Recharge to the inter-dune lakes and Holocene climatic changes in the Badain Jaran Desert, western China

We present new estimates on evaporation and groundwater recharge in the Badain Jaran Desert, western Inner Mongolia of northwestern China, based on a modified Penman Equation suitable for lakes in China. Geochemical data and water balance calculations suggest that local rainfall makes a significant contribution to groundwater recharge and that past lake-level variations in this desert environment should reflect palaeoclimatic changes. The chronology of lake-level change, established by radiocarbon and U-series disequilibrium dating methods, indicates high lake levels and a wetter climate beginning at ca. 10 ka and lasting until the late mid-Holocene in the Badain Jaran Desert. The greatest extension of lakes in the inter-dune depressions indicates that the water availability was greatest during the mid-Holocene. Relicts of Neolithic tools and pottery of Qijia Culture (2400-1900 BC) suggest relatively intensive human activity in the Badain Jaran Desert during the early and middle Holocene, supporting our interpretation of a less harsh environment. Wetter climates during the Holocene were likely triggered by an intensified East Asian summer monsoon associated with strong insolation.     

巴丹吉林沙漠潜水蒸发的数值模拟研究

为了确定巴丹吉林沙漠潜水蒸发强度与地下水埋深的关系,基于巴丹吉林沙漠的气候背景、砂土特征和不同地下水埋深时的典型植被特点设计了54种情景,利用Hydrus-1D建立不同情景下的SPAC水分运移模型,对周期性气象条件驱动下的潜水蒸发开展数值模拟。模拟结果表明:多年平均潜水蒸发量有着随地下水埋深增大而非线性减小的趋势;不同情景的极限埋深都大于3m,在埋深等于3m时潜水蒸发量都小于最大值的5%;当地下水埋深为0.5~1.5m时,潜水蒸发量对地下水埋深的变化最为敏感;当地下水埋深为1m时,潜水蒸发量对包气带岩性的变化也很敏感;在地下水埋深小于0.5m和大于1.5m的区间,气候、岩性、地下水埋深的变化对潜水蒸发量的影响变得微弱。另外,多年平均潜水蒸发量和地下水埋深的这种非线性关系可以用一个新提出的经验公式进行较为准确的拟合,将这个研究结果用于评价巴丹吉林沙漠湖泊集中区地下水的蒸发消耗,发现潜水蒸发总量显著大于湖面蒸发总量,前者约为后者的2.5~2.6倍,必须在沙漠水分平衡的分析中加以考虑。     

The Role of Groundwater in the Salt Lakes in the Badain Jaran Desert,China

正The Badain Jaran Desert is the second largest desert in China with tallest sand dunes on the earth.In contrast to the extremely dry climate,there are about 100 lakes spreading regularly over the depressions among high     

New Phenotypes of Limnocythere inopinata from Lakes in Badain Jaran Desert,Northern China

正Objective Limnocythere inopinata(Baird, 1843) is an ostracod widely distributed in recent non-marine waters and in Quaternary sediments, where it comprises various phenotypes(Yin et al., 1999; Zhang et al., 2015). Based on the nodation patterns, five phenotypes were described in previous publications, namely, the unnoded, the phenotype with one node in the postero-ventral part of the valve, one with two nodes in the antero-ventral and postero-ventral parts of the valve, another with three nodes in the antero-ventral, postero-ventral and postero-dorsal parts of the valve,     

Groundwater and lake evolution in the Badain Jaran Desert ecosystem, Inner Mongolia

The amount and timing of aquifer recharge and the evolution of lakes and groundwater in the south-eastern Badain Jaran desert of Inner Mongolia, with high megadunes, has been investigated using stable isotopes and hydrochemistry. Unsaturated zone moisture profiles down to 22 m have recorded recharge over 1185 years. Small but finite amounts of recharge are recorded with mean recharge rates of 0.95-1.33 mm year^?1, determined using a chloride mass balance technique. The unsaturated profile also acts as a unique archive of hydrological and climate change. Before 1300, it was relatively dry but distinct wet periods may be recognised during 1340-1450, 1500-1610 and 1710-1820. Since the mid 1800s, the climate shows a trend towards greater aridity. The interdune lakes are generally fresh but locally, hypersaline lakes are found in juxtaposition. This implies that in general, the lakes have low residence times and flow back into the dune system, but sedimentary obstruction locally prevents outflow and extreme evaporation occurs. The stable isotope records show that the lakes are fed by palaeowaters which on the basis of other proxy data must predate the Last Glacial Maximum. Their recharge source is problematic but most likely this derives from a diminishing water table extending some 30 m south to the Yabulai Mountains.     

