Detection and mapping of oil-contaminated soils by remote sensing of laser-induced fluorescence

The contamination of soil by aromatic mineral hydrocarbons (MHC) (e.g., gasoline, oil, etc.) has become a severe environmental problem because not only men, animals, and plants are threatened but also the water and air. With the unification of Germany a great number of suspected contaminated sites in the new countries were registered. An estimation of the German Federal Ministry of Environment (BMU) counts 180,000 areas contaminated with different pollutants, 55,000 are situated in the former GDR. On military settlements for example more than fifty percent of the chemicals are MHCs. Hence one can get an idea of the importance of soil pollution by hydrocarbons. Other zones contaminated due to carelessness or accidents are civil petrolstations, airports, refineries, pipelines, and traffic disasters. At the present time for most of these areas the contamination is assumed due to recent use. Due to the large extension of the problem an estimation and evaluation of the potential hazard for the environment is difficult and expensive to perform. In the case of an actual endangering the total area must be mapped in detail resulting in increasing costs for the owner. Nevertheless it is necessary to find reliable timesaving areal mapping and monitoring methods. One opportunity presented in this paper is the application of remote sensing by laser induced fluorescence from an airborne platform. It promises to fulfill these requirements in a sufficiently fast manner with very high spatial resolution. The access to the pollutant detection is the specific laser induced fluorescence emitted by the MHC (finger print). The present work shows the requirements for a helicopterborne lidar system for MHC mapping and how the detected signals are to be evaluated and interpreted.