Toshio Kataoka

A STUDY OF THE ATMOSPHERIC BOUNDARY LAYER USING RADON AND AIR POLLUTANTS AS TRACERS

Concentrations of radon 222Rn andair pollutants, meteorological parametersnear the surface and vertical profiles of meteorological elements were measured atUchio (Okayama City, Okayama Prefecture, Japan) 12 km north from the coast ofthe Inland Sea of Japan. In the nighttime, the 222Rn concentration increased in the case of weak winds, but did not increase as much in the case of moderate or strong winds, as had been expected. In the daytime, the 222Rn concentrationheld at a slightly higher than average level for the period from sunrise to about 1100 JST. It is considered that this phenomenon is due to a period of morning calm, that is, a transition period from land breeze to sea breeze.NO, which is sensitive to traffic volume,brought information concerning advection.Oxidant concentrations,which reflect the availability of sunlight,acted in the reverse manner to 222Rnconcentrations. Thus, a set of 222Rn and air pollutants could provide useful information regarding the local conditions of the atmospheric boundary layer.

The spatial and temporal variations of atmospheric 212Pb concentrations

Abstract Three monitoring stations were selected in the village of Kamisaibara. Atmospheric 212 Pb was measured using the step filter paper method. Atmospheric temperature, atmospheric pressure, and precipitation were measured as meteorological parameters. The correlation coefficients of atmospheric 212 Pb concentrations for stations ranged from 0.83 to 0.85. As precipitation increased up to 30 mm/d, atmospheric 212 Pb concentrations decreased sharply. Atmospheric 212 Pb concentrations were nearly zero above 30 mm/d precipitation. The observed 212 Pb concentration decreased with increasing precipitation and was below the detection limit when the precipitation reached 30 mm/d. The atmospheric 212 Pb concentration was significantly affected by meteorological parameters, especially precipitation.

222Rn in private well water in the vicinity of uranium mines over ten years

Abstract There are many small uranium mines of the sedimentary type in Kamisaibara, Okayama Prefecture, Japan. As inhabitants in Kamisaibara consume water from privately-dug wells, it is important to investigate distributions of 222 Rn in privately-dug well water in the vicinity of the mines. The determination of 222 Rn in well water was carried out from April 1980 to October 1990. Though small in area (16 km 2 ), each well water has its own characteristic activity concentrations of 222 Rn. The activity concentrations of 222 Rn are almost constant for each specific well over a long period (about 10 years). In general, the correlation coefficients for several sampling points are small. As Akawase and Tennoh are situated in the same rock type, the correlation coefficient is the highest value in this area. The estimated dose equivalent for the human stomach is approximately 0.4–54 μSv/year. The type of distribution of 222 Rn in privately-dug well water is log normal.

Measurement of Soil Concentration Profile of Radon-222 and Its Effect on Exposure Rate

The concentration profiles of 222Rn in the soil air are measured at several selected sites in different parts of Japan, together with the 226Ra concentrations in soil, 222Rn escape-to-production ratios of soil and the characteristic physical properties of the soil. The resulting data are used to derive the vertical soil concentration profile of 222Rn, which is found to differ distinctly from site to site. Measurements are also made of the concentrations in soil of 232Th and 40K. Based on these data, the exposure rates due to the nuclides in the soil are calculated for a level 1m above ground at each site. The lowering of exposure rate due to the diffusion loss of 222Rn is estimated to be 2~13% of the total exposure rate due to naturally occurring radionuclides in the soil.