Rapid rates of coastal wetland loss in Louisiana are widely recognized. One important question of wetland sustainability is how volumetric contributions of roots to wetland soils vary under the influence of different hydrologic regimes. The research presented here specifically investigates the spatial and temporal relationships among the specific gravity of live roots, soil chemistry, and flooding regime for the macrophyte Spartina alterniflora Loisel. in natural, salt marsh, field settings located across southeastern coastal Louisiana. The results of this research propose the existence of a stress-tolerance threshold (beyond which root specific gravity modifications are observed), and highlight the importance of micro-scale factors over macro-scale regional characteristics in determining environmental stresses and the subsequent impact on root specific gravity. A conceptual model is developed linking the interactions of relevant environmental variables, root specific gravity, and the idea of a stress-tolerance threshold.

A research proposal submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / In the past three decades there has been an increased interest in constructed wetlands (CW) and their effectiveness in treating water. The hydraulic efficiency of a CW can be determined by using chemical reactor theory to develop residence time distribution (RTD) parameters such as effective volume (Veff), normalized variance (σ2) and mean residence time (τm). Five experiments were conducted to study the effects on these RTD parameters in a CW by using a glass pilot-scale laboratory rig and varying the inlet-outlet positions. The rig made use of a glass tank 250x250x500mm filled with clear superabsorbent polymer balls as a packing. The clear tank and balls made it possible for the flow to be observed when a FWT red impulse tracer dye was inserted into the system. The flow was photographed at specific time intervals for visual analysis and comparison. . The visual results showed the formation of a hull-shaped velocity profile in all the experiments. The RTD was obtained by collecting tracer samples at specific outlet positions during the course of each experiment. The five inlet-outlet configurations RTD parameters results showed; a straight flow path from a single inlet to outlet yielded the lease desirable hydraulic performance with dead volumes contributing to up to 67% of the CW. An increase in the number of outlets and changing the direction of flow diagonally showed up to a 96% improvement to the effective volume of the system could be achieved when compared with single inline inlet-outlet flow. The best result was achieved by combining the visual and RTD data to make changes to the rigs geometry in order to eliminate dead zones and yielded up to a 148% improvement in the effective volume of the system when compared with single inline inlet-outlet flow. A well designed CW with respect to inlet-outlet position can result in reduced land requirements and construction costs by minimizing the dead volume and improving hydraulic efficiency. / MT2016

The occurrence of the emerging weed Glyceria maxima (Reed sweet-grass) in KwaZulu-Natal and Mpumalanga Province is possibly a threat to aquatic ecosystems. The aim of this study was to determine if G. maxima exhibits traits that indicate its potential for invasiveness. Additional aims included determining environmental factors that influence G. maxima establishment, preferred habitat and its impacts on plant species diversity in the invaded sites. The study was carried out at a dam at Mt. Shannon, Boston, and the Luhane River, Bulwer, both in the KwaZulu-Natal midlands. The littoral zone was divided into five elevational sampling zones in relation to water depth (i.e. from the terrestrial to aquatic habitat). Vegetation sampling was carried out twice in the 2008/09 and 2009/10 growing seasons. Water depth was found to be the major factor that determines the distribution patterns of G. maxima. Glyceria maxima’s preferred habitat was found to be semi-aquatic and aquatic habitats with a water depth of 130 cm. An unplanned fire event at Mt. Shannon Dam resulted in an increase in G. maxima vegetative recruitment. Glyceria maxima’s mode of spread within the study sites was found to be mainly vegetative reproduction as no seedlings were found. This was supported by a very low seed germination percentage (0.3-2%) in the laboratory germination tests although tetrazolium test showed that a considerable percentage of seeds was viable (25-89%; 53% av.). In the 2009/10 season G. maxima tiller density, percentage basal cover and height increased relative to 2008/09 which corresponded with a decline in the abundance of other species growing in the G. maxima stands. This shows that the habitat in which G. maxima is growing is ideal for its spread. Water depth, fire and vegetative reproduction are the main factors that influence G. maxima invasiveness in the littoral zone. Immediate attention should be given to the eradication of G. maxima while the number of the known infestations remains relatively small and fragmented, rather than waiting until the species is having a noticeable impact on riparian and wetland functioning. Glyceria maxima is likely to pose a threat to montane wetlands, which are generally regarded as biodiversity hotspots and water production regions. Keywords: Glyceria maxima, aquatic ecosystems, water depth, vegetative reproduction, seed germination and viability, Invasive.

