無煙炭は自然発火し難いと一般的に言われてきたが，ベトナムの無煙炭炭鉱においては2004 年以降，幾つかの炭鉱において自然発火が多発するようになってきている。筆者等は，これら全ての自然発火事象の調査と対策に関わってきている。また，亜瀝青炭を採掘する一炭鉱における数回の自然発火事象についても調査を行った。本論文では無煙炭の自然発火の特性を中心に検討を行う。この中で，無煙炭の自然発火の指標ガスとして，瀝青炭などに見られる炭化水素系ガスは発生せず，一酸化炭素と水素の二種類のガスに限定されることを明らかにするとともに，自然発火防止の観点から現場の採掘条件の問題点などについても検討する。

In order to prevent the mine pollution caused by the acid mine drainage (AMD) from abandoned metal mines in Japan, the treatment of AMD has been conducted with neutralization using a significant number of reagents. Passive treatment processes are attractive as an alternative because of an energy and cost saving one. Although the passive treatment processes using sulfate-reducing bacteria (SRB) have been investigated widely in the United States and Europe, many of those processes require a huge area that is necessary for a long hydraulic retention time (HRT). So, in this research, the mechanism, influential factors and performance of metal removal using SRB have been investigated in the column test to develop it as a prospective, effective and compact process. The results showed that sulfate reduction by SRB had continued for 140 days under the condition of a 50-hour HRT, and that metals had been removed as sulfides in a column. In addition, it is apparent that the positions where each metal sulfide was precipitated were different. This means that the quality of AMD is an important factor when the treatment facility is designed.