中国西北干旱区不同粒径表土碳酸盐含量及碳、氧同位素组成

通过对我国典型干旱区表土分粒级样品的碳酸盐含量及其碳氧同位素的测试,结果显示:我国西北干旱区表土不同粒级样品的碳酸盐含量以及碳氧稳定同位素组成存在较大的差异。随着粒径的减小,碳酸盐含量逐渐升高,氧同位素逐渐偏正,碳同位素逐渐偏负。可以认为细颗粒组分中土壤次生碳酸盐相对比例大,而粗颗粒组分中原生碳酸盐相对占优势。而次生碳酸盐氧同位素可能受蒸发的控制,碳同位素更多的受植被的影响,所以表现出细颗粒组分较粗颗粒组分碳酸盐的氧同位素更偏正,而碳同位素更偏负。因此,干旱区表土细颗粒组分碳酸盐能更好地反映成壤过程中次生碳酸盐形成时期的气候环境信息。     

中国北方沙尘源区铅同位素分布特征及其示踪意义的初步研究

对中国北方沙尘源区风成沙Pb同位素的分布特征以及示踪意义进行了初步研究。结果表明,中国北方沙尘源区风成沙Pb同位素的空间分布具有明显的区域差异,毛乌素沙地具有最低的206Pb/204Pb、207Pb/204Pb和208Pb/204Pb值,塔克拉玛干沙漠具有最大的206Pb/204Pb、207Pb/204Pb和208Pb/204Pb值,其他地区介于两者之间。通过对比研究,Pb同位素在中国北方黄土、格陵兰冰芯粉尘和北太平洋深海沉积物源区示踪方面具有较好的有效性。     

A Coupled Calibration and Modelling Approach to the Understanding of Dry-Land Lake Oxygen Isotope Records

Comparisons between climate proxies and instrumental records through the last two centuries are often used to understand better the controls on palaeoarchives and to find relationships that can be used to quantify changes in pre-instrumental climate. Here we compare an 80-year-long annually resolved oxygen isotope record from Nar Gölü, Turkey, a varved lake sequence, with instrumental records of temperature, precipitation, wind speed, relative humidity and calculated values of evaporation, all of which are known to be possible controls on lake oxygen isotope systems. Significant relationships are found between the isotope record and summer temperatures and evaporation suggesting these are dominant controls on the isotope hydrology of this non-outlet lake. Modelling the stable isotope hydrology of the lake system allows these relationships to be tested independently. We show that the isotope record follows the same trends in the temperature and evaporation records but that, even when combined, these two climatic factors cannot fully explain the magnitude of change observed in the isotope record. The models show the lake system is much less sensitive to changes in evaporation and temperature than the climate calibration suggests. Additional factors, including changes in the amount of precipitation, are required to amplify the isotope change. It is concluded that proxy-climate calibrations may incorrectly estimate the amplitude of past changes in individual climate parameters, unless validated independently.     

稳定同位素在湿地水文研究中的应用现状与前景

湿地水文过程对湿地形成、发育和演化起到了至关重要的作用,也是湿地保护和修复的关键。稳定同位素技术是湿地水文研究的有效工具,探讨了稳定同位素技术在湿地水资源性质与来源识别以及湿地水文循环研究等方面的应用,指出了当前应用中存在的问题,如缺乏湿地水文过程的系统性机理研究等,展望了稳定同位素在湿地水文中取样方法上的创新改进与人类干扰对湿地水文过程影响研究的应用前景。     

