Chemical characterization of biogenic secondary organic aerosol generated from plant emissions under baseline and stressed conditions: inter- and intra-species variability for six coniferous species

摘要

The largest global source of secondary organic aerosol (SOA) in the atmosphere isderived from the oxidation of biogenic emissions. Plant stressors associatedwith a changing environment can alter both the quantity and composition ofthe compounds that are emitted. Alterations to the biogenic volatile organic compound (BVOC) profilecould impact the characteristics of the SOA formed from those emissions.This study investigated the impacts of one global change stressor, increasedherbivory, on the composition of SOA derived from real plant emissions.Herbivory was simulated via application of methyl jasmonate (MeJA), a proxycompound. Experiments were repeated under pre- and post-treatment conditionsfor six different coniferous plant types. Volatile organic compounds (VOCs) emitted from the plants wereoxidized to form SOA via dark ozone-initiated chemistry. The SOAchemical composition was measured using a Aerodyne high-resolution time-of-flightaerosol mass spectrometer (HR-AMS). The aerosol mass spectraof pre-treatment biogenic SOA from all plant types tended to be similar withcorrelations usually greater than or equal to 0.90. The presence of astressor produced characteristic differences in the SOA mass spectra.Specifically, the following were identified as a possible biogenicstress AMS marker with the corresponding HR ion(s) shown in parentheses: 31 (CHO), 58 (CHO,CHO), 29 (CH), 57(CHO), 59 (CHO,CHO), 71 (CHO,CHO), and 83 (CHO). The firstaerosol mass spectrum of SOA generated from the oxidation of the plantstress hormone, MeJA, is also presented. Elemental analysisresults demonstrated an O : C range of baseline biogenic SOA between 0.3 and 0.47.The O : C of standard MeJA SOA was 0.52. Results presented herecould be used to help identify a biogenic plant stress marker in ambientdata sets collected in forest environments.