Dissertations

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Alkaline Pretreatment of Genetically-Engineered Switchgrass for Improved Carbohydrates Conversion Efficiency.
(2012-01-03) Wang, Ziyu; Jay Cheng, Chair; Zhilin Li, Minor; Ratna Sharma, Member; Larry Stikeleather, Member
Alkaline Pretreatment of Switchgrass for Ethanol Production
(2009-10-05) Xu, Jiele; Larry F. Stikeleather, Committee Member; Joseph C. Burns, Committee Member; Ratna R. Sharma-Shivappa, Committee Member; Jay J. Cheng, Committee Chair; Francis L. de los Reyes III, Committee Member
Assessing Eco-geomorphological Condition of Stream Restoration Projects in North Carolina.
(2012-12-14) Doll, Barbara A; Gregory Jennings, Chair; Jean Spooner, Member; William Hunt, Member; William Cope, Minor
Assessment of Ecosystem Service Provision by Stormwater Control Measures.
(2011-09-21) Moore, Trisha; William Hunt, Chair; Michael Burchell, Member; Gregory Jennings, Member; Stephen Broome, Minor
Assessments of Restored, Undisturbed, and Gaged Streams in the Southern Appalachian Mountains.
(2012-03-09) Zink, Jason Michael; Gregory Jennings, Chair; William Hunt, Member; Francois Birgand, Member; Richard McLaughlin, Member
Channel Evolution of a Restored Low Gradient, Sand Bed Stream
(2007-10-30) Lindow, Nicholas L.; Robert O. Evans, Committee Chair; Michael R. Burchell, II, Committee Member; Gregory D. Jennings, Committee Member; Richard A. McLaughlin, Committee Member
Stream restoration design and construction relies on an accurate prediction of stable dimension, pattern, and profile within the bounds of expected dynamic equilibrium. This study charts the morphologic evolution of a small, restored headwater stream in response to hydrologic, hydraulic, and geologic conditions in a low gradient, coastal plain system. The goal of the project was to define an expected dynamic equilibrium for constructed streams in the geomorphic regime and equate changes in stream form to fluvial and geotechnical parameters for predictive analysis. The restored stream reach was a previously straightened stream near Cove City, NC in the Lower Coastal Plain. The channelized stream was degraded due to direct cattle access and lack of features for aquatic habitat. Restoration involved removing the cattle, constructing a new floodplain, and re-meandering the channel. Log sill and rootwad structures were used to protect the stream bed and banks. The floodplain and banks were planted with a mixture of hydrophytic, herbaceous, and woody vegetation. The constructed stream was a low gradient, sand bed channel with an equilibrium bed slope of 0.001 m⁄m, cross sectional area of 1.9 m2, top width of 4.8 m, maximum depth of 0.7 m, and W⁄D of 12. The stream and riparian zone were instrumented for monitoring hydrology and surveying permanent cross sections. Rapid development of channel morphology occurred in the first year of monitoring. No significant changes in channel dimension or profile were recorded after the first year post construction. Significant deviations within the stream features were related to structures. Cross sections with root wads had a 12% steeper median side slope than non-structured stream sections. The channel downstream of log sills was 20% deeper than the median cross sectional depth. The dimensional response to fluvial hydraulics and geotechnical parameters was a complex interaction between stream power, shear stress, inundation, water table gradient, and discharge. The survey information was treated as a longitudinal data set, and multivariate statistical analysis was used to relate changes in stream dimension to stream power, shear stress, inundation, shallow groundwater seepage, and discharge processes. Inundation was directly related to increases in stream bank side slopes. Shallow groundwater gradient measured within the stream banks was a significant explanatory variable of direct changes in channel width, while the hydraulic gradient measured in the floodplain and discharge were inversely proportional. Maximum depth was directly related to discharge, but shear stress and stream power were not significant. In order to study in detail the response in bank side slope to shallow groundwater seepage, a soil lysimeter experiment was conducted using soil from the stream site. Banks were constructed in the lab and a high water table gradient was used to induce seepage at the bank face. Bank side slope was varied between experiments, and each test was run until failure. The