稳定氯同位素及其应用地球化学研究

稳定氯同位素的分馏作用有限,同位素比值变化小,测定精度要求高。在很长一段时期内,人们一直未能发现自然界稳定氯同位素组成的变化。随着测定技术的不断发展,氯同位素的分馏效应逐渐得到证实,并引起了人们的广泛关注。国内外学者已将氯同位素应用于海水、地表河流水、地下水、盐湖、古代蒸发岩(盐)和热液矿床等方面的地球化学研究中,对水体演化和矿床成因进行了较为深入的探讨和分析,并取得了一定的研究进展。这些研究工作充分表明氯同位素在水体演化和成矿理论研究以及矿产勘查等方面有着独特优势,尤其在我国开展蒸发岩(盐)氯同位素地球化学研究具有很大的发展潜力和广阔的应用前景。但氯同位素的应用地球化学研究目前尚处于发展时期,更深入的研究还有待于测定方法的进一步完善以及对不同地球化学体系氯同位素的系统测定和研究。     

石盐溶解过程中氯同位素分馏的初步研究

采用氯同位素组成测定的正热电离质谱法,研究了模拟石盐快速和慢速溶解过程及达到溶解-结晶平衡状态后氯同位素分馏现象。用Na2SO4饱和溶液模拟水溶剂中快速溶解过程,用99.5%乙醇模拟非水溶剂慢速溶解过程。在水溶剂和非水溶剂中,氯离子含量呈相反的变化趋势。快速溶解过程中,氯同位素分馏系数的变化范围为0.999 25～1.001 09,平均值为1.000 29,基本与自然界盐湖卤水石盐结晶体系的趋势相似;慢速溶解过程中氯同位素分馏系数的变化范围为0.999 34～1.001 07,平均值为0.999 51,此过程中开始能反映出NaC l慢速结晶过程的氯同位素分馏,处于溶解与再结晶共存时,氯同位素处于0分馏状态。NaC l的溶解基本能反映出自然界中盐湖卤水快速结晶和慢速结晶中的氯同位素分馏。     

稳定氯同位素在地球科学研究中的进展

本世纪初到八十年代中期由于氯同位素的测试精度很低（＞１．０‰）导致氯同位素地球科学研究未获得任何进展。１９８４年Ｋａｕｆｍａｎｎ等人建立测试精度高达±０．２４‰的方法，并且首次发现了氯同位素在自然界的变异。在此以后氯同位素的测试精度不断提高，各国学者相继对海水、温泉、火山湖水、油田卤水、地下水盐湖、冰雪、环太平洋的斑岩铜矿和美国密西西比型铅锌矿床造岩矿物和造矿矿物流质包裹体中氯同位素进行了测定并对其中氯同位素的分布规律做了比较深入的研究。在此基础上对各类水体及矿床的成因与物质来源进行了有益的探索，另外还以自然界氯同位素产生分馏的原因及机理做了初步的研究。     

Efficiency of different mesh sizes for isolating fossil chironomids for stable isotope and radiocarbon analyses

We examined the effects of sieving with different mesh sizes on the efficiency of processing fossil chironomids from lake sediments for isotope analyses. Results obtained for three different sediments indicate that each of the studied sieve fractions (100–150, 150–200, 200–250, 250–300, >300 μm) contain a similar proportion of the overall mass of chironomid fossils in a sample. However, the sorting time needed to separate chironomids from other sieve residue is disproportionately large for smaller mesh sizes. Employing sieves with a 200-μm rather than the 100-μm mesh commonly used for standard palaeoecological analyses of fossil chironomids decreased processing time for a given mass of fossils by 30–58% in our study. For optimizing the efficiency of chironomid sample processing for stable isotope and radiocarbon analysis we therefore recommend a 200-μm mesh size sieve, although the sorting of all >100-μm fractions may be necessary in sediments with low chironomid abundances. Excluding certain small taxa from isotope analysis, may structurally bias isotope values of samples. Therefore, further studies on taxon-specific isotope analysis are required to quantify these effects.     

