Ph.D. / Wetlands play an integral role in the hydrological cycle and biodiversity. Despite this, wetlands have been neglected in terms of research and monitoring in South Africa. This lack of research has become even more insufficient when it comes to endorheic wetlands. Endorheic wetlands in South Africa are known as pans. Pans are isolated depressions that for through wind erosion are generally shallow and lack an integrated drainage. Water gain is depended on rainfall and surface runoff and water loss is largely due to evaporation. Pans can be either ephemeral in nature or can remain inundated for long periods of time. There are close to 5000 pans in the study area of the Mpumalanga province of South Africa. An estimated 40% of these pans are perennial in nature. The little information on the ecology of pans is all focussed on those systems that are ephemeral. The lack of knowledge is, however, not restricted to the ecology of perennial pans but also the management tools available for these ecosystems. Whereas a variety of methods are available to determine the quantity and quality of water needed to sustain riverine systems (and wetlands connected to rivers), there are no such methods for pans. Especially important is the lack in standardised methods to assess the ecological integrity of perennial pans. This is important as perennial pan ecosystems are increasingly under threat from an increase in coal mining and agricultural activities in Mpumalanga. Coal mining activities have increased in the study area due to both an increase in energy demands and the ease of mining coal deposits in the study area. The lack in standardised methods could be as a direct result of the lack in knowledge of the ecology of the perennial pans. The aim of this study was thus to develop standardised methods for assessing the ecological integrity of perennial pans in Mpumalanga by studying the ecology of the pans. The study thus uses a fundamental approach to reach certain applied goals. To achieve the aim, a total of nine pans were included in the study of which seven were surveyed seasonally for two years and two were sampled on a single occasion. Five of these pans were located in the Mpumalanga Lake District (MLD) and were in a relatively pristine condition. The other four pans were impacted either by agricultural activities, mining activities or both. During these surveys, various components of the ecosystem were studied. These components included the spatial and temporal variations in the abiotic components like the physico-chemical characteristics, habitat quality and quantity, and the sediment characteristics. It also included the spatial and temporal variations in the vegetation communities surrounding the pans and the aquatic invertebrate communities within the pans. The aquatic invertebrate communities were assessed based on a taxonomic approach (diversity) and functional approach (biological traits).

Indicator organisms like coliforms, E. coli and enterococci are normally associated with the intestinal tract of warm-blooded animals, and can thus be used for indicating fecal contamination of water. This study investigated the removal efficiency of indicator organisms in a free water surface constructed wetland used for additional treatment of municipal wastewater. The species composition of enterococci and the prevalence of the tetracycline resistance gene tetM were also investigated. Samplings were done at five different sites: at the inlet, within and at the outlet of the wetland, as well as upstream and downstream of the wetland outlet into the adjoining river. A total of 86 enterococci isolates were characterized as E. faecalis, E. faecium or other Enterococcus spp., and the two former were also screened for the tetM gene. The investigated wetland showed a high removal rate of indicator organisms, with a removal of approximately 98%. E. faecium was identified as the predominant species in the wetland at a mean of 55.8%. In comparison, only 9.3% were E. faecalis, while other Enterococcus spp. were found to comprise 34.9%. Of the 56 isolates identified as E. feacalis or E. faecium 10.7% were positive for the tetM gene. The high removal of bacteria shown by this investigation provides further evidence of the benefits of constructed wetlands on wastewater treatment. It also offers a first indication of the Enterococcus spp. composition in Ekeby wetland, Eskilstuna, Sweden, and shows that the prevalence of the tetM gene is relatively low at this point in time.

