Knowledge Resource Center for Ecological Environment in Arid Area
| 东亚风尘沉积中石英氧同位素组成特征及其对物源变化的指示 | |
| 其他题名 | Oxygen Isotope Compositions of Quartz in Aeolian Deposits from East Asia and Implication on Source Fluctuations |
| 闫龑 | |
| 出版年 | 2015 |
| 学位类型 | 博士 |
| 导师 | 孙有斌 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 东亚地区是世界范围内一个十分重要的风尘源区，其粉尘释放量达每年数百万吨。风尘可以形成沙尘暴等灾害性天气，并传播污染物和病原体。大气中的风尘又通过其直接和间接辐射效应影响地球系统辐射平衡，并通过表面效应吸附污染物，并促生大量二次污染物。风尘还可以给汇区的陆地和海洋生态系统提供营养元素，提高其生物生产力。这些气候和环境效应通过多种反馈机制相互关联，对全球气候和环境变化有着深远的影响。风尘研究是揭示地球系统各圈层之间相互联系和互动反馈机制的一个重要出发点，而风尘物源研究又是探讨风尘系统与气候环境系统的相互作用和反馈机制的基础。 东亚风尘物源研究已取得长足进展，但现代风尘和古风尘序列的物源变迁的理解仍有较多争论。本研究主要利用石英氧同位素(?18O)作为物源指标，系统地研究东亚各主要源区表土中<16和16-63微米的石英?18O空间分布特征，包括塔克拉玛干沙漠、蒙古南部戈壁沙漠、柴达木盆地、巴丹吉林沙漠、腾格里沙漠和毛乌素沙漠。同时开展了黄土高原现代粉尘和风尘序列中粗细粒级石英的?18O分析，并结合石英电子自旋共振信号强度和结晶度指数(ESR-CI)，试图从源汇对比的角度来探讨东亚的风尘物源及其变化特征。在进行现代风尘物源解译时，还结合气团后向轨迹追踪和遥感技术，提出了物源指标源汇对比、气团后向轨迹模拟及遥感影像辨识三位一体的现代风尘物源研究方法。取得的初步结果和认识如下： 在东亚主要粉尘源区中，粗细粒级组分石英?18O均显示出自蒙古戈壁至中国北方沙漠(包括巴丹吉林沙漠、腾格里沙漠和毛乌素沙漠)和柴达木盆地，再至塔克拉玛干沙漠的递增趋势，指示高温下形成的火成岩石英在蒙古戈壁样品中比重最高，在塔克拉玛干最低，在其它源区则处于二者之间。对不同源区剥蚀区的火成岩覆盖面积比率统计结果佐证了上述推断。利用源区粗细粒级石英?18O二元图，可以对来自蒙古戈壁、中国北方沙漠和塔克拉玛干沙漠的粉尘进行较明确的区分。综合ESR-CI指数，认为细粒级石英CI-?18O二元图可以对上述三个主要源区和来自不同源区的混合风尘做清晰的区分，而在石英ESR-CI-?18O三元图上，上述主要粉尘源区的区分度更高。 通过利用MODIS影像监测源区起尘范围、气团后向轨迹模拟气团运移路经及石英CI-?18O揭示源汇物质联系，对2012年春季西安的尘暴降尘进行了物源研究。结果表明，2012年春季侵袭西安的四次自然尘暴事件主要起源于塔克拉玛干沙漠、古尔班通古特沙漠和中国北方沙漠，而中国北方沙漠对其的物质贡献占主导地位。同时，西安还发生了四次人为源尘暴事件，其对西安降尘的贡献量占西安春季降尘总量的20%。MODIS影像和气团后向轨迹表明这四次人为源尘暴可能源自西安南部的区域性尘云，表明人为源尘暴事件可能与区域性灰霾事件有成因联系。这种多学科综合物源研究方法有效地回避了应用单一物源研究方法所带来的不确定性，提供了一个对尘暴风尘由源至汇动态迁移过程的物源追踪研究方法。 通过对庄浪和灵台剖面细粒石英?18O的分析，建立了晚渐新世以来黄土高原细粒级风尘石英?18O的时间变化序列。石英?18O的变化特征显示自晚渐新世以来细粒级风尘物源体系变化可分为六个阶段，包括24-20Ma、20-12Ma、12-7Ma、7-2.6Ma、2.6-1.2Ma及1.2Ma以来。其中，24-20Ma、12-7和1.2Ma以来，风尘物源体系不稳定，而其他三个阶段，物源体系较稳定。与区域和全球的古气候记录及区域构造证据对比表明，不同阶段黄土高原细粒级风尘物源变化的驱动因素不尽相同。其中，在24-20Ma和12-7Ma，可能主要由青藏高原北部隆升导致风尘物源不稳定振荡；而在1.2Ma以来，则可能主要由气候变化驱动引发风尘物源的大幅变动。 |
| 英文摘要 | East Asia is a very important aeolian dust source, whose dust emission amouts to several million tons per year. Entrained dust can result in disastrous sand dust storms, propagate pollutants and pathogens, adjust the radiation budget of the earth system through its direct and indirect radiative effects, absorp atmospheric pollutants and promote the generation of secondary pollutants, and boost the productivity of the terrestrial and oceanic ecosystems in sink areas by providing nutrious elements. These climatic and environmental effects of aeolian dust correlate with each other through a variety of feedback mechanisms, which casts profound influences on the global climate and environment changes. Researches on aeolian dust are thus an important starting point to unraveling the correlation and interaction mechanisms of the different spheres of the earth system. The provenance study of aeolian dust is, however, the foundation of aeolian dust studies. Provenance studies of aeolian dust in East Asia had made much progress. The interpretations of the provenance of modern aeolian dust and paleo-dust (loess) sequences, however, have not yet arrived at concordant conclusions. This study aims at providing new datasets and