Usefulness of sediment oxygen demand as a tool for ompoundment management

Abstract

Sediment erosion and transport have a significant effect on water quality in agricultural watersheds. In the Midwest there are many man-made impoundments which experience severe sediment-related problems. Sediment Oxygen Demand (SOD) measurements have great practical utility for the management of sediment-impacted lakes for which sediment dredging or aeration/destratification schemes represent viable rehabilitation schemes. The report summarizes a fifteen-month study of the phenomenon of SOD in two shallow Illinois impoundments. Both lakes have served as public water supplies and experienced significant water quality problems associated with sediment accumulation or seasonal anoxia. The aims of the investigation were to identify the principal components of the SOD and to develop an optimized SOD procedure. Briefly, batch respirometric measurements of SOD were found to be most diagnostic of oxygen depletion due to sediment resuspension or disturbance. As such, the bulk of the demand could be identified as chemical; and associated with sediment solids rather than due to reduced soluble species in sediment pore waters. Sulfide minerals contributed to the SOD in nearly all cases. An improved method for the determination of acid-soluble sulfide was developed to permit correlation of sulfide levels with sulfidic SOD.