No description available.

No description available.

Riparian buffer zones, adjacent to waterways, may protect water quality by intercepting and removing nitrogen in runoff from agricultural land. This research comprised four parts: (1) a field study of nitrogen buffering by differently vegetated riparian zones in a United Kingdom (UK) sheep-grazed pastoral catchment; (2) a field study of surface and subsurface runoff hydrology, and nitrogen flux, in a UK riparian wetland; (3) a laboratory study ((^15)N tracer-isotope dilution) of microbial inorganic nitrogen production and removal processes in the UK riparian wetland soil; and (4) a laboratory microcosm study ((^15)tracer) of nitrate removal processes in bare and plant-inhabited (Glyceria declinata) New Zealand (NZ) riparian wetland soil. Dissolved organic nitrogen and ammonium were generally more important components of subsurface runoff than nitrate in the three UK riparian zones. All riparian zones were poor buffers having minimal effect on the nitrogen concentration of subsurface runoff. In the UK riparian wetland site subsurface (saturated zone) and surface 'preferential flow paths' typically conveyed large quantities of catchment runoff rapidly into, and across the site, and hindered nitrogen buffering. However, under low flow conditions, runoff-riparian soil contact increased and the wetland decreased the catchment nitrogen flux by 27%. In the UK riparian wetland soil most nitrate removal was attributable to denitrification (87- 100%) as opposed to dissimilatory nitrate reduction to ammonium (DNRA) (0-13%) and immobilisation (0-10%). Total ((^14)N+(^15)N) transformation rates for these processes were 1.3-47, 0.5-1.5 and 0.6-2.5 μg N g soil(^-1) hr(^-1) respectively. In the NZ riparian wetland soil Glyceria declinata assimilated 11-15% of nitrate but, more importantly, increased soil oxidation and altered the proportions of nitrate removal attributable to denitrification (from 29% to 61-63%) and DNRA (from 49 to <1%), but not immobilisation (22-26%). Denitrification and, thus, nitrogen buffering might be enhanced, in some riparian zones by increasing the extent of moderately anoxic soil with plants that release oxygen from their roots or with water table management.

Determining the root uptake of xenobiotic organic chemicals into plants is critical for assessing the human and ecological health risks associated with the consumption of plants growing in contaminated environments. Root uptake of xenobiotic organics occurs passively in conjunction with transpiration and the transport from root to shoot is ultimately controlled by passage through one or more lipid root membranes. The transpiration stream concentration factor (TSCF), the ratio between the concentration of a chemical in the xylem to that in the solution used by the roots, is used to describe the relative ability of an organic chemical to be passively transported from root to shoot. However, relatively few experimental TSCF values exist due to the cost and the lack of regulatory requirements for generating such data. Where literature data exist for chemicals having more than one TSCF, the variability is often large due to the lack of standardized methods and difficulty in accounting for metabolism and volatilization losses occurring during the uptake experiments. Because of the scarcity of experimental values, estimated TSCFs are often used. Widely cited estimation approaches relating TSCF and the logarithm octanol/water partition coefficient (log KOW) suggest that only compounds that are in the intermediate lipophilicity range (log KOW = 2) will be taken up and translocated by plants. However, recent data for highly water soluble compounds such as 1,4-dioxane, MTBE, and sulfolane suggest that these estimation techniques should be critically reviewed. To re-evaluate the relationship between TSCF and log Kow, TSCFs were measured for 25 organic chemicals ranging in log KOW from -0.8 to 5 using an improved pressure chamber technique. The technique provides an approach for efficiently generating consistent plant uptake data. By using this data, a new mass transfer model relating TSCF and log KOW was developed that indicates that neutral, polar organic compounds are most likely taken up by plant roots and translocated to shoot tissue. An extensive review of literature TSCF studies supports the updated model.

