Abstract
The naturally occurring primordial radionuclides in coals might exhibit high radioactivity, and can be exported to the surrounding environment during coal combustion. In this study, nine coal samples were collected from eastern Yunnan coal deposits, China, aiming at characterizing the overall radioactivity of some typical nuclides (i.e., 40K, 238U, 232Th, 226Ra) and assessing their ecological impact. The mean activity concentrations of 238U, 232Th, 40K and 226Ra are 63.86 (17.70â92.30 Bq· kg-1), 23.76 (11.10â37.10 Bq· kg-1), 96.84 (30.60â229.30 Bq· kg-1) and 28.09 Bq·kg-1 (3.10â61.80 Bq·kg-1), respectively. Both 238U and 232Th have high correlations with ash yield of coals, suggesting their inorganic origins. The overall environmental effect of natural radionuclides in studied coals is considered to be negligible, as assessed by related indexes (i.e., radium equivalent activity, air-adsorbed dose rate, annual effective dose, and external hazard index). However, the absorbed dose rates values are higher than the average value of global primordial radiation and the Chinese natural gamma radiation dose rate.
Highlights
Combustion of coals that are enriched in radioactive nuclides, those of U series, possibly magnifies the background levels of radioactive nuclides in the surrounding environment and increases human exposure risks [1,2,3,4]
The studied coals have ash yields ranging from 4.71% to 32.12%, and total sulfur ranging from 0.46% to 4.15%, classifying as low ash, medium-high sulfur coals
This study provides an initial assessment on the natural radionuclides in coals from eastern
Summary
Combustion of coals that are enriched in radioactive nuclides, those of U series, possibly magnifies the background levels of radioactive nuclides in the surrounding environment and increases human exposure risks [1,2,3,4]. High concentrations of radioactive nuclides in coals have been reported worldwide. High levels of radioactive nuclides in Chinese coals are rarely reported. Jiang et al (1989) [8] reported that the weighted means of 226 Ra, 232 Th and 40 K in Chinese coals are 36 (2â2300 Bqkg1 ), 30 (4â110 Bqkg1 ) and 104 Bqkg. The coal deposits in eastern Yunnan province, China, have been identified to enrich high levels of natural radionuclides [13,14,15,16,17]. Their spatial variation, modes of occurrences, and controlling factors are rarely illustrated. The radioactive nuclides in coal deposits of this area are reassessed, in an effort to generalize a basic knowledge on their potential environmental impacts
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