Role of ambient ammonia in particulate ammonium formation at a rural site in the North China Plain

Abstract

<p><strong>Abstract.</strong> The real-time measurements of NH<sub>3</sub> and trace gases were conducted, in conjunction with semi-continuous measurements of water-soluble ions in PM<sub>2.5</sub> at a rural site in the North China Plain (NCP) from May to September 2013 in order to better understand of chemical characteristics for ammonia, and of the impact on formation of secondary ammonium aerosols in the NCP. Extremely high NH<sub>3</sub> and NH<sub>4</sub><sup>+</sup> concentrations were observed after a precipitation event within 7–10 days following urea application. Elevated NH<sub>3</sub> levels coincided with elevated NH<sub>4</sub><sup>+</sup>, suggesting that NH<sub>3</sub> plays a vital role in enhancing particulate ammonium. For the sampling period, the average oxidation/conversion ratios for SO<sub>4</sub><sup>2−</sup> (SOR), NO<sub>3</sub><sup>−</sup> (NOR) and NH<sub>4</sub><sup>+</sup> (NHR) were estimated to be 64 %, 24 % and 30 %, respectively. The increased NH<sub>3</sub> concentrations mainly from agricultural activities, coincided with the prevailing meteorological conditions could promote the secondary transformation, resulting in higher hourly SOR, NOR and NHR. The concentrations of NH<sub>3</sub>, NH<sub>4</sub><sup>+</sup>, and NHR had clear diurnal variations, which could be attributed to their sources, meteorological conditions, and formation mechanisms. The back trajectory analysis indicates that the transport of air masses from the North China Plain region contributed to the atmospheric NH<sub>3</sub> variations, and both regional sources and long-distance transport from southeast played important roles in the observed ammonium aerosol at rural site in the NCP. The findings of this study are expected to facilitate developing future NH<sub>3</sub> emission control policies for the North China Plain.</p>

Parameterization of heterogeneous reaction of SO2 to sulfate on dust with coexistence of NH3 and NO2 under different humidity conditions

“…According to the distribution of observed concentrations during haze in China, the threshold for the NH 3 coexistence condition is set as 15 ppb (Meng et al, 2018), and the threshold concentration for NO 2 coexistence is set as 30 ppb in this study. The times when NO 2 and NH 3 are below their thresholds are few (<5%) (See Fig.S3).…”

“…High emission of NH 3 and NO 2 in China and other developing countries (Wang et al, 2016) may result in significant synergistic effects in heterogeneous formation of sulfate and contribute to haze formation (Fu et al, 2017;He et al, 2014). Abundance of NH 3 (maximum concentration higher than 100 ppb) (Meng et al, 2018;Pan et al, 2012Pan et al, , 2018Wen et al, 2015) and strong correlations between the peak levels of fine particles and large increases in NH 3 concentrations (Liu et al, 2015a;Ye et al, 2011) were usually observed in the heavy haze condition. Therefore, investigating the heterogeneous reaction of SO 2 at different RHs and the coexistence of NH 3 is important to improve the simulation of SO 4 2− in air quality models.…”

Temporal characteristics and vertical distribution of atmospheric ammonia and ammonium in winter in Beijing

“…1). Meng et al (2018) reported that there was a lag in the results of the LGR ammonia analyzer, and hourly average could reduce this influence. NH 3 measured by the LGR ammonia analyzer tracked well with the measurement at 102 m on the BMT from an open path quantum cascade-laser (QCL)-based NH 3 sensor (Aerodyne Research Inc., USA) using a 3 m fast-response counter-flow impactor inlet, with R 2 = 0.70, slope = 0.89 ( Fig.…”

The Physico-Chemical Quality of Streams and Channels Draining into River Rwizi, South Western Uganda

“…This is attributed to the uniform generation of particulate matter in all the stream sections. There are a lot of agricultural activities (crop agriculture, livestock rearing, fish rearing) in the upstream and midstream sections of the river[15] [38] which deposit high amounts of suspended particles in the river while wastes generated from Mbarara municipality are the main contributors of suspended particles in the downstream of the river.…”