第五讲稳定氮同位素.pptVIP

研究案例2 Study Case 2 研究案例2 Study Case 2 研究案例2 Study Case 2 同位素质量平衡 作业 通过文献阅读说明，如何利用N、O同位素示踪含N化合物的转化途径。 * 第五讲 稳定氮同位素 稳定氮同位素: 14N: 99.64% 15N: 0.36% standard = N2 in air (15N/14N = 0.00368) measured as: N2 典型氮库的同位素组成: Nitrate, rain: -13 to +2 Organic N, soil: 0 to +9 Fertilizer: -5 to +5 Animal waste: +8 to +22 氮同位素及其循环Nitrogen Isotopes and Nitrogen Cycling A DELTA 15-N = +10 ‰ means there is 10 parts per thousand (or permil) more 15-N in the sample than in the standard. A DELTA 15-N = -10 ‰ means there is 10 parts per thousand (or permil) less 15-N in the sample than in the standard. Delta (d) value = Ratio sample Ratio standard Ratio standard x 1000 - Where Ratio is the ratio of 2 isotopes of an element, such as 15N/14N for nitrogen, for a sample or a standard. 氮同位素及其循环Nitrogen Isotopes and Nitrogen Cycling People usually find the negative d values a bit confusing, but they are just a product of what material was chosen as the standard. Example: For N, the ratio of 15N/14N in Air is about 1/250. If a sample has 1% more 15N than Air (=1/250), its ratio would be: 1.01/250. This 1% corresponds to +10‰. If a sample has 1% less 15N than Air -- (= 0.99/250), this is -10‰. 氮同位素及其循环Nitrogen Isotopes and Nitrogen Cycling heavy vs. light isotopes the “heavy” isotope is the one with more neutrons; it is also generally the less abundant isotope. enriched vs. depleted remember to state what isotope is in short supply: does “enriched nitrogen” mean that: the nitrogen is enriched in heavy nitrogen OR the nitrogen is enriched in light nitrogen? positive vs. negative -10 ‰ is more positive than -20 ‰ . 氮同位素及其循环Nitrogen Isotopes and Nitrogen Cycling 1 天然气；2 火成岩；3 火山气；4 受粪肥污染土壤中的氮；5 动物粪便(厩肥)或污水中的NO3-；6 沉积岩中的有机质；7 石油；8 非豆科植物；9 垦植土壤和受生活污水污染土壤中的氮；10 土壤有机氮矿化形成的NO3- ；11天然土壤中的氮 ；12 雨水；13 煤；14 受化肥和工业废水污染土壤中的氮；15 含氮化肥的NO3-；16 豆科植物；17 泥炭 不同氮源的δ15 N值分布图 氮同位素及其循环Nitrogen Isotopes and Nitrogen Cycling -50 -40 -30 -20 -10 0 10 20 30 40 50 1 15 2