干旱区地下水补给与气候变化的包气带地球化学记录--以巴丹吉林沙漠为例

氯平衡原理在降雨极其稀少的干旱区研究地下水补给具有较强的适用性,与H、O稳定同位素及含水量在包气带垂向的变化相结合,能够准确地计算地下水的多年平均补给率.在巴丹吉林沙漠南缘的2个钻孔剖面分别记录了过去574 a(B1)和812 a(B2)以来的补给量变化过程及其所反映的气候波动特征,在该地区,多年降雨量为89 mm,而补给量平均仅为1.3 mm/a,从B2剖面完整的记录可以将800 a B P气候划分为4个干期和3 个湿期.1500～1530年是干旱区气候突变的时期,18世纪末至19世纪初是气候环境演化的又一个十分重要的时间界限,自此以后的漫长时间,干旱化进程进一步加剧.     

Isotopic and hydrochemical data to restrict the origin of the groundwater in the Badain Jaran Desert,Northern China

Despite its extreme aridity, the Badain Jaran Desert is rich in groundwater. In the southeastern part of the desert, it is characterized by coexistence of high megadunes and a great number of lakes. Deuterium and oxygen 18 isotope compositions as well as hydrochemistry of groundwater, lake water, soil water and river water were investigated in detail to gain an insight into their relationships and the origin of the ground-water. The results show that the groundwater and the lake water are genetically related, but unrelated to local precipitation and the leakage of Heine River at northern slope of Qilian mountain. δD and δ¹⁸O values of deep soil water (lower than 40 cm) and groundwater plot on the same evaporation line E11, which shows that they have the same recharge source. The point of intersection between E11 and LMWL suggests that the groundwater originates from the water resource which has a weighted mean value that is lighter by some 6‰ δ¹⁸O than the local precipitation in Badain Jaran Desert. ³H data of water samples shows that the groundwater in Badain Jaran Desert originates from the water recharged after the nuclear test. The deep fault zone underground maybe the water circulation channel based on Helium analysis of groundwater. The result has guiding significance to rational exploitation and utilization of the local groundwater.     

Genesis and soil environmental implications of intact in-situ rhizoliths in dunes of the Badain Jaran Desert,northwestern China

Acta Geochimica - Desert rhizoliths are generally found as weathered, broken and scattered samples on dune field surface, but rarely in-situ in their initial states buried under the soil of desert...     

Geostatistical characterization of soil moisture and chloride distribution in deep vadose profiles of the Badain Jaran Desert,Northwestern China

Geostatistical analysis of soil moisture and ion accumulation can provide a deep understanding of aspects of a region’s hydrology such as recharge rates and flow paths. By combining this approach with detrended canonical correspondence analysis, the present study investigated the vertical and spatial variation of soil moisture and chloride (Cl^?) in vadose profiles of megadunes near lakes in the southeastern Badain Jaran Desert, northwestern China. Soil moisture varied vertically within the dune profiles following exponential, logarithmic, or log-normal distributions at different sites as a result of regulation by different local controls. The main local controls for Cl^? concentration were slope and orientation of the dune. Cl^? was not affected by local controls at depths >5 m. Sills of spatial variation in soil moisture and Cl^? in the variogram analysis were highly sensitive to local controls in the top 4 m of the profiles, and the values were three times those at depths >4 m. The lag for soil moisture was insensitive to local controls, and was 50–60 m in the top 4 m of the profiles and 20 m in deeper layers, whereas the lag for Cl^? was about 20 m at all depths. The results demonstrate that understanding recharge rates using factors such as Cl^? accumulation requires a careful survey to ensure that the local controls that regulate these factors are adequately accounted for.     

