东亚季风区石笋δ13C是否记录植被变化:从川东北石笋记录的Heinrich事件说起     

程珂  谢宇  刘粤峰  李汉杰  潘晨光  彭小桃  刘淑华  陈琼  周厚云 《第四纪研究》2019,(4):837-844

以往的研究中一般认为石笋δ13C变化的影响因素复杂,但在大多数报道中地表植被仍被认为是影响石笋δ13C变化的主要因素之一.本文综合国内外已发表的模拟试验研究结果及川东北地区已发表和未发表的石笋δ18O-δ13C数据,特别是Heinrich事件中石笋δ18O-δ13C的表现,指出地表植被不一定是影响石笋δ13C变化的主要因素,洞穴水文(如地下水流速、滴水速率、水文化学,等等)的变化可以解释通常观察到的石笋δ13C变化.植被变化的效应可以叠加在洞穴水文变化的效应上.洞穴系统的水文变化复杂性可能是造成石笋δ13C变化呈现较复杂特征的主要原因.  相似文献   

Paleoceanographic records in the Chukchi Basin, western Arctic Ocean during the late Quaternary   总被引：1，自引：0，他引：1  

WANG Rujian  XIAO Wenshen  SHAO Lei  CHEN Jianfang  GAO Aiguo 《海洋学报(英文版)》2012,31(1):83-94

The late Quaternary paleoceanographic changes in the western Arctic Ocean are revealed by quantitative studies of foraminiferal abundance, ice-rafted detritus (IRD) and its mineralogical and petrological compositions, planktonic Neogloboquadrina pachyderma (sin.) (Nps)-δ¹⁸O and -δ¹³C, biogenic and non-biogenic components in Core M03 token from the Chukchi Basin during the Second Chinese National Arctic Expedition cruise. Seven IRD events appeared at MIS 7, 5, 3 and 1. These IRD were carried in massive icebergs, which were exported to the Beaufort Sea through the M'Clure Strait Ice Stream, Canadian Arctic Archipelago, and then transported into the Chukchi Basin by the Beaufort Gyre. Low IRD deposition occurred during the glacial times when more extended ice cover and weakened Beaufort Gyre, while the open water condition and the intensified Beaufort Gyre during interglacial periods favored the IRD deposition. Therefore, the IRD events not only indicate the provenance of coarser detritus and ice export events, but also reflect the evolutionary histories of the Beaufort Gyre and North American ice sheet. Seven light Nps-δ¹⁸O and -δ¹³C excursions could respond to enhanced rates of sea ice formation resulting in the production and sinking of isotopically light brines, but was irrelevant to the warm Atlantic water and freshwater inputs. Whereas, the heavy Nps-δ¹⁸O and -δ¹³C values separately reflect the lessened Arctic freshwater and Pacific water, and well-ventilated surface water from the continental shelf and halocline water. Variations of CaCO₃ content and planktonic foraminiferal abundance during the interglacial and glacial periods can demonstrate the incremental or diminishing input of the Atlantic water, while the total organic carbon (TOC) and opal contents increased and decreased during the glacial and interglacial periods, respectively, which could be related to the TOC degradation, opal dissolution and redox conditions of interface between the bottom water and sediments.  相似文献   

The domain of γ Doradus variables in the Hertzsprung–Russell diagram     

G. Handler 《Monthly notices of the Royal Astronomical Society》1999,309(2):L19-L23

70 new γ Doradus candidates were identified from Hipparcos photometry, which represents more than a doubling of the presently known number. Selecting the objects with good evidence for multiperiodicity, it is found that these stars, together with bona fide members of the class, occupy a well-defined region in a colour–magnitude diagram. This domain corresponds to a range of 7200–7700 K on the zero-age main sequence (ZAMS) and 6900–7500 K one magnitude above it, which partly overlaps with the instability strip of δ Scuti stars.
For the first time, γ Doradus stars can be discussed as a group. They can be found over a significant fraction of the main sequence lifetimes for objects in the relevant temperature range. An upper limit on the surface metallicity of γ Doradus stars is apparent, which may guide the search for their pulsation driving mechanism. The importance of possible objects exhibiting both γ Doradus and δ Scuti-type pulsations is discussed.  相似文献   

