| 引用本文: | 刘楠楠，杨胜利，刘维明，成 婷，陈 慧，唐国乾，李 帅，梁敏豪.2018.青藏高原东缘黄土石英光释光信号积分区间选择[J].地球环境学报,9(6):569-579 |
| LIU Nannan, YANG Shengli, LIU Weiming, CHENG Ting, CHEN Hui, TANG Guoqian, LI Shuai, LIANG Minhao.2018.Selection of integration time intervals for quartz optically stimulated luminescene (OSL) of loess in the eastern Tibetan Plateau[J].Journal of Earth Environment,9(6):569-579 |
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| 摘要: |
| 光释光信号积分区间的选择对等效剂量（D e ）的估算有重要影响。光释光衰减曲线并非单一的指数衰减，而由多个指数衰减函数组成，且每个衰减函数代表不同的信号组分。因矿物晶格陷阱类型不同，各组分有不同的衰减率、热稳定性等。本文对采自青藏高原东缘4个典型黄土分布区的黄土样品进行了系统的石英光释光组分分析和背景区间扣除研究。结果发现：（1）高原东缘黄土石英光释光信号由快、中、慢组分组成，并以快组分占主导，适合用单片再生剂量法测定等效剂量；（2）不同背景区间扣除对小于10 Gy样品等效剂量结果影响较小，误差范围内一致；（3）对大于10 Gy样品，选取早、晚不同背景区间扣除其等效剂量结果差异显著，两者差值占晚期背景扣除所得D e 值的10%—38%，且有随D e 值增加而增大的趋势，因此计算大于10 Gy样品D e 时应慎重选择积分区间。 |
| 关键词: 光释光信号组分 背景扣除 石英光释光 黄土 青藏高原 |
| DOI：10.7515/JEE182049 |
| CSTR：32259.14.JEE182049 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41472147）；兰州大学中央高校基本科研业务费专项资金（lzujbky-2017-ct05，lzujbky-2015-k10）；兰州大学西部环境教育部重点实验室开放基金 |
| 英文基金项目:National Natural Science Foundation of China (41472147); Fundamental Research Funds for the Central Universities (lzujbky-2017-ct05, lzujbky-2015-k10); Open Foundation of MOE Key Laboratory of Western China’s Environmental System, Lanzhou University |
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| Selection of integration time intervals for quartz optically stimulated luminescene (OSL) of loess in the eastern Tibetan Plateau |
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LIU Nannan, YANG Shengli, LIU Weiming, CHENG Ting, CHEN Hui, TANG Guoqian, LI Shuai, LIANG Minhao
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1. Key Laboratory of Western China’s Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China
2. CAS Key Laboratory of Mountain Hazards and Surface Process, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
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| Abstract: |
| Background, aim, and scope Selections of the integration time intervals for the quartz OSL is very important for estimating equivalent dose (D e). The traditional method, in calculating D e , is to select the first few seconds of OSL decay curve as the initial interval and subtract the last few seconds of decay curve as the background subtraction (e.g. 0—0.4 s, 19.9—24.9 s). In 2010, Cunningham and Wallinga suggested that the early background subtraction should be used in standard protocol. That is to select the first few seconds of OSL decay curve as the initial interval and subtract its followed few seconds interval as the background subtraction (e.g. 0—0.4 s, 0.4—1.4 s). Some recent studies also indicated the differences exist between D e values by using ‘early background’ and ‘late background’. To further illustrate the effect of different background interval subtractions on the equivalent dose, we have systematically studied loess samples collected from the four typical loess distribution areas in the eastern margin of the Tibetan Plateau. Materials and methods OSL samples were collected from 4 typical loess profiles using steel pipes, ~25 cm long and ~4 cm in diameter. Extraction of the quartz from samples and the OSL measurements were performed in the red light darkroom in the OSL laboratory of Chengdu Institute of Mountain Hazards and Environment, Chinese Academy of Sciences. First, the outside parts of sample, about 3—5 cm, were removed. After that, the 10% HCl and 30% H 2O2 were added in the residual samples to remove carbonates and organics. Next, the 38—63 μm of quartz components was extracted for measuring D e. After De of all samples were measured with the single aliquot regenerative-dose (SAR), we analyzed the components of quartz OSL signals of all samples and selection of integration time intervals using Analyst 4.53. Results The proportions of fast component of all samples are above 84%. For those samples of <10 Gy, the difference of average D e between A1 (0—0.4 s, 0.4—1.4 s) and A2 (0—0.4 s, 19.9—24.9 s) is only 0—0.32 Gy, which is 0—5% for the average De of A2. Compared to <10 Gy samples, to >10 Gy samples, the difference is 16.33—56.17 Gy, which is 10%—38% for the average D e of A2. Discussion For those samples with >10 Gy, we analyzed the changes of their natural and test dose signals after selecting the different background intervals to subtract. The average rate of change of natural signals is 13%—22% after selecting the different background intervals to subtract, and the average rate of change of test dose signals is 17%—31%. The difference of average rate of change of the two is 4%—15%. Thus, we infer that it may be caused by the large difference of average D e between A1 and A2 for >10 Gy samples. The further component analysis of test dose shows that a significant proportion of unstable medium components are included in test dose signals, so resulting in a higher D e when calculated with the early background subtraction (0—0.4 s, 0.4—1.4 s). Conclusions The fast component is the dominant signal of quartz OSL signals of loess in the eastern margin of Tibetan Plateau, and the equivalent dose can be measured using the SAR procedure. The effect of different background intervals subtraction on D e results of <10 Gy samples is small, and the error range can be negligible. But for >10 Gy samples, the effect is significant. It also shows that the difference of D e between A1 and A2 seems to be increasing with the increase of the equivalent dose. Recommendations and perspectives The integral intervals should be carefully selected when calculating D e of >10 Gy samples. To calculate OSL age of those samples, further studies are needed for selecting a more appropriate method of background subtractions, such as using independent age control or comparing to the result of measuring fast component only. |
| Key words: components of OSL signals background subtraction quartz OSL loess Tibetan Plateau |
