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@#<b>Objective</b> To investigate the indoor radon concentration and its changing trend in northeastern China. <b>Methods</b> We measured indoor radon levels cumulatively for over three months by solid state nuclear track detection in a total of 261 houses in multi-story or high-rise buildings in Shenyang, Changchun, Harbin, Heihe, and Yichun in northeastern China. The measurement lasted one year in Changchun for seasonal changes. <b>Results</b> The average indoor radon concentration in the five cities was 88 Bq/m<sup>3</sup>, ranging from 12 to 558 Bq/m<sup>3</sup>. The indoor radon concentrations were ≤ 100 Bq/m<sup>3</sup> in 75.1% of the houses, and ≤ 300 Bq/m<sup>3</sup> in 97.7% of the houses. The indoor radon concentration increased with the age of buildings. The indoor radon concentration was highest in winter, and it was higher in summer than in autumn and spring. <b>Conclusion</b> The indoor radon concentration in northeastern China increased compared with the data of 1980s and 1990s. It is highest in the winter heating season, and higher in summer than in spring and autumn. Indoor radon exposure deserves attention.
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Objective:To obtain the distribution characteristics of radon levels in drinking water in cities of China and analysis their influencing factors.Methods:A total of 31 cities were selected and 406 tap water samples were collected in accordance with the sampling plan based on administrative division. Radon concentrations in the water samples were determined by using RAD7 H 2O measuring devices, and the closed loop liquid-gas balance method and grab method . The radon concentrations in the gas loop were measured by using semiconductor detector. After four measurement periods, radon concentrations in water were calculated. Results:The arithmetic mean of radon concentrations in drinking water from 31 cities was (4.92±9.44) Bq/L and the geometric mean (0.71±7.77) Bq/L, ranging from less than the lower detection limit (LLD) to 43.15 Bq/L. For 84.2% of drinking water samples, radon concentrations were less than US EPA recommended 11.1 Bq/L, all lower than the EU-recommended value of 100 Bq/L.Conclusions:The radon concentrations in drinking water are higher in northeastern, northwestern, southwestern, northern China than those in southern, central China and eastern China. The factors influencing radon concentrations in drinking water are closely related to geological structure and water source type. Compared with the global values, the radon concentrations in drinking water in our cities are low and safe in general in China.
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Objective To explore the source and control of radon in high radon houses in geothermal fields; Methods Radon concentration in indoor and soil was measured by ATD detector in winter and summer; radionuclides in building materials were measured by gamma-ray spectrometry; radionuclides dose rates of building materials were measured by 6150 A D/ 6H X-γ ray detector; and radon reduction technology was applied to one of the houses;Results The average radon concentrations in 32 rooms were （106.4 ± 63.7） Bq/m3 (summer) and （421.3 ± 138.2） Bq/m3 (winter), and the concentrations in 12.5% (summer) and 96.9% (winter) of the rooms exceed 150 Bq/m3. The average radon concentration in soil around buildings was 12890 Bq/m3 (n = 24), which is 1.7 times of the typical soil radon concentration in Beijing (7600 Bq/m3). After soil decompression, the radon concentration in the house could be reduced to less than 100 Bq/m3. The radon reduction rates of active decompression and passive decompression were 94.6% and 71.4%, respectively. Conclusion The effect of soil decompression on reducing radon concentration in the bottom rooms is obvious. Attention should be paid to the radon in residential environment of geothermal field.
