Todd Rasmussen | The University of Georgia (original) (raw)
Papers by Todd Rasmussen
Journal of Environment Quality, 2014
Laboratory incubations of four broiler litter (BL) samples at 30°C were performed to investigate ... more Laboratory incubations of four broiler litter (BL) samples at 30°C were performed to investigate the effect of water content on the decay of uric acid nitrogen (UAN) and xanthine nitrogen (XN). UAN and XN concentrations increased in all samples during a period of 1 to 8 d before declining for the remaining 30 d. The increases may be the result of guanine and adenine catabolism. The slopes of linear equations fit to the natural log of the observations from 16 sampling points over 38 d were compared using the GLM procedure in SAS and results indicate that both UAN and XN decay significantly ( = 0.05) more rapidly with increasing water content (θ). A second study showed significant effects in one of three samples on the decay rate of UAN with additions of flue-gas desulfurization (FGD) gypsum or alum at a water content of 750 g kg BL. The decay rate of XN was not significantly affected. Finally, a simple two-point sampling study on the effect of water potential for the estimation of first order rate equation constants showed a positive relationship between the rate of UAN and XN decay over 28 d as a function of water potential (ψ): UAN = 0.0054 × ψ + 0.1010 ( = 0.9987) and XN = 0.0066 × ψ + 0.1101 ( = 0.9285). This is the first study of UAN and XN decay in BL and the findings add to our understanding of mineralizable N from BL.
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Water Encyclopedia, 2005
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Sssaj, 2009
ABSTRACT Fractured rock media are present at many existing and potential waste disposal sites, ye... more ABSTRACT Fractured rock media are present at many existing and potential waste disposal sites, yet characterization data and physical relationships are not well developed for such media. This study focused on water infiltration characteristics of an exposed fractured rock as an approach for defining the upper boundary condition for unsaturated-zone water percolation and contaminant transport modeling. Two adjacent watersheds of 0.24 and 1.73 ha with slopes up to 45% were instrumented for measuring rainfall and runoff. Fracture density was measured from readily observable fracture traces on the surface. Three methods were employed to evaluate the rainfall-runoff relationship. The first method used the annual totals and indicated that only 22.5% of rainfall occurred as runoff for the 1990-1991 water year, which demonstrates a high water intake rate by the exposed fracture system. The second method employed total rainfall and runoff for individual storms in conjunction with the commonly used USDA Soil Conservation Service curve number method developed for wide ranges of soils and vegetation. Curve numbers between 75 and 85 were observed for summer and winter storms with dry antecedent runoff conditions, while values exceeded 90 for wet conditions. The third method used a mass-balance approach for four major storms, which indicated that water intake rates ranged from 2.0 to 7.3 mm h[sup [minus]1], yielding fracture intake velocities ranging from 122 to 293 m h[sup [minus]1]. The three analyses show the complexity of the infiltration process for fractured rock. However, they contribute to a better understanding of the upper boundary condition for predicting contaminant transport through an unsaturated fractured rock medium. 17 refs., 4 figs., 1 tab.
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Agu Fall Meeting Abstracts, Dec 1, 2010
Precipitation is an essential input into surface hydrologic models. While rain gauges are the mos... more Precipitation is an essential input into surface hydrologic models. While rain gauges are the most common source for precipitation data, many regions suffer from a paucity of precipitation data at appropriate temporal and spatial resolutions. Satellite-based or gridded reanalysis data sources provide alternative rainfall inputs for hydrologic models. The University of Georgia and U.S. Dept. of Energy Savannah River National Laboratory are investigating complex hydrometeorological and source attribution problems using a combination of hydrologic observations and models. The project investigates the use several NASA products including TRMM 3B42, TRMM 3B42RT, and MERRA (Modern Era Retrospective-Analysis for Research and Applications) reanalysis data. These data are used as meteorological inputs for a hydrologic model of the Savannah River watershed, located in Georgia and South Carolina. Hydrologic simulations are performed using the BASINS 4.0 (Better Assessment Science Integrating Point and Non-Point Sources) environmental analysis system and the HSPF hydrologic model. Validation studies of the precipitation datasets along with comparisons of streamflow simulations using the alternative inputs will be presented. The work represents a synergy of scientific analysis and stakeholder applications that the forthcoming GPM era can leverage.
