Variation Of 222Rn Concentration Research Articles

High-resolution mapping and time-series measurements of 222Rn concentrations and biogeochemical properties related to submarine groundwater discharge along the coast of Obama Bay, a semi-enclosed sea in Japan

High-resolution mapping along the coast and time-series measurements of the radon-222 (222Rn) concentrations in the shallow zone in a semi-enclosed sea, Obama Bay, Japan, were undertaken in 2013. The temporal and spatial variations in the 222Rn concentrations were analyzed in parallel with meteorological conditions, physical–biogeochemical characteristics, and the submarine groundwater discharge (SGD) flux measured with a seepage meter. These data indicate that the groundwater influences the water properties of the bay and that the groundwater supply pathways are not limited to the local SGD. The concentrations of 222Rn flowing into the bay from rivers was known to be relatively high because groundwater seeps from the river bed. High-222Rn water was almost always present around the river mouth, and northward advection of the water affected the distribution of 222Rn concentrations in the bay. The southward wind suppressed the advection of the high-222Rn water and largely controlled the temporal variations in 222Rn concentrations at a station located on the north side of the river mouth, whereas the local SGD affected the short-term changes in the 222Rn concentrations. The concentrations of 222Rn and chlorophyll-a, an indicator of phytoplankton biomass, show a significant positive correlation in the surface layer along the coastline in seasons when the nutrient supply was the main factor limiting primary productivity.

A complexity analysis of 222Rn concentration variation: A case study for Domica cave, Slovakia for the period June 2010–June 2011

In this paper we have analyzed 222Rn concentration variation in Domica cave (Slovakia) for the period June 2010–June 2011. In that sense we have applied a complexity analysis on 222Rn concentration time series. We have considered possible existence of a periodical component in the variation of 222Rn concentration and some environmental parameters, as well as possible correlation between them. In addition we have offered novel complexity measures based on the Kolmogorov complexity (KC), i.e. the Kolmogorov complexity spectrum, its highest value (KCM) and the integral Kolmogorov complexity (KCI). These measures have been applied on 222Rn concentration time series: (i) to establish the dependence of 222Rn concentration on cave environmental parameters (wind speed inside the cave, external wind speed, air temperature, atmospheric pressure and CO2 concentration) and (ii) to see whether influence of some parameters make the distribution of measured quantity less or more stochastic.

Development of Three-Dimensional Numerical Model for 222Rn and its Decay Products Coupled with a Mesoscale Meteorological Model I. Model Description and Validation

A three-dimensional Eulerian numerical model for 222Rn and its decay products coupled with a mesoscale meteorological model has been developed and applied to the reproduction of the daily and monthly variations of 222Rn concentration, the monthly variation of 210Pb deposition in Japan and the temporal variation of gamma dose rate after the cold front passage in the coastal area of the Japan Sea for the verification of model capability. The results are as follows: (1) The model reproduced the monthly variation of surface 222Rn concentration in remote islands, but underestimated inland concentration due to a coarse vertical resolution near the surface of the model. (2) The model reproduced the seasonal variation of the observed and the long-term yearly averaged 210Pb depositions as long as precipitations are predicted precisely. (3) The model reproduced the rise of gamma dose rate in precipitation accompanied by the cold front passage. In particular, 222Rn decay products in melted snow and graupel contributed the rise of gamma dose rate.

A survey of indoor workplace radon concentration in Japan

Radon ( 222Rn) concentration was measured at indoor workplaces in Japan to estimate effective dose to the public from 222Rn and its progeny. Measurements were made from 2000 to 2003 at 705 sites in four categories of office, factory, school and hospital. Passive type Rn monitors equipped with two sheets of polycarbonate thin films for measuring radon concentrations were installed at observation sites and replaced every 3 months to observe seasonal variations in 222Rn concentrations. The range of annual mean 222Rn concentrations for all sites was 1.4–182 Bq m −3, with the arithmetic mean and standard deviation were 20.8 and 19.5 Bq m −3. Annual mean 222Rn concentration observed at office, factory, school and hospital were 22.6, 10.1, 28.4 and 19.8 Bq m −3, respectively. Seasonal variations in 222Rn concentrations at offices, schools and hospitals were similar to those found in dwellings, and variations in factories were similar to those found in outdoor environments. 222Rn concentration observed in every quarter period was found to decrease as follows: school > office > hospital > factory. The average effective dose to the public due to 222Rn was estimated to be 0.41 mSv y −1 weighted by the working population. Considering the 222Rn exposure in indoor workplaces, effective dose to the general public is estimated to be in the range from approximately 0.42 to 0.52 mSv y −1.

