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TRANSIENT BIOGEOCHEMICAL CYCLING AND SEDIMENT OXYGEN DEMAND
Impact/Purpose:
This research focuses on the impact of transient lacustrine processes on biogeochemical sediment-water fluxes and sediment oxygen demand in lakes and reservoirs.
Sediment oxygen demand (SOD), which governs dissolved oxygen (DO) depletion in lakes and reservoirs, is largely controlled by oxygen availability and microbial degradation of organic matter. Organic loading of thermally stratified lakes and reservoirs may lead to significant depletion of DO in the bottom (hypolimnetic) water, resulting in the release of chemical species from sediments, decreased water quality, and increased drinking-water treatment costs. The dynamic nature of lacustrine processes (e.g., sediment-laden hydraulic inflows, differential settling of terrigenous material and organic detritus, and variable near-sediment oxygen concentrations) has been established; however, the degree to which SOD and sediment-water fluxes are specifically impacted by spatial and temporal variations in these processes needs further investigation. Hypolimnetic oxygenation systems (e.g., bubble-plume diffusers), used increasingly by drinking water and hydropower utilities to replenish DO while preserving stratification, can also impact SOD and biogeochemical cycling via diffuser-induced mixing and increased oxygen concentration gradients. Little work has been done to quantify oxygen penetration into sediments, “diffuser-induced” SOD, and soluble chemical fluxes at the sediment-water interface as a result of diffuser use. The objective of this research is to investigate and quantify the effects of variations in sediment loading, mineral and organic matter composition of influent sediments, and oxygen availability on biogeochemical cycling and SOD.
Description:
Through this research, the effects of variable sediment accumulation and oxygen concentration on SOD and soluble chemical fluxes will be quantified. This study will enable correct estimates of “diffuser-induced” SOD to be made that will facilitate appropriate design of hypolimnetic oxygenation systems. Understanding the impacts that transient lacustrine processes have on sediments and the overlying water column is crucial for accurately quantifying SOD, optimizing water quality, and enhancing our ability to manage lakes and reservoirs.