六级大气颗粒物中超痕量铀钍的HR-ICP-MS分析方法研究

发布时间：2018-03-08 14:13

本文选题：大气颗粒物　切入点：天然放射性铀　出处：《中国疾病预防控制中心》2017年硕士论文　论文类型：学位论文

【摘要】：铀钍作为天然放射性元素,广泛存在于环境介质(土壤、水、空气)中,其在土壤和水中的含量分别约为μg/g和μg/L量级,钍的天然平均本底含量高于铀。目前空气中的铀钍主要有地壳、土壤扬尘等几方面来源,人类生产活动(如开采矿山和冶炼、燃煤发电等)在一定程度上也影响了空气中放射性铀钍的浓度水平。铀钍进入人体的途径主要有饮水、食物和空气等,其中吸入是最主要、最危险的途径之一。天然放射性铀钍既表现放射性毒性,又表现化学毒性,进入人体后主要滞留在骨骼、肝脏、肾脏等人体器官,可能导致造血、神经、免疫等系统病变,同时还可能诱发白血病等疾病。放射性物质被空气中的悬浮颗粒物吸附会形成放射性气溶胶,其对人体的危害程度与放射性物质的浓度水平、机体本身生理状态、气溶胶的空气动力学直径等有密切关系。国外针对大气颗粒物中铀钍总的含量开展了相关的监测与研究工作,联合国原子辐射影响科学委员会(UNSCEAR)报告了气溶胶中铀钍浓度参考值。国内针对气溶胶中天然放射性铀钍主要在铀矿等矿区周围开展相关的调查,目前未制定气溶胶中铀钍分析的标准方法和浓度限值。开展大气颗粒物中铀钍的分析方法研究,监测探讨我国气溶胶中(特别是细颗粒物中)铀钍的浓度水平,对于保护公众健康和大气污染防治具有重要的意义。本课题研究了六级大气颗粒物中超痕量铀钍的分析方法,优化实验条件,分析讨论不同粒径大气颗粒物中铀钍的浓度水平、剂量估算、污染溯源等;主要的研究内容如下:(1)六级大气颗粒物中超痕量铀钍的分析方法实验研究通过考察不同材质滤膜、酸消解体系以及质谱相关测定条件对本底和样品中铀钍含量分析的影响,确定选择本底铀钍含量较低的纤维素滤膜进行空气采样,前处理消解的方法选择HN03-HC1(王水)-H202的混合酸系,建立了微波消解-电感耦合等离子体质谱法测量六级大气颗粒物中超痕量铀钍的分析方法。通过含铀钍标准滤膜的实验验证,该方法铀钍的相对误差均在10%以下,方法精密度针对铀钍分别为3%、8%,方法检出限分别达到2×10-4ng/m3、1.3×10-3ng/m3,本方法扩展相对不确定度U铀=8%、U钍=4%,实验方法有效可靠。(2)铀钍的质量浓度水平与气象因子相关关系及分布特征研究运用建立的分析方法,对实际连续采集的气溶胶样品进行了分析讨论。通过Spearrnan非参数分析检验得出不同粒径颗粒物中超痕量铀钍的质量浓度与空气质量指数、湿度呈正相关关系;与温度、风速呈负相关关系;铀钍质量浓度在分布特征上表现为夏季低、冬季高,白天低、夜间高的趋势;铀钍集中分布在细颗粒物中,且细颗粒物受气象条件的影响比粗颗粒物大。(3)不同粒径大气颗粒物中超痕量铀钍的浓度水平研究运用建立的分析方法,对在北京市实际采集的360个气溶胶样品进行测量分析。铀在PM2.1、PM10.2、TSP的质量浓度范围分别是0.039～0.145 ng/m3、0.088～0.238 ng/m3,0.113～0.275 ng/m3;钍在 PM2.1、PM10.2、TSP 的质量浓度范围分别是 0.070～0.227ng/m3、0.166～0.461ng/m3,0.222～0.546ng/m3。天然铀-238活度浓度范围为0.291～5.007 μBq/m3,平均值2.194 μBq/m3,钍-232活度浓度范.围为 0.334～3.712 μBq/m3,平均值 1.541 μBq/m3。(4)吸入所致内照射剂量估算与含铀钍颗粒物溯源分析运用生物动力学模型和国家标准GB18871-2002提供的剂量转换系数进行待积有效剂量的估算。本次研究表明公众因吸入天然放射性铀钍引起的年待积有效剂量均值是0.345 μSv/a,范围为0.073 μSv/a～0.828 μSv/a,远远小于UNSCEAR报告给出的天然辐射源所致公众年有效剂量2.4 mSv/a。通过HYSPLIT模型对北京市2016年采样期间三次空气中铀钍浓度较高的污染过程进行了 72小时气流追踪溯源分析,境外气流方向主要来自西北部和北部方向;境内气流方向主要来自矿产丰富、人口密集的相关地区和省份。
[Abstract]:Uranium and thorium as natural radioactive elements, widely exist in the environment (soil, water, air medium), its content in soil and water were about g/g and g/L level, the average natural thorium content is higher than the bottom of uranium. Uranium and thorium in the air are the main aspects of soil crust, dust source and human activities (such as mining and smelting, coal-fired power generation etc.) to a certain extent, also affected the concentration of radioactive uranium and thorium in air. Uranium and thorium into the body of the main ways of drinking water, food and air, which is the main way of inhalation, the most dangerous is the performance of natural radioactive uranium and thorium. Radioactive toxicity and chemical toxicity, enters the human body mainly located in bone, liver, kidney and other organs of the body, may cause the blood, nerve, immune system diseases, but also may cause leukemia and other diseases. The radioactive material is in the air The suspended particles attached to the formation of absorbing radioactive aerosol concentration, its harm to the human body and the degree of radioactive substances, the body itself physiological state, there is a close relationship between the aerosol aerodynamic diameter. In foreign countries the total content of uranium and thorium in atmospheric particulates carried out monitoring and related research work, the United Nations Scientific Committee on atomic radiation effect of (UNSCEAR) report of uranium and thorium concentration reference values of aerosol. Investigation for domestic natural radioactive aerosols of uranium and thorium mainly carried out around the uranium mining related, is not currently formulating the limitation standard method and concentration of uranium and thorium in aerosols. To carry out the analysis of uranium and thorium in atmospheric particulates, monitoring of me the aerosol (especially fine particulate) concentrations of uranium and thorium, is of great significance for the protection of public health and the prevention and control of air