Investigations of the state of the environment are closely linked with the determination of the elemental composition of different samples. Nuclear-physical methods of analysis are widely used for these purposes. The accuracy of the methods is determined by the statistical errors and systematic and random errors, which are difficult to take into account and are associated with the content of one or another element in the sample, the characteristics of the sample, the sample preparation, the choice of external standards, the measurement conditions, the processing of the experimental information, and so on [ 1 ]. For this reason, there is a natural variance in the data obtained by different methods and on different installations. It is obvious that the accuracy and reliability of the results are higher when the elemental analysis is performed by several methods.In the present work we investigated the elemental composition of samples of six types of plants: junipers, ziziphora, mints, yarrow, sage, and ephedra, collected on one of the preserved stationary sites at the Chatkal' Biospheric Preserve [2]. The investigations were performed by four nuclear-physical methods: neutron-activation, ",c-activation, x-ray spectral, and x-ray fluorescence. The results obtained by these methods are compared with one another.Samples and Standards. The plants were dried to an air-dry state and subject to preliminary grinding, after which they were carefully ground in a mill in an agate mortar to a powdered state with particle size 1-5 ~m. The required amounts of powder were obtained by weighing with an error of -0.01 g. The powder was packaged in marked containers (Table 1). In the case of the x-ray spectral analysis, the samples were prepared as follows: to produce electrical conductivity, -80 mg of spectroscopically pure graphite was added to a -500 mg sample, the mixture was once again carefully ground and compacted under a pressure of 30 tons/cm 2 into a 2 mm thick tablet. The SBMT standards were used as the external references (the SVT-7 standard was used in the case of x-ray spectral analysis).Experimental Setups. The neutron-activation investigations were conducted on the basis of the VVR-SM reactor at the Institute of Nuclear Physics of the Academy of Sciences of the Republic of Uzbekistan [3]. To determine the content of elements for short-and long-lived radionuclides, the samples were irradiated for 20 sec and 15 h, respectively, in a vertical channel with neutron flux density 1013 and 6.1013 sec-l.cm -2, and then held for _> 20 min, 7 or 30 days, depending on the half-life of the radionuclides being analyzed. The spectra were registered with a Ge(Li) detector with a volume of 120 cm 3 and an energy resolution of 3.5 keV on the 133 keV line of the 6~The 3,-activation investigations were conducted on a setup assembled on the basis of the MT-22S microtron at the Nuclear Physics Laboratory of the Samarkand State University [4]. The samples were irradiated for 4 h with "y-ray bremsstrahlung generated in a tungsten target by a ...
