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首页> 外文期刊>Quaternary geochronology >The efficiency of charcoal decontamination for radiocarbon dating by three pre-treatments - ABOX, ABA and hypy
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The efficiency of charcoal decontamination for radiocarbon dating by three pre-treatments - ABOX, ABA and hypy

机译：通过三种预处理（ABOX，ABA和hypy）进行木炭净化放射性碳定年的效率

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摘要

Here we report results of a direct inter-comparison of the ability of three radiocarbon pre-treatment techniques to remove radiocarbon contamination introduced by exposing known-radiocarbon-free charcoal made at three different temperatures (300, 400 and 500 ℃) to environmental contamination on a rainforest floor for one to three years. The initial charcoal had no measureable radiocarbon, but ~(14)C activity increased after environmental exposure to ~1 pMC after one year (apparent age of ~40,000 yrs BP) and ~5 pMC after three years (apparent age of ~25,000 years). For the 400 and 500 ℃ samples, all techniques were able to reduce contamination by >90%. Acidebase oxidation (ABOX) provided the most reliable decontamination, reducing the radiocarbon activity of the one year samples to background, and reducing the radiocarbon activity of the three year samples to 0.04 ± 0.02 pMC or less (apparent age>56,900 yrs BP). The performance of ABOX was superior to that of both acid-base-acid (ABA) and hydrogen pyrolysis (hypy) treatments, with ABA performing better than hypy in most cases. No technique was able to fully remove decontamination from the 300 ℃ charcoal (although ABOX again removed the most contamination), likely due to the incompletely pyrolized nature of the charcoal which is dominated by aromatic clusters of small ring size. All the techniques rely on removing contaminant carbon faster than indigenous carbon and this condition is not met in the case of charcoal produced at temperatures below ~350 ℃. While all pre-treatments are useful for routine sample processing, the results suggest that ABOX is the only technique that can provide reliable decontamination of charcoal of an age close to the dating limit of the radiocarbon dating technique.
机译：在这里，我们报告了三种放射性碳预处理技术去除放射性碳污染能力的直接比较结果，这些技术是通过将三种不同温度（300、400和500℃）下制得的已知无放射性碳的木炭暴露于环境污染而产生的。一到三年的雨林地板。最初的木炭没有可测量的放射性碳，但是在环境暴露于一年后（〜40,000 yrs BP的年龄）〜1 pMC和三年后（〜25,000岁的表观年龄）〜5 pMC的环境暴露后，〜（14）C活性增加。 。对于400和500℃的样品，所有技术都能将污染减少90％以上。酸碱氧化（ABOX）提供了最可靠的净化效果，将一年样品的放射性碳活性降低到本底，并将三年样品的放射性碳活性降低到0.04±0.02 pMC或更低（表观年龄> 56,900 yr BP）。 ABOX的性能优于酸碱酸（ABA）和氢热解（hypy）处理，在大多数情况下ABA的性能均优于hypy。没有任何技术能够从300℃的木炭中完全去除污染（尽管ABOX再次去除了最大的污染），这很可能是由于木炭的不完全热解性质所致，其主要是小环尺寸的芳香簇。所有技术都依靠比本地碳更快地去除污染物的碳，并且在低于约350℃的温度下生产木炭的情况下无法满足此条件。尽管所有预处理都可用于常规样品处理，但结果表明，ABOX是唯一可提供可靠年龄的木炭去污的技术，该年龄接近放射性碳定年技术的定年极限。

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