One of the primary concerns of science studies scholars is the translation and utilization of theory in practice. In this thesis, I address this concern as it applies to theories of environmental ethics by analyzing the present use in and the applicability of Green philosophy to a current environmental public policy debate. Namely, through a history and analysis of the debate over the proposed introduction of a foreign species of oyster to the Chesapeake Bay, show that the Green perspective can, if adopted, be a valuable aid to solving current environmental problems. / Master of Science

Although agricultural pesticide use is suspected of being a major contributor to the risk of toxic contamination of the Chesapeake Bay, little information concerning the nature and extent of that risk is available. Such information is essential, however, for setting pesticide risk management priorities and for designing policies to reduce the risk of toxic pollution from agricultural sources. To help meet the information needs of Bay region water quality Management, a model of agricultural pesticide risk is developed and used to assess pesticide risk in Virginia’s Chesapeake Bay Region. The information generated by the model includes: an inventory of which chemicals are used; where they are used; estimates of aggregate chemical use for counties and crops; and an evaluation of the potential adverse environmental effects of that use. This information is provided for both current (1990) and future (2000) pesticide risk. An econometric model of land use in the Bay region is used to predict acreage in various crops to which pesticides will be applied in 1990 and 2000. Next, acreage estimates are combined with pesticide application rates to yield estimates of aggregate use of each pesticide. Finally, environmentally relevant characteristics of the pesticides (toxicity, persistence, mobility, etc.) are used to evaluate the potential environmental risk associated with that use. The policy implications of this modeling are then explored. Particular attention is paid to the potential for targeting of pesticide risk management programs at chemicals, sub-regions, or production systems (i.e. crops) that represent the greatest risk of toxic contamination of the Chesapeake Bay. Results indicate that while urbanization in the Chesapeake Bay region will reduce the amount of land devoted to crop production, the reduction in the acreage to which pesticides may be applied will not greatly reduce pesticide risk in the near future. The risk evaluation effort reveals that pesticide risk is highly concentrated in small subsets of the crops grown in the Bay region, of the pesticides used on those crops, and of the counties located in the region. / Master of Science

Modelling surface runoff can be beneficial to operations within many fields, such as agriculture planning, flood and drought risk assessment, and water resource management. In this study, we built a data-driven model that can reproduce monthly surface runoff at a 4-km grid network covering 13 watersheds in the Chesapeake Bay area. We used a random forest algorithm to build the model, where monthly precipitation, temperature, land cover, and topographic data were used as predictors, and monthly surface runoff generated by the SWAT hydrological model was used as the response. A sub-model was developed for each of 12 monthly surface runoff estimates, independent of one another. Accuracy statistics and variable importance measures from the random forest algorithm reveal that precipitation was the most important variable to the model, but including climatological data from multiple months as predictors significantly improves the model performance. Using 3-month climatological, land cover, and DEM derivatives from 40% of the 4-km grids as the training dataset, our model successfully predicted surface runoff for the remaining 60% of the grids (mean R2 (RMSE) for the 12 monthly models is 0.83 (6.60 mm)). The lowest R2 was associated with the model for August, when the surface runoff values are least in a year. In all studied watersheds, the highest predictive errors were found within the watershed with greatest topographic complexity, for which the model tended to underestimate surface runoff. For the other 12 watersheds studied, the data-driven model produced smaller and more spatially consistent predictive errors. / Master of Science / Surface runoff data can be valuable to many fields, such as agriculture planning, water resource management, and flood and drought risk assessment. The traditional approach to acquire the surface runoff data is by simulating hydrological models. However, running such models always requires advanced knowledge to watersheds and computation technologies. In this study, we build a statistical model that can reproduce monthly surface runoff at 4-km grid covering 13 watersheds in Chesapeake Bay area. This model uses publicly accessible climate, land cover, and topographic datasets as predictors, and monthly surface runoff from the SWAT model as the response. We develop 12 monthly models for each month, independent to each other. To test whether the model can be applied to generalize the surface runoff for the entire study area, we use 40% of grid data as the training sample and the remainder as validation. The accuracy statistics, the annual mean R2 and RMSE are 0.83 and 6.60 mm, show our model is capable to accurately reproduce monthly surface runoff of our study area. The statistics for August model are not as satisfying as other months’ models. The possible reason is the surface runoff in August is the lowest among the year, thus there is no enough variation for the algorithm to distinguish the minor difference of the response in model building process. When applying the model to watersheds in steep terrain conditions, we need to pay attention to the results in which the error may be relatively large.

