[en] Methods for measuring sup(129)I concentration in natural environment have been described. β^-, γ^-, and x-spectroscopy, mass-spectroscopy, laser spectroscopy, activation analysis are among them. Lower limit of sensitivity of each method and the critical value of the sup(129)I/sup(127)I ratio are presented. It is recommended for achieving satisfactory accuracy and economy of measurements to take into account sup(129)I concentration value as well as sup(129)I/sup(127)I ratio when selecting the method

[en] A description is presented of a testing apparatus that consists of a two-section ionization mobility chamber and of an electronic system for processing and registration of signals, the so called box-car-integrator, the apparatus being employed for studies on the mobility of positive and negative ions generated in the air. The mobility spectra of positive and negative ions are shown along with a graph of dependence of the mobility of negative ions in the air upon humidity. The results obtained are discussed and hypotheses concerning the structure and composition of ions generated in the air of variable humidity are put forward. (author)

[en] The steady bombardment of the Earth's atmosphere by cosmic radiation induces numerous radioactive species in the atmosphere of which the best known are ¹⁴C and T. Others of interest include ⁷Be, ¹⁰Be, and several isotopes of chlorine. The eventual formation of ¹⁴CO₂ and its subsequent significance for archaeological dating were brilliantly established by Willard Libby in the 1940s. However, the initial reactions of nascent ¹⁴C in a mixture of N₂ and O₂ produce ¹⁴CO, as shown first in the lab. and then in the atmosphere. Because cosmic ray production rates are essentially constant in a given location, the observed concentration of ¹⁴CO provides an excellent tool for studying the removal process, oxidation by HO to form ¹⁴CO₂. Because ¹⁴CO₂ becomes incorporated into all living biological species, other molecules become labeled with ¹⁴C as well, including ¹⁴CH₄. Measurement of the ¹⁴C radioactivity of such molecules in the atmosphere allows apportionment of sources between biological and fossil fuel origins. Tritium atoms are also formed by cosmic radiation, and can subsequently be incorporated into the chemical forms HT and HTO. Although most T atoms from cosmic radiation are found as HTO, the much higher specific radioactivity of HT provides interesting insights into atmospheric processes. Lab. studies furnish important clues for understanding the atmospheric routes. The differences in radioactive half-lives cause the terrestrial locations of cosmic ray induced ⁷Be and ¹⁰Be to be primarily the atmosphere and the oceans, respectively. In a comparable manner, the chemistry of atmospheric radiochlorine divides between the very long-lived ³⁶Cl and three isotopes with half-lives less than an hour, ^34mCl, ³⁸Cl and ³⁹Cl

[en] The Australian Nuclear Science and Technology Organisation (ANSTO) in collaboration with the NSW Environment Protection Authority (EPA), Pacific Power and the Universities of NSW and Macquarie has established a large area fine aerosol sampling network covering nearly 60,000 square kilometres of NSW with 25 fine particle samplers. This network known as ASP commenced sampling on 1 July 1991. The cyclone sampler at each site has a 2.5 μm particle diameter cut off and samples for 24 hours using a stretched Teflon filter for each day. Accelerator-based Ion Beam Analysis(IBA) techniques are well suited to analyse the thousands of filter papers a year that originate from such a large scale aerosol sampling network. These techniques are fast multi-elemental and, for the most part, non-destructive so other analytical methods such as neutron activation and ion chromatography can be performed afterwards. Currently ANSTO receives 300 filters per month from this network for analysis using its accelerator based ion beam techniques on a 3 MV Van de Graaff accelerator. One week a month of accelerator time is dedicated to this analysis. This paper described the four simultaneous accelerator based IBA techniques used at ANSTO, to analyse for the following 24 elements H, C, N, O, F, Na, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Cu, Ni, Co, Zn, Br and Pb. Each analysis requires only a few minutes of accelerator running time to complete. 15 refs., 9 figs

[en] We are investigating methods to minimize the effects of background spectral reflectance on chemical concentration measurements in Differential Absorption Lidar at CO₂ laser wavelengths (9-11 μm). To test simple cancellation techniques, we collected field reflectance data corresponding to an absorption line of ethylene, and three laser lines to each side. The six off-absorption lines were then used to estimate the measured reflectance at the on-absorption line. A linear interpolation between the two closest open-quotes off close-quote fines predicted the reflectance at the open-quotes on close-quote line to 1-2%. The measured lidar returns included not only reflectance, but also effects due to atmospheric absorption and wavelength dependence in the lidar. This latter effect appears to be dominant in our data. Removing these effects from the data did not much improve the linear interpolation results. Simple techniques will work for chemicals with sharp absorption spectra. For chemicals exhibiting broad spectra, we are also pursuing research into more sophisticated techniques including partial-least-squares and neural network methods. 11 refs., 5 figs., 4 tabs

[en] A study to support ozone depletion and climatic change research is briefly summarized. The goal of the study to to develop back-propagation neural network techniques for detection of optically thin polar stratospheric clouds in Advanced Very High Resolution Radiometer thermal infrared imagery. The neural networks are being used to analyze hyperspatial and hypertemporal data; these data sets are defined in the paper. Assessments of the neural network are very briefly described; these include verification, accuracy, and robustness over time

[en] Short communication. 3 refs, 1 fig

[en] An optical model originally developed at 532 nm is applied to the Ruby laser wavelength of 694 nm. Functional relationships resulting from the model allow estimates of stratospheric aerosol surface area, volume, extinction-to-backscatter ratio, extinction, and effective radius from single wavelength, Ruby-lidar measurements. These parametrizations are valid for global stratospheric sulphate aerosols and liquid polar stratospheric clouds. Relative errors of the estimates are in the range of 15-45% for surface area, 15-30% for volume, 20-35% for effective radius. These errors are comparable to the ones characterizing direct, in situ techniques as optical particle counters. Comparisons with results of the original model at 532 nm are presented

[en] The principle of determining the atomized concentration by β-ray transmission measurement is described. The laboratory calibration was carried out with the wet filter paper to simulate water content in the air, from which the quantitative relation between the β-ray count rate and water content in the air was derived. Therefore, the atomized concentration can be determined by using the β-ray count rate measured in situ and the calibration curve. The tests in situ show that the β-ray transmission method used to measure the atomized concentration during the period of flood discharge from the high dam in hydro-power stations is precise, rapid and has a higher sensitivity than the γ-ray transmission method

[en] An overview is given on the activity in PIXE analysis of atmospheric aerosol done by a Hungarian team during the last decade. The aims of the work imply characteristics of the regional aerosol influenced by local emission and interregional transport. The results are embedded in related studies available in the literature selected according to the demand of the project without an attempt at completeness. (orig.)