[en] A quantum chemical approach to reduced partition functions of isotopic molecules is described. The results of MINDO/3 calculations are presented for 13 molecules containing nitrogen. It has been found that in general the temperature characteristic of the isotope effect is steeper for organic compounds than for inorganic compounds. Bonding of nitrogen to carbon causes a significant increase of the isotope effect

[en] Using the compartment theory and appropriate computer codes, a new model of the nitrogen cycle for the earth crust and atmosphere has been subjected to a mathematical approach. Proceeding from the mathematical modelling of the time-dependent nitrogen distribution, modelling of the ¹⁵N distribution has been carried out, considering isotopic effects in the geosphere. Based on the chosen model quantitative data are given of the isotopic exchange with the upper mantle, of isotope effects of nitrogen chemically fixed in sediments and in metamorphism, and of the delta ¹⁵N values of magmatic and atmospheric nitrogen in the initial stage of crust development

[en] A number of metamorphic rocks has been studied with regard to their isotope ratio and chemically fixed nitrogen (NH₄⁺-N). The investigated phyllite, mica schist, and gneiss samples were taken from a compiled metamorphism profile of the Ore mountains. It has been found that the NH₄⁺-N content increases and the ¹⁵N/¹⁴N ratio decreases with increasing metamorphism. The isotope fractionation associated with the release of ammonia and molecular nitrogen has been determined between 350 ⁰C and 1050 ⁰C. On the basis of the results obtained the natural relationship between nitrogen concentrations and delta ¹⁵N values in rocks of differently developed metamorphism could be described

[en] According to data taken from literature and obtained from measurements the delta ¹⁵N values of magmatic rocks range from -16 to +31 parts per thousand and the nitrogen concentrations from 1 to 142 parts per thousand and acid rocks between -15.6 and +30.9 parts per thousand. Correlations were found between the logarithm of nitrogen concentrations and ¹⁵N values. On the assumption that nitrides are involved in the isotopic exchange in the lithosphere and are possibly the dominant nitrogen compounds in the upper mantle, conclusions could be drawn with regard to the causes of isotope variations of nitrogen in the crust and mantle

[en] Delta ¹⁵N values and nitrogen contents have been determined in humic and bituminous organic sediments of various grades of maturity. Their changes under thermal load have been investigated in model experiments. It was found that nitrogen concentrations varied from 0.8 to 1.44 per cent and the delta ¹⁵N values from +3.5 to +6.3 parts per thousand in humic Carboniferous coals (lignite to anthracite). Pyrolysis of a gas-flame coal and a forge coal released nitrogen at 650 ⁰C and 1000 ⁰C, resp., with delta ¹⁵N values of +2.8 and -7 parts per thousand, resp. The bituminous sediments investigated contained 0.1 to 0.8 per cent nitrogen with delta ¹⁵N values of +4.2 to +10.7 parts per thousand. The results obtained are discussed in terms of the elucidation of nitrogen genesis in natural gases

[en] Isotopic variations of nitrogen in soils may have their roots in three different forms: fluctuations of the isotopic composition in nitrogen compounds of the precipitations (inputs), the result of isotope effects in ion exchange processes and lastly of isotope effects in metabolic processes. Arable fields may be changed by anthropogenic processes, especially by applying nitrogenous fertilizers. The different isotopic compositions of the nitrogen compounds in soils may be used as natural tracers, i.e. tracing substances in soils and ground waters. (author)

[en] Thermodynamic studies of solubility and adsorption of nitrogen and nitrogen-methane mixtures, and isotope effects under geologic conditions are reported. The results are used for modelling natural gas migration and for developing an appropriate geochemical isotope model of genesis and accumulation of natural gases

[en] A collection of natural diamonds from Namibia, consisting of yellowisch colored single stones, has been analyzed for the nitrogen isotope ratio. To this end the diamonds were graphitized in a special vacuum apparatus. The mass spectroscopic isotope analysis resulted in a mean delta ¹⁵N value of 1.5 +- 0.2 parts per thousand. The value is discussed on the basis of model considerations

[en] Proceeding from a survey on nitrogen in the atmosphere, biosphere, hydrosphere, and lithosphere and nitrogen determination methods, a detailed review is given of procedures that allow to transform any nitrogen-containing starting material into molecular nitrogen for mass spectroscopic isotope analysis