THE ORIGIN AND DISTRIBUTION OF HAPS ELEMENTS IN RELATION TO MACERAL COMPOSITION OF THE A1 LIGNITE BED (PALEOCENE, CALVERT-BLUFF FORMATION, WILCOX GROUP), CALVERT MINE AREA, EAST-CENTRAL TEXAS

The origin and distribution of twelve potentially Hazardous Air Pollut ants (HAPs; As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, and U) identif ied in the 1990 Clean Air Act Amendments were examined in relation to the maceral composition of the Al bed (Paleocene, Calvert Bluff Format ion, Wilcox Group) of the Calvert mine in east-central Texas. The 3.2 m-thick Al bed was divided into nine incremental channel samples (7 li gnite samples and 2 shaley coal samples) on the basis of megascopic ch aracteristics. Results indicate that As, Cd, Cr, Ni, Pb, Sb, and U are strongly correlated with ash yield and are enriched in the shaley coa l samples. We infer that these elements are associated with inorganic constituents in the coal bed and may be derived from a penecontemporan eous stream channel located several kilometers southeast of the mining block. Of the HAPs elements studied, Mn and Hg are the most poorly co rrelated to ash yield. We infer an organic association for Mn; Hg may be associated with pyrite. The rest of the trace elements (Be, Co, and Se) are weakly correlated with ash yield. Further analytical work is necessary to determine the mode of occurrence for these elements. Over all, concentrations of the HAPs elements are generally similar to or l ess than those reported in previous studies of lignites of the Wilcox Group, east-central region, Texas. Petrographic analysis indicates the following ranges in composition for the seven lignite samples: liptin ites (5-8%), huminites (88-95%), and inertinites (trace amounts to 7%) . Samples from the middle portion of the Al bed contain abundant crypt o-eugelinite compared to the rest of the samples; this relationship su ggests that the degradation of plant material was an important process during the development of the peat mire. With the exception of Hg and Mn, relatively low levels of the HAPs elements studied are found in t he samples containing abundant crypto-eugelinite, We infer that the pe at-forming, environment for this portion of the coal bed was very wet with minimal detrital input. Relatively high concentrations of crypto- humotelinite were found in samples from the top and base of the coat b ed. The presence of abundant crypto-humotelinite in this part of the c oal bed suggests the accumulation of wood-rich peat under conditions c onducive to a high degree of tissue preservation in the peat mires. Al though several of the trace elements (Be, Co, Ni, and Sb) exhibit enri chment in these samples, they are not necessarily chemically associate d with humotelinite. We infer that these elements, with the exception of Be, are possibly associated with deposition of the roof and floor r ock of the coal bed; however, further analytical work would be necessa ry to confirm this hypothesis. Beryllium may have an organic origin. ( C) 1997 Elsevier Science B.V.