The design and function of a device that regulates the relative humidity of an ambient aerosol sample is described. We use this RH controller upstream of MOUDI impactors to permit sampling at relative humidities in the 70-80% range. Humidity control is achieved by allowing the aerosol to approach equilibrium with a saturated salt solution. Benefits to sampling with impactors in this relative humidity range include greatly reduced bounce of fine, hygroscopic particles, minimal flow-induced sizing errors, and minimization of uncertainties in measured size distributions due to diurnal variations in relative humidity during sampling. Data from field measurements in a humid environment (Look Rock, TN) and arid environments (Las Vegas, NV and Meadview, AZ) are discussed.
Bibliographical noteFunding Information:
This research was supported by the Electric Power Research Institute (Grant No. EPRI W09116-08/W04105-01). We wish to thank the management of Desert Research Institute for providing a secure location for the measurements made at their Southern Nevada Science Center in Las Vegas, NV and in particular Drs. Marc Pitchford and Hampden Kuhns for their assistance in setting up the equipment.
- Atmospheric aerosol
- Cascade impactor
- Particle bounce
- Size distribution
- Water uptake