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学科主题: 地理学::自然地理学
题名: 青藏高原纳木错地区环境化学特征
作者: 李潮流
答辩日期: 2007-05-26
导师: 康世昌
授予单位: 中国科学院研究生院
授予地点: 北京
学位: 博士
关键词: 青藏高原 ;  纳木错地区 ;  土壤元素 ;  降水化学 ;  气溶胶化学
索取号: B000004
部门归属: 图书馆
摘要: 纳木错位于青藏高原南部,是西藏最大的湖泊。纳木错流域涵盖了冰川、冻土、湖泊、高寒草甸等多种环境介质,是研究地球系统各圈层相互作用的理想地点。2005年6月中国科学院青藏高原研究所在纳木错湖东南岸建立了纳木错圈层相互作用综合观测站(简称纳木错站,30°47' N, 90°58' E; 4730 m a.s.l),拉开了对纳木错流域环境综合观测研究的序幕。本论文是纳木错站观测研究的一部分,通过对纳木错流域土壤环境和大气环境样品的采集和分析,认识纳木错流域的基本土壤和大气环境特征,为以后相关领域的工作奠定了基础。 2005年9月环绕纳木错湖岸采集了28个土壤样品,对样品的基本理化性质、重金属和稀土元素进行了分析;2005年8月至2006年8月收集了纳木错站的48次大气降水样品,并于2006年5月在念青唐古拉山扎当冰川垭口采集了雪坑冰雪样品,分析测定了全部样品的主要阴阳离子(Cl-, SO42-, NO3-, Ca2+, NH4+, Na+, K+, Mg2+)和 δ18O值,以及部分样品的pH值和电导率;2005年11月至2006年10月在纳木错站采集了49个大气气溶胶样品,2006年6月至10月在扎当冰川垭口采集了7个大气气溶胶样品,分析了上述样品中的元素含量,结果表明: 由于纳木错地区低温少雨的气候特点,该地区的土壤仍处在物理风化的早期阶段,大部分土壤呈碱性。纳木错地区土壤营养状况差,总有机碳和可交换阳离子含量很低。该地区土壤的pH值主要受土壤中无机碳的影响。纳木错地区土壤中重金属元素和稀土元素含量及特征受到土壤母质和土壤理化性质的共同影响。大部分元素的含量在南岸受土壤有机碳含量的控制,在北岸受土壤无机碳含量的控制;元素As的含量与土壤的pH值密切相关。土壤稀土元素的球粒陨石标准化结果显示,纳木错土壤稀土元素具有轻稀土元素富集和Eu(铕)负异常的一般特点,稀土元素和大部分重金属元素(除元素As外)主要富集在土壤表层。纳木错的土壤元素B,As和Bi具有较高的富集因子值。纳木错地区的降水化学主要受局地环境因素的影响,其中阴阳离子含量的顺序分别为HCO3->Cl->SO42->NO3-和Ca2+> NH4+ >Na+>K+>Mg2+,HCO3-和Ca2+分别为占主导地位的阴、阳离子,它们的浓度主要受降水持续状况和降水量的影响。降水pH值偏中性,电导率较低,pH值和电导率的加权平均值分别为6.24和19.3μs/cm。纳木错地区降水中的离子主要受局地产生的粉尘和当地牧民放牧燃烧等活动的影响,其次高原上的盐湖蒸发和干涸盐湖中的矿物颗粒的贡献,相应地海盐离子由于长距离传输中的“遗失”而对降水离子贡献较小。离子的季节变化特点是:总体上非季风期降水中的所有离子含量(Cl-除外)比季风期高。一些海盐离子在季风降水中的含量一定程度上反映了水汽来源。由于NH4+与δ18O全年的变化趋势比较一致,NH4+的含量有可能作为判别水汽来源的指标。通过纳木错与扎当冰川雪坑离子含量的对比发现,高原的降水化学特征与该地区的下垫面状况和海拔高度有很大关系,较低海拔降水化学主要反映了局地的大气特征。纳木错地区大气气溶胶的元素含量较低。元素经验正交分析表明,地壳粉尘对纳木错气溶胶有很大贡献,其次是有着复杂来源的人类活动释放的污染物。纳木错气溶胶元素中的As,Cr,Cd,Bi,Ni,B,Zn,Cs,Pb等元素具有较高的富集因子值,表明它们受到人类向大气中排放污染物的影响。在季节变化上,夏、秋两季的富集因子值较高,说明此时盛行的南亚季风把印度次大陆的污染物传输至纳木错地区。冬、春两季具有较低但稳定的富集因子值,可能反映的是这一时期盛行的西风环流从中东及印度西北部等地传输来的污染物。其中元素As和B中的一部分可能受到局地和高原面产生气溶胶的影响。纳木错大气气溶胶中的稀土元素主要来自粉尘。气溶胶与黄土相似的稀土元素组成说明,纳木错地区的气溶胶反映的是大尺度的大气环境。夏季风期间降水量的增大及降水pH值的降低对气溶胶中稀土元素的组成特点有很大影响。垭口气溶胶中大部分典型地壳元素的含量仅为同时期纳木错站的一半左右,冰川区一些典型污染元素如元素Cd,As,Bi 的含量也比纳木错站低。
英文摘要: Nam Co, the largest lake of the Tibetan Autonomous Region, lies at the south part of the Tibetan Plateau. Nam Co region is a perfect laboratory on the study of interaction among Multispheres, which composes of many environmental mediums such as glacier, frozen ground, lake and meadow. Nam Co Monitoring and Research Station for Multisphere Interactions (Briefly Nam Co Station, 30°47' N, 90°58' E; 4730 m a.s.l) was established on southeast bank of Nam Co by Institute of Tibetan Plateau, CAS on June 2005, which marked the prelude of the systematic scientific research in Nam Co region. This thesis is one part of the systematic research of Nam Co station, which will illustrate the basic Environmental characteristics of soil and atmosphere in this region by means of collection and analysis samples of soil, precipitation and aerosol. Then set a solid foundation for the future relative researches. Twenty-eight soil samples were sampled along Nam Co bank at September, 2005 and analyzed for basic physio-chemical characteristics, heavy metals and rare earth elements (REEs); A total of 48 precipitation samples and 30 snow-pit samples were collected at Nam Co Station from August 2005 to August 2006 and the col of Zhadang glacier at May 2006, respectively. All samples were analyzed for major cations (NH4+, Na+, K+, Ca2+ and Mg2+) and anions (Cl−, NO3− and SO42−), some samples were analyzed by conductivity and pH; Forty nine aerosol samples were collected at the Nam Co Station from November 2005 to October 2006. Seven aerosol samples were also sampled at the col of Zhadang glacier 50 km away from Nam Co station during June and October 2006. The results indicate: The soil in the Nam Co region is still at an early alkaline weathering stage (pH=7.94) for both low annual precipitation and low average annual temperature. The nutrient condition