Polythermal glaciers, i.e. glaciers with a combination of ice at and below the freezing point, are widespread in arctic and subarctic environments. The polythermal structure has major implications for glacier hydrology, ice flow and glacial erosion. However, the interplay of factors governing its spatial and temporal variations such as net mass balance, ice advection and water content in the ice is poorly investigated and as yet not fully understood. This study deals with a thorough investigation of the polythermal regime on Storglaciären, northern Sweden, a small valley glacier with a cold surface layer in the ablation area. Extensive field work was performed including mapping of the cold surface layer using ground-penetrating radar, ice temperature measurements, mass balance and ice velocity measurements. Analyses of these data combined with numerical modelling were used specifically to investigate the spatial and temporal variability of the cold surface layer, the spatial distribution of the water content just below the cold surface layer transition, the effect of radar frequency on the detection of the surface layer, and the sensitivity of the cold surface layer to changes in forcing. A comparison between direct temperature measurements in boreholes and ground-penetrating surveys shows that the radar-inferred cold-temperate transition depth is within ±1 m from the melting point of ice at frequencies above ~300 MHz. At frequencies below ~155 MHz, the accuracy degrades because of reduced scattering efficiency that occurs when the scatterers become much smaller compared to the wavelength. The mapped spatial pattern of the englacial cold-temperate transition boundary is complex. This pattern reflects the observed spatial variation in net loss of ice at the surface by ablation and vertical advection of ice, which is suggested to provide the predominant forcing of the cold surface layer thickness pattern. This is further supported by thermomechanical modeling of the cold surface layer, which indicates high sensitivity of the cold surface layer thickness to changes in vertical advection rates. The water content is the least investigated quantity that is relevant for the thermal regime of glaciers, but also the most difficult to assess. Spatial variability of absolute water content in the temperate ice immediately below the cold surface layer on Storglaciären was determined by combining relative estimates of water content from ground-penetrating radar data with absolute determination from temperature measurements and the thermal boundary condition at the freezing front. These measurements indicate large-scale spatial variability in the water content, which seems to arise from variations in entrapment of water at the firn-ice transition. However, this variability cannot alone explain the spatial pattern in the thermal regime on Storglaciären. Repeated surveys of the cold surface layer show a 22% average thinning of the cold surface layer on Storglaciären between 1989 and 2001. Transient thermomechanical modeling results suggest that the cold surface layer adapts to new equilibrium conditions in only a few decades after a perturbation in the forcing is introduced. An increased winter air temperature since mid-1980s seems to be the cause of the observed thinning of the cold surface layer. Over the last decades, mass balance measurements indicate that the glacier has been close to a steady state. The quasi-steady state situation is also reflected in the vertical advection, which shows no significant changes during the last decades. Increased winter temperatures at the ice surface would result in a slow-down of the formation of cold ice at the base of the cold surface layer and lead to a larger imbalance between net loss of ice at the surface and freezing of temperate ice at the cold-temperate transition.

Summer blooms of filamentous, diazotrophic cyanobacteria are typical of the Baltic Sea Proper, and are dominated by Aphanizomenon sp. and the toxic Nodularia spumigena. Although occurring every summer, the blooms vary greatly in timing and spatial distribution, making monitoring difficult and imprecise. This thesis studies how the spatial variability of Baltic cyanobacterial blooms influences estimates of abundance, vertical and horizontal distribution and N2-fixation. Implications for sampling and monitoring of cyanobacterial blooms are also discussed. The results of the thesis confirm the importance of diazotrophic cyanobacteria in providing N for summer production in the Baltic Proper. It also highlights the large spatial and temporal variation in these blooms and argues that improved spatial coverage and replication could make monitoring data more useful for demonstrating time trends, and for identifying the factors regulating the blooms. The vertical distribution of Aphanizomenon and Nodularia was found to be spatially variable, probably as a combination of species-specific adaptations and ambient weather conditions. Vertical migration in Aphanizomenon was more important towards the end of summer, and is probably regulated by a trade-off between P-availability and light and temperature.