长江口外海域沉积物中有机物的来源及分布

通过分析长江口外海域不同区域有机碳和氮的分布特征及其影响因素,了解了底部沉 积物中有机碳和氮同位素的生物地球化学特征,探讨二者对长江口外海域底部沉积物中有机 物来源的指示意义。运用质量混合模型,计算了长江输入的陆源有机物的贡献及其空间变化。结果表明,长江口外海域沉积物中TOC 和TN 的分布和东海陆架的环流体系有着密切关系, 与环流的分布相对应,如果大致沿31^oN 和123^oE 作为分界线, 整个研究区的TOC 和TN 的分布可划分为4 个具有不同分布特征的区域。TOC、TN、δ¹³C 和δ¹⁵N 分别与沉积物的平均粒 径呈线性相关关系,因此,粒度效应是控制长江口外海域沉积物中有机物分布和稳定同位素 碳、氮的一个重要因素。研究区内的C/N 比值能够在一定程度上体现有机物的来源信息,但δ¹⁵N 表现出了与C/N 和δ¹³C 不同的区域分布和变化特征。陆源有机物来源比重较高的区域与 长江口外海域赤潮突发频率最高的地区相对应。长江口附近沉积物中的陆源有机物来源最高, 超过了50%,且等值线呈舌状向东北方向凸出,表明了长江冲淡水的影响。陆源颗粒态有机物沉海底后,要不断经历早期成岩作用和生物作用,因此在在相同地点,陆源有机物对沉积物中有机物的贡献,要明显小于对悬浮颗粒态有机物的贡献。     

Important progress on the use of isotope techniques and methods in catchment hydrology

The use of isotope techniques and methods in catchment hydrology in the last 50 years has generated two major types of progress: (1) Assessment of the temporal variations of the major stocks and flows of water in catchments, from which the estimation of wa-ter residence times is introduced in this paper. (2) Assessment of catchment hydrologic processes, in which the interactions be-tween different waters, hydrographical separation, and bio-geochemical process are described by using isotopes tracers. Future progress on isotope techniques and methods in hydrology is toward the understanding of the hydrological process in large river basins. Much potential also waits realization in terms of how isotope information may be used to calibrate and test distributed rainfall-runoff models and regarding aid in the quantification of sustainable water resources management.     

Carbon and nitrogen isotopic composition of different strains ofArtemia sp

Stable carbon and nitrogen isotope ratios have been determined on 41 strains ofArtemia sp. from different geographic regions around the world. The δ¹³C and δ¹⁵N values ranged between −13.7 to−25.0 per mil and −0.7 to 21.2 per mil respectively.Artemia δ¹³C values from coastal environments are consistent with a marine origin for the food sourceArtemia from inland salt lakes have a range of carbon isotope values suggesting C₃, C₄ and CAM based organic matter could form the base of theArtemia food chain. These data indicate thatArtemia having a wide range of carbon and nitrogen isotope values are available for tropho-dynamic research studies that quantify the effect of respired CO₂ on tissue and CaCO₃ shell¹³C/¹²C ratios. Such stable isotope variation also suggests that stable isotope fingerprinting remains a viable technique for identifying specificArtemia collection sites.     

基于氢氧同位素和水化学的祁连山老虎沟冰川区径流过程分析

基于2012-2013年两个消融期在祁连山老虎沟冰川区连续2 a采集的冰川融水径流、雪冰以及降水样品,分析探讨了冰川区水体介质中氢氧同位素和水化学要素(主要化学离子、pH值、TDS和电导率等)在消融期的变化过程及特征。结果表明:祁连山老虎沟雪冰融水中的氢氧同位素值(δD和δ¹⁸O)表现出明显的消融期随月份波动,先升高再降低的趋势,在7月份表现出高值,反映了冰川消融强弱程度的变化过程。冰川径流中同位素含量与冰雪融水接近,且处于当地降水线上,其主要来自冰雪融水和降雨补给。老虎沟冰川融水径流水化学主要表现为Ca-Na-HCO₃-SO₄和Ca-Mg-HCO₃-SO₄型,其组成特征也表现出随消融过程而变化。对氢氧同位素和化学要素组成在消融期(6~9月)随时间的变化过程进行了分析,表明结合冰川区氢氧同位素和化学要素(包括化学离子、TDS、pH值和电导率等)的组成可以区分雪坑和新雪、河水的组分变化,可以反映冰川融水径流在消融期的变化过程。     

