Nationwide survey and behavior of tritium in air in China

为分析东亚地区大气中氚的区域尺度行为，中国在全国范围内对水汽中氚进行了调查。除通常的动力主动法外，还采用了新开发的无泵被动分子筛法采样水蒸气。在北京中国卫生部工业卫生实验室建造并安装了从吸收的水蒸气中提取水分的装置。用液体闪烁计数器对水样进行了蒸馏和氚放射性测量。1992年6月至1993年8月，在中国的13个城市和日本的5个城市(札幌市、仙台市、名古屋市、熊本市、那霸市)每两个月进行一次被动水汽采样。测量结果如下：1)东亚地区水汽中氚的区域分布是每两个月一次。并给出了年平均值的分布。2)乌鲁木齐和兰州的年平均浓度最高，约为15Bq/L。其次是哈尔滨、长春、北京、西安、拉萨、武昌，紧随其后的是成都。沿海地区(杭州、福州、新森)为低层，日本5个点属于最低层组(1-2Bq/L)。3)从区域分布图可以看出，既有内陆效应，也有纬度效应。以往核爆炸试验的效果有待以后研究。在北京、兰州和福州，每个季节每隔两天进行一次主动采样，连续十天。利用两层轨道模型对部分数据进行分析，计算得到的浓度与实测值吻合较好。

A nationwide survey of tritium in water vapor has been carried out in China for providing data used for analyzing regional scale behaviors of atmospheric tritium in East Asia.Besides the usual active method using motive power, a newly developed passive method using no pump was used for sampling water vapor with molecular sieves.An apparatus for withdrawing water from absorbed vapor was constructed and installed at Laboratory of Industrial Hygiene, Ministry of Public Health, Beijing, China. The distillation of withdrew water sample and tritium radioactivity measurement with a liquid scintillation counter have been made at the Laboratory.Sampling of water vapor by the passive method was carried out every two months from June 1992 to August 1993 at 13 cities in China and 5 cities in Japan (Sapporo, Sendai, Nagoya, Kumamoto, Naha).Results of measurement are as follows : 1) Regional distributions of tritium in water vapor in East Asia were obtained every two months. A distribution for annual mean value was also obtained. 2) At Urmuchi and Lanchow, most high annual mean concentration of about 15 Bq/l was observed. The next high group (8-11 Bq/l) includes Harbin, Chanchun, Beijing, Sian, Lhasa, and Wuchang and Chentu follows the group. Concentrations at coastal region (Hangchow, Fuzhou, Sinsen) show low level, and five points in Japan belong the most low level group (1-2 Bq/l). 3) From the regional distribution map, we can see both inland effect and latitude effect. The effect of past nuclear explosion test should be studied later.Sampling by the active method had been made every two days for ten days in each season at Beijing, Lanchow and Fuzhou. Analyzing some date by using two-layer trajectory model, we got fairly good agreement between the calculated concentration level and measured one.