High Levels of Daytime Molecular Chlorine and Nitryl Chloride at a Rural Site on the North China Plain

Abstract

Molecular chlorine (Cl) and nitryl chloride (ClNO) concentrations were measured using chemical ionization mass spectrometry at a rural site over the North China Plain during June 2014. High levels of daytime Cl up to ∼450 pptv were observed. The average diurnal Cl mixing ratios showed a maximum around noon at ∼100 pptv. ClNO exhibited a strong diurnal variation with early morning maxima reaching ppbv levels and afternoon minima sustained above 60 pptv. A moderate correlation (R = 0.31) between Cl and sulfur dioxide was observed, perhaps indicating a role for power plant emissions in the generation of the observed chlorine. We also observed a strong correlation (R = 0.83) between daytime (10:00-20:00) Cl and ClNO, which implies that both of them were formed from a similar mechanism. In addition, Cl production is likely associated with a photochemical mechanism as Cl concentrations varied with ozone (O) levels. The impact of Cl and ClNO as Cl atom sources is investigated using a photochemical box model. We estimated that the produced Cl atoms oxidized slightly more alkanes than OH radicals and enhanced the daily concentrations of peroxy radicals by 15% and the O production rate by 19%.

Wintertime photochemistry in Beijing: Observations of RO<sub>x</sub> radical concentrations in the North China Plain during the BEST-ONE campaign

“…The proposed source originated from photolysis of 20 ClNO 2 generating chlorine radicals, which can oxidize VOC to RO 2 . However, the observed ClNO 2 (0.5 ppbv, maximum of diurnal average, Tham et al, 2016) and Cl 2 (Liu et al, 2017) concentrations could only explain 10% and 30% of the missing primary RO x source for the summer Wangdu campaign (Tan et al, 2017). During the winter campaign in Beijing, the missing primary RO x source was 2 to 3 times larger than what was found during the Wangdu summer campaign.…”

Quantification of known and unknown terpenoid organosulfates in PM10 using untargeted LC–HRMS/MS: contrasting summertime rural Germany and the North China Plain

“…In contrast, for the NCP samples, we found a median NR of 0.7, which indicated that particles were quite acidic for a major part of the measurement period. Similarly, Liu et al (2017) determined the particle pH values for NCP to be typically in the range of 2.8 to 4.8, but even reached down to pH values of 2 during daytime. Such extremely acidic conditions might be necessary for the formation of SQT-OSs, and thus, explain the contrasting trends observed for MEL and NCP.…”

ClNO2 Yields From Aircraft Measurements During the 2015 WINTER Campaign and Critical Evaluation of the Current Parameterization

“…Ambient ClNO 2 was first observed off the coast of Texas in 2006 . It has since been measured from ship-, ground-, and aircraft-based platforms in both continental and coastal/marine environments throughout North America (Edwards et al, 2013;Faxon et al, 2015;Kercher et al, 2009;Kim et al, 2014;Mielke et al, 2011Mielke et al, , 2016Osthoff et al, 2008;Riedel et al, 2012Riedel et al, , 2013Thornton et al, 2010;Wild et al, 2016;Young et al, 2012), Europe and the United Kingdom (Bannan et al, 2015(Bannan et al, , 2017Phillips et al, 2012Phillips et al, , 2016Reyes-Villegas et al, 2018), and Asia (Liu et al, 2017;Tham et al, 2018Tham et al, , 2016Tham et al, , 2014X. Wang, Wang, Xue, et al, 2017;T.…”