Development and Use of Optical Remote Sensing Methods for Studies of Megacity Air Pollution and Volcanic Gas Emissions

Licentiate thesis, 2007

Optical Remote Sensing Techniques offers the opportunity to, in real-time, obtain line averaged measurements of gases in the lower and upper atmosphere. These techniques easily offer themselves to automatization, which increases their usability for e.g. risk-assessment of remotely situated volcanoes and routine monitoring of air pollution levels in urban areas. In 2007, a milestone in human history will be passed when half of the world’s population will be living in urban areas. Of these approximately 300 millions will be living in Megacities, defined as urban agglomerations with more than 10 million people. These large urban settlements cause problems with air pollution, problems worsened by the use of low-efficiency combustion techniques. At the same time, approximately 500 million people are living near active volcanoes. People strongly affected by the risk these volcanoes pose on their surroundings and by the emissions of sulphuric and halogenic gases. This thesis deals with the development and use of one Optical Remote Sensing technique, Differential Optical Absorption Spectroscopy (DOAS), for studying air pollution in Megacities, applied to México City and Beijing, and for monitoring of emissions of volcanic gases. A measurement technique for determining the speed and altitude of a gas plume using a DOAS-based instrument has been developed. Also, a method for creating tomographic reconstructions of the gas concentration in a cross section of a gas plume has been developed together with a novel instrument for performing fixed point automatic measurements on gas plumes.