VTechWorks Repository :: Browsing by Author "Eick, Matthew J."

Browsing by Author "Eick, Matthew J."

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Arsenic Adsorption on Iron Oxides in the Presence of Soluble Organic Carbon and the Influence of Arsenic on Radish and Lettuce Development
Grafe, Markus (Virginia Tech, 2000-12-12)
Chapter 2: Germination and Growth of Radish (Raphanus sativus) and Lettuce (Lactuca sativus) Exposed to Arsenite and Arsenate in Hydroponic Growth Solution Little information is available on the survival, uptake, and dry mass production of vegetable seedlings and maturing plants in arsenic enriched environments. Such information is however very important to many vegetable growers in areas of subsistent agricultural like Bangladesh or home-gardeners in closer proximity of As sources such as metal smelters. Accordingly we conducted research investigating (i) the germination and radical formation of radish and lettuce seeds at varying As (V) and As (III) concentrations and (ii) radish and lettuce plants in solution culture. Seed germination studies demonstrated that 0.1mM and 0.025mM are toxic threshold levels of As (III and V) for radishes and lettuce, respectively, while As (V) is more toxic to radish seeds than As (III). Arsenic (III and V) impacted both germination and radical development in radish seeds. For lettuce we observed that As had no impact on germination but reduced radical length significantly (p < 0.01). At most equimolar concentrations, As (III) was more toxic than As (V) in lettuce seeds (0.025 - 0.10mM As), a result contrary to those obtained in radish seeds (0.05 - 0.5mM As). The hydroponic growth studies showed that losses and increases in dry weight are a function of absorbed As and are dependent on the source of As: As (V) or As (III). Moreover, the effect of absorbed As (V) or As (III) on dry weight reductions and increases differed between root and shoot portions of the plants and are crop dependent. Tissue-As (originally solution As (V)) was more toxic at the radish root level and tissue-As (originally solution As (III)) was more toxic at the radish shoot level. Conversely for lettuce, As (III) caused reductions in dry weight, while As (V) had a stimulating effect on biomass production. Lower As (V) concentrations in plant tissue throughout the lettuce study and at low As (V) concentrations (0.02mM) in the radish study may be explained by the molar ratio of P:As of approximately 5. From a food nutrition safety standpoint, studies need to concentrate on sub-lethal levels in order to ensure the proper formation of the harvestable portion of the plant. Chapter 3: Adsorption of Arsenate (V) and Arsenite (III) on Goethite in the Presence and Absence of Soluble Organic Carbon The environmental fate of arsenic is of utmost importance as the U.S. EPA has recently proposed to tighten the arsenic drinking water standard from 50 ppb to 5 ppb. In natural systems the presence of dissolved organic carbon (DOC) may compete with As for adsorption to mineral surfaces, hence increasing its potential bioavailability. Accordingly, the adsorption of arsenate As (V) and As (III) on goethite (α-FeOOH) was investigated in the presence of either a peat humic acid (Hap), a Suwannee River Fulvic Acid (FA) (IHSS) or citric acid (CA). Adsorption edges and kinetic experiments were used to examine the effects of equimolar concentrations of organic adsorbates on arsenic adsorption. Adsorption envelopes were conducted over a pH range of 11 to 3, while the kinetic studies were conducted at pH 6.5 for As (V) and pH 5.0 for As (III). Arsenate adsorption was inhibited in the order of Hap > FA > CA while arsenite adsorption was inhibited in the order of CA > FA > Hap. Humic acid reduces As V adsorption starting at pH 9, with a maximum reduction at pH 6.5. Fulvic acid slightly inhibited As (V) adsorption starting at pH 5, and this inhibition increased with a decrease in pH. No effect was observed in the presence of CA. Arsenite adsorption is inhibited by HA starting a pH 7 and increases with a decrease in pH, while FA and CA reduce As (III) adsorption beginning at pH 8, with a continuous reduction as the pH decreases. The differential extent of As V adsorption in the presence of the organic acids suggests that the distribution and the respective densities of the abundant functional groups (phenol/ catechol OH or COO⁻) are significant in the adsorption of As (V). Furthermore, larger organic acids may hydrophobically partition to surfaces via a more favorable entropy driven reaction mechanism which may influence As (V) diffusion and its subsequent adsorption to surfaces. The decrease in As (III) adsorption is caused by its reduced affinity for the surface at pH values lower than 9, and the simultaneous increase in surface activity by the organic substances' via their COO⁻ functional groups. The results of these experiments suggests that dissolved organic carbon substances are capable of increasing the bioavailability of As in soil and water systems in which the dominant solid phase is a crystalline iron oxide. Chapter 4: Adsorption of Arsenate and Arsenite on Ferrihydrite in the Presence and Absence of Dissolved Organic Carbon (DOC) The adsorption of As (V) and As (III) on synthetic 2-line ferrihydrite in the presence and absence of a peat humic acid (Hap), Suwannee River Fulvic Acid (FA) or citric acid (CA) was investigated. Previous work with goethite has demonstrated the ability of DOC materials to reduce As (V) and As (III) adsorption. In this study, a batch technique was used to examine the adsorption of arsenic (III and V) and DOCs on ferrihydrite in the pH range from 3 to 11. The results obtained demonstrated that As (V) adsorption on ferrihydrite was reduced only in the presence of CA. Arsenate reduced the adsorption of all organic acids except Hap. Both FA and CA reduced As (III) adsorption on ferrihydrite, while Hap had no effect. Fulvic and citric acid adsorption on ferrihydrite was reduced in the presence of As (III), however, adsorption increases of FA and CA were observed at lower pH, which is consistent with a decrease in As(III) adsorption. The peat humic acid had no effect on As (III) adsorption, and we believe that the adsorption process of Hap and As (III and V) on ferrihydrite are independent of each other. The observed differences between this study and the study on goethite are believed to be an intricate function of ferrihydrite's surface characteristics, which affects the mechanisms of surface adsorption and hence the affinity of organic acids such as Hap, FA, and CA for the ferrihydrite surface. As such, the adsorption of DOCs to ferrihydrite are assumed to be energetically less favorable and to occur with a fewer number of ligands, resulting in lower surface coverage of weaker bond strength. Additional factors for the observed differences are discussed. This work demonstrates the importance of the solid phase in adsorption processes and functional group composition, as noticeable differences are observed in comparison to a crystalline Fe-oxide solid phase.
