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重建黄旗海水位、水化学和湖泊生物学变化历史可为研究我国夏季风边缘区冰后期气候变化提供重要环境记录。对该湖中央HQH4岩芯研究结果显示,末次冰期晚期沉积物中湖泊自生有机质烧失量和自生碳酸盐烧失量的平均值分别仅为全新世沉积物的1/13和1/5,造成这种结果的主导因素是夏季气温在全新世初显著升高和黄旗海从此进入稳定的湖泊环境。晚全新世自生碳酸盐烧失量平均值比早、中全新世低14%,其最大值也明显低于早、中全新世,这种情况很可能是因为晚全新世夏季温度略低于早、中全新世所致。自生有机质和碳酸盐烧失量是快速、经济地获取闭流型半咸水湖泊冰后期环境变化的有效代用指标。 相似文献
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黄旗海岩芯烧失量分析与冰后期环境演变 总被引：3，自引：1，他引：2
重建闭流型湖泊的水位及环境变化,可以为研究冰后期及全新世以来的气候变化及季风环流演变提供不可或缺的关键信息。对HQH4岩芯烧失量与川蔓藻化石种子的研究结果显示,黄旗海湖区在全新世到来之前的气候寒冷,湖面冰封期较长,夏季温度较低,致使湖泊的有机生产率和自生碳酸盐产量比全新世低很多。黄旗海从全新世早期起进入了稳定的湖泊发展阶段后有机生产率显著上升,自生碳酸盐产量同步大幅度增长。在10 200~6 800 a BP期间,烧失量出现显著波动,很大程度上反映了气候发生暖湿-冷干-暖湿-冷湿的变化。在6 800~3 800 a BP期间,烧失量较高而且波动较小,反映了中全新世黄旗海以稳定的温暖湿润气候为主,湖水水位变化不大,有机质和碳酸盐生产力较高。从3 800 a BP起,气候逐渐变凉,间有多次冷暖干湿的剧烈变化,水位波动频繁。 相似文献
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岱海湖泊沉积物频率磁化率对历史时期环境变化的反映* 总被引：52，自引：4，他引：48
在探讨封闭湖泊沉积物频率磁化率的环境意义的基础上,根据岱海DH32孔湖泊沉积物磁化率的测量结果,结合粒度、孢粉、历史资料和硅藻分析结果,对岱海历史时期的环境变化进行了探讨。研究认为:历史时期内陆封闭湖泊沉积物频率磁化率高值段指示气候偏湿阶段;低值段指示气候干旱阶段;DH32孔湖泊沉积物频率磁化率反映的近300年来岱海气候变化可划分七个阶段,并与粒度、孢粉、硅藻和历史资料的分析结果基本一致。湖泊沉积物频率磁化率是恢复历史时期环境变化的重要环境指标之一。 相似文献
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选择青藏高原腹地可可西里为研究区,通过对该区湖泊沉积物粒度参数的分析,并且与其他环境代用指标进行比较。探讨了中更新世以来可可西里地区的环境演变。结果表明：粒度参数的变化特征可以很好的指示湖泊水位的变化,能反映湖区气候的变化情况,而粒度参数所指示的湖泊水位波动及环境变化得到了其他环境代用指标很好的支持了。说明对沉积物粒度研究是恢复区域气候环境变化的一种有效途径。同时该区湖泊沉积物粒度参数的变化规律和深海氧同位素曲线在冰期-间冰期旋回尺度上有较好的一致性,但也出现不同的变化特征,说明本区既表现出全球一致的气候特征,但也受区域气候变化影响,这可能与青藏高原的抬升有一定关系,因此,本研究对研究区域气候与全球气候之间的关系有重要意义。 相似文献
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选择青藏高原腹地可可西里为研究区,通过对该区湖泊沉积物粒度参数的分析,并且与其他环境代用指标进行比较,探讨了中更新世以来可可西里地区的环境演变。结果表明:粒度参数的变化特征可以很好地指示湖泊水位的变化,能反映湖区气候的变化情况,粒度参数所指示的湖泊水位波动及环境变化得到了其他环境代用指标很好的支持,说明对沉积物粒度研究是恢复区域气候环境变化的一种有效途径。同时该区湖泊沉积物粒度参数的变化规律和深海氧同位素曲线在冰期—间冰期旋回尺度上有较好的一致性,但也出现不同的变化特征,表明这一区域既有与全球一致的气候特征,也受区域气候变化影响,其原因可能与青藏高原的抬升有一定关系。 相似文献
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青藏高原西北部湖泊沉积物记录了丰富的区域气候环境变化信息,对于揭示青藏高原西风-季风环流系统变化及其相互作用过程具有重要意义。通过对青藏高原西北部高海拔干旱区典型湖泊阿克赛钦湖沉积岩芯粒度、总无机碳（Total inorganic carbon,TIC）、总有机碳（Total organic carbon,TOC）、总氮（Total nitrogen,TN）、碳氮比（C/N）和磁化率等环境代用指标的分析,探讨阿克赛钦湖不同沉积深度范围内湖泊水动力搬运条件、湖面变化及湖区冷暖变化等湖泊环境变化过程。结果表明：阿克赛钦湖沉积物有机质含量低,湖泊沉积物以粉砂为主,黏土次之,砂含量最少。多指标记录的环境变化大致分为以下4个阶段：第Ⅰ阶段（531～480 cm）气候相对温暖,流域蒸发较弱,湖泊水生生产力低,为湖泊水动力搬运条件弱的深水环境。第Ⅱ阶段（480～380 cm）气候寒冷干燥,流域蒸发强烈,湖泊水生生产力相对较高,为湖泊水动力搬运条件强的浅水环境。第Ⅲ阶段（380～160 cm）气候逐渐转暖,入湖水量增多,湖面扩张,湖泊水动力搬运条件逐渐减弱。第Ⅳ阶段（160～0 cm）气候寒冷干燥,流... 相似文献
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报道了大柴旦盐湖DC1303沉积剖面硼矿层及其下伏沉积地层的矿物学、有机质烧失量（LOI）等环境指标的研究结果,首次探讨硼矿层下伏灰黄色粉砂质粘土层沉积以来大柴旦湖水水化学演变及其与区域气候变化的关联。根据剖面的岩性、矿物组合和有机质烧失量（LOI）将研究剖面划分为3个沉积单元：I．灰黄色粉砂质粘土层（623～423cm）、II．灰黑色淤泥夹结核层（423—407cm）、III．柱硼铁石矿层（407—395em）。研究结果表明,在湖底硼矿层形成之前的较长时期内,大柴旦湖是碎屑沉积为主的非盐湖相沉积环境,直到单元I顶层20cm沉积物中才开始出现少量石膏。此后快速进入硫酸盐型盐湖沉积阶段（II）和湖底柱硼镁石矿层形成阶段（Ⅲ）。有机烧失量在I1、I2和I3单元中呈阶段性增加预示区域气温稳步上升,由此导致山区降水量增加和湖区蒸发量增强。湖泊环境变化是区域水文气候条件改变的结果。 相似文献
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对东南极拉斯曼丘陵莫愁湖ZH沉积柱进行了生态地质学的研究,通过AMS-14C定年构建年龄框架,采用550℃烧失量、粒度和元素地球化学指标等,恢复了中晚全新世该地区较高分辨率的湖泊生物量记录。结果显示,距今6600-6100年、5400-4800年、4650-3750年和3500年-2850年为莫愁湖生物量高值期,气候相对温暖适宜,湖泊生产力旺盛;距今6100-5400年、4800-4650年和3750-3500年为湖泊生物量低值期,气候相对寒冷,湖泊生产力相对较弱。而且在整体较暖的气候环境下,出现了其它无冰区沉积物中鲜有记录的距今4800-4650年、4400年前后和3750-3500年的气候快速变冷事件。根据莫愁湖湖泊生物量恢复的东南极拉斯曼地区高分辨的气候变化特征,与太阳活动强度和东南极大陆冰芯记录相吻合,为东南极中晚全新世多样的气候格局研究提供了新的依据。 相似文献
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Jamie G. Smith 《Geografiska Annaler: Series A, Physical Geography》2003,85(1):91-97
