[en] Dry deposition velocities and scavenging ratios are presented for a number of stations in India. The variation in scavenging ratios at a place was more than the differences in the average values at various locations studied. It was concluded that, a crude global-average value may be adequate for first-order calculations, but more accurate estimates may require the inclusion of precipitation type, height, amount, and vertical activity distributions into scavenging models. 8 references, 4 figures, 1 table

[en] The global values of the activity ratios of ⁷Be/³²P, ⁷Be/³⁵S, and ⁷Be/²²Na are presented and discussed. The wide range of variations of these observed ratios and residence times derived from them indicate a varying input of a stratospheric component of these isotopes. This shows that the troposphere is not a closed system and residence times calculated from the above ratios are likely to be larger than the actual values. More consistent results are obtained for tropospheric residence times based on ²¹⁰Bi/²¹⁰Pb activity ratios from various locations. The ⁷Be/³⁵S ratios are lower than the expected ratios by a factor of 2 to 3, calculated from cosmic ray production values, indicating other sources like bomb production. Since the ratios are less even during periods of low fallout activity, another source, such as graphite reactors is a possibility. (authors) 31 refs

[en] A comparison is made of the dilution potential of the Planetary Boundary Layer (PBI) at surface and high altitude locations in India and over the oceans of the Arabian Sea, Bay of Bengal region, using radon as a tracer. The significant difference in the diffusive properties of the PBL at these locations and their variations through the seasons are discussed and the use of these studies for plant siting pointed out. (author)

[en] Measurements on airborne fallout radioactivity for the period 1975 up to the middle of 1981 are given. Normally, these measurements are confined to Bombay, but after nuclear tests, some of the other stations where these measurements were carried out in previous years are operated for some time to study the levels of fresh activity. The levels of the long-lived fission products ¹⁴⁴Ce, ¹⁰⁶Ru and ¹³⁷Cs, and the short-lived fission products ⁹⁵Zr and ¹⁴⁰Ba, were measured, whenever they could be detected following nuclear tests, and tabulated. The data indicate that the activity varies by large factors from tests of similar yield, depending on the meteorological and other conditions. It was determined that the travel time for the Chinese test debris from Lop Nor, China to the West-coast of India is 14 to 16 days

[en] Measurements of the activities of short-lived radon and thoron daughters, long-lived RaD (²¹⁰Pb), and cosmic-ray produced ⁷Be in the surface atmosphere of different regions of India and the neighboring seas are presented. The seasonal and geographical variations of the activities and the meteorological significance of these variations are also discussed. Over land, the natural activities due to radon and thoron daughters undergo an annual and diurnal cycle, which is an index of the variation in the vertical mixing of the surface atmosphere. Over the oceans the diurnal variations are not so pronounced as over the land. Detailed measurements at stationary positions over the Arabian Sea showed significant changes in radon which were in phase at all the positions. The levels of radon daughters in the Kolar Gold Field mines, the second deepest in the world, have been measured. Maximum values are about 10 pCi/liter, and the daughter products are in a state of high disequilibrium. RaD(²¹⁰Pb) over the land undergoes a seasonal cycle similar to radon with winter maximums and summer minimums, indicating that it is mainly supported from ambient radon. Beryllium-7 undergoes a seasonal cycle similar to stratospheric fallout with reduced amplitude. This can be interpreted as being due to the presence of a seasonally dependent stratospheric ⁷Be mixing with a constant level of ⁷Be produced within the troposphere itself

[en] A number of non-uranium mines in India were monitored for airborne radon daughter product activity. The Equivalent Equilibrium Radon (EER) values were derived from the individual concentrations of RaA, RaB and RaC, calculated from the gross alpha decay of the filter paper air samples. Some of these mines had shown fairly high levels of airborne radioactivity. The EER values in the Ventilation Return Airways (VRA) of these mines varied from a few pCi/l to 20 pCi/l, while at a few underground working areas levels as high as 40 pCi/l were detected

[en] HV-70 filters were evaluated by comparison with Whatman GF/A glass fibre filters which have nearly 100% collection effeciency for natural radioactivity over a wide range of face velocities. The overall effeciency of HV-70 is calculated as 1.30. A major part of this factor is due to burial loss in HV-70 filters. The figure of 30% obtained for burial loss is similar to values reported in the literature. These values are based on the assumption of 100% retention for GF/A filters, but this seems to be true only within an accuracy of 5% from data reported in the literature. A 'spread' in the penetrating fractions that is much in excess of the expected statistical variations of the count rates suggests a variation in the factors controlling penetration of the filters by aerosols. (author)

[en] The global values of the activity ratios of ⁷Be/³²P, ⁷Be/³⁵S, and ⁷Be/²²Na are presented and discussed. The wide range of variations of these observed ratios and residence times derived from them indicate a varying input of a stratospheric component of these isotopes. This shows that the troposphere is not a closed system and residence times calculated from the above ratios are likely to be lager than the actual values. More consistent results are obtained for tropospheric residence times based on ²¹⁰Bi/²¹⁰Pb activity ratios from various locations. The ⁷Be/³⁵S ratios are lower than the expected ratios by a factor of 2 to 3, calculated from cosmic ray production values, indicating other sources like bomb production. Since the ratios are less even during periods of low fallout activity, another source, such as graphite reactors is a possibility. (orig.)

[en] Data on the measurements of ⁷Be in ground level air at Bombay for a seven year period are presented. The seasonal variation clearly shows a spring peak typical of a stratospheric source. As ⁷Be is continuously produced in the atmosphere, it can be used as a tracer in the atmospheric transport studies. (author). 3 refs., 3 figs

[en] Ten non-uranium mines from various regions of India have been surveyed for airborne radioactivity due to radon daughter products. The average air concentrations of RaA, RaB and RaC in the main ventilation return airways and in some selected areas in different working levels underground were assessed. The average equilibrium equivalent radon values and the RaC to RaB ratios were calculated. In one of these mines activity levels of the order of 500 to 1200 mWl were observed in different working areas. In all other mines the levels observed varied from a few mWL to about 100 mWL. The method of air sampling and analysis is briefly described. (author)