Explosive morning growth phenomena of NH3 on the North China Plain: Causes and potential impacts on aerosol formation

Ye Kuang; Wanyun Xu; Weili Lin; Zhaoyang Meng; Huarong Zhao; Sanxue Ren; Gen Zhang; Linlin Liang; Xiaobin Xu

doi:10.1016/j.envpol.2019.113621

Explosive morning growth phenomena of NH₃ on the North China Plain: Causes and potential impacts on aerosol formation

Environ Pollut. 2020 Feb:257:113621. doi: 10.1016/j.envpol.2019.113621. Epub 2019 Nov 15.

Authors

Ye Kuang¹, Wanyun Xu², Weili Lin³, Zhaoyang Meng⁴, Huarong Zhao⁵, Sanxue Ren⁵, Gen Zhang⁴, Linlin Liang⁴, Xiaobin Xu⁴

Affiliations

¹ Institute for Environmental and Climate Research, Jinan University, Guangzhou, China.
² State Key Laboratory of Severe Weather & Key Laboratory for Atmospheric Chemistry of CMA, Institute of Atmospheric Composition, Chinese Academy of Meteorological Sciences, Beijing, 100081, China. Electronic address: xuwy@cma.gov.cn.
³ College of Life and Environmental Sciences, Minzu University of China, Beijing, 100081, China.
⁴ State Key Laboratory of Severe Weather & Key Laboratory for Atmospheric Chemistry of CMA, Institute of Atmospheric Composition, Chinese Academy of Meteorological Sciences, Beijing, 100081, China.
⁵ Ecological and Agricultural Meteorology Station of the Chinese Academy of Meteorological Sciences, Baoding City, Hebei Province, 072656, China.

PMID: 31761581
DOI: 10.1016/j.envpol.2019.113621

Abstract

Atmospheric ammonia (NH₃) as the most important alkaline gas in the atmosphere has attracted much attention in recent years due to its critical role in haze formation, especially on the North China Plain (NCP). Comprehensive studies are needed for investigating diurnal variations of NH₃ and underlying mechanisms in different seasons and their potential impacts on atmospheric chemistry. In this study, continuous long-term observation (Mar. 2016 to May 2017) of NH₃ at a rural site in the NCP was used to characterize the diurnal variation of NH₃ in different seasons and to unveil its causes and potential impacts on atmospheric chemistry. NH₃ concentrations displayed rapid increases during the morning, reaching very prominent peaks mostly between 8:00 to 11:00 LT. Such frequent (55%) morning peaks were mainly caused by the evaporation of dew and guttation water droplets. Average dew and guttation water volume concentrations of 750 mL m^-2 was estimated for spring, which resulted in approximate NH₃ emissions of 800 ng m^-2 s^{- 1}. Such high emission fluxes from dew and guttation water evaporation have never been reported before, suggesting dew and guttation droplets to be significant night-time reservoirs and strong morning sources for NH₃. In light of recent studies putting forward that NH₃ can promote the heterogeneous formation of HONO and nitrate under high humidity conditions, we investigated the differences in HONO and aerosol chemical composition diurnal variations between days with and without NH₃ morning spikes during November. HONO, nitrate and sulfate concentrations were significantly higher for days with NH₃ morning spikes, with HONO displaying a morning peak near that of NH₃. These results demonstrate that the prevailing NH₃ morning spikes on the NCP have significant influences on aerosol formation and atmospheric chemistry. NH₃ emission mitigation strategies and regulations are urgently needed.

Keywords: Ammonia source; Dew and guttation; HONO; Haze formation.

MeSH terms

Aerosols / analysis*
Air Pollutants / analysis*
Ammonia / analysis*
China
Environmental Monitoring*

Substances

Aerosols
Air Pollutants
Ammonia