No abstract

No abstract

contaminant washout and rainout from the atmosphere by precipitation are considered. Formulas of decreasing contaminant concentration in precipitation and in the air as a function of duration of precipitation are deduced. Coefficients of contaminant washout (below the cloud) and rainout (in the cloud layer of the atmosphere) for gases and aerosols are determined from comparison of theoretical curves with experimental data. Rainout of almost all the gases of the atmosphere is, at least, a factor of 10 less than that of aerosols.

No abstract

The present radiation conditions on the territory of the Russian Federation formed over a period of decades and are a consequence of the development of the nuclear-fuel cycle, the production and testing of nuclear weapons, and accidents at the Industrial Association "Mayak" and Cbernobyl nuclear power plant in 1986. We shall briefly describe the radioactive contamination of the environment in 1994-1995. Radioactive Contamination of the Atmospheric Layer Near the Ground. The radioactive contamination of the atmosphere near the ground is monitored by Rosgidromet by the method of analyzing aerosol samples collected by means of air-filtering units at 53 observation points and with vertical screens at 13 observation points as well as samples of atmospheric precipitation which are collected with the aid of horizontal boards at 445 points and stations, including in the near zones for monitoring different radiation-hazardous objects.On the territory of Russia the concentration of the total fl-activity of nuclides in the atmosphere near the ground in 1995 equaled -2.2.10 -4 Bq/m 3 on the average, which is 10% higher than the average value for 1994. The total fl-activity of atmospheric precipitation on the underlying surface was equal to an average of 1.5 and 1.6 Bq/(m2-day) in 1994 and 1995, respectively. The maximum precipitation and concentration of t3-active radionuclides are observed systematically in regions of uranium deposits and locations where building materials, containing tailings and other wastes from uranium mining, are used --Chitin, Irkutsk, Omsk, and other regions.The largest number of cases of a short-time ten-fold increase above the background level for atmospheric precipitation and a five-fold increase for concentration of radionuclides in air during the last two years was observed in the Nizhegorod region. In all cases a high contamination was noted for not more than 1 day, and only products of decay of radium and thorium were found in the samples.Outside the territories contaminated as a result of the Chernobyl accident, the average 137Cs concentration in air in 1994-1995 fluctuated from (2-4).10 -7 Bq/m 3 in Zapolyar'e and in the northern regions of Eastern Siberia up to 3.6.10 -6 Bq/m 3 in the southern portion of the European part of Russia. The weighted-mean 137Cs concentration in air over the territory of Russia in 1995 was equal to 5.1-10 -7 Bq/m 3, which is somewhat lower than the 1994 level (6-10 -7 Bq/m3). In 1995 the highest monthly average concentration of 137Cs in air was observed in August-September in Ryazan' (3.8.10 -6 and 4.3.10 -6 Bq/m 3, respectively, and in August-October in Obninsk (4.5-10 -6 and 3.5-10 -6 Bq/m 3, respectively). This is ten times higher than the average concentration over the country, but 106 times lower than admissible for category B population (AC B = 18.1 Bq/m3). The 9~ concentration in air in 1994-1995 did not change and was equal to 1.6-10 -7 Bq/m 3. The atmospheric fallout of 137Cs in 1995 constituted an average of 1 Bq/(m2-yr), which is 1.4 times lower than...