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Objective To establish a simple and convenient method and study the feasibility of using gold nanoparticle composites (ssDNA-AuNPs) for colorimetric detection of gamma radiation.Methods The composites ssDNA-AuNPs were prepared by applying the ssDNA to the surface of AuNPs,and then were irradiated with gamma ray with absorbed doses of 0,5,10,20,and 30 Gy,respectively.Subsequently the color change in the solutions were observed simultaneously with absorption spectra being measured.The linear relationship between the ratio of A625/A521 in the absorption spectrum and the absorbed dose was established.Results With the increase of radiation dose,the color of the solutions changed from wine-red to blue-violet gradually,the ratio of A625/A521 in absorption spectra had excellent liner response for absorbed dose ranging from 0 to 30 Gy,and the linear equation was A625/A521 =0.020 6 + 0.303 6 E(R2 =0.991 5).Conclusions The ssDNA-AuNPs synthesized in this experiment can be successfully used for colorimetric detection of gamma absorbed dose,and a simple and convenient method for detection of gamma radiation has been newly established.
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Objective To increase the cumulative measurement level of 222 Rn and 220 Rn and ensure the accuracy and reliability of the measurement result . Methods By using improved 222 Rn-220 Rn discriminative detectors ( LD-P detectors) , the radon research group of National Institute for Radiological Protection Chinese Center for Disease Control and Prevention participated with the intercomparison organized by National Institute of Radiological Science ( NIRS) , Japan. Specifically, with the 222 Rn-220 Rn discriminative detectors being sent to Japan, the comparison was completed under different conditions in the 222 Rn chamber and 220 Rn chamber in NIRS. After exposure, the detectors were sent back to our laboratory for etching and analysis, and then measurement result were informed to NIRS. Finally, NIRS returned the exposure reference values of 222 Rn and 220 Rn to our laboratory. Results Under the conditions of high and low levels of 222 Rn, the relative percentage differences ( RPD ) between the measured values and the reference value provided by the NIRS were -12. 0％ and -11. 8％, respectively, while coefficients of variation ( COV) were 3. 0％ and 6. 2％, respectively. Under the conditions of high level and low levels of 220Rn, the relative percentage differences (RPD) between the measured value and the reference value provided by the NIRS were -0. 8％ and -8. 0％, respectively; coefficients of variation ( COV ) were 6. 7％ and 4. 5％, respectively. Conclusions This intercomparison result were categorized by NIRS ( PRD<10％) , with the satisfactory result of LD-P detectors available.
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Objective To investigate the relationship between indoor radon concentration and air exchange rate for new residential building.Methods The indoor radon concentration and air exchange rate were measured in two new roughcast houses in Guangzhou and Hefei,respectively.The radon concentration was measured using radon instrument.The air exchange rate was measured by using tracer gas dilution method.Results The indoor radon concentrations measured in Guanzhou for two bedrooms in a 48-hour closed condition were 106 and 115 Bq/m3,the range of 17-181 and 6-224 Bq/m3.Air exchange rates were 0.16/h and 0.21/h.In Hefei,the twice measured values for one bedroom were 148 and 186 Bq/m3,the range of 8-224 and 14-290 Bq/m3,and air exchange rates were 0.14/h and 0.12/h.The indoor radon concentration exponentially decreased with the increase of air exchange rates.Conclusions Attention should be paid to the indoor radon pollution issue that may arise in new residential buildings of energy-saving design due to low air exchange rate.
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Objective To investigate the levels and distribution of radon concentrations in groundwater in some representative cities in China,and estimate the effective dose from inhaled radon released from domestic groundwater.Methods A total of 12 cities in 7 provinces (municipalities) were selected,including Beijing,Inner Mongolia,Ningxia,Shaanxi,Henan,Liaoning and Heilongjiang.In total,73 water samples from groundwater supply were taken.Radon concentrations in water samples were determined by using a continuous radon monitor with air-water exchanger.Results The average radon content in groundwater for drinking was 11.8 Bq/L in 12 cities in 7 provinces,ranging from 1.0 to 63.8 Bq/L.The radon concentrations in 37％ water samples exceeded 1 1.1 Bq/L,the safe limit recommended for drinking water by the United States Environmental Protection Agency (EPA).The radon contents in all of the water samples was lower than the reference level 100 Bq/L recommended by World Health Organization (WHO).The average annual effective dose arising from inhaled radon released from groundwater was 29 μSv (2.4 to 160 μSv).Conclusions Generally,the effective dose from inhaled radon released from groundwater is negligibly low.However,in some areas dominated by granite bedrock,the dose contribution from radon released from groundwater to residents should be routinely monitored.
