中文摘要：

选取西安为研究对象,通过建立能够刻画该地区PM_（2.5）发生和演变（扩散与衰减等）规律的数学模型,完成对该地区污染扩散预测评估.通过采用PCA方法确定西安地区PM_（2.5）的扩散中心,并构建线性抛物型方程对一般情况下的扩散进行刻画,针对突发情形,即当PM_（2.5）浓度最高点处增至2倍时,采用高斯模型对数据进行扩散的预测和评估,计算出PM_（2.5）的污染扩散范围.最后通过比较完成对该地区的污染预测评估.

英文摘要：

Xi＇an has been selected as the study case in this paper,in which the pollution has been predicted by establish the mathematical model with which the occurrence and evolution（diffusion and attenuation）of PM_（2.5）can be described.In the PCA method,the spread center of PM_（2.5）has been determined,aquasilinear parabolic equation constructed to describe the diffusion of PM_（2.5）under normal circumstances,as the basis for the emergency situations that when the highest point of PM_（2.5） concentrations increased 2-fold.By means of Gaussian model,the range of PM_（2.5） pollution diffusion has been calculated.And the pollution forecast for the region been completed by comparison.