Comparisons of measured nitrous acid (HONO) concentrations in a pollution period at urban and suburban Beijing, in autumn of 2014

Abstract

To study the HONO formation mechanisms during a pollution period, a continuous measurement was performed in both urban and suburban aeras of Beijing. During this period, the PM 2.5 concentrations increased to 201 and 137 g/m 3 in urban and suburban areas, respectively. The concentrations of HONO, CO, SO 2 , O 3 , NO, NO 2 , NO x were 1.45 ppbv, 0.61 ppmv, 8.7 ppbv, 4.3 ppbv, 44.4 ppbv, 37.4 ppbv, 79.4 ppbv and 0.72 ppbv, 1.00 ppmv, 1.2 ppbv, 7.9 ppbv, 3.7 ppbv, 8.2 ppbv, 11.9 ppbv, in urban and suburban areas, respectively. To compare possible pathways of HONO formation in both sites, the contributions of direct emissions, heterogeneous formations, and homogeneous productions were studied. HONO/NO 2 ratios in the two sites indicated that heterogeneous reactions of NO 2 were more efficient in suburban areas. And in both urban and suburban areas, the increase of PM 2.5 concentrations and RH would promote the conversion efficiency in RH that ranged from 0% to 85%. However, when RH was above 85%, the HONO formation slowed down. Moreover, the study of direct emissions and homogeneous reactions showed that they contributed to a majority of HONO increase in urban areas than the 20% contributions in suburban areas. It implied that the high NO x concentrations and NO concentrations in urban areas or in pollution periods would make direct emissions and homogeneous reactions become dominant in HONO formations.

Exploring the nitrous acid (HONO) formation mechanism in winter Beijing: direct emissions and heterogeneous production in urban and suburban areas

“…The average values of HONO concentrations at the urban and suburban sites were comparable to our previous measurements at the same observation sites in October of 2014. 28 Moreover, they were also in accordance with measurements by Spataro et al 22 (HONO concentration was 1.06 ppbv on average with NO 2 of 38.8 ppbv) and Hendrick et al 23 (2 ppbv at urban sites and 1.25 ppbv at suburban sites in Beijing). It could be seen from Fig.…”

“…The measurement sites were described in detail in a previous study. 28 The locations of the measurement sites are shown in Fig. 1 Suburban site: the HONO analyzer and other gas analyzers were set in the Lake Yanqi campus of the University of Chinese academy of sciences (UCAS, 40.4 N, 116.6 E).…”

Measurements of nitrous acid (HONO) in urban area of Shanghai, China

“…For comparison, the field measurement conducted by Hao et al (2006) in October 2004 to January 2005 at the same location led to daytime and nighttime HONO/NO 2 ratios of 0.022 and 0.058, respectively. The obtained HONO/NO 2 ratios were in line with those observed in many urban areas in the world during daytime (HONO/NO 2 = 0.003-0.075) and nighttime (HONO/NO 2 = 0.025-0.175) measurements (Alicke et al 2002;Acker et al 2006;Hao et al 2006;Kanaya et al 2007;Elshorbany et al 2009;Qin et al 2009;Tong et al 2015).…”

Contributions of different sources to nitrous acid (HONO) at the SORPES station in eastern China: results from one-year continuous observation

“…Nitrous acid (HONO) is a vital constituent of nitrogen cycle in the atmosphere, first observed in the field by Perner and Platt (1979). The concentrations of HONO varied from dozens of ppt in remote regions (Villena et al, 2011b;Meusel et al, 2016) to several ppb in polluted urban regions (Yu et al, 2009;Tong et al, 2015). The photolysis of HONO (R1) has been long standing as a momentous source of the hydroxyl radical (OH) especially during the early morning when other OH sources are minor (Platt et al, 1980;Alicke, , 2003.…”