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1.
沉积物金属元素变化的粒度效应—以太湖沉积岩芯为例 总被引：9，自引：3，他引：9
水体沉积物中金属元素含量变化除了与人为污染有关之外,在很大程度上受沉积物粒度、矿物组成等沉积物性质的影响．在进行沉积物金属元素研究中,要充分考虑沉积物金属元素含量变化的粒度效应．本文通过对太湖MS岩芯中17种金属元素、沉积物粒度、矿物组成等指标的分析,研究了金属元素变化特征以及与沉积物粒度组成的关系．MS岩芯金属元素变化可分为两类,第一类主要为Al、Fe、K等,该类元素在沉积岩芯中下部含量较高,岩芯上部含量较低;第二类为Na元素,在沉积岩芯中下部含量较低,岩芯上部含量升高．MS岩芯中金属元素与粘土含量之间具有显著相关关系,经沉积物粒度(粘土含量)校正后,沉积岩芯中金属元素含量趋于稳定．因此,沉积物粒度组成(粘土含量)是影响金属元素含量的主要因素,在研究太湖沉积物金属元素变化规律及进行金属污染评价时,应对金属元素含量进行粒度校正． 相似文献
2.
青海湖沉积碳酸盐矿物之间氧同位素分馏的评估及其环境意义 总被引：1，自引：0，他引：1
青海湖沉积岩芯的矿物学和稳定同位素研究结果显示自生碳酸盐矿物以单种或多种矿物形式保存在沉积物中;不同碳酸盐样品的δ18O值的变化范围为5.47‰至-1.04‰,差值最高达6.5‰;δ18O值与总碳酸盐含量呈正相关关系,与碳酸盐矿物种类的改变则无明显关联.结果表明,造成δ18O显著变化的主导因素是湖水氧同位素组成,自然条件下生成的不同碳酸盐之间的氧同位素分馏不明显.说明δ18O是指示闭流湖泊降水蒸发水量平衡变化的敏感指标之一. 相似文献
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4.
西藏普莫雍错不同岩芯环境指标的对比研究及其反映的近200年来环境变化 总被引：4，自引：1，他引：3
在西藏南部普莫雍错不同位置处采集了四支岩芯沉积物,对其中一支利用~(210)pb和~(137)Cs方法建立了沉积物的年代序列,并对其他三支岩芯的上部沉积物进行了总有机碳、无机碳、粒度及化学元素含量的分析.结合沉积物年代,对不同岩芯的环境代用指标进行对比,讨论了该地区近200年来的环境变化状况.结果表明,不同位置处采集的岩芯其环境指标变化趋势在整体上具有一定的可比性,但在细节变化与环境指标的数值上仍具有明显的差异,显示了湖泊内部沉积状况的空间差异性,这可能是由于采样点水深、水下地形以及与主要补给河流距离的不同而造成的.PY04岩芯环境指标显示普莫雍错湖区环境在约1900AD之前较为稳定;在约1900-1940AD之间湖区环境波动加剧,地表侵蚀增强,沉积速率加快;湖区环境在1940AD左右发生了明显的变化,温度显著升高,沉积物粒度增大,湖泊处于退缩状态,表明湖泊环境向暖干化方向发展. 相似文献
5.
新疆博斯腾湖沉积物粒度的古环境意义初探 总被引：3，自引：0，他引：3
湖泊沉积物的粒度分析是一种研究古环境变化常用的手段,但是其环境意义具有多解性,尤其是沙（荒）漠干旱区的湖泊沉积物粒度变化,代表的是沙尘天气的多寡强弱还是其它环境因素的变化值得细致研究。在对我国最大的内陆淡水湖—新疆博斯腾湖的沉积物短岩芯进行了^210Pbex,^137Cs定年的基础上,对近50多年沉积物的粒度进行分析,结果表明平均粒径与粗颗粒含量与区域最大河流—开都河大山口站的最大一天洪量、洪峰流量、天山巴音布鲁克站年降水量、湖泊水位变化以及湖泊附近焉耆站3-6月风力强度变化记录等环境因素对比发现,湖泊中部沉积物中粗颗粒含量变化主要反映的是入湖河流径流量、区域洪水强度及频率、山地降水,而并不反映大风天气或者湖泊水位的变化。对其近千年沉积岩芯的多指标分析结果表明,即使在数百年时间尺度上,博斯腾湖沉积物粒度的环境意义依然与十年时间尺度上一致。 相似文献
6.
