青岛市区辐射环境质量评价

IOCAS-IR > 海洋环流与波动重点实验室

	青岛市区辐射环境质量评价
其他题名	Assessment of radioactivity environment in Qingdao area
	曲丽梅
学位类型	博士
	2006-06-16
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	天然放射性核素辐射环境外照射内照射青岛市区
摘要	安全环境是人类赖以生存的基础，天然放射性辐射环境是人类生存环境的重要组成部分，放射性物质存在于各类物质中，包括空气、水源和土壤等。放射性物质的辐射对环境的影响往往被人们所忽视，但又是最危险的环境影响因素。为了生存和健康不仅需要了解重金属和有机物污染，而且需要了解辐射污染。天然放射性辐射环境与该区域内的地质环境密切相关。青岛地区燕山期岩浆活动频繁，形成了以钾长花岗岩和二长花岗岩为主的大规模侵入岩体，大多数母岩为富含铀、钍的花岗岩。本论文选择青岛地区做为放射性的研究区，该花岗岩地区与放射性核素的辐射强度的关系具有典型的代表性。论文在大量密集测量地表岩石、土壤γ总量、土壤中238U、232Th 、40K放射性核素的含量基础上，分析了天然放射性辐射环境与该区域内的地质环境. 分析了环境中氡的来源及迁移机制，给出了氡的运移理论模型，指出了环境中氡的危害及其土壤中的分布与地质环境的关系。分别从内照射和外照射的角度，将土壤中238U (226Ra) 、232Th 、40K放射性核素的比活度、γ能量谱、环境中的氡浓度和直接测量空气中的吸收剂量率相结合，首次对青岛地区的辐射环境进行了研究和评价，可为奥运和青岛市长远发展提供科学保障。结果表明研究区内土壤中的238U含量低于全国及世界平均值，土壤中232Th含量分别是全国和世界均值含量的1.1和1.5倍, 土壤中40K含量分别是全国和世界均值含量的2.43和2.44倍，因此空气中的吸收剂量率高于全国（81.5nGy•h-1）和世界（80 nGy•h-1）约1.2倍。通过能谱估算的空气吸收剂量率与实际测量值近似相等。研究区的年有效剂量为0.83 mSv，低于世界平均年有效外部照射的剂量限值1.0mSv，外照射指数和内照射指数均小于1，该区的等效镭浓度Raeq均值为197 Bq•kg-1，低于建议最大容许值370 Bq•kg-1，基于以上的各类指标均在世界均值或容许值范围内，可以认为该区的外照射水平属于安全辐射范畴。 222Rn浓度对人体内部照射具有举足轻重的地位，也是评价辐射环境质量的关键所在。本文采用经典的氡在空气中的扩散和对流的理论模式，通过研究区内的土壤中铀的含量推算出离地面1米高的空气中的氡的浓度，并且分析了土壤中的氡浓度与土壤中的放射性核素U、Th、K的含量的关系。研究区的土壤氡浓度总体平均值为5887Bq/m3，与全球土壤氡浓度的平均值7400 Bq/m3相比属于土壤氡浓度正常地区。由于青岛市区土壤覆盖层很薄,地表储气条件较差，造成土壤氡逸散。因此除区内土壤氡浓度几处偏高区以的其他区域，甚至断裂带上他和其他区域的土壤氡浓度也普遍偏低。通过计算可以得出青岛市区大气中氡浓度所导致的居民室外吸入氡子体所产生的年均人有效剂量估算结果是0.94mSv/a。这与联合国辐射防护委员会公布世界平均本底值1.2mSv/a相比,此值在正常范围内。这个地区虽然大面积出露富含放射性物质的花岗岩，由花岗岩风化形成的土壤中放射性核素含量（钍、钾）也较高，但是因为铀含量不高，另外本区临海，一年四季的风速较大，因此本地区室外和室内空气中氡浓度不高。综上可以得出结论：本区的辐射环境属于安全区域，适于人类生活。本论文研究成果和创新点有：首次在大量密集测量的基础上，系统地对青岛地区的辐射环境进行了研究和评价；在数据采集方面，采用直接就地测量，跟其他调查方法比，采样密度大，数据量大。从研究方法方面，本文从外照射和内照射的角度，采用了多指标相结合的综合方式来评价本区的辐射环境质量，详实可信；引入GIS技术，和放射性评价相结合，较为系统深入地探讨了放射性核素和氡浓度的分布特征及其与岩性的关系。
其他摘要	Human being lives depend on safe environment. The natural radioactivity environment is one important part of human living surroundings. The natural radioactivity lies in all the matters surrounding human beings such as air, water and soil.The impact of radioactivity material on environment is the most dangerous although it is usually ignored. For living and health, man need to know the pollution not only from heavy metal and organic materials, but also from radioactivity. There is close relationship between the radioactivity and the area’s geology in environment. In Qingdao area, because of the impact of the active magma during Yanshan period, invasive rock body was cosmically formed. Most of mother rocks are granites containing uranium and thorium. In this dissertation we chose Qingdao as radioactivity research area, where the relationship is typical between the granite and the radiation intensity in interest area. On basis of extensive measurement of surface rocks, γ total dose in soil, radioactivity concentration of nuclide 238U、232Th 、40K, we analyze their radioactivity feature and distribution, as well as the geological environment in the area. We analyzed the resource of Rn in environment, as well as the transportation mechanics of Rn. The transportation model of Rn was introduced. Hazard of Rn in environment was stressed. The relationship between distribution of Rn and geological environment was analyzed. Based on outer and inner radiation, many factors were integrated to systematically assess the radiation environment in Qingdao for the first time. These factors involve