湖北神农架石笋年纹层与氧碳同位素关系   总被引：2，自引：1，他引：1  

梁燕  孔兴功  汪永进 《中国岩溶》2008,27(4):371-376

基于湖北神农架青天洞石笋U 系测年和年纹层统计结果,分别建立了末次盛冰期( 17 474± 174～ 16 105± 151 aB. P. )和全新世大暖期( 6 935. 4± 33. 8～6 137± 48 aB. P. )长达1 000余年的两个石笋年纹层生长序列。全新世大暖期年纹层平均厚度( 265μm) 约为末次盛冰期( 102μm)的2. 5倍,说明在间冰期东亚季风增强时石笋沉积速率较大,冰期时则相反。两支分辨率为4～ 8年的石笋年纹层厚度与δ13 C变化曲线对比显示: 在百年尺度上,石笋年纹层厚度与δ13 C变化曲线均呈良好的相关性(相关系数分别为- 0. 53和- 0.60) ,说明两指标可能受洞穴上覆土壤带CO2 产率这一主控因素的影响。当上覆土壤层生物活动增强, CO2 分压较高时,导致石笋δ13 C值偏负、生长速率增大。然而,在相同尺度上,两支石笋δ18O变化与对应的δ13 C及年纹层厚度之间的相关性较弱,反映研究地点上覆土壤层CO2产率对东亚夏季风强弱变化响应关系比较复杂。   相似文献   

洞穴水系氢氧同位素监测对重建古气候样品选择的指示意义   总被引：3，自引：2，他引：1  

刘子琦  李红春  熊康宁  袁道先  盈斌  徐晓梅  李俊云 《中国岩溶》2008,27(2):139-144

在贵州省中西部地区采集了地表水、织金洞和石将军洞不同年份和季节的洞穴水样进行氢氧同位素分析。结果显示该地区地表水的δDV- SMOW 和δ18OV- SMOW平均值分别为- 56. 15± 2. 46‰和- 7. 96± 0. 33‰ ,而织金洞1月、4月、9月的水样δDV- SMOW和δ18OV- SMOW平均值分别是- 53. 25‰和- 7. 96‰ , - 59.25‰和- 8. 24‰ , - 56. 89‰和- 8. 21‰ ,无论是旱季还是雨季织金洞大部分洞穴滴水的δD和δ18O值都比较接近地表降水的同位素年平均值,这说明大气降水在不同季节进入洞穴时已经受到充分混合,它们代表的是年均大气降水同位素加权平均值;而另一些滴水点(如寿星宫) ,由于其地表汇水面积小,洞厅顶部的包气带很薄,降雨能很快渗入而使其滴水能敏感地反映出季节性降雨的同位素组成。由此认为,在重建古气候时对石笋的选用切忌盲目,选择前必须进行仔细的洞穴水系稳定同位素组成调查。   相似文献   

黑河流域中上游地区降水δ18O变化特征   总被引：1，自引：0，他引：1  

张应华  仵彦卿 《冰川冻土》2007,29(3):440-445

水资源短缺和合理利用是黑河流域面临的一个严峻问题,解决问题的关键就是要深入了解水循环过程.降水作为水循环中一个重要环节,分析其环境同位素变化特征是应用同位素示踪技术研究水循环过程所必须的前提.根据黑河流域中上游地区取得的降水水样和降水气象资料,分析了该区域降水中δ¹⁸O的变化特征.结果表明:降水δ¹⁸O受降水量、季节、高度和温度等众多因素综合影响,其中温度占主导地位;由于位于干旱内陆地区,降水中δ¹⁸O的季节变化幅度较大,可达20‰以上;降水δ¹⁸O与降水前后平均气温的相关性显著,分别高于δ¹⁸O与降水前气温或降水后气温的相关性.从空间上来看,山区或上游地区降水δ¹⁸O与气温之间的相关性显著,分别高于δ¹⁸O与山前或山前盆地的相关性.  相似文献   

羊卓雍湖流域湖水稳定同位素循环过程研究   总被引：9，自引：0，他引：9  

巩同梁  田立德  刘东年  姚檀栋  尹常亮  余武生  刘忠方 《冰川冻土》2007,29(6):914-920

基于卓雍错流域2004年降水、河水、湖水中δ¹⁸O的监测结果,结合内陆湖水循环稳定同位素蒸发分馏模型,探讨了青藏高原南部羊卓雍湖水中稳定同位素的变化过程.研究表明:羊卓雍现代湖水中-5.9‰的δ¹⁸O平均值,相对应于当地相对湿度介于54%~58%的气候条件下,这是湖水蒸发分馏作用的最后结果.此外,入湖河水中δ¹⁸O变化也对湖水中平衡δ¹⁸O有一定的影响,而湖水温度的直接影响可以乎略.湖水中δ¹⁸O对入湖水δ¹⁸O的波动的调节能力很强,对于入湖水中δ¹⁸O大的波动,只有不到50 a的时间,湖水中稳定同位素会重新达到平衡.  相似文献   