observed failure mechanism was due to small, pop-out failures and liquefaction of the underlying sandy soil. Positive pore water pressure in the upper loam horizon reduced apparent cohesion and promoted bank collapse. Bank failures occurred along linear failure planes that were similar to the initial bank slope. An increase in bank slope was observed to increase slope stability. Scour pools that developed downstream of the log sills at the restored stream were modeled using River2D. The survey data and information on roughness and hydrology was used to model the two-dimensional, depth-averaged velocity profile upstream of the logs and within the pools. The maximum depth of scour was modeled using empirical relationships based on the morphologic jump, headloss over the sill, meander radius of curvature, median bed particle size, and flow turbulence. The predicted and measured scour depths were significantly correlated in a mixed linear⁄interactive multivariate model. The model parameters included a morphologic jump term, turbulence, and median bed material size. The scour pool depth was dependent on downstream conditions and tailwater depth. An empirical relationship was derived relating headloss over the weir for prediction of downstream energy condition. Stream restoration design and construction techniques are specific to geomorphologic regime. This study provides scientific knowledge related to stream evolution under fluvial and geotechnical processes in the Lower Coastal Plain of North Carolina. The results can be used to evaluate channel equilibrium conditions, improve construction practices, and predict the implications of designed channel form and structures.
Co-Composting and Characterization of Swine Waste Solids and Its Use as a Soil Amendment in a Field Study: The Effects of Duration of Composting
(2008-02-17) Rivin, Jonathan M; john j. classen, Committee Chair
Composting is a reasonable option for managing swine wastes prior to land application. However, the process is protracted, and the loss of nutrients can be considerable, diminishing the usefulness as a plant nutrient source. For these reasons, reducing composting time has been of interest. The objectives of this research were to compost swine waste feedstocks for various lengths of time, use them as soil amendments in a field study, and subsequently relate the compost characteristics to plant response and changes in soil characteristics. Additionally, a laboratory nitrogen mineralization study was conducted to determine mineralization rates of the amendments. Swine manure solids and Paulownia branches/leaves were co-composted for 0, 3, 6 and 15 weeks. For the field study, the composts and manure were used as soil amendments; fertilized and unfertilized soils were the controls. The uncomposted feedstock-amended soil produced the greatest sorghum stover yield, although grain yields from all treatments were statistically equivalent. With respect to soil physical properties, the effect of treatment on soil bulk density was statistically significant, but for soil impedance and aggregate stability, treatment was not statistically significant. The water holding capacity was not statistically affected by treatment at either field capacity or wilting point. Compared the controls, the reduction in plant available water induced by the manure-amended soil was statistically significant. Due to the minimal effects of soil treatments on soil and plant response, relating amendment characteristics to field response was not feasible The results from a nitrogen mineralization study did not confirm the projected mineralization rates for the amendments, which were hypothesized from the literature. As the amendment application rates were based upon the projected mineralization rates, the field loading rates may have been low. However, the nitrogen mineralization dynamics in the laboratory and in the field may have been dissimilar.
Comparing the performance of naturally ventilated and fan ventilated greenhouses
(2007-08-16) Li, Shuhai; Jack R. Edwards Jr., Committee Member; James H. Young, Committee Member; Mary M. Peet, Committee Member; Daniel H. Willits, Committee Chair
A Comprehensive Analysis of Marine Recirculating Aquaculture Effluent Treatment.
(2012-01-24) Guerdat, Todd; Thomas Losordo, Chair; Francis Lajara De Los Reyes, Minor; Stephen Broome, Member; Michael Burchell, Member
Develop Methods To Evaluate the Performance of Aflatoxin Sampling Plans for Shelled Corn.
