The Detection of Zinc Sulfide in Melted Snow Samples

Abstract

A modern Becquerel phosphososcope has been constructed for detecting zinc sulfide tracer in melted snow samples. The device utilizes the components of the real-time sensor described by Nickola et al., adapted to a rotating shutter unit. Commercially available fluidized zinc sulfide powder has been found adequate for storm work when ultraviolet radiation is almost eliminated by cloud cover. The dependence of the light output of the pigment on temperature was found to be negligible at room temperature. An absolute calibration of light output vs. mass concentration of pigment has not been performed; results are expressed as voltage developed by the photomultiplier sensor. Field trials have shown that the instrument is very useful for detecting differences in pigment concentration from time-to-time and place-to-place. The background signal from a test tube of distilled water is 5 mV. Samples of clean snow and stream water produce a signal of 5?8mV. When the tracer is dispersed, the signals found in samples of the snow-pack vary from near background to several hundred millivolts at a distance of 8 mi from the dispersing site, to as high as 70 V in the immediate vicinity of the dispenser.