河流沉积物原位XRF岩芯扫描结果定量估算的初步研究

原位XRF岩芯扫描技术具有前处理简单、破坏性小、快速和连续测量等优势, 是获取高分辨率元素记录的有效手段, 已被广泛应用于海洋、湖泊、三角洲和黄土等沉积物的古环境变化研究中, 但是针对河流沉积物的研究较少。本文利用原位XRF岩芯扫描技术对黄河内蒙古段河道钻孔沉积物进行了扫描分析。首先选取岩芯HDZ10( 40°8'3.9"N, 111°14'21.3"E) 进行X荧光元素实验测试条件分析, 在此基础上利用HDZ12( 40°12'59.91"N, 111°10'48.66"E) 探讨了河流沉积物原位XRF扫描技术的可行性及结果定量校正方法。对比元素强度值与元素含量的结果, 发现河流沉积物中Sr、Ca、Ti、Fe、Rb和Zr的元素强度值与元素含量相关系数较高。我们依据上述元素获得岩芯样品的强度值与元素含量的对数比率值, 并通过主轴回归分析方法得到相应的模型校正系数, 选取拟合度R2最高的校正系数建立了对数比率校正模型。校正后的ln(Zr/Ca)、ln(Fe/Ca)、ln(Ti/Ca)、ln(K/Ca)、ln(Rb/Ca)和ln(Sr/Ca)元素强度曲线与实测曲线基本一致, 最大程度地校正了原位XRF扫描分析结果, 较好地实现了河流沉积物的原位XRF扫描结果的定量估算。

PRELIMINARY STUDY ON CALIBRATION OF X-RAY FLUORESCENCE CORE SCANNER FOR QUANTITATIVE ELEMENT RECORDS IN THE YELLOW RIVER SEDIMENTS

XRF core scanning technique is an effective method to obtain the high resolution elemental record.The advantages of this method are nondestructive, fast, continuous measurement and simple pretreatment.XRF core scanning technique has been widely applied to investigate paleo-climate change in various environments such as marine, lacustrine, deltaic and loess deposits.This paper presents a preliminary research on application of XRF Core Scanner in fluvial deposit, with scientific objective to explore the optimal exposure time of fluvial sediments, and try to validate the results of XRF core scanning technique and transform scanning XRF dates to quantitative element concentrations through log-ratio calibration equation model(LRCE).In this study, we applied XRF core scanning technique to measure the sediment core HDZ10 ( 40°8'3.9"N, 111°14'21.3"E) from Inner Mongolia reach of the Yellow River with scanning time range from 10s to 45s.The results showed that the optional exposure time for K, Ca, Ti, Fe, Al and Si is 15s with a 10kV acceleration intensity, and 25s exposure time for Rb, Sr and Zr with a 30kV acceleration intensity.A whole sediment core HDZ12 (40°12'59.91"N, 111°10' 48.66"E) was continuously performed every 10mm and 20 samples(interval of 1m)were tested by X-ray fluorescence spectrometer in the Lanzhou University.We found that Sr and Ca had strong correlation coefficients comparing the results of XRF core scanner and the X-ray fluorescence spectrometer (R2>0.8), while Al and Si were weak correlation coefficients(0.4566 and 0.0687), which could be attributed to the influence of water content.We applied a log-ratio calibration model to explore the quantifying method of XRF core scanning technique.Seven elements(Sr, Ca, Ti, Fe, Rb, Zr and K)were used to calibrate the model parameters with a major axle regression analysis method.Our results showed that log-ratios of element intensities(Zr/Ca, Fe/Ca, Ti/Ca, K/Ca, Rb/Ca and Sr/Ca)were linearly correlated with log-ratios of element concentrations.Our results suggested that XRF core scanning technique associated with log-ratio calibration equation model could be a reliable approach for quantitative measurement of fluvial sediments.