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Nitrogen-15 (15 N) tracing is a technique to study the nitrogen cycle using the heavier, stable nitrogen isotope 15 N.Despite the different weights, 15 N is involved in the same chemical reactions as the more abundant 14 N and is therefore used to trace and quantify conversions of one nitrogen compound to another.
Nitrogen-15 is extensively used to trace mineral nitrogen compounds (particularly fertilizers) in the environment. [15] When combined with the use of other isotopic labels, 15 N is also a very important tracer for describing the fate of nitrogenous organic pollutants. [16] [17] Nitrogen-15 tracing is an important method used in biogeochemistry.
The rhizobia, which fix nitrogen and are symbiotic with plant roots, appear in several different families. The four families Nitrobacteraceae, Hyphomicrobiaceae, Phyllobacteriaceae, and Rhizobiaceae contain at least several genera of nitrogen-fixing, legume-nodulating, microsymbiotic bacteria. Examples are the genera Bradyrhizobium and Rhizobium.
Nitrifying bacteria are present in distinct taxonomical groups and are found in highest numbers where considerable amounts of ammonia are present (such as areas with extensive protein decomposition, and sewage treatment plants). [3]
The difference is whether the relative abundance is with respect to all the nitrogen, i.e. 14 N plus 15 N, or just to 14 N. Since the atmosphere is 99.6337% 14 N and 0.3663% 15 N, a is 0.003663 in the former case and 0.003663/0.996337 = 0.003676 in the latter.
Nitrogen-15 is a rare stable isotope of nitrogen. Two sources of nitrogen-15 are the positron emission of oxygen-15 [8] and the beta decay of carbon-15. Nitrogen-15 presents one of the lowest thermal neutron capture cross sections of all isotopes. [9] Nitrogen-15 is frequently used in NMR (Nitrogen-15 NMR spectroscopy).
15 N NMR is the most effective method for investigation of structure of heterocycles with a high content of nitrogen atoms (tetrazoles, triazines and their annelated analogs). [7] [8] 15 N labeling followed by analysis of 13 C– 15 N and 1 H– 15 N couplings may be used for establishing structures and chemical transformations of nitrogen ...
Approximately 78% of Earth's atmosphere is N gas (N 2), which is an inert compound and biologically unavailable to most organisms.In order to be utilized in most biological processes, N 2 must be converted to reactive nitrogen (Nr), which includes inorganic reduced forms (NH 3 and NH 4 +), inorganic oxidized forms (NO, NO 2, HNO 3, N 2 O, and NO 3 −), and organic compounds (urea, amines, and ...