杭州余杭地区环境空气高污染特征及成因分析

Characteristics and Causes of Heavy Air Pollution Episodes in Yuhang District of Hangzhou

基于2012年4月26日-5月8日以及6月9-14日期间的连续在线监测结果,研究了重污染天气下杭州余杭地区空气污染的特征和规律,并重点分析了2个典型的高污染过程的成因及污染来源。研究结果表明:高污染过程中,余杭地区细颗粒浓度非常高,高时段PM2.5达0.4 mg/m^3、能见度低于1 km;结合其他气态污染物监测结果,可知余杭地区具有复合型大气污染特征;5月1-8日出现了区域污染过程,72 h后向轨迹表明,该次区域大范围污染过程期间受外来输送影响,同时存在静风、相对较高的温度、高湿下的本地污染物排放累积,这2个因素是该次极端高污染过程的主要原因;6月11-15日,余杭周边未出现区域性污染,24 h后向轨迹路线表明染主要是由于该地污染物排放的累积导致。因此,该次高污染过程是在静稳天气条件下,该地污染物排放累积,同时在大气化学反应的作用下,二次细颗粒物急剧生成所致。初步判断,其主要排放源前期主要来自于机动车排放影响,后期则受到燃煤源和机动车排放的叠加影响。

Based on the continuous on-line monitoring results from April 26 to May 8, 2012 and June 9 to June 14, 2012,the characteristics and laws of the heavy pollution weather in Yuhang area, Hangzhou were studied, with the focus on analysis of the causes and pollution sources of two typical high pollution process. Results showed that in the process of high pollution,concentration of fine particles in the area was very high, up to 0.4 mg/m^3, and the visibility was less than 1km. Combined with other gaseous pollutants monitoring results, the characteristics of air pollution in the area had composite features.Pollution episode of May 1 to May 8 showed regional process, Hysplit 72 hours showed foreign transport affected this regional wide-range pollution; meanwhile there was emissions of pollutants, static wind, relatively high temperature and high humidity, which were the main factors for the extreme high pollution process. Episode of June 11 to June 15 did not suffer the regional pollution, Hysplit 24 hours showed that pollution was mainly due to the accumulation of local pollutant emission.Therefore, the high pollution process was the result of the accumulation of pollutants in the static and stable weather conditions, and the rapid formation of the two fine particulate matters at the same time. It can be preliminarily ascertained that the main emission sources were mainly derived from the impact of motor vehicle emissions at early days, and later from the superposition of coal and motor vehicle emissions.