Speciation and Transformation of Reduced Nitrogen In The Atmosphere: A Laboratory and Field Investigation

Abdelhamid, Aroob

Graduate Thesis Or Dissertation

Speciation and Transformation of Reduced Nitrogen In The Atmosphere: A Laboratory and Field Investigation Public Deposited

Analytics

Citations

Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/sb397933n

Abstract

Reduced nitrogen has been shown to negatively affect air quality, climate, and human health. Due to increases in food production, their concentrations are expected to increase, and thus knowing their speciation, sources, sinks, and transformations in the atmosphere is important to better constrain their effects on the atmosphere. The results presented in this thesis elucidate some of the gas phase and aerosol phase transformations of these compounds.

The first study focuses on the organic nitrogen (ON) formed upon reactive uptake of ammonia into biogenic SOA in a collaboration with the University of Eastern Finland. This work showed that increasing ammonia concentration promoted greater production of a variety of ON, especially ON with larger carbon numbers. These ON were mid- to low-volatility, with initial ammonium concentrations creating low volatility compounds. Finally, this study observed that ON volatility is up to 3 orders of magnitude lower than the volatility of oxygenated compounds lacking nitrogen incorporation.

The second and third study present data from the Holistic Interaction of Shallow Clouds, Aerosols, and Land Ecosystem (HISCALE) field campaign conducted in August- September 2016 in the agricultural region of Lamont, OK, that was conducted to study the true atmospheric speciation of ambient reduced nitrogen.

For the second study, I measured ambient ions, which have been shown to promote new particle formation, and are largely composed of ON compounds. This work identified ON in the high m/z region that had been seen in previous campaigns but remained unidentified until now. These high mass-to-charge ions were seen to have a diel cycle and were sometimes correlated with neutral ammonia measurements, but their sources remain unknown.

The third study presents ambient neutral compounds measured in HISCALE. Ammonia, methylamine, and trimethylamine showed morning signal spikes that can be attributed to dew formation. Amides and imines were also measured with diel cycles that cannot be fully explained, suggesting the need for further study into the sources and fates of reduced nitrogen oxidation products.

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