Abstract

Dissolved oxygen (DO) depletion in a water body is governed by two primary mechanisms: biological oxygen demand (BOD) from the water column, and sediment oxygen demand (SOD) from sediments. SOD is the dominant oxygen sink in many water bodies; measurements show as much as 95% of oxygen consumption as attributable to SOD (Truax, Shindala, & Sartain, 1996). Measuring SOD in surface water impoundments is an essential component in evaluating and an important input for modeling the health of a water body. Traditional SOD measurement methods are difficult in deeper waters, such as in reservoirs or lakes, because traditional SOD measurement chambers require direct placement. The goal of this research was to modify an existing SOD chamber design to support deployment and recovery in depths in excess of 5ft, typically from a boat or other floating platform. The design required accurate DO measurements, taken unattended and recorded for several hours to several days, for SOD calculations and other parameters such as cation releases under anaerobic conditions. Using a previously designed chamber, I developed tools and methods to meet these requirements. DO data logger probes were purchased so that DO calculations could be taken without the need of surface support. To mount the chambers inside the previously designed chambers, a new mounting mechanism was designed and installed onto the chamber lids. Deployment and recovery methods and design were developed to ensure the chambers would be recoverable from a boat in deep waters. Previously, the unmodified chambers could not be deployed unattended because of the required power and data link with the surface. Here I present an easily replicated chamber design that allows for remote chamber placement and measurement of SOD in deep waters without the need of SCUBA or other specialized equipment that is traditionally required. The chamber design allows water to circulate through the chambers until they are placed and closed on the sediment bed, at which time the measurements start, ensuring correct initial conditions. During deployment, the data logger will log DO concentrations at predetermined intervals for several hours or days at a time. To recover the chambers, the researcher must only find the buoy attached to the rope and hoist the units back to the surface. Modifications and methods were tested and revised over the course of several months and dozens of tests. Experiments were conducted at various depths, ranging from 12–50ft, which showed the versatility of the chambers. Using this design, other researchers will be able to generate substantial amounts of SOD data at depths that will allow accurate SOD behavior to be included in models of water impoundments.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering

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