| 痕量甲烷碳同位素真空制样系统的研制与贵州省一些水稻田甲烷碳同位素组成的初步测定 |
| 李金华
|
| 1993
|
| 学位授予单位 | 中国科学院地球化学研究所
|
| 学位授予地点 | 中国科学院地球化学研究所
|
| 学位名称 | 博士
|
| 学位专业 | 环境地球化学
|
| 关键词 | 痕量甲烷
碳同位素
真空制样系统
水稻田
|
| 摘要 | 甲烷碳同位素（δ~(13)C）在辩识甲源汇和提示甲烷的产出机理、传输途径方面有重要作用国内因痕量甲烷的同位素制样问题未能开展有关的研究工作。我们研制了一套痕量甲烷碳同位素的真空制样系统，并对贵州省内一些水稻田的甲烷δ~(13)C值作了初步测定。痕量甲烷碳同位素真空制样系统充分考虑到气样中CO_2、H_2O、CO和非甲烷烃等杂质气体对甲烷同位素制样的干扰，在吸收和借鉴前人工作基础上研制出来，在设计上具有以下特点：（1）制样过程中杂质气体的清除采用多环“冷阱串”，保证冷冻过程的可靠性和稳定性。（2）甲烷的高温转化使用了新型HA-02贵金属催化剂，实验检测表明：在较低的温度下（400 ℃ - 500 ℃）HA-02催化剂能确保甲烷的充分氧化分解。（3）CO_2气样设计有样品管和熔封管两种接收方式，便于收集和贮存。（4）真空制样系统可以制备气样中CO_2、CO的同位素样本，与质谱仪配合可以同步监测CO_2、CO的碳氧同位素组成。同位素条件检测实验证明了痕量甲烷碳同位素真空制样的可行性。用自行研制的真空系统对贵州省内一些水稻田甲烷的δ~(13)C值初步测定表明：稻田甲烷以富集轻同位素为特征，δ~(13)C变化在-54.05 ～ -64.47‰，平均为-60.67 ± 3.56‰，比较接近肯尼亚水稻田的研究结果，同时甲烷δ~(13)C值在一天中从上竿到晚上有逐步富集~(13)C的趋势。 |
| 其他摘要 | Measurements of stable carbon isotopic composition of CH_4 can be used to reveal clues as to CH_4 source、sinks and machenisms of CH_4 production、transport and emission. Thus far few studies on stable carbon isotopic ratios of various sources of CH_4 in China have done. Here we managed to develooped an intergrated set of vacuum line for analysis of ~(13)C/~(12)C ratios of trace methane, and primarily measured δ~(13)C values of six trace methane gas samples collected from some of GuiZhou's rice paddies by stainless steel tank. Our vacuum line is established based on many similiar designing of CH_4 conversion lien in the literature, suggesting adequate consideration of the removal of disturb caused by CO_2、H_2O、CO and non-methane hydrocarbon (NMHC) in the air samples, and shows the following characteristics: (1) multiple-loop cold traps in the vacuum line are used to condensed more reliably and steadily CO_2、H_2O、CO and NMHC at the liquid nitrogen temperature than the common U-taped cold trap. (2)A new kind of noble metal cataltyst (HA-02) supported on 2 ～ 3 mm Aluminium oxide pellets are used for CH_4 conversion at a lower temperature of 400 ℃ - 500 ℃. (3) The resulting CO_2 from methane conversion can be collected in either common CO_2 sample tubing or fusing tubing in which CO_2 can be kept in store for a long time. (4) Our vacuum line can also moniter simultaneously the variation of ~(13)C/~(12)C and ~(18)O/~(16)O ratios of CO_2 and CO in the air samples with the coordination of mass spectrometry. The testing experiments by comparison with the δ~(13)C values of the standard CH_4 gas sample have proved our vacuum line is efficient and workable in processing trace CH_4. Additional, our measurements of ~(13)C/~(12)C ratios of CH_4 from GuiZhou's rice paddies indicated: methane from rice paddies is characterized by relatively depleted -~(13)C compared with the present atmospheric CH_4, with a mean δ~(13)C values of - 60.67 ±3.56‰, ranging from -64.47‰ to -54.05‰. Our results are very consistent with that derived from Kenya's rice paddies. Meanwhile δ~(13)C values of CH_4 from Gui Zhou's rice paddies are found to show a tendency of enriched -(13)C by degrees along the time during a day. |
| 页数 | 60
|
| 语种 | 中文
|
| 文献类型 | 学位论文
|
| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/3916
|
| 专题 | 研究生_研究生_学位论文
|
推荐引用方式
GB/T 7714 |
李金华. 痕量甲烷碳同位素真空制样系统的研制与贵州省一些水稻田甲烷碳同位素组成的初步测定[D]. 中国科学院地球化学研究所. 中国科学院地球化学研究所,1993.
|
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
修改评论