海洋沉积物<sup>32</sup>Si测年方法研究

詹晓青; 李超; 贾磊; 张金鹏; 刘广山

doi:10.3969/j.issn.0253-4193.2019.02.006

海洋沉积物³²Si测年方法研究

doi: 10.3969/j.issn.0253-4193.2019.02.006

1.
厦门大学环境与生态学院, 福建厦门 361102
2.
厦门大学海洋与地球学院, 福建厦门 361102
3.
中国地质调查局广州海洋地质调查局, 广东广州 510075

基金项目: 中国地质调查局项目（GZH201500207，GZH201300503，DD20160146）。

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出版历程
- 收稿日期: 2018-05-30
- 修回日期: 2018-10-24

Study on dating method of ³²Si in marine sediments

1.
College of Environment & Ecology, Xiamen University, Xiamen 361102, China
2.
College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
3.
Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 510075, China

摘要

摘要: 天然³²Si是宇宙射线成因的，随着降水进入湖泊或海洋，被硅质生物摄取后最终存在于生物硅中。³²Si来源单一，生产速率相对恒定，半衰期为150 a，可测年的时间尺度为100~1 000 a，是该时间尺度最合适的测年核素，填补了百年到千年时间尺度测年方法的空白。本文建立了海洋沉积物³²Si的测量方法，主要步骤为：（1）样品前处理；（2）生物硅的分离与纯化；（3）生物硅样品中磷的分离与纯化；（4）³²P的制样与β计数测量。全程通过硅钼蓝和磷钼蓝分光光度法监测实验过程硅和磷的损失情况，对南沙海域采集的沉积物岩心进行研究，得到南沙海域沉积物岩心³²Si的平均活度为16.60 mBq/kg，范围值为8.39~33.34 mBq/kg；³²Si在SiO₂中的平均比活度为0.356 Bq/kg，³²Si的核素丰度平均值为1.29×10^-16（³²Si/SiO₂）；根据岩心³²Si活度估算得深水区（水深1 335~1 537 m）和浅水区（121~141 m）岩心的沉积速率分别为0.106 cm/a、0.191 cm/a；根据³²Si活度计算³²Si的平均沉降通量为2.14×10^-6 Bq/（cm²·a），与参考文献的结果较为吻合。
- ³²Si /
- 生物硅 /
- 年代测定 /
- 南沙海域 /
- 沉积物岩心
Abstract: ³²Si generates from the spallation reaction of cosmic rays and argon in atmosphere, which is ingested by siliceous organisms such as diatoms after falling into the lakes and sea from atmosphere. The cosmogenic radioactive isotope ³²Si, with a half-life of approximately 150 a, represents an excellent dating tool for the age range of approximately 100-1 000 a. ³²Si, with a single source and a constant production rate, is of importance to the ancient environments and paleoclimatology. The method of determining ³²Si activity in the marine sediments was established. The main steps were as follows:(1) sample pretreatment; (2) separating and purifying biogenic silica; (3) separating and purifying phosphorus from biogenic silica; (4) preparation of phosphorus and counting ³²P by β counter. The experimental process was monitored by acidic silicomolybdenum blue spectrophotometry and phosphomolybdenum blue spectrophotometry to control loss of silicon and phosphorus during the process. The specific activity of ³²Si in sediments from Nansha sea area varies from 8.39 mBq/kg to 33.34 mBq/kg, with 16.60 mBq/kg as the mean value. The average specific activity of ³²Si in SiO₂ is 0.356 Bq/kg. The average specific abundance of ³²Si in biogenic silica is 1.29×10^-16 (³²Si/SiO₂). Sedimentary rates of sediment cores from deep water (1 335-1 537 m) and shallow water (121-141 m) are 0.106 cm/a and 0.191 cm/a respectively. The average setting flux of ³²Si is 2.14×10^-6 Bq/(cm²·a), within the range of references.
- ³²Si /
- biogenic silica /
- dating /
- Nansha sea area /
- sediment core

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参考文献(30)

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