Significant concentrations of nitryl chloride sustained in the morning: investigations of the causes and impacts on ozone production in a polluted region of northern China
Item
Title (Dublin Core)
Significant concentrations of nitryl chloride sustained in the morning: investigations of the causes and impacts on ozone production in a polluted region of northern China
Description (Dublin Core)
Nitryl chloride (ClNO<sub>2</sub>) is a dominant source of chlorine radical in polluted environment, and can significantly affect the atmospheric oxidative chemistry. However, the abundance of ClNO<sub>2</sub> and its exact role are not fully understood under different environmental conditions. During the summer of 2014, we deployed a chemical ionization mass spectrometer to measure ClNO<sub>2</sub> and dinitrogen pentoxide (N<sub>2</sub>O<sub>5</sub>) at a rural site in the polluted North China Plain. Elevated mixing ratios of ClNO<sub>2</sub> (> 350 pptv) were observed at most of the nights with low levels of N<sub>2</sub>O<sub>5</sub> (< 200 pptv). The highest ClNO<sub>2</sub> mixing ratio of 2070 pptv (1 min average) was observed in a plume from a megacity (Tianjin), and was characterized with a faster N<sub>2</sub>O<sub>5</sub> heterogeneous loss rate and ClNO<sub>2</sub> production rate compared to average conditions. The abundant ClNO<sub>2</sub> concentration kept increasing even after sunrise, and reached a peak 4 h later. Such highly sustained ClNO<sub>2</sub> peaks after sunrise are discrepant from the previously observed typical diurnal pattern. Meteorological and chemical analysis shows that the sustained ClNO<sub>2</sub> morning peaks are caused by significant ClNO<sub>2</sub> production in the residual layer at night followed by downward mixing after breakup of the nocturnal inversion layer in the morning. We estimated that ∼ 1.7–4.0 ppbv of ClNO<sub>2</sub> would exist in the residual layer in order to maintain the observed morning ClNO<sub>2</sub> peaks at the surface site. Observation-based box model analysis show that photolysis of ClNO<sub>2</sub> produced chlorine radical with a rate up to 1.12 ppbv h<sup>−1</sup>, accounting for 10–30 % of primary RO<sub><i>x</i></sub> production in the morning hours. The perturbation in total radical production leads to an increase of integrated daytime net ozone production by 3 % (4.3 ppbv) on average, and with a larger increase of 13 % (11 ppbv) in megacity outflow that was characterized with higher ClNO<sub>2</sub> and a relatively lower oxygenated hydrocarbon (OVOC) to non-methane hydrocarbon (NMHC) ratio.
Creator (Dublin Core)
Tham, Yee Jun
Wang, Zhe
Li, Qinyi
Yun, Hui
Wang, Weihao
Wang, Xinfeng
Xue, Likun
Lu, Keding
Ma, Nan
Bohn, Birger
Li, Xin
Kecorius, Simonas
Größ, Johannes
Shao, Min
Wiedensohler, Alfred
Zhang, Yuanhang
Wang, Tao
Date (Dublin Core)
2018-09-21
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-16-14959-2016
https://acp.copernicus.org/articles/16/14959/2016/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
