Browsing by Author "Kozarek, Jessica Lindberg"

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    Channel Morphology and Riparian Vegetation Influences on Fluvial Aquatic Habitat
    Kozarek, Jessica Lindberg (Virginia Tech, 2011-01-14)
    As public awareness of river degradation has grown in recent years, the number of stream restoration activities has increased dramatically. Anthropogenic influences at a range of spatial scales from watershed landuse to riparian vegetation management to local channel morphology can have hierarchical relationships to local (meso- and macro-) in-stream habitat characteristics. This research examined these influences first by examining the influence of complex channel morphology on meso-scale brook trout (Salvelinus fontinalis) habitat in Shenandoah National Park, VA, and then by examining the combined influence of watershed urbanization and riparian vegetation (100-200 m reaches) on stream temperature. Moving beyond one-dimensional (1D) averaged representations of fish habitat, this research explored the distribution of two-dimensional (2D) flow complexity metrics at the meso-habitat scale as explanatory variables for brook trout habitat preferences and as potential metrics to evaluate habitat restoration design. Spatial hydraulic complexity metrics, including area-weighted circulation and kinetic energy gradients, were calculated based on 2D depth averaged modeled velocity distributions in two 100-m reaches on the Staunton River. While there were no statistically significant correlations between kinetic energy gradients or area-weighted circulation and fish density, fish density was positively correlated to the percent of the channel dominated by protruding boulders. The structural complexity of areas with protruding boulders create complex flow patterns suggesting that flow complexity plays an important role in available brook trout habitat preferences at the local scale, although the 2D depth averaged model may not have adequately represented this complexity. The 2D distribution of flow characteristics was then investigated further to quantify areas of flow refugia (low velocity shelters) and the relationship between these areas, traditional measures of habitat quality, and fish biomass. Flow complexity in the vicinity of flow obstructions (in this case, boulders) was investigated further using patch classification and landscape ecology metrics. The relative influence of riparian vegetation on stream temperature (another important habitat characteristic) in urban and nonurban watersheds was investigated in 27 paired forested and nonforested reaches in PA, MD, and DE. Riparian vegetation and watershed-scale urbanization both influence stream temperature, which can have profound impacts on in-stream ecosystems. Generally, increased urbanization and removal of riparian forest influenced maximum stream temperatures resulting in higher maximum summer stream temperatures (up to 1.8°C); however, the influence of riparian forests (at at 100-200 m reach scale) decreased with increasing urbanization. Extreme maximum summer temperatures, which are a concern for aquatic biota, increased in both frequency and duration in urban nonforested reaches relative to forested reaches indicating that the addition of a forested 100-200 m long buffer partially mitigated these temperature extremes even in urban watersheds. Overall, changes to channel morphology and riparian vegetation had measurable local effects on stream habitat (temperature and hydraulic complexity) yet the implications of restoration efforts at the local scale on ecosystem services at a larger (km +) scale requires further study.
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    Development and Comparison of 17beta-Estradiol Sorption Isotherms for Three Agriculturally Productive Soils From Different Physiographic Regions in Virginia
    Kozarek, Jessica Lindberg (Virginia Tech, 2005-08-10)
    Natural steroid estrogens such as 17beta-estradiol in low nanogram per liter concentrations can adversely affect the reproductive health of aquatic organisms. The overall goal of this research was to quantify the sorption of 17beta-estradiol to three soils considered to be agriculturally productive from different physiographic regions in Virginia to aid in modeling the concentration of estrogens available for transport in runoff from agricultural fields. Batch equilibrium experiments were conducted with various concentrations of 17beta-estradiol (E2) in a background solution of 5 mM calcium chloride and 100 mg/L sodium azide added to four separate soil samples representative of productive agricultural soils from three different physiographic regions of Virginia. Groseclose loam, Myatt sandy loam and Cecil loam were supplied by the Crop and Soil Environmental Sciences Department at Virginia Tech. All soils were collected from the plow layer (0 to 15 cm) except for an additional Cecil soil sample from the Bt horizon. The concentration of E2 in the liquid phase was measured by gas chromatography/mass spectrometry (GC/MS) and was used to find the time to reach equilibrium and to develop sorption isotherms for each soil. The time required to reach equilibrium for all soils was less than 24 hours. A linear isotherm provided the best fit to model the sorption of E2 to Cecil and Myatt soils (R2 = 0.94 and 0.96, respectively). For Groseclose soil, the general form of the Freundlich isotherm fit best (R2 = 0.98), although the linear isotherm also provided a good fit (R2 = 0.93). The sorption of E2 to agricultural soil appears to be related to the organic carbon content of each soil (Pearson coefficient, 0.82). Attempts to analyze and create isotherms for conjugated E2 by deconjugating with metholysis were unsuccessful.
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    Sorption of estrogen to three agricultural soils from Virginia, USA
    Kozarek, Jessica Lindberg; Wolfe, Mary Leigh; Love, Nancy G.; Knowlton, Katharine F. (American Society of Agricultural and Biological Engineers, 2008)
    Land-applied manures and grazing livestock are sources of estrogens to the environment. Natural steroid estrogens such as 17 beta-estradiol (E2) in low concentrations (ng L(-1)) can adversely affect the reproductive health of aquatic organisms. The goal of this research was to quantify the sorption of E2 to three agricultural soils form different physiographic regions in Virginia, a critical step in predicting transport of estrogens in runoff from agricultural fields. Batch equilibrium experiments were conducted with a range of E2 concentrations (50 to 2000 mu g L(-1)) in a background solution of 5 mM calcium chloride and 100 mg L(-1) sodium azide added to samples of Groseclose loam, Myatt sandy loam, and Cecil loam soils collected from the plow layer (0 to 15 cm) in addition to samples of Groseclose loam, Myatt sandy loam, and Cecil loam soils collected from the plow layer (0 to 15 cm) in addition to a Cecil soil sample from the Bt horizon. The concentration of E2 in the liquid phase was measured by gas chromatography/mass spectrometry (GC-MS) and was used to develop sorption isotherms for each soil. The time required to reach apparent equilibrium for all soils was less than 24 h. In general, the linear isotherm provided a good fit to model the sorption of E2 to agricultural soils from the plow layer (R(2) > 0.9). The sorption of E2 to agricultural soil was correlated to the organic carbon content of each soil (Pearson coefficient, 0.79) with log K(oc) values ranging from 2.90 to 3.99.