藏南沉错湖泊三角洲的沉积相及沉积环境

在西藏自治区沉错湖泊三角洲平原和湖内钻孔取芯 ,利用14 C和ESR测年方法建立了钻孔剖面的年代标尺。在岩芯描述、沉积物粒度分析和CaCO3含量分析基础上 ,对沉错湖泊三角洲的沉积环境和沉积相进行了解释分析。 36 7m长的岩芯大致记录了 5 5万年以来的沉积历史。全孔平均沉积速率约为 0 6 6 7mm/a。 16 92 0aBP以来三角洲的沉积速率较大 ,平均为 1 2 7mm/a。由于沉积物物质来源的多源性导致CaCO3在剖面上的无规律性变化。但是 ,沉积物粒度和沉积序列变化指示全套沉积由底部的冲积扇相向上过渡为水下扇亚相和三角洲沉积相。在大约 175 0 0aBP～ 14 0 0 0aBP时期 ,沉错存在高湖面阶段。沉积序列中记录了末次冰期最盛期 (LastGlacialMaximum )和新仙女木事件 (YoungerDryas)。沉积特征和沉积环境的变化主要受湖面涨缩变化所控制。而湖面升降变化的驱动因素主要为气候 ,尤其夏季风的强弱和冷事件     

黑河调水对下游生态环境恢复效果的卫星遥感监测分析

利用2002年7月至2003年9月EOS/MODIS资料, 计算了黑河尾闾湖——东居延海重新出现后水域面积并分析其变化特征; 通过对2002和2003年6~8月黑河下游额济纳旗和古日乃绿洲植被指数的对比分析, 了解黑河调水对下游植被恢复的效果。结果表明: 东居延海重新出现后仍为季节性湖泊, 其面积2002年初冬最大, 2003年春季迅速减小并于6月6日干涸。随着中游地区再次向下游调水, 2003年8月中旬东居延海再次出现, 干涸时间为70d, 较前些年大大缩短。东居延海再现后对位于河道周围的额济纳旗绿洲植被恢复效果比较明显, 对远离河道的古日乃绿洲植被生长影响不显著。     

盐湖水化学类型的判别分析研究

应用判别分析分类技术研究了盐湖水化学类型。结果表明,用统计分析方法筛选出的变量(X1～X8)对区分盐湖水化学类型有显著作用。考虑这些变量,依据判别分析分类技术建立了盐湖水化学类型的数学模型。其判别函数可以成功地对盐湖样品进行水化学类型的判别或预测。     

硼酸盐水溶液中硼物种的存在形式及影响因素

根据以往相关的研究报道,综述了含硼水溶液中硼物种的存在形式,及其与总硼浓度、溶液pH值、溶液离子强度、温度、压力等因素的关系。随着总硼浓度的提高,硼氧配阴离子的聚合度加大,在pH值较高或较低时,聚硼离子的含量较少,主要以H3BO3和B(OH)4-的形式存在;同时,指出含硼水溶液存在普遍的过饱和现象,我国含硼盐湖卤水中的硼物种可以用B4O72-的综合统计形式表示。总结了硼酸盐水溶液中各种硼氧配阴离子的FT-IR,Raman和NMR的归属。     

小冰期气候的研究进展

小冰期是近2ka来的一个重要气候事件,又是目前全球变暖的背景事件,已成为古气候和古环境研究的热点。对此,科学工作者已经做了大量的研究。本文广泛综合前人研究的成果,介绍了小冰期的概况,认为1450-1890年是小冰期的时限,在此期间有三次冷期和两次暖期。冷期发生在1450-1510年、1560-1690年和1790-1890年,其中第二次冷期表现最甚;暖期发生在1510-1560年和1690-1790年。太阳活动和火山活动是小冰期气候变化的主要因素。并重点从冰芯、树轮、湖泊沉积、历史文献和沙漠地层等方面综述了近年来国内外对小冰期气候变化的研究现状。     

The effect of temperature‐humidity similarity on Bowen ratios,dimensionless standard deviations,and mass transfer coefficients over a lake

