Using Molecular Tracers to Understand BVOC Interactions with Anthropogenic Pollutants in the Southeast U.S. and Amazonia
Abstract
Biogenic volatile organic compounds (BVOCs) are the dominant source of reduced carbon to the atmosphere. The SOAS 2013 and GoAmazon 2014/15 campaigns were designed to investigate how anthropogenic pollution alters the fate of BVOCs. We used speciated organic chemical measurements to observe the major BVOCs (isoprene, monoterpenes, sesquiterpenes) and many of their oxidation products, ranging from volatile (using in-situ GC-MS and PTR-ToF-MS) to semi-volatile gas and particle phase compounds (using in-situ SV-TAG, offline GCxGC-VUV/EI-HRTOFMS, and other techniques). We use these speciated chemical observations of nearly 1000 molecular tracers with measurements made by collaborating groups to investigate their phase partitioning, contributions to secondary organic aerosol (SOA), and mechanisms controlling their transformations. Major findings include that polyols from isoprene oxidation contributed 8% to 15% on average to organic aerosol mass, but with different chemical compositions in the southeast US and Amazon, indicating differences in chemical transformation pathways forming SOA. We also observed substantial gas-phase concentrations of polyols, and that the gas-particle partitioning of approximately 100 known and newly observed oxidation products is not well explained by environmental factors (e.g. temperature). Compounds having high vapor pressures have higher particle fractions than expected from absorptive equilibrium partitioning models, suggesting many commonly measured biogenic oxidation products can be bound in low-volatility mass (e.g. accretion products, inorganic-organic adducts) that decomposes to individual compounds on analysis. Correlation of isoprene derived polyols, and BVOC organosulfates, with aerosol sulfate was observed across all three campaigns, demonstrating a strong link between anthropogenic pollution and the fate of BVOCs forming SOA. We also observed sesquiterpenes and diterpenes, and through synthesizing authentic standards, we quantified both gas- and particle-phase products from beta-caryophyllene oxidation in the ambient air. Finally, we report a wide suite of newly observed tracers that correlate with known isoprene, monoterpene, and sesquiterpene oxidation products.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.A41M..01G
- Keywords:
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- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 3355 Regional modeling;
- ATMOSPHERIC PROCESSESDE: 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES