Knowledge Resource Center for Ecological Environment in Arid Area
| 黑河下游灌丛沙丘中的气候记录及若干环境事件的捕获 | |
| 其他题名 | Environmental Events and Climatic and Environmental Records in the Sediments of Tamarix Ramosissima Dunes of Heihe River Downstream |
| 马健 | |
| 出版年 | 2016 |
| 学位类型 | 硕士 |
| 导师 | 何元庆 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 黑河下游属于温带内陆极干旱气候控制下的荒漠地带，但因源于祁连山黑河水的孕育，形成了额济纳绿洲。随着气候变化和人类活动的加剧，该区域的生态环境问题日趋严重，有必要重建该区域近几百年的气候环境演变，为现在或将来面临的生态环境治理提供参考。但由于荒漠区高分辨率气候代用指标很少，所以本文选取黑河下游的灌丛沙丘沉积作为研究介质。野外考察过程中采集了两个沙丘沉积剖面，依据AMS14C定年结果建立了两个剖面的年代序列，并针对沉积物样品进行了粒度、碳酸盐、重金属汞和常量元素等实验。通过对各个指标结果的对比分析，得出以下结论：（1）通过额济纳地区两个剖面粒度特征的对比，大致总结出了研究区近300年间的气候波动：19世纪末期以后，剖面的粗颗粒含量明显下降，冬季风势力减弱，反映了气候从小冰期向现代暖期的过渡；20世纪，粗颗粒含量出现两到三次明显波动，较好地对应了1910～1920年代和1950～1960年代两次偏凉时期；剖面顶部粗颗粒含量最少，可能指示了最近几十年风力减弱的事实。说明沙丘沉积物对气候变化的响应是及时而准确的。此外，对比300年来的沙尘事件记录，发现沉积物颗粒的粗细与沙尘暴频次和强弱变化具有一定的相似性，其原因与二者成因的一致性是分不开的。（2）沙丘中Hg的突变可能与火山喷发事件有关，剖面中有两个样品Hg含量异常升高，其原因可能是1815年和1883年印尼的两次大规模火山喷发而引起的全球Hg沉降增加。此外，沙丘沉积物中的重金属汞记录了近代以来人类的工业活动，其中存在三个明显的峰值：18世纪末的西班牙美洲地区银矿开采；19世纪中后期的北美淘金热；二次世界大战及战后经济复苏。所以，欧美的工业发展历程在亚洲内陆的风沙沉积物中反应出来，这一方面说明了早在大航海时代，人类的工业活动已经对全球大气环境产生了影响；另一方面也证明了采用沙丘沉积物重建过去气候和环境演变的可靠性。（3）通过对碳酸钙、粒度和常量元素的对比分析，恢复了近300年来黑河下游地区的气候变化序列：1825年之前，气候干冷，处于小冰期末期；1825~1900年，气候相对偏湿润，小冰期结束，向现代暖期过度；1900~1930年，气候转向干冷，旱灾频发；1930~1955年，气候向相对暖湿阶段转变，该时期西北地区的增温幅度最为明显；1955~1957年，区域气温降低，气候转干；1975年至今，气候开始从暖干向暖湿转型。（4）通过祁连山区和黑河下游气候环境记录的对比，发现二者具有一定相似性，但祁连山区水分条件对温度的变化更为敏感。下游的居延海在近几个世纪中一直处于萎缩的状态，古居延泽和西居延海先后干涸，如今注入东居延海的水量也十分有限。其原因是气候水文条件的变化和人类活动强度的增大，其中人类农业生产需水量的不断增加是居延海退缩的最主要原因。 |
| 英文摘要 | Heihe downstream, which has a continental climate, is extraordinary dry. But with the influence of Heihe River, this area developed the Ejina Oasis. Because of the climate changing and the increasing human activity, the problem of ecology and environment is becoming more serious in Heihe downstream. Then, it’s necessary to rebuild the climate change during the past several hundred years, and it may offer help to the problem of ecology and environment which we are confronting with or will confront with. But the desert is short of high resolution proxy, we select the deposit nebkha as the medium. We dug two nebkha profiles during the field trip, and dated these two profiles by AMS14C. Besides, we tested the particle size, carbonate, Hg and macro-elements by using the sediment of nebkhas. And contrasted these indexes, we drew the following conclusions: (1) By contrasting the two profiles’ particle size, we concluded the changing of climate in Ejina: After the end of nineteenth Century, coarse particle content in dunes descended and the power of winter monsoon intensity have weakened, and this correspond with the end of Little Ice Age. In twenty century, the coarse particle content has several fluctuations, and correspond with two cold phases: 1910s~1920s and 1950s~1960s. The top layer of dunes have the least of coarse particle content, and this may correspond with the abatement of wind in several decades. The response to climate change of dune deposits is accurate and timely. Furthermore, contrast to the dust weather events in the past 300 years, we found that the change of particle size is similar with the change of intensity and frequency of dust weather. And this kind of similarity connect with the same cause of dune deposit and dust weather.(2) The saltation of Hg content in Ejina profile related to volcanic eruption. Hg concentration are abnormal high in two samples, and it’s connected with the increase of mercury deposition flux which caused by the volcanic eruption in 1815 and 1883. Then, mercury in nebkha sediments comes mainly from humanity's industrial actions. The range of Hg concentration of the profile has three peaks which respectively correspond with the silver mining Spanish America in late 18th century, the Gold Rush in mid-to-late 19th century, World War II and the post-war economic resurrection. Therefore, industrial developing process in western world was recorded by sand sediments in inner Asian. It means that even as early as uncharted waters, human industrial activities have impacted the global atmospheric environmental. On the other hand, it also prove the reliability of rebuild the climate change by nebkha sediments.(3) The comparison among experimental results of particle size, carbonate and macro-elements reflect on the climate change of Heihe downstream. Before 1825, climate was cold and dry, and this stage is in the end of Little Ice Age. 1825~1900, the climate was humid relatively, and the Little Ice Age terminated, then transitioned to the modern warm period. 1900~1930, climate became cold and dry, and the occurrence of droughts was more frequent. 1930~1955, climate became relative humid, and the raising temperature in Northwest is most obvious. 1955~1957, temperatures reduced, and climate turned to dry. After 1975, climatic shift has begun, climate in Northwest shift from warm-dry to warm-wet.(4) Contrast the climatic record in Qilian Mountain with the sand sediments in Heihe downstream, we found that change of these two climatic records are similar, but the moisture regime of Qilian Mountain is more sensitive to temperature. Juyan Lake, the terminal lake of Heihe River, was shrink continually during the past several centuries. The ancient Juyan Lake and Western Juyan Lake were disappear successively, and the water of Eastern Juyan Lake cannot be optimistic either. The reasons of lake-shrinking are climate change and the increase of intensity of human activities, and the latter is main cause of the shrinking of Juyan Lake. |
| 中文关键词 | 灌丛沙丘 ; 黑河下游 ; 沉积 ; 气候环境演变 ; 气候代用指标 |
| 英文关键词 | nebkha Heihe downstream deposit climate change proxy |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287707 |
| 推荐引用方式 GB/T 7714 | 马健. 黑河下游灌丛沙丘中的气候记录及若干环境事件的捕获[D]. 中国科学院大学,2016. |
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