Volume 11, No. 7, December 2011, Pages 873-882 PDF(520 KB)
Estimation of the Main Factors Influencing Haze, Based on a Long-term Monitoring Campaign in Hangzhou, China
Zhi-mei Xiao1, Yu-fen Zhang1, Sheng-mao Hong2, Xiao-hui Bi1, Li Jiao2, Yin-chang Feng1, Yu-qiu Wang1
1 State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, College of Environmental Science and Engineering, Nankai University, No. 94 Weijin Road, Tianjin 300071, China
2 Hangzhou Municipal Environmental Monitoring Centre, Hangzhou 310007, China
Eight years of data on haze and visibility (2003–2010) and one year of (2010) data on surface meteorological elements (relative humidity, wind speed, air temperature), visibility and the concentrations of air pollutants (PM2.5, SO2, NO2 and O3) measured each hour of each day were analyzed using correlation analysis to investigate the main factors influencing haze in Hangzhou, China. The occurrence of hazy weather has become more frequent over the past eight years in Hangzhou, and haze appears about 160 days per year. The occurrence of haze during the day was more frequent in the spring and the winter and less frequent in the summer and the autumn. Low visibility occurred in the morning, and the maximum visibility occurred in the afternoon period. The results of the statistical analysis show that the relative humidity and the concentration of PM2.5 played the most important roles in reducing visibility. The correlation coefficients between the concentration of PM2.5 and the concentrations of O3, SO2 and NO2 indicate that O3 and NO2 are the dominant factors contributing to PM2.5 pollution, which, in turn, can lead to haze. To reduce the number of haze days, greater concern and more countermeasures should be taken to decrease the O3 and NO2 pollution in Hangzhou, China.
Haze; Relative humidity; PM2.5; O3; NO2.