Literature has not yet seen a contribution involving the description of successional patterns of mosquitoes (Diptera: Culicidae) inhabiting discarded automobile tires in sylvan areas nor an investigation into the macro- and micro-environmental factors that may influence the seasonal shifts in species composition and abundance in that respective habitat. Waste tires in undeveloped forests are a hazard to human and animal health because they can support a population of vector mosquitoes. Locating productive waste tire mosquito habitats is problematic in wooded areas but is crucial for diminishing pathogen transfer in areas where humans have regular access to forests because of possible zoonotic disease transmission. The intentions of this study were 1) to describe the ecological succession patterns of mosquitoes in waste tires in a subtropical wetland and upland forest and 2) to create a database on which regressive geo-spatiotemporal models locating unidentified productive waste tires in sylvan zones can be built. The entomological research conducted here did not confirm the hypothesis that Aedes albopictus (Skuse) would be the dominant species in all the tires at all the study sites. There appeared to be seasonal trends in mosquito production despite the general constant warmth and rainfall levels year-round in subtropical Tampa, Florida. However, the findings of this research indicates that climatic conditions alone do not sufficiently explain spatiotemporal variation in mosquito populations. Rather, the effects of weather are heterogeneous at the microcosmic level, which has a more direct impact on ecological interactions between the different species found here and their abiotic environment.

The Palmiet wetlands located along the Kromrivier in the Eastern Cape province of South Africa have experienced severe degradation through gully erosion during the past decennia which has been threatening the water quality and water security of large towns in the Nelson Mandela Metropolitan hub. Water scarcity is a growing problem in this region as a result of land degradation and growing erratic rainfall patterns. The main causes of wetland degradation are argued to be land use and land cover change. With the aim of protecting the wetlands along the Kromrivier a total of eleven large gabion and concrete erosion-control structures were constructed between the 2002 and 2013 by the government initiate Working for Wetlands. This study aims to map the groundwater table in order to derive how erosion-control structures and gully erosion affect groundwater dynamics along the Kromrivier. This was achieved by several steps. Firstly, water table elevations were measured along several transects by installing a series of piezometers which allowed do investigate how the structures affected the water table. This also allowed for a comparison in groundwater dynamics between eroded and non-eroded reaches so that effects of gully erosion could be identified and potential causes discussed. Secondly, the analysis of aerial images allowed for the development of the aerial extent of the Palmiet wetland and gullies to be seen over a ten year period and longitudinal profiles provided specific characteristics of the wetland and gullies. Lastly, particle size distribution and organic matter content were analyzed as groundwater flow and gully erosion can vary greatly depending on soil characteristics. The hydraulic gradient was highest in proximity to the structures as a result of the created potential induced by the drop in surface water elevation. The radius of influence to where the structures were affected the water table was estimated to be approximately 40 m from the channel. Further away from the channel, the gradual slope of the water table indicated that the porous gabion side walls of the structures did not affect the water table. The groundwater flow is determined by Darcy's Law and the relatively flat water table along the non-eroded reaches of site A displayed local drainage points, thereby indicating variations in the local flow direction. In May the water table along the non-eroded reaches was sloping away from the channel resulting in an area of groundwater discharge with respect to the channel. Not only was the water table generally higher during August, the regime had also changed, indicating a potentially large seasonal variability. Along the eroded reaches downstream from the structures the water table was above the gully bottom during both months resulting in an area of groundwater recharge with respect to the channel. Also here the regime had changed from an approximately constant hydraulic gradient sloping towards the channel during May to a water table with a divide in flow direction. Since their implementation in 2003, the structures have been effective with respect to preventing the headcut in the main channel from migrating further upstream. However, the gullies downstream of the structures had significantly increased in width between 2003 and 2013 and the Palmiet wetland had also slightly decreased in size during the same