ATMOSPHERE AND TEMPERATURE CHANGES WITHIN A RECLAIMED COAL STRIP MINE1

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Abstract
We measured oxygen (02) carbon dioxide (CO2), and temperature, over a 2-year period, with depth along a transect of an acid, reclaimed, coal strip mine. Spoil-atmosphere O2 concentrations decreased with depth, but approached zero only in a small portion of the transect. Most of the mine remained well oxygenated (02 > 10 percent by volume) down to the 12-meter depth throughout the year. Carbon dixoide concentrations ranged from near atmospheric levels to greater than 15 percent. Decreases in O2 were strongly correlated with CO2 increases at most locations, although we did not observe a one-for-one replacement, as would be expected if aerobic respiration were the cause of the air-composition changes. Carbonate neutralization of acid produced by pyrite oxidation may also explain the O2–CO2 correlation, but results at some sites are not consistent with that mechanism either. At some locations, especially between 1 and 3 meters from the surface, variations in O2 and CO2 were correlated with changes in the spoil temperature. No such correlation was observed at deeper depths. Spoil temperatures in layers below 3 meters remained in a range conducive to iron-oxidizing bacterial activity year around. Temperature within 60 centimeters of the surface showed greater seasonal extremes than a natural soil and had a mean annual temperature 1.2 to 1.7°C higher. We measured oxygen (02) carbon dioxide (CO2), and temperature, over a 2-year period, with depth along a transect of an acid, reclaimed, coal strip mine. Spoil-atmosphere O2 concentrations decreased with depth, but approached zero only in a small portion of the transect. Most of the mine remained well oxygenated (02 > 10 percent by volume) down to the 12-meter depth throughout the year. Carbon dixoide concentrations ranged from near atmospheric levels to greater than 15 percent. Decreases in O2 were strongly correlated with CO2 increases at most locations, although we did not observe a one-for-one replacement, as would be expected if aerobic respiration were the cause of the air-composition changes. Carbonate neutralization of acid produced by pyrite oxidation may also explain the O2–CO2 correlation, but results at some sites are not consistent with that mechanism either. At some locations, especially between 1 and 3 meters from the surface, variations in O2 and CO2 were correlated with changes in the spoil temperature. No such correlation was observed at deeper depths. Spoil temperatures in layers below 3 meters remained in a range conducive to iron-oxidizing bacterial activity year around. Temperature within 60 centimeters of the surface showed greater seasonal extremes than a natural soil and had a mean annual temperature 1.2 to 1.7°C higher. © Williams & Wilkins 1983. All Rights Reserved.

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