New-designed in-situ measurement system for radon concentration in soil air and its application in vertical profile observation
New-designed in-situ measurement system for radon concentration in soil air and its application in vertical profile observation
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DOI：
10.1080/00223131.2021.1961638
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发表时间：
2021-08
影响因子：
1.2
通讯作者：
Hao Wang;Lei Zhang;Yunxiang Wang;Changhao Sun;Q. Guo
中科院分区：
文献类型：
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作者：
Hao Wang;Lei Zhang;Yunxiang Wang;Changhao Sun;Q. Guo
摘要 土壤中的氡是地球科学中一种有价值的放射性示踪剂，特别是对于地震和火山前兆。为了连续原位测量土壤中氡浓度，开发了一种新设计的测量系统。详细开展了湿度响应校正的标定和实验，并利用7个氡探头在不同深度进行了垂直剖面现场测量。标定结果表明，在绝对湿度32.8 g m−3条件下，1小时测量周期，氡气探头灵敏度为16.1±1.0 cph (kBq m−3)−1，检测下限为231±15 Bq m−3。现场测量结果表明，不同深度的氡浓度随时间变化，并随土壤深度的增加而增加。晴天垂直剖面呈现不同扩散长度的负指数分布，而降雨会扰乱垂直分布，导致近地表氡浓度增加。在我们的观测中，地下80厘米以上的氡浓度显得相当稳定，几乎不受降雨的影响。
ABSTRACT Radon in soil is a valuable radioactive tracer in earth science, especially for earthquake and volcanic precursors. For the purpose of continuous measurement of radon-in-soil concentration in-situ, a new-designed measurement system was developed. Calibration and experiments for humidity response correction were carried out in details, and field measurement of vertical profile with 7 radon probes at different depths was performed. Calibration results show that the sensitivity of the radon probes is 16.1 ± 1.0 cph (kBq m−3)−1, and the lower level detection limit is 231 ± 15 Bq m−3 for 1-hour measurement cycle under the absolute humidity of 32.8 g m−3. Field measurement results show that radon concentrations at different depths change with time and increase with depth in the soil. The vertical profile presents a negative exponential distribution with different diffusion length in sunny days, while rainfall can disturb the vertical distribution and lead to increase of radon concentration in the near ground surface. Radon concentration in underground deeper than 80 cm appears quite stable and hardly affected by rainfall in our observation.