Stewart A. Rounds

Applications of Fluorescence Spectroscopy for Predicting Percent Wastewater in an Urban Stream

Dissolved organic carbon (DOC) is a significant organic carbon reservoir in many ecosystems, and its characteristics and sources determine many aspects of ecosystem health and water quality. Fluorescence spectroscopy methods can quantify and characterize the subset of the DOC pool that can absorb and re-emit electromagnetic energy as fluorescence and thus provide a rapid technique for environmental monitoring of DOC in lakes and rivers. Using high resolution fluorescence techniques, we characterized DOC in the Tualatin River watershed near Portland, Oregon, and identified fluorescence parameters associated with effluent from two wastewater treatment plants and samples from sites within and outside the urban region. Using a variety of statistical approaches, we developed and validated a multivariate linear regression model to predict the amount of wastewater in the river as a function of the relative abundance of specific fluorescence excitation/emission pairs. The model was tested with independent data and predicts the percentage of wastewater in a sample within 80% confidence. Model results can be used to develop in situ instrumentation, inform monitoring programs, and develop additional water quality indicators for aquatic systems.

Enantiomer fractions of chlordane components in sediment from U.S. Geological Survey sites in lakes and rivers.

Spatial, temporal, and sediment-type trends in enantiomer signatures were evaluated for cis- and trans-chlordane (CC, TC) in archived core, suspended, and surficial-sediment samples from six lake, reservoir, and river sites across the United States. The enantiomer fractions (EFs) measured in these samples are in good agreement with those reported for sediment, soil, and air samples in previous studies. The chlordane EFs were generally close to the racemic value of 0.5, with CC values ranging from 0.493 to 0.527 (usually >0.5) and TC values from 0.463 to 0.53 (usually <0.5). EF changes with core depth were detected for TC and CC in some cores, with the most non-racemic values near the top of the core. Surficial and suspended sediments generally have EF values similar to the top core layers but are often more non-racemic, indicating that enantioselective degradation is occurring before soils are eroded and deposited into bottom sediments. We hypothesize that rapid losses (desorption or degradation) from suspended sediments of the more bioavailable chlordane fraction during transport and initial deposition could explain the apparent shift to more racemic EF values in surficial and top core sediments. Near racemic CC and TC in the core profiles suggest minimal alteration of chlordane from biotic degradation, unless it is via non-enantioselective processes. EF values for the heptachlor degradate, heptachlor epoxide (HEPX), determined in surficial sediments from one location only were always non-racemic (EF approximately 0.66), were indicative of substantial biotic processing, and followed reported EF trends.

Sources and transport of phosphorus and nitrogen during low-flow conditions in the Tualatin River, Oregon, 1991-93

In the 1980s, significant nutrient-related water-quality problems that impacted beneficial uses were identified in the Tualatin River during the low-flow summer months, defined as May 1 to October 31. Nuisance algal blooms resulted in fluctuations in oxygen concentrations and pH conditions; reduction of phosphorus concentrations was determined to be the most effective control mechanism for these conditions. Elevated ammonia concentrations also contributed to low dissolved oxygen concentrations. Because standards for beneficial uses were not being met, the Oregon Department of Environmental Quality established Total Maximum Daily Loads (TMDLs) for phosphorus and ammonia in the Tualatin Basin, as required by the Clean Water Act. To provide necessary context for the TMDL process, data were collected during the period 1991-93 to characterize the sources and transport of water, phosphorus, and major forms of nitrogen in the main-stem Tualatin River during the summer. A significant source of water to the river was not accounted for by surface-water inputs, and was consistent with direct discharge of ground water to the main-stem river channel. Ground water is also the primary source of water for the tributaries during the summer low-flow season. Because large natural supplies of highly mobile phosphorus exist in the upper 500 feet of valley-fill sediments throughout the Tualatin Basin, ground water in the basin is naturally enriched with phosphorus. While improvement in wastewater treatment efficiencies and land management practices have resulted in significant reductions in nutrient concentrations in the Tualatin River, phosphorus concentrations continue to exceed TMDL criterion concentrations. The presence of significant geologic sources of phosphorus in the basin will confound the achievement of current TMDL criteria for phosphorus in the Tualatin River and its tributaries. In contrast, natural sources of all forms of nitrogen to the Tualatin River are insignificant relative to the effluent from the wastewater treatment plants in the basin. Efficient wastewater treatment is, therefore, an effective means for controlling ammonia concentrations in the main-stem river.

Use of Continuous Monitors and Autosamplers to Predict Unmeasured Water-Quality Constituents in Tributaries of the Tualatin River, Oregon

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Simulating potential structural and operational changes for Detroit Dam on the North Santiam River, Oregon, for downstream temperature management

A hydrodynamic and water temperature model was developed for Big Cliff Reservoir on the North Santiam River in western Oregon for calendar years 2002 and 2003. This model allows the connection of an existing model of Detroit Lake upstream to an existing model of the North Santiam River downstream. The Big Cliff Reservoir model was able to reproduce the daily as well as hourly fluctuations in water surface elevation well. Initial runs showed that the magnitude and seasonal patterns in modeled water temperature released from Big Cliff Dam matched measured temperature just downstream in the North Santiam River generally well; however, model temperatures were 2 to 3°C too warm in late October to early November. Sensitivity testing and other investigations into this issue led to modifications in the setup of the modeled Detroit Lake model releases, which formed the upstream boundary of the Big Cliff Reservoir model. These changes led to somewhat higher water temperature errors within the Detroit Lake model, but improved the measuredto-modeled fit for the Big Cliff release in late October to early November in both 2002 and 2003.

Modeling water quality, temperature, and flow in Link River, south-central Oregon

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Plankton communities and summertime declines in algal abundance associated with low dissolved oxygen in the Tualatin River, Oregon

2. Reduced algal “seed source” to inoculate the river. Small reductions in chlorophyll-a concentrations in the upper river have led to downstream declines (FIG. 2). Although such inoculation is important for maintaining DO, inputs of nuisance algae can be problematic. The inoculation of blue-green algae in June 2008 translated into a large bloom of toxin-producing blue-green algae (Anabaena) in the lower river -the largest in decades (below right).