The high incidence of pathogens is one of the main causes for impaired surface water quality designations in the United States. Pathogen presence in fresh water is monitored through the detection of indicator bacteria. Indicator bacteria concentrations, spatial and temporal variability, and microbial risks were evaluated in two rural watersheds, the Bosque and Leon Rivers, and one predominantly urban watershed, the San Jacinto River, all in Texas. Human health risk was predicted from contaminated waters as indicated by ingestion of Escherichia coli found in surface water for contact recreation scenarios. The watersheds were chosen because many segments were previously placed on the 303 (d) list (published by the TCEQ) for failing the indicator bacteria standards. Predominantly urban areas of the San Jacinto River and rural portions of the Bosque and Leon Rivers, where Concentrated Animal Feeding Operations (CAFOs) are numerous, were compared to relatively pristine rural watersheds. Spatial analysis of the watersheds with E.coli concentrations exceeding the single sample (394 MPN/100mL) and the geometric mean standards (126 MPN/100mL) indicated that land use is a significant factor influencing the incidence of bacterial concentrations. Non-agricultural rural areas of the watersheds, such as forests and rangelands, had significantly lower E.coli concentrations compared to the agricultural areas and urban land uses. Human health risk due to ingestion of E.coli as an indicator organism indicated a similar pattern to that of their concentrations in that urban and agricultural areas had a greater risk compared to the other rural areas of the watersheds. The risk estimate for urban and agricultural areas exceeded the acceptable limit of one in ten thousand (10^-4), indicating a potential for adverse health effects to humans. Temporal variability in the watersheds as a function of streamflow, rainfall, and temperature indicated a positive correlation between bacterial concentration and high streamflow, rainfall and temperature. The positive correlation for these effects was greater in the rural areas compared to urban areas, indicating the presence of multiple factors responsible for E.coli concentrations in urban areas. Thus, land use was confirmed to be a major factor contributing to the presence of indicator bacteria in surface waters.

The intensification of land-water management due to agriculture, forestry, and urbanization is a global phenomenon increasing the pressure on worlds water resources and threatening water security in North America. The Prairie Pothole Region of North America covers approximately 775,000 km2 and contains millions of wetlands that serve important hydrological and ecological functions. The unique hummocky topography and the variable effect of different processes contribute to high spatio-temporal variability in soil water, posing major challenges in hydrological studies. The objectives of this study were to a) examine the spatial pattern of soil water storage and its scale and location characteristics; and b) to identify its controls at multiple scales. Soil water content at 20 cm intervals down to 140 cm was measured along a transect extending over several knolldepression cycles in a hummocky landscape. High water storage in depressions and low water storage on the knolls created a spatial pattern that was inversely related to elevation. Spatial patterns were strongly similar within any given season (intra-season rank correlation coefficient as high as 0.99), moreso than between the same season over different years (inter-annual rank correlation coefficient as high as 0.97). Less similar spatial patterns were observed between different seasons (inter-season rank correlation coefficients as high as 0.90). While the intra-season and inter-annual spatial patterns were similar at scales >18 m, the inter-season spatial patterns were similar at much large scales (>72 m). This may be due to the variations in landform elements and micro-topography. The similarity at scales >72 m were present at any time and depth. However, small- and medium-scale spatial patterns changed with depth and with season due to a change in the hydrological processes. The relative dominance of a given set of processes operating both within a season and for the same season over different years yielded strong intra-season and inter-annual similarity at scales >18 m. Moreover, similarity was stronger with increasing depth, and was thought to be due to the dampening effect of overlying soil layers that are more dynamic. Similarity of spatial patterns over time helps to identify the location that best represents the field averaged soil water and improves sampling efficiency. Change in the similarity of scales of spatial pattern helps identify the change in sampling domain as controlled by hydrological processes. The scale information can be used to improve prediction for use in environmental management and modeling of different surface and subsurface hydrological processes. The similarity of spatial pattern between the surface and subsurface layers help make inferences on deep layer hydrological processes as well as groundwater dynamics from surface water measurements.

