Collection of Nitrogen Dioxide for Nitrogen and Oxygen Isotope Determination─Laboratory and Environmental Chamber Evaluation.

The family of atmospheric oxides of nitrogen, NO (e.g., nitrogen oxides (NO) + nitric acid (HNO) + nitrous acid (HONO) + peroxyacetyl nitrate (PAN) + particulate nitrate (pNO) + other), have an influential role in atmospheric chemistry, climate, and the environment.

Speciated Collection of Nitric Acid and Fine Particulate Nitrate for Nitrogen and Oxygen Stable Isotope Determination.

Stable isotopic composition of atmospheric nitrate (nitric acid (HNO) + particulate nitrate (pNO)) provides a higher-order dimensional analysis of critical atmospheric components, enabling a process-level understanding of precursor emissions, oxidation chemistry, aerosol acidity, and depositional patterns. Current methods have not been evaluated for their ability to accurately speciate and determine nitrogen (δN) and oxygen (δO and ΔO) isotope compositions for gaseous and particle phases. Suitability of a denuder-filter sampling system for the collection of speciated HNO and pNO for off-line concentration and isotopic determination was tested using both laboratory and field collections.

Selective Collection of Particulate Ammonium for Nitrogen Isotopic Characterization Using a Denuder-Filter Pack Sampling Device.

Nitrogen stable isotope analysis (δN) of particulate ammonium (NH) may provide additional constraints on this critical component of fine particulate matter; however, no previous collection method has been verified for its ability to accurately and precisely characterize δN(NH). This is a critical point due to the difficulty of quantitative NH collection and possible sampling artifacts. Here, we report on δN(NH) precision using an established denuder-filter pack combination with two filter configurations including (1) a nylon filter plus an acid-impregnated cellulose filter and (2) an acid-impregnated glass fiber filter for NH collection in both laboratory-controlled environments and ambient air samples.