AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Laboratory Measurements of Total Suspended Organic Carbon: Technique Development and Application to Chamber SOA Photo-Oxidation Experiments
JOSHUA MOSS, Jesse Kroll, Stephen Duncan, MIT
Abstract Number: 516 Working Group: Instrumentation and Methods
Abstract Secondary organic aerosol (SOA) comprises a major fraction of particulate matter in the atmosphere and is principally formed via the oxidation of volatile organic compounds (VOCs). Laboratory chamber studies aimed at elucidating the underlying chemical mechanisms pertaining to SOA formation and evolution have been unable to enumerate all organic species produced in SOA-forming reactions, largely due to the extreme chemical complexity of the system and poorly constrained depositional losses to chamber walls and instrument inlets. While particle wall losses are relatively easily accounted for, vapor depositional losses remain poorly constrained and difficult to predict, varying from species to species and even from chamber to chamber. Additionally, these vapor losses may also decrease SOA yields in chamber studies and could lead to profound differences in the chemistry observed in chambers from that observed in the atmosphere. Here we describe the development and deployment of an apparatus to measure Total Suspended Carbon (TSC) for use in laboratory studies of SOA formation and aging to both directly quantify vapor wall losses and provide a new constraint on the extent of “carbon balance” measured in atmospheric oxidation studies. This work builds on an established technique for TSC measurement, involving the use of a platinum catalyst to fully oxidize VOCs to carbon dioxide which is directly quantifiable. Coupling this new apparatus to a suite of analytical instruments to measure gas- and particle-phase organic species will yield novel insight into chamber wall losses. Numerous characterization studies, centered around chamber SOA photo-oxidation experiments, will comprise the bulk of the work presented and will draw novel connections between the “bottom-up” measurements obtained from the suite of instruments and the “top-down” constraint imposed by our TSC apparatus. These comparisons will allow us to assess the extent of carbon balance obtained from and the speciation capabilities of our suite of instruments.