长江三角洲平原湖沼沉积物XRF岩芯扫描结果的可靠性分析

摘要

对长江三角洲顶部湖沼相沉积为主的X J02孔(32°19 ′57″N,119°16 ′22″E)进行XRF全岩芯扫描(XRF-cps)分析,同时选取70个样品利用X射线荧光光谱仪(XRF-ppm)进行元素含量测定.通过对两种测试方法所获结果的对比及相关性分析,探讨了XRF岩芯扫描方法测定元素含量的可靠性及其影响因素.结果表明:两种方法所测得的6种元素Ti,Zn,Rb,Sr,Fe和Ca的相关系数很高,XRF扫描强度变化可以很好地反映其含量的变化；XRF扫描强度受含水量的影响,尤其对原子量较小的元素Si等影响比较明显；对于含量较低的元素P和Pb,XRF扫描强度不能真实的反映沉积物中的元素含量.%X-ray fluorescence(XRF)core scanning is increasingly accepted as an effective method for high-resolution elemental records because of its rapid,non-destructive and continuous measurements.In order to know the reliability of XRF core scanning,we compare the measurement results from core scanning method with those results from the well-acceptable traditional X-ray fluorescence spectrometer.The materials we used are the sediments of core X J02 (32 ° 19′57″N,119°16′22″E,core length 31.8m) from the Yangtze River delta.The core sediments is mainly consist of silt and clay.We measure the whole core using XRF core scanner in Tongji University.At the same time,70 samples (intervals of 45cm) from the core XJ02 are selected for element measurement by traditional X-ray fluorescence spectrometer.Comparing the results of twelve detectable elements from two methods,and carrying out a correlation analysis on each element from the XRF core scanner and the conventional X-ray fluorescence spectrometer,we group three types of elements base on the correlation coefficients (R2):1) Type one includes Ti,Zn,Rb,Sr,Fe and Ca with high correlation (R2 ＞0.8) ; 2) Type two includes Zr,Al and K that were weaker correlated (0.5 ＜R2 ＜0.8) ; 3)Type three includes Pb,Si and P,which are poorly correlated (R2＜0.2).Type one should be more effective for XRF core scanning method on delta area.On the other hand,the XRF core scanner measurements could be affected by sediment properties,such as the water content,grain size and surface roughness.In this paper,we compare the correlation coefficient of each element results from two measurement methods before and after controlling the influence of water content,we find that the correlation coefficient would increase after control water content influence,especially to some light element such as element Si.The result indicate that XRF core scanner date of six elements (Ti,Zn,Rb,Sr,Fe and Ca)can reflect the element content confidently.The content of element P and Pb is low,the XRF core scanner date can't reflect the low element content accurately.It is suggested by the experimental result that XRF core scanning date is reliable for many element in delta sediments,and XRF core scanning has a lot of advantages comparing with conventional test methods,it could be widely used in paleoclimate and paleoenvironment research in delta tract.