XRF岩芯扫描技术是古气候研究中的重要工具,其中所获得的基于湖泊岩芯的Rb/Sr比值在古气候研究中被广泛用于表征流域化学风化的强度.然而在不同的地质背景下,影响Rb/Sr比值变化的因素不同,使得其古气候解释意义较为复杂.本研究选取青藏高原东部若尔盖盆地的湖泊沉积物岩芯,获取了高分辨率的XRF岩芯扫描Rb/Sr比值、传统XRF测试Rb/Sr比值、化学蚀变指数CIA以及其他古气候替代指标,开展了不同指标间的对比分析.研究结果显示:(1)在细粒物质为主的沉积段,岩芯扫描Rb/Sr和CIA可作为指示化学风化强度的可靠指标;(2)岩芯扫描Rb/Sr和CIA的低值对应于总有机碳含量、乔木花粉含量、碳酸盐含量和C/N比值的高值,综合分析各古气候代用指标的指示意义,认为岩芯扫描Rb/Sr可指示亚洲夏季风强度的变化;(3)受"粒度效应"和测试精度限制,若尔盖岩芯25~0.3和56~47m沉积段的扫描Rb/Sr数据不适用于化学风化强度的重建,在今后若尔盖盆地古气候演化历史的重建工作中应加以注意.本研究指出,当涉及XRF岩芯扫描Rb/Sr在其他研究区古气候分析中的应用时,应通过多指标间的相互验证来明确其特有的古气候指示意义. 相似文献
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云南程海沉积物碳酸盐来源辨识 总被引：8，自引：2，他引：6
碳酸盐是湖泊沉积物的组成部分,其碳、氧同位素组成是恢复湖区古气候/古环境的有效代用指标.沉积物碳酸盐包括物源区带来的外源碳酸盐和湖泊内生沉淀产生的自生碳酸盐,其中只有自生碳酸盐才具有古气候指示意义.故沉积物碳酸盐来源辨识是开展碳酸盐古环境记录研究的基础和前提.通过多种方法的综合判别,证明了程海沉积物碳酸盐主要是自生碳酸盐,为开展碳酸盐记录研究提供了可靠依据.程海是开展碳酸盐碳氧同位素与古气候研究的理想场所,尤其值得深入研究. 相似文献
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我国西南地区湖泊众多,利用湖泊沉积物已开展了大量全新世植被、降水、温度和水位等的重建工作.然而,代用指标的季节性差异和气候演变的区域差异使得不同代用指标和地区重建的古气候结果存在较大差异,需要更多可靠记录来相互佐证和构建我国西南地区气候变化的详细图景.本文以云南抚仙湖FXH-6钻孔沉积物为研究对象,对正构烷烃和色度指标作了分析,在厘清其来源及环境指示意义的基础上,重建过去近5000年抚仙湖有机质的来源和湖泊水位的变化,探讨了湖泊环境变化与区域气候变化的关系.结果表明,抚仙湖沉积物中正构烷烃n-C23和n-C31可有效指示内源沉水植物和外源陆生植物.近5000年抚仙湖湖泊环境经历了3个阶段:在5000—2300 cal a BP阶段,沉水植物广泛分布,湖泊水位处于高位;在2300—2000 cal a BP阶段,抚仙湖沉积环境快速变化,内源沉水植物生物量锐减,水位快速下降;2000 cal a BP至今,沉水植物生物量持续减少,湖泊水位保持低水位;同时,人类活动也影响了该阶段(2000 cal a BP至今)陆源植物的输入.本研究重建的抚仙湖持续降低的水位变化和湖泊生产力趋势与过去5000年西南地区的年平均温逐渐降低、年平均降水量逐渐减小的总体趋势相对应,表明区域气候变化是湖泊沉积环境变化的主要驱动力. 相似文献
