Noxious gas emissions above former coal and iron mines in Lorraine due to the presence of iron sulphides

摘要

Studies were carried out in the iron and coal basins of Lorraine (North-East of France) which indicated that oxygen-depleted air and carbon dioxide was being emitted into built-up areas related to former mine workings. Investigations were carried out to determine the origin of this gas production indicated that carbon dioxide production could be caused by the oxidation of iron sulphide minerals (pyrite and marcasite) and reaction of sulphuric acid with carbonates minerals to produce carbon dioxide gas. These reactions have produced highly mineralised mine water with circum-neutral pH values and a low content of dissolved metals and metalloids. Through a bibliographic study, similar neutral mine drainage has been observed and assumptions were made on the reactions which could take place. A conceptual model is proposed to explain the gas emissions.