Characterization of Atmospheric Ammonia over Xi'an, China

Jun-Ji Cao；Ting Zhang；Judith C. Chow；John G. Watson；Feng Wu；Hua Li

NH3 ； NH4(superscript +) ； Aerosol, Agricultural activity

Aerosol and Air Quality Research

9卷2期（2009 / 06 / 01）

277 - 289

英文

Continuous measurements of atmospheric ammonia (NH3) between April 2006 and April 2007 were conducted at an urban site and a suburban site in Xi'an, northwest China. NH3 was collected using Ogawa passive samplers every sixth day. At the same time, NH4(superscript +) in fine particles was collected using battery-powered mini-volume samplers. The annual average concentrations of NH3 were 12.9 μg/m^3 and 14.1 μg/m^3, at the urban and suburban sites, respectively. The NH3 concentrations reached a maximum (~22.8-35.3 μg/m^3) in June and July and were minimum (~3.0-4.7 μg/m^3) in December, which was closely linked with NH3 volatilization under different ambient temperatures. The seasonal variation in NH3 was summer ＞ spring ＞ autumn ＞ winter at both sites, which may be ascribed to the impact of biological emission sources such as agricultural activity. NH3 and NH4(superscript +) aerosol concentrations were weakly correlated, implying that gas-particle reactions are influenced by many factors such as sources, meteorology and removal. Average NH3/NH4(superscript +) ratios varied from 0.1 to 25.3, with an annual average of 4.0. High NH3 concentrations at Xi'an had a significant influence on atmospheric acidity and the formation of secondary NH4(superscript +) aerosol.