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Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferential flow.... more Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferential flow. Yet this explanation is inconsistent with many field experiments that indicate the presence of ``old'' water in stream inflows, along with matric tensions that are inconsistent with macropore saturation. Alternatively, rapid hydrologic responses can be explained using piston flow - even in unsaturated media. While this displacement effect is attenuated by saturation changes within the unsaturated zone, saturation changes are minimized when the air-soil-water meniscus line is immobile. The meniscus advance may be restricted by soil wettability, as well as by nanoscale surface roughness. Instead of a meniscus advance, the meniscus shape (e.g., the contact angle and capillary radius) may adjust to maintain a constant fluid potential. Dynamic contact angles substantially reduce saturation changes, which is consistent with observed slow tracer and rapid pressure responses in a large, saprolite column experiment.
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Transactions of the ASABE, 2010
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An American Nuclear Society (ANS) working group was recently established to revise ANSI/ANS-2.17,... more An American Nuclear Society (ANS) working group was recently established to revise ANSI/ANS-2.17, a standard for evaluating radionuclide transport in ground water at commercial nuclear power production (NPP) facilities. The working group consists of technical experts from the nuclear industry, Federal and State regulatory agencies, universities, DOE National Laboratories, and hydrogeologic consulting firms. ANS 2.17 was originally adopted in 1980, reaffirmed in 1990, but subsequently withdrawn in 2000 due to a lapse in the decadal concurrence process. The working group charge is to re-visit the lapsed standard, review the state-of-the-science and -practice, and develop a performance-based standard that provides guidelines for demonstrating the ability to detect, characterize, diagnose, quantify, and effectively mitigate accidental and routine subsurface releases of radionuclides from NPP facilities. The resulting consensus standard focuses on subsurface site characterization, monito...
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2007 International Workshop on the Analysis of Multi-temporal Remote Sensing Images, 2007
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Encyclopedia of Earth Sciences Series, 2011
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ABSTRACT While many point sources of pollution have been ameliorated over the last twenty years, ... more ABSTRACT While many point sources of pollution have been ameliorated over the last twenty years, nonpoint sources (NPSs) of pollution remain a serious threat to the nation's water quality (Reilly, 1991). On a national scale, silvi-culture is one of the leading causes of NPS pollution, and has been identified as a localized problem in the Southeast (Myers, et al., 1985). Because forested watersheds often possess the nation's best quality waters, NPS control programs for protecting these waters must be undertaken. In this paper, a conceptual framework is established that shows the complex interrelationships between management mechanisms, investigation methods, and criteria and assessment methodologies for silvicultural NPS pollution control. The role and definition of water quality monitoring for the operation of this management framework is discussed, and the fundamental components related to the design of water quality monitoring programs are discussed. The monitoring programs include monitoring objectives, sampling stations and frequency, and environmental parameters. It should be emphasized that there does not currently exist a technical guide for forest water quality monitoring in the Southeast. It is the intent of this paper, therefore, to draw upon monitoring guidelines developed for other regions, and to clarify the role of water quality monitoring and to propose general design guidelines for implementing forest water quality monitoring programs in the Southeast. This book was published by the Institute of Natural Resources, The University of Georgia, Athens, Georgia 30602 with partial funding provided by the U.S. Department of Interior, Geological Survey, through the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1984 (P.L. 98-242). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors. Proceedings of the 1993 Georgia Water Resources Conference, April 20-21, 1993, Athens, Georgia. Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of Technology
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ABSTRACT We develop the theoretical and applied framework for using sinusoidal pumping tests to e... more ABSTRACT We develop the theoretical and applied framework for using sinusoidal pumping tests to estimate aquifer properties for confined, leaky, and partially penetrating conditions. The framework 1) derives analytical solutions for three boundary conditions suitable for many practical applications, 2) validates the analytical solutions against a finite element model, 3) establishes a protocol for conducting sinusoidal pumping tests, and 4) estimates aquifer hydraulic parameters based on the analytical solutions. The analytical solutions to sinusoidal stimuli in radial coordinates are derived for boundary value problems that are analogous to the Theis (1935) confined aquifer solution, the Hantush and Jacob (1955) leaky aquifer solution, and the Hantush (1964) partially penetrated confined aquifer solution. The analytical solutions compare favorably to a finite-element solution of a simulated flow domain, except in the region immediately adjacent to the pumping well where the implicit assumption of zero borehole radius is violated. The procedure is demonstrated in one unconfined and two confined aquifer units near the General Separations Area at the Savannah River Site, a federal nuclear facility located in South Carolina. Aquifer hydraulic parameters estimated using this framework provide independent confirmation of parameters obtained from conventional aquifer tests. The sinusoidal approach also resulted in the elimination of investigation-derived wastes.
