| The microscopic and chemical evolution of woody cell wall-derived huminitic macerals from peats and lignites was investigated in order to achieve a better understanding of the: (1) origin of cell wall-derived huminites in low rank coal, and thus, vitrinites in high rank coal, (2) chemical structure of coal itself, and (3) chemical aspects of the gelification process.;Woods of recent origin, peatified woods in various states of decomposition, and lignitic woods were procured from various U.S. swamps and lignitic deposits. During peatification and early coalification the following microscopic trends were recognized: (1) a gradual increase in the degree of natural staining, i.e. cell walls became progressively darker, (2) a rapid increase in the abundance of fungal remains in surface litter followed by a slow decrease, (3) a gradual decrease in the relative intensity of birefringence, and (4) a sharp decrease in primary fluorescence intensity while most other fluorescence parameters (e.g. Q ratio, chromaticity, etc.) increase.;Analyses by chemical fractionation and various Curie-point pyrolysis techniques showed that an array of modified lignin polymers constitute the major components of cell wall-derived huminitic macerals, hence the bulk of coal itself. The molecular structure of the huminitic polymers was dependent on the original lignin structure (i.e. hardwood versus softwood) and the level of coalification. Though some ;Correlations between the observed trends were determined by canonical correlation analyses. These analyses showed that: (1) the birefringence intensity was related to the presence/absence of carbohydrates in huminitic macerals and their precursors, and (2) the degree of natural staining (i.e. intrinsic coloration) and the character of the primary fluorescence of huminites were found to be related to the chemical character of the lignin-derived polymers comprising them.;Gelification is thought to result from the "homogenization" of the cell walls which occurs as the bulk of the carbohydrate skeleton is depolymerized and metabolized while the various modified, remnant lignin-derived polymers form polymers of even greater molecular weight. |
