Regional Characteristics of Air Pollutants during Heavy Haze Events in the Yangtze River Delta, China

Honglei Wang,Yue'E Li,Duanyang Liu,Bin Zhu,Junlin An,Lijuan Shen,Honghui Xu,Chen Pan

doi:10.4209/aaqr.2015.09.0551

Abstract

There were 6 severe haze events over a large area of the Yangtze River Delta (YRD) region in January 2013. In this study, based on the hourly concentrations of trace gases and PM_(2.5) at 10 observation stations (8 city stations, 1 regional background station and 1 island station) during Jan. 1-31, 2013 as well as the concentrations of water-soluble ions at 5 stations (4 city stations and 1 regional background station) during Jan. 18-24, 2013 in the YRD region, the regional characteristics of the air pollutants during heavy haze episodes were investigated in combination with the atmospheric circulation patterns. The concentrations of PM_(2.5) on haze days were 1.6-2.4-fold higher than on clear days. The concentration of PM_(2.5), SO_2, NO_2 and CO increased significantly, with average values of 128.6, 48.5, 78.1 μg m^(-3) and 1.5 mg m^(-3) on haze days, and were 64.6, 36, 52.5 μg m^(-3) and 1.1 mg m^(-3) on clear days. The PM_(2.5) concentration of ten observation sites had positive correlations with CO and NO_2, and had weakly negative correlations with O_3. The sources of PM_(2.5), SO_2, NO_2 and CO were strong in inland cities and weak in coastal cities, and the sources of O_3 were mainly from Wuxi, Suzhou and southeast of An'hui. The mass and water-soluble ion concentrations were both centralized in PM_(2.1) during the haze events; additionally, the NH_4^+, SO_4^(2-) and NO_3^- ions were dominant, constituting 86-90.9% of the total ion concentrations in PM_(2.1). The mass spectra of NH_4^+, K^+, Cl^-, SO_4^(2-), F^-, NO_2^- and NO_3^- had unimodal distributions. The secondary formations of sulfate dominated on haze days, and the nitrate oxidation rates were relatively high for inland cities and low for coastal cities.

Highlights

In recent years, haze pollution has attracted substantial attention due to its significant effects on visibility and public health in China (Wu et al, 2007; Tie et al, 2009; Zhang et al, 2015)
A continuous and wide range of heavy haze pollution episodes occurred in January 2013, which was due to the specific atmospheric circulation
It was dominated by a weak ridge or a straight westerly at 500 hPa on Jan. 6; there was anticyclonic circulation at 850 hPa and the ground isobar was relatively sparse, indicating that the wind speed was small and the weather was clear on the low level of the Yangtze River Delta (YRD) region

Summary

Introduction

Haze pollution has attracted substantial attention due to its significant effects on visibility and public health in China (Wu et al, 2007; Tie et al, 2009; Zhang et al, 2015).

Results

Conclusion