外来源影响北京地区空气质量的典型个例分析

Typical case study on external pollution sources influencing air quality in Beijing area

利用京津冀地区80个环境监测站PM_(2.5)浓度的逐时监测资料和常规气象站的观测资料,分析了2013年1月京津冀地区3次典型重污染天气过程PM_(2.5)浓度的分布和演变特征,选取PM_(2.5)浓度快速增长时段的风场特征分析外来源对北京地区污染输送的影响。结果表明:2013年1月京津冀地区存在3个PM_(2.5)浓度高值中心,分别位于石家庄—保定、廊坊和唐山地区。北京地区外来源主要来自河北省中南部的石家庄—保定及廊坊一带,主要通过边界层偏南风远距离输送影响北京地区,边界层辐合线和逆温结构加剧了污染物在北京地区的累积。随着静稳时间的增长,PM_(2.5)污染物向燕山和太行山前输送堆积,造成北京地区PM_(2.5)浓度高于河北省中南部地区,北京市郊区PM_(2.5)浓度高于城区。

Based on the hourly PM_（2.5） concentration observed at eighty environmental monitoring stations and conventional meteorological data, the spatial-temporal characteristics of PM_（2.5） concentration during three typical severe pollution events over the Beijing-Tianjin-Hebei region in January of 2013 were analyzed. The effect of external pollution sources on the pollutants transport in the Beijing area was investigated by analyzing the characteristics of wind field during the period of rapidly increasing PM_（2.5） concentration. The results indicate that there are three highvalue centers of PM_（2.5） concentration over the Beijing-Tianjin-Hebei region in January of 2013,and they are located at the Shijiazhuang-Baoding,Langfang,and Tangshan areas in Hebei province, respectively. The external pollution sources for the Beijing area mainly come from the middle and southern regions of Hebei province such as the ShijiazhuangBaoding and Langfang areas. Pollutants can be transported from long distance by the southerly winds in the boundary layer,and the convergence line and inversion structure in the boundary layer strengthen the accumulation of pollutants in the Beijing area. Under the persistent stable weather condition,PM_（2.5） pollutants are transported and accumulated in front of the Yanshan and Taihang mountains. This leads to PM_（2.5） concentration in the Beijing area larger than that in the middle and southern regions of Hebei province,and that in the suburban areas higher than that in the urban areas of Beijing.