张家武,,
毛春晖,
张延利,
周姗,
杨盼盼
兰州大学资源环境学院, 西部环境教育部重点实验室, 甘肃 兰州 730000
基金项目: 国家自然科学基金项目（批准号：41771212）和兰州大学中央高校基本科研业务费专项项目（批准号：lzujbky-2017-it81）共同资助
详细信息
作者简介: 张玉枝, 女, 29岁, 博士研究生, 湖泊沉积与环境变化研究, E-mail:zhangyzh15@lzu.edu.cn
通讯作者: 张家武, E-mail:jwzhang@lzu.edu.cn
中图分类号: P941.78;P595收稿日期:2020-01-28
修回日期:2020-04-21
刊出日期:2020-09-30
Accuracy assessment and calibration of the impact of water content and structure of lake sediments on the XRF scanning data—A case study of Aweng Co in the Tibetan Plateau
Zhang Yuzhi,Zhang Jiawu,,
Mao Chunhui,
Zhang Yanli,
Zhou Shan,
Yang Panpan
Key Laboratory of Western China's Environmental Systems, Ministry of Education, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 73000, Gansu
More Information
Corresponding author: Zhang Jiawu,E-mail:jwzhang@lzu.edu.cn
MSC: P941.78;P595--> Received Date: 28 January 2020
Revised Date: 21 April 2020
Publish Date: 30 September 2020
摘要
摘要:本研究利用XRF岩芯扫描仪对青藏高原西部的阿翁错湖泊沉积物进行高分辨率元素扫描。通过与传统X射线荧光光谱仪测试结果进行相关分析，对XRF元素扫描结果中常用元素的可靠性和准确性进行评估，并通过标准化多项式校正法、多元对数比校正法及标准化中位数校正法对其进行校正。结果表明，元素Ti和Fe的XRF岩芯扫描元素强度与传统XRF方法测试的元素含量显著相关，其结果可靠，能够反映元素的真实变化过程，无需对其校正。Al、Si和K元素强度受到岩芯含水量等因素的影响，Ca元素强度易受到岩芯裂隙的影响，在使用前需要对其进行校正。不同校正方法的校正结果对比表明，标准化多项式校正方法对湖泊沉积物中Al、Si、K和Ca元素强度的校正效果最好。当岩芯含水量变化较大造成岩芯表面出现裂隙等结构变化时，建议进行分段校正。
关键词: 湖泊沉积/
XRF岩芯扫描/
校正/
阿翁错
Abstract:X-ray fluorescence (XRF) scanning technology is widely used in determining the rough content of elements in sediments as it has advantages of rapid measurements, no damage to samples and high resolutions for environmental studies. However, the scanned intensities of some elements are often biased by water content and sedimentary structure of sediments, which need to be assessed and calibrated before being used in environmental researches. In order to evaluate the accuracy and reliability of the XRF scanning data, we chose core sediments from an alpine closed saline lake (salinity is 29.5 g/L and pH is 9.2), Aweng Co (32.70°~32.82°N, 81.63°~81.80°E; 4430 m a.s.l.), in western Tibet to compare the XRF scanning data and the traditional accurate XRF measurements for assessment and calibration. Two sediment cores, AWC2015A and AWC2015B (32.745°N, 81.757°E, 4430 m a.s.l, bedrocks in the catchment are Cretaceous granite and Jurassic metamorphosed sandstone), retrieved from the central part of the lake at a water depth of 6 m using a piston corer on a UWITEC platform in July 2015, were combined to a composite sequence of 445 cm in length. XRF scanning was conducted on one half of the sediment core using the Avaatech XRF core scanner at 2 mm resolution. The accuracy of the XRF scanning data are evaluated by comparing with the results of traditional XRF analyzer (Epsilon 3XL XRF analyzer) with 1 cm-resolution samples from section 130.5~189.5 cm of the core (58 samples) and another 19 samples distributed evenly along the core. The average of three XRF scanning data that cover one traditional XRF data are used to compare in this study. Then calibrations are conducted using three different methods, including the normalized polynomial-scaled (NPS) calibration, the multivariate log-ratio calibration (MLC), and the normalized median-scaled (NMS) calibration.
The results show that the XRF-scanned elemental intensities of Ti and Fe are significantly correlated with the measured elemental contents by traditional XRF equipment, indicating the intensities of Ti and Fe are reliable and thus can be used without calibrations. The intensities of Al, Si and K are affected by the water content, and the intensity of Ca is influenced by the cracks in the sediments, suggesting the intensities of Al, Si, K and Ca should be properly calibrated before being used for climatic and environmental change studies. Comparisons of the results calibrated by three different methods suggested that the performance of the NPS calibration is the best and it resulted in consistent variations of the calibrated Al, Si, K and Ca with their measured contents. Separate calibrations are recommended when the structures of the sediment surface changed (e.g. cracks) during the process of scanning, which may be caused by water loss after exposure in the air during the pretreatments.
Key words:lake sediments/
XRF scanning/
calibration/
Aweng Co
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