(1998-12-29) Johansson, Anders Sture; Thomas B. Whitaker, Chair; Francis G. Giesbrecht, Member; Winston M. Hagler, Jr., Member; James H. Young, Member
Eighteen lots of shelled corn were tested for aflatoxin contamination. The variability and distributional characteristics associated with the aflatoxin testing procedure were investigated. The total variance associated with testing shelled corn was estimated and partitioned into sampling, sample preparation, and analytical variances. All variances were found to increase with an increase in aflatoxin concentration. Using regression analysis, mathematical expressions were developed to model the relationship between aflatoxin concentration and the total, sampling, sample preparation, and analytical variances. The expressions for these relationships were used to estimate the variance for any sample size, subsample size, and number of analyses for a specific aflatoxin concentration. For example, testing a lot with 20 parts per billion (ppb) aflatoxin using a 2.5 lb sample, Romer mill and 50 g subsample, and HPLC analysis, the total, sampling, sample preparation, and analytical variances are 274.9 (CV=82.9%), 214.0 (CV=73.1%), 56.3 (CV=37.5%), and 4.6 (CV=10.7%), respectively. The percentage of the total variance for sampling, sample preparation, and analytical is 77.8, 20.5, and 1.7 %, respectively. Next, fifteen positively skewed distributions were each fitted to 18 empirical distributions of aflatoxin test results for shelled corn. The compound gamma distribution was selected to model the sample aflatoxin test results for shelled corn. The method of moments technique was chosen to estimate the parameters of the compound gamma distribution. Mathematical expressions were developed to calculate the parameters of the compound gamma distribution for any lot aflatoxin concentration and test procedure. Observed acceptance probabilities were compared to operating characteristic curves predicted from the compound gamma distribution and all 18 distributions of sample aflatoxin test results were found to lie within a 95% confidence band. Using the mean and variance relationships to compute the parameters of the compound gamma distribution, 16 sampling plans, based on four sample sizes and four sample acceptance levels were created and analyzed. For a given sample size, decreasing the sample acceptance level, using a sample acceptance level equal to the regulatory guideline: (a) decreases the percentage of lots accepted while increasing the percentage of lots rejected at all aflatoxin concentrations; (b) increases misclassification of lots (both false positives and false negatives) while decreasing the percentage of correct decisions; and (c) decreases the average aflatoxin concentration in the lots accepted and lots rejected. For a given sample size where the sample acceptance level is less than the regulatory guideline, the number of false positives increases and the number of false negatives decreases when compared to the situation where the sample acceptance level equals the regulatory guideline. For a given sample size, where the sample acceptance level is greater than the regulatory guideline, the number of false positives decreases and the number of false negatives increases when compared to the situation where the sample acceptance level equals the regulatory guideline. Increasing the sample size for a given sample acceptance level, where the legal limit equals the sample acceptance level: (a) increases the percentage of lots accepted at lower concentrations while increasing the percentage of lots rejected at higher concentrations; (b) decreases misclassification of lots (both false positives and false negatives) while increasing the percentage of correct decisions; and (c) decreases the average aflatoxin concentration in the lots accepted while increasing the average aflatoxin concentration in the rejected lots.
Development and Field-Testing of the DRAINMOD-FOREST Model for Predicting Water, Soil Carbon and Nitrogen Dynamics and Plant Growth in Drained Forests.
(2010-12-16) Tian, Shiying; Mohamed Youssef, Co-Chair; Richard Skaggs, Chair; John King, Minor; Devendra Amatya, Member; George Chescheir, Member
Development of a Struvite Crystallizer for Reducing Phosphorus in Effluent from Livestock Waste Lagoons
(2003-11-06) Bowers, Keith Edison; Philip W. Westerman, Committee Member
The research successfully met its objectives of designing and characterizing a crystallizer for removing phosphorus from livestock lagoon effluent in North Carolina. A design was created for a struvite crystallizer utilizing a cone-shaped continuous-mode fluidized bed. A laboratory-scale system operating at 49.2 L/h of total liquid flow achieved near-steady state operation at two sets of operating conditions. The first used ammonia addition of 100 ppm and no magnesium (Mg) addition. The second used ammonia addition of 100 ppm and Mg addition of 30 ppm. Estimated reduction in orthophosphate phosphorus (OP) and total phosphorus (TP) was 36 percent and 24 percent, respectively, over the first condition set and 74 percent and 58 percent, respectively, over the second. Three models were developed to describe crystallizer behavior. The MLMB model assumed perfect mixing of both liquid and bed. The PLCB model assumed plug flow of liquid and perfect classification of the bed. The PLMB model, which best predicted behavior, assumed plug flow of liquid and perfect mixing of the bed. Factorial experiments were conducted to test the effects of Mg addition, ammonia addition, and flow rate on phosphorus removal. Increasing Mg addition in the range tested (0 to 60 ppm) and increasing ammonia addition in the range tested (0 to 200 ppm) were significantly associated with increasing phosphorus removal. The effect of flow rate was insignificant between the values tested (41.2 and 56.8 L/h). A field-scale system was assembled at a lagoon and used to conduct factorial experiments testing the same effects as those in the laboratory. Increasing Mg addition in the range tested (0 to 60 ppm), increasing ammonia addition in the range tested (from no pH enhancement to 1 pH point enhancement), and decreasing flow rate between the values tested (341 and 568 L/h) were all significantly associated with increasing phosphorus removal. Reduction in TP and OP averaged 70.2 percent and 77.3 percent, respectively, when ammonia and Mg were being added. Peak reductions in TP and OP were 81.9 percent and 87.1 percent, respectively.
