Infrared Measurement of Fluorocarbons, Carbon Tetrachloride, Carbonyl Sulfide, And Other Atmospheric Trace Gases

Abstract

A cryogenic procedure for concentrating trace gases in the atmosphere has been developed and applied to the ambient air at Research Triangle Park, NC, Atlantic Beach, NC, and New York City. The concentrated gases have been analyzed by long path infrared absorption spectroscopy, with a detectability down to partial pressures of 10⁻¹¹ atmospheres. Carbonyl sulfide has been detected at partial pressures in the range 1 × 10⁻¹⁰ atm. to 3 × 10⁻¹⁰ atm. Carbon tetrachloride was always detected with a rather narrow partial pressure range of 0.7 × 10⁻¹⁰ atm. to 1.1 × 10⁻¹⁰ atm. Fluorocarbon-11 values ranged from about 1.3 × 10⁻¹⁰ atm. at Research Triangle Park to 8 × 10⁻¹⁰ atm. at New York City. Fluo-rocarbon-12 covered the range 1.8 × 10⁻¹⁰ atm. to 1.0 × 10⁻⁹ atm. Hydrocarbon pollutants varied widely in concentration, but were always detected, even in the clean rural air.