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ABSTRACT Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferent... more ABSTRACT Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferential flow. Yet this explanation is inconsistent with many field experiments that indicate the presence of ``old'' water in stream inflows, along with matric tensions that are inconsistent with macropore saturation. Alternatively, rapid hydrologic responses can be explained using piston flow - even in unsaturated media. While this displacement effect is attenuated by saturation changes within the unsaturated zone, saturation changes are minimized when the air-soil-water meniscus line is immobile. The meniscus advance may be restricted by soil wettability, as well as by nanoscale surface roughness. Instead of a meniscus advance, the meniscus shape (e.g., the contact angle and capillary radius) may adjust to maintain a constant fluid potential. Dynamic contact angles substantially reduce saturation changes, which is consistent with observed slow tracer and rapid pressure responses in a large, saprolite column experiment.
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Journal of Environment Quality, 2014
Laboratory incubations of four broiler litter (BL) samples at 30°C were performed to investigate ... more Laboratory incubations of four broiler litter (BL) samples at 30°C were performed to investigate the effect of water content on the decay of uric acid nitrogen (UAN) and xanthine nitrogen (XN). UAN and XN concentrations increased in all samples during a period of 1 to 8 d before declining for the remaining 30 d. The increases may be the result of guanine and adenine catabolism. The slopes of linear equations fit to the natural log of the observations from 16 sampling points over 38 d were compared using the GLM procedure in SAS and results indicate that both UAN and XN decay significantly ( = 0.05) more rapidly with increasing water content (θ). A second study showed significant effects in one of three samples on the decay rate of UAN with additions of flue-gas desulfurization (FGD) gypsum or alum at a water content of 750 g kg BL. The decay rate of XN was not significantly affected. Finally, a simple two-point sampling study on the effect of water potential for the estimation of first order rate equation constants showed a positive relationship between the rate of UAN and XN decay over 28 d as a function of water potential (ψ): UAN = 0.0054 × ψ + 0.1010 ( = 0.9987) and XN = 0.0066 × ψ + 0.1101 ( = 0.9285). This is the first study of UAN and XN decay in BL and the findings add to our understanding of mineralizable N from BL.