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Objective To investigate the levels and distribution of radon in dwellings in Shenzhen cities of China.Methods A total of 108 low-,multi-,middle-and high-rise buildings were selected.Indoor radon concentrations were measured by using solid track detector.Results The arithmetic mean of indoor radon concentrations in Shenzhen was 64 Bq/m3,and geometric mean was 58 Bq/m3,in range of 15 to 155 Bq/m3.The average indoor radon concentration in Bao'an district was 50 Bq/m3 with the lowest value,and that in Pingshan new district was 87 Bq/m3 with the highest value.There were 12 measuring points where indoor radon concentrations were higher than 100 Bq/m3 in Shenzhen,accounting for 11.1％ of the total number.Shapiro-Wilk test showed that the frequency distribution of indoor radon concentration in Shenzhen follows lognormal distribution (P ＞ 0.05).The indoor radon concentrations showed a downward trend from 1990 to 2015.The indoor radon concentration decreases with the elevated floors except 10th and above floors.Conclusions The indoor radon concentrations in Shenzhen increased by 35％,compared to the previous investigations.It is recommended that efforts continue to improve radioactive materials standards about building material and to enhance the natural ventilation in high-rise buildings in order to lower the radiation hazards from radon.
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Objective To explore the effect of radon released from water on the indoor radon activity concentration in groundwater supplies.Methods Two groundwater supplies in a city were chosen.Radon concentrations in three kinds of water samples were determined by using a continuous radon monitor with air-water exchanger,including source water,finished water and tap water.The solid track detector was used to analyze the indoor radon concentration in water supplies.Results The concentrations of radon in source water,finished water and tap water were (7.59 ± 1.36),(3.56 ±0.86),(3.68 ±0.81)Bq/L and (12.19 ±0.57),(7.87 ± 1.12),(9.50 t 1.12) Bq/L,respectively.The concentration of radon was the highest in source water and at less varying level in finished water and tap water.Aeration and filtration tank process significantly decreased radon activity in water.Radon concentrations in aeration and filtration rooms were 4 218 Bq/m3 and 1 937 Bq/m3,respectively,which exceeded the limit in work place (1 000 Bq/m3).Conclusions Aeration and filtration workplaces for groundwater supplies were found to contain elevated radon concentrations in air,which was released from groundwater.Radon issues in groundwater supplies in China should be paid more attention.
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Objective To guarantee the quality of measurenents with the radon-thoron discriminative detectors of our laboratory.Methods LD-P radon-thoron discriminative detector participated in the international intercomparison for integrating radon/thoron detectors organized by National Institute of Radiological Science (NIRS,Japan).Detectors were sent to NIRS for exposure.Radon intercomparison was conducted with radon chamber providing three levels of exposure:low,medium and high levels.Thoron intercomparison was carried out at thoron chamber,which also provided three levels of exposure:low,medium and high levels.Detectors were posted back to our laboratory for etching and analysis after exposure.Then the measured values were submitted to NIRS.Finally the reference values were informed of us.Results The relative percent difference (RPD) between the measured value and the reference value for radon was-13.8％,-14.4％ and-17.1％ at low,medium and high levels respectively,and that of thoron were-14.4％,8.9％ and-3.2％ at three levels respectively.Conclusions Both radon and thoron measurement of our detectors rank asCategory Ⅰ in the 4th international intercomparisons for integrating radon/thoron detectors with the NIRS radon/thoron chambers.
