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Arsenic contamination has been a growing concern for many countries, especially Bangladesh. In Bangladesh, one of the most arsenic-contaminated regions is Chandpur. In this study, groundwater data were analyzed in order to create models to improve knowledge on groundwater flow dynamic in a specific area of Chandpur called Matlab. Observation have shown that groundwater flows from north to southeast. The southeast part of Matlab is faced with excessive pumping for irrigation which could explain in part the flow direction. In this study, no predictive model was created due to a lack of data, but the key knowledge gaps are presented. Soil analysis, aquifers identification and study about the interaction between the Meghna river and the shallow aquifers are highlighted as the most crucial studies to decrease the knowledge gaps. Climate change will likely result in drier summer, an increase in rainfall during monsoon and an increase in extreme events. This will lead to more challenging living conditions for the rural population already facing many challenges. Therefore, further studies for knowledge acquisition need to be conducted, and new sustainable measures must be taken to prevent catastrophic outcomes. / Arsenikkontaminering har varit ett växande bekymmer för många länder, särskilt Bangladesh. En av de mest arsenikförorenade regionerna i Bangladesh är Chandpur. I denna studie analyserades grundvattendata för att skapa modeller för att förbättra kunskapen om grundvattenflödesdynamiken i Matlab-regionen i Chandpur-distriktet i sydöstra Bangladesh. Observationer har visat att grundvatten rinner från norr till sydost. Den sydöstra delen av Matlab står inför överdriven pumpning för bevattning som delvis skulle kunna förklara flödesriktningen. I denna studie skapades ingen förutspående modell på grund av brist på data, men de viktigaste kunskapsluckorna presenteras. Jordanalys, identifiering av vattendrag och studier om samspelet mellan Meghna-floden och de grunda vattendragen framhävs som de mest avgörande studierna för att minska kunskapsluckorna. Klimatförändringar kommer sannolikt att resultera i torrare somrar, en ökning av nederbörd under monsunen och en ökning av extrema händelser. Detta kommer att leda till mer utmanande levnadsvillkor för landsbygdsbefolkningen, som redan står inför många utmaningar. Därför behöver ytterligare studier för kunskapsinhämtning genomföras, och nya hållbara åtgärder måste vidtas för att förhindra katastrofala utfall.

