Characteristics and formation mechanism of regional haze episodes in the Pearl River Delta of China

Wenguang Li; Xingang Liu; Yuanhang Zhang; Kang Sun; Yusheng Wu; Rui Xue; Limin Zeng; Yu Qu; Junling An

doi:10.1016/j.jes.2017.03.018

Characteristics and formation mechanism of regional haze episodes in the Pearl River Delta of China

J Environ Sci (China). 2018 Jan:63:236-249. doi: 10.1016/j.jes.2017.03.018. Epub 2017 Mar 29.

Authors

Wenguang Li¹, Xingang Liu², Yuanhang Zhang³, Kang Sun⁴, Yusheng Wu⁴, Rui Xue⁴, Limin Zeng⁴, Yu Qu⁵, Junling An⁵

Affiliations

¹ State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
² State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China. Electronic address: liuxingang@bnu.edu.cn.
³ State Key Joint Laboratory of Environment Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China. Electronic address: yhzhang@pku.edu.cn.
⁴ State Key Joint Laboratory of Environment Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
⁵ State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.

PMID: 29406106
DOI: 10.1016/j.jes.2017.03.018

Abstract

To investigate the characteristics and the specific mechanism of continuous haze, comprehensive measurements were conducted from 15 October to 19 November in the Atmospheric Environment Monitoring Super-Station in Heshan of Guangdong province. Five haze episodes occurred in October and November 2014 in the Pearl River Delta (PRD) region. The meteorological parameters, gas data, chemical compositions, and optical parameters of the aerosols were obtained. Among these events, the second haze episode, with the highest concentration of PM_2.5 of 187.51μg/m³, was the most severe. NO₃^- was always higher than SO₄^2-, which indicated that motor vehicles played an important role in the haze, even though the oxidation rate from SO₂ to SO₄^2- was faster than that of NO_X to NO₃^-. The difference between the hourly averages of Na⁺ and K⁺ during the haze episode and clean days was small, implying that straw combustion and sea salt had no significant effect on the occurrence of haze, and the backward trajectories of the air masses also conformed with this result. The air pollutants were difficult to disperse because of the significant decrease in the planetary boundary layer (PBL) height. Relative humidity played a crucial role in the formation of haze by leading to hygroscopic growth of the diameter of aerosols.

Keywords: Chemical characteristics; Formation mechanism; Haze episodes; PRD.

MeSH terms

Air Pollutants
China
Environmental Monitoring*
Particulate Matter / analysis*

Substances

Air Pollutants
Particulate Matter