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<br /> <br />-2s- <br /> <br />indicative of stage 3 of the acid production process, however, may not have <br />been reached in the 4 weeks allowed in our test. <br />Neither washout nor lag time appears to account for the similar <br />sulfate production rates for innoculated and non-innoculated samples in the <br />experiment results reported here. We conclude the bacteria were riot able <br />to survive in significant numbers on the samples tested. Low bacteria <br />survival may be due to the elevated pH of the samples at the time of <br />innoculation or a difficulty in acclimating to the mineralogy of the <br />samples. <br />3.2.2 Particle Size. In general, the smaller particle sizes <br />exhibited a lower final pH after 10 weeks (Table 5). Sulphate generation, <br />however, showed only a slight tendency to increase with smaller particle <br />sizes. Cumulative acidity was significantly greater for the smaller <br />,particle fraction (Figure 7). The relationship between cumulative acidity <br />and mean particle size was best represented by: Cumulative Acidity (mg as <br />CaCOg) = 43.8 x (mean particle size; mm)-0.24 with a correlation <br />coefficient of 0.99. <br />The total exposed surface area of each sample was calculated <br />assuming the particles were cubes with a specific gravity of 4.5. The <br />surface area for the 81, 62, 83, and B4 samples was found to be 1660, 610, <br />340, and 140 cm2 respectively. The relationship between cumulative acidity <br />and total exposed surface area fit a linear function of: cumulative acid- <br />ity (mg as CaC03) = 0.011 x (surface area; cm2) + 21.6 with a correlation <br />coefficient of 0.91. <br />Hawley and Shikaze (;i2) conclude that the single greatest factor <br />that controls the rate of acid formation is probably available surface <br />area. Kleinmann et. al. (2) in experiments with high sulfur coals from <br />the eastern U.S. found a fairly consistent doubling of acid production and <br />iron concentrations in both sterile and innoculated tests when particle <br />size was reduced by an order of magnitude (0.2-20 cm to 0.02-0.2 cm). <br />However, a study of acid generation rates using a soxhlet reactor found <br /> <br /> <br />