Hyporheic exchange is an ecologically and biogeochemically essential function of rivers and streams. One important driver of hydrostatic (hyporheic) exchange is gra- dients in the hydrostatic hydraulic head at the streambed. This thesis investigates the impact of discharge on hydrostatic exchange in two stream reaches in Uppland, Sweden, with different geomorphological characteristics. By comparing 1D approx- imations of hydrostatic head variations along different longitudinal profiles across the streams, the use of a 2D hydraulic model for defining such variations is evaluated. Channel topography and discharge data have been obtained through field surveys in the two streams and form the basis for the setup of two HEC-RAS 2D models. The models have been calibrated against stream-depth measurements, validated against stream depth and stream velocity, and used for simulation of a range of discharges in both reaches. Water surface elevations, obtained for the different discharges in three profiles along each reach, have been used as input in a spectral model evaluating flow across streambed area; average hyporheic exchange velocity W. The results show that W , and thereby the hydrostatic exchange, decreases with increasing dis- charge and varies between different longitudinal profiles in the reach with the most complex geomorphology. For the reach with simpler geomorphology, the effects of discharge, as well as variations across the streams, are negligible. This implies that a 1D approximation of the hydrostatic head variations at the streambed can be sat- isfactory for a stream with simple geomorphology, whereas a 2D evaluation is more accurate for a stream with a complex geomorphology. / Denna uppsats handlar om hur ett vattendrags geomorfologi (form och geologi) och vattenföring påverkar hyporheiskt utbyte. Hyporheiskt utbyte är en process där ytvat- ten tränger igenom vattendragets botten, flödar i den så kallade hyporheiska zonen och blandas med grundvatten för att sedan återvända till vattendraget. Det är en vik- tig funktion på grund av dess påverkan på ekologi och biogeokemiska reaktioner, exempelvis genom syresättning av botten. Hyporheiskt utbyte påverkas bland annat av variationer i vattnets energinivå (hydrau- lisk tryckhöjd) vid bottnen. Den hydrauliska tryckhöjden varierar med vattenytans höjd, som är summan av bottnens topografi och vattnets djup. Målet med studien var att undersöka vattenföringens påverkan på hydrostatiskt, hyporheiskt utbyte i två vattendrag med olika geomorfologiska egenskaper. Endimensionella (1D) approx- imationer av hydraulisk tryckhöjd används ibland vid modellering av hyporheiskt utbyte. Därför var ytterligare ett mål att utvärdera flera endimensionella (1D) ap- proximationer av hydraulisk tryckhöjd vid botten, för att på så sätt undersöka om tvådimensionell (2D) modellering tillför mer information. För att uppnå målen genomfördes fältstudier vid två vattendrag i Uppland, vid vilka topografimätningar och spårämnesförsök gjordes. Dessa lade grunden för uppbygg- nad av 2D-modeller över vattendragen i modelleringsverktyget HEC-RAS. Model- lerna kalibrerades mot uppmätta djupdata och användes sedan för simulering av ett antal olika vattenföringar. Longitudinella profiler placerades i mitten samt till vänster respektive höger om mitten i vattendragen. Längs dessa profiler, för de olika vatten- föringarna, erhölls vattenytans höjd, som blev indata till en spektral modell. Utifrån topografi och vattenytans höjd längs en profil beskriver den spektrala modellen hur den hydrauliska trycknivån varierar med hjälp av en Fourier-serie. Den spektrala modellen beräknar det hyporheiska utbytets medelhastighet W , vil- ken är ett mått på hur stor volym vatten som genomtränger bottenarea per tid. Re- sultaten visar att för vattendraget med mest komplex geomorfologi minskar W med ökande vattenföring, och W varierar också mellan de olika longitudinella profilerna. För det andra vattendraget, som har en enklare geomorfologi, syns inga betydande skillnader, varken mellan olika vattenföringar eller profiler. Därutöver är W mind- re för vattendraget med enklare geomorfologi jämfört med vattendraget med kom- plex geomorfologi. Resultaten antyder därmed att 1D-approximationer av hydraulisk tryckhöjd vid bottnen är tillräckliga för vattendrag med enkel geomorfologi, medan 2D-modellering tillför information för ett vattendrag med komplex geomorfologi.

<p>Digital elevation models (DEM) can be used for a multitude of applications. Under ideal circumstances, calibration of a remotely acquired estimate of topographic elevation is calibrated through use of ground control points (GCP) which would be ubiquitous, seamlessly joining remotely sensed data and high accuracy check points. In reality there are many areas on the earth’s surface which are difficult, expensive, or dangerous to access. Under these circumstances, the acquisition of GCPs may not be realistic and relative DEMs must be used. Innovative methods must then be used to determine the relative error associated with a DEM in a given study area. The method presented in this paper compares three DEMs (ASTER, CDED, SRTM) derived from independent acquisition systems to determine their relative errors.</p> <p>The ASTER DEM data was chosen for a lineament analysis study in north central Ontario, Canada. This study used a quantitative digital approach to determine the density of lineaments mimicking the geometry of the northern Sudbury Igneous Complex contact (SIC). The study revealed a lineament density at ~25km north of the northern SIC contact, suggesting a ring structure from an ancient multi-ring impact basin. This argument is supported by findings of the pattern of plagioclase clouding intensities in Matachewan dykes in the vicinity of the ring structure. The orientation of the dykes may have some connection to the faulting and block rotation caused by crater wall collapse.</p> <p>Paleomagnetic data from the norite in the SIC and Foy Offset dyke combined with an unconstrained magnetic inversion of the Foy Offset dyke suggest that the Sudbury Structure has not been folded, but instead has been deformed by brittle deformation.</p> / Master of Science (MSc)

