Abstract
Abstract. The atmospheric concentrations of gaseous ammonia have been measured during two field campaigns in the winter and in the summer of 2007 at Beijing (China). These measurements were carried out by means of diffusion annular denuders coated with phosphorous acid. The results were discussed from the standpoint of temporal and diurnal variations and meteorological effects. The daily average NH3 concentrations were in the range of 0.20–44.38 μg/m3 and showed regular temporal variations with higher concentrations during summer and with lower during winter. The temporal trends seemed to be largely affected by air temperature because of agricultural sources. No diurnal variability was observed for gaseous NH3 levels in both winter and summer seasons. The highest ammonia value of 105.67 μg/m3 was measured in the early morning during the summer period when stable atmospheric conditions occurred. The diurnal winter and summer trends of ammonia showed a weak dependence on the air temperature and they were affected nearly by wind direction suggesting regional and local source influences. Ammonia was also correlated with the atmospheric mixing in the boundary layer, and, with NOx, CO and PM2.5 air concentrations supporting the hypothesis that the traffic may be also an important source of ammonia in Beijing.
Highlights
Gaseous ammonia (NH3) is the third most abundant nitrogen containing compound and is the primary alkaline trace gas in the atmosphere
NH3 exhibited a distinct and significant (p < 0.001) temporal variation with higher concentrations in summer than in winter (Fig. 1). This difference in NH3 concentrations has been observed by other papers and is in agreement with the temperature dependence of NH3 emissions from animal waste, natural and fertilized soils, and vegetations (Langford and Fehsenfeld, 1992; Langford et al, 1992; Yamamoto et al, 1995; Asman et al, 1998; Lefer et al, 1999; Aneja et al, 2000; Robarge et al, 2002; Pryor et al, 2001), which are at low values during winter
Atmospheric ammonia concentrations were highest in summer at Beijing site
Summary
Gaseous ammonia (NH3) is the third most abundant nitrogen containing compound and is the primary alkaline trace gas in the atmosphere. According to studies of the ammonia level in China, in Beijing, some research has shown that the concentration of secondary particles are higher in the winter probably due to the high SO2 emissions and low wind speed, which aid the formation of SO24−. Such systems are designed with a vertically positioned denuder tube to eliminate the sedimentation of particles (Possanzini et al, 1983; Allegrini et al, 1987, 1999; Febo et al, 1989; Perrino et al, 1990) This sampling technique is able to accurately determine gaseous ammonia and particulate ammonium without disturbing the partition existing in the atmosphere at the time of the sampling and without mutual interferent (Perrino et al, 1999, 2002). The study is a part of a Sino-Italian collaboration project (Blue Sky of Beijing: Research on Regional Air Pollution Project) and part of the international collaborative research CAREBEIJING (Campaigns of Air Quality Research in Beijing and Surrounding Region)
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