近200年来湖北涨渡湖对江湖联通变化的环境响应

江湖联通状况对湖泊生态系统有着重要影响,但是由于缺乏长期的生态水文监测数据,湖泊系统对其响应的过程与机理仍缺乏认识.本研究选择长江中下游地区典型湖泊——涨渡湖,结合该湖一沉积短柱的²¹⁰Pb、¹³⁷Cs年代测试,通过高分辨率的多指标分析(硅藻、元素地球化学和粒度),揭示近200年来湖泊生态系统对该湖与长江之间联通关系改变的响应过程.与历史文献记载一致,古湖沼学记录揭示出该湖与长江的联通状况经历了3个阶段.1)江湖联通期(1954年以前):该湖与长江自然相通,江湖水体交换频繁,丰富的贫营养浮游种Cyclotella bodanica表明该湖长期处于低营养及湖泊水位相对较高的状态.2)江湖隔绝期(1954 2005年):随着湖坝的兴建,江湖联通关系被隔绝,湖泊换水周期变长,透明度降低,喜好扰动环境的Aulacoseria granulata大量生长.相应地,富营养硅藻的增加、高TOC含量以及较高的沉积物TP、TN浓度表明,该湖营养水平逐渐升高.特别是近20年来,较高含量的富营养硅藻种——C.meneghinena、A.alpigena、Nitzschia palea、Surirella minuta和地球化学记录,包括TOC含量和沉积物TP、TN浓度,表明该湖富营养化程度加剧.3)江湖季节性联通期(2005年后):硅藻以附生种、底栖种为主,但仍有一定含量的富营养化属种,且TOC含量以及沉积物TP、TN浓度仍然保持较高水平,表明富营养程度有所缓解.古湖沼学和历史记录都揭示了自该湖与长江无连通后其生态状况的快速退化、重新联通后生态状况有所好转.因此,在长江中下游洪泛平原区,江湖关系的重新联通将是减轻湖泊生态压力的有效手段.     

青藏高原苟鲁错近几十年环境变化的湖泊沉积记录

通过对青藏高原苟鲁错湖泊沉积物碳酸盐含量,粒度、C值的综合分析,得出湖泊流域气候近几十年来气候呈干暖化趋势。另外,通过苟鲁错附近五道梁和沱沱河气象站统计资料和湖泊沉积特性的对比分析,说明通过碳酸盐、粒度、C值等综合指标对重建苟鲁错流域古气候是可行的,这为苟鲁错流域古气候重建提供了参考和依据。     

近30年来青藏高原羌塘地区东南部湖泊变化遥感分析

以多时相Landsat TM/ETM+影像、CBERSCCD影像和早期1∶10万地形图为数据源,选取羌塘高原东南部22个面积较大的湖泊作为研究对象,借鉴城市扩展研究的思路,引入变化强度指数和象限方位分析等方法,从面积、强度和空间分异特征等多个方面对该区湖泊近30年来的变化进行分析.结果表明,1975-2005年间研究区湖泊呈扩张趋势,总面积共扩大了1162.19km2;色林错扩张面积最多,达510.02km2,以北部扩张最为明显;国加轮湖扩张强度最大;造成区域内湖泊面积扩张的主要因素是冰雪融水量的增加、降水量的增多以及蒸发量的减少.     