pollution. The subject of research The analytical method of the six level in the atmospheric particles of trace uranium and thorium, optimizing the experimental conditions, discussed different concentration levels of uranium and thorium in the atmospheric particles dose estimation, pollution source; the main contents are as follows: (1) analysis of the experiments of the six super atmospheric particles of trace uranium and thorium. Through the investigation of different membrane material, acid digestion system and mass spectrometry measurement conditions on the bottom and the content of uranium and thorium in the samples, determine the choice of cellulose membrane of uranium and thorium content in the lower end of the air sampling method, digestion pretreatment HN03-HC1 (aqua regia) mixed acid system -H202, established the analysis method of measurement six super atmospheric particles of trace uranium and thorium by microwave digestion inductively coupled plasma mass spectrometry. The uranium thorium standard membrane experiment, the relative error of the method of uranium and thorium are below 10%, fine method According to the density of uranium and thorium were 3%, 8%, the detection limit reached 2 * 10-4ng/m3,1.3 * 10-3ng/m3 respectively, this method extends the relative uncertainty of U =8% U =4% uranium, thorium, experimental method is effective and reliable. (2) the quality level of concentration of uranium and thorium associated with meteorological factors and distribution characteristics of using the established method the actual, aerosol samples were continuously collected were analyzed and discussed. Through Spearrnan non parametric analysis of different diameter particles of ultra trace uranium and thorium concentration and air quality index, humidity was positively correlated with temperature, wind speed; there was a negative correlation between the concentration of uranium and thorium; distribution characteristics of low in summer in winter, high, low in daytime, nighttime high trend; uranium and thorium are concentrated in fine particles, and the effect of fine particles by meteorological conditions than coarse particle. (3) different particle size of ultra trace uranium and thorium. The concentration level of study using the established method, measurement and analysis of 360 aerosol samples collected in the city of Beijing. Uranium in PM2.1, PM10.2, the concentration of TSP was 0.039 ~ 0.145 ng/m3,0.088 ~ 0.238 ng/m3,0.113 ~ 0.275 ng/m3; in PM2.1 PM10.2, thorium, concentration of TSP were 0.070 ~ 0.227ng/m3,0.166 0.546ng/m3. ~ 0.461ng/m3,0.222 ~ -238 activity of natural uranium concentration range of 0.291 ~ 5.007 Bq/m3, average 2.194 Bq/m3, th -232 activity concentration is 0.334 ~ 3.712. Van Wai Bq/m3, the average value of 1.541 Bq/m3. (4) inhalation and containing uranium and thorium particle tracing analysis using bio kinetic model and the national standard provided by GB18871-2002 dose conversion coefficients to estimate the accumulated effective dose of radiation dose estimation. This study shows that due to the public caused by inhalation of natural radioactive thorium to uranium The mean effective dose of product is 0.345 Sv/a, a range of 0.073 Sv/a ~ 0.828 Sv/a, far less than the UNSCEAR report gives the source of natural radiation caused by the public annual effective dose of 2.4 mSv/a. by sampling the pollution process of uranium and thorium concentration three times higher in the air of Beijing city during the 2016 HYSPLIT model of the source analysis of 72 hours of air track outside the air flow direction mainly from the northwest and north direction; the airflow direction mainly from the territory rich in mineral resources, and related areas of densely populated provinces.

【学位授予单位】：中国疾病预防控制中心
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R14

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