Similarity between heat and water vapor turbulent transport in the Atmospheric Surface Layer has been the basis of many engineering models to calculate surface fluxes, including the widely applied Bowen ratio equation, for a long time. Modernly, it is best understood within the context of Monin‐Obkhov Similarity Theory (MOST). In this work we study similarity between temperature and humidity, the Bowen ratio, and turbulent mass and heat transfer coefficients over a tropical lake in Brazil (Furnas Lake). The analysis was partly based on the concept of ‘Surface flux numbers’ recently proposed to diagnose scalar similarity, and considered wind directions and flux footprints. A period of 50 days of 30‐min. micrometeorological runs was used. Several cases of dissimilar temperature‐humidity behavior were found in the data. Both footprint extent and an aggregate temperature‐humidity Surface flux number turned out to be insufficient to diagnose these situations, but separate flux numbers for each scalar were able to diagnose their individual conformity to MOST. Overall, temperature displayed consistently larger relative variances and fluxes in comparison with humidity. The results highlight the need of careful analysis when measurements are made at sites close to land, when flux footprints may extend over there, indicating the possibility of advection effects. Copyright © 2016 John Wiley & Sons, Ltd.     

Groundwater ‐ the disregarded component in lake water and nutrient budgets. Part 1: effects of groundwater on hydrology

Lake eutrophication is a large and growing problem in many parts of the world, commonly due to anthropogenic sources of nutrients. Improved quantification of nutrient inputs is required to address this problem, including better determination of exchanges between groundwater and lakes. This first of a two‐part review provides a brief history of the evolution of the study of groundwater exchange with lakes, followed by a listing of the most commonly used methods for quantifying this exchange. Rates of exchange between lakes and groundwater compiled from the literature are statistically summarized for both exfiltration (flow from groundwater to a lake) and infiltration (flow from a lake to groundwater), including per cent contribution of groundwater to lake‐water budgets. Reported rates of exchange between groundwater and lakes span more than five orders of magnitude. Median exfiltration is 0.74 cm/day, and median infiltration is 0.60 cm/day. Exfiltration ranges from near 0% to 94% of input terms in lake‐water budgets, and infiltration ranges from near 0% to 91% of loss terms. Median values for exfiltration and infiltration as percentages of input and loss terms of lake‐water budgets are 25% and 35%, respectively. Quantification of the groundwater term is somewhat method dependent, indicating that calculating the groundwater component with multiple methods can provide a better understanding of the accuracy of estimates. The importance of exfiltration to a lake budget ranges widely for lakes less than about 100 ha in area but generally decreases with increasing lake area, particularly for lakes that exceed 100 ha in area. No such relation is evident for lakes where infiltration occurs, perhaps because of the smaller sample size. Copyright © 2014 John Wiley & Sons, Ltd.     

Monitoring of water surface temperature of Eurasian large lakes using MODIS land surface temperature product

In this study, data from MODIS land surface temperature product level 3 (MOD11A2) were used to investigate the spatiotemporal variation of Eurasian lakes water surface temperature (LSWT) from 2001 to 2015, and to examine the most influencing factors of that variation. The temperature of most lakes in the dry climate zone and in the equatorial climatic zone varied from 17 to 31°C and from 23 to 27°C, respectively. LSWTs in the warm temperate and cold climatic zones were in the range of 20 to 27°C and −0.6 and 17°C, respectively. The average day time LSWT in the polar climate zone was −0.71°C in the summer. Lakes in high latitude and in the Tibetan Plateau displayed low LSWT, ranging from −11 to 26°C during the night time. Large spatial variations of diurnal temperature difference (DTD) were observed in lakes across Eurasia. However, variations in DTDs were small in lakes located in high latitude and in tropical rainforest regions. The shallow lakes showed a rapid response of LSWT to solar and atmospheric forcing, while in the large and deep lakes, that response was sluggish. Results of this study demonstrated the applicability of remote sensing and MODIS LST products to capture the spatial–temporal variability of LSWT across continental scales, in particular for the vast wilderness areas and protected environment in high latitude regions of the world. The approach can be used in future studies examining processes and factors controlling large scale variability of LSWT.     

Hydrogeomorphic processes of thermokarst lakes with grounded‐ice and floating‐ice regimes on the Arctic coastal plain,Alaska

Thermokarst lakes cover > 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded ice) and deeper lakes maintaining perennial liquid water (floating ice). Thus, lake depth relative to maximum ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum ice thickness by analysing remotely sensed, water quality, and climatic data over a 35‐year period. Shoreline erosion rates due to permafrost degradation ranged from < 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P ? E_L) with periods of full and nearly dry basins. Shorter‐term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long‐term record for only shallow lakes. Our analysis suggests that grounded‐ice lakes are ice‐free on average 37 days longer than floating‐ice lakes resulting in a longer period of evaporative loss and more frequent negative P ? E_L. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum ice thickness in ACP lakes. Copyright © 2011 John Wiley & Sons, Ltd.