The intensification of land-water management due to agriculture, forestry, and urbanization is a global phenomenon increasing the pressure on worlds water resources and threatening water security in North America. The Prairie Pothole Region of North America covers approximately 775,000 km2 and contains millions of wetlands that serve important hydrological and ecological functions. The unique hummocky topography and the variable effect of different processes contribute to high spatio-temporal variability in soil water, posing major challenges in hydrological studies. The objectives of this study were to a) examine the spatial pattern of soil water storage and its scale and location characteristics; and b) to identify its controls at multiple scales. Soil water content at 20 cm intervals down to 140 cm was measured along a transect extending over several knolldepression cycles in a hummocky landscape. High water storage in depressions and low water storage on the knolls created a spatial pattern that was inversely related to elevation. Spatial patterns were strongly similar within any given season (intra-season rank correlation coefficient as high as 0.99), moreso than between the same season over different years (inter-annual rank correlation coefficient as high as 0.97). Less similar spatial patterns were observed between different seasons (inter-season rank correlation coefficients as high as 0.90). While the intra-season and inter-annual spatial patterns were similar at scales >18 m, the inter-season spatial patterns were similar at much large scales (>72 m). This may be due to the variations in landform elements and micro-topography. The similarity at scales >72 m were present at any time and depth. However, small- and medium-scale spatial patterns changed with depth and with season due to a change in the hydrological processes. The relative dominance of a given set of processes operating both within a season and for the same season over different years yielded strong intra-season and inter-annual similarity at scales >18 m. Moreover, similarity was stronger with increasing depth, and was thought to be due to the dampening effect of overlying soil layers that are more dynamic. Similarity of spatial patterns over time helps to identify the location that best represents the field averaged soil water and improves sampling efficiency. Change in the similarity of scales of spatial pattern helps identify the change in sampling domain as controlled by hydrological processes. The scale information can be used to improve prediction for use in environmental management and modeling of different surface and subsurface hydrological processes. The similarity of spatial pattern between the surface and subsurface layers help make inferences on deep layer hydrological processes as well as groundwater dynamics from surface water measurements.

Geotechnical engineers often face important discrepancies between the observed and the predicted behavior of geosystems. Two conceptual frameworks are hypothesized as possible causes: the ubiquitous spatial variability in soil properties and process-dependent terminal densities inherent to granular materials. The effects of spatial variability are explored within conduction and diffusion processes. Mixtures, layered systems, inclusions and random fields are considered, using numerical, experimental and analytical methods. Results include effective medium parameters and convenient design and analysis tools for various common engineering cases. In addition, the implications of spatial variability on inverse problems in diffusion are numerically explored for the common case of layered media. The second hypothesis states that there exists a unique terminal density for every granular material and every process. Common geotechnical properties are readily cast in this framework, and new experimental data are presented to further explore its implications. Finally, an unprecedented field study of blast densification is documented. It involves comprehensive laboratory and site characterization programs and an extensive field monitoring component. This full scale test lasts one year and includes four blasting events.

Benthic microalgal community composition on an ephemerally submerged sandflat at East Beach, Galveston Island, Texas was studied to determine the spatial and temporal variability of total biomass and community composition and its responses to experimental manipulations of two environmental factors (salinity and nutrients). Four field studies were conducted between August 2004 and February 2005. The community consisted of two major algal groups, diatoms, and cyanobacteria with two less abundant groups, green algae, and phototrophic bacteria. Spatial variability showed that patch sizes of 12 - 25 m were detected over larger scales with smaller scale (cm) patches of approximately 28 - 201 cm^-2 contained within the larger patches. The second study examined the spatio-temporal variability of BMA over a 21-month period in a 1,000 m^2 area. Sampling location and date explained a significant amount of the variability in the abundances of algal groups, which were positively correlated with the water content of the sediments and negatively correlated with temperature (sediment and water). All of the algal groups showed a seasonal pattern with higher abundances measured in the winter months and lower abundances found during the summer. BMA biomass (100 mg Chl a m^-2 or greater) maxima occurred at temperatures less than 22 degrees C and sediment water content greater than 15% (g water g sediment^-1). BMA response to different salinities and nutrient (N+P) amended sediments was assessed in four bioassays conducted over a 6-month period (Aug. 2004, Oct. 2004, Dec. 2004, and Feb. 2005). In the salinity study, the treatments that were either 100% or partially diluted with deionized water had the lowest BMA biomass over all. Chlorophyll a and fucoxanthin were significantly affected by salinity with higher abundances found in salinities that averaged 15 with a preference for salinities greater than 22. Chlorophyll b was affected by salinity with higher abundances measured in the treatments with lowest salinity (DL and DI); and was affected by the time of year. This would suggest that this algal group prefers an environment with salinity less than 2 but can easily adapt to environments with higher salinities. BMA abundances were not significantly affected by the nutrient amended sediment, but were significantly affected by stations with higher water content, and during the cooler months (Dec. 2004 and Feb. 2005).