Excessive sedimentation is a leading cause of aquatic life use impairments in Virginia. As required by the Clean Water Act, a total maximum daily load (TMDL) must be developed for impaired waters. When developing a TMDL for aquatic life use impairment where sediment has been identified as the primary pollutant, the target sediment load is often determined using a non-impaired reference watershed, i.e., the reference watershed approach (RWA). The RWA has historically been used in Virginia to establish TMDL target sediment loads because there is no numeric ambient water quality criterion for sediment. The difference between the sediment load generated by the reference watershed and the load generated by the impaired watershed is used to determine the sediment load reduction required to meet the TMDL target load in the impaired watershed. Recent quantification of the Chesapeake Bay TMDL based on Phase 5.3 of the Chesapeake Bay Watershed Model (CBWM) offers a simpler and potentially more consistent method of calculating target sediment loads for impaired watersheds within the Chesapeake Bay watershed. Researchers in the Biological Systems Engineering department at Virginia Tech have developed the "disaggregate method" (DM) which uses landuse inputs to, and pollutant load outputs from, the CBWM to determine pollutant load reductions needed in watersheds whose areas are smaller than the smallest modeling segments generally used in the CBWM. The DM uses landuse-specific unit area loads from two CBWM model runs (an existing condition run and TMDL target load run) and a finer-scale, locally assessed landuse inventory to determine sediment loads. The DM is simpler and potential more consistent than the reference watershed approach. This study compared the reference watershed approach and the disaggregate method in terms of required sediment load reduction. Three sediment-impaired watersheds (Long Meadow Run, Taylor Creek and Turley Creek) within the Chesapeake Bay watershed were used for the study. Study results showed that the TMDL development method used to determine sediment loads would have noticeable effects on resulting sediment-load reduction requirements. For Taylor Creek, the RWA required 20.4 times greater reductions in sediment load (tons/yr) when compared to the DM. The RWA also required 9.2 and 10.4 times greater reductions for Turley Creek and Long Meadow Run watersheds, respectively. On a percentage basis, the RWA for reduction Taylor Creek was 7.3 times greater than that called for by the DM. The RWA called for 4.4 and 4.6 times greater percent reductions for Turley Creek and Long Meadow Run watersheds, respectively. An ancillary objective of this research was to compare the sediment load reductions required for the impaired and their respective RWA-reference watersheds, using the DM. This comparison revealed that, both Taylor Creek and Turley Creek watersheds required less sediment load reduction than their respective reference watersheds, while the load reductions required for Long Meadow Run were slightly greater than its reference watershed. There are several issues associated with either the RWA or the DM for developing sediment TMDLs. Those issues are discussed in detail. Recommendations the need for further studies, based in questions raised by the research presented here are also discussed. / Master of Science

During the winter 1988-89, diurnal and nocturnal habitat use by juvenile female canvasbacks wintering on the upper Chesapeake Bay was determined. Radio-implanted canvasbacks used shallow water (0-2 m) areas near artificial feeding sites during the day, and deeper water (2-6 m) that had an abundant (> 200/m²) population of small (< 25 mm) Macoma balthica at night. Because of poorer Macoma populations on the east side of the Bay, canvasbacks there may feed more during the day and are in lower Macoma densities at night than west shore canvasbacks. Management of Chesapeake Bay canvasback populations should focus on providing natural foods and rest areas. / Master of Science

