应用碳、氮稳定同位素研究鄱阳湖枯水末期水生食物网结构

稳定碳、氮同位素比值分析技术是研究生态系统中物质循环与能量流动的有效技术。δ13C值常用来分析消费者食物来源,δ15N值常用来确定生物在食物网中的营养位置。应用稳定同位素技术分析了鄱阳湖北部湖口县、都昌县、星子县、吴城镇4个采样点95条鱼和其他食物网成分样品的碳、氮稳定同位素比值,构建了鄱阳湖枯水期末期水生食物网。结果表明,不同水域颗粒有机物(POM)的δ13C值不同,范围为-27.5‰～-24.6‰可以区分赣江、修水、鄱阳湖、长江和鄱阳湖湖交汇处水体的颗粒有机物特征。江西鄱阳湖国家级自然保护区受人类活动

Growth and food availability of silver and bighead carps: evidence from stable isotope and gut content analysis

A 2-year investigation of growth and food availability of silver carp and bighead was carried out using stable isotope and gut content analysis in a large pen in Meiliang Bay of Lake Taihu, China. Both silver carp and bighead exhibited significantly higher delta 13C in 2005 than in 2004, which can probably be attributed to two factors: (i) the difference between isotopic compositions at the base of the pelagic food web and (ii) the difference between the compositions of prey items and stable isotopes. The significantly positive correlations between body length, body weight and stable isotope ratios indicated that isotopic changes in silver carp and bighead resulted from the accumulation of biomass concomitant with rapid growth. Because of the drastic decrease in zooplankton in the diet in 2005, silver carp and bighead grew faster in 2004 than in 2005. Bighead carp showed a lower trophic level than silver carp in 2005 as indicated by stable nitrogen isotope ratios, which was possibly explained by the interspecific difference between the prey species and the food quality of silver carp and bighead.

大气CH_4中碳稳定同位素组成的PreCon-GC/C-IRMS系统测定

利用预浓缩装置-气相色谱/燃烧-同位素比值质谱仪(PreCon-GC/C-IRMS)联用系统,建立了就采样、浓缩和在线质谱分析大气CH4中稳定碳同位素组成的测定方法。通过多组试验对比,分析并讨论了利用PreCon-GC/C-IRMS联用技术测定大气CH4中碳稳定同位素比值的试验条件、系统线性、稳定性及准确度和精密度等。结果表明,在本研究方法条件下,当离子流强度在1.0~20 V时,系统线性良好(斜率S=0.04‰/V),在4.0~15 V内其线性(斜率S=0.03‰/V)优于总体线性;系统测量稳定性可靠,&delta;13C值的测定结果的S.D<0.3‰,最大偏差<0.5‰,回收率达99.99%,准确度和精度均符合分析与研究要求。利用该系统对室内和室外草坪地空气中CH4的碳稳定同位素组成做初步测试,其碳同位素的平均值分别为-31.358‰和-33.085‰,且相同地点区域空气中CH4的1&delta;3C值,在1 d内和不同日期间的变化均在0.5‰以内,重现性良好。

东海典型海域溶解无机碳的稳定碳同位素研究

本文采用碳稳定同位素比分析法，进行了29个调查站的溶解无机碳稳定同位素的研究。研究结果表明，海水的混合强度是决定#delta#~13C-DIC分布的重要因素；在表层海水中，海－气界面二氧化碳交换和浮游植物光合作用对#delta#~13C-DIC影响较大；在中、底层海水，特别是底层海水中，有机物的氧化分解作用对#delta#~13C-DIC影响较大。