An Assessment of Virginia Cooperative Extension's New Extension Agent Training Program
Brown, Almeshia S. (Virginia Tech, 2003-11-13)
This study is an assessment of the New Extension Agent Training (NEAT) program in Virginia. Although new Extension agents have exceptional subject matter training, they often lack skills needed to be effective Extension professionals (Bennett, 1979). The NEAT program provides a way for new agents to receive hands-on experiences that will facilitate a smooth transition into their respective roles. There is currently no specific data that has the NEAT program. Therefore, an evaluation of the program by its participants to determine its importance and effectiveness may be utilized to enhance the effectiveness of the NEAT program. The survey utilized to collect data in the study was developed by the researcher. The instrument was put on a website where participants could access it during a given time frame. The population consisted of new Extension agents, training agents, and administrators who participated in the NEAT program and are currently employed by Virginia Cooperative Extension (VCE). Participants were asked to rate the importance and effectiveness of the NEAT program in facilitating new Extension agents' growth in a series of goals needed for a new agent to be proficient. These goals were then divided into eight competencies as outlined by National Policy Statement on Staff Training and Development (1968). Participants were asked to provide demographic information and suggestions that would be useful in designing future programs. Data were analyzed using SPSS. The data showed that communication was rated the most important competency while human development was considered the least important. The data related to the ratings of effectiveness of the NEAT program in relation to the eight competencies also demonstrated that respondents rated communication as the most effectively taught competency covered in the NEAT program, and human development as the least effectively taught competency. Significant differences among ratings by position in the NEAT program were measured at the 0.05 alpha level. Significant differences were observed both between new Extension agents and Extension administrators and between Extension training agents and Extension administrators were in the importance of a selected competency and the effectiveness of the NEAT program in teaching the some of the competencies.
Beneficial Reuse of Dredged Materials in Upland Environments
Haus, Nicholas Wes (Virginia Tech, 2011-12-13)
Sediments excavated from dredging operations are known as dredged materials. Beneficial reuse of dredged materials in confined utilization facilities (CUFs) is a new approach that has the potential to productively utilize large quantities of dredged materials. However, several factors can inhibit the use of dredged materials in CUFs. In this study, high levels of salts and polycyclic aromatic hydrocarbons (PAHs) were investigated. In the first part of this study, 176,000 m3 of saline dredged materials was placed into a CUF. In less than 4 years, most of the dredged materials had developed horizonation and converted to Inceptisols. The formation of pedogenic Bg horizons in these soils occurred after a polygonal prism network had developed which partially disintegrated into a blocky structured, oxidized horizon with an abundance of redoximorphic features. During the study period, the soil chemistry of the weathering dredged materials shifted from Na-dominated to Ca and Mg-dominated system, allowing plant invasion. In the second part of the study, a bench-scale greenhouse bioremediation experiment was conducted to test the effectiveness of biosolids, compost, and straw at enhancing PAH degradation. Initial concentrations of PAHs decreased significantly after 150 days using standard methods of extraction. However, at 327 days the concentrations of many PAHs, especially those with higher molecular weights, had rebounded close to initial levels. This indicates that PAH bioremediation studies using organic matter additions and conducted using standard methods of extraction need to be carried out longer periods of time or that extraction methods need to be improved.
