Continuous flow hygroscopicity-resolved relaxed eddy accumulation (Hy-Res REA) method of measuring size-resolved sodium chloride particle fluxes
Meskhidze, N., T. Royalty, B. Phillips, K. Dawson, M. Petters, R. Reed, J. Weinstein, D. Hook, AND R. Wiener. Continuous flow hygroscopicity-resolved relaxed eddy accumulation (Hy-Res REA) method of measuring size-resolved sodium chloride particle fluxes. AEROSOL SCIENCE AND TECHNOLOGY. Taylor & Francis, Inc., Philadelphia, PA, 52(4):433-450, (2018).
Aerosols play an important role in controlling the Earth’s radiation balance, cloud formation, cloud microphysical properties, biogeochemical cycling of nutrients, tropospheric chemistry and have been increasingly recognized for their adverse effects on air quality and human health. Aerosols arise from both natural sources and anthropogenic activities; therefore, to characterize relevant environmental effects, it becomes increasingly important to accurately quantify both number and mass concentrations of aerosols of different origin. Moreover, the characterization of both emission and deposition fluxes of aerosols is important for understanding the life cycle of aerosols and their potential to contribute to the Earth’s energy balance.
The accurate representation of aerosols in climate models requires direct ambient measurement of the size- and composition-dependent particle production fluxes. Here, we present the design, testing, and analysis of data collected through the first instrument capable of measuring hygroscopicity-based, size-resolved particle fluxes using a continuous-flow Hygroscopicity-Resolved Relaxed Eddy Accumulation (Hy-Res REA) technique. The Hy-Res REA system used in this study includes a 3D sonic anemometer, two fast-response solenoid valves, two condensation particle counters, a scanning mobility particle sizer, and a hygroscopicity tandem differential mobility analyzer. The different components of the instrument were tested inside the US Environmental Protection Agency's Aerosol Test Facility for sodium chloride and ammonium sulfate particle fluxes. The new REA system design does not require particle accumulation, and therefore avoids the diffusional wall losses associated with long residence times of particles inside the air collectors of traditional REA devices. A linear relationship was found between the sodium chloride particle fluxes measured by eddy covariance and REA techniques. The particle detection limit of the Hy-Res REA flux system is estimated to be ∼3 × 105 m−2 s−1. The estimated sodium chloride particle classification limit, for the mixture of sodium chloride and ammonium sulfate particles of comparable concentrations, is ∼6 × 106 m−2 s−1.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
EXPOSURE METHODS & MEASUREMENT DIVISION