树轮稳定氮同位素记录的进展与展望

树轮稳定同位素比率是研究气候变化与环境演变的有效代用资料,耦合分析树轮稳定同位素记录的信息可揭示森林生态系统碳—水—氮时空变化特征及相互作用,反映环境变化对植物特定化合物的生理影响。树轮稳定氮同位素比率（δ¹⁵N）与树木生长的环境条件密切相关,其变化可以反映长时间尺度森林生态系统氮循环的动态特征,弥补监测资料的不足。本文综述了树轮稳定氮同位素的分馏机理与测定方法,解析了树轮δ¹⁵N在样品预处理和测试中需要关注的问题,系统梳理与归纳了基于树轮δ¹⁵N进行气候变化、环境演变和人类活动氮排放研究的进展。指明中国树轮稳定氮同位素研究潜力及其在未来亟需着重发展的方向,旨在推动森林生态系统氮循环时空特征深入研究。     

基于温度作为辅助变量的中国降水δ^18O空间分布特征

本研究利用从WorldClim获得的高分辨率气象数据分析稳定同位素温度效应,研究发现最热季度的平均气温与中国62个站点同位素年平均值之间表现出很好的相关性（R2=0．79）。在此基础上利用地统计学方法,也就是采用温度作为辅助变量的空间插值算法——局部平均的简单克里金法（Simple Kriging with locally varying mean,SKlm）,对中国降水中稳定同位素年平均值空间分布进行了模拟,得到了较高分辨率的中国降水中年均δ^18O空间分布图,该图能够较好地表现区域同位素变化模式,能够反映如降水汽团的来源、性质等的气候环境背景,也能在一定程度上反映包括当地的纬度、地形、海拔高度等在内的局部地理因素。     

Taphonomic and early diagenetic effects on the C and N stable isotope composition of cladoceran remains: implications for paleoecological studies

I addressed the effects of taphonomic and early diagenetic processes on the isotope composition of cladoceran remains, using both experimental and field approaches. An experiment was designed to mimic the conditions encountered by cladoceran remains when they settle through the water column and are buried in the sediment. Cladoceran exoskeletons were incubated for 4 months in oxic or anoxic water, and in sediment. Changes in their carbon (C) and nitrogen (N) content and isotope compositions were measured. Most changes in isotope composition of exoskeletons took place when they settled through the water column. Once buried in the sediment, however, the δ¹³C and δ¹⁵N values of cladoceran exoskeletons did not undergo further change. Taphonomic processes resulted in an increase in δ¹³C and δ¹⁵N of the cladoceran remains and this was related to microbial degradation, which selectively removed isotopically light C and N compounds from the remains. For δ¹³C, changes were minimal (<1‰) and occured within the first 3 months. Taphonomic effects on δ¹⁵N were larger, from +2 to +5‰, and occurred within the first 2–3 weeks. These effects depended on incubation conditions and were greater in anoxic waters than under oxic conditions. Monthly changes in the isotope composition of sedimenting cladoceran exoskeletons were also recorded in the field using sediment traps, and were compared to the isotope composition of the living cladoceran community. The isotope composition of sedimenting remains displayed values consistent with those that might be expected, considering the effects of taphonomic processes observed in the experiment. Because C and N in cladoceran exoskeletons might involve a different isotope routing, the δ¹⁵N value of the remains provides an annual record of the value in the parent community, with a 1-month delay, while δ¹³C of remains essentially reflects that of the parent community during the period of lake thermal stratification. These findings provide insights into paleolimnological interpretation of isotopic changes in cladoceran remains from sediment cores.     