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Water Encyclopedia, 2005
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Water Encyclopedia, 2005
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Water Encyclopedia, 2005
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Water Encyclopedia, 2005
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Sssaj, 2009
ABSTRACT Fractured rock media are present at many existing and potential waste disposal sites, ye... more ABSTRACT Fractured rock media are present at many existing and potential waste disposal sites, yet characterization data and physical relationships are not well developed for such media. This study focused on water infiltration characteristics of an exposed fractured rock as an approach for defining the upper boundary condition for unsaturated-zone water percolation and contaminant transport modeling. Two adjacent watersheds of 0.24 and 1.73 ha with slopes up to 45% were instrumented for measuring rainfall and runoff. Fracture density was measured from readily observable fracture traces on the surface. Three methods were employed to evaluate the rainfall-runoff relationship. The first method used the annual totals and indicated that only 22.5% of rainfall occurred as runoff for the 1990-1991 water year, which demonstrates a high water intake rate by the exposed fracture system. The second method employed total rainfall and runoff for individual storms in conjunction with the commonly used USDA Soil Conservation Service curve number method developed for wide ranges of soils and vegetation. Curve numbers between 75 and 85 were observed for summer and winter storms with dry antecedent runoff conditions, while values exceeded 90 for wet conditions. The third method used a mass-balance approach for four major storms, which indicated that water intake rates ranged from 2.0 to 7.3 mm h[sup [minus]1], yielding fracture intake velocities ranging from 122 to 293 m h[sup [minus]1]. The three analyses show the complexity of the infiltration process for fractured rock. However, they contribute to a better understanding of the upper boundary condition for predicting contaminant transport through an unsaturated fractured rock medium. 17 refs., 4 figs., 1 tab.
Bookmarks Related papers MentionsView impact
Agu Fall Meeting Abstracts, Dec 1, 2010
Precipitation is an essential input into surface hydrologic models. While rain gauges are the mos... more Precipitation is an essential input into surface hydrologic models. While rain gauges are the most common source for precipitation data, many regions suffer from a paucity of precipitation data at appropriate temporal and spatial resolutions. Satellite-based or gridded reanalysis data sources provide alternative rainfall inputs for hydrologic models. The University of Georgia and U.S. Dept. of Energy Savannah River National Laboratory are investigating complex hydrometeorological and source attribution problems using a combination of hydrologic observations and models. The project investigates the use several NASA products including TRMM 3B42, TRMM 3B42RT, and MERRA (Modern Era Retrospective-Analysis for Research and Applications) reanalysis data. These data are used as meteorological inputs for a hydrologic model of the Savannah River watershed, located in Georgia and South Carolina. Hydrologic simulations are performed using the BASINS 4.0 (Better Assessment Science Integrating Point and Non-Point Sources) environmental analysis system and the HSPF hydrologic model. Validation studies of the precipitation datasets along with comparisons of streamflow simulations using the alternative inputs will be presented. The work represents a synergy of scientific analysis and stakeholder applications that the forthcoming GPM era can leverage.
Bookmarks Related papers MentionsView impact
Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferential flow.... more Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferential flow. Yet this explanation is inconsistent with many field experiments that indicate the presence of ``old'' water in stream inflows, along with matric tensions that are inconsistent with macropore saturation. Alternatively, rapid hydrologic responses can be explained using piston flow - even in unsaturated media. While this displacement effect is attenuated by saturation changes within the unsaturated zone, saturation changes are minimized when the air-soil-water meniscus line is immobile. The meniscus advance may be restricted by soil wettability, as well as by nanoscale surface roughness. Instead of a meniscus advance, the meniscus shape (e.g., the contact angle and capillary radius) may adjust to maintain a constant fluid potential. Dynamic contact angles substantially reduce saturation changes, which is consistent with observed slow tracer and rapid pressure responses in a large, saprolite column experiment.
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Transactions of the ASABE, 2010
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An American Nuclear Society (ANS) working group was recently established to revise ANSI/ANS-2.17,... more An American Nuclear Society (ANS) working group was recently established to revise ANSI/ANS-2.17, a standard for evaluating radionuclide transport in ground water at commercial nuclear power production (NPP) facilities. The working group consists of technical experts from the nuclear industry, Federal and State regulatory agencies, universities, DOE National Laboratories, and hydrogeologic consulting firms. ANS 2.17 was originally adopted in 1980, reaffirmed in 1990, but subsequently withdrawn in 2000 due to a lapse in the decadal concurrence process. The working group charge is to re-visit the lapsed standard, review the state-of-the-science and -practice, and develop a performance-based standard that provides guidelines for demonstrating the ability to detect, characterize, diagnose, quantify, and effectively mitigate accidental and routine subsurface releases of radionuclides from NPP facilities. The resulting consensus standard focuses on subsurface site characterization, monito...
