AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Method Development and Field Evaluation of an Acidic Ultrafine Particle Detector
Da-Wei Wang, Hai Guo, KALAM CHEUNG, Chak K. Chan, Hong Kong Polytechnic University
Abstract Number: 693 Working Group: Instrumentation and Methods
Abstract A simple and novel method, involving the use of an iron nanofilm detector, was developed for the enumeration and size measurement of acidic ultrafine particles. To obtain morphological information of acidic and non-acidic ultrafine particles on the designed iron nanofilm detectors, both types of particles were generated and collected on the detectors. The reaction spots were examined using Atomic Force Microscopy (AFM) to establish the correlations between the diameter of the particle and the size of the reaction spot. A field evaluation was conducted in Hong Kong from September to November 2010 to validate this method. A scanning mobility particle sizer (SMPS), in tandem with a condensation particle counter (CPC), was used to measure the size-resolved number concentration of ambient particles in the range of 5.5–350 nm at 4-min scan intervals. On the other hand, a SMPS + electrostatic precipitator (ESP) system was used to collect particles smaller than 350 nm on the iron nanofilm detectors, which were subsequently examined using AFM. Measurements obtained from these two sampling methods were compared for validation. The results indicated that the particle number concentrations obtained from the AFM scanning of the exposed detectors, collected via the SMPS + ESP system, were comparable to those derived from the SMPS + CPC measurements (p > 0.05). The average geometric mean diameter of particles at peak measured by the SMPS + CPC and the detectors scanned by AFM was 52.3 ± 6.9 nm and 51.9 ± 3.1 nm, respectively, demonstrating good agreement. The influence of temperature, relative humidity, and gaseous pollutants on the surface structure of the detectors was also examined. It is concluded that the iron nanofilm detectors developed in this study could be a reliable tool for the measurement and analysis of acidic particles in a wide range of ambient conditions.