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Enhanced sulfate formation by nitrogen dioxide: Implications from in situ observations at the SORPES station
Author(s) -
Xie Yuning,
Ding Aijun,
Nie Wei,
Mao Huiting,
Qi Ximeng,
Huang Xin,
Xu Zheng,
Kerminen VeliMatti,
Petäjä Tuukka,
Chi Xuguang,
Virkkula Aki,
Boy Michael,
Xue Likun,
Guo Jia,
Sun Jianning,
Yang Xiuqun,
Kulmala Markku,
Fu Congbin
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd023607
Subject(s) - sulfate , environmental chemistry , oxidizing agent , particulates , chemistry , nitrogen dioxide , atmosphere (unit) , pollution , air pollution , pollutant , nitrogen , meteorology , geography , ecology , organic chemistry , biology
Investigating sulfate formation processes is important not only for air pollution control but also for understanding the climate system. Although the mechanisms of secondary sulfate production have been widely studied, in situ observational evidence implicating an important role of NO 2 in SO 2 oxidation in the real atmosphere has been rare. In this study, we report two unique cases, from an intensive campaign conducted at the Station for Observing Regional Processes of the Earth System (SORPES) in East China, showing distinctly different mechanisms of sulfate formation by NO 2 and related nitrogen chemistry. The first case occurred in an episode of mineral dust mixed with anthropogenic pollutants and especially high concentrations of NO x . It reveals that NO 2 played an important role, not only in surface catalytic reactions of SO 2 but also in dust‐induced photochemical heterogeneous reactions of NO 2 , which produced additional sources of OH radicals to promote new particle formation and growth. The second case was caused by aqueous oxidation of S(IV) by NO 2 under foggy/cloudy conditions with high NH 3 concentration. As a by‐product, the formed nitrite enhanced HONO formation and further promoted the gas‐phase formation of sulfate in the downwind area. This study highlights the effect of NO x in enhancing the atmospheric oxidizing capacity and indicates a potentially very important impact of increasing NO x on particulate pollution formation and regional climate change in East Asia.