Environmental Monitoring by Multi-Spectral Lidar Techniques

Sammanfattning: Multi-spectral lidar (light detection and ranging) techniques have been developed and employed in various environmental studies, ranging from concentration mapping of volcanic emissions to fluorescence imaging of historical monuments. In both absorption measurements of gaseous species and fluorescence imaging of stones, multiple wavelength excitation and multiple wavelength detection have been applied. A mobile frequency agile lidar system, using all-solid-state technology, has been constructed for range resolved atmospheric gas concentration measurements in the ultraviolet, visible and mid-infrared wavelength regions. A measurement method based on multivariate statistical techniques has been developed to analyse the composition of complex gas mixtures from their combined absorption spectrum. Industrial emissions of mercury from chlor-alkali plants and hydrocarbons from a test site, have been studied to explore the capabilities of the new lidar system. Local polynomial regression with local data driven bandwidths has been developed and utilised as a flexible technique for evaluating DIfferential Absorption Lidar (DIAL) data. The method allows an optimally adapted range resolution and control of measurement accuracy. A new method for gas flux measurements using a combination of DIAL and wind videography has been developed. Validation of the method has been performed during measurements of sulphur dioxide at a paper and pulp mill. The emission of sulphur dioxide from the Italian volcanoes Mt Etna, Stromboli and Vulcano has been studied in several ship-borne measurements combining simultaneous passive and active optical spectroscopy techniques. The deviations between the instruments could be explained by modelling the light scattering through the plume, which allowed correction of data for most situations. Fluorescence imaging of the facades of the Lund Cathedral (Sweden) and the Parma Cathedral and Baptistery (Italy), employing a scanning fluorescence lidar system and multivariate analysis techniques, has been performed allowing classification of different stone types and algal colonisation. Range resolved fluorescence measurements of ocean, coastal and harbour water have been performed during a ship-borne cruise in the Mediterranean sea.