云南错恰湖两百年来气候环境变化与重金属污染

高海拔地区由于特殊的自然环境对气候变化和营养输入的响应十分敏感.在人类活动逐渐加强的背景下,高山湖泊高分辨率的沉积物记录了人与自然相互作用的演变过程.选取云南西北部典型高山湖泊——错恰湖,获取长度37 cm的连续湖泊沉积序列,基于铅铯测年法得到年代深度模型,并对湖芯样品进行总有机碳、总氮及正构烷烃的多指标测定和元素测量,结合气象监测数据探讨分析错恰湖的有机质来源和流域环境演化特征.根据气候代用指标的变化,两百年来错恰湖泊环境及区域气候演化可以分成4个主要阶段：1807-1900年：湖泊水位上升、湖面扩大,有机质丰度下降,有机质以外源贡献为主,内源比例上升;1900-1950年：湖泊水位开始下降、湖面收缩,有机质丰度下降,外源有机质来源增加;1950-1982年：湖泊水位下降、湖面进一步收缩,有机质丰度下降,外源输入比例继续增加;1982-2007年：湖泊水位下降、湖面收缩,有机质含量上升且以陆源输入为主,同时内源贡献比例开始增加.在元素测定结果中,人类活动对应了湖泊沉积重金属含量变化的3个阶段：1950年以前,重金属含量低且稳定,可视作自然背景阶段,人类影响忽略不计;1950年以后,湖泊流域工农业逐渐发展,人为干扰凸显;直到1982年以后,冶炼工业的进步加强了重金属的污染态势,并通过大气传输沉降被湖泊沉积物记录.错恰湖沉积记录的分析讨论在总结该区域气候环境演化历史的同时,加深了对气候人类活动湖泊生态系统相互作用过程的理解,为高山湖泊响应人类活动影响提供了证据.     

青藏高原达则错近1000年来生态系统变化及可能机制

在全球变化的背景下,厘清湖泊生态系统对气候环境以及人类活动的响应机制对制定社会的适应政策非常重要.目前的研究手段如现场观测和围隔实验等可以很好地揭示湖泊生态系统在有观测记录以来的演替和变化过程,但是不能提供历史时期湖泊生态系统的变化及其对气候环境变化和人类活动的响应.古湖沼学可以为探讨湖泊生态系统的长期变化及其对气候环...     

滇西北地区高山湖泊沃迪错近两百年来环境变化及枝角类群落响应

区域增温和大气氮沉降作用已成为高山湖泊面临的重要环境胁迫,已有高山湖泊生物群落响应的长期模式研究主要集中于藻类而缺乏更高营养级生物(如浮游动物)的系统调查。本研究选择滇西北地区深水型的高山湖泊沃迪错开展沉积物调查,通过多指标分析(总氮、总磷、叶绿素a、氮稳定同位素等)并结合区域气候重建记录,识别近两百年来该湖泊及流域环境的变化历史,进一步利用枝角类群落指标(物种组成、生物量等)定量评价了湖泊生物群落的响应模式与驱动因子。结果表明,湖泊营养水平(如总氮浓度)和初级生产力(叶绿素a浓度等)在过去近两百年总体呈上升趋势。相关分析显示,大气氮沉降和流域外源输入是影响总氮上升的主要因素,同时区域增温和营养盐富集促进了湖泊初级生产力的不断上升。自1960s以来区域升温明显,湖泊营养水平和叶绿素a浓度呈现加速上升的趋势。钻孔中枝角类群落以浮游属种(Daphnia longispina等)为优势种,在1900AD以前D.longispina相对丰度较为稳定(40.83%±8.02%),之后出现下降趋势且在1948—1965年间明显下降,之后再次明显上升并成为主要优势种。排序分析显示,气温、叶绿素a和总...     

湖泊沉积物XRF元素连续扫描与常规ICP-OES分析结果的对比及校正--以兹格塘错为例

岩芯X荧光光谱扫描仪(XRF)可以无需破坏样品,直接通过对剖开岩芯表面扫描获知沉积物的元素化学组成,但目前少有关于XRF连续扫描方法测试结果精度和准确性的研究.本文以高原封闭咸水湖泊兹格塘错湖相沉积岩芯为研究对象,利用XRF方法进行了高分辨率连续扫描,同时在岩芯不同层位选取了60个样品利用ICP-OES方法进行元素测定...     

湖泊沉积物的矿物磁性测量及其环境应用

本文结合太湖沉积物的磁性研究，简要地阐述了湖泊沉积物磁性测量的方法与磁信息的环境应用，通过分析太湖沉积样芯的磁参数曲线所内含的环境信息，揭示了磁测方法在古湖沼学研究中的应用前景。     