Challenges and Opportunities for Denitrifying Bioreactors in the Mid-Atlantic
Bock, Emily (Virginia Tech, 2018-01-18)
Sustaining the global population depends upon modern agricultural practices reliant on large inputs of nitrogen (N) fertilizer, but export of excess N from agroecosystems has negative environmental consequences, such as accelerated eutrophication and associated water quality degradation. The challenges posed by diffuse and widespread nutrient pollution in agricultural drainage waters necessitate cost-effective, adaptable, and reliable solutions. In this context, enhanced denitrification approaches developed over the last several decades have produced denitrifying bioreactors that harness the ability of ubiquitous soil microorganisms to convert bioavailable N into inert N gas, thereby removing bioavailable N from an ecosystem. Denitrifying bioreactors are edge-of-field structures that consist of organic carbon substrate and support the activity of denitrifying soil bacteria that remove N from intercepted nutrient-enriched drainage waters. The potential to improve bioreactor performance and expand their application beyond the Midwest to the agriculturally significant Mid-Atlantic region was investigated with a three-pronged approach: 1) a pilot study investigating controls on N removal, 2) a laboratory study investigating controls on emission of greenhouse gases nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), and 3) a field study of one of the first denitrifying bioreactors implemented in the Atlantic Coastal Plain. The pilot and laboratory studies tested the effect of amending woodchip bioreactors with biochar, an organic carbon pyrolysis product demonstrated to enhance microbial activity. The pilot-scale study provides evidence that either hardwood- of softwood-feedstock biochar may increase N removal in woodchip bioreactors, particularly under higher N loading. The results from the laboratory experiment suggest the particular pine-feedstock biochar tested may induce greater greenhouse gas emissions, particularly of the intermediate product of denitrification and potent GHG nitrous oxide. The field study evaluated performance of a biochar-amended woodchip bioreactor installed on a working farm. Two years of monitoring data demonstrated that the bioreactor successfully removed N from drainage waters, but at relatively low rates constrained by low N loading that occurred in the absence of fertilizer application during continuous soy cropping at the site (10.0 kg NO3--N ha-1 yr-1 or 4.86 g NO3- -N m-3 d-1 on the basis of bed volume reached the bioreactor.) Removal rates averaged 0.41 g m-3 d-1 (8.6% removal efficiency), significantly lower than average rates in systems receiving greater N loading in the Midwest, and more similar to installations in the Maryland Coastal Plain. Greenhouse gas fluxes were within the range reported for other bioreactors, and of the N removed an average of only 0.16% was emitted from the bed surface as N2O. This case study provides useful measurements of bioreactor operation under low N loading that informs the boundaries of bioreactor utility, and may have particular regional relevance. The pilot and field studies suggest that wood-based biochars may enhance N removal and may not produce problematic quantities of greenhouse gases, respectively. However, the laboratory study raises the need for caution when considering the costs and benefits amending woodchip bioreactors with biochar and accounting for the effect on greenhouse gas emissions in this calculation, because the tested pine biochar significantly increased these emissions.
Changes in Fluvial Erosion of Cohesive Streambank Soils with Stream Chemistry
Thompson, Theresa M.; Akinola, Akinrotimi I.; Hoomehr, Siavash; Eick, Matthew J. (2018-06-01)
The goal of this study was to quantify changes in fluvial erosion rates with changes in stream chemistry.
Chemical Monitoring of a Primary Water Supply: Lake Pelham in Culpeper, Virginia
Morgan, John (Virginia Tech, 2011-12)
Over the last decade there has been an increase in public and government concern over water quality in the United States, especially water bodies that are sources of drinking water. A study conducted by the United States Geologic Survey (USGS) and the National Water-Quality Assessment (NAQWA), has indicated that nutrient concentrations in streams and groundwater in basins with significant agricultural or urban development are substantially greater than naturally occurring or “background” levels (Dubrovsky, 2010). Various academic studies throughout the United States have demonstrated that many water sources are in danger of being severely polluted, with accelerated eutrophication occurring in many lakes. Specifically, the EPA, who has the task of monitoring these water bodies along with the USGS, has tightened the regulations about point and non-point sources of pollution, in an attempt to reduce the amount of eutrophication in sensitive water bodies. Lake Pelham, located in Culpeper, Virginia has experienced an increase in water quality problems; specifically an increase in nutrients in the lake, causing significant algae blooms. Increasing concern over the amount of nutrients found in lakes, rivers, streams and other water ways (i.e. the Chesapeake Bay) have yielded an increase in the amount of money spent on studies, both at the Federal (EPA) and state level (DEQ). Furthermore, several counties and towns have taken it upon themselves to conduct monitoring programs on their local water sources, to ensure the health of potable water as well as the health of their constituents. The objectives of this research program for Lake Pelham were to: 1.) conduct a literature review of similar surface water systems to highlight current trends in nutrient concentrations 2.) measure and monitor the total phosphorus and nitrogen levels in the lake and examine relationships between nutrient concentrations, water temperature, dissolved oxygen content, and pH and 3.) outline future actions for monitoring Lake Pelham and possible preventive actions for nutrient control. In 2010, the interaction between pH, temperature, nitrogen and phosphorous was investigated. The total nitrogen concentration of Lake Pelham is highly dependent on the leachate entering the lake. Large increases in nitrogen occur during even the smallest rainfall events, suggesting nitrogen is entering the lake from the surrounding environment. The current study indicates that the mean annual average total nitrogen concentration of the lake is approximately 10 mg/l. This value provides a baseline which can be used while the total nitrogen is being monitored over the next several years. In previous years, an increase in pH values (< 1.0 between test dates) was associated with algal blooms in the lake and necessitated the treatment with copper sulfate. Between 1992 and 2010, the nitrogen concentration doubled and the phosphorus concentration increased 7 fold. Algae concentrations and pH fluctuation decrease as the water temperature decreases. Similar to nitrogen, phosphorus concentrations in the lake increase with rainfall events suggesting a relationship to runoff and/or leeching entering from the surrounding watershed. Even during lower water levels, similar to what occurred in August of 2010, when the lake was 15 inches below peak level, a small rainstorm had a large impact on the amount of phosphorus entering the lake requiring the addition of copper sulfate. The trophic state for Lake Pelham was calculated from the average values of the total phosphorus measured in the lake over 2010 and the Secchi disk readings from the same time period. The Tropic State Index (TSI) was calculated to be 59.75 when using the total concentration of phosphorus in Lake Pelham. The TSI calculated from the Sechhi Disk values was 54.5. This gives a average TSI value of 57.1, which indicates that the lake is in a eutrophic state. This was the first attempt at determining the trophic state of Lake Pelham. The study is an important first step for understanding nutrient loading in Lake Pelham and applying protective measures to preserve water quality. Similar to a study conducted in King County, Washington, long term data (decade or more) and in depth statistical analysis will be needed to explain the seasonal variability of Lake Pelham.
