Spaceborne remote sensing for detection and impact assessment of coal fires in North China

Abstract

China has tremendous coal fields in its Northern regions. Not all of them are accessible for mining yet despite the fact, that China is the world's largest coal producer (about 1 billion tons annually). Many coal seams are reaching the surface and show self-ignited fires of considerable extension. Furthermore, fires occur in mines or in the underground. 56 areas of large fires are known to the Chinese authorities and numerous small ones exist in addition. Due to the vast dimensions of some burning coal fields, extinguishing the fires requires a huge effort. Besides the economic losses caused by burning coal (more than 20 million tons p.a.); 3 to 5 times of this amount is heavily affected by the fire and is therefore of no economic use. The environmental impact regionally and globally must not be neglected. It has been estimated by Chinese scientists that the carbon dioxide produced by these uncontrolled fires contributes with approximately 3 % to the Chinese CO 2 production. Spaceborne remote sensing offers important information such as digital elevation models (DEMs) as basic data for geologic formations and routes for access to burning areas, such as hot spot detection for fire assessment, such as land use classification and deposit estimation, such as estimation of environmentally harmful gases. Multitemporal measurements (e.g. differential SAR interferometry) offer a measure for ground subsidence and estimations of burned coal volumes. Furthermore, it is an efficient means for an early warning system of new fires. In the paper, examples of burning areas will be shown and some relevant computed DEMs. Furthermore, some land use data and some infrared data will be presented. The application of these data for other involved disciplines like modelling of the geologic vicinity surrounding the burning coal seams, analysis and modelling of the fire and its 3-dimensional propagation also based on ground and underground air (oxygen) supply (chimneys) will be mentioned. Based on these models, the best method for extinguishing the fire under observation may be derived as well as methods to prevent new self ignition by oxidation processes. But this will not be covered in the paper.