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Characterization of organic nitrogen in aerosols at a forest site in the southern Appalachian Mountains.

ABSTRACT: This study investigates the composition of organic particulate matter in PM2.5 in a remote montane forest in the southeastern US, focusing on the role of organic nitrogen (N) in sulfur-containing secondary organic aerosol (nitrooxy-organosulfates) and aerosols associated with biomass burning (nitro-aromatics). Bulk water-soluble organic N (WSON) represented ~ 14% w/w of water-soluble total N (WSTN) in PM2.5 on average across seasonal measurement campaigns conducted in the spring, summer, and fall of 2015. The largest contributions of WSON to WSTN were observed in spring (~ 18% w/w) and the lowest in the fall (~ 10% w/w). On average, identified nitro-aromatic and nitrooxy-organosulfate compounds accounted for a small fraction of WSON, ranging from ~ 1% in spring to ~ 4% in fall, though were observed to contribute as much as 28% w/w of WSON in individual samples that were impacted by local biomass burning. The highest concentrations of oxidized organic N species occurred during summer (average of 0.65 ng N m-3) along with a greater relative abundance of higher-generation oxygenated terpenoic acids, indicating an association with more aged aerosol. The highest concentrations of nitro-aromatics (e.g., nitrocatechol and methyl-nitrocatechol), levoglucosan, and aged SOA tracers were observed during fall, associated with aged biomass burning plumes. Nighttime nitrate radical chemistry is the most likely formation pathway for nitrooxy-organosulfates observed at this low NO x site (generally < 1 ppb). Isoprene-derived organosulfate (MW216, 2-methyltetrol derived), which is formed from isoprene epoxydiols (IEPOX) under low NO x conditions, was the most abundant individual organosulfate. Concentration-weighted average WSON / WSOC ratios for nitro-aromatics + organosulfates + terpenoic acids were 1 order of magnitude lower than the overall aerosol WSON / WSOC ratio, indicating the presence of other uncharacterized higher-N-content species. Although nitrooxy-organosulfates and nitro-aromatics contributed a small fraction of WSON, our results provide new insight into the atmospheric formation processes and sources of these largely uncharacterized components of atmospheric organic N, which also helps to advance the atmospheric models to better understand the chemistry and deposition of reactive N.

SUBMITTER: Chen X

PROVIDER: S-EPMC7377252 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Characterization of organic nitrogen in aerosols at a forest site in the southern Appalachian Mountains.

Chen Xi X Xie Mingjie M Hays Michael D MD Edgerton Eric E Schwede Donna D Walker John T JT

Atmospheric chemistry and physics 20180501 9

This study investigates the composition of organic particulate matter in PM2.5 in a remote montane forest in the southeastern US, focusing on the role of organic nitrogen (N) in sulfur-containing secondary organic aerosol (nitrooxy-organosulfates) and aerosols associated with biomass burning (nitro-aromatics). Bulk water-soluble organic N (WSON) represented ~ 14% w/w of water-soluble total N (WSTN) in PM2.5 on average across seasonal measurement campaigns conducted i ...[more]

PMID: 32704249

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Project description:The eastern subterranean termite, Reticulitermes flavipes, currently inhabits previously glaciated regions of the northeastern U.S., as well as the unglaciated southern Appalachian Mountains and surrounding areas. We hypothesized that Pleistocene climatic fluctuations have influenced the distribution of R. flavipes, and thus the evolutionary history of the species. We estimated contemporary and historical geographic distributions of R. flavipes by constructing Species Distribution Models (SDM). We also inferred the evolutionary and demographic history of the species using mitochondrial (cytochrome oxidase I and II) and nuclear (endo-beta-1,4-glucanase) DNA sequence data. To do this, genetic populations were delineated using Bayesian spatial-genetic clustering, competing hypotheses about population divergence were assessed using approximate Bayesian computation (ABC), and changes in population size were estimated using Bayesian skyline plots. SDMs identified areas in the north with suitable habitat during the transition from the Last Interglacial to the Last Glacial Maximum, as well as an expanding distribution from the mid-Holocene to the present. Genetic analyses identified three geographically cohesive populations, corresponding with northern, central, and southern portions of the study region. Based on ABC analyses, divergence between the Northern and Southern populations was the oldest, estimated to have occurred 64.80 thousand years ago (kya), which corresponds with the timing of available habitat in the north. The Central and Northern populations diverged in the mid-Holocene, 8.63 kya, after which the Central population continued to expand. Accordingly, phylogeographic patterns of R. flavipes in the southern Appalachians appear to have been strongly influenced by glacial-interglacial climate change.Open research badgesThis article has been awarded Open Materials, Open Data Badges. All materials and data are publicly accessible via the Open Science Framework at https://doi.org/10.5061/dryad.5hr7f31.

Dataset Information

Characterization of organic nitrogen in aerosols at a forest site in the southern Appalachian Mountains.

Publications

Characterization of organic nitrogen in aerosols at a forest site in the southern Appalachian Mountains.

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