Table 1.

HONO concentrations measured in urban environment.

Observation duration	Location	Instrument	cHONO (ppbv) (median)	References
2001.5–6	Rome, Italy	DOAS	<2	(Acker et al., 2006)
2009.4–5	Houston, USA	ID-CIMS	<1.5(0.19)	(Levy et al., 2014)
2009.7, 2010.1–2	Paris, France	LOPAP	0.01–0.5, 0.01–1.7	(Michoud et al., 2014)
2014.6	York, UK	LOPAP	0.33–1.15	(Crilley et al., 2016)
2014.7–8	London, UK	LOPAP	0.2–1.8	(Lee et al., 2016)
2003.1–2	Kathmandu, Nepal	DOAS	0.15–7.45(1.7)	(Yu et al., 2009)
2004.5–2004.6	Soul, South Korea	WD-IC	1.8 ± 0.4(1.3)	(Shon et al., 2007)
2000.7, 11	Guangzhou, China	GAC	1.0–2.7	(Hu et al., 2002)
2007.8	Beijing, China	WD-IC	1.45 ± 0.58(1.47)	(Spataro et al., 2013)
2011.5, 11	Hongkong, China	LOPAP	0.35 ± 0.30, 0.93 ± 0.67	(Xu et al., 2015)
2014.2–3	Beijing, China	LOPAP	0.28–3.24	(Hou et al., 2016)
2015.7–8	Xi'an, China	LOPAP	1.12 ± 0.97	(Huang et al., 2017)
2006.8–9	Beijing, China	LOPAP, GAC	0.034–3.69	(Yang et al., 2014)
2015.9–10, 2016.1, 4–5, 6–7	Beijing, China	AIM-IC	2.27 ± 1.82; 1.05 ± 89;1.05 ± 0.95; 1.38 ± 0.90	(Wang et al., 2017)
2016.5	Shanghai, China	LOPAP	0.48–5.84(2.31)	(Cui et al., 2018)
2016.12	Beijing, China	LOPAP	3.5 ± 2.7	(Zhang et al., 2019e)
2015.9–2016.8	Jinan, China	LOPAP	1.15 ± 1.07	(Li et al., 2018)
2019.12.15–2020.1.22	Shijiazhuang, China	MARGA	2.43 ± 1.08(2.10)	This work
2019.1.23–2020.2.2			1.53 ± 1.16(1.20)	This work
2019.2.3–2020.2.22			0.97 ± 0.76(0.75)	This work