Effect of Riparian Buffers and Controlled Drainageon Shallow Groundwater Quality in the North Carolina Middle Coastal Plain
(2000-11-15) Dukes, Michael Dale; Robert O. Evans, Chair; J. Wendell Gilliam, Member; R. Wayne Skaggs, Member; John E. Parsons, Member
Degradation of water quality in the streams and estuaries of North Carolina in recent years has resulted in regulations to reduce the introduction of numerous types of contaminants to this system. In the Neuse and Tar-Pamlico River Basins, excessive amounts of nitrogen have been identified as causing increased algal growth, low dissolved oxygen concentrations, and have been linked to increased growth of toxic microorganisms such as Pfiesteria piscicida. There are numerous sources of nitrogen to the basins; however, agricultural nonpoint sources have been identified as the largest contributor of nitrogen. Riparian buffers, controlled drainage, and nutrient management have been identified as effective BMPs for reducing nitrogen transport to streams under many landscape conditions. As a result, a combination of nutrient management, controlled drainage, and riparian buffer best management practices have been mandated in the Neuse River Basin to reduce the loss of agricultural nonpoint source pollution. A large portion of the agricultural nonpoint source nitrogen losses to surface waters in the Neuse River Basin originate in the Middle Coastal Plain. These lands are drained by irregularly spaced first and second order streams that have often been channelized (i.e. deepened) to enhance drainage. The riparian vegetation has often been removed from these channelized streams. The effectiveness of riparian buffers and controlled drainage are not well documented under these landscape conditions that are common in the Middle Coastal Plain region. Controlled drainage may not be economical in this region because multiple control structures would be required to maintain a suitable water table elevation in this gently sloping landscape. Implementation of riparian buffers has met strong resistance from the agricultural community due to the potential loss of land. A few studies have also found that nitrogen rich groundwater may enter deeply incised or channelized streams below the active treatment zone of the buffer, rendering the buffer ineffective. A study to evaluate the effect of riparian buffer vegetation type and width on shallow groundwater quality was implemented at the Center for Environmental Farming Systems near Goldsboro, North Carolina. The effect of controlled drainage, riparian buffers, and a combination of both was studied. The hydrologic portion of the riparian ecosystem management model (REMM) was evaluated and tested against field measurements.Five riparian buffer vegetation types were established as follows: cool season grass (fescue), deep-rooted grass (switch grass), forest (pine trees), native vegetation, and no buffer (no-till corn and rye rotation). These vegetation types were established at two buffer widths perpendicular to the channelized streams, 8 m (25 ft) and 15 m (50 ft). In addition, a continuous native vegetation buffer under free drainage and a continuous no buffer treatment under controlled drainage was established. For about 50% of the time monitored, the 15 m riparian buffer plots resulted in a statistically lower NO3-N concentration in the mid depth ditch wells (screen depth 1.5-2.1 m below ground surface) compared to the 8 m plots. Width was not a statistically significant variable at the deep well depth (2.1-3.5 m screen depth). Vegetation type had no statistically significant effect on NO3-N concentration. Nitrate concentration decreased 69 and 28% as groundwater flowed beneath the 8 m wide riparian buffer plots toward the channelized streams and 84 and 43% in the 15 m plots, at the deep and mid depth, respectively. The wider buffers were approximately 15% more effective at removing nitrate, but the improvement was not linearly correlated to the width increase. The primary reason vegetation differences were not observed was likely due to the limited time for vegetation establishment and development during the relatively short 2.5 year study period. Five years or longer may be required for some types of vegetation to mature to the point of impacting the nitrogen in the shallow groundwater. Furthermore, differences in localized groundwater flow paths and soil physical and chemical properties may indefinitely over shadow vegetation effects at this site. Controlled drainage