Technical Note: The application of an improved gas and aerosol collector for ambient air pollutants in China

• Main Authors: H.-B. Dong, L.-M. Zeng, M. Hu, Y.-S. Wu, Y.-H. Zhang, J. Slanina, M. Zheng, Z.-F. Wang, R. Jansen
• Format: Article
• Language: English
• Published: Copernicus Publications 2012-11-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/12/10519/2012/acp-12-10519-2012.pdf

An improved Gas and Aerosol Collector (GAC) equipped with a newly designed aerosol collector and a set of dull-polished wet annular denuder (WAD) was developed based on a Steam Jet Aerosol Collector (SJAC) sampler. Combined with Ion Chromatography (IC) the new sampler performed well in laboratory tests with high collection efficiencies for SO<sub>2</sub> (above 98%) and particulate sulfate (as high as 99.5%). An inter-comparison between the GAC-IC system and the filter-pack method was performed and the results indicated that the GAC-IC system could supply reliable particulate sulfate, nitrate, chloride, and ammonium data in field measurement with a much wider range of ambient concentrations. When applied in two major field campaigns (rural and coastal sites) in China, the GAC-IC system provided high-quality data in ambient conditions even under high loadings of pollutants. Its measurements were highly correlated with data by other commercial instruments such as the SO<sub>2</sub> analyzer (43c, Thermo-Fisher, USA; <i>R</i><sup>2</sup> as 0.96), the HONO analyzer (LOPAP, Germany; <i>R</i><sup>2</sup> as 0.91 for samples from 15:00 to 07:00), a filter sampler (Tianhong, China; <i>R</i><sup>2</sup> as 0.86 for SO<sub>4</sub><sup>2−</sup>), and Aerosol Mass Spectrometer (AMS, Aerodyne, USA; <i>R</i><sup>2</sup> above 0.77 for major species) over a wide range of concentrations. Through the application of the GAC-IC system, it was identified that 70% of chloride and nitrate by the filter method could be lost during daytime sampling due to high temperature in the rural site of Kaiping. In Changdao field campaign (coastal site), though a particle dryer was applied, its drying efficiency was not well considered for the collection efficiency of AMS seemed still interfered a bit by local high relative humidity. If the inter-comparison was done with relative humidity below 50%, the correlations ranged from 0.81 to 0.94 for major species. Through laboratory and field studies, this instrument is proved particularly useful in future intensive campaigns or long-term monitoring stations to study various environmental issues such as secondary aerosol and haze formation, as well as climate change.