Chemistry and Transport of Metals from Entrenched Biosolids at a Reclaimed Mineral Sands Mining Site in Dinwiddie County, Virginia
Lasley, Katrina (Virginia Tech, 2008-06-30)
Deep row incorporation of biosolids is an alternative land application method that may allow higher than currently permitted mine land reclamation application rates. Biosolids treated by various processes possess characteristics that uniquely affect metal solubility and mobility due to their influence on metal speciation. The objectives of this research were to compare the effects of biosolids stabilization type and rate on heavy metal solubility, mobility, and speciation. Two rates each of Alexandria, (Virginia) anaerobically digested (213 and 426 dry Mg ha-1) and Blue Plains (Washington, DC) lime-stabilized (329 and 657 dry Mg ha-1) biosolids were placed in trenches at a mineral sands mine reclamation site in Dinwiddie County, Virginia in June and July 2006. Vertical and lateral transport of heavy metals from the biosolids seams were determined by analyzing leachate collected in zero tension lysimeters below the trenches and suction lysimeters adjacent to the trenches. Chloride (Cl-), sulfate (SO42-), nitrate (NO3-), phosphate (PO43-), dissolved organic carbon (DOC), and pH were also determined within the dissolved fractions (< 0.45 Âµm) collected on September 8, 2006, November 3, 2006, January 5, 2007, June 8, 2007, and September 7, 2007 as input for the speciation program MINTEQA2. Silver, Cd, Pb, and Sn did not move vertically or laterally to any significant extent. Lime-stabilized biosolids produced higher cumulative metal mass transport per sampling period for Cu (967 g ha-1), Ni (171 g ha-1), and Zn (1027 g ha-1) than the anaerobically digested biosolids and control during the 15-month period following entrenching. Barium mass loss was similar for both biosolids. All metals moved primarily with particulates. MINTEQA2 predicted the majority of the metals within the dissolved fraction were present as free ions. As pH decreased and time increased, the amount of association with fulvic acids decreased allowing more free ions and binding with inorganic ligands. Little movement into groundwater demonstrates that anaerobically digested and lime-stabilized biosolids can be land-applied at high rates with little concern of heavy metal contamination of groundwater under these conditions.
Competitive Adsorption of Arsenite and Silicic Acid on Goethite
Luxton, Todd Peter (Virginia Tech, 2002-12-12)
The adsorption behavior of silicic acid and arsenite alone and competitively on goethite over a broad pH range (3-11) at environmentally relevant concentrations was investigated utilizing pH adsorption data and zeta potential measurements. Both addition scenarios (Si before As(III) and As(III) before Si) were examined. The results of the adsorption experiments and zeta potential measurements were then used to model the single ion and competitive ion adsorption on goethite with the CD-MUSIC model implemented in the FITEQL 4.0 computer program. Silicic acid adsorption was reduced by the presence of arsenite for all but one of the adsorption scenarios examined, while in contrast silicic acid had little effect upon arsenite adsorption. However, the presence of silicic acid, regardless of the addition scenario, dramatically increased the arsenite equilibrium solution concentration over the entire pH range investigated. The CD-MUSIC model was able to predict the single ion adsorption behavior of silicic acid and arsenite on goethite. The modeled zeta potential data provided further evidence of the CD-MUSIC model's ability to describe the single anion adsorption on goethite. Our model was also able to collectively describe adsorption and zeta potential data for the low Si-arsenite adsorption scenario quite well however, our model under-predicted silicic acid adsorption for the high Si-arsenite competitive scenario.