did not raise the water table elevation near the ditch as compared to the free drainage treatment. Over seventeen storm events, the riparian buffer (free drainage) treatment had an average groundwater table depth of 0.92 m, compared to 0.96 and 1.45 m for the combination and controlled drainage treatments, respectively. Again, the lack of hydrologic treatment effect may be due to localized differences in soil properties and groundwater flow paths. Percent NO3-N concentration decrease for those treatments was 22 and 35%, 75 and 51%, and 77 and 69%, for the deep and mid depth wells, for each respective treatment. Although more nitrate was apparently removed from the groundwater on the controlled drainage treatments, this effect could not be correlated to water table depth.Daily predicted water table depth from the riparian ecosystem management model (REMM) was compared to observed depths over a simulation period of two years. The model performed well during some periods but poorly during large storm events. Average absolute errors ranged from 150 to 650 mm. Model instability during large storm events and anomalies in evapotranspiration calculations must be addressed before this model can be a reliable planning tool for regions such as the Middle Coastal Plain of North Carolina.Based on this research, several recommendations for further study are presented. Monitoring of riparian buffer vegetation plots should continue with the expectation that vegetation may have a significant impact over time as the vegetation types become established. Eventually the vegetation in the buffer will reach a steady state with respect to nitrogen in the buffer; however, this may take many years. Quantification of the relative proportion of dilution and denitrification for a given nitrate concentration decrease beneath the buffers should be investigated. One approach would be installation of redox probes at the deep well depth to give an indication if conditions are favorable (i.e. reducing) for denitrification. Also, the deep groundwater (i.e. below the impermeable layer) chemistry should be compared to the shallow groundwater chemistry to determine the relative proportions of constituents such as calcium and magnesium. This analysis would give an indication if dilution of the shallow groundwater were occurring as a result of deep groundwater upwelling. The REMM simulations may be improved by measuring groundwater velocity into the riparian buffer, improving the estimates of surface water runoff into the riparian buffers, and by modifying the model to simulate a single buffer zone rather than three.
Effect of Urban Stormwater BMPs on Runoff Temperature in Trout Sensitive Regions
(2008-11-17) Jones, Matthew Paul; William F. Hunt, Committee Co-Chair; Aziz Amoozegar, Committee Member; Garry L. Grabow, Committee Member; Daniel H. Willits, Committee Co-Chair
While the negative impact of warm urban stormwater runoff on coldwater stream environments has been studied, little is known about the effect of urban stormwater best management practices (BMPs) on runoff temperature. A monitoring study was conducted from May through October of 2005, 2006, and 2007 in western North Carolina, along the southeastern extent of United States trout populations, to examine the effect of urban stormwater BMPs on runoff temperature. The monitoring sites consisted of a stormwater wetland, wet pond, and four bioretention areas. Runoff temperatures at all monitoring locations significantly (p<0.05) exceeded the 21Â°C trout temperature threshold from June through September. Monitored runoff temperatures at a parking lot surrounded by a mature tree canopy and a parking lot covered with a light-colored chip seal were cooler than nearby un-shaded and standard asphalt parking lots. Both the stormwater wetland and wet pond increased water temperatures significantly. Effluent temperatures from the wet pond were significantly warmer than flows from the stormwater wetland from June through September. At both sites, water temperatures were coolest at the bottom depths, and water was cooler than 21Â°C at the bottom of the stormwater wetland during the early summer and early fall, indicating the thermal benefit of an outlet structure that would draw water from these bottom depths. Water was significantly cooler after conveyance in buried pipes when discharged into the stormwater wetland and wet pond. All of the bioretention areas monitored during the course of this study significantly reduced maximum