Thesis (M.S.)--Indiana University, 2007. / Title from screen (viewed on Apr. 27, 2007) Department of Earth Science, Indiana University-Purdue University Indianapolis (IUPUI) Includes vita. Includes bibliographical references.

Prairie wetlands are affected by agricultural activities, in particular herbicide contamination of wetland ecosystems. The environmental fate of herbicides in wetlands is determined by their persistence and transport. Currently, little is known about the persistence of commonly used herbicides in wetland water and sediment. The objective of this dissertation was to determine the importance of wetland sediments in influencing the fate of commonly used herbicides in prairie wetlands.<p> Sediment sorption is an important dissipation pathway for herbicides. The effects of land use on physicochemical properties of wetland sediment, and the associations between these properties and herbicide sorption characteristics for four herbicides (trifluralin, atrazine, 2,4-D and glyphosate), were examined for 17 wetlands.<p> The sorption of herbicides in sediment increased in the order of 2,4-D < atrazine < glyphosate < trifluralin. Overall, sediments from wetlands that were recently cultivated had lower total organic carbon (TOC), total inorganic carbon (TIC), electrical conductivity (EC), exchangeable cation (EXCAT), cation excheageable capacity (CEC), and sorption coefficient (Kd) values (2,4-D, trifluralin, and atrazine) than sediments from semi-permanent and riparian ephemeral wetlands. Although TOC content was correlated to the sorption of 2,4-D, trifluralin and atrazine, riparian wetland sediments despite having a lower TOC content than semi-permanent wetland sediments, had the highest herbicide sorption capacity for 2,4-D, trifluralin and atrazine.<p> To further examine the link between land use and herbicide sorption by sediment, a multi-residue analytical method was developed to quantify seven sulfonylurea herbicides commonly used in crop production (thifensulfuron-methyl, tribenuron-methyl, ethametsulfuron-methyl, metsulfuron-methyl, rimsulfuron, nicosulfuron and sulfosulfuron) in sediment from 17 wetlands. Sediment was extracted with deionized water using pressurized liquid extraction and the resultant extracts were cleaned-up using Oasis HLB solid-phase extraction cartridges. Quantification and confirmation were performed using liquid chromatography interfaced with positive ion electrospray tandem mass spectrometry, and multiple reaction monitoring. Calibration curves were linear with correlation coefficients greater than 0.994 and limits of quantification ranged from 1.0 to 2.0 µg kg-1. Ethametsulfuron-methyl, sulfosulfuron and metsulfuron-methyl, the three most environmentally persistent of the seven sulfonylurea herbicides monitored in this study, were most frequently detected in wetland sediment. The concentrations of sulfonylurea herbicides were higher in sediments from the semi-permanent wetland, which received surface runoff from a larger catchment. <p> To assess the relationship between herbicide dissipation and sorption to sediment, seven commonly used herbicides (glyphosate, dicamba, bromoxynil, 2,4-D, MCPA, mecoprop-P and dichlorprop) were applied to one half of an ephemeral (E) and a semi-permanent (SP) prairie wetland to mimic a direct overspray event, a worst-case scenario for wetland contamination. Water and sediment samples collected over a 77-d study period (early June to late August) were analyzed for herbicide concentration; aminomethylphosphonic acid (AMPA), the degradation product of glyphosate, was also monitored. Glyphosate dissipated rapidly in the water column of each wetland with DT50 values of 3.7 d for wetland E and 6.9 d for wetland SP. The mass of AMPA in each wetland increased with a concomitant decrease in the mass of glyphosate, suggesting that glyphosate degradation was occurring in the water column. In addition, glyphosate was also lost from the water column via sorption to bottom sediment, as evidenced by its detection in sediment samples up to 42-d post-treatment (39.0 224.5 µg kg-1). The DT50 of the other six acid herbicides ranged from 2.3 d (bromoxynil) to 31 d (dichlorprop). The two chiral herbicides, mecoprop-P and dichlorprop, were the most persistent acid herbicides in the water column. Sorption to sediment was also an important dissipation route for these six herbicides in water, especially in wetland E. After 77 d in the semi-permanent wetland and 56 d in the ephemeral wetland, the concentrations of bromoxynil, dicamba and 2,4-D were below the Canadian Water Quality Guidelines for the Protection of Aquatic Life. Concentrations of the more persistent herbicides (mecoprop-P and dichlorprop) remained at levels above the guidelines.<p> Use of bromide ion as a conservative tracer indicated that some of the water loss from both wetlands was via infiltration. Because there was a strong correlation between the decrease in bromide ion and herbicide mass in the water column, it is possible some herbicides were lost from the water column along with the infiltrating water. Infiltration to wetland margins during this part of the growing season would have been largely driven by the riparian vegetation surrounding both wetlands.<p> Overall, this thesis demonstrated the importance of sediment in the dissipation of currently used herbicides in wetland ecosystems. Both laboratory sorption studies and whole-wetland experiments provided insights on the sorptivity of herbicides in sediment as well as their persistence in water and sediment.

