对复杂地形和低风条件下放射性核素大气扩散模拟对比研究

Comparison Study of Radionuclide Dispersion Modeling in Regions of Complex Topography and Low Wind Condition

使用《环境影响评价技术导则大气环境》(HJ2.2-2008)推荐的大气环境影响预测模式(AERMOD和CALPUFF)对某一复杂地形区域高架烟囟排放的放射性核素进行了大气扩散模拟的对比研究。模拟结果表明:在研究时段内,AERMOD计算出的平均落地浓度最大值高于CALPUFF;计算出的最大小时落地浓度和最大日均落地浓度也均高于CALPUFF计算出的相应值。对复杂地形条件下的高架烟囟释放,AERMOD出现最大小时落地浓度的时刻不一定是风速较低的时刻,而是对应下风向附近有高海拔受体、且风速适中、污染物易通过风的平流输送在高海拔受体处形成撞山高浓度的时刻;CALPUFF出现最大小时落地浓度的时刻一般是排放口和地表风速较低、且大气又极不稳定、垂直方向湍流剧烈的时刻。对复杂地形条件下的放射性核素大气扩散模拟,相对于AERMOD模式,CALPUFF模式可模拟生成更加真实的气象场、采用了烟团扩散模式而更具优势。

The recommended atmospheric environmental impact prediction models AERMOD and CALPUFF in Guidelines for Environmental Impact Assessment Atmospheric Environment of HJ2. 2-2008 were compared to simulate the performance of airborne radionuclides released from elevated chimneys in the complex terrain. The simulation results showed that,in the study period,the maximum average concentration calculated by AERMOD was higher than calculated by CALPUFF; the maximum hourly concentration and the maximum daily concentration were higher than the corresponding values calculated by CALPUFF as well. For the elevated chimneys release in the complex terrain,the maximum hourly concentration calculated by AERMOD does not always occur when the wind speed is low,but in the condition that there is near high-altitude receptor,and the wind speed is moderate,easy for contamination transporting to the high-altitude receptor. The maximum hourly concentration calculated by CALPUFF generally occurs when the discharge and near surface wind speeds are low,and the atmosphere is extremely unstable leading to severe vertical turbulent. For simulating the performance of airborne radionuclides in the complex terrain,the C ALPUFF model is more advantageous than the AERMOD model,which simulates a more realistic meteorological field and adopt the puff diffusion model.