stormwater temperatures; however, only bioretention areas smaller than 10% of their contributing watershed significantly reduced median stormwater temperatures. The larger bioretention areas provided evidence of substantial reductions in runoff volume, which would reduce effluent thermal loads. Despite temperature reductions, all bioretention areas discharged effluent significantly warmer than 21Â°C during the summer months. Evaluation of bioretention temperature profiles showed that the coolest effluent temperatures could be obtained from bioretention areas with a soil depth between 90 and 120 cm. Due to its ability to reduce runoff temperatures and flows, bioretention areas are considered to be an effective treatment option for mitigating thermal pollution from urban stormwater runoff. A computer model was developed to simulate the thermal dynamics of a bioretention area. The model used a Green-Ampt based approach to simulate bioretention hydraulics. Pavement and runoff temperature were calculated using a finite difference solution for thermal conduction within the pavement profile in conjunction with a surface heat balance. A number of analytical and empirical methods were used to estimate weather parameters and the antecedent soil temperature profile. Soil and water temperature profiles during infiltration were simulated using a model for conduction and convection in porous media that utilized separate energy equations for the fluid and solid phases. The bioretention thermal model was validated by comparing simulation results with temperature data collected during the course of the monitoring study. The majority of simulated storm events had a root mean squared error less than 2.0Â°C for bioretention effluent estimates. Predicted effluent temperatures were typically warmer than measured values between 10:00 and 17:00 hours, and cooler for the remainder of the day. A sensitivity analysis showed that effluent temperatures were most affected by input parameters related to the soil and pavement surface heat balances. Simulation results suggested that volume reductions had a larger impact on effluent thermal loads than temperature reductions. Overall, the bioretention thermal model was considered to serve as a valuable tool for predicting bioretention effluent temperatures in trout sensitive regions.
Effects of In-Stream Processes on the Fate of Nitrogen and Phosphorous in Drainage Canals of Forested Watersheds
(2004-05-11) Appelboom, Timothy William; Dr. G.M. Chescheir, Committee Co-Chair; Dr. R.W. Skaggs, Committee Co-Chair; Dr. J.W. Gilliam, Committee Member; Dr. D.M. Amatya, Committee Member; Dr. H.R. Malcom, Committee Member
As time progressed and populations increased, human activities related to the production of resources such as food, timber, clothing, and energy have focused on enhancing biological systems to increase yields. This has resulted in the altering of the natural cycles of nitrogen and phosphorous throughout the world. The objectives of this study were to; 1. conduct a literature review of forest stream hydrologic and nutrient inputs, outputs, and transformations and their associated contributions to the overall budgets, 2. quantify these inputs, outputs, and transformations for a drainage network section in the lower coastal plain of North Carolina, and 3. develop a mathematical relationship to describe nitrate removal from forest drainage systems that can be used in modeling. Upstream inflow, rainfall/throughfall, and subsurface flow along with litterfall and lateral movement were measured as inputs, outflow at the outlet and denitrification were measures as outputs to the drainage section. Denitrification was estimated using seven methods; in stream tanks, undisturbed cores, background N15 and O18 concentrations, N15 enrichment, diffusion calculations, mass balance, and modeling. During this study, 6.7 kg of nitrate was removed through demitrification during the first years flow period (85 days) and 19.8 kg dur4ing the second years flow period (82 days) from the 1900 meter log and 3 meter wide drainage canal section studied. The mathematical relationship to describe the nitrate removal rate is based on a depth and concentration independent term which takes temperature into account. This relationship is based on a term called a mass transfer coefficient (r). This relationship resulted in a mass transfer coefficient (r) of 0.064 m/day at 25oC.
Effects of Subsurface Flows on Wetland Restoration at Juniper Bay and Surrounding Area.