西昆仑山南红山湖沉积反映的过去150年湖区环境变化

采用～２１０Ｐｂ和～１３７Ｃｓ方法对西昆仑山南红山湖 ２号孔（长 １．０７ ｍ）湖泊岩芯进行了定年和沉积速率研究，获得了分辨率达１．４年的过去约１５０年（１８５０～１９９７年）连续湖泊沉积环境序列．该沉积柱子的总有机碳、总氮、元素地球化学、碳酸钙、粒度、介形虫丰度等变化表明，这些环境代用指标具有很好的一致性，反映了湖区环境具有１９世纪下半叶的冷湿、１９世纪末期到２０世纪２０年代的暖湿和２０年代开始的暖干变化背景．２０年代以来又具有次一级的冷暖／干湿波动，可以划分为１９２２～１９６０年间的冷干／暖湿波动、１９６０年以来的强烈暖干化以及出现于７０年代中期到８０年代末期的短暂冷湿过程．其中，７０年代中期至末期的湿润时期和８０年代中期开始的干旱环境在邻近地区的器测气象记录中得到证实，粒度数据与器测降水记录具有较好的相关性．与同一地区的古里雅冰芯记录对比，该孔指示环境冷暖的代用指标（ＴＯＣ）与冰芯中代表温度变化的δ～１８Ｏ变化具有很好的对应关系，但指示干湿程度的指标与冰芯中代表降水大小的冰川积累量变化关系较差．该孔湖泊沉积记录表明，选取的代用指标具有明确的环境意义，湖芯序列能够反映高分辨率的气候环境变化．     

基于XRF岩芯扫描的Rb/Sr比值的古气候意义探讨——以青藏高原东部若尔盖盆地为例

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...     

Environmental changes reflected by the lake sediments of the South Hongshan Lake, Northwest Tibet

The 1.07-m long lake core with 1 cm interval cutting, which was obtained by drilling in the South Hongshan Lake of Northwest Tibet, was dated by the 210Pb and 137Cs methods, and a 150-year consecutive lake sedimentary sequence (1840─1997) with 1.4 year resolution was obtained. Some environmental proxies, such as the total organic carbon (TOC), total nitrogen (TN), ratio of TOC to TN (TOC/TN), trace chemistry elements (TCE), CaCO3, grain size, richness of ostracoda etc. showed that they are of well coincidence. These results implied that the environmental background varied from the cold-wet period in the late 19th century, to the warm-wet period from the end of the 19th century to the 1920s and to the warm-dry period since the 1920s. There were sub-variations since the 1920s: the cold-dry/warm-wet fluctuation from 1922 to 1960, the intensively warm-dry period since 1960 with a short cold-wet period in the mid-1970s to the end of the 1980s. The humid period from the mid-1970s to the end of the 1970s and the dry period beginning from the early 1980s were well documented by climatic data of the nearby weather station records while the grain size was well correlated to the annual precipitation. Compared with the records from Guliya ice core in the same area, the TOC proxy in the lake core indicating warm/cold conditions well corresponded to the ( 18O records representing temperature variations in the ice core. However, the proxies with dry/wet significance in the lake core were different from the variations of snow accumulation reflected by the ice core. It can be concluded that the chosen environmental proxies have clear environmental significance and the lake sediments can reflect climatic and environmental changes at high-resolution.     

A high-resolution palaeoclimate record for the last 4800 years from lake la Brava,SE pampas plains,Argentina

Climatic changes are reflected in variations of different parameters. Sequences of lake sediments are good sources of this information because they provide continuous and detailed records of palaeoclimatic changes. In order to determine the changes in climate in SE Pampas plain, in this paper we present a series of rock magnetic studies performed on a bottom core collected from Lake La Brava (Argentina).In order to establish lake level variations, we also measure total sulphur, organic and inorganic carbon (TS, TOC and TIC) content, alkaline elements, light and heavy metals and changes in vegetation communities. Five radiocarbon age determinations were made from samples of organic-rich clay and calibrated ages were calculated. The averaged sediment accumulation rate is 1.3 mm/yr and the sequence represents a temporal extent of about 4800 calibrated years before the present (cal. BP).The main aim was to reconstruct the hydrological balance of the lake, the changes in erosional strength and sediment supply within the catchment area since the Middle Holocene, and to explore the extent to which these may be linked to changes in climate and/or human activities. The results of this work and previous studies suggest periodic changes from cooler to warmer and humid conditions. Relationships between submerged and emergent plants are consistent with the behaviour of magnetic susceptibility. TOC changes suggest wet environment during magnetic enhancement. Floods and lower lake level events were identified in detail. Changes in sediment contribution and depositional processes for the last 50 cal. BP are caused by human impact, particularly by the use of natural resources.     

