Snowpack photochemical production of HONO: A major source of OH in the Arctic boundary layer in springtime

Abstract

Abstract. Both snow manipulation experiments and ambient measurements during the Polar Sunrise Experiment 2000 atAlert (Alert2000) indicate intensive photochemical production of nitrous acid (HONO) in the snowpack. This process constitutes a major HONO source for the overlying atmospheric boundary layer in the Arctic during the springtime, and sustained concentrations of HONO high enough that upon photolysis they became the dominant hydroxyl radical (OH) source. This implies a much greater role for OH radicals in Arctic polar sunrise chemistry than previously believed. Although the observations were made in the high Arctic, this finding has a significant implication for the boundary layer atmospheric chemistry in Antarctica during sunlit seasons and in the mid to high latitudes of the Northern Hemisphere during the winter and spring seasons when approximately 50% of the land mass may be covered by snow.

Photochemical production of nitrous acid on glass sample manifold surface

“…At the relative humidity of !40% observed during the measurement intensive, there should be at least several monolayers of water on the glass manifold wall surfaces [Svensson et al, 1987;Saliba et al, 2001]. Thus the produced NO 2(ads) may react rapidly with adsorbed H 2 O to produce HONO, which is then released from the surface into the air [Pitts et al, 1984] This mechanism is consistent with the recent observations of photochemical production of HONO [Zhou et al, 2001] and NO x [Honrath et al, 1999[Honrath et al, , 2000 in snowpack from nitrate/HNO 3 photolysis. These observations are also supportive of a recent hypothesis that the photolysis of adsorbed HNO 3 /nitrate on ground surfaces is a major daytime source of HONO and thus is responsible for the observed elevated HONO concentrations in the rural atmospheric boundary layer .…”

The photolysis of ortho-nitrophenols: a new gas phase source of HONO

“…[36][37][38][39][40][41][42][43] While the night time formation of HONO in the atmosphere is reasonably well explained by direct emissions and different heterogeneous conversion processes of NO 2 [44][45][46] on ground surfaces, 42 recent sensitive measurements have shown unexpectedly high HONO concentrations during the daytime. 36,38,41,43,47 The measured HONO levels were significantly higher than the values predicted on the basis of the available knowledge about daytime sources and sinks of HONO. The experiments revealed the existence of a strong daytime source of HONO up to 60 times higher than the night time sources 43 and contributing up to 60% to the direct OH radical sources, 48 which was suggested to arise from the photolysis of adsorbed HNO 3 /nitrate 38,47,[49][50][51] or by heterogeneous photochemistry of NO 2 on organic substrates.…”

“…36,38,41,43,47 The measured HONO levels were significantly higher than the values predicted on the basis of the available knowledge about daytime sources and sinks of HONO. The experiments revealed the existence of a strong daytime source of HONO up to 60 times higher than the night time sources 43 and contributing up to 60% to the direct OH radical sources, 48 which was suggested to arise from the photolysis of adsorbed HNO 3 /nitrate 38,47,[49][50][51] or by heterogeneous photochemistry of NO 2 on organic substrates. [52][53][54] Recent work in our laboratory on different aspects of aromatic hydrocarbon photooxidation processes performed in the presence of OH-radical scavengers has revealed that OH radicals are generated during the photolysis of nitrophenols.…”

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

“…This includes different surfaces (ground and aerosols) such as the photocatalytic conversion of NO 2 on mineral dust (Ndour et al 2008), the dark heterogeneous conversion of NO 2 on suspended soot particles (Ammann et al 1998;Arens et al 2001), the heterogeneous hydrolysis of NO 2 (Finlayson-Pitts et al 2003), the photosensitized reduction of NO 2 on organic surfaces (George et al 2005;Stemmler et al 2006), the photolysis of adsorbed nitric acid (HNO 3 ) (Zhou et al 2003) and nitrate (NO 3 − ) (Zhou et al 2001), the HNO 3 conversion on primary organic aerosols (Ziemba et al 2010) and from soilemitted nitrite (Su et al 2011). Direct emissions from combustion processes (i.e.…”