period. However, it was unclear whether this decrease was part of the longer term ongoing trend or part of a shorter term cycle and/or seasonal fluctuation. For a gully bank to collapse, the shear strength of the slip surface needs to be exceeded and this often occurs because of an increase in pore water pressurewhich causes a reduction in shear strength. A large gully height of up to 4 m with nearly vertical slopes, a water table above the gully bottom and an increase in moisture content between May and August indicated that it is not unlikely that a high pore water pressure. played a significant role in the slumping of the gully walls. The two structures together were responsible for an surface water elevation difference of 7.76 m. Through damming this resulted in an elevated water table in the upstream Palmiet wetland, thereby increasing the saturation and promoting diffuse flow across the wetland. However, the structures also trap most of the sediment in upstream direction which appears to have resulted in the de-stabilization of the downstream streambed at site A as these eroded reaches now receive a significantly lower sediment load. By increasing the retention volume in the wetland, the structures also facilitated in ensuring flood retention as the wetland could now hold more water during high flows, thereby cutting off the peak flow. As gully erosion is known to occur during periods of high flow it is not unreasonable to argue that slumping of the gully walls would have been more severe without the structures in place. In this sense the structures increase the water quality and decrease the flux of sediment where the latter leads to a decrease in the sedimentation rate of the downstream Churchill Dam. Consequently, this contributes to securing the fresh water supply to towns in the Nelson Mandela Metropolitan hub. The discovery of Palmiet rests up to 2.6 m below the surface indicated that cycles of gully erosion followed by the re-establishment of Palmiet have been occurring in this valley for thousands of years. However, it seemed that land use and land cover changes had accelerated gully erosion during the past decades resulting in a loss of Palmiet wetland at a rate which was beyond 'natural'. Even though the structures could be seen as disruptions of long term natural cycles, they are in favor of the well-being of mankind as they protect the wetlands to a certain extent. The main results of this study provided a basic understanding of how the water table behaves in response to the structures and along eroded and non-eroded reaches of the Kromrivier. Furthermore, this study discussed the larger scale affects of the structures and showed how the gullies and the aerial extent of the Palmiet wetland have evolved since the implementation of the structures in 2003. In order to manage these Palmiet wetlands more effectively in the future, it is highly important that groundwater dynamics, gully erosion and the size and health of the wetland are annually monitored in order to get a more accurate idea of how effective these structures are. This new obtained knowledge could also assist in managing other peat lands in South Africa more effectively.

At the end of the 20th century, the combination of climatic and anthropogenic events resulted in hyper salinity conditions in the coastal wetland Ciénaga Grande de Santa Marta (CGSM), Colombia. Although salinity concentrations are generally related to the type and quantity of water entering and exiting a wetland and to its internal hydrological dynamics, there have been no up to date hydrological studies on the CGSM. Here we show how a water budget can be used as a first-order of approximation to describe the CGSM's hydrology, despite data limitations. We collected hydroclimatic data to calculate and analyze the fluxes of water entering and exiting CGSM and their corresponding uncertainties. We find that the water budget is mostly affected by the precipitation regime, a result connected to studies of regional El Niño/La Niña effects. Scenario analyses show that contribution of freshwater from the streams coming down from the Sierra Nevada Mountain Range on the eastern side of CGSM is currently larger than that of the channels draining from Magdalena River to the west, in contrast to the general focus on the western side. However, Monte Carlo simulations suggest that the eastern freshwater inflow is insignificant in affecting the hydrological response of CGSM. These results outline the need to (1) increase understanding of the internal connectivity and circulation of CGSM and (2) further investigate the effect of agriculture on the eastern side of CGSM.

