Characteristics and formation mechanism of a serious haze event in autumn 2017 in Harbin, China

Abstract

Eighteen air quality monitoring stations in nine districts and nine counties in Harbin were selected to analyze the spatial and temporal characteristics of six basic air pollutants. Straw burning monitoring data, meteorological factor data, and aerosol optical depth (AOD) data were selected in combination with backward trajectory of hybrid single particle lagrangian integrated trajectory (HYSPLIT) to analyze the causes of air pollution. The results showed that the daily variation of the six pollutants was consistent with the three haze processes, and the main pollutants were particulate matter 2.5 (PM2.5) and particulate matter 10 (PM10). Except for O3, the hourly variations in the concentrations of other pollutants showed the same patterns over time. The concentrations increased at night and gradually decreased during the day. The most polluted areas were the urban area and the central area of Harbin, among which the worst was the Shuangcheng District. The cause of the pollution is as follows: First, there are a large number of straw burning areas surround Harbin, which cause high particulate matter emission. Second, the weak air pressure and low wind speed limit pollutant diffusion, allowing gradual accumulation, resulting in a high concentration of particles near the ground. Finally, regional pollutant transport from the southwest also contributes to the pollution process.