tetralins) as well as decomposition of labile functional groups (e.g., carboxylic moieties) takes place around 300 °C during the early stages of decomposition of the Hiawatha coal. The main degradation step Occurs between 500 and 600 °C when the "bulk" components of the coal start to decompose. A third stage consists of char-forming reactions characterized by the evolution of small, stable molecules and aromatic hydrocarbon moieties.Weathering has an effect on all degradation steps. The alkylnaphthalenés and alkyltetralins are likely to react with the network phase, presumably through "grafting" reactions, thereby becoming unable to evaporate at low temperatures. The increase of oxygen-containing products indicates the formation of various oxygen functional groups (most likely carboxyl, carbonyl, and hydroxyl moieties) during weathering. On the other hand, the intensity of the phenols is decreased in the weathered coal, indicating that the hydroxyl groups react with the network phase by condensation reactions and that the newly formed bonds are not broken at the maximum pyrolysis temperature (610 °C) used in the Py-MS experiments.Acknowledgment. The work reported here was sponsored by U.S. DOE Contract No. DE-FG22-84PC70798 and several research contracts from Utah Power and Light Co. The authors wish to express their appreciation to Mike Brady (Utah Power and Light Co.) for helping to obtain a fresh Hiawatha seam coal sample from the Wilberg mine.

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Solute transport and chemical neutralization (pH 3 to 7) within a shallow heterogeneous aquifer producing acid mine drainage (AMD) are examined at an abandoned surface coal mine in West Virginia. The aquifer is undergoing partial neutralization by mixing with alkalinity from a leaking sludge disposal pond, extending in preferential zones controlled by aquifer heterogeneity. Hydraulic heads interpolated from wells indicate leakage from a central alkaline (pH 7.1, 0.72 meq/L alkalinity) sludge pond is a principal source of recharge. Chemically-conservative sodium, added to AMD during treatment and leaked into the aquifer with the sludge, develops a dispersion plume over a restricted portion of the aquifer that correlates with pH, hydraulic head, and dissolved metals distributions. Concentrations of aluminum, iron, sulfate and acidity display higher concentrations downgradient from the pond as sludge alkalinity is consumed along flow paths. Before reaching springs, most dissolved iron is oxidized and hydrolyzed, likely precipitating in the aquifer as a ferric hydroxide or hydroxysulfate phase. The spatial pattern of iron and aluminum concentrations suggests accelerated oxidation caused by gas transport along the outer slopes of the spoil. Dissolved aluminum concentrations increase with total acidity, suggesting that dissolution of silicate minerals results from acidity released by iron hydrolysis. Neutralization reactions and higher pH are favored in more highly permeable portions of the spoil, where ferrihydrite and aluminum hydroxysulfate minerals (such as basaluminite) are supersaturated, In acid-producing zones at pH < 4.5, jurbanite is near equilibrium and an aluminum-sulfate phase with similar properties may limit aluminum concentrations, but become undersaturated in zones of advancing neutralization. At this particular site, ferrous iron produced by pyrite oxidation is almost completely oxidized over short transport distances, allowing hydrolysis of iron and aluminum should sufficient alkalinity be added to these acid waters.

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