Seasonal variations in number of acidophilic iron-oxidizing bacteria and iron oxidation in the river contaminated with acid mine water

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Abstract
Number of acidophilic iron-oxidizing bacteria, soluble iron, pH, and water temperature were measured seasonally at five sampling stations in the Akagawa River which is highly polluted by strongly acid mine water discharged from the abandoned Matsuo sulfur and iron-sulfide mine area. Other environmental variables of the river water were also determined (titratable acidity. dissolved oxygen, electrical conductivity, sulfate, aluminum, ammonia and nitrate-nitrogen, and phosphate). Distinct seasonal variations in the number of iron-oxidizing bacteria and ferric iron concentration were observed of the river water during the flow and were correlated with seasonal change in water temperature. Hydrogen ion concentration, dissolved oxygen, nutrients for microorganisms, such as, nitrogen and phosphate in the water of the main stream were judged to be not limited to iron oxidation or bacterial growth. Thus, water temperature was found to be a major environmental factor influencing on the activity of iron oxidation and on the growth of bacteria in the river.