A numerical model is presented to describe solute transport in groundwater coupled to sorption by plant roots, translocation into plant stems, and finally evapotranspiration. The conceptual model takes into account both Root Concentration Factor, RCF, and Transpiration Stream Concentration Factor, TSCF for chemicals which are a function of Kow. A similar technique used to simulate the solute transport in groundwater to simulate sorption and plant uptake is used. The mathematical equation is solved using finite difference technique to solve for the concentration at any grid cell with respect to time. The new package is integrated into SEAM3D to create a new SEAM3D Plant Uptake Package, or PUP. The model is then verified by comparing results for root sorption in one side to the SEAM3D Reaction Package, and results for plant uptake to the SEAM3D Source Sink Mixing Package. The verification results showed an excellent match, which led to using the new package in a series of design application scenarios to evaluate phytoremediation effect. Hypothetical design scenarios included: 1) the effect of a phytoremediation system dimensions, 2) the effect of phytoremediation plant density or maximum ET rate, 3) the effect of out-flux of the phytoremediation with respect to the natural aquifer in-flux, and 4) the effect of using a phytoremediation system when the source of contamination is removed. For all the previous study cases, the results evaluate the effect on: 1) contaminant concentrations downstream the source (expressed in plume length at a concentration 1% of the source concentration), 2) solute mass removal from the aquifer, and 3) mass-flux changes at different cross-sections downstream the contaminant source. The results indicating the followings: 1) the width of the phytoremediation system, WET, has a limited effect on the solute mass-removal; 2) high tree density close to the contaminant source has a greater effect on solute mass removal relative to uniform density of trees planted over the entire plume; 3) the width of the ET area will have only a slight effect on the mass removal if the TSCF value is small; 4) as the value of TSCF gets lower, the efficiency of solute mass uptake is lower, and thus the solute concentration in groundwater is higher regardless of the quantity of water transpired; 5) dynamic steady-state plume dimensions (specially the plume length) are affected by the groundwater in-flux, which will control the dimensions and density of a phyto system; 6) splitting the phyto system into two halves does not have the same outcome of having one piece of area closer to the contamination site; 7) using a phyto system after the contamination source is removed led to increasing the solute concentration in the areas of the trees and decreases the concentration in the areas downstream the trees. The alternative model gives more options for simulation of solute mass uptake by plants by making use of field and lab data between the solute dissolved concentration in groundwater C, and solute mass in tree's core M to select a modeling category of three: Linear (ISO-1), Freundlich (ISO-2), and Langmuir (ISO-3). Each modeling option depends on the designer selection according to the fitted equation parameters between, C and, M. In terms of conservative results, ISO-1, and ISO-2 give less mass removal results than ISO-3 in case of sources with low concentrations. ISO-2, and ISO-3 give less mass removal results than ISO-1 in case of sources with high concentrations. / Ph. D.

Direct transpiration rates and plant uptake of naphthalene by a hybrid poplar phytoremediation system located in Oneida, Tennessee were determined using hydrologic and groundwater concentration data. Water table recession analysis techniques were employed to determine direct transpiration rates from the saturated zone of the shallow, unconfined aquifer underlying the site. Direct transpiration rates varied over the growing season (late March to mid-October), with a maximum and mean daily direct transpiration of 0.0100 and 0.0048 feet/day, respectively. During 2004, the maximum direct transpiration rate was observed in May, and rates declined starting in June due to an associated decline in the water table. A technique was developed to estimate the volumetric transpiration rate of each tree based on the breast-height diameters and seasonally variable direct transpiration rates. During peak transpiration, the larger trees at the study site were estimated to directly transpire 4 to 13 gallons per day per tree. Plant uptake rates of naphthalene were estimated by superimposing spatial data (volumetric transpiration rates and naphthalene concentration in groundwater). The mass loss rate of naphthalene from the aquifer as a result of plant uptake during July 2004 was 335 mg/day which only represents 0.117% of the aqueous mass plume. Monthly groundwater profiles showed a decrease of the saturated thickness beneath the system of hybrid poplars between the dormant and active season. This study suggests direct transpiration rates and plant uptake of naphthalene are dependent on variables including climatic parameters, magnitude of the saturated thickness, and the concentration of naphthalene in groundwater. / Master of Science

No description available.

Challenges at hazardous waste and contaminated sites are persistent, complex, and multifactorial, and unfortunately the progress in implementing solutions is slow. This delay can be attributed to the lack of collaboration, information transfer to the end-user, and partnership building among academia, government and the affected community. As a solution, Environmental Research Translation (ERT), a framework that is rooted in existing participatory models, and encompasses many of the key principles from informal science education and community-based participatory research is proposed. The ERT framework lead to a community-academic partnership called: Gardenroots: The Dewey-Humboldt, Arizona Garden Project. Vegetable gardening in contaminated soils presents a health hazard. A controlled greenhouse study was conducted in parallel with a co-created citizen science program to characterize the uptake of arsenic by homegrown vegetables near the Iron King Mine and Humboldt Smelter Superfund Site in Arizona. Community members, after training, collected soil, water and vegetable samples from their household garden. The greenhouse and home garden arsenic soil concentrations ranged from 2.35 to 533 mg kg⁻¹. In the greenhouse experiment four vegetables were grown in three different soil treatments and a total of 63 home garden produce samples were obtained from 19 properties neighboring the site. All vegetables accumulated arsenic, ranging from 0.01 - 23.0 mg kg⁻¹ dry weight. Bioconcentration factors were determined and arsenic uptake decreased in the order: Asteraceae > Brassicaceae >> Amaranthaceae > Cucurbitaceae > Liliaceae > Solanaceae > Fabaceae. Concentrations of arsenic measured in potable water, soils and vegetable samples were used in conjunction with reported US intake rates to calculate daily dose, excess cancer risk and Hazard Quotient for arsenic. Relative arsenic intake dose decreased in order: potable water > garden soils > well washed homegrown vegetables, and on average, each accounted for 79, 14 and 7%, of a residential gardener's daily arsenic intake dose. The IELCR ranges for vegetables, garden soils and potable water were 10⁻⁸ to 10⁻⁴, 10⁻⁶ to 10⁻⁴; and 10⁻⁵ to 10⁻², respectively. The ERT framework improved environmental health research, information transfer, and risk communication efforts. Incorporating the community in the scientific process lead to individual learning and community-level outcomes.

