张家界市一次旅游高峰期前后PM_(2.5)污染演化的动力特征分析

Study on the Dynamics of PM_(2.5) Before and After the Peak Days of Tourism in Zhangjiajie

应用去趋势波动分析法(DFA)分析张家界市一次旅游高峰期前后(即2014年4月2日至10日,其中4月5日至7日为清明假期)大气PM2.5浓度序列的演变规律.结果表明,旅游高峰前后各站点大气PM2.5的浓度时间序列至少在7 d的尺度上具有长期持续性特征,且景区内站点(袁家界、未央路)PM2.5的长期持续性要强于城区(永定新区、电业局).用滑动窗口的方法讨论了长期持续性随时间的变化特征,发现各站点旅游高峰前后,PM2.5的长期持续性特征均表现出很强的稳定性,并没有出现旅游高峰过后大气PM2.5长期持续性减弱的现象.该现象说明,张家界市一次旅游高峰期间,PM2.5的波动演化在动力学上主要是由PM2.5的长期持续性特征主导控制.该研究有助于加深对旅游城市大气PM2.5污染演变动态过程的认识.

Detrended fluctuation analysis method was used to investigate the evolution law of PM2.5 before and after the peak days of tourism（from 2 Apr. to 10 Apr.） in Zhangjiajie. It was exhibited that there is an obvious long-range correlation at scale of 7 days as to the time series of PM2.5 during the study period for each monitoring site, and the long-range correlation is stronger for the scenic spot（Yuanjiajie, Weiyanglu）, compared with the sites of urban （Yongdingxinqu, Dianyeju）. The variation characteristics of long-range correlation over time were analyzed by sliding window method. It was found that the long-range correlation does not appear to weaken after the peak days of tourism, which is stable for all sites. This phenomenon suggests that the temporal evolution of PM2.5 concentrations is mainly affected by the long-range correlation mechanism before and after the peak days of tourism. The research finding helps to further strengthen understanding of the PM2.5 pollution evolution process for tourism city.