阳江天然高本底辐射地区空气中氡、及其子体致居民的剂量估算

Estimation of Doses to the Residents Arising from Inhalation of Rn-222,Rn-220 and Their Decay Products in High Background Radiation Area of Yangjiang.

目的 为了估算阳江天然高本底辐射地区空气中氡、及其衰变子体所致居民的平均年有效剂量和某些人体组织或器官的吸收剂量。方法 采用瞬间采样法 ,同时测量阳江天然高本底辐射地区 (HBRA)和相邻的正常本底对照地区 (CA)空气中氡、及其衰变子体浓度 ,计算出调查地区的氡平衡因子F和平衡当量浓度。根据调查地区空气中累积测量氡 ,浓度 ;氡平衡因子F和平衡当量浓度 ;人员的居留因子 ,估算了居民的平均年有效剂量和某些人体组织或器官的吸收剂量。结果 HBRA室内、外空气中氡浓度分别是 49 61Bq·m- 3 和 1 7 30Bq·m- 3 ,CA是 1 8 1Bq·m- 3 和 1 1 7Bq·m- 3 ;HBRA室内、外浓度分别是 95 1 6Bq·m 3 和 9 3Bq·m- 3 ,CA是 1 2 4Bq·m- 3 和 8 1Bq·m- 3 。HBRA室内、外氡的平衡因子F分别是 0 46和 0 53 ,CA分别是 0 62和 0 63。HBRA室内、外空气中平衡当量浓度分别是 6 51Bq·m- 3 和 0 79Bq·m- 3 ,CA室内、外分别是 0 66Bq·m- 3 和 0 33Bq·m- 3 。结论 氡、及其衰变子体所致HBRA和CA居民的平均有效剂量分别是 3 2 8mSv·a- 1 和 1 0 3mSv·a- 1 。HBRA的居民支气管上皮组织和肺的吸收剂量分别为 5 40mGy·a- 1 和 1 0 8mGy·a- 1 ,它们的吸收剂量分别约是CA的 4倍。

Objective This paper reports on the estimate of average annual effective dose of the residents and absorbed dose in some human tissues and organs arising from inhalation of Rn-222,Rn-220 and their decay products in investigated areas.Methods In order to calculate equilibrium factor F for Rn-222 and equilibrium equivalent concentration of Rn-220,we measure concentration of Rn-222 and Rn-220 by discrete sampling.Meanwhile,we measure the concentration of decay products of Rn-222 and Rn-220.Based on the equilibrium factor F of Rn-222 and equilibrium equivalent concentration of Rn-220,and the occupancy factor,writer estimated average annual effective doses and absorbed doses in some tissues and organs to the residents arising from inhalation of Rn-222,Rn-220 and their decay products in investigated areas.Results The data based upon the results of integrated measurements on the concentration of Rn-222 and Rn-220 in investigated areas.The average indoor and outdoor concentrations of Rn-222 are 49 61 Bq·m -3and 17.30 Bq·m -3in HBRA,respectively,and 18.1 and 11.7 Bq·m -3in CA,respectively.The average indoor and outdoor concentrations of Rn-220 are 95.16 Bq·m -3and 9.3 Bq·m -3in HBRA,respectively,and 12.4 and 8.1 Bq·m -3 in CA,respectively.The averages of equilibrium factors of Rn-222 for indoors and outdoors in HBRA are 0.46 and 0.53,respectively.The values in CA are 0.62 for indoors and 0.63 for outdoors,respectively.The value of equilibrium equivalent concentration of Rn-220 for indoors and outdoors in HBRA are 6.51 Bq·m -3 and 0.79 Bq·m -3,respectively,and the values for CA are 0.66 Bq·m -3 and 0.33 Bq·m -3,respectively.Conclusion The estimate of average annual effective dose to the residents arising from inhalation of Rn-222,Rn-220 and their decay products was 3.28 mSv·a -1 in HBRA,while that in CA was 1.03 mSv·a -1.The trachea-bronchial tree has the maximum absorbed dose in HBRA,the value is 5.40 mGy·a -1;lung has the second absorbed dose,the value is 1.08 mGy·a -1.These two values are about 4.0 times in CA.The estimate of average annual effective dose to the residents arising from inhalation of Rn-220 and its decay products was 1.75 mSv·a -1in HBRA.We noted that Rn-220 and its decay products are very important component of effective dose for the inhabitants living in the HBRA.