| Radon is an unique,colorless,tasteless,odorless radioactive inert gas produced by the decaying of radium in nature. Researches by scientists have confirmed that inhaling of radon and its daughter products can cause lung cancer when they are presented in enhanced levels at lungs. Therefore, the high concentration of radon in the environment has been identified as one of the important causes of disease to cause lung cancer. Radon is considered 1 of 19 carcinogenic substances to human being by World Health Organization. It is also 1of 5 indoor pollutants, impacting on human health, which are formally controlled in China Radon pollution has been paid more and more attention by many countries. The subject of this thesis is from the project "research of radon radiation field and environmental effects at air-ground interface"(project number:40374051) surpported by national natural science foundation,and also the research results of "survey and evaluation of the radon concentration in the main districts of Chongqing City",which is the technical service project from Chongqing supervision and management center of radiation environment.The Chongqing city is located in the southwest of China, covering an area of 82 400 km2, which is supported by the main urban districts and the other counties liking a myriad of stars surrounding the moon, constituting a combined and network modern city group of the organic combination of the large, medium and small cities. Currently, Chongqing city is the largest city in China with the largest administrative area, the largest population and the most management units. This investigation is to grasp the distribution of indoor and outdoor radon concentration in the main districts of Chongqing City(Yu Zhong District,Jiang Bei District , Ba Nan district , Nan An District , Sha Pingba District , Yu Bei District , Jiu Longpo District , Da Dukou District , Beibei district), covering a completed regional area of 631 km2 or so. Then we can obtain the overall basic data of radon concentration to make up the blank of the distribution of radon concentration in Chongqing and provide scientific basis for carrying out radioactive environmental assessment of urban development, government decision-making, and establishing a good environment to live, dwell, work and study. To turn Chongqing into a developed, harmonious and livable city, we must reduce the harm, made by radon, to people by making effective measures to reduce radon concentration for the high radon concentration buildings.In the study we have measured the indoor and outdoor ambient air radon concentration in the main city of Chongqing with about 631 km2 completed regional area by pulse ionization chamber using RAD7 radonα-spectrometry detector from U.S. Durridge and method of nuclear solid track record using the BR-G2000 automatic nuclear solid track measuring system and CR-39 track pieces from Beijing Expo Special Science and Technology Co., Ltd.. According to mandate and technical requirements, we set 10 sampling points to monitor outdoor air radon concentration. It should be measured for 48 hours at the parallel sampling point, 24 hours at the other points. To measure the indoor air radon concentration we set the sampling points by means of different density distribution method based on mesh distribution according to the tour-style building features of Chongqing city. The indoor air radon concentration in the measured areas was performed by 2×2 km2 grid distribution, with a measuring point in the center of each grid, making sure to set the sampling points within 4 km2. We laid out 210 pieces of track piece, including 189 pieces of point position samples, 21 pieces of parallel samples; We were recycled 187 pieces of track piece, including 168 pieces of point position samples, 19 pieces of parallel samples; the total recovery rate was 89.0%, parallel samples occupies the 10.2% of the the total recovery samples, and accounts for 12.3% of the point position samples,which included bedroom, office, underground construction.Through measuring the radon concentration in the indoor and outdoor air in the main city of Chongqing and laboratory analysis, we have obtained the radon concentration from 10 outside sampling points by 24 hours continuously monitoring and the cumulative radon concentration data from indoor sampling points by 70 days continuous measurement. Results after analyzed and evaluated showed that the average air radon concentration standard is lower in the main districts of Chongqing City, the outdoor average is 14.9Bq·m-3 and historical data unchanged; the indoor average is 64.5 Bq·m-3, which are both below the national standard. (1) The air radon concentration at 10 outdoor sampling points are in the range of 0 ~ 58.1 Bq·m-3 in the main districts of Chongqing City. The average value of air radon concentration outdoor is 14.9Bq·m-3. The radon concentration values outdoor in Jiang Bei District,Sha Pingba District and Da Dukou District are slightly higher than the other six districts. They are respectively 21.4Bq·m-3,22.3Bq·m-3 and 23.0Bq·m-3.(2) The measuring value of air radon concentration outdoor in the main districts of Chongqing City is just above 1-2Bq·m-3 compared with the domestic and foreign historical monitoring data.(3) The outdoor air radon concentration is basically coincident with total change trend. From the whole aspect, radon concentration in the morning is slightly higher than that in the afternoon.(4) The empirical frequency distribution of the air radon concentration indoor in the main districts of Chongqing City is normal distribution.(5) The average value of air radon concentration indoor is 64.5 Bq·m-3 in the main districts of Chongqing City. There are only 3 house radon concentration exceed the standard in the totally 168 houses investigated. Two houses are in Beibei District and one is in Jiulongpo District, just accounted 1.8% on the all monitoring points. After surveying we found that this three sampling indoors are storage rooms or unused houses with poor ventilation condition.(6) The overall average values of air radon concentration indoor were quite low in the main districts and all counties of Chongqing City. They were all lower than the action level of radon indoor provided by the national standards. Among them the maximum was 75.1 Bq·m-3and the minimum is 35 Bq·m-3 respectively in Bei Bei District and Ba Nan District.(7) According to different factors we discussed the average values of air radon concentration indoor. They were sorted as follows: According to different times the order of the average air radon concentration levels indoor is the early of 21th Centuryhollow brick; According to different building positions the order of air radon concentration level indoor is underground structure>building on the grounds; According to different building floor material the order of air radon concentration level indoor is stone floor>floor tile>cement>wood floor; According to different building function the order of air radon concentration level indoor is office> underground structure>room.(8) The annual effective dose range from the outdoor and indoor air radon and its progenies is 0.70-1.29mSv/a, which is far lower than the annual effective dose 1.30mSv/a, estimated to the public by the United Nations Scientific Committee on Effects of Atomic Radiation.
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