Collection of Ammonia for High Time-Resolved Nitrogen Isotopic Characterization Utilizing an Acid-Coated Honeycomb Denuder

Nitrogen stable isotope analysis (delta N-15) of ammonia (NH3) has shown potential to be a useful tool for characterizing emission sources and sink processes. However, to properly evaluate NH3 emission sources and sink processes under ambient conditions, it is necessary to collect and characterize the chemical speciation between NH3 and particulate ammonium (pNH(4)(+)), together referred to as NHx Current NH3 collection methods have not been verified for their ability to accurately characterize delta N-15-NH3 and/or provide necessary chemical speciation (i.e., delta N-15-NH3 and delta N-15-NH4). Here, we report on the suitability of an established collection device that can provide NHx speciation, an acid-coated (2% citric acid (w/v) + 1% glycerol (w/v) in 80:20 methanol to water solution) honeycomb denuder (HCD) with a downstream filter pack housed in the ChemComb Speciation Cartridge (CCSC), for characterizing delta N-15-NH3 under a variety of laboratory-controlled conditions and field collections. The collection method was tested under varying NH3 concentration, relative humidity, temperature, and collection time at a flow rate of 10 L per minute (LPM). The acid-coated HCD collection device and subsequent chemical processing for delta N-15-NH3 analysis is found to have excellent accuracy and precision of +/- 1.6 parts per thousand (2 sigma), with an operative capacity of similar to 400 mu g of collected NH3 for concentrations <= 207 ppb(v). This work presents the first laboratory verified method for (delta N-15-NH3 analysis and will be useful in future air quality studies.