APPLICATION OF DIGITAL IMAGE-PROCESSING TO A BETA-GAUGE FOR DETERMINING MASS CONCENTRATION OF SUSPENDING PARTICULATE MATTER IN ATMOSPHERE

A two-dimensional image of the mass concentration of suspending particulate matter (SPM) collected on Millipore filter paper was photographed with Ultrofilm-H-3. The printed paper image was transformed into a digital image (256 x 256 pixels) with 256 gray levels. Two results were obtained. The averaged values of gray level over all pixels of the digital image was found to correlate with the mass value measured by a beta-gauge. The characteristical range of the digital image which was transformed to frequency by two-dimensional fast fourier transformation was found in the low frequency. It was presumed to relate to SPM from anthropogenic sources because the SPMs usually show higher density and smaller particle size than SPMs from natural sources.