中国科学院青藏高原研究所机构知识库
Advanced  
ITPCAS OpenIR  > 图书馆  > 学位论文
Subject: 地理学::自然地理学
Title: 青藏高原典型区雪冰重金属记录及其环境意义
Author: 张强弓
Issued Date: 2009-06-05
Supervisor: 康世昌
Major: 自然地理学
Degree Grantor: 中国科学院研究生院
Place of Degree Grantor: 北京
Degree Level: 博士
Keyword: 青藏高原 ;  雪冰/冰芯 ;  重金属 ;  汞(Hg) ;  时空分布 ;  历史记录
Call Number: S000022
Department: 图书馆
Abstract: 工业革命以来,人类活动在加速改变社会发展历史进程的同时,也给环境造成了巨大破坏,并逐渐成为影响环境中化学元素再分配的重要因素。重金属一般以很低的天然含量广泛存在于自然界中,但人为排放的增多已经造成了全球范围的重金属污染。重金属在极地和山地冰川中的含量变化可以作为评价人类活动对大气环境影响的良好指标。青藏高原平均海拔4000 m以上,自身人类活动稀少且远离工业源区,是评价大气重金属污染程度和历史变化的理想研究场所。本论文重点调查了青藏高原南部珠峰地区及其他典型冰川区雪冰中的重金属浓度,并结合稳定氢氧同位素、主要阴阳离子和不溶微粒等参数的分析,揭示了青藏高原这一独特区域雪冰重金属的时空变化特征和历史变化趋势及其环境意义。 沿珠穆朗玛峰(珠峰)北坡的攀登路线在不同海拔采集了14个表层雪样品,在东绒布冰川垭口钻取了一支108.83 m冰芯,分析了样品中的主要元素及重金属浓度。在空间上,表层雪重金属浓度未出现显著的随海拔高度变化的特征,主要归因于极高海拔区强风对雪的搬运以及局地裸露基岩的粉尘输入;峰顶重金属浓度较高,可能与登山活动有关。冰芯中重金属浓度呈现出明显的季节变化特征,即季风期低而非季风期高。与世界其他地区雪冰样品相比,珠峰雪冰中重金属浓度大致与南北极及偏远地区相当,远低于人类活动强烈的大城市,说明珠峰地区受到人类活动并不强烈,可以作为全球偏远地区以及对流层中上部大气环境本底的代表。 对雪冰中稀土元素的报道还不多见,珠峰冰芯上部8.4 m记录表明,稀土元素浓度具有季风期低而非季风期高的特征,其标准分布模式在两个季节表现出相似的特征。对稀土元素的潜在源区评价表明,人为源可基本忽略,局地自然源贡献也非常小;结合稀土元素地球化学特性和大气环流分析等推断,珠峰地区雪冰中的稀土元素浓度很可能代表了对流层中上部大气的平均状况,源区主要包括上风方向的干旱区,如撒哈拉、Thar沙漠、西亚和青藏高原西部等。 利用珠峰冰芯恢复了过去350年来大气重金属含量的历史记录。结果表明,大部分重金属浓度的历史变化趋势有较好的一致性,且与主要元素Al和Fe的变化趋势相似,表现为缓慢上升。其中大部分重金属浓度在1720s、1750s、1770s、1870 - 1940和1960 - 1990期间表现为高值期。大多数重金属浓度并未在工业革命后期,尤其是20世纪中期出现显著的增长。过去350年来,重金属10年平均浓度值表现为较为稳定的状态,未出现数量级的变化。富集因子(EF)计算表明,除了Cs、Bi和U外,其他重金属的EF值在过去350年比较稳定,大部分元素的10年平均值均低于10,表明珠峰冰芯记录的重金属主要还是自然来源。U的EF平均值在近50年较以前有了明显升高,这可能是人类污染贡献比例增高的体现。 汞是一种全球性污染物,可以长距离传输并易在低温区沉降。对青藏高原及其毗邻的天山地区6条冰川共计8个雪坑的总汞浓度分析表明,大部分雪坑各层位的总汞浓度均在15 ng/L以下,与世界其他偏远地区雪冰中总汞浓度相当,显著低于城市如北京降雪中的总汞浓度,表明青藏高原代表了偏远地区雪冰的总汞浓度状况。总汞浓度表现出季节变化,即季风期较低而非季风期较高;在空间变化上呈现“北高南低”的分布态势。总汞和不溶微粒浓度具有较好的对应关系,说明青藏高原大气汞传输和沉降很可能是以颗粒态汞为主要方式进行的。对大气汞沉降通量估算表明,青藏高原大气汞沉降通量在0.88-8.03 μg/ m2.yr间,与世界范围内大气汞自然沉降速率相当,而显著低于城市如北京的大气汞年沉降速率。 今后的工作应对青藏高原雪冰重金属的时空分布特征和历史记录做综合集成研究。此外,汞的生物地球化学循环是当前环境中重金属污染研究领域的热点,需要给予特别关注。
English Abstract: The Industrial Revolution was the beginning of a major change in the course of human history. Since then, human society and development commenced exponentially and lucratively, however such growth comes at a cost and the environment was sacrificed for the evolution of our way of life. We are approaching a time where the environmental degradation has reached crisis levels. It is evident that human activities have been playing a significant role on the redistribution of the earth’s elements. Heavy metals typically have low natural abundance, however, increasing anthropogenic emissions have caused serious heavy metal pollution concerns globally. Heavy metals recorded in the Glaciers from Polar and high-mountain regions can serve as an excellent proxy of evaluating human impact on the atmospheric environment. The Tibetan Plateau, known as the highest plateau in the world, with an average elevation of over 4000 m, and sparse human population as well as negligible industrial activities, has been recognized as an ideal “Natural Laboratory” for understanding the scope and history of atmospheric heavy metal pollution. This dissertation quantifies heavy metal concentrations in the snow/ice samples from Mt. Everest regions and other typical glaciers on the north-south transect of the Tibetan Plateau along with other proxy such as stable oxygen/hydrogen isotopes, major ions and insoluble microparticles, to assist with the explanation of the seasonal and spatial variations of heavy metals, historical trends and their environmental significance. In May 2005, a total of 14 surface snow (0 - 10 cm) samples were collected along the climbing route from the advanced base camp to the summit (6500 - 8844 m a.s.l.) on the northern slope of Mt. Everest. A 108.83 m ice core was retrieved from the col of the East Rongbuk Glacier on the eastern saddle of Mt. Everest in September 2002. Samples were measured for major elements and heavy metals. Results showed that there are no clear trends for element variations with elevation due to redistribution of surface snow by strong winds during the spring. In addition, local crustal aerosol inputs also have an influence on elemental composition of surface snow. Heavy metal concentrations in the snow samples from the Everest summit were relatively high, resulting from the impact of climber activities. Seasonal variability in snow/firn heavy metals showed higher concentrations during the non-monsoon season while lower concentrations we observed during the monsoon season. Heavy metal concentrations at Mt. Everest are comparable with polar sites and other remote sites, plus are far lower in concentrations than large cities, indicating that anthropogenic activities and heavy