Bookmarks Related papers MentionsView impact
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2007 International Workshop on the Analysis of Multi-temporal Remote Sensing Images, 2007
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Developments in Water Science, 2004
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Encyclopedia of Earth Sciences Series, 2011
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ABSTRACT While many point sources of pollution have been ameliorated over the last twenty years, ... more ABSTRACT While many point sources of pollution have been ameliorated over the last twenty years, nonpoint sources (NPSs) of pollution remain a serious threat to the nation's water quality (Reilly, 1991). On a national scale, silvi-culture is one of the leading causes of NPS pollution, and has been identified as a localized problem in the Southeast (Myers, et al., 1985). Because forested watersheds often possess the nation's best quality waters, NPS control programs for protecting these waters must be undertaken. In this paper, a conceptual framework is established that shows the complex interrelationships between management mechanisms, investigation methods, and criteria and assessment methodologies for silvicultural NPS pollution control. The role and definition of water quality monitoring for the operation of this management framework is discussed, and the fundamental components related to the design of water quality monitoring programs are discussed. The monitoring programs include monitoring objectives, sampling stations and frequency, and environmental parameters. It should be emphasized that there does not currently exist a technical guide for forest water quality monitoring in the Southeast. It is the intent of this paper, therefore, to draw upon monitoring guidelines developed for other regions, and to clarify the role of water quality monitoring and to propose general design guidelines for implementing forest water quality monitoring programs in the Southeast. This book was published by the Institute of Natural Resources, The University of Georgia, Athens, Georgia 30602 with partial funding provided by the U.S. Department of Interior, Geological Survey, through the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1984 (P.L. 98-242). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors. Proceedings of the 1993 Georgia Water Resources Conference, April 20-21, 1993, Athens, Georgia. Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of Technology
Bookmarks Related papers MentionsView impact
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ABSTRACT We develop the theoretical and applied framework for using sinusoidal pumping tests to e... more ABSTRACT We develop the theoretical and applied framework for using sinusoidal pumping tests to estimate aquifer properties for confined, leaky, and partially penetrating conditions. The framework 1) derives analytical solutions for three boundary conditions suitable for many practical applications, 2) validates the analytical solutions against a finite element model, 3) establishes a protocol for conducting sinusoidal pumping tests, and 4) estimates aquifer hydraulic parameters based on the analytical solutions. The analytical solutions to sinusoidal stimuli in radial coordinates are derived for boundary value problems that are analogous to the Theis (1935) confined aquifer solution, the Hantush and Jacob (1955) leaky aquifer solution, and the Hantush (1964) partially penetrated confined aquifer solution. The analytical solutions compare favorably to a finite-element solution of a simulated flow domain, except in the region immediately adjacent to the pumping well where the implicit assumption of zero borehole radius is violated. The procedure is demonstrated in one unconfined and two confined aquifer units near the General Separations Area at the Savannah River Site, a federal nuclear facility located in South Carolina. Aquifer hydraulic parameters estimated using this framework provide independent confirmation of parameters obtained from conventional aquifer tests. The sinusoidal approach also resulted in the elimination of investigation-derived wastes.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
ABSTRACT Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferent... more ABSTRACT Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferential flow. Yet this explanation is inconsistent with many field experiments that indicate the presence of ``old'' water in stream inflows, along with matric tensions that are inconsistent with macropore saturation. Alternatively, rapid hydrologic responses can be explained using piston flow - even in unsaturated media. While this displacement effect is attenuated by saturation changes within the unsaturated zone, saturation changes are minimized when the air-soil-water meniscus line is immobile. The meniscus advance may be restricted by soil wettability, as well as by nanoscale surface roughness. Instead of a meniscus advance, the meniscus shape (e.g., the contact angle and capillary radius) may adjust to maintain a constant fluid potential. Dynamic contact angles substantially reduce saturation changes, which is consistent with observed slow tracer and rapid pressure responses in a large, saprolite column experiment.
Bookmarks Related papers MentionsView impact