Remote detection of gaseous pollutants

The polluting species of Carbon Dioxide and Methane have many sources including leaks from landfill sites and seeps from oil wells. Monitoring of this pollution is necessary to identify their sources, with the eventual aim of reducing their emission. Several techniques have been used to monitor these species in a variety of circumstances. Passive infrared absorption methods are suitable for the monitoring of volcanic plumes (Fourier Transform InfraRed (FTIR), Differential Optical Absorption Spectroscopy (DOAS) and Correlation Spectroscopy (COSPEC)). Vehicle emissions are measured using DOAS, While COSPEC is used to image small gas leaks from short distances. Although these methods can be used to identify the gases of interest, they suffer from resolution and background problems, which would probably render them unsuitable for airborne remote sensing. It is possible to extract images of CO2 and CH4 from hyperspectral imagery. However, due to the sensors design to measure surface reflected radiation, images of gaseous attenuation are relatively poor. Differential Absorption Lidar (DIAL) is a promising system for the remote sensing of gases, overcoming both the resolution and background problems. The ability to locate the gas in range measurements is important, and high-powered pulsed lasers mean airborne remote sensing of gaseous pollutants will soon be a reality.