Atmospheric gaseous and particulate oxalic acids were measured from April 20-23, 1998, during the day and night at an urban site, Urawa. To suppress filter artifacts, the samples were collected with the annular denuders-filter pack sampler. The concentrations of gaseous and particulate oxalic acids ranged from 320 ng/m3 to 680 ng/m3 (86.8 pptv to 185 pptv at 25 °C) and 403 ng/m3 to 777 ng/m3, respectively. A negative filter artifact, the volatilization loss of particulate oxalic acid collected on quartz filter was estimated and corrected. The results showed that the filter artifact was not negligible and the concentration of particulate oxalic acid is remarkably underestimated due to the volatilization losses from the particulate matter collected on the filter without a back up media such as KOH-coated filter used in this study.
Many studies on particle charging theory in submicron region were reported previously, however, experimental studies on particle charging were only a few. Therefore, in this study, monodisperse Polystyrene latex (hereafter, PSL) aerosol (particle diameter, Dp = 0.401, 0.791, 1.001 μm) and polydisperse Dioctylphthalate (hereafter, DOP) aerosol (Dp = 0.8 μm) were charged by a corona type particle charger, which were charged by positive ions, and then, the amount of charge was measured by two kinds of methods; a differential mobility analyzer (hereafter, DMA) and electrical aerosol detector with an induced type Faraday cage (hereafter, EAD). In the present experiment, charging characteristics of particle, that is, the relation between number of charges on particle ions and charging time, was investigated with parameters which were particle diameter, ion concentration and strength of electric field. An extensive experiment in electric field was carried out by changing frequency of square wave of applied voltage and particle diameter on PSL. The experimental results were compared with the combined field and diffusion charging theory in the continuum region, that is, Liu-Kapadia's theory. It was found that the experimental results were agreed with the theory.
Optimum sample sizes for designing particle count measurements were investigated. NaCl monodisperse aerosols were counted using a condensation nucleus counter (CNC). Statistical analysis of the data from the particle count with CNC agreed with the Poisson distribution. Furthermore, a χ2-test showed that a normal (Gaussian) distribution could be applied to the data when the mean of the particle count (m) is greater than 10. This result indicated that statistical analysis for the data could be simplified by using the normal distribution. In samples with m > 104, the experimental error affected the fluctuation of the data with exceeding the statistical error. Optimum sample size was influenced by m as well as the fluctuation level of the data. These results suggested that the optimum experimental design consisted of 200 data with a mean in the range 10 ≤ m ≤ 103.