Bog fires are a serious natural phenomena. Major increase in the number of fires has
happened during the last decades due to bog transformation into agricultural lands, accidents and
human activities. During bog fires the peat is exposed to high temperatures due to which chemical
transformation and even mineralisation of peat can occur. The aim of the study was to analyse
the impacts of the bog fires on the bog as an ecosystem, advance the understanding and
knowledge of fire impact on peat and humic matter properties and application possibilities. As
the material for the study peat samples from burnt sites and thermally treated peat were used. To
reveal peat transformation during bog fires, thermogravimetric analysis of peat samples were
done, where amounts of bitumens, humic acids and mineral matter were estimated. During bog
fires thermal modification of peat properties takes place, resulting in full mineralisation of peat
and release of mineral substances. Bog fires lead to development of peat char, bitumens and
significant changes in structure and properties of peat humic acids. However, from perspective
of application of peat as a substrate and from perspective of impacts on the bog ecosystems, the
effects are negligible