Nous avons identifié le rôle de la distribution solide et l’implication de facteurs (potentiel d’oxydoréduction, anions compétiteurs, activité biologique, matière organique (MO)) dans la mobilité de l’arsenic (As) et l’antimoine (Sb) dans un sol de zone humide (ZH) agricole. Pour cela, nous avons effectué i) un suivi de la physico–chimie de l’eau interstitielle de la ZH et ii) des incubations en batch du sol de surface de la ZH (0–20/30 cm). En parallèle, nous avons déterminé la distribution solide de As et Sb sur le sol de la ZH à différentes profondeurs (0–130 cm). Nous avons démontré que As est accumulé à la surface du sol avec une association préférentielle avec les oxyhydroxydes de Fe/Mn « amorphes » (59% de As total) en présence de taux élevés de MO. En conditions réductrices, As est fortement solubilisé (jusqu’à 20% de la teneur en As total) contrairement aux conditions oxydantes ce qui est associé i) à la dissolution des oxyhydroxydes de Fe/Mn catalysée par l’activité microbienne et ii) au changement de la spéciation inorganique de As sous forme de As(III) (espèce plus mobile que As(V)). Pour ce qui est de Sb, il est accumulé à la surface du sol avec i) une distribution plus étendues avec les phases solides (27% et 15% dans les oxyhydroxydes de Fe/Mn « amorphes » et « cristallins », 21% dans la MO et 32% dans la fraction résiduelle) et ii) une affinité directe pour la MO contrairement à As. La mobilisation de Sb est favorisée en conditions oxydantes (jusqu'à 5 μg.L–1) en présence de MO dissoute dans l’eau interstitielle et est limitée en conditions réductrices (<3%) (0,2 μg.L–1 dans l’eau interstitielle et 1,5 μg.L–1 dans les batch). Cette mobilité en conditions réductrices est attribuée i) à la dissolution réductrice des oxyhydroxydes de Fe/ Mn catalysée par l’activité microbienne réductrice du sol et ii) au possible changement d’état d’oxydation de Sb sous forme de Sb(III) (espèce moins mobile que Sb(V)). En conditions réductrices, l’apport de 50 mg.L–1 de nitrates et de 20 mg.L–1 de phosphates au sol a engendré une mobilisation plus importante de As et Sb (d’un facteur 2,3 et 1,6, respectivement) qui est attribuée à une possible amplification de la respiration microbienne du sol causant une production plus importante en ions hydrogénocarbonates qui en plus des ions phosphates favoriserait la mobilisation de As et Sb par des effets de compétition. / In this study, we evaluated the effect of i) solid-phase distribution and ii) biophysico–chemical factors (redox potential (Eh), competing anions, microbial activity, organic matter (OM)) on the mobility of arsenic (As) and antimony (Sb) in an agricultural wetland soil. For that, we first performed a physico–chemical monitoring of wetland porewater (field scale) then we conducted controlled batch incubations of the wetland soil (0–20/30 cm) (batch scale). The solid–phase distribution of As and Sb in wetland soil was also performed at different soil depths (0–130 cm). We showed that the highest As content was found in the upper soil layers (0–40 cm) with a preferential association to “amorphous” oxyhydroxydes (59% of total As) in presence of high levels of OM. Under reducing conditions, As was highly solubilized at both field and batch scale (up to 20% of the total As content) which was induced by i) the dissolution of Fe/Mn oxyhydroxides enhanced by soil microbial activity and ii) As(V) reduction into As(III) (very mobile specie). On the other hand, Sb mobilization was enhanced under oxidizing conditions at field scale (up to 5 μg.L–1) with the concomitant occurrence of dissolved OM (up to 93 mg.L–1) and was rather limited under reducing conditions (<3% of the total Sb content; 0.2 μg.L–1 at field scale and up to 1.5 μg.L–1 at batch scale). The mobility behavior of Sb was attributed to i) the dissolution of Fe/Mn oxyhydroxides catalyzed by microbial activity, ii) the possible occurrence of Sb in its less mobile form (Sb(III)) under reducing conditions and iii) probable DOM–induced mobilization under oxidizing conditions. Under reducing conditions, the addition of nitrate (50 mg.L–1) and phosphate (20 mg.L–1) to wetland soil, enhanced As and Sb mobilization by factors of 2.3 and 1.6 which was suggested to be caused by the combined competing effect of phosphate and hydrogenocarbonate ions; the latter one resulting from a possible enhanced microbial activity.

Le phosphore (P) est un facteur de contrôle de l’eutrophisation. Sa présence dans les masses d’eau est liée en partie à des émissions diffuses agricoles. L'objectif de cette thèse a été d'identifier et de quantifier les mécanismes à l'origine des transferts de P diffus, par une démarche intégrant analyse de données d'observations multi-échelle et modélisation.L'analyse d'une chronique de chimie de l'eau à l'exutoire d'un petit bassin versant agricole a révélé que les formes particulaires et dissoutes du P avaient des origines différentes dans le paysage, et étaient transférées de manière indépendante. Le P particulaire provient des sédiments du cours d'eau, de l'érosion des berges et occasionnellement d'épisodes érosifs dans les versants. Le P dissous provient des sols de la zone riparienne; il est transféré par écoulement de subsurface lorsque les fluctuations de nappe créent une connexion hydrologique avec la rivière.Un suivi multi-site de la concentration en P dans l'eau des sols ripariens a permis de mettre en évidence que la nappe agissait non seulement sur le transfert, mais aussi sur la solubilisation du P. Deux moments importants