Wetlands are very valuable ecosystems as they play an integral role in wildlife habitat, water management and greenhouse gas exchange. The exchange of carbon dioxide between prairie wetlands and the atmosphere is poorly understood. The purpose of this study was to identify rates and trends in the growing season carbon dioxide flux from the riparian and open-water zone of a prairie pothole wetland. In addition to providing core open water and riparian zone CO2 flux measurements, relationships between variations in CO2 flux and characteristics of the wetland���s biological, biochemical and hydrometeorological state were assessed. The CO2 effluxes from the pond during the summer of 2006 were approximately four times greater than in 2005, but were much lower in the early fall. Algal chlorophyll-a concentrations were greater in 2005 than 2006 for all three algal assemblages. The mean chlorophyll-a concentrations in 2005 for epiphyton, phytoplankton and metaphyton were 2.75 �� 0.62 g m-2, 87 �� 24 �� L-1, and 318 �� 187 g m-2 respectively. In 2006 mean concentrations for the same assemblages were 0.008 �� 0.001 g m-2, 8 �� 2 �� L-1, and 27 g m-2 respectively. The amount of DOC in the open water in August of 2005 (140 mg DOC L-1) was 70 times greater than in July of 2005 (2 mg DOC L-1). DOC ranged from 30 to 52 mg DOC L-1 in 2006. Although highly productive, the pond proper appeared to be a source of DOC which is concurrent with literature from littoral zone and shallow inland waters. Soil respiration increased upslope from the wetland to the cropped upland in 2005. Net ecosystem exchange was greater in the cattail ring surrounding wetland than the grass and sedge zone beyond the cattails. The riparian vegetation may have been water stressed in late-July (at the climax of the dry period) when net ecosystem exchange decreased. Diurnal net ecosystem exchange in the riparian zone indicates uptake during the day and emissions at night. From this data it appears that the riparian zone may have acted as a CO2 sink in June, July and August and a source in April. / October 2008