Diurnal Variation in Radon Concentration and Mixing-Layer Depths

Variation of 222Rn, its short-lived daughters and 212Pb concentrations in the atmosphere, and conditions of the lower atmosphere were observed simultaneously at Kamisaibara Village in Japan. The variation of 222Rn concentration and the ratio of the concentrations of 212Pb and the short-lived daughters of 222Rn during nighttime is explained by sodar echoes and temperature profiles obtained by an instrumented tethered balloon. Depths of the convective mixing layer estimated using the 222Rn concentration, using the surface sensible heat flux, and obtained by low-level sondes are compared and found to be in approximate agreement.

Radon in residences: influences of geological and housing characteristics.

222Rn is a radioactive gas emitted during the decay of 238U. 222Rn is a recognized lung carcinogen in humans and a common indoor air contaminant. This paper describes the results of research undertaken in 894 residences of the Province of Quebec (Canada), in which one of the objectives was to evaluate the influence of geological and housing characteristics on 222Rn levels. After a random selection of homes, 222Rn concentrations were measured with alpha track detectors in the basement and the main bedroom during two consecutive 6-mo periods. Geological subsoil characteristics were determined from various sources (e.g., geological maps, databanks on uranium sampling in lake and stream sediments), and housing characteristics were documented with a questionnaire. Statistical variance analysis of data indicates that geological factors only explain 5% and 4.5% of the variations in 222Rn concentrations, respectively, in the basement and on the first floor. When variables relative to housing characteristics are added, the analysis explains only 18% and 15% of the variations in 222Rn concentrations in the basement and on the first floor. These results illustrate the difficulties in predicting 222Rn concentrations in homes.

222Rn in Water

The U.S. Environmental Protection Agency has proposed a drinking water standard for 222Rn in public water supplies. When promulgated, operators of public water supplies will be required to determine water 222Rn concentrations. Most likely, water samples will be collected and mailed to laboratories for analyses. Additionally, it is probable that homeowners will test private well water in a similar manner by collecting water samples and mailing them to a laboratory for 222Rn analyses. In anticipation of these actions, this study was conducted to evaluate two methods of water sample collection and to evaluate the potential losses of 222Rn from water samples mailed to a laboratory. Thirdly, temporal variations in 222Rn concentrations in several groundwater supplies in North Carolina were examined. Water supplies at four sites in eastern North Carolina and five sites in western North Carolina were sampled over a 7-mo period beginning in the fall of 1993 and continuing through the spring of 1994. Samples were analyzed using a liquid scintillation method. This study showed that a "slow-flow" method is not only suitable for sample collection, but may be the preferable method for water sample collection since slow-flow collection resulted in less 222Rn loss than was observed during syringe collection, i.e., the water 222Rn concentrations in samples collected by the slow-flow method were generally higher. Further, based on this study, mailing water samples to a laboratory for analysis should not have a substantial effect on the measured 222Rn concentrations. Consequently, water samples can be collected by the slow-flow method by water supply operators, as well as homeowners, and mailed to laboratories for 222Rn analyses with reasonable assurance that the samples have not suffered significant 222Rn loss. Temporal variations in water 222Rn concentrations were observed in this study. One factor complicating the study of temporal variations in 222Rn concentrations was the striking influence that inconstant water usage and inadequate well purging prior to sample collection had on 222Rn loss from the water.

Variation of 222Rn Concentration in Outdoor Air due to Variation of the Atmospheric Boundary Layer

Variation of 222Rn concentration in outdoor air, returns of a monostatic acoustic sounder and sensible heat flux are simultaneously observed at Okayama-shi in Japan. The sensible heat flux is measured with an eddy correlation method using a sonic anemometer and a copper-constantan thermocouple thermometer. Using height of a surface-based inversion layer obtained by the acoustic sounder returns and two 222Rn concentrations during the presence of the surface-based inversion layer, the exhalation rate of 222Rn at this site is estimated to be about 0.01 Bq.m-2.s-1, which agrees well with the exhalation rate of 222Rn estimated at Nagoya-shi in Japan. Using the estimated exhalation rates of 222Rn and the variation of the 222Rn concentration in the daytime, heights of mixing layers are estimated. These heights of the mixing layers are larger than the height of the mixing layer estimated using the sensible heat flux and the representative vertical profile of the autumnal night time air temperature in this area.

