Portable, Low-cost Samplers for Distributed Sampling of Aerosols and Reactive Gases

JAMES HURLEY, Alejandra Caceres, Ksenia Onufrieva, Gabriel Isaacman-VanWertz, Virginia Tech

     Abstract Number: 255
     Working Group: Instrumentation and Methods

Abstract
At present, field measurements of gas- and particle-phase reactive organic compounds are often performed using large, expensive, sophisticated instrumentation such as mass spectrometers. Such instrumentation is logistically challenging to deploy and requires skilled operators for maintenance and analysis. Alternatively, filter- and/or adsorbent-based sampling approaches allow offline collection and are comparatively simple. However, collection of samples requires significant operator effort and most available samplers are insufficiently portable, cheap, and/or flexible to enable distributed sampling across spatial or temporal scales. For example, existing tools generally lack the ability to synchronize the timing of multiple samples, may not monitor and/or control sample flow to provide identical sampling conditions, and may not be weatherproof and solar powered for long-term outdoor deployment. We present and validate here a network of distributed samplers for addressing a range of scientific questions regarding the spatial and temporal distributions of reactive organic compounds and aerosol precursors. Over a dozen low-cost (~$500 in materials) samplers have been built and validated in laboratory and field studies. Air is sampled at a known and controlled flow rate through a filter cartridge that can be used for particle sampling or, in the case of gas sampling, removal of oxidants using a sodium thiosulfate impregnated filter. Gases are sampled downstream of the filter on an adsorbent cartridge for subsequent analysis by gas chromatography-mass spectrometry (GC-MS). Utility and validation of the samplers is demonstrated by their deployment to: (a) locate sources of reactive gases by mobile sampling across a spatial domain, (b) measure vertical gradients of aerosol precursors through contemporaneous synchronized sampling at multiple heights, (c) measure trends in atmospheric composition through long-term intermittent deployment, and (d) particle sampling at multiple outdoor sites simultaneously. Improvements to increase flow rates and enhance usability for particle sampling will be discussed.