中国西北极端干旱区水文与湖泊演化及其巴丹吉林沙漠大型沙丘的形成

地表径流和地下水循环是维持中国西部现今极端干旱区绿洲、湖泊和地下水位变化的绝对主导因素。极少的年降水量和年际—季节降水分布的不均性、强烈的蒸发、蒸腾作用,稀少而水量有限的地表径流和人类活动的影响及其过度的水资源利用是导致目前自然景观和生态环境恶化的根本原因。不仅如此,在这样一个大的气候背景条件下,人类不合理、不科学的活动可以夸张的放大和加速生态系统的恶化程度和速度,而要维持、改善和修复已破坏的生态环境则需长期不懈的努力和巨大的人力、资金投入。地质断裂带不但具有蓄水、导水的作用,还具有隔水作用;断裂体系中含水量的丰寡与断裂的性质（张性或压性）、发育的地质部位和年代等因素有关。断裂构造对水的这种蓄—导—隔作用,在不同地理单元是不同的：在地势较高的部位以导为主,在低洼的地方则以蓄为主,而在前二者之间的过渡区则以导—隔为主。额济纳盆地地下水位变化和水资源（或潜在水资源）量的大小是以地表径流补给为主、地下水为辅,是区域蒸发、蒸腾和水资源利用之间平衡过程的表现;而在巴丹吉林沙漠区,特别是其东南部众多的湖泊区则是以地下水补给为主,加之以古水为辅。虽然我们还不十分清楚巴丹吉林沙漠内部高大沙丘和湖泊形成时期的相互作用和依存关系,但是我们却有足够的证据证明高大沙丘形态的维持与湖泊之间不存在必然的因果关系。直接通过阿尔金山断裂体系对额济纳盆地和巴丹吉林沙漠、腾格里沙漠水量的贡献是否真正存在还缺乏地质证据或者至少是十分有限。对中国西部干旱—极端干旱区水资源进行科学而深入、系统而规范、全面而统一的调查和规划,调整和协调,采用科学的流域管理模式,利用生态修复、动态调控、工程保障等措施对于维持整个流域生态环境的稳定和持续发展、维系中下游,特别是酒泉基地和额济纳绿洲是十分必要而迫切的。对于巴丹吉林沙漠东南部地下水和湖泊水的开发和利用的设想既不利于该区生态环境的维持和改善,也缺乏科学依据和工程的可行性。西北干旱—极端干旱区水文循环和水量是气候环境决定的,不仅现代如此,过去也是如此。     

内蒙古巴丹吉林沙漠400年来大气沉降 Hg的湖泊沉积记录

Hg污染具有全球性,人类活动较少地区的湖泊沉积物对长距离输入的大气沉降Hg变化敏感。巴丹吉林沙漠中发育了约142个沙漠丘间湖泊,是研究大气沉降Hg记 录的理想材料。选择巴丹吉林沙漠东南部的宝日陶勒盖湖泊进行湖泊钻探,结合²¹⁰Pb_uns和¹³⁷Cs核素测年及THg沉积通量计算,重建了400年来巴丹吉林沙漠湖泊的THg沉积记录,并探讨了影响沙漠湖泊THg沉积的影响因素,评估了自然背景和人类活动的影响。结果表明：(1)沉积物中THg含量分布范围为1.5~17.5 ng/g,富集系数和沉积通量的分布范围分别为0.3~4.5和2.9~38.9 μg/(cm²·a)。 THg含量、富集系数和沉积通量均表现为在岩心上部近几十年富集。(2)近400年来,湖泊沉积物中背景THg(THg_岩石风化)通量变化相对稳定,主要受控于附近物源供给和区域风沙活动。大气沉降THg(THg _大气)通量自20世纪30年代以来呈逐渐增加的趋势,很大程度上反映了近几十年来人为源大气沉降THg的增加。但20世纪30年代以来岩心局部的大气沉降THg通量的峰值可能还受全球变暖和湖泊生产力增加 的影响,而20世纪30年代之前出现的峰值可能与“小冰期”冷期强烈的区域风沙活动有关。巴丹吉林沙漠湖泊400年来的THg_大气沉积通量变化与全球Hg产量和冰心中的大气Hg含量变化记录一致,是沙漠 地区大气沉降THg的可信纪录。     