Complicated Composting: Persistent Pyridine Carboxylic Acid Herbicides
Reimer, Julie (Virginia Tech, 2013-05)
This paper reviews pyridine carboxylic acid herbicide impacts on compost. Pyridine carboxylic acid herbicides are not completely broken down during grass growth, harvest and drying of hay, in the digestive tract of livestock, or during composting. These herbicides are a popular choice for broadleaf weed control because of this persistence: they remain effective for months or years. Pyridine carboxylic acids are also more effective than the common herbicide 2, 4-dichlorophenoxyacetic acid and can be applied to pastures with grazing livestock because they have low mammalian toxicity. The growth-inhibitory action of naturally occurring pyridine compounds has been researched since the discovery of α-picoline-γ-carboxylic acid in the early 1900’s. These pyridine carboxylic acid compounds mimic plant growth hormones called auxins, causing plants to grow abnormally and then die. Plants injured by auxinic herbicides have poor seed germination, twisted growth, cupped or enlongated leaves, misshapen fruit, reduced yields, and ultimately die. Picloram (4-amino-3,5,6-trichloropyridine-2-carboxylic acid) was developed by Dow Chemical Company as a systemic herbicide for herbaceous weeds and woody plants in rights-of-way, forestry, rangelands, pastures, and small grain crops. Clopyralid (3,6-dichloropicolinic acid) was also developed by Dow Chemical Company to control annual and perennial broadleaf weeds in crops and turf. Another Dow herbicide, aminopyralid (4-amino-3,6-dichloro-2-pyridine carboxylic acid), is used for broad leaf weed control in pastures. Aminocyclopyrachlor (6-amino-5-chloro-2-cyclopropylpyrimidine-4-carboxylic acid) is the first pyrimidine carboxylic acid herbicide and was developed by DuPont for weed and brush control on uncultivated non-agricultural areas, uncultivated agricultural areas, industrial sites, and natural areas. Clopyralid compost contamination was reported in 2000 at four different facilities including Washington State University. In Vermont, compost samples were tested and found to contain aminopyralid, clopyralid, and picloram in 2012. Across the U.S. since 2000, there have been many reports of apparent plant injury from compost contaminated with auxinic herbicides. Because of the limited testing facilities and expense of chemical testing, the majority of these reports remain anecdotal. If the history of a compost feedstock is unknown, bioassays are recommended to test compost for the presence of auxinic herbicides. Even though pyridine carboxylic acid herbicides are sold with proper labeling and restrictions, compost contamination is continuing. Adjustments should be made for the registered uses of these herbicides, and herbicide applicators need improved education about the implications of contaminating compost feedstock.
Conservation Programs and White-tailed Deer Ecology
Royeen, David D. (Virginia Tech, 2019-05-07)
White-tailed deer have reached historical numbers since nearly being wiped out due to overhunting and habitat loss. This paper seeks to review the rebound of white-tailed deer populations, specifically analyzing the role conservation practice and habitat management have played. A brief history of private land contracts in the United States is established before relating deer ecology to habitat availability. The importance of deer from the perspective of humans as well as the ecosystem is highlighted in an effort to encourage and promote conservation and habitat preservation efforts. This work seeks to answer the question “How do conservation programs influence white-tailed deer behavior and what steps can land managers take to protect wildlife on their property?”. A list of recommendations for land owners is given to share best-practice policies for governing a healthy population of white-tailed deer. Lastly, study limitations and constraints of this paper are analyzed to promote transparency and identify areas of concern with data collection.
Creating learning opportunities for students with Science on a Sphere
Bates, Kara (Virginia Tech, 2014-07)
In many classrooms, teachers are looking for ways to increase student engagement. Disengaged students are not reaching their full potential and experience relatively high levels of anxiety and frustration, which negatively impacts learning. Providing multiple hands-on and problem-solving learning opportunities can increase student engagement. The new curriculum developed for use on the Science on a Sphere provides educators with a resource to create problem-solving learning opportunities in their classrooms by using cooperative learning. These opportunities will help students understand how to work in collaborative groups while learning about and solving science-related problems. The curriculum consists of activities themed around climate change and human health. Additionally, the curriculum has been aligned to the Virginia Standards of Learning. To assess the curriculum, teachers and administrators reviewed, assessed, and provided feedback on the lesson plans and handouts. Overwhelmingly, most respondents stated that while the activities were well thought-out, would be beneficial for increasing students’ learning, and provided problem-solving learning opportunities for students, they would not feel comfortable using and interacting with the Science on a Sphere without first participating in some form of training. Therefore, prior to making this curriculum available to other teachers, professional development opportunities should be provided to teach educators how to use and interact with the Sphere.
Desorption Kinetics of Lead from Goethite: Effect of Mixing and Sorption Period
Garman, Stephanie Michelle (Virginia Tech, 2006-02-10)
In natural systems, the solution concentration and hence, potential bioavailability of trace metals is primarily controlled by adsorption-desorption reactions at the mineral-water interface. While many studies have been conducted to understand the adsorption of trace metals to soil minerals, less is known about long-term adsorption/desorption processes. In this study, we examined the influence of mixing and sorption period on the desorption of lead from goethite. Lead sorption was rapid and essentially complete in 1 h, with no change in the quantity of lead adsorbed over the 6 month sorption period. Desorption of lead was slower than the adsorption reaction and was best modeled by two first order equations. At all sorption densities, the desorption of lead followed the order Short-term (24 h) > Long-term non-stirred (6 months) > Long-term stirred (6 months). However, statistical analysis indicated that these differences were not statistically significant. Furthermore, the desorption rate coefficients were very similar for all the experiments indicating that there was no significant residence time effect in this study. However, a sample from a previous study that was allowed to age 5 years and then analyzed by the desorption procedure did have statistically significant differences between the long-term (5 years) and the short-term (5 months). These results suggest that longer adsorption periods, perhaps a number of years, may be necessary to determine if residence time effects are an artifact of the experimental conditions or truly the length of the adsorption period.
