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  1. The Mt. Bachelor Observatory was frequently impacted by biomass burning smoke in 2021, an extreme forest fire year in the state of Oregon.

     
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    Free, publicly-accessible full text available March 16, 2024
  2. Abstract. Chemical ionization mass spectrometry with the nitrate reagent ion (NO3- CIMS) was used to investigate the products of the nitrate radical(NO3) initiated oxidation of four monoterpenes in laboratory chamber experiments. α-Pinene, β-pinene, Δ-3-carene, andα-thujene were studied. The major gas-phase species produced in each system were distinctly different, showing the effect of monoterpenestructure on the oxidation mechanism and further elucidating the contributions of these species to particle formation and growth. By comparinggroupings of products based on the ratios of elements in the general formula CwHxNyOz, therelative importance of specific mechanistic pathways (fragmentation, termination, and radical rearrangement) can be assessed for eachsystem. Additionally, the measured time series of the highly oxidized reaction products provide insights into the ratio of relative production andloss rates of the high-molecular-weight products of the Δ-3-carene system. The measured effective O:C ratios of reaction products wereanticorrelated with new particle formation intensity and number concentration for each system; however, the monomer : dimer ratios of products had a smallpositive trend. Gas-phase yields of oxidation products measured by NO3- CIMS correlated with particle number concentrations for eachmonoterpene system, with the exception of α-thujene, which produced a considerable amount of low-volatility products but noparticles. Species-resolved wall loss was measured with NO3- CIMS and found to be highly variable among oxidized reaction products in ourstainless steel chamber. 
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  3. null (Ed.)
  4. Abstract. Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies. NO3-BVOC reactions influence air quality, climate and visibility through regional and global budgets for reactive nitrogen (particularly organic nitrates), ozone, and organic aerosol. Despite its long history of research and the significance of this topic in atmospheric chemistry, a number of important uncertainties remain. These include an incomplete understanding of the rates, mechanisms, and organic aerosol yields for NO3-BVOC reactions, lack of constraints on the role of heterogeneous oxidative processes associated with the NO3 radical, the difficulty of characterizing the spatial distributions of BVOC and NO3 within the poorly mixed nocturnal atmosphere, and the challenge of constructing appropriate boundary layer schemes and non-photochemical mechanisms for use in state-of-the-art chemical transport and chemistry–climate models.

    This review is the result of a workshop of the same title held at the Georgia Institute of Technology in June 2015. The first half of the review summarizes the current literature on NO3-BVOC chemistry, with a particular focus on recent advances in instrumentation and models, and in organic nitrate and secondary organic aerosol (SOA) formation chemistry. Building on this current understanding, the second half of the review outlines impacts of NO3-BVOC chemistry on air quality and climate, and suggests critical research needs to better constrain this interaction to improve the predictive capabilities of atmospheric models.

     
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