Nonpoint source pollution from cropland has been identified as the primary source of nitrogen and sediment, and a significant source of phosphorus in the Chesapeake Bay. These pollutants, whether from point or nonpoint sources, have been found to be the primary cause of declining water quality in the Bay. Numerous studies have indicated that, for many watersheds, a few critical areas are responsible for a disproportionate amount of the nutrient and sediment yield. Consequently, if pollution control activities are concentrated in these critical areas, then a far greater improvement in downstream water quality can be expected with limited funds. In this research a phosphorus transport model is incorporated into ANSWERS, a distributed parameter watershed model. The version of ANSWERS used has an extended sediment transport model which is capable of simulating the transport of individual particle classes in a sediment mixture during the overland flow process. The phosphorus model uses a nonequilibrium desorption equation to account for the desorption of phosphorus from the soil surface into surface runoff. The sediment-bound phosphorus is modeled as a function of the specific surface area of the soil and transported sediment. The equilibrium between the soluble and sediment-bound phosphorus is modeled using a Langmuir isotherm. The extended ANSWERS model was verified using water quality data collected from rainfall simulator plot studies conducted on the Prices Fork Research Farm in Blacksburg, Virginia. The plots consisted of four 5.5 m wide by 18.3 m long strips with average slopes ranging from 6.2 to 11 percent. Two of the plots were tilled conventionally, and the remaining two were no-till. Simulated rainfall at an intensity of 5 cm/h was applied to the plots and runoff samples were analysed for sediment and phosphorus. The model was then verified by comparing the simulated responce with the observed data. The results of the verification runs ranged from satisfactory to excellent. Also developed is a technique for selecting a design storm for ANSWERS. The technique creates an n-year recurrence interval storm with a duration equal to the time of concentration of the watershed. The intensity pattern is simulated on a ten-minute interval using a first-order Markov model with a lognormal distribution. Using a two-year recurrence interval design storm, the use of the model is demonstrated for evaluating the application of conservation practices to critical areas on a Virginia watershed. Application of BMP's to critical areas is shown to be substantially more cost effective in terms of pollutant reduction than nonselective placement of BMP's if cost sharing funds are involved. / M.S.

Availability of dead fish to bald eagles (Haliaeetus leucocephalus), prey preferences of bald eagles, and the effects of food on their distribution and movements on the northern Chesapeake Bay were examined from April 1988-July 1989. Dead fish surveys were conducted, by boat, to monitor dead fish availability in several eagle-use areas of the northern Bay, and 3 methods were used to describe disappearance rates of dead fish: dead fish cages, anchored dead fish and floating dead fish. Live fish availability was monitored using gillnets. Dead fish were most available to eagles from May through September, with a peak in availability in June (0.75 dead fish/km with fish die-offs not included, and 3.5 dead fish/km with fish die-offs included). Channel catfish (Ictalurus punctatus) comprised the largest portion of dead fish in early summer months (30% and 28% of total seen, excluding fish die-offs). In contrast, live catfish comprised only 0.4% and 2.1% of the fish caught near the surface in gillnets during spring and summer indicating that dead catfish may be more available, relative to other species, than live catfish. Atlantic menhaden (Brevoortia tyranus) comprised 83-98% of the fish seen in 2 fish die-offs (175 total fish). Only 2 dead fish were seen along 147.7 km of dead fish surveys in winter (0.014 dead fish/km). Most (95%) dead menhaden that we anchored near the bottom off Aberdeen Proving Ground (APG) in summer were scavenged before becoming rancid (X̅= 0.4 days). In contrast, 70% of dead menhaden that we put out in winter became rancid before being scavenged (X̅= 9 days). Pairs of prey items were offered on shoreline areas to wild bald eagles and on platforms to 2 captive bald eagles. All pair-wise combinations of channel catfish, gizzard shad (Dorosoma cepedianum), menhaden and white perch (Morone americana) were offered. We also paired gizzard shad with mallards (Anas platyrhynchos) and rabbits (eastern cottontails, Sylvilagus floridanus, or domestic rabbits, Oryctolagus cuniculus) in shoreline trials, and gizzard shad with mallards and eastern gray squirrels (Sciurus carolinensis) in captive eagle trials. Wild and captive eagles preferred catfish (P=0.0072 and P<0.0002, respectively), and showed no preference for gizzard shad, menhaden nor white perch. Wild eagles preferred gizzard shad over mallards in summer and in winter (P= 0.062 and P=0.002, respectively), while captive eagles preferred mallards over gizzard shad (P= 0.039). Wild eagles selected gizzard shad 4 of 4 times over rabbits (P= 0.125), while captive eagles selected squirrels 5 of 5 times over gizzard shad (P=0.062, both eagles combined). Handling time and familiarity with prey seem to be major factors influencing prey preference, though prey availability seems to determine the actual diet of eagles on the northern Bay. The prediction that the autumn decline in fish abundance on the northern Chesapeake Bay causes eagle distribution to shift from APG to 2 autumn/early winter concentration areas on the northern Bay (Susquehanna River and the Eastern Shore) and then to Blackwater National Wildlife Refuge (BWNWR) and vicinity (winter concentration area on the lower Bay) was tested. By supplying fish (mostly gizzard shad) ad libidum each morning at 2 sites from 28 September through 11 December 1988 a situation in which fish availability did not decline on APG was simulated. Eagle use of the sites increased from 4 eagles seen on first morning that we supplied fish to a peak of 63 eagles seen on the morning of 8 December. Based on shoreline surveys and relocations of 39 radio-tagged nonbreeding Chesapeake hatched eagles, eagle distribution shifted to the Susquehanna River, where eagles feed on gizzard shad, as in 1986 and 1987. However, they did not shift to the Eastern Shore to feed on waterfowl as they had done in 1986 and 1987. Supplemental feeding on APG failed to keep eagles from moving to the lower Bay. Although local eagle distribution on the northern Bay in autumn seems to be dependent on food availability, the autumn decline in fish abundance may not be the proximate factor causing movement to BWNWR and vicinity. / Master of Science