insights for this field by utilizing quartz oxygen isotope (?18O) as a source tracer. Quartz ?18O of the major dust sources in East Asia, including the Taklimakan desert, Mongolian Gobi, Badain Juran desert, Tengger desert, Mu Us desert, and Qaidam Basin, had been studied for both fine (<16?m) and coarse (16-63?m) dust fractions. Provenance of modern dust and loess sequences on the Chinese Loess Plateau (CLP) was then interpreted by conducting source-sink comparisons of quartz ?18O of the corresponding fractions, with the combination of quartz electronic spinning resonance signal intensity (ESR) and crystalinity index (CI). Upon interpreting the provenance of modern dust, this study proposes a multidisciplinary source-tracing method, including direct comparison of source proxies, back trajectory simulation of air masses, and the recognition of entrained dust by satellite images. Preliminary conclusions are as follows. Among the major dust sources of East Asia, quartz ?18O of both fractions shows consonant increasing trend from the Mongolian Gobi, to the northern Chinese deserts (i.e. Badain Juran, Tennger, and Mu Us deserts), and then to the Taklimakan desert, indicating the geological settings of the source areas are different. The coverage ratio survey of the igneous rocks in different sources corroborated the inference above. Using quartz ?18O of both fractions can differentiate dust from the Mongolian Gobi, Taklimakan desert and the northern Chinese deserts. Combination of quartz ?18O and ESR-CI from previous studies can help the differentiation. The bivariate plot of quartz ?18O and CI of fine fraction can make clear separation of dust from different sources, regardless of single-sourced or mixed dust, while the trivariate plot of quartz ?18O, ESR, and CI of fine fractions can further increase the differentiability. Combining dust entrainment monitoring by MODIS images, air mass transport route simulation by back trajectory modeling, and material linkage confirmation by source-sink quartz ?18O and CI comparisons, provenance study of dust storms happened in Xi’an in the spring of 2012 has been conducted. Results show that there were four natural dust storm events, which originated from the Taklimakan desert, Gurbantunggut desert, and the northern Chinese deserts, with the northern Chinese deserts being the primal sources. In the meantime, there were four anthropogenic dust storm events, which contributed around 20% of spring dustfall to Xi’an. MODIS images and air mass back trajectories indicate that these four events might originate from the regional dust cloud to the south of Xi’an, and possibly related with regional haze events. This multidisciplinary approach effiencently increases the accuracy of source |
| 中文关键词 | 东亚风尘 ; 石英氧同位素 ; 物源 ; 黄土高原 |
| 英文关键词 | East Asia Aeolian dust Quartz oxygen isotope Provenance Loess Plateau |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地球环境研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287499 |
| 推荐引用方式 GB/T 7714 | 闫龑. 东亚风尘沉积中石英氧同位素组成特征及其对物源变化的指示[D]. 中国科学院大学,2015. |
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