青藏高原中部各拉丹冬峰雪冰记录特征

2005年10~11月在青藏高原唐古拉山脉各拉丹冬峰冰川区不同海拔采集了3个雪坑样品,分析结果表明,雪坑中δ¹⁸O和主要离子浓度具有明显的季节变化特征.夏季风期间降水中δ¹⁸O低于其它季节,表明该地区夏季δ¹⁸O的"降水量效应"仍然存在.雪坑中主要离子在非季风期的浓度高于夏季风期.主要离子的相关分析表明,除NH₄⁺、NO₃^-外,雪坑中其它离子浓度之间均存在较好的正相关性.各拉丹冬峰冰川区仍受到南亚季风的影响,但因其位于夏季风影响的边缘区域,其影响程度相对于高原南部较弱;同时也受到大陆性气候的影响,在冬春季节具有较高的粉尘气溶胶沉降.     

高精度稳定锶同位素分析方法综述

近年来稳定Sr同位素在同位素地球化学领域越来越受到重视,在表生地球化学、古环境、考古学、地球内生作用及陨石等方面研究都取得了重要成果,这得益于高精度稳定Sr同位素分析方法的发展。文章总结了δ88/86Sr分析方法的关键技术要素。在化学提纯方面,文献中广泛使用Sr特效树脂,用离子交换法实现Sr元素的分离提纯,但Sr特效树脂价格昂贵,且具有难以消除的记忆效应,建议用阳离子树脂代替;在质谱分析方面,主要使用多接收电感耦合等离子体质谱（MCICP-MS）和热电离质谱（TIMS）进行测量,MC-ICP-MS测量具有比TIMS更高的测量效率,但是测量精度略低;对于质量歧视校正,目前使用较为广泛的方法有标样—样品间插法、Zr元素外部校正法以及双稀释剂法,其中双稀释剂法具有较高的测量精度,但在MC-ICP-MS上应用的相关研究较少。目前还缺乏对国际标准样品的δ88/86Sr的详细对比。因此,优化分析流程、提高测量精度以及更多标准样品δ88/86Sr的测定是需要加强的工作。     

南极普里兹湾海域夏季表层水体颗粒有机碳及其同位素分布特征

基于中国第29次南极科学考察在普里兹湾海域采集的61个站位的表层悬浮体样品的颗粒有机碳(POC)及其稳定同位素(δ13CPOC)测试结果,结合卫星遥感解译的研究区海水表面温度(SST)、叶绿素a(Chl a)浓度和海冰覆盖率数据,研究了普里兹湾海域表层水体悬浮POC的分布特征,探讨了悬浮体中POC的来源及其形成过程。结果表明,2013年夏季普里兹湾表层悬浮POC浓度为0.28—0.84 mg·L-1,平均浓度为0.48 mg·L-1;δ13CPOC值的变化范围为-29.68‰—-26.30‰,平均值为-28.01‰。表层水体悬浮POC分布呈现近岸高于远岸,西部高于东部的特征。POC的高值区主要分布在冰架附近,与表层水体Chl a浓度和海冰覆盖率分布趋势基本一致,表明夏季普里兹湾表层水体悬浮POC主要由浮游植物现场生产,而浮游植物的生长受到了海冰的显著影响。在普里兹湾外部海域表层水体悬浮颗粒物δ13CPOC值从东向西逐渐偏负,而调查区东部从近岸向远海逐渐偏负,反映该海域δ13CPOC分布特征主要受到浮游植物吸收与固定CO2速率的影响。中山站附近海域δ13CPOC值显著偏负,可能是受到近岸海域陆源有机质输入和浮游生物种属改变的影响。     

长江流域大气降水中δ^18O变化与水汽来源

根据GNIP所提供的长江流域多年月平均降水中δD、δ^18O料以及NOAA-CIRES提供的NCEP/NCAR再分析资料,研究了长江流域降水稳定同位素与降水量、水汽压、温度和水汽来源之间的关系。结果表明：在平均季节尺度下,长江流域大气降水中δ^18O降水量、水汽压和温度均存在显著的负相关关系,说明该流域降水中δ^18O...     

