Organic Nitrogen Concentrations and Species in Aerosol and Precipitation Samples from the Rocky Mountains

摘要

In PM_(2.5) aerosol samples WSON concentrations were slightly higher than nitrate. Concentrations ranged from 0.05 μg N/m~3 to 0.6 μg N/m~3. The highest ON concentrations were measured when the sampling sites were impacted by smoke. ON contributed 12-48% of total water soluble nitrogen measured in aerosol, with an average of 18% in RMNP and 29% in GTNP. In both GTNP and RMNP ammonium was the dominant nitrogen species. Dry deposition of PM_(2.5) WSON contributed 1% to total reactive nitrogen deposition in RMNP and GTNP. In precipitation samples, organic nitrogen contributed an average of 23% and 27% to measured total nitrogen, in RMNP and GTNP, respectively. Wet deposition of ON contributed similar fractions in RMNP (18%) and GTNP (16%) to total reactive nitrogen deposition (including the dry deposition pathways). A variety of compounds were identified including nitrophenols and organosulfur-nitrogen compounds in the negative mode and amides and amines in the positive mode. The organosulfur-nitrogen compounds appear to be nitric acid and sulfuric acid esters of monoterpene oxidation products. Significantly more compounds were identified in the positive ion mode but further analysis to elucidate the structures is necessary to identify the type of compounds present.