Abstract
Abstract. In the past decades, regional air pollution characterized by photochemical smog and grey haze-fog has become a severe environmental problem in China. To investigate this, a field measurement campaign was performed in the Huabei region, located between 32–42° N latitude in eastern China, during the period 2 April–16 May 2006 as part of the project "Influence of Pollution on Aerosols and Cloud Microphysics in North China" (IPAC-NC). It appeared that strong pollution emissions from urban and industrial centers tend to accumulate in the lower atmosphere over the central area of Huabei. We observed widespread, very high SO2 mixing ratios, about 20–40 ppbv at 0.5–1.5 km altitude and 10–30 ppbv at 1.5–3.0 km altitude. Average CO mixing ratios were 0.65–0.7 ppmv at 0.5–1.5 km altitude, and very high CO around 1 ppmv was observed during some flights, and even higher levels at the surface. We find the high pollution concentrations to be associated with enhanced levels of OH and HO2 radicals, calculated with a chemical box model constrained by the measurements. In the upper part of the boundary layer and in the lower free troposphere, high CO and SO2 compete with relatively less NO2 in reacting with OH, being efficiently recycled through HO2, preventing a net loss of HOx radicals. In addition to reactive hydrocarbons and CO, the oxidation of SO2 causes significant ozone production over Huabei (up to ~13% or 2.0 ppbv h−1 at 0.8 km altitude). Our results indicate that the lower atmosphere over Huabei is not only strongly polluted but also acts as an oxidation pool, with pollutants undergoing very active photochemistry over this part of China.
Highlights
The growing influence of gas and aerosol emissions from major urban and industrial centers on air quality and climate on regional to global scales is of great concern
The results have shown that air pollutants from China can be detected over North America and even Europe through longdistance transport and associated chemical transformation processes (Zhang et al, 2008a; Barletta et al, 2009; Fiedler et al, 2009; Cooper et al, 2010)
The principal measurement platforms of IPAC-NC included a twin-engine YUN-12 aircraft operated from Tianjin International Airport and two ground stations, one located at 39.88◦ N, 116.47◦ E on the campus of the Beijing University of Technology (Beigongda station), and the other at 39.73◦ N, 117.53◦ E in the Xin’an weather modification station of the Baodi County of Tianjin Municipality (Xin’an station, previously referred as Baodi station by Ma et al, 2010)
Summary
The growing influence of gas and aerosol emissions from major urban and industrial centers on air quality and climate on regional to global scales is of great concern. Photochemical smog episodes are accompanied by high aerosol loads, causing haze pollution with potential impacts on human health, climate and the hydrological cycle (Ramanathan et al, 2005; Pope and Dockery, 2006; Ma et al, 2010) These aerosols, mainly consisting of fine particles, originate either directly from traffic, industrial activity and biomass burning (primary particles), or indirectly from the gas-to-particle conversion of low-volatile condensable inorganic and organic gases (secondary particles), formed via a complex sequence of oxidation reactions of gaseous precursors from the same sources (Seinfeld and Pandis, 1998; Kulmala, 2003; Jimenez et al, 2009; Apel et al, 2010).
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