Weathering of organic matter from the Miocene brown shale (Sokolov Basin, Czech Republic): Environmental and remediation aspects

Agrochemical and microbiological properties of the weathering products of Miocene brown shale are influenced by the kerogen type and the amount of pyrite in fresh rocks. Only small amount of humic substances is produced at the weathering of Type I-II kerogen when compared with Type III kerogen. However, large amount of free phenol produced during the weathering of Type III kerogen reduces the bacterial growth. On the contrary, the aliphatic character of Type I-II kerogen allows its rapid bacterial degradation. Regardless the amount of the humic substance produced, the cation-exchange ability of the weathered organic matter is primarily determined by the pH of sediments. In pyrite-rich sediments, the weathered organic matter is saturated with H+ ions and does not participate in cation-exchange reactions. Moreover, low pH reduces the bacterial growth.