Because of its high radio toxicity, the long lifetime of the main isotopes of plutonium and the long time that it remains in biological systems, a study of the content and nature of the distribution of plutonium in the environment is of considerable importance in radioecoiogy. In addition to data on the plutonium concentration in natural systems [1][2][3][4][5][6], information on the isotopic composition is also of considerable value [7][8][9][10][11][12], since this is an important characteristic when establishing the probable source of contamination and the dating of the contamination of natural systems. In fact, plutonium in the processed fuel of nuclear power plants [7] and weapons [13][14][15] has a specific isotopic composition, which in both cases differs considerably from that in global radioactive residues, which fall out on the earth as a result of tests on nuclear devices [6, 13, 14]. By analyzing the content and isotopic composition of plutonium in soil samples and deposits from the bottoms of reservoirs, taken near factories where used fuel from nuclear power plants is reprocessed or weapons-grade plutonium is processed, a considerable amount of industrial plutonium has been found, and it has been established how its relation to the concentration of global plutonium varies with time in the locality in question. In certain publications, based on a layer-by-layer investigation of the concentration and isotopic concentration in the soil [11] and from the bottoms of different reservoirs [8, 9] and arctic ice [I0], important conclusions have been reached on the migration of plutonium in the soil, river and marine systems, and on the geochronology of radioactive residues.The purpose of the research described in this paper was to determine the isotopic composition and concentration of plutonium in the soil of several regions, to investigate the possibility of isolating the fraction of industrial plutonium from the background of the plutonium of global radioactive fallout, and to use this information to identify the main regional sources of contamination.The Method of Analyzing, Selecting and Preparing the Samples. The most effective method of analyzing the plutonium contamination of natural systems is the combined use of ~-and mass spectrometry. Using eL-spectrometers one obtains, as a rule, the activity of 238pu and the overall activity 239+240pu, while using a highly sensitive mass spectrometer one can determine the isotopic ratios 240pu/239pu, 241pu/239pu and 242pu/239pu. These data give the complete picture of the content of all the main plutonium isotopes in the samples being investigated. To determine the concentration and isotopic composition of plutonium in the soil, sediments and other parts of the environment at the global level of contamination or less, a system has been developed based on the use of ratio-chemical and mass-spectrometer methods employing the improved commercial MI-1201 mass spectrometer.The ratio-chemical determination of plutonium in soil samples is based on isotopic dilution...