应用音频大地电磁法探测内蒙古巴丹吉林高大沙山结构及成因

巴丹吉林沙漠拥有世界罕见的高大沙山群。为了解巴丹吉林高大沙山结构与成因,应用音频大地电磁法进行测量,利用非线性共轭梯度法二维反演得到了沙山的横截电性剖面。沙山电性剖面深部呈现明显的低阻,而沙山中部存在一定规模高阻区域。判断巴丹吉林沙漠众多高大沙山群的形成是由其稳定的西北风作用、源源不断的地下水补给机制和特殊的地层环境共同作用的结果。地下水由于蒸腾作用上升遇到古老沙丘的钙质层阻挡,由背风坡底部蒸发出来。水蒸气凝结在顶部滚落的沙子表面,使其抗风蚀能力增强,起到固沙作用;随着时间推移,沙山越来越大,形成高大沙山。     

Climatic changes in the Chalbi Desert,North Kenya

The Chalbi flat, located 60 km outside the rift to the east, forms a moist, salt-clay encrusted playa which also functions as an inland sink for alluvial fans. Residual lacustrine beds, including freshwater carbonates and travertines, crop out along its higher periphery. Mammalian bones of lacustrine and terrestrial elements, and K/Ar dating of the capping lava suggest a lake or a swamp environment 2–2.5 million years ago. Radiocarbon dating of Melanoides tuberculata and Planorbis and a sediment assemblage composed of clotted micrite, calcareous molds, root marks and stromatolites point to an additional early Holocene Chalbi lake or swamps 11000-9500 yr BP. The data suggest wet environmental conditions outside the rift, which is consistent with the occurrence of a wet period in the early to middle Holocene in intertropical Africa, but out of phase with the climatic conditions in Sinai and Israel and with the high-latitude maximum lake levels and glacier advance. These relations have probably been caused by migration of climatic belts.     

放射性核素210Pb、137Cs测定巴丹吉林沙漠湖泊岩芯的年代及沉积速率

巴丹吉林沙漠发育了世界上独一无二的丘间湖泊群,100多个永久性的丘间湖泊分布于沙漠的东南部。沙漠湖泊岩芯是干旱地区重要的气候、环境档案,然而受沙漠湖泊发育极端环境的影响,岩芯测年面临很大挑战。本文选择巴丹吉林的沙漠南缘的阿尔吉林和敦德吉林进行钻探,获取无扰动岩芯,利用核素（210Pb、137Cs）进行测年,并计算其沉积速率。结果表明：（1）核素（210Pb和137Cs）测年能够获取巴丹吉林沙漠丘间现代湖泊岩芯的可靠年代。（2）岩芯Ar-1的CRS测年结果为102±8a,沉积速率分布范围为0.13 ~ 0.33cma-1,岩芯Dd-1的CRS测年结果为123±2a,沉积速率分布范围为0.18 ~ 0.70cma-1。（3）沙漠岩心沉积速率空间分布具有自沙漠腹地向边缘递增的趋势,210Pbuns-CRS平均沉积速率分布范围为 0.16 ~ 0.57cma-1 ,137Cs沉积速率分布范围为0.05 ~ 0.6 cm a-1。未来对于沉积速率空间变化的可能影响因素,如高大沙山的围限阻挡效应、137Cs的分子扩散效应以及古地震等,应进行更深入研究。     

