Nationwide survey and behavior of tritium in air in China

为了为分析东亚地区大气氚的区域尺度行为提供数据，在中国开展了全国范围的水蒸气氚调查。除了常用的利用动力的主动方法外，还采用了一种新开发的无泵的被动方法来进行分子筛水蒸气取样。在中国北京公共卫生部工业卫生实验室建造并安装了一套从吸收蒸汽中提取水分的装置。在实验室进行了萃取水样的蒸馏和液体闪烁计数器对氚放射性的测量。1992年6月至1993年8月，在中国13个城市和日本5个城市（札幌、仙台、名古屋、熊本、那雄）每2个月进行一次被动法水汽采样。测量结果如下：1)每两个月获得东亚地区水汽中氚的区域分布。还得到了年平均值的分布。2)乌鲁木齐市和兰州市的年平均浓度最高，约为15 Bq/l。下一个高组（8- 11bq /l）包括哈尔滨、长春、北京、西安、拉萨和武昌，陈图紧随其后。沿海地区（杭州、福州、新森）浓度较低，日本有5个点属于最低水平组（1 ~ 2 Bq/l）。3)从区域分布图上可以看出内陆效应和纬度效应。过去核爆炸试验的效果有待进一步研究。北京、兰州和福州在每个季节采用主动采样法每两天采样一次，连续10天。利用两层轨迹模型对部分数据进行分析，得到了较好的浓度计算值与实测值吻合。

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.