Eight atmospheric carbon dioxide samples (as calcium carbonate—CaCO3—precipitates) from Lindesnes site (58ºN, 7ºE), belonging to 1963 and 1980 (four samples from each year) and stored at the National Laboratory for Age Determination (NTNU), have been reevaluated through radiocarbon (14C) analysis. Previous 14C results indicated the presence of a contaminant, which was not removed through different chemical cleansing procedures (e.g., hydrochloric acid—HCl and/or hydrogen peroxide—H2O2). Here, we present a follow up investigation using 14C step-combustion and Fourier-transform infrared spectroscopy (FTIR) analysis. Results from 14C data indicate unsuccessful removal of the contaminant, while further FTIR analysis displayed the presence of moisture. This finding alludes to the possibility that the contaminant is of ambient air-CO2 deeply embedded in CaCO3 powders (within clogged CaCO3 pores and/or bonded to the lattice). Samples were found exposed to air-CO2 and humidity. These conditions may have lasted for years, possibly even decades, leading to the 14C offsets detected here.

中文翻译：

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大气 CO2 样品中特隆赫姆 CaCO3 沉淀物的放射性碳阶梯燃烧氧化法和 FTIR 分析：进一步调查和见解


来自林德斯内斯遗址（北纬 58°，东经 7°）的 8 个大气二氧化碳样本（碳酸钙 - CaCO3 - 沉淀物），属于 1963 年和 1980 年（每年四个样本），储存在国家年龄测定实验室 (NTNU)，已被通过放射性碳（14C）分析重新评估。先前的 14C 结果表明存在污染物，该污染物无法通过不同的化学清洁程序（例如盐酸 - HCl 和/或过氧化氢 - H2O2）去除。在这里，我们使用 14C 分级燃烧和傅里叶变换红外光谱 (FTIR) 分析进行后续研究。 14C 数据结果表明污染物去除不成功，而进一步的 FTIR 分析显示存在水分。这一发现暗示污染物可能是环境空气中的二氧化碳，它深深嵌入碳酸钙粉末中（在堵塞的碳酸钙孔隙内和/或与晶格结合）。发现样品暴露在空气、二氧化碳和湿气中。这些条件可能持续了数年，甚至可能数十年，导致此处检测到的 14C 偏移。