(2006-08-21) Pati, Swamy; Rodney L. Huffman, Committee Chair; R. Wayne Skaggs, Committee Member; Michael J. Vepraskas, Committee Member; Michael R. Burchell II, Committee Member; Gary T. Roberson, Committee Member
The North Carolina Department of Transportation purchased a 270-hectare, roughly elliptical tract of agricultural land, known as Juniper Bay (a Carolina Bay), to convert to wetlands as part of their wetlands mitigation program. Preliminary water balance work suggested that there are significant flows of groundwater entering and leaving the tract. This study was initiated to examine the subsurface potentials and determine the degree to which a ditch around the perimeter of the tract controls the lateral fluxes of groundwater in the surficial aquifer. Five nests of piezometers were installed along each of four 150-m transects crossing the perimeter ditch at approximately the major and minor axes of the tract, which correspond to the suspected maxima of influx and efflux. Deep soil cores (up to 13 m) were collected along each transect to guide placement of piezometers for monitoring hydraulic heads. Piezometer water levels were recorded at 15-minute intervals. Meteorological data were collected with an on-site weather station. Models were developed for the four transects using Visual MODFLOW. Models were calibrated with observed groundwater pressure heads. Maximum absolute error in the calibration process was 0.5 m. The modeling results suggested that the ditch drained water from the surficial system from both sides. In the deeper sand layers, there was an indication of groundwater flowing into the bay at NW and NE transects. Groundwater flows in the SW transect indicated outflows. The SE transects showed water draining into the ditch from both sides. The models were extended to 800-m inside the bay to simulate conditions after the interior ditch system was blocked. Simulation results showed groundwater inflows through the NW, NE, and SE transect, and groundwater outflows through SW transect. The lateral influence of the perimeter ditch had a maximum of approximately of 100 m, observed at the SW transect, and a minimum of 30 m, observed at the SE transect. The extent of influence of the perimeter ditch was also dependent on the weather conditions, showing more influence in summer months compared to winter months. Influence of the perimeter ditch was entirely in the upper sands at the NE and SE transects, but some influence was seen in the middle sand layers at the NW and SW transects. Groundwater flow estimates from the transects were extrapolated over the whole perimeter of Juniper Bay to obtain net groundwater inflow. Net groundwater inflow was approximately 125 mm for the time period of 1 January 2004 to 30 June 2004. To develop recommendations for maintaining the perimeter ditch, the models were run for various scenarios focused on water levels in the perimeter ditch. Control levels were imposed on the ditch and options were investigated. A water level of 35.9 m MSL was identified as a critical point of control of the perimeter ditch. Controlling the water level in the perimeter ditch at 35.9 m will minimize offsite impacts and result in maximum wetland area.
Enzymatic Hydrolysis of Rye Straw and Bermudagrass for Ethanol Production
(2002-11-21) Sun, Ye; John Classen, Committee Member; Jiayang Cheng, Committee Co-Chair; Joel Ducoste, Committee Member; Yuri Yamamoto, Committee Member; Philip Westerman, Committee Chair
Dilute sulfuric acid pretreatment of rye straw and bermudagrass was investigated under acid concentrations of 0.6% to 1.5% (w/w) and residence time 30 min to 90 min. The pretreatment effectively solubilized the hemicellulose components to monomeric sugars such as xylose, arabinose, and galactose. Cellulose in the rye straw was not hydrolyzed into glucose during the acid pretreatment, while part of the cellulose in the bermudagrass was converted into glucose by the acid pretreatment. After enzymatic hydrolysis with excessive cellulases, the glucose yields of 30% to 52% and 46% to 81% of the theoretical potentials were obtained for rye straw and bermudagrass, respectively. The pretreated solid residues were hydrolyzed with cellulases supplemented with β-glucosidase. The addition of β-glucosidase greatly improved the glucose production rate. There was no cellobiose accumulation when the β-glucosidase loading was up to 25 CBU/g (CBU, cellobiase unit, expressed as μmol of cellobiose that is converted into glucose per minute). The conversion rate was 45% for bermudagrass hydrolyzed with cellulases of 10 FPU/g (FPU, filter paper unit, expressed as μmol of glucose produced per min with filter paper as a substrate) and β-glucosidase of 25 CBU/g. The further increase of enzyme loadings did not significantly improve the glucose yield. Rye straw was more resistant to enzymatic hydrolysis than bermudagrass. The conversion rate was 38% with the additions of cellulases at 15 FPU/g and β-glucosidase at 25 CBU/g rye straw. The production of cellulase enzymes in transgenic plants has the potential to significantly reduce enzyme costs. Expression of cellulase enzyme, Acidothermus cellulolyticus E1 endoglucanase, in transgenic duckweed Lemna minor was examined. The recombinant E1 protein was biologically active with the expression level of 0.24% of total soluble protein. HEPES (N-[2-Hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid]) buffer (pH = 8) extracted more proteins including E1 from duckweed fronds than sodium citrate buffer (pH = 4.8) and sodium acetate buffer (pH = 5). The E1 protein was thermotolerant and exhibited the optimal enzyme activity at temperature 80°C and pH 5. The E1 activity remained unchanged after heating at 60°C for 6 h. However, it was inactivated after 15-min heating at 90°C.
