Observations concerning the nature of maceral fluorescence alteration with time

Distinctive features of the alteration of maceral fluorescence intensity with upon blue-light or UV excitation are related to the level of organic maturation. Alteration has been measured in different media; the results demonstrate clearly that the negative component of the alteration phenomenon is due to photochemical oxidation. Highly weathered bituminous coals do not display negative alteration because the potential for oxidation quenching has been reduced. The positive component of alteration is thought to be due to the creation of additional absorption centers and increased molecular rigidity as a result of photochemical oxidation and the enhancement of cross-linking among mobile phase and network molecules.