Ammonia (NH_3) is an important alkaline gas and precursor of secondary aerosols or fine particulate matter (such as PM_(2.5)) in the atmosphere. NH_3 is mainly from agricultural sources (ammonium based N fertilizers and livestock wastes). However, the contribution of urban and industrial sources to atmospheric NH_3 has become an environmental concern with accelerated urbanization and industrialization in China. Therefore this paper studied the spatial-temporal variability of NH_3 and its applications in environmental protection at different sites near various emission sources in Beijing using ALPHA passive samplers during April 2010 and march 2011. The annual mean NH_3 concentration can be classified to three levels, the highest NH_3 concentrations were found at fatting house at a swine farm site (2379 mug/m~3) and a waste water pool at a refuge landfill site (2801 mug/m~3). The second high concentrations occurred at a manure pit nearby a swine farm site (205 mug/m~3) and anaerobic heat workshop of refuge landfill site (198 mug/m~3). The lowest NH_3 concentrations were observed at the avenue beside the gate of China Agricultural University (15.2 mug/m~3), working area of refuge landfill site (11.1 mug/m~3) and cropland at Shangzhuang site (7.8 mug/m~3). Due to garbage components, temperature and precipitation, the NH_3 concentrations near raw water pool of refuge landfill varied at very large scope (137-6581 mug/m~3) during the sampling period. As affected by the open and close of the window, the concentrations of fattening house of swine farm were highest in winter, and lowest in summer, which was opposite to the variation at manure pit. The NH_3 concentrations were highest at in summer, and lowest in winter, which may be ascribed to the high concentration of particulate matter (PM_(2.5)) near traffic source, and high NH_3 volatilization with high temperature in summer. Due to the fertilization mode and change of air temperature, the NH_3 concentrations on the farmland revealed the same seasonal pattern as the traffic source. Our results suggest that fattening house of swine farm and raw water pool of refuge landfill were very important NH_3 emission sources compared with fertilized cropland, based on emission densities. Besides, the concentration near the avenue was twice as high as that near the cropland, suggesting that the traffic exhausts not only contribute to NO_x emission, but also to NH_3 emission, which was largely related to motor vehicles with catalytic converters.