ~(13)C. Then, the isotope profile leveled out, and several compounds started to become enriched in ~(13)C by up to 9.5% with increasing distance from the source, due to preferential removal of the molecules with ~(12)C only, through biodegradation. Finally, as the amount of a compound diminished in the source, a ~(13)C enrichment was also observed close to the source. The magnitude of isotope fractionation tended to be larger the smaller the mass of the molecule was. This study demonstrates that, in the unsaturated zone, carbon isotope ratios of hydrocarbons are affected by gas-phase diffusion in addition to biodegradation, which was confirmed using a numerical model. Gas-phase diffusion led to shifts in δ~(13)C > 1% duringrnthe initial days after the spill, and again during the final stages of source volatilization after > 75% of a compound had been removed. In between, diffusion has less of an effect, and thus isotope data can be used as an indicatorfor hydrocarbon biodegradation.
机译：为了评估13种挥发性有机化合物（VOC）的命运，这些挥发性有机化合物作为人工燃料来源被埋在不饱和区中，在丹麦进行了现场试验。化合物特异性同位素分析显示，距源3 m之内的VOC蒸气在114天内〜（13）C /〜（12）C比率演化过程中存在明显的不同阶段。在第3天，在第6天的程度较小，在〜（13）C中，与原始来源的距离相比，随着与来源的距离增加，化合物的耗竭量高达-5.7％。这种趋势可以通过仅具有〜（12）C的分子相比具有〜（13）C的分子更快的向外扩散来解释。然后，同位素分布趋于平稳，并且由于仅通过生物降解优先去除了〜（12）C的分子，因此随着离源距离的增加，几种化合物开始在〜（13）C中富集高达9.5％。 。最后，随着源中化合物数量的减少，在源附近也观察到〜（13）C富集。分子的质量越小，同位素分馏的幅度就越大。这项研究表明，在不饱和区中，碳氢化合物的碳同位素比除了受到生物降解作用外，还受到气相扩散的影响，这一点已通过数值模型得到证实。在泄漏后的最初几天，气相扩散导致δ〜（13）C> 1％的变化，而在> 75％的化合物被去除后，在源挥发的最后阶段又发生了变化。在两者之间，扩散的影响较小，因此同位素数据可用作烃类生物降解的指标。

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