Deep foundations, such as piles and suction caissons, are used throughout an offshore oil and gas production facility in deepwater. Ideally, the values of geotechnical properties for foundation design are determined by results from geotechnical investigation programs performed at the site of the foundation. However, the locations for facilities are not known exactly when soil borings are drilled and the footprint of a facility in deepwater can be very large with numerous foundation elements spread out over miles. Therefore, it is not generally feasible to perform a site-specific investigation for every foundation element. The objective of this research is to assess, analyze and model spatial variability in geotechnical properties for offshore foundations. A total of 97 geotechnical investigations from 14 offshore project sites covering the past twenty years of deepwater development in the Gulf of Mexico are compiled into a database. The geologic setting is primarily a normally to slightly overconsolidated marine clay, and the property of interest for the design of deep foundations is the undrained shear strength. The magnitude and characteristics of variability in design undrained shear strengths are analyzed quantitatively and graphically. Geostatistical models that describe spatial variability in the design shear strength properties to the distance away from the available information are developed and calibrated with available information from the database. Finally, a methodology is presented for incorporating the models into a reliability-based design framework to account for spatial variability in foundation capacity. Design examples are presented to demonstrate the use of the reliability methodology. Based on the design undrained shear strength profiles for the past 20 years in this Gulf of Mexico deepwater area, the design undrained shear strength varies spatially but does not depend on the time or method for site investigations. There are nonlinear spatial relationships in the point shear strength laterally and vertically due to stratigraphy such that depth-averaged shear strengths are correlated over further distances than point shear strengths. The depositional forces are an important factor causing spatial variations in the undrained shear strength, with greater variation and less spatial correlation in the more recent hemipelagic deposits (about upper 60 feet) than the deeper turbidite deposits and along the shelf versus off the shelf. The increased conservatism required in deep foundation design due to spatial variability when site specific strength data are not available is generally small with less than a five percent increase required in design capacity in this geologic setting. / text

Soil cover systems are an integral part of a mine reclamation program and are increasing in area. Knowledge of temperatures and thermal properties in the cover system provide important information regarding the energy balance, thermal regime, as well as preliminary insight into soil water content. Cover system temperatures and thermal properties are measured at a small number of vertically intensive profiles. Current methods do not provide any information as to the spatial variation of temperatures and thermal properties at scales other than the point scale. The objective of this study was to investigate the spatial scaling of thermal properties in reclamation cover systems. A distributed temperature sensing (DTS) system was installed in three cover systems of various textures and configurations. Semivariogram analysis demonstrated that on a 40 m slope consisting of mineral soil over sand (Site #1) soil temperatures did not exhibit any spatial structure, due to the presence of vegetation. A 100 m cover system comprised of a structureless sand (Site #2) was confirmed to be spatially uniform through semivariogram analysis. Semivariograms at Site #2 displayed secondary structure that corresponded to the 65 m plateau and 35 m slope. Site #3 consisted of a uniform peat and a 2% slope. Spatial structure was non-existent at Site #3 and was attributed to the unique thermal properties of peat that magnified the effect of microtopography on the surface energy balance. A method to estimate apparent thermal inertia (ATI) using DTS measurements at the soil surface was developed. Apparent thermal inertia was found to be less uncertain than the current standard apparent thermal diffusivity. The ATI method was determined to be the preferred method as it was related to soil water content and not prone to estimation errors due to imprecise depth measurement. The spatial scaling properties of a 236 m cover system (Site #3) were investigated using estimations of ATI. Measurements were taken every meter along the transect for bulk density, elevation, air-dried thermal conductivity and air-dried volumetric heat capacity. The dominant scale of variation in ATI was not related to physical or thermal properties, which tended towards the 3 m scale (bulk density and thermal conductivity) or the 108 m and field scale trend (elevation and volumetric heat capacity). The dominant scale of variation in ATI shifted between 30 m and the field scale trend and was related to water content as represented by the soil matric potential. A dry cover system tended to homogenize thermal property distribution, leading to a dominance of the 108 m and field scale trend. Wetter days led to a shift to the 30 m scale, with intermediate days showing a mix in scale dominance. Information on thermal property spatial scaling properties of cover systems can be used to optimally design monitoring systems that measure at the same scale as that which the cover is performing. Characterizing the spatial variability of the system will lead to better cover system designs and ultimately a more sustainable system.

