Oxygen and Hydrogen Isotope Measurements in Plant Cellulose Analysis
Oxygen and Hydrogen Isotope Measurements in Plant Cellulose Analysis
复制标题
植物纤维素分析中的氧和氢同位素测量
DOI：
10.1007/978-3-642-83349-6_5
复制
发表时间：
1989
影响因子：
5.2
通讯作者：
L. Sternberg
中科院分区：
文献类型：
--
作者：
L. Sternberg
同位素是原子核中质子数相同但中子数不同的原子。我们大多数人都熟悉不稳定的同位素（例如碳-14），它们会衰变成另一种元素（例如碳-14衰变成氮-14）。然而，本章讨论的是不衰变因而不产生放射性的稳定同位素。在植物生物量中发现的最丰富的元素有两个或两个以上的稳定同位素。碳以碳-12（6个质子和6个中子）或碳-13（6个质子和7个中子）的形式存在，氢可以以氘（1个质子和1个中子）或protium（1个质子）的形式存在，氧可以以氧-16（8个质子和8个中子），氧-17（8个质子和9个中子）或氧-18（8个质子和10个中子）的形式存在。中子数最少的同位素通常被称为较轻的同位素，中子数较多的同位素被称为较重的同位素。质量最小（中子数较低）的元素的同位素的自然丰度大于质量较大的元素。因此，生物圈中的碳由98.89%的碳12和1.11%的碳13组成（Nier and Gulbransen 1939）。氢由99.9844%的质子和0.0156%的氘组成，氧由99.763%的氧-16,0.0375%的氧-17和0.1995%的氧-18组成（Hoefs 1973）。测量稳定同位素的绝对丰度是极其困难的，因此它们通常是相对于一个标准来测量和表示的。
Isotopes are atoms containing the same number of protons but a different number of neutrons in their nucleus. Most of us are familiar with unstable isotopes (e.g., Carbon-14) which decay to another element (e.g., Carbon-14 decays to Nitrogen-14). This chapter, however, is concerned with stable isotopes which do not decay and thus produce no radioactivity. The most abundant elements found in plant biomass have two or more stable isotopes. Carbon exists either as carbon-12 (6 protons and 6 neutrons) or carbon-13 (6 protons and 7 neutrons), hydrogen can be found either as deuterium (1 proton and 1 neutron) or protium (1 proton), and oxygen can be found either as oxygen-16 (8 protons and 8 neutrons), oxygen-17 (8 protons and 9 neutrons), or oxygen-18 (8 protons and 10 neutrons). Isotopes having the least number of neutrons are usually called the lighter isotopes, and those having more neutrons are called the heavier isotopes. The natural abundance of the isotope of those elements with the least mass (lower number of neutrons) is greater than those with the larger mass. Thus carbon in the biosphere is comprised of 98.89% carbon 12 and only 1.11% of carbon-13 (Nier and Gulbransen 1939). Hydrogen is comprised of 99.9844% protium and 0.0156% deuterium, and oxygen is comprised of 99.763% oxygen-16, 0.0375% oxygen-17 and 0.1995% oxygen-18 (Hoefs 1973). It is extremely difficult to measure absolute abundance of stable isotopes, thus they are usually measured and expressed relative to a standard.