���ൺ��1 500 km 2��Χ�ڴ��ܶ����������Ժ��غ͵ر�γ ���������ϵͳ�����о�����������������ֲ����ɼ���Ӱ�����ء�����������ൺ�������к���232 Th ��40 K �ķ����ԱȻ��ƫ�ߣ���238U ƫ�͡��ر�γ ���������( ƽ��ֵ91. 87 nGy /h) �Ը���ȫ��������ƽ��ֵ���о����֣��ر� 93. 14%��γ �������Ե�������Ժ���238U��232 Th ��40K ��γ ���䣬����232 Th ��40K �Ĺ���ռ81. 21%������Ҫ�Ĺ����ߡ����ʱ�����������γ ���������ֵ����ɽ�ڸ��໨�����ǵ����ൺ����—����ׯһ��γ ���������ƫ�ߵ���Ҫԭ��; ͬʱ��������( ·����ϡ���ò����) ���������Ҳ����һ��Ӱ�졣��Ȼ�о�����γ ��������ʽϸߣ���������Ч����( 0. 56 mSv) ���ڹ������������������ֵ ( 1. 0 mSv) ���˾ӻ�����������Ӱ�졣

Based on a large density measurements of soil including radionuclides and surface gamma radiation within 1 500 km2 in Qingdao City��a systematic in-depth study of its radioactive characteristics��distribution and influencing factors were conducted�� The results revealed that the radioactive of nuclides232Th and 40 K in soils of Qingdao City were with higher specific activity��while 238U was low�� Surface gamma radiation dose rate ( 91. 87 nGy /h) was slightly higher than the national and world wide mean values�� The study found that 93. 14% of the surface gamma radiation comes from radionuclides 238U��232Th and 40K��in which the 232Th and 40K were the main radioactive elements accounted for 81. 21% of the contribution�� The geological background was the main factor which effected the gamma radiation dose rate of the surface soil��like the high gamma radiation from Qingdao to Wanggezhuang area could be mainly attributed to the various types of granite and fault structure of Yanshannian��in the meantime�� environmental factors ( paving��landscape��etc�� ) contributed the gamma radiation dose rate in a certain level�� Although the gamma radiation dose rate in the studied area is higher��the annual effective dose ( 0. 56 mSv) is far below the public exposure dose limits 1. 0 mSv��which is basically not harmful for the living environment��