Research was conducted in soils of the Chesapeake Bay area primarily to determine the combined effects of tillage practice and N fertilizer application rates on N leaching and denitrification losses from corn fields. Three well known models - the NTRM, CERES- Maize, and VT-MAIZE - were also tested to determine their predictive ability of N distribution in soil and crop, the various components of the N cycle, and corn yields. To accomplish the above objectives, two field sites were located (in 1986) for a 3 year study on agronomically important and representative soils that are used for corn production in the Chesapeake Bay drainage basin. The main plot treatment was tillage and consisted of no-till and conventional-till. The subplot treatments were N application rates which consisted of 6 levels with 4 inorganic and 2 organic (sewage sludge) N fertilizers. Denitrification experiments were also conducted on the Groseclose silt loam soil to estimate and compare N loss through denitrification from both till and no-till practices. C₂H₂ was used to inhibit N₂ production and N₂O was collected in closed chambers located on the soil surface. Tensiometers and neutron moisture meter access tubes were also installed to monitor soil moisture and energy levels. Nitrogen leaching losses were determined by applying the principle of N mass balance. Denitrification N loss during the corn growing season was less than 2% of the applied N fertilizer. The N losses from the two tillage systems were not significant at p > 0.10. If Fick’s law is to be applied for predicting N loss from the soil subsequent to C₂H₂ application, sampling must occur after a minimum preset critical time. In the Groseclose soil, there was an increase in both total yield and total N uptake when sewage sludge was applied compared to the split and preplant inorganic fertilizers applied at the same rate. There was no difference in yield or N uptake due to applying N as either preplant or a split application. Where no-till management was used, there was an increase in both yield and N uptake as compared with conventional tillage. In the Suffolk soil, tillage management did not influence yield or N uptake where time and source of N application were studied. The relationship between yield and N application rates for both soil types could be described with quadratic equations. The total N recovery could also be described with quadratic equations. However, these relationships do not hold every year for every season or tillage management practice. The no-till plots retained higher moisture content than conventional tillage plots in the upper 0-100 cm depth. Below 100 cm depth, however, no-till retained less than conventional till. The gain and loss of N in soil was dependent on the tillage type and seasons of the year. During the growing season, generally the conventional tillage gained more N than the no-till. During winter, however, the N losses due to leaching were proportional to the amount of N retained at the end of the growing season. Thus, conventional tillage lost more N by leaching during the winter months. Mineralization of N was higher in conventional till, while denitrification was higher in no-till. Split application has shown less N loss due to leaching than the preplant. Mineralization, denitrification, and leaching took place from both the upper and lower zones of the soil profile. The model performances varied from year to year and from one tillage practice to another. Since they were generally written for average (normal) soil and climatic conditions, they did not make satisfactory predictions under the severe moisture conditions experienced during this study. Thus, they require a great deal of readjustment. Considering all aspects, however, the NTRM is the best model. The unmodified VT-MAIZE is the next best. / Ph. D.

