颗粒物干沉降对AERMOD模型预测大气污染的影响

The effect of particulate dry deposition on air pollution simulated by AERMOD model

AERMOD模型是《环境影响评价技术导则—大气环境》中的推荐模式。为了更好地验证颗粒物干沉降作用对该模型预测结果的影响,选取福州市的煤堆场作为面源污染源,对预测范围内所有网格点PM10、TSP最大地面浓度进行预测。结果表明:所有网格点TSP地面浓度考虑干沉降时,约为不考虑干沉降时的0.13;PM10地面浓度考虑干沉降时,约为不考虑干沉降时的0.70,干沉降对TSP的影响大于PM10。同一粒径分布下,密度对颗粒物干沉降的影响较大,密度增加对可吸入颗粒物干沉降的影响大于总悬浮颗粒物,当密度大于3 g.cm-3时,所有网格点PM10与TSP地面浓度比值的平均值接近于0.98,认为粒径大于10μm的颗粒物基本完全沉降。此后,随着密度增加网格点处地面浓度的减小主要由PM10的沉降引起。AERMOD考虑干沉降时,距离污染源中心500 m外的网格点处地面浓度,PM10/TSP>0.98,大于10μm的粗颗粒几乎完全沉降。

The AERMOD is a recommended atmospheric simulation model by＂a guideline of environment impact assessment：atmospheric environment＂.To validate the effect of particulate matter dry deposition on the results of ground concentration predicted by AERMOD model,a coal storage yard in Fuzhou was selected as a non-point source,and the maximum ground concentrations of PM10 and TSP in each grid point within the forecast range were predicted.The results indicate that the ratio of surface TSP concentration with counting dry deposition and without counting dry deposition is 0.13 in all grid points.The same ratio for PM10 is 0.70.The effect of dry deposition is larger on TSP than on PM10.The effect of density on particulate matter dry deposition is significant within the same particle size,while the effect of density increase is larger on dry deposition of inhalable particulate matter than on that of TSP.When the density is higher than 3 g · cm-3,the PM10/TSP ratios of the average ground concentrations are all close to 0.98 in all grid points.The particles diameters larger than 10 μm are almost deposited completely.Thus,the decrease of surface concentration in the grid point is caused by PM10 deposition with the increase of density.The ratio of the surface concentration of PM10 to that of TSP in the grid point 500 m away from the source center is larger than 0.98 when dry deposition is considered in the AERMOD model,and coarse particles larger than 10 μm are almost deposited completely.