【作者】 王君；

【导师】 卫蓉；

【作者基本信息】 昆明理工大学 ， 环境工程， 2009， 硕士

【摘要】 本文以昆明荷叶山柱状沉积物为研究对象,通过对沉积物中常量元素、微量元素包括稀土元素在内的四十余种元素进行定量分析,结合沉积学、地球化学、14C建立的年代序列等来探讨昆明荷叶山柱状沉积物的环境意义,重建昆明北部地区末次冰盛期(始于1.8万年前)以来的气候环境演变过程。本研究采用ICP-MS测定了荷叶山柱状沉积物中微量元素：Li、Rb、Cs、Be、Sr、Ba、Se、Ga、Th和U,重金属元素：Cr、Ni、Pb、Co以及稀土元素La、Ce、Pr、Pm、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu。用ICP-AES测定了常量元素：Al、Ti、Ca、Mg、Fe和Mn,用AAS测定了Na。研究表明：常量元素中Na、Ti波动较剧烈。Na/Al, Mg/Al, Ca/Al的比率呈现出相似的变化趋势,在距今1万年前左右,这些元素的比率相比1万年前增大,而且1万年以后变化显著,这与末次冰消期(1.5万年前-1.1万年前)的结束全新世(白1.1万年前至今)的开始有关。Mg/Ca比值指示了昆明北部气温的变化。该比值显示在17.8m～10.6m(20～11kaBP)之间,该段时期温度较低；在10.6m～2m(11～2kaBP)之间,Mg/Ca比值开始逐渐增大,在8kaBP时突然增大,表明昆明北部气温逐渐升高,但温度仍有波动。在2m-表层(2kaBP～至今)之间,Mg/Ca比值突然降低,表明温度降低。微量元素中Rb/Sr比值的大小反映了环境的气候条件。结合14C定年结果和沉积学等,恢复了昆明北部末次冰盛期以来的气候环境变化过程17.8m～15.2m(20～17kaBP):Rb/Sr比值最低,属于末次冰盛期的干燥寒冷气候；15.2m～10.2m(17～11kaBP):Rb/Sr比值波动地逐渐增大,属于末次冰消期的寒冷干燥向温暖湿润过渡阶段；10.2m～4.6m(11～5kaBP):进入全新世大暖期；4.6m-表层(5kaBP～至今)：Rb/Sr比值突然降低,为全新世干冷时期。荷叶山柱状沉积物中稀土元素的球粒陨石标准化曲线趋势基本一致,δEu的平均值为0.72,表现出弱的Eu负异常,δCe的平均值为7.12。∑LREE/∑HREE比值大于1,说明荷叶山沉积物稀土元素分馏较明显。La/Yb、La/Sm和Gd/Yb均大于1,说明荷叶山沉积物中轻稀土元素富集。ΣREE含量的变化与气候环境温暖湿润、寒冷干旱等相对应。ΣREE含量的变化与末次冰盛期以来的几次气候变化相对应。18～17 kaBP:末次冰盛期的干燥寒冷阶段,与玉木冰期Ⅱ对应；15～12 kaBP:温度波动地上升,与晚更新世玉木冰期的晚冰期和新仙女木时期相对应。更多还原

【Abstract】 This paper used a geochemical analysis of core sediments from a twenty-meter column taken from Lotus Mountain in Kunming, Yunnan, China to reconstruct environmental conditions over the past 20 kyr. ICP-MS operation condition was used in the determination of trace elements (Li, Rb, Cs, Be, Sr, Ba, Se, Ga, Th and U), heavy metals (Cr, Ni, Pb and Co), and REEs (La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu). ICP-AES was used to determine Al, Ti, Ca, Mg, Fe and Mn. Na was determined by AAS. The age of the sediment column was determined by 14C analysis.The general trend for Na/Al, Mg/Al and Ca/Al ratios were similar as well as higher than they were 10 thousand years ago, which correlates with the gradually warming climate during the Holocene (dated from 11 thousand years ago).The Mg/Ca ratio was used as an indicator of temperature change. The results indicated that temperatures between 20-11kaBP gradually decreased before starting to warm from 11-2kaBP. The last 2,000 years have seen temperatures once again decreasing.The Rb/Sr ratio recorded similar a pattern with temperatures decreasing between 20～17kaBP, warming between 17～115kaBP, then becoming particularly warm between 11 to 5kaBP before cooling during the last 5,000 years.Chondrite patterns for the REEs were all similar. The meanδEu value was 0.72, which showed the core sediments to be part of the negative Eu anormally, while the meanδCe value was 7.12, which showed the core sediments as a positive Ce anormally. Values for the∑LREE/∑HREE ratio showed that the sediments were rich in LREE Futhermore, the individual element ratios for La/Yb, La/Sm and Gd/Yb also suggested the column to be rich in LREE.Changes in the∑REE of the core sediments also correlated well with climate changes during the last Glacial Maximum(LGM). From 18 to 17 kaBP it was the cold while from 15～12 kaBP it was warming.更多还原