| 氧化条件对样品有机碳同位素测定的影响因素讨论 |
| 点此下载全文 |
| 引用本文：曹蕴宁,刘卫国,宁有丰,张庆乐,王政.2005.氧化条件对样品有机碳同位素测定的影响因素讨论[J].地球学报,26(z1):55-56. |
| DOI：10.3975/cagsb.2005.s1.20 |
| 摘要点击次数: 3060 |
| 全文下载次数: 2487 |
|
| 基金项目:本文得到国家重点基础研究发展规划项目（编号:2004CB720200)，国家自然科学基金项目（编号:40121303,40373008)，全国优秀博士论文研究基金项目，黄土与第四纪地质国家重点实验室开放基金（编号：SKLLQG0525)等的资助。 |
|
| 中文摘要:有机碳同位素在全球变化、古气候和古环境恢复研究中的应用日益广泛和深人。有机碳同位素分析的基本原理是在高温下过量的氧气中将样品有机物氧化为CO2，通过分离纯化得到纯净的CO2气体送人质谱测定其护δ13C值。
在已发表文章中，对于有机碳同位素的研究，人们所采用的氧化温度和氧化时间都有很大差异，但很少系统地研究有机碳同位素分析氧化条件对样品有机碳同位素测定结果的影响。为了解不同的氧化条件是否会造成样品的有机碳同位素分馏，以及不同氧化条件对样品有机碳同位素测定结果的影响程度，笔者采用封管法，选取了不同类型的样品（有机碳标准、植物、表土、黄土以及红粘土等），采用不同的氧化温度：500℃,550℃,650℃,750℃,850℃,900℃以及950℃等，恒温2.5 h,然后炉冷至室温。
实验结果表明：氧化温度为850℃，恒温时间为2.5 h，对于有机碳标准、植物、表土和较年轻的黄土样品，足以确保样品有机质氧化充分，δ13C值达到稳定，不会产生同位素分馏。
但对于深层黄土和红粘土样品，氧化温度为850℃，恒温时间为2.5 h，其δ13C值不能达到一个稳定值，仍有偏正趋势。这可能是由于深层样品成岩化作用强，样品中含有一些含碳的矿物包裹体，随温度上升到一定程度，才逐渐分解，释放出气体。对于深层黄土和红粘土样品，采用850℃甚至更高的氧化温度其δ13C值仍未达到稳定，合适的氧化温度需进一步的研究来确定。 |
| 中文关键词:碳同位素 土壤有机质 氧化条件 条件实验 |
| |
| A Discussion on the Effects of Oxidation Conditions On δ13C of Organic Matter |
|
|
| Abstract:The carbon isotopic composition of organic matter in soil has been widely used in global change research and in reconstruction of paleovegetation and paleoclimate. The basic principle of organic carbon isotopic analysis lies in transforming the organic matter into CO2 under the superfluous oxygen condition at high temperature, and then separating and purifying the resultants so as to get pure CO2 for determining their δ13C.
In the study of organic carbon isotope composition,various oxidation temperatures and oxidation durations have been used, but researches about possible effects of oxidation conditions on δ13C of organic matter are very insufficient. In order to understand whether various oxidation conditions may result in organic carbon fractionation, and what the degree of possible effects of various oxidation conditions on δ13C of organic matter is, the authors selected various types of samples (standard material for organic carbon，plants, modem soil, loess, red clay, etc.）and used the tube-sealed method to oxidize samples at various oxidation temperatures: 500℃，550℃，650℃，750℃，850℃，900℃and 950℃The oxidation temperature was then kept for 2. 5 hours, and after that the muffle was cooled to room temperature with door closed.
According to the experimental results, the oxidation temperature of 850℃ and the constant temperature time of 2.5 hours are enough to assure adequate oxidation of organic matter for such sam讨es as standard material for organic carbon, plants, modern soil and younger loess, with no fluctuation of their δ13C values and no fractionation.
Nevertheless, for older loess and red clay samples at oxidation temperature of 850℃and constant temperature time of 2.5 hours, the δ13C values cannot reach constancy and still have a somewhat positive trend. This is probably attributed to strong diagenesis of older samples which might contain some carbonaceous mineral inclusions. With the increase of oxidation temperature, these carbonaccous mineral inclusions begin to break down and release CO2 gas. For these samples, 850℃ or even higher oxidation temperature cannot guarantee the stableness of δ13C values of the organic matter, and hence further experiments are necessary for determining appropriate oxidation conditions. |
| keywords:carbon isotopes soil organic matter oxide tion condition conditional experiments |
| 查看全文 查看/发表评论 下载PDF阅读器 |
|
|
|
|
|
