Characteristics of atmospheric ammonia over Beijing, China

Abstract

Continuous measurements of atmospheric ammonia (NH<sub>3</sub>) were conducted using Ogawa passive samplers from February 2008 to July 2010 at an urban site and from January 2007 to July 2010 at a rural site in Beijing, China. NH<sub>4</sub><sup>+</sup> in fine particles was also collected at the rural site during 2008–2009. The field comparison between the Ogawa passive samplers and an active analyzer for NH<sub>3</sub> conducted at the urban site assures the quality and accuracy of the measurements. The concentrations of NH<sub>3</sub> at the urban site ranged from 0.7 to 85.1 ppb, with the annual average of 18.5 ± 13.8 and 23.5 ± 18.0 ppb in 2008 and 2009, respectively. The NH<sub>3</sub> concentrations at the rural site were lower than those at urban site, and varied from 0.8 to 42.9 ppb, with the annual average of 4.5 ± 4.6, 6.6 ± 7.0 and 7.1 ± 3.5 ppb in 2007, 2008 and 2009, respectively. The data showed marked seasonal variations at both sites. The results emphasized traffic to be a significant source of NH<sub>3</sub> concentrations in winter in urban areas of Beijing. This was illustrated by the strong correlations of NH<sub>3</sub> with the traffic related pollutants (NO<sub>x</sub> and CO) and also by the bimodal diurnal cycle of NH<sub>3</sub> concentrations that was synchronized with traffic. Similar patterns were not observed during the summer, suggesting other non-traffic sources became more important. At the rural site, the daily NH<sub>4</sub><sup>+</sup> concentrations ranged from 0.10 to 36.53 μg m<sup>−3</sup>, with an average of 7.03 μg m<sup>−3</sup> from June 2008 to December 2009. Monthly NH<sub>3</sub> were significantly correlated with NH<sub>4</sub><sup>+</sup> concentrations. Average monthly NH<sub>3</sub>/NH<sub>4</sub><sup>+</sup> ratios varied from 0.13 to 2.28, with an average of 0.73. NH<sub>4</sub><sup>+</sup> in PM<sub>2.5</sub> was primarily associated with SO<sub>4</sub><sup>−2</sup> at the rural site

Persistent sensitivity of Asian aerosol to emissions of nitrogen oxides

“…Over South Asia and to a lesser extent over East Asia, NH 3 retrieved from the TES satellite instrument tends to be higher than simulated with a different GEOS-Chem simulation that had higher, yet aseasonal, NH 3 Asian emissions [Shephard et al, 2011]. Meng et al [2011] indicate that there is a large urban NH 3 source in Beijing that may be underestimated. Thus, the sensitivity of inorganic aerosol to NO x emissions could be even larger than found here.…”

Isotopic constraints on heterogeneous sulphate production in Beijing haze

“…So we also predicted the AWC, pH and I s in stable mode (assuming that bulk aerosols crystallize 187 once saturation is exceeded), which is consistent with Wang et al(2016).The input of observed inorganic ion concentrations 188 and meteorological parametersare summarized in Table S4. Since gaseous NH 3 was not measured in our campaign, we used 189 the empirical equation NH 3 (ppb) = 0.34×NO X (ppb)+0.63, derived from observations of Meng et al(2011) in Beijing winter,190 to estimate the NH 3 concentrations. We used NO 2 concentrations instead of NO X as input due to the lack of NO X 191 observations in our study, which would give a lower end of the NH 3 concentrations.…”

Continuous Measurement of Ambient Aerosol Liquid Water Content in Beijing

“…Strict emission limits on coal burning power plants and factories and vehicle emissions, and control of factories on emissions of SO 2 and NO x are measures put in place by the government that have resulted in reduction of the corresponding particulate components. However, very little has been done on the reduction of ammonia emissions, which continue in the rising (Meng et al, 2011;Wang et al, 2011), and reflects on the alkalinity that aerosol in Beijing shows. A comparison of ACSM aerosol mass and Acidity ratio shows how the aerosol is predominately alkaline during the sampling period, particularly for low aerosol masses (i.e., clean period) (Fig.…”