Perfluoroalkyl carboxylates (PFCAs) and perfluoroalkane sulfonates (PFSAs)are anthropogenic fluorinated surfactants that have been detected in almost every environmental compartment studied, yet their production and applications are far outweighed by those of other higher molecular weight fluorinated surfactants used in commerce. These fluorinated surfactants are widely incorporated in commercial products, yet their post-application fate has not been extensively studied. This thesis examines various biological and environmental processes involved in the fate of these surfactants upon consumer disposal. Specific focus was directed towards the environmental chemistry of polyfluoroalkyl phosphate esters (PAPs), perfluoroalkyl phosphonates (PFPAs), and perfluoroalkyl phosphinates (PFPiAs), and their potential roles as sources of perfluoroalkyl acids (PFAAs) in the environment. PAPs are established biological precursors of PFCAs, while PFPAs and PFPiAs are newly discovered PFAAs in the environment. Incubation with wastewater treatment plant (WWTP) microbes demonstrated the ability of PAPs to yield both fluorotelomer alcohols (FTOHs), which are established precursors of PFCAs, and the corresponding PFCAs themselves. WWTP biosolids-applied soil-plant microcosms revealed that PAPs can significantly accumulate in plants along with their degradation metabolites. This has implications for potential wildlife and human exposure through the consumption of plants grown and/or livestock raised on farmlands that have been amended with contaminated biosolids. A number of compound-and environmental-specific factors were observed to significantly influence the partitioning of PFPAs and PFPiAs between aqueous media and soil, as well as, aquatic biota during sorption and bioaccumulation experiments respectively. In both processes, PFPAs were primarily observed in the aqueous phase, while PFPiAs predominated in soil and biological tissues, consistent with the few environmental observations of these chemicals made to date. Detection of the PAP diesters (diPAPs), PFPiAs, and fluorotelomer sulfonates (FTSAs),all of which are used commercially, in human sera is evidence of human exposure to commercial fluorinated products, but the pathways by which this exposure occurs remain widely debated. Overall, this work presents novel findings on the environmental fate of commercial fluorinated surfactants and each of the process studied shows a clear link between the use of commercial products and the fluorochemical burden currently observed in the environment.

Perfluoroalkyl carboxylates (PFCAs) and perfluoroalkane sulfonates (PFSAs)are anthropogenic fluorinated surfactants that have been detected in almost every environmental compartment studied, yet their production and applications are far outweighed by those of other higher molecular weight fluorinated surfactants used in commerce. These fluorinated surfactants are widely incorporated in commercial products, yet their post-application fate has not been extensively studied. This thesis examines various biological and environmental processes involved in the fate of these surfactants upon consumer disposal. Specific focus was directed towards the environmental chemistry of polyfluoroalkyl phosphate esters (PAPs), perfluoroalkyl phosphonates (PFPAs), and perfluoroalkyl phosphinates (PFPiAs), and their potential roles as sources of perfluoroalkyl acids (PFAAs) in the environment. PAPs are established biological precursors of PFCAs, while PFPAs and PFPiAs are newly discovered PFAAs in the environment. Incubation with wastewater treatment plant (WWTP) microbes demonstrated the ability of PAPs to yield both fluorotelomer alcohols (FTOHs), which are established precursors of PFCAs, and the corresponding PFCAs themselves. WWTP biosolids-applied soil-plant microcosms revealed that PAPs can significantly accumulate in plants along with their degradation metabolites. This has implications for potential wildlife and human exposure through the consumption of plants grown and/or livestock raised on farmlands that have been amended with contaminated biosolids. A number of compound-and environmental-specific factors were observed to significantly influence the partitioning of PFPAs and PFPiAs between aqueous media and soil, as well as, aquatic biota during sorption and bioaccumulation experiments respectively. In both processes, PFPAs were primarily observed in the aqueous phase, while PFPiAs predominated in soil and biological tissues, consistent with the few environmental observations of these chemicals made to date. Detection of the PAP diesters (diPAPs), PFPiAs, and fluorotelomer sulfonates (FTSAs),all of which are used commercially, in human sera is evidence of human exposure to commercial fluorinated products, but the pathways by which this exposure occurs remain widely debated. Overall, this work presents novel findings on the environmental fate of commercial fluorinated surfactants and each of the process studied shows a clear link between the use of commercial products and the fluorochemical burden currently observed in the environment.