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通过对现代乌伦古湖附近出露的古湖相沉积剖面的AMS~(14)C测年,粒度、总有机碳、总有机氮以及碳酸盐等环境代用指标的分析及其与全新世钻孔沉积记录的对比研究,结果发现:乌伦古湖在MIS-3晚期的33600-22500 cal a BP以及冰后期至早中全新世的16500-6500 cal a BP期间,维持着湖相沉积环境,湖面约比现在湖面高40 m.33600-22500 cal a BP的MIS-3晚期,气候相对温暖,乌伦古湖呈现高湖面特征,湖泊沉积物来源以流水搬运为主;22500-16500 cal a BP的末次冰期冰盛期,气候寒冷干燥,湖泊沉积物来源以风力搬运为主;16500-6500 cal a BP的冰后期以及早、中全新世期间,气候回暖,湖泊沉积物主要来源于河流径流作用.6500-5500 cal a BP,受高温干旱事件的影响,湖面收缩、水位剧降,除沉积中心外的其它钻孔位置出现沉积中断.5500 cal a BP后气候转冷变湿,湖泊重新恢复到现在的状态.乌伦古湖MIS-3晚期以来的古湖相沉积环境变化及其反映的古气候万年尺度上的干湿变化与周边区域气候环境变化记录有很好的一致性,响应了区域环境变化和全球气候突变事件.季风和西风的强度消长变化及其引起的环流条件改变以及温度变化引起的蒸发效应可能是区域气候环境变化的主要原因.这一古湖相沉积记录的研究可为MIS-3晚期以来北疆地区的古湖泊演化以及长时间尺度上西风和季风环流相互关系及其影响区的气候环境演化提供地质证据. 相似文献
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柴达木盆地东部尕海短钻岩芯记录的过去近400a区域环境变化 总被引：2，自引：2，他引：0
干旱区湖泊沉积可以有效记录区域湿度变化及粉尘活动历史,位于柴达木盆地德令哈南部的咸水封闭湖泊尕海具有恢复区域环境变化的潜力.该地区的长序列环境演变研究已开展了较多的工作,但缺乏短尺度、高分辨率的近代以来的环境变化湖泊记录.通过对尕海深水区短钻岩芯放射性核素210Pb和137Cs的年代测定和沉积物各指标分析,认为尕海沉积物碳酸盐含量可以反映区域湿度变化;而粗颗粒组分(66.9μm)主要由风力搬运入湖,其含量可以指示区域粉尘活动历史.区域近400 a的环境变化可划分为3个阶段:1633 1750 AD:各指标出现大幅度波动,表现出该时期气候环境的不稳定和干湿交替,其中1650 1720 AD的变化波动尤为显著,这与太阳活动进入Maunder极小期存在一定的联系.1750 1950 AD:区域气候环境无明显波动,碳酸盐含量逐渐降低,湿度增加.1950 2010 AD:各指标变动剧烈,区域虽降水增多,但由于蒸发加强,湿度降低;1974 AD以后粗颗粒组分含量急剧上升,表现出高强度尘暴事件. 相似文献
11.