锂同位素地球化学研究进展

锂的两个稳定同位素(6Li和7Li)相对质量差较大,因此锂同位素分馏比较显著。由于分析测量技术的改进和完善,锂同位素地球化学近年来有了长足的发展。研究表明,温度是控制锂同位素分馏的一个重要因素。此外,锂在不同矿物中配位结构和化学键强度的差异也会影响共存相之间的锂同位素分馏。由于锂同位素存在较大的分馏和不同地质体中截然不同的δ7Li值,锂同位素地质应用范围十分广泛。目前,锂同位素在地表风化、海底热液和洋壳蚀变、板块俯冲、示踪卤水来源和演化等方面的研究中成效显著,并且开始应用到矿床学中。     

霍景涅里辛沙漠地下水化学和同位素特征

在综合分析地质条件基础上,运用水化学及同位素技术,并结合现场调查及室内分析的方法,对霍景涅里辛沙漠地下水进行研究,分析了研究区地下水化学及稳定同位素特征,讨论了地下水的矿化过程及影响因素,确定了沙漠区地下水的补给来源。结果表明：沙漠区潜水中各离子组分平均值均大于承压水,潜水的溶解性总固体（TDS）平均值远大于承压水,说明潜水的蒸发作用大于承压水;控制潜水中主要离子成分的作用主要为溶解作用、交替吸附作用以及蒸发作用,控制承压水中主要离子成分的作用主要为溶解作用;沙漠区潜水与承压水具有一定的水力联系;地下水的补给来源主要为山区冰雪融水及降水,潜水的补给高程为1 370m,承压水的补给高程为1 650m。     

西部中国沙棘叶片稳定碳同位素组成的空间特征及其气候意义

分析了西部中国沙棘（Hippophate rhamnoides sinensis）叶片稳定碳同位素组成特征及其与环境因子之间的关系。结果表明,中国沙棘叶片δ13C值在-30.40‰~-24.91‰之间变化,平均值约为-27.62‰,属于C3植物。随纬度和经度的升高,中国沙棘叶片δ13C值明显升高,而随海拔的升高而降低,具有明显的空间分布特征。中国沙棘叶片δ13C值与温度没有明显的关系,随蒸发量和日照时间的升高而升高,随降水量的升高有降低趋势,具有明显的气候意义。表明中国沙棘具有较高的水分利用效率,水分是控制中国沙棘δ13C值变化或生长的主导因子。     

A preliminary study on oxygen isotope of ice cores of Collins Ice Cap,King George Island,Antarctica

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Identifying recent sources of organic matter enrichment and eutrophication trends at coastal sites using stable nitrogen and carbon isotope ratios in sediment cores

We studied the potential for using stable carbon and nitrogen isotope ratios in sediment profiles to trace external nutrient sources and eutrophication at four coastal sites in the Baltic Sea. The sites are characterized by various present and past activities in their catchments, including residential development, sugar processing, agriculture and fish farming. Radiometrically dated sediment cores were analysed for nutrient isotope ratios, organic carbon and total nitrogen. Background information was collected from historical sources, literature and water monitoring data. Despite the multiple organic enrichment sources, it was possible to identify individual sources and processes in the sediment profiles using stable isotope analysis of bulk sediment. The largest changes in δ¹⁵N values were seen at sites receiving urban wastewaters. The site that received effluents from a sugar cane (C₄-plant) refinery in the past showed a clear effect on δ¹³C values compared to the site that received wastewater from a sugar beet (C₃-plant) factory. Fish farming produced detectable, albeit minor changes in the sediment profile. Slightly lower δ¹³C values reflected the influence of fish feed and fish metabolism, and higher δ¹⁵N values likely indicated the influence of increased sediment denitrification. The land-sea connection via river discharge was observable in the overall δ¹³C levels of the sediment cores. Our results suggest that temporal changes in sources of organic matter enrichment can be detected in well-dated coastal sediment cores using nutrient stable isotope analyses, even at sites subjected to multiple impacts. There is not, however, a simple relationship between sediment stable isotope profiles and the eutrophication history of our study sites.