Hydrogen isotope ratios of recent lacustrine sedimentary n-alkanes record modern climate variability
Hydrogen isotope ratios of recent lacustrine sedimentary n-alkanes record modern climate variability
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DOI：
10.1016/j.gca.2004.06.004
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发表时间：
2004-12
影响因子：
5
通讯作者：
D. Sachse;J. Radke;G. Gleixner
中科院分区：
文献类型：
--
作者：
D. Sachse;J. Radke;G. Gleixner
研究人员测量了沿N-S欧洲样带从近期湖泊表层沉积物中提取的正构烷烃（n- c12至n-C31）的氢同位素比率，以测试这些生物标志物是否记录了现代气候变异。将正构烷烃的δD值与IAEA-GNIP数据库中瑞典北部- 119‰至意大利南部- 41‰的大气水δD值、湖泊水δD值以及年平均气温（北部- 2.0°C至南部13.7°C）进行了比较。除藻类衍生的n- c17和n-C19外，短链正构烷烃n- c12 ~ n-C20的δD值北高南低。大气降水与短链正构烷烃之间氢的同位素分馏ε值从N向S递增超过100‰，且与N - c16和N - c18年平均气温显著相关。这表明这些正构烷烃可能来自北方湖泊的不同来源，可能是由于石油污染，或者是通过不同的生化途径合成的。藻类源的n- c17和n- c19烷烃，水生植物源的n- c21和n- c23烷烃，陆源源的n-C25、n-C27、n-C29和n- c31长链烷烃与大气水、湖泊水和年平均气温的δD值有明显的相关性，说明它们很好地记录了大气水的δD值。n- c17与大气水的平均氢同位素分馏值εC17/wof - 157‰（SD = 13）在不同气候和湖泊环境的大范围内基本稳定，表明环境因子对该生化分馏的影响较小。这表明n- c17的δD值适合重建源水的同位素组成。长链正构烷烃与水的平均分馏为- 128‰（SD = 12）。两个ε值的平均差值为31‰，可能是由于叶片水分中氘的蒸发富集所致。如果这是对富集的唯一影响，陆源化合物和水生化合物δD值的差异可能适合于重建湖泊环境的陆源蒸散发。
Hydrogen isotope ratios were measured on n-alkanes (n-C12to n-C31) extracted from recent lake surface sediments along a N-S European transect to test if modern climate variability is recorded in these biomarkers. δD values of the n-alkanes are compared to δD values of meteoric water from the IAEA-GNIP database spanning a range from −119‰ in northern Sweden to −41‰ in southern Italy, to lake water δD values, and to mean annual temperatures, varying between −2.0°C in the north and 13.7°C in the south. δD values of the short-chained n-alkanes n-C12to n-C20, excluding algal derived n-C17and n-C19, are higher in the north and lower in the south. The isotopic fractionation ε for hydrogen between meteoric water and the short-chained n-alkanes is increasing from N to S by more than 100‰ and is significantly correlated to mean annual temperature for n-C16and n-C18. This suggests that these n-alkanes may originate from a different source in the northern lakes, possibly due to petroleum contamination, or are synthesized using a different biochemical pathway. The n-C17and n-C19alkanes of algal origin, the n-C21and n-C23alkanes originating from water plants, and the long-chain n-alkanes n-C25, n-C27, n-C29, and n-C31of terrestrial origin, clearly correlate with δD values of meteoric water, lake water, and mean annual temperature, indicating that they excellently record the δD value of meteoric water. The mean hydrogen isotope fractionation εC17/wof −157‰ (SD = 13) between n-C17and meteoric water is fairly constant over the wide range of different climates and lake environments, suggesting only minor influence of environmental factors on this biochemical fractionation. This suggests that δD values of n-C17are suitable to reconstruct the isotopic composition of source water. The mean fractionation between the long-chain n-alkanes and water is −128‰ (SD = 12). The mean difference of 31‰ between both ε values is likely due to evaporative enrichment of deuterium in the leaf water. If this is the only influence on the enrichment, the difference between the δD values of terrestrial and aquatic compounds might be suitable to reconstruct terrestrial evapotranspiration of the lake environment.