Evaluation of Bioretention Hydrology and Pollutant Removal in the Upper Coastal Plain of North Carolina with Development of a Bioretention Modeling Application in DRAINMOD.
(2011-03-25) Brown, Robert; William Hunt, Chair; Gregory Jennings, Member; Richard Skaggs, Member; Aziz Amoozegar, Minor
An Evaluation of Indicator Bacteria Transport in Stormwater Runoff and Removal in Stormwater Control Measures.
(2010-07-07) Hathaway, Jon Michael; William Hunt, Committee Chair; Gregory Jennings, Committee Member; Otto Simmons, Committee Member; Gregory W. Characklis, Committee Member; Alexandria Graves, Committee Member
Forest Operations Impact on Forest Soil and Water on Poorly Drained Organic Soil Watersheds in North Carolina.
(2004-12-09) Grace, Johnny McFero III; Dr. R. Wayne Skaggs, Committee Chair
A 3-year study was conducted to evaluate the effect of thinning a drained loblolly pine (Pinus taeda L.) plantation and harvesting a mature natural (primarily hardwood) watershed on the hydrology and soil hydraulic properties of poorly drained organic soils in the Tidewater region of eastern North Carolina. Harvesting increased bulk density and decreased saturated hydraulic conductivity (ksat), drainable porosity, and saturated water content in the natural watershed. Thinning also decreased ksat and drainable porosity; however, bulk density was not influenced. Mean event outflow increased from 22.0 mm on the control to 47.3 mm on the harvested watershed. Similarly, event peak flow and number of flow days from the harvested watershed were more than 100 percent greater than observed on the control. Mean daily outflow doubled and peak flow rates increased 40 percent on the thinned watershed in relation to the control. These differences in hydrologic behavior are primarily attributed to the harvesting and thinning operation which resulted in reduced ET. Phosphorus increased following harvesting the natural watersheds and thinning the plantation watersheds. Nitrate-nitrogen load increased from 6.35 kg/ha*yr during the calibration period to 36.0 kg/ha*yr during the period following harvesting, an increase four times greater than observed on the control watershed. However, nitrate-nitrogen loads were not significantly impacted by the thinning operation in this study. Sediment load increased following treatment for both the harvesting and thinning treatment. Observed increases in nutrient load occurred following harvesting and thinning; however increased load was primarily associated with increases in outflow rather than elevated nutrient concentrations. The DRAINMOD hydrologic water management model predicted total outflows were within 30 mm and 20 mm of measured flows for the 3-year period (2000-2002) for WS2 (control) and WS5 (thinned), respectively. The difference in daily average outflows over the period was 0.04 mm for WS2 and -0.02 mm for WS5. DRAINMOD accurately predicted daily water table depths over the 3-year period to within 10 cm for WS2 and 5 cm for WS5. Long-term (50 years) average outflow was 21.8 cm for the unthinned condition and 34.7 cm for the thinned condition over the 50-year simulation (1951-2000).

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