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Objective To investigate the radiation level around Jiangzha hot spring,and to analyze the sources of pollution.Methods The radon and its progeny concentration,γ dose rate in hot spring living district and surrounding area were measured with ATD monitors,radon and WL continuous measurement devices,γ dose rate meter.Results The radon concentration in water was 23 -764 Bq/L.Radon concentration indoors,outdoor and in bathing place were 254 -876 799,688 -709 and 3590-15 299 Bq/m3,respectively.γ dose rate were 205 -28718 nGy/h indoor,4104- 18254 n Gy/h outdoors.Conclusions Jiangzha hot spring is an area with rare high radon and high nature radiation.Its radiation level and health effects are worthy for further attention.
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Objective To study the seasonal variation of indoor 222Rn and 220Rn concentrations in Longdong district,Gansu Province.Methods A total of 44 houses from 5 different types of raw soil architectures and 5 ordinary brick houses from a typical area were selected in Longdong district,Gansu Province in China.The LD-P discriminative 222Rn and 220Rn detectors were used to measure the indoor concentrations of 222Rn and 220Rn during four seasons in one year.Results The indoor concentrations of 222Rn showed a significant seasonal variation,which varied with different types of houses.222Rn concentrations of ordinary brick houses,soil brick houses and the cave dwellings were higher in winter and autumn and lower in summer.The average concentrations of 222Rn were 55.3-90.3 Bq/m3 in winter,36.4-65.7 Bq/m3 in spring,35.6-63.9 Bq/m3 in summer,and 60.7-87.2 Bq/m3 in autumn.For cave dwellings,open-cut cave dwellings and the underground cave dwellings,222Rn concentrations were higher in summer and autumn,and lower in winter and spring.The average concentrations of 222Rn ranged from 139-184 Bq/m3 in winter,135-199 Bq/m3 in spring,179-252 Bq/m3 in summer,172-242 Bq/m3 in autumn.The seasonal variation of indoor 220Rn was basically consistent in six types of houses,and lower in winter and spring and highest in autumn.The average concentrations of 220Rn ranged from 43.4-64.3 Bq/m3 in winter,60.6-537 Bq/m3 in spring,77.7-792 Bq/m3 in summer,63.2-1077 Bq/m3 in autumn.The indoor concentrations of 222Rn and 220Rn were different among different types of houses,and they were generally higher in type of raw soft architectures than in that of ordinary brick houses.Conclusions 222Rn concentrations indoors showed a significant seasonal variation and varied with different types of houses.
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Objective To investigate the concentrations of indoor radon (222Rn) and its daughter products as well as indoor thoron (220Rn) in selected houses in Yuhang district and Sanmen county,Zhejiang province,and estimate their annual effective doses to the population.Methods Solid state nuclear track detectors were used in selected dwellings in Yuhang district and Sanmen county,and the detectors were placed in bedrooms or living rooms.Without changing the ventilation habits of residents,These detectors were continuously placed from March to September in 2009.Results Indoor 222 Rn and 220Rn concentrations in low-rise buildings were the highest among all types of houses.The indoor concentration of 222 Rn had no relation with the building age (F = 0.53,P ＞ 0.05),but that of 220 Rn was dependent on the building age (F = 3.56,P ＜ 0.05).Moreover,the investigation demonstrated indoor 220 Rn concentrations in houses with no decoration were higher than in the houses decorated (t = 2.33,P ＜0.05).The average indoor concentrations of 222Rn and 220Rn in Yuhang district were 32.5 Bq/m3 and 314.3 Bq/m3,respectively,and the annual effective doses were 0.88 mSy and 0.42 mSv respectively.The average indoor concentrations of 222Rn and 220Rn in Sanmen county were 26.8 Bq/m3 and 399.5 Bq/m3,and the annual effective doses were 0.72 mSy and 0.53 mSv respectively.Conclusion The concentrations of indoor 222 Rn in some areas of Zhejiang province are at natural background level,and the concentrations of indoor 220Rn in rural areas are relatively higher.The total annual effective dose from 220Rn and its progeny was larger than that from 222Rn and its progeny by 50 percents.