青藏高原东南部巴松措现代沉积过程及其对气候变化的响应 总被引：1，自引：1，他引：0
湖泊沉积物是记录气候演化信息的重要载体之一，在探讨过去气候变化过程研究中发挥重要作用.然而，沉积物中的许多代用指标对气候的指示意义存在多解性，不同指标所反映的环境信息相互之间有时会存在矛盾.为了能够更准确地解读湖泊沉积物中指标所记录的环境变化信息，开展现代湖泊沉积物指标与环境之间的关系研究，深入探讨各指标对环境变化的响应机制尤为关键.本文选取青藏高原东南部巴松措湖泊表层沉积物作为研究对象，利用210Pb与137Cs比活度检测结果建立年代序列，对沉积物中粒度、磁化率、有机质含量等指标进行分析，揭示巴松措现代沉积过程.结合沉积物粒度端元组分分析结果，并将不同指标变化与林芝气象站所记录的数据资料进行对比，得出以下主要结论：该地区沉积物来源主要包括径流搬运的冰川碎屑物质和来自青藏高原南部、西南部上空悬浮于大气中的风成物质两部分；其中，通过风力搬运的物质输入主要集中在冬半年，受季节性风向及风速变化影响明显；径流受到冰雪融水与夏季降水的补给，因此通过径流搬运的物质输入量受到温度与降水综合影响；湖泊中磁性矿物碎屑的产生和输入主要受区域降水量影响的流域侵蚀速率变化控制，该湖泊沉积物磁化率波动可以有效的指示该地区降水量变化；沉积物中总有机碳含量和总氮含量变化主要反映湖泊自身初级生产力的变化，对区域温度变化的响应显著. 相似文献
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Humid Little Ice Age in arid central Asia documented by Bosten Lake, Xinjiang, China 总被引：15，自引：0，他引：15
J. A. Holmes 《中国科学D辑(英文版)》2006,49(12):1280-1290
Short sediment cores retrieved from Bosten Lake, the largest inland freshwater lake in China, were used to explore humidity and precipitation variations in arid central Asia during the past millennium. The chronology of the cores was established using 137Cs, 210Pb and AMS 14C dating re- sults. Multi-proxy high-resolution analysis, including pollen ratios of Artemisia and Chenopodiaceae (A/C), carbonate content and grain size, indicates that the climate during the past millennium can be divided into three stages: a dry climate between 1000―1500 AD, a humid climate during the Little Ice Age (LIA) (c. 1500―1900 AD), and a warm dry period after 1900 AD. On centennial timescales, the climate change in northwestern China during the past 1000 years is characterized by oscillations between warm-dry and cold-humid climate conditions. All the proxies changed significantly and indi- cate increased precipitation during the LIA, including increased pollen A/C ratios and pollen concen- trations, decreased carbonate content and increased grain size. The humid period during the LIA re- corded by the Bosten Lake sediments is representative of arid central Asia and is supported by nu- merous records from other sites. During the LIA, the water runoff into the Keriya River and Tarim River in the Tarim Basin increased, while the ice accumulation in the Guliya ice core increased. Additionally, the lake levels of the Aral and Caspian Sea also rose, while tree-ring analysis indicates that precipita- tion increased. We hypothesize that both the lower temperature within China and the negative anomalies of North Atlantic Oscillation (NAO) during this period may have contributed to the humid climate within this area during LIA. 相似文献
13.
