Seasonal and diurnal variations of ambient PM2.5 concentration in urban and rural environments in Beijing
Seasonal and diurnal variations of ambient PM2.5 concentration in urban and rural environments in Beijing
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DOI：
10.1016/j.atmosenv.2009.03.009
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发表时间：
2009-06
影响因子：
5
通讯作者：
Xiujuan Zhao;Xiaoling Zhang;Xiaofeng Xu;Jing Xu;W. Meng;W. Pu
中科院分区：
文献类型：
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作者：
Xiujuan Zhao;Xiaoling Zhang;Xiaofeng Xu;Jing Xu;W. Meng;W. Pu
2005 - 2007年，在北京市城乡环境中进行了为期3年的PM2. 5浓度的5 min时间分辨率测量，研究了PM2. 5浓度的季节变化和日变化。在城市地区观察到明显的季节性变化，通常在冬季观察到最高浓度，而通常在夏季观察到最低浓度。在农村地区，PM2.5浓度的最大值通常出现在春季，其次是夏季，最小值通常出现在冬季。在城市和农村地区的PM2.5浓度的日变化显着。在市区，PM2.5浓度呈现双峰模式，峰值出现在上午7：00 - 8：00。晚上7点到11点之间最小值一般出现在中午前后。早高峰是由于在高峰时段加强了人类活动。下午边界层高度和风速的降低以及下午高峰时段源活动的增加导致了傍晚时段PM2.5浓度的最高值。农村地区PM2.5浓度呈单峰型，峰值出现在下午5：00 ~ 11：00。城市PM2.5浓度的季节和日变化主要受边界层和源排放的季节和日变化的影响。降水的年际变化对城区PM2. 5的季节变化也有重要影响。季节风场和日风场是影响农村地区PM2.5变化的重要因素。南风将南部城市地区排放的污染物向北输送，并显著提高了农村地区的PM2.5浓度水平。
Three years of measurement of PM2.5with 5-min time resolution was conducted from 2005 to 2007 in urban and rural environments in Beijing to study the seasonal and diurnal variations in PM2.5concentration. Pronounced seasonal variation was observed in the urban area, with the highest concentrations typically observed in the winter and the lowest concentrations generally found in the summer. In the rural area, the maximum in PM2.5concentration usually appeared during the spring, followed by a second maximum in the summer, while the minimum generally occurred in the winter. Significant diurnal variations in PM2.5concentration were observed in both urban and rural areas. In the urban area, the PM2.5concentration displays a bimodal pattern, with peaks between 7:00 and 8:00 a.m. and between 7:00 and 11:00 p.m. The minimum generally appears around noon. The morning peak is attributed to enhanced anthropogenic activity during rush hours. The decreases of boundary layer height and wind speed in the afternoon companying with increased source activity during the afternoon rush hour result in the highest PM2.5concentration during evening hours. In the rural area, the PM2.5concentration shows a unimodal pattern with a significant peak between 5:00 and 11:00 p.m. The seasonal and diurnal variations in PM2.5concentration in the urban area are mostly dominated by the seasonal and diurnal variability of boundary layer and source emissions. The year-to-year variability of rainfall also has an important influence on the seasonal variation of PM2.5in the urban area. The seasonal and diurnal wind patterns are more important factors for PM2.5variation in the rural area. Southerly winds carry pollutants emitted in southern urban areas northward and significantly enhance the PM2.5concentration level in the rural area.