A semi-continuous measurement of gaseous ammonia and particulate ammonium concentrations in PM2.5 in the ambient atmosphere

Abstract

Ammonia has a short residence time in the atmosphere and rapidly neutralizes acid gases that occur near its source, requiring a rapid measurement system for ammonia and particulate ammonium concentrations to better understand their sources, temporal variation of ammonia emissions, and the formation of secondary ammonium aerosols. A semi-continuous measurement system, consisting of a diffusion scrubber, a particle growth chamber, an air-liquid separator, and a fluorescent detector, was developed to determine both gaseous ammonia (NH 3 ) and particulate ammonium (NH 4 + ) in PM 2.5 in the ambient atmosphere of Gwangju, South Korea, during the months of March, April, July, and September of 2007. During the sampling periods, the average concentrations of ammonia and ammonium were found to be 2.33±1.29 μg/m 3 and 1.89±0.99 μg/m 3 , respectively. Although the average gaseous ammonia concentration was highest in March, the particulate ammonium concentration was higher during the warmer season, reaching 2.08±1.07 μg/m 3 and 2.32±0.94 μg/m 3 in April and July, respectively, while only 1.68±0.61 μg/m 3 in March and 1.24±0.99 μg/m 3 in September. It is proposed that the higher availability of acid species during the warmer months produced a significant amount of particulate ammonium sulfate. Diurnal fluctuation of ammonia and ammonium during the warmer months showed that their peak time occurred at approximately 10:00 am. Both ammonia and ammonium concentrations were better correlated during the warmer months than during the cooler months. Further, the data suggest that the ammonia and ammonium were measured under well dispersed conditions, and multiple sources contributed to the ammonia at the sampling site.

Surface–atmosphere exchange of ammonia over peatland using QCL-based eddy-covariance measurements and inferential modeling

“…However, increasing air temperature can also be linked to lower NH 3 concentrations, especially observed in this study in late April and early May (period IV). With higher temperature a larger amount of acidic gas or particle species are present in the atmosphere, which usually leads to reactions of ammonia to ammonium salts such as ammonium nitrate (Kim et al, 2011). We observed higher NH 3 concentrations when it was dry and/or cold, whereas rainy conditions led to lower ammonia concentration levels, which confirms findings reported by Mosquera et al (2001).…”

“…Thus, a likely reason for decreasing uptake after 15 March might have been a shift of the stomatal compensation point of the local active peatland vegetation due to higher temperatures as was shown by Milford (2004). Similar to findings in Kim et al (2011), precipitation after 15 March significantly reduced ammonia concentrations in ambient air while the ratio of wet to dry deposition probably considerably increased.…”

Investigation of factors controlling PM2.5 variability across the South Korean Peninsula during KORUS-AQ

“…The overall results of the thermodynamic calculations presented here are consistent with recent studies that found that NO x emissions enhance haze events in South Korea ( Jung et al, 2019 ), the United States ( Baasandorj et al, 2017 ), and China (e.g., Pan et al, 2016 ; Li, H., et al, 2018 ; An et al, 2019 ; Xu et al, 2019 ). The high levels of ammonia present in Seoul attributed to vehicle traffic ( Song et al, 2009 ; Phan et al, 2013 ; Link et al, 2017 ) and regional agriculture ( Kim et al, 2011 ), including rice patties ( Das et al, 2009 ), would be expected to result in NO x -limited nitrate formation during our study period. However, models should be assessed as to whether they can reproduce the nitrate production pathways here, particularly during the Transport/Haze period when ozone remains elevated at night.…”