Island biogeography theory predicts that the patterns and distributions of spatially isolated populations are governed by large scale processes. The high elevations forests in the Southern Appalachians represent a series of naturally fragmented islands that harbor many isolated populations of species at the southern limits of their range. Understanding the governing forces of population dynamics in this region will enhance the probability of species persistence in the face of threats such as global warming and human development. We surveyed bird populations across multiple elevations in Virginia and combined this with a multi-scale habitat analysis to determine influences of species presence and species richness. We detected 101 species across the elevation gradient, including 12 species with special conservation status and ten species whose presence increased with increasing elevation. These ten elevation sensitive species responded to habitat variables at both the microhabitat and landscape scale, with species-specific patterns of habitat variable correlation emerging. Habitat type was least effective in predicting species presence for any elevation sensitive species. Species richness declined over the elevation gradient until the highest elevations, where this trend reversed and richness began to increase. This pattern was driven by an increase in short-distance migrants beginning at mid-elevations, which ultimately overpowered a corresponding decrease in long-distance migrants beginning at similar elevations. Habitat analysis linked these patterns to a preference of short-distance migrants for smaller, more isolated non-forested patches, and a historical lack of persistence for long-distance migrants. Conservation and management decisions for the region should focus on a multi-scale approach that preserves all habitat types for continued species presence and high species richness, although the persistence of particular elevation sensitive species is compounded by unique species-habitat relationships and the perception of islands as species-specific. Continued monitoring of these fragmented populations in light of both short- and long-term threats which span multiple scales of influence will maintain high species richness and ensure the persistence of crucial breeding habitat. / Master of Science

The objective of the present study was to acquire a better understanding of parameters controlling the species generation and transport from compartment fires. The experiments were performed in a half-scale ISO 9705 compartment and a 6.1 m long hallway connected in a head-on configuration. The buoyancy driven propane fire was provided by a burner and a continuous gaseous fuel supply system. All the measurements were obtained during the steady state of the fire. The ventilation conditions were fixed and three different fire source elevations were studied for heat release rates ranging from 20 kW to 150kW. The species yields were obtained from performing detailed mapping measurements at the compartment and hallway exit planes. The measurements included local specie mole fractions of oxygen, carbon dioxide, carbon monoxide and unburned hydrocarbons. The local temperature and the local pressure (for local gas velocity calculations) were also measured. In addition, visual observations of the flow dynamic were performed through a window and the vents to give useful insights and lead to a better understanding of the combustion process. The data obtained from the species generation study was analyzed using previously developed methods. The method based on equivalence ratio was presented and determined inappropriate for the present study where the global equivalence ratio was not equal to the plume equivalence ratio due to the complexity of the fire dynamic taking place. The method consisting of correlating the species yields based on the combustion within the compartment as a function of a non dimensional heat release rate allowed qualitative conclusions to be made. The non-dimensional heat release rate was based on the fuel load and the geometric parameters of the compartment. This methodology revealed similarities in the species production between the three fire source elevations investigated. A correlation of the data was obtained based on experimental data. The transport of species to remote locations was studied for the three fire source elevations and fixed ventilation conditions. Species mole fractions and yields were obtained at the compartment exit plane (compartment/hallway interface) and at the hallway exit plane. The results were compared for various heat release rates and showed differences for some scenarios attributed to mixing along the hallway and oxidation reactions outside the compartment. / Master of Science

No / Modelling played an important role in simulation, optimisation, and control of multi-stage flash (MSF) desalination processes. Top brine temperature (TBT) is one of the many important parameters that affect optimal design and operation of MSF processes. Within the MSF process model, calculation of TBT is therefore important. For a given pressure, TBT is a function of boiling point temperature (BPT) at zero salinity and temperature elevation (TE) due to salinity. In this work, we develop several neural network (NN) based correlations for predicting TE. It is found that the NN based correlations can predict the experimental TE very closely. Also predictions by the NN based correlations were good when TE values, obtained using existing correlations from the literature are compared. Due to advancement of the microcomputer, plant automation becomes reliable means of plant maintenance. NN based correlations (models) can be updated in terms of new sets of weights and biases for the same architecture or for a new architecture reliably with new plant data.

Yes / The water permeability constant, (Kw) is one of many important parameters that affect optimal design and operation of RO processes. In model based studies, e.g.within the RO process model, estimation of Kw is therefore important. There are only two available literature correlations for calculating the dynamic Kw values. However, each of them are only applicable for a given membrane type, given feed salinity over a certain operating pressure range. In this work, we develop a time dependent neural network (NN) based correlation to predict Kw in RO desalination processes under fouling conditions. It is found that the NN based correlation can predict the Kw values very closely to those obtained by the existing correlations for the same membrane type, operating pressure range and feed salinity. However, the novel feature of this correlation is that it is able to predict Kw values for any of the two membrane types and for any operating pressure and any feed salinity within a wide range. In addition, for the first time the effect of feed salinity on Kw values at low pressure operation is reported. While developing the correlation, the effect of numbers of hidden layers and neurons in each layer and the transfer functions is also investigated.