The loss‐on‐ignition (LOI) technique for organic matter determination is evaluated with reference to clay‐rich, glaciolacustrine sediments. Examples of the use of LOI in glaciolacustrine literature are inconsistent in their methodology, and standardisation is called for. Problems with application of the technique to glaciolacustrine sediments stem mainly from the effects of additional weight loss due to release of structurally bound water and exposure time to ignition temperatures. Exposure time should be increased from 1 hour to 2.5 hours in the light of significant additional weight loss occurring between 2 and 2.5 hours in clay‐rich samples. The reason for this sudden increase in LOI after 2 hours (up to 86% of total LOI in some cases) appears to be the build‐up of a distinct surface crust during heating that insulates the core of the sample from ignition temperatures. Some time between 2 and 2.5 hours, the crust breaks down and exposes the sample core to ignition temperatures, increasing weight loss significantly. Overestimation of LOI due to loss of structural water is thought to be insignificant. Replicates of LOI at 550 and 1000°C in non‐calcareous, clay‐rich (>40%) sediments, show differences of <0.25%, which, for the purpose of inferring broad changes in glacier extent in lake catchments, is an acceptable error. 相似文献
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Bryan Shuman 《Journal of Paleolimnology》2003,30(4):371-385
Loss-on-ignition analysis of Quaternary lake sediments provides an inexpensive and easy way to investigate past environmental changes. The mass loss on ignition at 550 °C (LOI) from lake sediment cores may vary because of temporal changes in: (1) sediment composition controlled by factors such as productivity, inorganic inputs, and decomposition; and (2) the patterns of sediment accumulation controlled by factors such as basin morphology and water level. Climatic changes can alter both. Here, modern surface samples and transects of sediment cores, collected across small (<10 ha), shallow (<4 m) lakes in the northeastern United States, show that LOI varies little (2–5%) across the deep portions of these small lakes at a given time. Large changes in LOI occur only at the transition into the littoral (shallow) zone. LOI variations in sediment cores that exceed 2–5%, therefore, appear to represent meaningful environmental changes. However, because of the many possible controls, changes in the LOI of a single core are often hard to interpret. Multiple cores increase the interpretability. At lakes studied here, similar LOI trends among several cores confirm that some LOI changes resulted from basin-wide shifts in sediment composition. Differences among cores, however, developed during the early- and mid-Holocene and indicate that the edge of the littoral zone moved towards the centers of the lakes during two periods of low lake levels, at ca. 11 000–8000 and ca. 5400–3000 cal yr B.P. The basin-wide balance of sediment sources controlled the LOI from deep-water sediments, but sedimentation patterns, which changed as lake levels changed, were also important. LOI differences among cores may therefore help identify past lake-level changes in other lakes. 相似文献
13.
Loss on ignition as a method for estimating organic and carbonate content in sediments: reproducibility and comparability of results 总被引：59，自引：0，他引：59