A prolonged warm and humid interval during marine isotope stage 13–15 as revealed by hydrographic reconstructions from the South China Sea (IMAGES MD972142)

Variations of orbital-driven insolation, ice volume, and greenhouse gas effects have been proposed as major controlling factors in determining the timing and amplitude of Quaternary cyclic climate changes. However, it remains to be determined how the internal feedback in the tropical atmosphere and ocean and the coupling between the low- and high-latitude systems may have produced instability or non-cyclic changes in the long-term climate evolution. Such “abnormalities” have been reported increasingly from paleoclimatic reconstructions in East Asia and the western Pacific for a prolonged warm and humid climate interval during marine isotope stage (MIS) 13–15, ～475–610 kya. To better address the climate abnormality in MIS 13–15 that has been observed in the western Pacific, here we report high-resolution late Quaternary planktic foraminifer faunal abundance and faunal sea surface temperature (SST) records from the International Marine Past Global Change (IMAGES) program core MD972142, which was retrieved from the southeastern South China Sea (SCS). Our results indicate that the faunal assemblages and SSTs in the southeastern SCS express a substantially prolonged, unusual warm interglacial-type climate condition in MIS 13–15. The climate was abnormally warm during the cold MIS 14. Our study also suggests a lowering of sea surface salinity (SSS) during MIS 13–15. While the western Pacific climate experienced a persistently warm and humid period at MIS 14, a “normal” cooling (～2 °C) condition on the surface of the eastern equatorial Pacific existed concomitantly. While assessing possible interpretations of this “abnormal” climate interval in MIS 13–15, our study indicates that an enhanced interhemispheric and/or longitudinal temperature gradient across the basin-wide Pacific cannot be ruled out. A change in the sensitivity of the East Asian Monsoon (EAM) that controlled temperature and precipitation patterns in East Asia and the western Pacific is probably also important or responsible for this climate abnormality. Based on our evidence, we suggest that the tropical dynamics would have played a role in the climate abnormality in MIS 13–15, through maintaining or even increasing the longitudinal SST gradient in the equatorial Pacific, which may have intensified the low-latitude trade winds in the eastern component of the Walker Circulation that drove a longer duration and/or stronger intensity of the summer vs. winter EAM.     

O-羧甲基壳聚糖的制备及其结构表征

本文以壳聚糖为原料,采用苯甲醛选择性的保护壳聚糖C2位氨基的方法,制备了O-羧甲基壳聚糖(O-CMC)。采用红外光谱及核磁共振波谱法对产物结构进行了表征,确定了羧甲基化反应只发生在壳聚糖的O位。该方法制备得到的O-CMC的羧甲基度为42.2%,反应选择性好,步骤简单,产率高达85%。     

神农架石笋记录的近200年东亚季风变化及其ENSO响应

通过湖北省神农架永兴洞石笋(编号:YX92)230Th年龄和纹层计数年代学研究,建立了1788AD-1956AD时段年际分辨率石笋氧同位素序列。该序列δ18O值变化范围为-9.70‰~-7.87‰,最大振幅约达1.83‰,呈现显著的年代际尺度振荡旋回特征。功率谱分析结果揭示存在显著的60~70年准周期信号。该记录与同区域和尚洞石笋δ18O曲线具有很好的重现性,说明其可能受控于共同的气候因子,指示了东亚夏季风大尺度环流特征。将石笋重建的东亚夏季风指标与全印度夏季降水量指示的印度夏季风指数对比,结果显示两者在年代际旋回特征上具有很好的相似性,但是呈反相位关系。进一步与ENSO指数对比,发现东亚夏季风年代际尺度变化与ENSO存在密切联系,表现为东亚夏季风增强,对应于ENSO暖期,反之亦然。因此,东亚季风与印度季风在年代际尺度上的反相位关系可能源于两者对ENSO机制的不同响应。     

Stable carbon‐isotope record of shallow‐marine evaporative epicratonic basin carbonates,Ordovician Williston Basin,North America

