A unified hydrogeological conceptual model of the Milk River transboundary aquifer,traversing Alberta (Canada) and Montana (USA)

A conceptual model of the transboundary Milk River Aquifer (MRA), extending across the Canada–USA border, was developed based on literature, focused fieldwork and a three-dimensional geological model. The MRA corresponds to the Virgelle Member of the Milk River Formation (Eagle Formation in Montana, USA) and it is an important groundwater resource over a large area (25,000 km²). The Virgelle outcrops near the international border and along the Sweet Grass Arch in Montana. The down-gradient limit of the MRA is the unconformity separating the Virgelle from the gas-bearing sandy shale of the Alderson Member. The MRA is confined above by the Pakowki/Claggett Formations aquitards and below by the Colorado Group aquitard. The MRA contains higher transmissivity areas resulting in preferential flowpaths, confirmed by natural geochemical tracers. Tritium and ¹⁴C delineate restricted recharge areas along the outcrops on both sides of the international border. Drastic decreases in horizontal hydraulic gradients indicate that the Milk River intercepts a large proportion of groundwater flowing to the north from the recharge area. Downgradient of the Milk River, groundwater movement is slow, as shown by ³⁶Cl residence times exceeding 1 Ma. These slow velocities imply that groundwater discharge downgradient of the Milk River is via vertical leakage through the Colorado Group and upward along buried valleys, which act as drains and correspond to artesian areas. When confined, the MRA contains a fossil groundwater resource, not significantly renewed by modern recharge. Groundwater exploitation thus far exceeds recharge, a situation requiring properly managed MRA groundwater depletion.     

Geologic and hydrologic hazards in glacierized basins in North America resulting from 19th and 20th century global warming

Alpine glacier retreat resulting from global warming since the close of the Little Ice Age in the 19th and 20th centuries has increased the risk and incidence of some geologic and hydrologic hazards in mountainous alpine regions of North America. Abundant loose debris in recently deglaciated areas at the toe of alpine glaciers provides a ready source of sediment during rainstorms or outburst floods. This sediment can cause debris flows and sedimentation problems in downstream areas. Moraines built during the Little Ice Age can trap and store large volumes of water. These natural dams have no controlled outlets and can fail without warning. Many glacier-dammed lakes have grown in size, while ice dams have shrunk, resulting in greater risks of ice-dam failure. The retreat and thinning of glacier ice has left oversteepened, unstable valley walls and has led to increased incidence of rock and debris avalanches.     

Evolution of the Mount Woods Inlier, northern Gawler Craton, Southern Australia: an integrated structural and aeromagnetic analysis

Structural mapping integrated with interpretation and forward modelling of aeromagnetic data form complimentary and powerful tools for regional structural analysis because both techniques focus on architecture and overprinting relationships. This approach is used to constrain the geometry and evolution of the sparsely exposed Mount Woods Inlier in the northern Gawler Craton. The Mount Woods Inlier records a history of poly-phase deformation, high-temperature metamorphism, and syn- and post-orogenic magmatism between ca. 1736 and 1584 Ma. The earliest deformation involved isoclinal folding, and the development of bedding parallel and axial planar gneissic foliation (S₁). This was accompanied by high-temperature, upper amphibolite to granulite facies metamorphism at ca. 1736 Ma. During subsequent north–south shortening (D₂), open to isoclinal south–southeast-oriented F₂ folds developed as the Palaeoproterozoic successions of the inlier were thrust over the Archaean nuclei of the Gawler Craton. The syn-D₂ Engenina Adamellite was emplaced at ca. 1692 Ma. The post-D₂ history involved shear zone development and localised folding, exhumation of metamorphic rocks, and deposition of clastic sediments prior to the emplacement of the ca. 1584 Ma Granite Balta Suite. The Mount Woods Inlier is interpreted as the northern continuation of the Kimban Orogen.     

Kinetics of biodegradation of diesel fuel by enriched microbial consortia from polluted soils

Three microbial consortia were isolated from three polluted soils located at an oil refinery and acclimated to grow on diesel fuel as the sole carbon source. Batch experiments were then conducted with the three consortia to study the kinetics of diesel biodegradation. The effects of temperature (25, 30 and 35?°C) and diesel concentration (0.5, 1 and 3?%) on the biodegradation of diesel were analysed. Several species were identified in the acclimated microbial consortia, and some of them appeared in more than one consortium. Thermal inhibition was observed at 35?°C. In the rest of experiments, over 80?% of the substrate was degraded after 40?h of treatment. These results proved the good feasibility of using the polluted sites as sources of mixed consortia for hydrocarbon degradation. However, diesel degradation efficiencies and rates were very similar, suggesting that the acclimation process produced mixed consortia with very similar characteristics; in this context, origin of the soil sample was not a decisive factor. A simple Monod-type kinetic model was used to simulate the biodegradation process, and accurate results were obtained. The ?? _max values were between 0.17 and 0.34?h^?1. The results of this study revealed that the consortia can function at high concentrations of hydrocarbons without any sign of growth inhibition, which is important for the design of bioreactors for wastewater treatment with high concentrations of fuel.     

Through-Water Close Range Digital Photogrammetry in Flume and Field Environments

Measurement of the structure of gravel-bed river surfaces is crucial for understanding both bed roughness and the sediment entrainment process. This paper describes the use of close range digital photogrammetry to measure and monitor change occurring in submerged river gravel-beds in both flume and field environments. High-resolution digital elevation models (DEMs) were obtained and two-media (through air and water) techniques were used to correct for the e.ects of refraction at the air/water interface. Although suitable refractive models have been developed, the use of proprietary software to generate DEMs automatically introduces the problem of how to re-establish collinearity. A simple refraction correction algorithm based upon analytical geometry was developed and is described. This algorithm was designed for use after initial DEM acquisition and allows any photogrammetric software package to be used for data acquisition. Application of this algorithm led to improvements in DEM accuracy by reducing the systematic, depth-dependent bias caused by refraction
Research carried out in a flume environment allowed the algorithm to be tested by measuring a flooded and drained bed surface. Non-systematic differences between the "dry" and "wet" DEMs arose from reductions in stereomatching success in the two-media case. This effect was thought to be due to light attenuation and the introduction of residual parallax. Results suggest that close range digital photogrammetry can be used to extract high quality DEMs of submerged topography in both flume and field fluvial environments, which represents a particularly exciting development for fluvial geomorphologists     

Assessment of toxicological status of a SW Mediterranean segment population of striped dolphin (Stenella coeruleoalba) using skin biopsy

Various studies have revealed high concentrations of contaminants such as organochlorines (OCs) and heavy metals in Mediterranean cetaceans. A geographical trend of contamination (PCBs and DDTs) has been found for striped dolphin (Stenella coeruleoalba). In this study we used a non-lethal approach (skin biopsy) to investigate bioaccumulation of OCs, including polychlorobiphenyls (PCBs), DDTs, polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs), trace elements (Hg, Cd, Pb) and CYP1A activity (BPMO) in nine striped dolphins sampled in the Aeolian area (Sicily - Italy) in summer 2002. The arithmetic mean value of BPMO activity in this group was 43.46 AUF/g tissue/h. This value is approximately 3 times and 5 times lower, respectively, than the value found in the Ionian and in the Ligurian groups. Skin biopsies of striped dolphins emerged as a suitable material for assessing the toxicological status of the various Mediterranean groups.