the specility content of 238U (226Ra) 、232Th 、40 K in soil, the terrene gamma radiation absorbed air dose, annual effective dose, external irradiation index, inner irradiation index and equal radium index. The result can provide references for Olympic games and long-term development of Qingdao. The results show that the content of 238U is under the average of the country and the world. The concentration of 232Th is 1.1 times of the nation and 1.5 times of the world. And the concentration of 40K is 2.43 times of the nation and 2.44 times of the world. The absorbed air dose estimated from the gamma spectrometer is close to the measured value. The annual effective dose in the area is 0.83 mSv, under 1.0mSv of world average. The external irradiation index and inner irradiation index are both less than 1. And the mean equal radium index is 197 Bq•kg-1,under suggested allowance value of 370Bq•kg-1. We conclude the study area is safe because all the indexes are under the allowed value. 222Rn is very important for interior irradiation and it is the key indicator for assessment of environment radioactivity. Based on the classical diffuse and convection model, the radon above 1m over ground was estimated by the concentration of uranium in soil. Relationship between the radionuclide in soil and the radon was also analyzed. There was no significant relationship between radon in soil and the radionuclide. The area is normal because the average radon in soil(5887Bq/m3) is under 7400 Bq/m3 of the world. The thin coverage of soil and the bad condition of gas storage may result in the escape of the radon in soil. Excluding several special higher area, generally the radon concentration in this area including the rapture is normal. The average annual effective dose of radon above 1m over ground is 0.94mSv/a in the study area, so it is safe compared with the publicized average 1.2mSv/a by UNSCEAR. Granite with abundant radionuclide occupies study area. The concentration of potassium and thorium in soil are relatively higher, while the uranium concentration is not high. The wind all the year round is strong for the impact of sea. Neither of the radon outside and inside room is high. In conclusion, the study area of Qingdao is safe in radioactivity and suitable for living. There are several innovations in this dissertation. Radioactivity environment in Qingdao was systemically assessed for the first time; In data collection, we adopted more representative direct ground measurement on the spot, which can get huge dataset compared with other methods. On basis of outer and inner radiation, many factors, instead of single one or two, were used to assess the radiation environment. These factors involve the specility content of 238U (226Ra) 、232Th 、40 K in soil, the terrene gamma radiation absorbed air dose, annual effective dose, external irradiation index, inner irradiation index and equal radium index. So the result is more convincing. In addition, GIS was utilizted to reveal the spatial feature. As a result, the relationship of nuclides and Rn distribution and rock attribute were deeply analyzed.
页数	104
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/899
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	曲丽梅. 青岛市区辐射环境质量评价[D]. 海洋研究所. 中国科学院海洋研究所,2006.

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