{"title":"评估正烷烃化合物特定辐射碳小规模分析中的 14c 空白值","authors":"Kristina Reetz, Ronny Friedrich, Jago J Birk, Wilfried Rosendahl, Sabine Fiedler","doi":"10.1017/rdc.2024.26","DOIUrl":null,"url":null,"abstract":"Compound-specific radiocarbon analysis (CSRA) provides the possibility to date sample material at a molecular level. <jats:italic>N</jats:italic>-alkanes are considered as specific compounds with high potential to CSRA. As these compounds originate from plant waxes, their radiocarbon (<jats:sup>14</jats:sup>C) analysis can provide valuable information about the age and origin of organic materials. This helps to reconstruct and understand environmental conditions and changes in vegetation in the past. However, CSRA has two main challenges: The small sample size of CSRA samples, making them extremely sensitive to blank effects, and the input of unknown amounts of extraneous carbon during the analytical procedure. According to the previous study from Sun and co-workers, we used different-sized aliquots of leaves <jats:italic>Fagus sylvatica</jats:italic> (<jats:italic>n</jats:italic>C27, <jats:italic>n</jats:italic>C29) and <jats:italic>Festuca rubra agg</jats:italic> (<jats:italic>n</jats:italic>C31, <jats:italic>n</jats:italic>C33) as modern standards and two commercial standards (<jats:italic>n</jats:italic>C26, <jats:italic>n</jats:italic>C28) as fossil standards for blank determination. A third commercial standard (<jats:italic>n</jats:italic>C27) with predetermined radiocarbon content of F<jats:sup>14</jats:sup>C = 0.71 (<jats:sup>14</jats:sup>C age of 2700 BP) serves to evaluate the blank correction. We found that the blank assessment of Sun and co-workers is also applicable to <jats:italic>n</jats:italic>-alkanes, with a minimum sample size of 15 µg C for dependable CSRA dates. We determined that the blank introduced during the analytical procedure has a mass of (4.1 ± 0.7) µg carrying a radiocarbon content of F<jats:sup>14</jats:sup>C = 0.25 ± 0.05. Applying the blank correction to a sediment sample from Lake Holzmaar (Germany) shows that all four isolated <jats:italic>n</jats:italic>-alkanes have similar <jats:sup>14</jats:sup>C ages. However, the bulk material of the sediment and branches found in the sediment core are younger than the CSRA dates. We conclude that the disparity between the actual age of analysed organic material and the age inferred from radiocarbon results, which can occur in sediment traps due to delayed deposition, is the reason for the CSRA age.","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"30 1","pages":""},"PeriodicalIF":2.0000,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"ASSESSING 14C BLANKS IN THE SMALL-SCALE ANALYSIS OF N-ALKANE COMPOUND-SPECIFIC-RADIOCARBON-ANALYSIS\",\"authors\":\"Kristina Reetz, Ronny Friedrich, Jago J Birk, Wilfried Rosendahl, Sabine Fiedler\",\"doi\":\"10.1017/rdc.2024.26\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Compound-specific radiocarbon analysis (CSRA) provides the possibility to date sample material at a molecular level. <jats:italic>N</jats:italic>-alkanes are considered as specific compounds with high potential to CSRA. As these compounds originate from plant waxes, their radiocarbon (<jats:sup>14</jats:sup>C) analysis can provide valuable information about the age and origin of organic materials. This helps to reconstruct and understand environmental conditions and changes in vegetation in the past. However, CSRA has two main challenges: The small sample size of CSRA samples, making them extremely sensitive to blank effects, and the input of unknown amounts of extraneous carbon during the analytical procedure. According to the previous study from Sun and co-workers, we used different-sized aliquots of leaves <jats:italic>Fagus sylvatica</jats:italic> (<jats:italic>n</jats:italic>C27, <jats:italic>n</jats:italic>C29) and <jats:italic>Festuca rubra agg</jats:italic> (<jats:italic>n</jats:italic>C31, <jats:italic>n</jats:italic>C33) as modern standards and two commercial standards (<jats:italic>n</jats:italic>C26, <jats:italic>n</jats:italic>C28) as fossil standards for blank determination. A third commercial standard (<jats:italic>n</jats:italic>C27) with predetermined radiocarbon content of F<jats:sup>14</jats:sup>C = 0.71 (<jats:sup>14</jats:sup>C age of 2700 BP) serves to evaluate the blank correction. We found that the blank assessment of Sun and co-workers is also applicable to <jats:italic>n</jats:italic>-alkanes, with a minimum sample size of 15 µg C for dependable CSRA dates. We determined that the blank introduced during the analytical procedure has a mass of (4.1 ± 0.7) µg carrying a radiocarbon content of F<jats:sup>14</jats:sup>C = 0.25 ± 0.05. Applying the blank correction to a sediment sample from Lake Holzmaar (Germany) shows that all four isolated <jats:italic>n</jats:italic>-alkanes have similar <jats:sup>14</jats:sup>C ages. However, the bulk material of the sediment and branches found in the sediment core are younger than the CSRA dates. We conclude that the disparity between the actual age of analysed organic material and the age inferred from radiocarbon results, which can occur in sediment traps due to delayed deposition, is the reason for the CSRA age.\",\"PeriodicalId\":21020,\"journal\":{\"name\":\"Radiocarbon\",\"volume\":\"30 1\",\"pages\":\"\"},\"PeriodicalIF\":2.0000,\"publicationDate\":\"2024-03-25\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Radiocarbon\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1017/rdc.2024.26\",\"RegionNum\":3,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Radiocarbon","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1017/rdc.2024.26","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
ASSESSING 14C BLANKS IN THE SMALL-SCALE ANALYSIS OF N-ALKANE COMPOUND-SPECIFIC-RADIOCARBON-ANALYSIS
Compound-specific radiocarbon analysis (CSRA) provides the possibility to date sample material at a molecular level. N-alkanes are considered as specific compounds with high potential to CSRA. As these compounds originate from plant waxes, their radiocarbon (14C) analysis can provide valuable information about the age and origin of organic materials. This helps to reconstruct and understand environmental conditions and changes in vegetation in the past. However, CSRA has two main challenges: The small sample size of CSRA samples, making them extremely sensitive to blank effects, and the input of unknown amounts of extraneous carbon during the analytical procedure. According to the previous study from Sun and co-workers, we used different-sized aliquots of leaves Fagus sylvatica (nC27, nC29) and Festuca rubra agg (nC31, nC33) as modern standards and two commercial standards (nC26, nC28) as fossil standards for blank determination. A third commercial standard (nC27) with predetermined radiocarbon content of F14C = 0.71 (14C age of 2700 BP) serves to evaluate the blank correction. We found that the blank assessment of Sun and co-workers is also applicable to n-alkanes, with a minimum sample size of 15 µg C for dependable CSRA dates. We determined that the blank introduced during the analytical procedure has a mass of (4.1 ± 0.7) µg carrying a radiocarbon content of F14C = 0.25 ± 0.05. Applying the blank correction to a sediment sample from Lake Holzmaar (Germany) shows that all four isolated n-alkanes have similar 14C ages. However, the bulk material of the sediment and branches found in the sediment core are younger than the CSRA dates. We conclude that the disparity between the actual age of analysed organic material and the age inferred from radiocarbon results, which can occur in sediment traps due to delayed deposition, is the reason for the CSRA age.
期刊介绍:
Radiocarbon serves as the leading international journal for technical and interpretive articles, date lists, and advancements in 14C and other radioisotopes relevant to archaeological, geophysical, oceanographic, and related dating methods. Established in 1959, it has published numerous seminal works and hosts the triennial International Radiocarbon Conference proceedings. The journal also features occasional special issues. Submissions encompass regular articles such as research reports, technical descriptions, and date lists, along with comments, letters to the editor, book reviews, and laboratory lists.