Determining Sources of Fecal Contamination in Two Rivers of Northumberland County, Virginia
Szeles, Cheryl Lynne (Virginia Tech, 2003-04-09)
The goal of monitoring the water quality of shellfish beds is to provide protection against transmission of water-borne infectious diseases. The Coan River and the Little Wicomico River contain shellfish beds that are closed to harvest due to contamination with fecal bacteria. These two rivers are located in Northumberland County, Virginia, and empty into the lower Potomac River and the Chesapeake Bay. Bacterial source tracking (antibiotic resistance analysis of Eschericia coli) was used to determine the sources of fecal contamination that have caused shellfish harvest closures in these two rivers. A total of 1,248 Eschericia coli isolates were collected from known sources to build a regional library for the rivers. The Virginia Department of Shellfish Sanitation (DSS) and project cooperators collected known source samples from August 2001 to September 2002. The Average Rate of Correct Classification for the known source library was 71.9%, with a total of 930 isolates correctly classified. The categories (and rates of correct classification) were Birds (84.7%), Humans (74.8%), Livestock (72.4%), Pets (62.0%), and Wildlife (65.7%). The library was used to identify the sources of Eschericia coli isolated from DSS sampling stations along the Coan and Little Wicomico Rivers from August 2001 to September 2002. Some stations contained a substantial human signature, while wildlife and birds are also major contributors. The results will be used to decide the necessary changes that need to be addressed if the shellfish harvesting beds are to be reopened.
Determining Sources of Fecal Pollution in Water for a Rural Virginia Community
Graves, Alexandria Kristen (Virginia Tech, 2000-08-01)
This project involves developing and applying bacterial source tracking (BST) methodology to determine sources of fecal pollution in water for a rural community (Millwood, VA). Antibiotic resistance analysis (ARA) is the primary BST method for fecal source identification, followed by randomly amplified polymorphic DNA (RAPD) analysis for confirmation. Millwood consists of 66 homes, all served by individual septic systems, and a stream (Spout Run) passes through the center of the community. Spout Run drains a 5,800 ha karst topography watershed that includes large populations of livestock and wildlife. Stream and well samples were collected monthly and analyzed for fecal coliforms and fecal streptococci, starting in 5/99 and ending in 5/00. Twelve percent of the well samples and 92% of the stream samples were positive for fecal coliforms, and 26% of the stream samples exceeded the recreational water standard (1,000 fecal coliforms/100 ml). ARA of fecal streptococci recovered from the stream samples indicated that isolates of human origin appeared throughout the stream as the stream passed through Millwood with a yearly average of (approx. 10% human, 30% wildlife, and 63% livestock), and the percent human origin isolates declined downstream from Millwood. These results were obtained by comparing the antibiotic resistance profiles of stream isolates against a library of 1,174 known source isolates with correct classification rates of 94.6% for human isolates, 93.7% for livestock isolates, and 87.8% for wildlife isolates. There is a human signature in Spout Run, but it is small compared to the proportion of isolates from livestock and wildlife. The sporadic instances where well water samples were positive appeared primarily during very dry periods. Restricting livestock access to streams can dramatically lower fecal coliform counts during the unusually hot and dry periods. Reducing FC counts to below recreational water standards for Virginia (1000 per 100ml for any one sample) may be achievable, however to maintain streams below standards may prove to be difficult, as Spout Run is in an area where there are large populations of Canada geese, deer, and other wildlife, and will be hard to restrict these animals.
Developing a Stormwater Pond Filter to Capture Phosphorus and Other Pollutants
Houston, Stephanie Chung-Pei-Hua (Virginia Tech, 2018-06-11)
Excess nutrients, particularly phosphorus (P), significantly contribute to anthropogenic eutrophication, which negatively impacts ecosystems, human health, and the economy. Traditional Best Management Practices (BMPs) such as wet retention ponds prevent eutrophication by acting as a sink for nutrients, but can become a source of pollutants if not properly monitored and maintained. A proposed solution is a standalone, multi-stage filter system that can attach to BMPs with standing water for targeted removal of excess nutrients and with the potential to recycle the filter media. The studies in this dissertation seek to address the feasibility of this solution through the following tasks: 1.) develop a tool that can identify ponds and locations within ponds with high total phosphorus (TP) concentrations, 2.) evaluate filter media that can remove P and can be recycled along with captured P, and 3.) develop a filter system that can remove pollutants in separate stages for the option to recycle certain pollutants. The studies focused primarily on P because the nutrient has the potential to be recycled if captured within the filter. Models developed in the first task showed that TP concentrations in the water were correlated with the pond outlet, pH of the water, and iron concentrations. TP concentrations in the sediment were correlated with the pond's length-to-width ratio and the concentration of aluminum and copper. For the second task, a batch experiment and measurements of physicochemical properties were conducted on four biochars (corn stover pyrolized at 400°C , corn stover pyrolized at 600°C, mixed hardwood, and rice husk). Results indicated that mixed hardwood biochar could sorb dissolved phosphorus (DP) above a solution concentration of 2.9 mg P/L. The properties that could allow this biochar to sorb DP were a smaller negative surface charge, high surface area, smaller concentration of elemental P, and more water-extractable cations. A laboratory-scale test of a three-stage filter system was performed as part of the third task. The filter effectively separated nitrogen and P in different stages, but did not separate lead from P. Median water quality parameters (pH, conductivity, temperature, turbidity, dissolved oxygen, carbon, iron) met U.S. EPA recommended limits, but some parameters violated the recommended limits at a few time points. These studies demonstrate that excessive pollutant concentrations exist in current BMPs, which can benefit from a filter system. The filter system has the potential to collect pollutants separately provided that the correct media mix and configuration is identified such that P can be more completely isolated and water quality parameters are met.