硝酸盐氮氧同位素在不同生态系统中的研究进展   总被引：1，自引：0，他引：1  

张金  马金珠  陈春武  潘昆  包磊 《干旱区地理》2015,38(2):312-319

硝酸盐作为氮循环中的重要物质之一,已成为地下水污染的主要形式。硝酸盐的来源分为自然源和人为源。不同来源的硝酸盐具有不同的同位素特征,因此可以利用N、O同位素来识别硝酸盐的来源、迁移和转化。本文通过综述硝酸盐的主要来源及其同位素特征,简要介绍了硝酸盐同位素检测技术的发展历程,影响同位素分馏的相关作用过程;同时简述了硝酸盐同位素在农业、沙漠、森林、城市生态系统中开展的相关研究,概述了研究中存在的问题,并展望了今后的发展方向。  相似文献   

用稳定氮同位素分析广东硇洲岛海域金线鱼营养级   总被引：1，自引：0，他引：1  

陈春亮  古汉基  杨国欢 《广东海洋大学学报》2013,(4)

应用稳定同位素方法测定广东硇洲岛海域的金线鱼(Nemipterus virgatus)鱼肉、鱼鳃、内脏团和鱼鳞的稳定氮同位素,并计算出营养级。结果表明,在规格较一致的情况下,金线鱼各部位δ15N值范围为10.09‰¹4.07‰,其中,鱼肉δ15N值范围为11.56‰14.07‰,其中,鱼肉δ15N值范围为11.56‰¹4.07‰,差值达2.51‰,平均为12.84‰;鱼鳃δ15N值范围10.41‰14.07‰,差值达2.51‰,平均为12.84‰;鱼鳃δ15N值范围10.41‰¹2.10‰,差值达1.69‰,平均为11.41‰;内脏团δ15N值范围10.09‰12.10‰,差值达1.69‰,平均为11.41‰;内脏团δ15N值范围10.09‰¹1.98‰,差值达1.89‰,平均为11.08‰;鱼鳞δ15N值范围10.10‰11.98‰,差值达1.89‰,平均为11.08‰;鱼鳞δ15N值范围10.10‰¹1.35‰,差值达1.25‰,平均为10.66‰。鱼肉、鱼鳃、内脏团、鱼鳞的δ15N值大小依次为:鱼肉、鱼鳃、内脏团、鱼鳞。由δ15N值推算出来金线鱼的营养级范围为2.4611.35‰,差值达1.25‰,平均为10.66‰。鱼肉、鱼鳃、内脏团、鱼鳞的δ15N值大小依次为:鱼肉、鱼鳃、内脏团、鱼鳞。由δ15N值推算出来金线鱼的营养级范围为2.46³.12,平均值为2.80,符合其主要摄食浮游和底栖动物的食性。  相似文献   

How do non-halophyte locust trees thrive in temperate coastal regions: A study of salinity and multiple environmental factors on water uptake patterns     

Han Li  Zhiqing Lan  Han Chen  Jinhui Jeanne Huang 《水文研究》2024,38(3):e15122

Understanding plant water use patterns is crucial for comprehending the dynamics of the soil–plant-atmosphere continuum and evaluating the adaptability of plants across diverse ecosystems. However, there remains a gap in our comprehension of non-halophyte plants' water uptake patterns and driving factors in temperate coastal regions. For this reason, we used locust trees (a widely planted non-halophyte tree species in northern China) as a study subject. We collected water isotope data (δ²H and δ¹⁸O) for locust trees xylem and soil over two consecutive growing seasons. The MixSIAR model was used along with five distinct sets of input data (single isotopes, uncorrected dual isotopes, and corrected dual isotopes incorporating δ²H data obtained by soil water line or cryogenic vacuum distillation methods) to infer water utilization patterns. The results indicated that locust trees primarily absorb shallow soil water (0–20 cm, 29.4% ± 16.9%) and deep soil water (120–180 cm, 24.7% ± 5.8%). Pearson's correlation analysis revealed the key driving factors behind water uptake patterns were vegetation transpiration and soil salinity. Remarkably, the build up of salts in the lower soil layer (60–120 cm) hinders the absorption of water by plants. To prevent high salt concentrations from affecting water uptake in non-halophyte plants, we recommend implementing sufficient irrigation from March to April each year to meet the water needs of plant growth and regulate the accumulation of salts in various soil layers. This study reveals the dynamic water utilization strategy of non-halophyte plants in temperate coastal regions, offering valuable information for water resources management.  相似文献