Inf Iuonce of ~(220)Rn on ~(222)Rn measurement in Chinese cave dwellings

摘要

Alpha track detectors (ATDs) are widely used for measurement of indoor ~(222)Rn concentration. However, some results showed there were quite differences of ~(222)Rn concentration in some Chinese cave dwellings by using different kinds of ATDs. The abnormal results had caused a special attention. Further experiments found some filter membranes used with some detectors had very large air exchange rates, that means ~(220)Rn gas can also get into diffusion chamber through filter with ~(222)Rn gas together. In this way, ~(222)Rn concentration would be overestimated for the disturbance of ~(220)Rn. Since the ~(220)Rn concentrations are very high (152 ～ 296Bq m~(-3)) in some cave dwellings north west in China , its contribution should not be neglected.