Development of the Urban Wetland Filter for Managing Phosphorus in Stormwater
Rosenquist, Shawn E. (Virginia Tech, 2010-03-19)
Degradation of surface water quality by excess nutrients in stormwater is a substantial environmental and economic problem in the U.S. Phosphorus (P) is often the limiting nutrient for harmful algal blooms and the best target to prevent degradation. Natural treatment strategies such as constructed wetlands (CW) demonstrate effective and economical P management but obstacles exist to implementation. Biological P removal has large land requirements that limit the use of best management practices (BMP) in high land-value areas. Various BMP also utilize sorption processes (SP) for P removal but variations in performance and finite sorption capacity limit SP as a viable long-term removal strategy. However, by understanding variability and making sorption capacity renewable, SP could provide, with shorter retention times, a space-efficient, long-term removal strategy. This multi-study research program developed the urban wetland filter (UWF), a concept intended to overcome the unique limitations of high land-value areas to natural treatment strategies and provide a low-cost, easily implemented BMP to meet P management goals while harvesting sequestered P for use as a fertilizer. Experimental factors included substrate and influent properties pertinent to understanding performance variation and optimizing microbial iron (Fe) reduction for rejuvenation of sorption capacity. Regarding performance, modeling identified major sources of variability including, by order of importance, magnitude of a solution/substrate concentration gradient, length of the "antecedent dry period" between loadings, and pH. Field-scale results confirmed this multifactor dependence of P-removal while also supporting the inclusion of cast-iron filings in substrate to improve P removal. Regarding rejuvenation, results indicated that microbial Fe reduction is capable of releasing previously sequestered P from substrates. A sufficient carbon source was necessary, but microbial inoculation was not necessary to facilitate Fe reduction, which released most of the previously sequestered P, albeit more slowly than P sequestration. Field-scale results indicated that Fe reduction might occur faster under field conditions, possibly due to humic acids, and that inclusion of cast-iron filings enabled additional P removal after rejuvenation by providing a conservative source of Fe for the creation of new sorption sites; however, cast-iron filings may also limit the release of P during rejuvenation.
Dolomite and Micronutrient Fertilizer Affect Phosphorus Fate in Pine Bark Substrate used for Containerized Nursery Crop Production
Shreckhise, Jacob H.; Owen, James S. Jr.; Eick, Matthew J.; Niemiera, Alexander X.; Altland, James E.; White, Sarah A. (2019-09)
Dolomite and a micronutrient fertilizer are routinely incorporated into a pine bark-based soilless substrate when producing containerized nursery crops, yet the effect of these amendments on phosphorus (P) is not well understood. The objective of this research was to determine the effect of dolomite and micronutrient fertilizer amendments on P partitioning among four P fractions (i.e., orthophosphate-P EOM non-orthophosphate dissolved P [NODP], total dissolved P [TDP], and particulate P (PPJ) and to model potential P species in leachate of pine bark substrate. Amendment treatments incorporated into bark at experiment initiation included (1) a control (no fertilizer, dolomite, or micronutrient fertilizer), (2) controlled-release fertilizer (CRF), (3) CRF and dolomite, (4) CRF and micronutrient fertilizer, or (5) CRF, dolomite, and micronutrient fertilizer. Phosphorus fractions in leachate of irrigated pine bark columns were determined at eight sampling times over 48 days. Amending pine bark with dolomite and micronutrient fertilizer reduced leachate OP concentrations by 70% when averaged across sampling dates primarily due to retention of OP in the substrate by dolomite. The NODP fraction was unaffected by amendments, and the response of TDP was similar to that of OP. Particulate P was present throughout the study and was strongly correlated particulate Fe and DOC concentrations. Visual MINTEQ indicated MnHPO4 and Ca-5(PO4)(3)(OH) were consistently saturated with respect to their solid phase in treatments containing CRF. Results of this study suggest amending pine bark with dolomite and micronutrients is a best management practice for reducing P leaching from containerized nurseries.