The crab processing industry of the Chesapeake Bay region has, until recently, been able to dispose of their processing wastewaters by discharging them, largely untreated, directly to the receiving waters along which their plants are located. With the upcoming implementation of new NPDES discharge limits, this practice will no longer be possible. This study investigated the potential of two different technologies for treating the processing wastewaters. Bench-scale anaerobic contact type reactors were studied for effectiveness in the removal of organics from the processor’s wastewaters, and a pilot-scale countercurrent air stripping tower was studied for ammonia removal. Two anaerobic reactors which were fed retort process wastewater at F/M ratios of 0.35 and 0.25 lb COD/1b MLVSS/day, were found to achieve organics removals (on a BOD₅ basis) of 88% and 94% respectively. Similarly, a second pair of anaerobic reactors were fed a mixed wastewater, representative of a mechanized processing plant’s total wastewater flow, at F/M ratios of 0.10 and 0.07 lb COD/1b MLVSS/day. These reactors were found to achieve organics removals (on a BOD₅ basis) of 79% and 83% respectively. All four of the reactors were eventually shut down after exhibiting signs of failure. These failures were attributed to possible sodium and ammonia toxicity problems. The effectiveness of the air stripping tower in the removal of ammonia from retort process wastewater was tested in relation to liquid flow rate, influent temperature, and influent pH. A maximum ammonia removal of 71% was observed when treating a waste, with an influent temperature of 580C and pH level of 12.2, at an air-to-water ratio of approximately 825 ft³/gal. Similarly, an ammonia removal rate of 67% was observed while treating a waste, with an influent temperature of 650°C and pH level of 11.0, at an air-to-water ratio of approximately 412 ft³/gal. / Master of Science

Stormwater runoff from urban and urbanizing areas poses a serious threat to water quality, and unless managed properly will impede efforts to restore the Chesapeake Bay.Water quantity, as well as quality, must be considered, and Low Impact Development(LID) is an innovative stormwater management approach that addresses both. LID seeks to mimic a site's predevelopment hydrologic regime by retaining and treating stormwater at the lot level using small, cost-effective landscape features.The purpose for this study was to identify and rank impediments to the implementation of LID in the Virginia portion of the Chesapeake Bay watershed. This was accomplished by going to LID workshops and distributing a survey to stakeholders in attendance. The survey asked respondents to rank the following impediments to the implementation of LID: site-specific & non-structural, property owner acceptance, pollutant removal benefit, development rules, lack of education, maintenance considerations, flooding problems, and cost. Lack of education was ranked as the most important impediment, with development rules following close behind. Pollutant removal benefit was ranked the least important impediment. A second purpose was to assess whether there is a relationship between a county's growth rate and adoption of Better Site Design principles (BSD) and LID. A Code and Ordinance Worksheet was used to evaluate the development rules of 13 counties (6 high growth, 3 medium growth and 4 low growth) within Virginia's portion of the Chesapeake Bay Watershed. The scores from the worksheets were used to determine if the amount of growth pressure experienced by a county influenced the degree to which they incorporated BSD and LID in their local development codes. Statistical testing revealed that the relationship between growth pressure and score on the Code and Ordinance Worksheet was moderate, at best.