150ka B.P.以来萨拉乌苏河流域主元素变动旋回

萨拉乌苏河流域米浪沟湾剖面150kaB.P.以来存在27个由风成砂与河湖相和古土壤构成的沉积旋回。通常后两者的Al2O3、TFe、Mn、TiO2、K2O、MgO、CaO和Na2O含量明显高于前者,而SiO2则相反,构成了与沉积旋回相应的150kaB.P.以来27个元素变化旋回。结合各元素的化学迁移特性、研究区所在的鄂尔多斯高原东南部洼地地貌特征以及季风沙区位置,论证了风成砂中SiO2含量增高,Al2O3、TFe、Mn、TiO2、K2O、MgO、CaO和Na2O相对降低,与干寒多风气候及其影响下石英的大量迁入有关,而河湖相和古土壤中SiO2相对迁移、Al2O3等呈聚集的势态,与暖湿气候作用下稳定性元素Al2O3、TFe、Mn、TiO2和非稳定性元素K2O、MgO、CaO、Na2O都能够从四周地表汇集于本区这种特殊的比较封闭的低地有关。研究表明,萨拉乌苏河流域150kaB.P.以来27个元素变化旋回与该时期北半球冰期-间冰期气候波动诱发的亚洲冬夏季风在毛乌素沙漠的多次更迭具有成因上的联系。     

哈萨克斯坦南部Shayan黄土粒度端元指示的14.4cal.ka B.P.以来的风尘历史

中亚干旱区不仅是全球主要的风尘源区之一, 也是气候变化的敏感区域之一。重建中亚干旱区风尘历史、解释其驱动机制对治理现代沙尘天气和改善人类生存环境至关重要。然而, 关于中亚干旱区风尘驱动机制的问题仍存在不同观点。本研究采用参数化粒度端元分析方法对哈萨克斯坦南部的Shayan黄土剖面(厚度约650cm)进行了分析。结果表明: 1)Shayan剖面沉积物粒度组分分为4个端元, EM1代表高空西风远距离搬运和以团聚体的形式被粗颗粒携带的粘土组分, EM2代表沉积时期大气粉尘的背景, 以浮尘的形式存在的细粉砂组分, EM3代表低空短距离搬运的近源粗粉砂组分, EM4代表较强风力条件下被搬运的局地砂粒组分; 2)EM3+EM4含量指示的风尘历史显示, 14.4cal.ka B.P.至早全新世阶段(14.4~8.2cal.ka B.P.)风力较强, 中全新世(8.2~4.2cal.ka B.P.)风力较弱, 晚全新世(4.2~0cal.ka B.P.)再次增强; 3)西伯利亚高压强度变化是中亚干旱区过去风尘活动变化的主要驱动力。

     

临夏黄土记录的26万年来季风快速变化

黄土高原西部高分辨率黄土序列开展的多代用指标研究,有助于揭示轨道-亚轨道尺度上东亚冬、夏季风的变化特征及动力机制。但针对同一地质记录提取冬、夏季风多代用指标进行对比和敏感性分析的工作尚不多见,因此制约了对季风快速变化特征和机理的理解。本文利用甘肃临夏85 m黄土岩芯开展高分辨率的粒度、磁化率和元素扫描分析,发现在轨道尺度上粒度和Zr/Rb比值显示的大幅冰期-间冰期波动与深海氧同位素记录有很好的对应关系,表明东亚冬季风的波动响应于北半球高纬冰量的变化。但在千年尺度上,粒度能更敏感地响应冬季风的快速变化;Rb/Sr比值和磁化率均能很好记录轨道尺度上的东亚夏季风波动,但在亚轨道尺度上Rb/Sr的敏感性明显高于磁化率。粒度、Zr/Rb和Rb/Sr所指示的东亚季风快速变化表现出较强的岁差信号,与石笋和北纬65°夏季太阳辐射有较好的对应关系,表明东亚季风变化也受到岁差直接驱动的夏季太阳辐射变的控制。在最后两个冰期-间冰期旋回中(即末期冰期旋回和倒数第二次冰期旋回)Rb/Sr及Zr/Rb比值和粒度记录分别可以辨别出与石笋相同数量级的变暖事件,但粒度记录的暖事件明显要多于Rb/Sr及Zr/Rb比值,且这些暖事件并不能一一对应。粒度及元素比值记录显著变冷的千年尺度的Heinrich(H)事件与石笋记录的夏季风明显减弱的事件有很好的对应关系,但其发生频率明显高于海洋记录。这些指标记录的千年尺度上波动信号的不一致性主要归因指标对不同气候要素敏感性的差异。未来需要进一步开展高分辨率多代用指标敏感性分析,选取对季风快速变化的敏感指标,有助于我们理解季风快速变化的特征(如周期和幅度等)和分析季风快速变化的时空差异性。