粉煤灰的农业利用及其环境放射性污染评价

AGRICULTURAL APPLICATION OF COAL ASH AND ITS RADIOACTIVE CONTAMINATION TO ENVIRONMENT

对北京、内蒙、宁夏、河北、广东和天津等地大型火力发电厂粉煤灰的采样分析表明：粉煤灰中主要放射性成分为２３８ Ｕ 、２３２ Ｔｈ 衰变系和４０ Ｋ ，比活度范围分别为９３２ ～２８３８ Ｂｑ／ｋｇ ，８０３ ～２３８８ Ｂｑ／ｋｇ 和１１５６ ～４４７４ Ｂｑ／ｋｇ 。试样模拟研究表明， 当粉煤灰施用量达６７５ Ｔ／ｈ ｍ ２ 时，土壤中天然放射性核素２２６ Ｒａ 和２２８ Ｒａ 的比活度分别是对照的３５６ 倍和２６０ 倍。土壤中天然放射性核素的比活度和地面１ ｍ 高处空气吸收剂量及地面γ辐射所致人均年有效剂量当量随粉煤灰的施用量增加呈现增加的趋势。土壤中２２８ Ｒａ 的比活度与粉煤灰施用量的相关性可表示为ｙ ＝ ２２０４ｘ ＋ １７２５ ，（ｒ２ ＝ ０９９０９） ；对于２２６ Ｒａ ，ｙ ＝ ２１３８ｘ ＋ ２４５ ，（ｒ２ ＝ ０９９６６） 。地面１ ｍ 高处空气吸收剂量率（ Ｄ） 与粉煤灰施用量的相关性可表示为：ｙ ＝ １８９６ｘ ＋ ３８７５ ，（ｒ２ ＝ ０９８９１ ） 。有效剂量当量（ Ｈ） 的变化与施用粉煤灰的量之间的相关性可表示为：ｙ ＝ ２３２４５ｘ ＋４７５０５ ，（ｒ２ ＝ ０９８９１） 。

Sampling from the electric power plants of Beijing,Inner Mongolia,Ningxia,Hebei,Guangdong and Tianjin,coal ash samples were determined respectively by HPGe γ spectrometer analyzer.The results show that the main composition of radioactive substances are 238 U, 232 Th,their daughter nuclides and 40 K.The range of specific radioactivity for 238 U is 93\^2～283\^8Bq/kg,for 232 Th, 80\^3～238\^8Bq/kg and for 40 K, 115\^6～447\^4Bq/kg.When amount of the coal ash applied is up to 675t/hm\+2 the specific radioactivity of 226 Ra and 228 Ra are 3\^56 and 2\^60 times higher than those of control respectiviely.The increase of natural specific activity in soil varies with the amount of the coal ash applied,the expression of coefficient curve for 228 Ra is y=22\^04x+17\^25(r\+2=0\^9909) and for 226 Ra, y=21\^38x+2\^45(r\+2=0 9966).The same trend is shown with absorbed dose in air (D) and the annual effective dose(H),for D, y=1\^896x+3\^875(r\+2=0\^9891) and for H, y=23\^245x+47\^505(r\+2=0 9891).\;