Prairie wetlands are affected by agricultural activities, in particular herbicide contamination of wetland ecosystems. The environmental fate of herbicides in wetlands is determined by their persistence and transport. Currently, little is known about the persistence of commonly used herbicides in wetland water and sediment. The objective of this dissertation was to determine the importance of wetland sediments in influencing the fate of commonly used herbicides in prairie wetlands.<p> Sediment sorption is an important dissipation pathway for herbicides. The effects of land use on physicochemical properties of wetland sediment, and the associations between these properties and herbicide sorption characteristics for four herbicides (trifluralin, atrazine, 2,4-D and glyphosate), were examined for 17 wetlands.<p> The sorption of herbicides in sediment increased in the order of 2,4-D < atrazine < glyphosate < trifluralin. Overall, sediments from wetlands that were recently cultivated had lower total organic carbon (TOC), total inorganic carbon (TIC), electrical conductivity (EC), exchangeable cation (EXCAT), cation excheageable capacity (CEC), and sorption coefficient (Kd) values (2,4-D, trifluralin, and atrazine) than sediments from semi-permanent and riparian ephemeral wetlands. Although TOC content was correlated to the sorption of 2,4-D, trifluralin and atrazine, riparian wetland sediments despite having a lower TOC content than semi-permanent wetland sediments, had the highest herbicide sorption capacity for 2,4-D, trifluralin and atrazine.<p> To further examine the link between land use and herbicide sorption by sediment, a multi-residue analytical method was developed to quantify seven sulfonylurea herbicides commonly used in crop production (thifensulfuron-methyl, tribenuron-methyl, ethametsulfuron-methyl, metsulfuron-methyl, rimsulfuron, nicosulfuron and sulfosulfuron) in sediment from 17 wetlands. Sediment was extracted with deionized water using pressurized liquid extraction and the resultant extracts were cleaned-up using Oasis HLB solid-phase extraction cartridges. Quantification and confirmation were performed using liquid chromatography interfaced with positive ion electrospray tandem mass spectrometry, and multiple reaction monitoring. Calibration curves were linear with correlation coefficients greater than 0.994 and limits of quantification ranged from 1.0 to 2.0 µg kg-1. Ethametsulfuron-methyl, sulfosulfuron and metsulfuron-methyl, the three most environmentally persistent of the seven sulfonylurea herbicides monitored in this study, were most frequently detected in wetland sediment. The concentrations of sulfonylurea herbicides were higher in sediments from the semi-permanent wetland, which received surface runoff from a larger catchment. <p> To assess the relationship between herbicide dissipation and sorption to sediment, seven commonly used herbicides (glyphosate, dicamba, bromoxynil, 2,4-D, MCPA, mecoprop-P and dichlorprop) were applied to one half of an ephemeral (E) and a semi-permanent (SP) prairie wetland to mimic a direct overspray event, a worst-case scenario for wetland contamination. Water and sediment samples collected over a 77-d study period (early June to late August) were analyzed for herbicide concentration; aminomethylphosphonic acid (AMPA), the degradation product of glyphosate, was also monitored. Glyphosate dissipated rapidly in the water column of each wetland with DT50 values of 3.7 d for wetland E and 6.9 d for wetland SP. The mass of AMPA in each wetland increased with a concomitant decrease in the mass of glyphosate, suggesting that glyphosate degradation was occurring in the water column. In addition, glyphosate was also lost from the water column via sorption to bottom sediment, as evidenced by its detection in sediment samples up to 42-d post-treatment (39.0 224.5 µg kg-1). The DT50 of the other six acid herbicides ranged from 2.3 d (bromoxynil) to 31 d (dichlorprop). The two chiral herbicides, mecoprop-P and dichlorprop, were the most persistent acid herbicides in the water column. Sorption to sediment was also an important dissipation route for these six herbicides in water, especially in wetland E. After 77 d in the semi-permanent wetland and 56 d in the ephemeral wetland, the concentrations of bromoxynil, dicamba and 2,4-D were below the Canadian Water Quality Guidelines for the Protection of Aquatic Life. Concentrations of the more persistent herbicides (mecoprop-P and dichlorprop) remained at levels above the guidelines.<p> Use of bromide ion as a conservative tracer indicated that some of the water loss from both wetlands was via infiltration. Because there was a strong correlation between the decrease in bromide ion and herbicide mass in the water column, it is possible some herbicides were lost from the water column along with the infiltrating water. Infiltration to wetland margins during this part of the growing season would have been largely driven by the riparian vegetation surrounding both wetlands.<p> Overall, this thesis demonstrated the importance of sediment in the dissipation of currently used herbicides in wetland ecosystems. Both laboratory sorption studies and whole-wetland experiments provided insights on the sorptivity of herbicides in sediment as well as their persistence in water and sediment.

In this study, we discussed the treatment efficiencies of different types of industrial wastewaters by several lab-scale constructed wetlands. The purpose this study is to decrease certain pollutants in the effluents from the industrial wastewaters treatment plants investivate the feasibility of water reuse and recovering. We divided the experiment into two stages, and three types of industry wastewaters ,including paper, steel and refiring, are in this study. In the first stage, the treatment efficiencies of controlling the flow rate at 6 mL/min higher that those controlling at 4 mL/min. However, sinece the amounts of phosphur were smalls in the industrial weatewaters, the removal efficiencies are not high enough. Thus, we added sewage and phousphate into the wastewaters in second stage of experiments with the best ratio of N : P of 4 : 1. The performance work of these two stage experiments did help to clean the nutrient of nitrogenous in the industrial wastewater, especially the refining industry comparing to the other two types of industries.

Thesis (M.S.)--Youngstown State University, 2009. / Includes bibliographical references (leaves 51-53). Also available via the World Wide Web in PDF format.

Thesis (M.Sc.(Botany))--University of Pretoria, 2004. / Includes summary. Includes bibliographical references (leaves 162-169).