Towards Organic Carbon Isotope Records from Stalagmites: Coupled δ13C and 14C Analysis Using Wet Chemical Oxidation
Towards Organic Carbon Isotope Records from Stalagmites: Coupled δ13C and 14C Analysis Using Wet Chemical Oxidation
复制标题
石笋有机碳同位素记录：使用湿化学氧化进行 δ13C 和 14C 耦合分析
DOI：
10.1017/rdc.2019.35
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发表时间：
2019
期刊：
影响因子：
8.3
通讯作者：
Eglinton, Timothy I
中科院分区：
文献类型：
--
作者：
Lechleitner, Franziska A;Lang, Susan Q;Haghipour, Negar;McIntyre, Cameron;Baldini, James U;Prufer, Keith M;Eglinton, Timothy I
Speleothem organic matter can be a powerful tracer for past environmental conditions and karst processes. Carbon isotope measurements (δ13C and 14C) in particular can provide crucial information on the provenance and age of speleothem organic matter, but are challenging due to low concentrations of organic matter in stalagmites. Here, we present a method development study on extraction and isotopic characterization of speleothem organic matter using a rapid procedure with low laboratory contamination risk. An extensive blank assessment allowed us to quantify possible sources of contamination through the entire method. Although blank contamination is consistently low (1.7 ± 0.34 – 4.3 ± 0.86 μg C for the entire procedure), incomplete sample decarbonation poses a still unresolved problem of the method, but can be detected when considering both δ13C and 14C values. We test the method on five stalagmites, showing reproducible results on samples as small as 7 μg C for δ13C and 20 μg C for 14C. Furthermore, we find consistently lower non-purgeable organic carbon (NPOC) 14C values compared to the carbonate 14C over the bomb spike interval in two stalagmites from Yok Balum Cave, Belize, suggesting overprint of a pre-aged or even fossil source of carbon on the organic fraction incorporated by these stalagmites.
