关键词: 天然放射性, γ剂量率, 氡, 气土, 年有效剂量

Abstract: This environmental survey for natural radioactivity in Baotou City was conducted with measurement of γ absorbed dose rates in air and with measurement of ²²²Rn, ²²⁰Rn and their progenies concentrations. The average value of γ instantaneous dose rates measured in Baotou city was 62.5 nGy/h. The mean cumulative dose rate of γ ray in air was 100.7 nGy/h, which was consistent with both the γ instantaneous dose rate after subtraction of the cumulative dose rate of cosmic rays and the aerial survey value (60 nGy/h) of Baotou City in 2006. The α potential energy concentrations of the ²²²Rn and ²²⁰Rn progenies in aerosol were 12.88 and 9.55 nJ/m³, respectively, and both of them were within the range of standard limits. The annual effective dose in Baotou City was estimated to be 0.58 mSv from external exposure and 1.29 mSv from internal exposure, which are slightly higher than the national average value and the world-wide average. The effective dose from natural radioactivity in Baotou City did not exceed the regulatory limits, and thus, would not pose a threat to public health.

Key words: natural radioactivity, gamma radiation dose rate, ²²²Rn, ²²⁰Rn, annual effective dose