You are here:
Speciation and Trends of Organic Nitrogen in Southeastern U.S. Fine Particulate Matter (PM2.5)
Citation:
Samy, S., J. Robinson, I. Rumsey, Johnt Walker, AND M. Hays. Speciation and Trends of Organic Nitrogen in Southeastern U.S. Fine Particulate Matter (PM2.5). JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES. American Geophysical Union, Washington, DC, 118(4):1996-2006, (2013).
Impact/Purpose:
Studies show that a significant fraction of the total N in atmospheric PM is bound in a complex organic mixture. The nutrient enrichment resulting from dry and wet N deposition is a topic of ecological concern. More accurate information about atmospheric organic N and its reactivity is provided.
Description:
Dissolved free amino acids (FAA; amino acids present in a dissolvable state) and combined AA (CAA; amino acids present in peptides, proteins, or humic complexes) in fine aerosols (PM) are investigated at a semi-urban site in the southeastern US. Detection of native (chemically underivatized) organic nitrogen (ON) compounds was achieved by liquid chromatography-mass spectrometry (LC-MS) using a quadrupole time-of-flight (Q-TOF) MS. The seven most abundant FAA (glycine > alanine = aspartic acid = arginine > glutamic acid > serine > glutamine) account for 90% of the total campaign average (11 +/- 6 ng/m-3). The mean CAA (46 +/- 21 ng m-3) value was determined to be several times higher than FAA, with the seven most abundant CAA (alanine > glycine > glutamic acid > threonine > aspartic acid > tyrosine > serine) representing 92% of the total campaign average. The impacts of meteorological conditions, atmospheric oxidant (ozone) levels, along with inorganic N (IN) trends measured during the sampling campaign are evaluated in relation to FAA and CAA concentrations and profile distributions. Compound specific correlative trends observed in relation to ozone and IN suggest atmospheric processing plays an important role in understanding atmospheric ON impacts on biogeochemical cycling. In order to better understand composition and sources of ON, accurate mass LC-MS (Q-TOF) spectra can be further evaluated for co-extracted water-soluble organic compounds (WSOC) to characterize a larger fraction of the ON mass. An examination of our ambient sample spectra followed by injections of authentic standards confirmed the presence of several N-heterocyclic compounds that were quantified in biomass burning samples previously.