Dolomite and Micronutrient Fertilizer Affect Phosphorus Fate When Growing Crape Myrtle in Pine Bark
Shreckhise, Jacob H.; Owen, James S. Jr.; Eick, Matthew J.; Niemiera, Alexander X.; Altland, James E.; Jackson, Brian E. (American Society for Horticultural Science, 2020-05-07)
Soilless substrates are routinely amended with dolomite and sulfate-based micronutrients to improve fertility, but the effect of these amendments on phosphorous (P) in substrate pore-water during containerized crop production is poorly understood. The objectives of this research were as follows: compare the effects of dolomite and sulfate-based micronutrient amendments on total P (TP), total dissolved P (TDP), orthophosphate P (OP), and particulate P (PP; TP − TDP) concentrations in pour-through extracts; to model saturated solid phases in substrate pore-water using Visual MINTEQ; and to assess the effects of dolomite and micronutrient amendments on growth and subsequent P uptake efficiency (PUE) of Lagerstroemia L. ‘Natchez’ (crape myrtle) potted in pine bark. Containerized crape myrtle were grown in a greenhouse for 93 days in a 100% pine bark substrate containing a polymer-coated 19N–2.6P–10.8K controlled-release fertilizer (CRF) and one of four substrate amendment treatments: no dolomite or micronutrients (control), 2.97 kg·m−3 dolomite (FL); 0.89 kg·m−3 micronutrients (FM); or both dolomite and micronutrients (FLM). Pour-through extracts were collected approximately weekly and fractioned to measure pore-water TP, TDP, and OP and to calculate PP. Particulate P concentrations in pour-through extracts were generally unaffected by amendments. Relative to the control, amending pine bark with FLM reduced water-extractable OP, TDP, and TP concentrations by ≈56%, had no effect on P uptake efficiency, and resulted in 34% higher total dry weight (TDW) of crape myrtle. The FM substrate had effects similar to those of FLM on plant TDW and PUE, and FM reduced pore-water OP, TDP, and TP concentrations by 32% to 36% compared with the control. Crape myrtle grown in FL had 28% lower TDW but pour-through OP, TDP, and TP concentrations were similar to those of the control. Chemical conditions in FLM were favorable for precipitation of manganese hydrogen phosphate (MnHPO4), which may have contributed to lower water-extractable P concentrations in this treatment. This research suggests that amending pine bark substrate with dolomite and a sulfate-based micronutrient fertilizer should be considered a best management practice for nursery crop production.
Dynamic forcing of oxygen, iron, and manganese fluxes at the sediment-water interface in lakes and reservoirs
Bryant, Lee Davis (Virginia Tech, 2010-03-23)
The National Research Council recently called for a more interdisciplinary approach to drinking water research to address the critical issue of global drinking water supplies. Hypolimnetic oxygenation systems (HOₓ) are being increasingly used to improve water quality in stratified reservoirs by increasing dissolved oxygen (O₂) concentrations and subsequently suppressing the release of soluble species such as iron (Fe) and manganese (Mn) from the sediment into the water. However, while the influence of HOx on the water column has been established, little work has been done on how oxygenation affects sediment O₂ uptake (i.e., sediment oxygen demand) and other sediment-water fluxes. In response to the growing need for alternative approaches for improving water quality, we conducted highly interdisciplinary research to evaluate how O₂, Fe, and Mn cycling at the sediment-water interface is influenced by both natural and HOx-induced variations in water column dynamics, chemical redox processes, and microbial activity within the sediment, all of which may govern sediment-water fluxes. Studies were performed in an alpine lake in Switzerland and in an HOₓ-equipped drinking-water-supply reservoir in Virginia. This research was based on in situ field campaigns paired with laboratory experiments, microbial analyses, and computer simulation to elucidate variable sediment O₂ uptake and corresponding Fe and Mn cycling. This work is unique in that sediment-water fluxes were assessed using in situ data from both sides of the sediment-water interface. Results show that sediment O₂ uptake flux is strongly controlled by both wind- and HOₓ-induced dynamic forcing. Our findings reveal that Fe and Mn fluxes were suppressed from the bulk hypolimnion via biogeochemical cycling in the oxic benthic region. Results also indicate that the sediment microbial community structure may directly respond to HOₓ-induced variation in sediment O₂ availability. Additionally, based on an analysis of the robustness of several commonly used methods for flux calculations, we show that flux estimates are not strongly dependent on the method chosen for analysis. Ultimately, by emphasizing the highly transient nature of sediment O₂ uptake, this research will aid in accurate characterization of various sediment-water fluxes and corresponding water quality. Our results will also directly contribute to the optimization of HOₓ operations and lake and reservoir management.
Effect of Leaching Scale on Prediction of Total Dissolved Solids Release from Coal Mine Spoils and Refuse
Ross, Lucas Clay (Virginia Tech, 2015-08-24)
Coal surface mining in the Appalachian USA coalfields can lead to significant environmental impacts including elevated total dissolved solids (TDS) levels in receiving streams. Column leaching procedures are recommended by many studies for TDS prediction, but many question their applicability to field conditions. The objective of this study was to assess results from a simple column leaching method relative to larger scale leaching vessels (scales) using one coal mine spoil and two coarse coal refuse materials. A non-acidic mine spoil sample from SW Virginia (crushed to ≤ 1.25 cm) was placed into PVC columns (~10 cm x 40 cm) in the laboratory and leached unsaturated with simulated acidic rainfall. The same spoil was also placed into larger 'mesocosms' (~1.5 m³) with run-of-mine material and into barrels (~0.1 m³; screened to ≤ 15 cm) under natural field environmental and leaching conditions. Similarly, two coarse coal refuse samples were placed into lab columns and field barrels. Comparative results suggest the column method was a reasonable predictor of TDS release from the coal mine spoil relative to the two larger scales studied. However, there were significant differences at times during the study, including during initial peak TDS elution (1,750 µS cm⁻¹ in columns vs. 2,250 µS cm⁻¹ in mesocosms). Field leaching also produced a distinct seasonal time-lagged EC pattern that was not observed in the columns. On the other hand, significantly different and dissimilar leaching results were noted for the refuse column vs. barrel leachates, calling into question their prediction ability for refuse.

Browsing by Author "Eick, Matthew J."

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