Variation of 222Rn Concentration in Outdoor Air due to Variation of the Atmospheric Boundary Layer

Variation of 222Rn concentration in outdoor air, returns of a monostatic acoustic sounder and sensible heat flux are simultaneously observed at Okayama-shi in Japan. The sensible heat flux is measured with an eddy correlation method using a sonic anemometer and a copper-constantan thermocouple thermometer. Using height of a surface-based inversion layer obtained by the acoustic sounder returns and two 222Rn concentrations during the presence of the surface-based inversion layer, the exhalation rate of 222Rn at this site is estimated to be about 0.01 Bq.m-2.s-1, which agrees well with the exhalation rate of 222Rn estimated at Nagoya-shi in Japan. Using the estimated exhalation rates of 222Rn and the variation of the 222Rn concentration in the daytime, heights of mixing layers are estimated. These heights of the mixing layers are larger than the height of the mixing layer estimated using the sensible heat flux and the representative vertical profile of the autumnal night time air temperature in this area.

Measurements of regional distribution of radon-222 concentration.

Outdoor 222Rn concentrations were measured with electrostatic integrating radon monitors (EIRM) at 40 points around Nagoya, in which 15 sets of 2-month-exposure data over 2.5 yr were obtained. Seasonal variation of 222Rn concentration showed a clear pattern which had a spring-to-summer minimum and an autumn-to-winter maximum. Annual means 222Rn concentration ranged 3.5~11.7 Bq·m−3 depending on locations. Higher concentrations were obtained in mountainous regions while lower concentrations were obtained near the sea. The relation between atmospheric 222Rn concentration and uranium content of granitic rocks was also discussed. High level 222Rn concentrations were obtained over areas of granitic rocks which were comparatively uranium-rich. As an almost linear relationship was recognized between the 222Rn concentration and exposure rate due to external natural radiation, a close correlation was anticipated between the concentration and 226Ra content of soil. From the obtained regional distribution of 222Rn co...

Radon anomaly as a possible precursor of a submarine earthquake

In the framework of investigating the ventilation of deep-sea basins in the Indonesian archipelago, 222Rn was determined in near bottom water samples. In one of these basins, the Halmahera Basin, excess 222Rn concentration and the related standing crop was unexpectedly high. At this station excess Radon has an almost uniform concentration of about 2 dpm·kg −1 up to 120 meters above the bottom. In this paper the possibility is discussed that the high standing crop in this basin is connected with three submarine earthquakes with a magnitude of resp. 4.4, 5.4 and 5.9 mb that took place four days after we took the samples, possibly in combination with submarine faults, which are typical for the Indonesian archipelago. The epicentres were within 100 km from the station. All over the world variations in 222Rn concentrations have been observed prior to earthquakes (up to 500 km from the epicentre). This can be regarded as an important non-seismic precursor to earthquakes, but it has to our knowledge never been observed in deep-sea basins.

A Simple Model for Estimating the Mixing Depth from the Diurnal Variation of Atmospheric 222Rn Concentration

Abstract A simple model is proposed for estimating the mixing depth from the diurnal variation of 222Rn concentration in surface air. The comparison is described between the mixing depth calculated with the model and that determined from observations of temperature profiles with rawinsondes, which indicates good agreement.

通気式電離箱による横坑内のラドン濃度の測定, およびその濃度変化と地震発生の関係

The concentration of 222Rn in air in the gallery at Mikawa. Crustal Movement Observatory (Toyohashi City, central Japan) has been continuously measured with a flow-type ionization chamber since April, 1977 for the investigation of pre-earthquake anomalies. The observed 222Rn concentration shows remarkable increase after rainfall. It seems that 222Rn rich air is squeezed in the gallery by the contractile force caused by rainfalls from faults with elevated 226Ra content. The variation of 222Rn concentration in the gallery has been calculated from the rainfall data from June, 1977 to December, 1979. Sometimes remarkable disagreements between the observed and calculated values of the 222Rn concentration are seen before and after the occurrence of nearby earthquakes. Such a disagreement might be a precursor of nearby earthquake. The concentration of 222Rn is also influenced by the changes in atomospheric pressure; it increases as the pressure drops and decreases as the pressure rises. Seasonal variations are recognized, too. Continuous observation of 222Rn has also been started in June, 1980 at Kikugawa Crustal Movement Observational Station (Shizuoka Prefecture, central Japan).