Secular variations in stable carbon‐isotope values of marine carbonates are used widely to correlate successions that lack high‐resolution index fossils. Various environmental processes, however, commonly may affect and alter the primary marine carbon‐isotope signal in shallow epicratonic basins. This study focuses on the marine carbon‐isotope record from the carbonate–evaporite succession of the upper Katian (Upper Ordovician) Red River Formation of the shallow epicratonic Williston Basin, USA. It documents the carbon‐isotope signal between the two major Ordovician positive shifts in δ¹³C, the early Katian Guttenberg and the Hirnantian excursions. Eight δ¹³C stages are identified based on positive excursions, shifts from positive to negative values and relatively uniform δ¹³C_carb values. A correlation between carbon‐isotope trends and the relative sea‐level changes based on gross facies stacking patterns shows no clear relation. Based on the available biostratigraphy and δ¹³C trends, the studied Williston Basin curves are tied to the isotope curves from the North American Midcontinent, Québec (Anticosti Island) and Estonia, which confirm the Late Katian age (Aphelognathus divergens Conodont Zone) of the upper Red River Formation. The differences in the δ¹³C overall trend and absolute values, coupled with the petrographic and cathodoluminescence evidence, suggest that the carbon‐isotope record has been affected by the syndepositional environmental processes in the shallow and periodically isolated Williston Basin, and stabilized by later burial diagenesis under reducing conditions and the presence of isotopically more negative fluids.     

重庆金佛山羊口洞滴水δD和δ18O变化特征及其环境意义

为探究重庆金佛山羊口洞滴水δD、δ18O化特征及其环境意义,于2011年10月—2013年8月,在重庆市南川区金佛山逐月采集大气降水样品及羊口洞6个滴水监测点的滴水样品进行氢氧稳定同位素测定。通过比较降水和滴水δD、δ18O的分布特征、季节变化及其与降水量和温度的相关性发现：（1）6个滴水点δD、δ18O较均匀地分布在当地降水线附近,表明从降水到形成滴水的过程受蒸发作用影响不大,滴水δD、δ18O现了当地大气降水δD、δ18O均水平。（2）受洞穴上覆岩土层的调蓄作用影响,羊口洞各滴水点δD和δ18O变化范围（—46.77~—62.09‰,—7.05~—9.96‰）远小于洞外大气降水（5.17~—115.63‰和—1.44~—16.10‰）,且较降水存在明显滞后性。但滴水δD、δ18O体上也表现出与降水相同的夏季偏轻、冬季偏重的趋势,主要受降水水汽源地季节性差异影响。而各个监测点滴水δD和δ18O节变化差异较大,可能受滴水点上覆岩层裂隙管道发育、覆盖层厚度、岩溶水滞留时间、形成滴水前的运移路径、滴水点的高度和滴率、滴水点距离洞穴出入口的距离等多种原因影响。（3）降水δ18O现出＂降水量效应＂和＂负温度效应＂,羊口洞滴水δ18O降水量总体上也呈负相关关系,而与温度（水温、洞温）的关系则呈现多样化：1#、2#、5#、6#监测点滴水δ18O温度不相关,3#点为正相关,4#点为负相关,这与各监测点滴水δ18O节变化差异较大有关。（4）总体而言,羊口洞滴水δD和δ18O季节变化不够明显,利用羊口洞石笋进行季节分辨率的古气候重建可能性较低,但滴水δD和δ18O承了当地大气降水信息,其石笋δ18O用于重建年际~十年际及更长时间尺度的古气候变化。     

塔里木盆地西南缘表土碳同位素组成特征分析

土壤碳同位素可以反映生长植被的同位素组成,从而进一步反映当时的植被类型以及气候环境状况。已有的研究显示,不同地区碳同位素与气候因子的关系存在显著差异,因此在不同区域开展土壤碳同位素与气候因子之间相关性关系分析对古气候的重建至关重要。通过采集塔里木盆地西缘帕米尔地区和盆地南缘和田地区策勒县的表土沉积物,分析测定后获得其有机碳同位素,并将该表土有机碳同位素数据与气候因子进行相关性分析,以探明研究区有机碳同位素组成特征及其潜在的气候意义。结果表明：帕米尔地区和策勒地区的表土碳同位素变化对气候因子的响应存在明显差异。气温方面,帕米尔地区与气温呈正相关,其中与冷季气温相关性最好（r=0.598,P<0.01）;策勒地区与气温呈负相关,其中与暖季气温相关性最好（r=-0.684,P<0.01）。降水方面,帕米尔地区与降水量的相关性不显著;策勒地区与年均降水量呈弱负相关,与暖季降水量呈弱正相关,与冷季降水量呈显著的负相关关系（r=-0.632,P<0.01）。上述分析表明基于沉积物有机碳同位素来重建古气候时应充分考虑区域差异的影响。