陕西红碱淖近百年来环境变化的湖泊沉积记录 总被引：14，自引：1，他引：14
本文通过岩性、粒度、磁化率、有机碳、化学元素的多指标综合分析,对陕西红碱淖近百年以来的环境演化进行了探讨。红碱淖于1927年后开始成湖,以较低的磁化率值、低湖泊生产力和较高的Fe/Mn比值为特征;1952-1960年,为短暂湖泊快速扩张时期,在沉积物中表现为粘粒含量一度下降、各元素浓度明显被稀释;自1960年以来,岩性和指标特征反映了该湖演化为稳定的深湖环境。湖泊的形成和扩张与区域降水量的增加有关,而50年代后期以来湖面的迅速扩大同时得益于人类滩地疏导导致的入湖水量增加。人类活动也引起了近40年来湖泊生产力的提高和沉积物-水界面氧系统的变化。此外,钻孔粒度特征较好地分辨出20世纪30年代末至40年代3次强沙尘暴事件。 相似文献
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古生态记录揭示的长江中下游太白湖生态系统稳态转换过程 总被引：2，自引：2，他引：0
长江中下游浅水湖泊在过去百年内受到强烈的人类活动影响,生态系统状态发生显著的变化,服务功能逐渐丧失.为了更科学有效地管理浅水湖泊,当前迫切需要了解湖泊的生态系统转变过程.以长江中下游典型富营养化浅水湖泊太白湖为例,结合历史资料和监测数据,基于铅铯同位素重建年代序列,利用粒度、地化指标和沉积物中硅藻群落的时间序列数据,对太白湖过去百年间生态系统转变进行分析.基于T检验的STARS法检测硅藻群落的结果显示,有2个稳态转换分别发生在1950s末和1990s末.1950s末太白湖硅藻群落代表的生态系统状态发生了显著突变,这主要归因于由于建闸筑坝造成的水文条件和营养条件的改变;1990s期间的湖泊生态系统整体转变则是由长期营养输入和渔业活动加强导致的生态系统弹性损失引起的.讨论了不同阶段太白湖生态系统主要要素间反馈机制在水文条件改变和营养富集影响下的变化,加深了对人类活动干扰下太白湖生态系统结构变化过程的理解,为建立浅水湖泊系统动力学模型提供基础. 相似文献
15.
Quantitative reconstruction of the lake water paleotemperature of Daihai Lake, Inner Mongolia, China and its significance in paleoclimate 总被引：5，自引：2，他引：5
By measuring Sr/Ca ratios of the ostracod shells (Limnocthere cf. inopinata) in sediments of the Daihai Lake, and combined with Sr2+/Ca2+ ratios of the lake water, this paper obtained paleosalinity of the lake water. Vaporizing experiment of the lake water in
laboratory showed that there was a quantitative relationship between salinity and oxygen isotope. Using this relationship,
oxygen isotope values of the paleo-lake water were calculated. By measuring the oxygen isotope of the authigenic carbonate
in the lake’s sediments, and in combination with the oxygen isotope values of the paleo-lake water, the paleotemperature of
the lake water was calculated. Finally, based on these proxies, the paleoclimate in the lake basin was explored. 相似文献
16.
《Limnologica》2020
Lake sediment can sequestrate large amounts of carbon and this issue has become a research hotspot. However, most of research on carbon burial in lakes is based on a single (or a few) sediment core records and so may underestimate the variability of carbon burial features within a single lake. In this study, therefore, Chaohu Lake, a typical large shallow lake in the middle and lower reaches of the Yangtze River, was selected to conduct multiple, high resolution sediment core studies to elucidate that variability. Overall 18 sediment cores are analyzed according to paleolimnological proxies (including 210Pb/137Cs for 3 master cores); sediment accumulation rate, total organic carbon, grain size and loss of ignition is measured or estimated for most cores. The spatiotemporal variations of organic carbon burial rate (OCBR), carbon storage and their driving factors were examined. Results show: 1) There was a clear temporal difference in carbon burial during the past 150 years, with OCBR varying from 1.1 g C/m2/y to 25.6 g C/m2/y (mean 9.8 g C/m2/y). OCBR began to increase after around 1900, a rapid increase followed after 1950s and a downward trend after 1970s. Total carbon burial amount (OCBA) in the lake since the 1850s is 1.11 x 1010 g. 2) The average OCBR of six sediment cores in the northwest lake area is 13.4 g C/m2/y, significantly higher than that for sediment cores in other areas (9.6 g C/m2/y). 3) TOC, OCBR, OCBA in all 18 cores exhibited similar temporal patterns (i.e. marked increase since 1950s in most of the cores) but with significant differences in several lake locations. 4) During the last 150 years, carbon burial in Chaohu Lake appears to be greatly affected by changes in regional temperature and population size, according to their significant correlations. OCBR also has a significant correlation with the average lake level in the past 50 years, indicating human activity (notably dam building). This has imposed an important impact on OCBR in Chaohu Lake. This multi-sediment core study reveals the spatiotemporal characteristics of carbon burial in the lake and provides an important basis for increasing the accuracy of calculating carbon storage in large shallow lakes. 相似文献
17.
