Abstract
ABSTRACT Ambient air pollution caused by fine particulate matter (PM) and trace gases is a pressing topic as it affects the vast majority of the world's population, with a particularly heavy influence in densely populated urban environments. Alongside nitrogen oxides (NOx) and PM, ammonia (NH3) is also a relevant air pollutant due to its role as a precursor of particulate ammonium. This is a study about the short-term temporal dynamics of urban NH3 concentrations in Munster, northwest Germany, the role of road traffic and agriculture as NH3 sources and about the importance of ammonia for secondary particle formation (SPF). The NH3 mixing ratio was rather high (mean: 17 ppb) compared to other urban areas and showed distinct diurnal maxima around 10 a.m. and during the night at 9 p.m. The main source for ammonia in Munster was agriculture, but road traffic also contributed through local emissions from vehicle catalysts. NH3 from surrounding agricultural areas accumulated in the nocturnal boundary layer and contributed to SPF in the city center. Modeled emissions of NH3 as estimated by the Handbook for Emission Factors in combination with traffic counts were in the same magnitude for NH3. The size-resolved chemical composition of inorganic ions in PM10 was dominated by NH4+ (8.66 µg m–3), followed by NO3– (3.89 µg m–3), SO42– (1.58 µg m–3) and Cl– (1.33 µg m–3). Particles in the accumulation range (diameter: 0.1–1 µm) showed the highest inorganic ion concentrations. The ammonium neutralization index J (111%) indicated an excess of NH4+ leading to mostly alkaline PM. High ammonia emissions from surrounding agricultural areas combined with large amounts of NOx from road traffic play a crucial role for SPF in Munster.
Highlights
A vast majority of the world's population (91%) lives in locations that exceed the WHO air quality guidelines (WHO, 2016) with poor air quality responsible for one in every nine premature deaths in 2012 (WHO, 2016)
This study aims 1) to identify ammonia emission sources at an urban site on different temporal scales from a few seconds to one day, 2) to evaluate the role of road traffic as an urban ammonia source using information from a real-world vehicle fleet combined with plume peak correlation of traffic-related trace gases with NH3 and 3) to evaluate the role of ammonia in secondary particle formation (SPF) by evaluating the chemical composition of size-resolved particulate matter (PM) samples
three-way catalytic converters (TWC) systems of gasoline vehicles and selective catalytic reduction (SCR) catalysts of diesel engines are responsible for these local emissions of NH3
Summary
A vast majority of the world's population (91%) lives in locations that exceed the WHO air quality guidelines (WHO, 2016) with poor air quality responsible for one in every nine premature deaths in 2012 (WHO, 2016). Urban areas are especially prone to high levels of pollutants with an increasing frequency of air pollution episodes in many cities (WHO, 2016). This is due to the fact that the density of anthropogenic emission sources is higher in urban areas compared to rural regions. Air quality monitoring mainly focuses on particulate matter (PM), tropospheric ozone (O3), and oxygenated N-, S-, and C-compounds including nitrogen oxides (NO + NO2 = NOx), sulfur dioxide (SO2), and carbon monoxide (CO), while ammonia (NH3), a reduced N-compound, is often neglected in urban air pollution monitoring and evaluation. Ammonia plays a special role in atmospheric air pollution as the main alkaline gas that neutralizes acidic compounds in the troposphere (Perrino et al, 2002; Ferrara et al, 2012), leading to the formation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