ont été identifiés : la période de sécheresse estivale est favorable à la constitution d'un pool de P mobile dans les sols, exporté à l'automne; lorsque la nappe stagne dans les sols, la dissolution réductrice des oxydes de Fer provoque un second relargage de P. Un modèle couplé hydrologie-biogéochimie a permis de préciser le rôle de la nappe, de la teneur en P des sols et des variations d'humidité et de température. Une analyse de l' / Phosphorus (P) is a controlling factor of eutrophication. Its presence in water bodies is partly due to agricultural diffuse emissions. The objective of this thesis was to identify and quantify the processes controlling diffuse P transfer, with an approach combining analysis of multi-scale observation data and modelling.Analysis of a water chemistry time series acquired at the outlet of a small agricultural catchment revealed that particulate and dissolved P forms had different spatial origin within the landscape, and were transferred through distinct mechanisms. Particulate P originates from stream bed sediments, bank erosion and occasionally from erosion on hillslopes. Dissolved P originates from riparian soils; it is transferred via subsurface flow when the water table fluctuations create a hydrological connection with the stream.Multi-site monitoring of P concentration in the soil pore water of the riparian zone evidenced that groundwater fluctuations controlled not only P transfer, but also its solubilisation. Two critical moments were identified: the summer dry period is favourable for the build-up of a pool of mobile P forms in soils, which is transferred in the autumn; when groundwater stagnates in soil in anoxic conditions, reductive dissolution of iron oxides causes a second P release. A coupled hydrological-biogeochemical model confirmed the hypotheses regarding the role of groundwater fluctuation, the soil P content and variability in soil temperature and moisture. An assessment of the information content in the data and the propagation of uncertainty enab

Abstract This thesis examined hydrological processes such as snowmelt and groundwater discharge in drained peatland areas in the boreal zone. The studied processes were measured in situ using environmental tracers. Further, performance of a treatment wetland was studied during snowmelt and high flow. A GIS model was developed to estimate groundwater seepage areas in peatland systems surrounding eskers. It was found that soil frost had a clear impact on water quality during snowmelt. This was evident as lower suspended sediments, water colour and dissolved organic carbon concentrations, among other changes. The treatment wetland was found to reduce the suspended solids load during the snowmelt period and late autumn, while reductions in phosphorus and nitrogen loads occurred during summer. A sampling algorithm was built to test how different sampling frequencies affected the estimation of suspended solid loads from the constructed wetland. The results showed increasing uncertainty for sparser sampling (from weekly to monthly sampling), but the uncertainty remained high even at weekly sampling. The GIS model was tested on two eskers and shown to give a fair estimate of groundwater discharge locations. It can thus be used for improving aquifer protection in boreal eskers related to the drainage networks surrounding them. However, to be applied more widely, further efforts are required. The findings in this thesis could be used to develop better water management policies for peat extraction areas, or other industries operating in similar soils and climate. For example, meltwater could be allowed to temporarily bypass treatment facilities in areas with deep soil frost penetration. The wetland study showed that peatland-based wetlands are a suitable approach for improving water treatment performance even under variable hydraulic loads. The uncertainty in the estimated load from a small peat extraction catchment was high, which might limit the use of such data for some purposes. Load estimation methods using the concentration data collected during previous years might be able to reduce the uncertainty, but if the uncertainty needs to be lowered substantially use of sensor technology might be the only viable approach. / Tiivistelmä Tämä väitöskirja käsittelee lumensulannasta syntyvää valuntaa erilaisilla turvemailla ja pintavalutuskentän puhdistustehoa lumensulannan aikaan turvetuontantoalueella. Lisäksi työssä pohditaan miten erilainen näytteenottoohjelma vaikuttaa turvetuotantoalueilta arvioituun kiintoaine kuormitukseen ja kehitetään yleiseen paikkatietoaineistoon perustuva malli jolla on mahdollista ennustaa pohjaveden purkatumispaikkoja harjualueilla. Routaisella turvetuotantoalueelta kiintoaineen, värin ja liuenneen orgaanisen hiilen pitoisuudet olivat pieniä lumensulannan aikaan. Työssä seurattu pintavalutuskenttä vähensi kiintoainekuormitusta alapuoliseen vesistöön myös lumensulannan ja syksyn aikana. Ravinteiden osalta pintavalutuskentän toiminta oli parasta kesäaikaan, lumensulannan ja syksyn aikana havaittiin typen ja