of this region is bad, both TOC and CEC value is generally low. IC concentration contributes much to pH value of this region. Mean concentrations of heavy metals and REEs of this region are controlled by both parent materials and physico-chemical characteristic. Most elements concentrations controlled by TOC in south bank and by IC in north bank. While As has close connection with pH value of the soil. The chondrite-normalized Diagrams of REEs suggest general characteristics of high LREE-enrichment, HREE-depletion and Eu-depletion. Vertical profiles indicate that both heavy metals (except As) and REEs primarily exist in the surface soil. Elements B, As and Bi have high enrichment factors. The precipitation chemistry in the Nam Co region is mainly influenced by the regional environment dominated by crustal dust aerosols. In general, the ionic abundance of precipitation (μeq/L) samples follows the sequence of Ca2+> NH4+ >Na+>K+>Mg2+ for cations and HCO3->Cl->SO42->NO3- for anions, with Ca2+ and HCO3- as the dominant ions. Concentrations of Ca2+ and HCO3- are correlated negatively with precipitation amount. The average pH and conductivity value of precipitation is 6.24 and 19.3µs/cm, respectively. Empirical orthogonal function (EOF) analysis indicates that regional crustal aerosols and species from combustion emissions of residents are the major sources for these ions, lake salt aerosols from the Nam Co nearby and regional mineral aerosols from dry lake sediments is secondary sources, sea salt contribution is the least due to the long distance transport. In general, all the ion concentrations (except of Cl-) in non monsoon period are higher than monsoon period. Some sea salt ion concentrations reflect the water source at some extent during monsoon period. It seems that NH4+ concentration can be utilized as an index of distinguishing water resource due to its consistent variation trends with that of δ18O. When compared with data from a snowpit in the Zhadang Glacier 50 km away (5800 m a.s.l), major ion concentrations in precipitation at the Nam Co Station are much higher due to local aerosol inputs. Comparisons of aerosol element concentrations at Nam Co station with other regions suggest that the Nam Co region is a remote and “pristine” region of the world. EOF analysis suggests that natural dust contribute much to the total aerosol, then is anthropogenic pollutants of complex source. Crustal enrichment factors (EFs) reveal several elements (As,Cr,Cd,Bi,Ni,B,Zn,Cs,Pb) may have anthropogenic source. Nam Co region received more contaminants in summer and autumn season than winter and spring season, which shows that Indian monsoon in summer and autumn season transport more contaminants from Indian subcontinent to Nam Co region. The high EF values of some elements in winter and spring season maybe reveal Nam Co region is affected by the anthropogenic contaminants from north-west part of India and Middle East. Among them part of As and B maybe came form some local dusts of the Tibetan Plateau. The aerosol REEs reside mostly in crustal dust. The similar REE compositions between aerosol and loess suggest aerosols of the Nam Co station reflect large scale atmospheric condition. The relatively higher precipitation and lower pH value of the monsoon season affect much of the aerosol REE compositions. Most crustal element Concentrations in glacial region is about half of the Nam Co station. Some polluting elements such as Cd,As,Bi at the glacier region also lower than the Nam Co station.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.itpcas.ac.cn/handle/131C11/1222
Appears in Collections:图书馆_学位论文

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Recommended Citation:
李潮流.青藏高原纳木错地区环境化学特征[博士].北京.中国科学院研究生院.2007
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