Five test runs were performed to assess possible bias when performing the loss on ignition (LOI) method to estimate organic matter and carbonate content of lake sediments. An accurate and stable weight loss was achieved after 2 h of burning pure CaCO3 at 950 °C, whereas LOI of pure graphite at 530 °C showed a direct relation to sample size and exposure time, with only 40-70% of the possible weight loss reached after 2 h of exposure and smaller samples losing weight faster than larger ones. Experiments with a standardised lake sediment revealed a strong initial weight loss at 550 °C, but samples continued to lose weight at a slow rate at exposure of up to 64 h, which was likely the effect of loss of volatile salts, structural water of clay minerals or metal oxides, or of inorganic carbon after the initial burning of organic matter. A further test-run revealed that at 550 °C samples in the centre of the furnace lost more weight than marginal samples. At 950 °C this pattern was still apparent but the differences became negligible. Again, LOI was dependent on sample size.An analytical LOI quality control experiment including ten different laboratories was carried out using each laboratory's own LOI procedure as well as a standardised LOI procedure to analyse three different sediments. The range of LOI values between laboratories measured at 550 °C was generally larger when each laboratory used its own method than when using the standard method. This was similar for 950 °C, although the range of values tended to be smaller. The within-laboratory range of LOI measurements for a given sediment was generally small. Comparisons of the results of the individual and the standardised method suggest that there is a laboratory-specific pattern in the results, probably due to differences in laboratory equipment and/or handling that could not be eliminated by standardising the LOI procedure.Factors such as sample size, exposure time, position of samples in the furnace and the laboratory measuring affected LOI results, with LOI at 550 °C being more susceptible to these factors than LOI at 950 °C. We, therefore, recommend analysts to be consistent in the LOI method used in relation to the ignition temperatures, exposure times, and the sample size and to include information on these three parameters when referring to the method. 相似文献
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Spatial variability in surface sediment composition characterised by near-infrared (NIR) reflectance spectroscopy 总被引：1，自引：0，他引：1
Tom Korsman Mats B. Nilsson Karin Landgren Ingemar Renberg 《Journal of Paleolimnology》1999,21(1):61-71
Near-infrared (NIR) spectral data were obtained from 165 surface sediment samples from a northern Swedish humic, mesotrophic lake (0.5 km2). The NIR spectra, together with data on water depth and loss-on-ignition (LOI), allow an evaluation of the source of spatial variance in sediment characteristics. The results show that water depth and organic matter (LOI) account for 20 and 16%, respectively, of the variance in the NIR-absorbance data. More importantly, the spatial variance in the spectral data suggest that NIR analysis of lake sediments mainly reflect sediment properties that cannot simply be explained by depth or amount of organic matter. The influence of inlets and land-use (e.g. clear-cutting) on sediment characteristics was more pronounced in the spectral data than would be expected from the LOI data. This is explained by differences in the chemical composition of the organic matter, as revealed by NIR spectroscopy, rather than in the amount of organic matter or depth-related sedimentation properties (e.g. particle size or density). This initial attempt to characterise sediment properties using NIR suggests that NIR analysis might become a valuable complementary tool to traditional sediment characterisation. 相似文献
