Relationship of materials in flooded soils and sediments to the water quality of reservoirs—I: Oxygen consumption rates

Abstract

Rates of oxygen consumption were obtained for four soils and six reservoir sediments using sediment-water reaction chambers and a differential respirometer. Determination of microbial activity as measured by [ 14C]glucose metabolism was also performed on these soils and sediments. To study the transformation of newly flooded soils into aquatic sediments, we examined the effects of prolonged submergence and temperature upon oxygen consumption, carbon dioxide formation and methanogenesis. Newly flooded soils initially had high biological oxygen consumption rates, ranging from 67.2 to 76.6% of the total oxygen demand. Established reservoir sediments, in contrast, exhibited extremely high chemical oxygen demands, ranging from 62.7 to 89.9% of the total oxygen demand and had proportionately lower biological oxygen demands. Newly flooded soils had the capacity for high rates of oxygen consumption, carbon dioxide formation, and methanogenesis. However, these rates were extremely temperature-dependent and subject to rapid decline with prolonged submergence due to leaching and degradation of biologically available organic carbon (BAOC). With aging, the amount of BAOC released from the flooded soils decreased, the proportion of reduced inorganic chemical species increased, and a distinct aerobic-anaerobic double layer developed at the soil surface during aerobic conditions in the overlying water column.