fosforin huuhtoutumista. Eri näytteenotto-ohjelmilla havaittiin olevan suuri vaikutus arvioituun kuormitukseen. Yleisesti voidaan sanoa epävarmuuden kasvavan kohti harvempaa näytteenotto väliä (viikoittainen-kuukausittainen), mutta, myös viikoittaisella näytteenotolla epävarmuus on huomattava. Kehitettyä paikka- tietomallia kokeiltiin kahdella harjulla jossa se pystyi antamaan suuntaa antavaa arvioita pohjaveden purkautumispaikoista. Työn tuloksia voidaan hyödyntää turvetuotannon tai muiden turvemailla tai niiden lähellä sijaitsevien teollisuuden vesistövaikutuksia arvioitaessa. Esimerkiksi routaisella turvemaalla voitaisiin harkita lumensulannasta aiheituvan valunnan ohijuoksutusta vesiensuojelurakenteista. Työssä todettiin myös pintavalutuskenttien toimivan vaihtelevan kuormituksen alaisena, sekä lumensulannan että syksyn aikaan. Arvioiduissa kuormituksissa erinäytteenottoväleillä havaitut suuret epävarmuudet saattavat rajoittaa laskelmien käyttöä joissakin tarkoituksissa. Epävarmuutta voidaan vähentää käyttämällä hyväksi edellisinä vuosina tehtyjä vedenlaatumittauksia. Luotettavin tapa epävarmuuden vähentämiseksi on jatkuvatoimisten vedenlaatumittareiden käyttäminen.

Biogas production from energy crops grown on arable land often competes with food and feed production. Wetland plants offer an alternative source of biomass as well as offering a number of environmental benefits such as nutrient removal from wastewaters, carbon sequestration and reducing the use of mineral fertilizer. The aim of this study is to investigate the effect of harvest time on biogas production of Phragmites australis and Glyceria maxima and to perform a cost-benefit analysis of using these wetland plants as a substrate for biogas production. The results of the batch experiment show that the overall biogas production and specific methane yields of biomass harvested in June was higher than biomass harvested in September due the increased lignocellulosic nature of the more mature September plant. The cost-benefit showed that in Sweden it is not currently profitable to solely use wetland plants for biogas production. For both species the highest costs were seen in the June harvested biomass, this was due to the much higher fresh weight and increased transportation costs. For both species the highest revenues generated were the June harvested biomass, this was due to the higher specific methane yields. It was found that the harvest time that was closest to profitability from both species was the June harvest for Phragmites australis. Although the costs were higher for harvesting in June, this was outweighed by the higher amount of electricity produced for this scenario. If transportation distance was to be increased it could result in September being the favourable harvest time. Therefore, individual circumstances of the farmers could decide which is the optimal harvest time. Although solely using wetland plants for biogas production is not currently profitable, co-digestion and pre-treatment are options to investigate that could change this. Also if a greater financial value is put on the socioeconomic benefits such as increased biodiversity, aesthetic value and global warming mitigation it may be financially viable in the future.

Low learner performance is one of the greatest challenges that confront South Africans in this post-apartheid era. Despite valiant efforts on the government’s part to improve the education system every year, successful learners are not coming through the ranks in sufficient numbers. In the case of Atteridgeville, an old township near the Pretoria Central Business District, the phenomenon of low learner performance is reflected in the quality of schoolyards and the behavior of learners. Schoolyards are degraded, learners lack confidence, they are not enthusiastic about their schools, they do not interact with the communities around their schools, and they do not venture into the physical landscape outside their schools. The question arises whether the landscape outside the classroom is not, in fact, contributing to the problem. If this is so then a way must be found to manipulate the landscape so that obstacles to learner performance are removed and learning is facilitated. This thesis explores the notion that the outdoor landscape in Atteridgeville can play a role in helping learners reach their potential. Therefore Atteridgeville will be the departure point for the investigation. The investigation will result in a project location which will be further investigated to identify its inherent opportunities and constraints. The design response to these opportunities and constraints, coupled with both theoretical and conceptual backing, will inform the project at master plan and detail design level. Methods must be found to unlock the didactic and experiential potential of the schoolyard and surrounding landscape in a township where open green spaces are under threat and physical and social obstacles to learner performance exist. / Dissertation ML(Prof)--University of Pretoria, 2014 / Architecture / ML(Prof) / Unrestricted