Resumo: Os atributos mineralógicos e físicos possuem dependência espacial e a distribuição espacial destes atributos possui relação com as formas do relevo. O objeto deste trabalho foi avaliar os atributos mineralógicos da fração argila e os atributos físicos de um argissolo em curvaturas do relevo, assim como avaliar a correlação entre esses atributos. Uma malha de dimensão 100 x 100 m foi delimitada em uma área caracterizada pela forma convexa e outra pela fôrma côncava. As malhas possuem espaçamento regular de 10 x 10 m e os pontos de cruzamento deste espaçamento determinaram os pontos de coleta das amostras, num total de 121 pontos amostrais georreferenciados em cada malha. Os atributos físicos foram avaliados nas profundidades 0,0- 0,2 e 0,2-0,4 m e os atributos mineralógicos na profundidade 0,0- 0,2 m. Os atributos físicos analisados foram diâmetro médio ponderado, diâmetro médio geométrico, agregados maiores que 2 mm, agregados entre 2 e 1 mm , agregados menores que 1 mm, microporos, macroporos, volume total de poros, densidade do solo, resistência do solo à penetração e teor de água no solo, já os atributos mineralógicos da fração argila foram largura a meia altura, diâmetro médio do cristal dos óxidos de ferro, da caulinita e gibbsita, substituição isomórfica e área de superfície específica da hematita e goethita. Os teores da goethita e hematita e razão goethita/(goethita+hematita) e razão caulinita/(caulinita+gibbsita) também foram calculados. Os dados foram submetidos às análises estatísticas e geoestatísticas para avaliação da variabilidade espacial e influência das curvaturas nestes atributos. Para avaliação da relação entre os atributos da mineralogia e físicos realizaram-se as análises de correlação simples e espacial. Os atributos físicos e mineralógicos apresentaram-se dependentes das curvaturas do relevo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The mineralogicals and physical attributes have spatial dependence and the distribution of these attributes has relation with the forms of relief. The object of this study was to evaluate the attributes of clay mineralogy and the physical attributes of an argissol in curvatures of relief, as well as assess the correlation between these attributes. A grid size of 100 x 100 meters was defined in an area characterized by the convex shape and another in an area characterized by the concave shape. The grids have regular spacing of 10 x 10 m and the spacing of the points of intersection determine the points of collection of samples, a total of 121 georeferenced sample points in each grid. The physical attributes were evaluated in depth from 0.0 - 0.2 and 0.2 -0.4 m and the mineralogical attributes in depth 0,00-0,20 m. The physical attributes were analyzed: mean weight diameter, mean geometric diameter, aggregates larger than 2 mm, aggregates between 2 and 1 mm, aggregates smaller than 1 mm, microporosity, macroporosity, total porosity, bulk density, penetration resistance and water content in soil. The attributes of minerals were: width at half height, average diameter of crystals of iron oxides and kaolinite and gibbsite and isomorphic substitution and specific surface area of hematite and goethite. The contents of goethite and hematite and ratio goethite / (goethite + hematite) [Gt / (Gt + Hm)] and ratio kaolinite / (kaolinite + gibbsite) [Ct / (Ct + Gb)] were also calculated. Data were subjected to statistical and geostatistical analysis to evaluate the spatial variability and influence of these curvatures on these attributes. To assess the relation between mineralogy and physical attributes simple and spation correlation analysis where made. The physical and mineralogical attributes and depend on the curvature of the relief. There was also the influence of crystallinity of goethite and gibbsite in soil physical. / Orientador: José Marques Júnior / Coorientador: Gener Tadeu Pereira / Banca: Marcílio Vieira Martins Filho / Banca: Zigomar Menezes de Souza / Mestre