metal pollution have little effect on the Mt. Everest atmospheric environment, thus it is representative of the background atmospheric environment. Rare earth elements (REEs) measurements have not been extensively attempted in glacial snow/ice samples due to their extremely low concentrations and limited available sample volumes in most ice cores. REEs in Everest ice core samples display large seasonal variations, with high concentrations in the non-monsoon season and low concentrations in the monsoon season. This seasonality is useful for ice core dating. When normalized to a shale standard, the Mt. Everest REEs exhibit a consistent shale-like pattern with a slight enrichment of middle REEs during both seasons. Investigation of potential REEs sources suggests an absence of anthropogenic contributions and minimal input from local natural provenances. REEs in Everest ice core samples are most likely representative of a stable well-mixed REE background of the middle and upper troposphere consisting of a mixture of aerosols transported by the atmospheric circulation from the west windward arid regions such as the Thar Desert, West Asia, the Sahara Desert, western Tibetan Plateau and other uncertain regions. High resolution atmospheric heavy metal records for the past 350 years were reconstructed using the 108.83 m Everest ice core. Most metals present similar historical variation trends which mirror Al and Fe, which exhibit slight increasing trends. Higher concentrations occur in 1720s, 1750s, 1770s, 1870 - 1940 and 1960 - 1990. On the basis of 10-yr mean heavy metal concentrations, most heavy metals did not exhibit elevated concentrations since the time of the industrial revolution or the mid 20th century. During the past 350 years, most heavy metals stay at a steady concentration, and did not show a notable increase larger than an order of magnitude. Enrichment factor (EF) analysis showed that heavy metal concentrations are stable and lower than 10 in the past 350 years except for Cs, Bi and U, indicating that natural sources remain dominant for Everest samples. It has to be noted that, U has elevated concentrations during 1970 – 1990, furthmore, the EF mean values were increasing significantly relative to previous years, possibly due to the increasing contribution from the anthropogenic emissions. Mercury (Hg), has been found to undergo long-range transport on a global scale and is easily deposited in cooler regions, which has given it global pollutant status. Samples for mercury were collected in 8 snow pits from 6 glaciers along the north- south transect of the Tibetan Plateau. Results showed that most samples have total mercury concentrations lower that 15 ng/L, which is comparable with other remote regions, and are lower than fresh snow in Beijing. Total mercury concentrations also showed clear seasonal variation and are spatially characterized by higher concentrations in north while lower in south. The strong positive correlation between total mercury concentrations and the insoluble microparticle concentrations may indicate that atmospheric transport and deposition of mercury in the Tibetan Plateau are dominated via particulate binding. The annual atmospheric mercury flux was estimated to range of 0.88 - 8.03 μg/ m2.yr in the Tibetan Plateau, which remains within the average level of global natural flux, and are much lower than Beijing. A synthesis study on spatial and temporal variations, as well as historical records of heavy metals in snow/ice from Tibetan plateau is strongly recommended. Furthermore, biogeochemical cycling of mercury, a hot spot in study of heavy metals, is worthy of being paid special attentions.
Language: 中文
Content Type: 学位论文
URI: http://ir.itpcas.ac.cn/handle/131C11/1238
Appears in Collections:图书馆_学位论文

Files in This Item:

There are no files associated with this item.


Recommended Citation:
张强弓.青藏高原典型区雪冰重金属记录及其环境意义[博士].北京.中国科学院研究生院.2009
Service
Recommend this item
Sava as my favorate item
Show this item's statistics
Export Endnote File
Google Scholar
Similar articles in Google Scholar
[张强弓]'s Articles
CSDL cross search
Similar articles in CSDL Cross Search
[张强弓]‘s Articles
Related Copyright Policies
Null
Social Bookmarking
Add to CiteULike Add to Connotea Add to Del.icio.us Add to Digg Add to Reddit
所有评论 (0)
暂无评论
 
评注功能仅针对注册用户开放,请您登录
您对该条目有什么异议,请填写以下表单,管理员会尽快联系您。
内 容:
Email:  *
单位:
验证码:   刷新
您在IR的使用过程中有什么好的想法或者建议可以反馈给我们。
标 题:
 *
内 容:
Email:  *
验证码:   刷新

Items in IR are protected by copyright, with all rights reserved, unless otherwise indicated.

 

 

Valid XHTML 1.0!
Copyright © 2007-2017  中国科学院青藏高原研究所 - Feedback
Powered by CSpace