1995 Fisher Scientific Award Lecture Reflections of an atmospheric chemist wondering why he won an analytical chemistry award

Abstract

The author recalls his scientific career starting with electrochemistry and gas phase kinetics and leading, largely by serendipity, to atmospheric chemistry and measurements in the atmosphere using rockets and stratospheric balloons. The scientific problems met along the way required measurements with instruments that were not commercially available and required development of new methods and techniques. These included mass spectrometry, chemiluminescence, and tunable Diode Laser Absorption Spectrometry (TDLAS) to measure trace concentrations of gases in the lower and upper atmosphere. TDLAS is considered to be the method of choice where freedom from interferences, high sensitivity, and fast time response are required. Lead salt laser diodes operate in the near infrared where most molecules of atmospheric interest have strong fundamental absorptions. The research groups at York University and at Unisearch Associates have been pioneers in applying this powerful technique to atmospheric measurements in a variety of environments including the pristine air over the Pacific, at the top of Mauna Loa, at the Grand Canyon, and the polluted air of Los Angeles and other major cities. The results of recent measurements of the emissions of two strong greenhouse gases, CF4 and C2F6, from Quebec aluminium refineries are described. More recently a family of instruments based on near-infrared laser diodes have been developed that can make remote-sensing measurements of a number of pollutants in ambient air and industrial stacks. Examples of passive, on-road, remote-sensing measurements of automobile exhaust emissions of CO and CO2, and of in-stack emissions of HF are presented. Another remote-sensing instrument that has been developed is an improved visible and UV Differential Optical Absorption Spectrometer (DOAS) capable of measuring, remotely and simultaneously, a number of important pollutants. Examples of measurements of NO, NO2, O3, benzene, and toluene are presented. Key words: air measurements, instruments, remote sensing.