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Loss on ignition: a qualitative or quantitative method for organic matter and carbonate mineral content in sediments? 总被引：5，自引：7，他引：5
Juan I. Santisteban Rosa Mediavilla Enrique López-Pamo Cristino J. Dabrio M. Blanca Ruiz Zapata M. José Gil García Silvino Castaño Pedro E. Martínez-Alfaro 《Journal of Paleolimnology》2004,32(3):287-299
Since the publication of the paper of , loss on ignition (LOI) has been widely used as a method to estimate the amount of organic matter and carbonate mineral content (and indirectly of organic and inorganic carbon) in sediments. The relationships between LOI at 550 °C (LOI550) and organic carbon (OC) content and between LOI at 950 °C (LOI950) and inorganic carbon (IC) content are currently accepted as a standard. However, the comparison of 150 analyses of samples of diverse lithologies, collected from a single core, reveals that these relationships are affected by sediment composition (presence of clays, salts, and the variable content of organic carbon). This results in an incremental error on the estimation of carbon content from LOI values that invalidates the use of LOI values as a quantitative method for estimating carbon content. Conversely, the general trends of LOI550 and LOI950 show a good correlation with carbon content (both organic and inorganic) allowing use of LOI as a qualitative test for carbon content. Similarly, in our case, LOI at 105 °C (LOI105) is a good qualitative proxy for the trends in gypsum content. 相似文献
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Byron Winston Sonja Hausmann Jaime Escobar William F. Kenney 《Journal of Paleolimnology》2014,51(3):393-403
Reservoir sediments are used cautiously in paleolimnological studies because of dating uncertainties, possible sediment disturbances and even concerns that indicators of trophic status may behave differently in reservoirs as opposed to natural lakes. We measured loss on ignition (LOI), carbon to nitrogen ratio (C:N), diatom abundance, total nitrogen (TN), total phosphorus (TP), TN:TP ratio, and carbon and nitrogen isotopes (δ13C and δ15N) in an 83-cm sediment core to track recent trophic status changes in Beaver Reservoir, Northwest Arkansas, USA. Measurements showed that LOI, TN, TP and diatom abundance increased significantly from the bottom to the top of the core (p < 0.001). The C:N ratio and δ13C indicated a predominantly algal source for organic matter in the sediments. Increases in TN and TP were positively correlated with human population growth (p < 0.01) and the TN:TP ratio recorded a shift from phosphorus to nitrogen limitation around 1990. This shift may have encouraged cyanobacterial growth that caused episodes of taste and odor problems in the reservoir. This study suggests that despite concerns about sediment dating and disturbance, reservoir sediments can provide valuable information on past water quality changes. 相似文献