Use of Continuous Measurements of Integral Aerosol Parameters to Estimate Particle Surface Area

While surface area is one of the most important atmospheric aerosol properties in health effects, methods for online measurement of surface area are not widely available and/or require complex operations. In this paper, we describe an integrated measurement method that can continuously monitor the total surface area, as well as the total number and volume, of atmospheric aerosols. Three integral aerosol sensors - (i) a condensation particle counter (CPC) for number concentration measurement, (ii) a mass concentration monitor (MCM) for mass concentration measurement, and (iii) an electrical aerosol detector (EAD) for current measurement of charged aerosol - are used in this study. Signals from the three sensors are converted into a lognormal size distribution by minimizing the difference between the measured signals and the theoretical values based upon a size distribution model, the instrument calibration, and its theoretical responses. Results from a 20 day continuous sampling period show that the calculated total surface area from integrated measurement correlates well with that of particle sizing measurement. The calculated lognormal size distribution parameters between the two methods have similar values. These results suggest that the integrated measurement method is feasible to continuously measure total number, surface area, and volume concentrations. As the integrated measurement method can yield results in near real time, it can be used for online measurement of atmospheric aerosols.