以内蒙古锡林郭勒盟苏尼特右旗的察干淖尔盐湖为研究对象,利用OSL(Optically Stimulated Luminescence)测年技术和DEM(Digital Elevation Model)数字高程模型,重建湖面波动历史,探讨湖泊形成与环境变化过程.通过对察干淖尔盐湖周边大量的野外考察,发现湖泊周围存在海拔高程为1020、978和973 m的三级古湖岸阶地,其OSL测年结果分别为29.2±1.3、18.4±0.8及8.2 8.0 ka.通过湖岸阶地高程恢复的上述3个时期的古湖面积分别为3600、500和400 km~2.与现今的干旱盐湖景观迥然不同. 相似文献
18.
Environmental records of lacustrine sediments in different time scales: Sediment grain size as an example 总被引：2，自引：0，他引：2
CHEN Jing’an WAN Guojiang David Dian Zhang ZHANG Feng & HUANG Ronggui . State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang China . Department of Geography Geology University of Hong Kong Pokfulam Road Hong Kong China 《中国科学D辑(英文版)》2004,47(10):954-960
Understanding the past is the key to know thepresent and to predict the future. As a core project ofthe International Geosphere Biosphere Program, PastGlobal Changes (PAGES) aims to reconstruct theevolution history of global climate, global environ-ment and global ecosystem with resort to all kinds ofnatural records, so as to reveal the change rules(change processes, change amplitude and change rate)of the global environment and thus provide scientificbasis for predicting climate changes p… 相似文献
19.
Impacts of regional warming on long‐term hypolimnetic anoxia and dissolved oxygen concentration in a deep lake 
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下载免费PDF全文 Although few reports have described long‐term continuous anoxia in aquatic systems, Lake Ikeda in Japan experienced such conditions in the hypolimnion from 1990 to 2010. The present study aimed to assess temporal fluctuations in the lake's thermal stability from 1978 to 2011 to understand the influence of regional climate change on hypolimnetic anoxia in this lake. Because complete vertical mixing, which supplies dissolved oxygen (DO) to the hypolimnion, potentially occurs on February, we calculated the Schmidt stability index (S) in February and compared it with hypolimnetic DO dynamics. Vertical water temperature profiles were calculated using a one‐dimensional model, and calculated temperatures and meteorological data were used to analyse annual fluctuations in water temperatures, thermocline depth, meteorological variables and S. We estimated that mean annual air and volume‐weighted water temperatures increased by 0.028 and 0.033 °C year?1, respectively, from 1978 to 2011. Between 1986 and 1990, S and water temperature increased abruptly, probably due to a large upwards trend in air temperature (+0.239 °C year?1). We hypothesize that a mixing regime that lacked overturn took effect at this time and that this regime lasted until 2011, when S was particularly small. These results demonstrate that abrupt climate warming in the late 1980s likely triggered the termination of complete mixing and caused the 21‐year period of successive anoxia in Lake Ikeda. We conclude that the lake response to a rapid shift in regional climate conditions was a key factor in changing the hypolimnetic water environment and that thermal stability in winter is a critical environmental factor controlling the mixing regime and anoxic conditions in deep lakes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
20.
Environmental characteristics of Mid-Holocene recorded by lacustrine sediments from Lake Daihai, north environment sensitive zone, China 总被引：4，自引：0，他引：4
One of the goals for paleaoenvironmental research is to predict the tendency of future climate and environmental changes based on the understanding of the past. The key approach is to find similar pictures which happened in the past. By understanding the background and mechanism of the paleaoenvironmen- tal changes, reliable parameters and verifications can be provided for the numerical model to predict the tendency of future climate and environmental changes. The Mid-Holocene as the nearest … 相似文献