浅钻岩芯揭示的固城湖4000年来环境演化

对固城湖6.2m深的现代沉积物柱状岩芯进行了放射性同位素、粒度、有机质含量、有机质σ~(13)C和孢粉分析。沉积记录巾各项环境指标的变化表明,4ka以来固城湖经历了高湖面—低湖面—高湖面的显著变化。气候变化是影响湖泊环境演化的重要自然因素,但2.5ka以来人类活动对湖泊演化的影响显得更为明显。特别是2.5ka和1.1ka两次人类对湖泊水系的改造是引起湖泊环境两次突变的主要因素。     

Quantitative recuperation of climatic sequences for the last 200 years in Xingcuo Lake,eastern Tibetan Plateau

The functional relation between theδ18O values in the shell of gastropod Gyraulus sibirica and the air temperature in the warm half-yearly period, and that between Sr/Ca ratio and the precipitation in the warm half-yearly period were established by calibrating the δ18O and δ13C values, Sr/Ca ratio and Mg/Ca ratio in the shell Gyraulus sibirica, as well as the total organic carbon (TOC) and its δ13C values in the Xingcuo Lake sediment in the eastern Tibetan Plateau. The sequences of air temperature and precipitation in the last 200 years in the region were quantitatively recuperated on this basis. The results showed the following: (i) There was a negative correlativity between Sr/Ca ratio and the precipitation in the warm half-yearly period, its correlation coefficient was 0.86. (ii) There was an obviously positive correlativity between indexδ18O and the running average temperature in the warm half-yearly period, its correlation coefficient was 0.89. (iii) Evolution of the air temperature and the precipitation in the last 200 years can be divided into three phases distinctly. The precipitation in the later mid-19th century was 220 mm higher than that today; the air temperature in the warm half-yearly period was 2℃ lower than that of the present. The precipitation in the minimum air temperature period of the early 20th century was below that today by 60 mm, and the air temperature in the warm half-yearly period was 3.4℃ lower than that today. (iv) An evidently warming and drying trend existed in the last five decades.     

2.5ka来新疆吉力湖湖泊沉积记录的气候环境变化

选择位于西风区的吉力湖为研究对象,利用~(210)Pb、~(137)Cs和AMS~(14)C测年手段,建立了吉力湖沉积岩芯2.5ka以来的时间序列。对湖泊沉积物的粒度、总有机碳、总氮以及有机碳同位素等多环境指标的综合分析,重建了吉力湖2.5ka以来的气候环境演化特征。2.5ka以来吉力湖气候环境变化大致经历了5个阶段:500BC-50BC,暖干;50BC-650AD,冷湿,气候不稳定,冷暖波动较大;650-1350AD,暖干,对应于中世纪暖期(MWP),1350-1850AD,冷干,对应于小冰期(LIA);1850AD以来,温干,其中20世纪20年代后,尤其是70年代以来,气候变暖。吉力湖多环境指标记录的气候环境变化与其它地质记录以及历史文献记录均具有较好的一致性。     

Climatic and environmental changes over the last millennium recorded in the Malan ice core from the northern Tibetan Plateau

In this paper, climatic and environmental changes were reconstructed since 1129A.D. based on the Malan ice core from Hol Xil, the northern Tibetan Plateau. The record of δ 18O in the Malan ice core indicated that the warm-season air temperature variations displayed a general increase trend, the 20th-century warming was within the range of natural climate variability, and the warmest century was the 17th century while the warmest decade was the 1610s, over the entire study period. The “Medieval Warm Epoch” and “Little Ice Age” were also reflected by the ice core record. The dust ratio in the Malan ice core is a good proxy for dust event frequency. The 870-year record of the dust ratio showed that dust events occurred much frequently in the 19th century. Comparing the variations of δ 18O and the dust ratio, it is found that there was a strong negative correlation between them on the time scales of 101―102 years. By analyses of all the climatic records of ice cores and tree rings from the northern Tibetan Plateau, it was revealed that dust events were more frequent in the cold and dry periods than in the warm and wet periods.