基于XRF连续扫描的云南抚仙湖沉积物元素特征及环境意义
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摘要
X射线荧光光谱(X-ray fluorescence, XRF)岩芯扫描仪具有前处理简单、非破坏性、连续高效测量及高精度等优势,已被广泛的应用于海洋、浅水湖泊及黄土等高分辨率的气候与环境变化研究中。然而,深水湖泊的水动力过程、物质迁移转化等与浅水湖泊均存在显著差异,且对深水湖泊沉积物的XRF连续元素扫描研究还有待进一步开展。通过对我国西南地区滇中盆地抚仙湖沉积物XRF元素连续扫描,并与电感耦合等离子体发射光谱仪(inductively coupled plasma optical emission spectrometry, ICP-OES)和质谱仪(inductively coupled plasma mass spectrometry, ICP-MS)元素分析方法对比,结合年代学与其他环境代用指标,探讨了滇中深水湖泊沉积物XRF连续扫描的元素特征所指示的环境意义。研究结果表明:(1)除P, Ge和Cr元素外, XRF元素连续扫描结果与ICP-OES/ICP-MS分析具有较好的相关性(p<0.01);其中K, Ca, Ti, Fe, Rb和Zr元素的相关系数大于0.85。(2)元素的主因子分析发现,主成份1和2的方差贡献分别为76.31%和10.37%,其成分1远大于成分2,且K, Fe, Ti, Zn, Rb和Zr等元素的公因子载荷大于0.9,指示了抚仙湖流域的侵蚀强度是主要影响抚仙湖沉积过程的控制要素,其对流域内气候环境变化及人类活动强度具有较好的指示意义。(3)结合抚仙湖其他环境代用指标(粒度、总有机质含量),重建了距今5 200年以来的滇中环境变化与人类活动历史。在距今约2200年,人类活动(耕作农业、砍伐森林等)的显著加强使得流域内植被减少、土壤侵蚀加剧,进入湖盆中的外源碎屑物增加,沉积物中元素含量显著增高。研究结果将为XRF技术在深水湖泊中的应用,以及开展环境演变与人类活动影响的高分辨率研究提供有效的借鉴。
X-ray fluorescence(XRF) core scanning has the advantages of simple pre-processing, non-destructive and high precision, and it has been widely used in the high-resolution environmental change studies of oceans, shallow lakes and loess. However, the hydrodynamic processes and the material translocation and transformation of deep lakes are apparently different from shallow lakes, and the research of XRF continuous scanning in deep lake is still relatively few. Based on the analysis of XRF elements continuous scanning of Fuxian Lake sediments, located in the central Yunnan plateau basin, the characteristics of geochemical elements and its environmental significance have been discussed, combined with comparative analysis of XRF core scanning and inductively coupled plasma optical emission spectrometry(ICP-OES) and mass spectrometry(ICP-MS) method, chronology and other environmental proxies. The results obtained are as follows:(1) There is a close correlation of geochemical elements between XRF core scanning and the ICP-OES/ICP-MS methods(p<0.01), except for the element P, Ge and Cr. The correlative coefficient of K, Ca, Ti, Fe, Rb and Zr is more than 0.85.(2) The result of principal factor analysis shows that the variance contribution rates of principal component 1 and 2 are 76.31% and 10.37%, respectively. The principal component 1 is much greater than component 2. The factor loading of K, Fe, Ti, Zn, Rb and Zr exceed 0.9. It indicates that the erosion intensity of Fuxian Lake catchment is the main control factor of the deposition process, and the exogenous detrital elements have a better indicative implications for regional environment change and human activity intensity.(3) Based on the geochemical element analysis by using XRF core scanning and other climate proxies of the lacustrine sediments, the environmental changes and human activities of the central Yunnan plateau basin have been reconstructed since 5 200 cal. a BP. The intensified human activity(e. g. agricultural farming, extensive deforestation) caused a heavy loss of soil of the lake catchment since 2 200 cal. a BP., and the significant increased element contents(e. g. Ti, Rb, Zr) indicated that a large amount of exogenous detritus had been carried into the lake basin. The results of this study can provide references and experience for the application of XRF technology in deep lake, and it will be helpful for the study of high-resolution environmental change and human activities in the Asian southwest monsoon.
X-ray fluorescence(XRF) core scanning has the advantages of simple pre-processing, non-destructive and high precision, and it has been widely used in the high-resolution environmental change studies of oceans, shallow lakes and loess. However, the hydrodynamic processes and the material translocation and transformation of deep lakes are apparently different from shallow lakes, and the research of XRF continuous scanning in deep lake is still relatively few. Based on the analysis of XRF elements continuous scanning of Fuxian Lake sediments, located in the central Yunnan plateau basin, the characteristics of geochemical elements and its environmental significance have been discussed, combined with comparative analysis of XRF core scanning and inductively coupled plasma optical emission spectrometry(ICP-OES) and mass spectrometry(ICP-MS) method, chronology and other environmental proxies. The results obtained are as follows:(1) There is a close correlation of geochemical elements between XRF core scanning and the ICP-OES/ICP-MS methods(p<0.01), except for the element P, Ge and Cr. The correlative coefficient of K, Ca, Ti, Fe, Rb and Zr is more than 0.85.(2) The result of principal factor analysis shows that the variance contribution rates of principal component 1 and 2 are 76.31% and 10.37%, respectively. The principal component 1 is much greater than component 2. The factor loading of K, Fe, Ti, Zn, Rb and Zr exceed 0.9. It indicates that the erosion intensity of Fuxian Lake catchment is the main control factor of the deposition process, and the exogenous detrital elements have a better indicative implications for regional environment change and human activity intensity.(3) Based on the geochemical element analysis by using XRF core scanning and other climate proxies of the lacustrine sediments, the environmental changes and human activities of the central Yunnan plateau basin have been reconstructed since 5 200 cal. a BP. The intensified human activity(e. g. agricultural farming, extensive deforestation) caused a heavy loss of soil of the lake catchment since 2 200 cal. a BP., and the significant increased element contents(e. g. Ti, Rb, Zr) indicated that a large amount of exogenous detritus had been carried into the lake basin. The results of this study can provide references and experience for the application of XRF technology in deep lake, and it will be helpful for the study of high-resolution environmental change and human activities in the Asian southwest monsoon.
引文
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