Anthropogenic Pollutants Induce Changes in Peroxyacetyl Nitrate Formation Intensity and Pathways in a Mountainous Background Atmosphere in Southern China

Abstract

Mountainous background areas are typically considered to have a clean atmosphere where peroxyacetyl nitrate (PAN) can be decomposed. This study demonstrated that PAN was photochemically formed with a simulated production rate of 0.28 ± 0.06 ppbv h −1 in the Nanling mountains (1690 m a.s.l.) of South China and that net PAN formation was dependent on both volatile organic compounds (VOCs) and NO x precursors (transition regime). In contrast to dominated acetaldehyde oxidation in previous urban and rural research, PAN at Nanling was primarily formed by methylglyoxal (38%), acetaldehyde (28%), radicals (20%), and other oxygenated volatile organic compounds (OVOCs) (13%). Moreover, when polluted air masses invaded the Nanling mountains, the PAN production rate was altered, primarily because anthropogenic aromatics intensified PAN formation via the oxidized pathways of methylglyoxal, other OVOCs, and radicals. Finally, net PAN formation at Nanling reduced the hydroxyl radical level by consuming NO x , impaired local radical cycling, and thereby suppressed local O 3 production. This suppressing effect was exacerbated on polluted days. The findings of this study deepen our understanding of PAN photochemistry and the impact of anthropogenic intrusions on the background atmosphere of mountainous regions.

A Comparative Study of Ground-Gridded and Satellite-Derived Formaldehyde during Ozone Episodes in the Chinese Greater Bay Area

“…The F0AM model used in this study included 142 non-methane VOCs and over 17,000 elementary reactions of 5900 species [85]. It considered the physical process of deposition within the boundary layer height (BLH) and inputted observation parameters, including gaseous pollutants (i.e., O 3 , CO, NO, NO 2 , HONO, SO 2 , and VOCs), meteorological parameters (i.e., T, P, and RH), and photolysis rate constants (J O 1 D , J NO 2 , J H 2 O 2 , J HONO , J HCHO , and J NO 3 ), as constraints [86]. The photolysis rates of additional molecules, including OVOCs, were parameterized based on the solar zenith angle and then adjusted according to J NO 2 measurements [87].…”