Interaction between the north-eastern boundary of Sgr A East and giant molecular clouds

We have detected the   v = 1 → 0 S(1) (λ= 2.1218 μm)  and   v = 2 → 1 S(1) (λ= 2.2477 μm)  lines of H₂ in the Galactic Centre, in a  90 × 27 arcsec²  region between the north-eastern boundary of the non-thermal source Sgr A East, and the giant molecular cloud (GMC)  M−0.02 − 0.07  . The detected  H₂ v = 1 → 0  S(1) emission has an intensity of  1.6–21 × 10⁻¹⁸ W m⁻² arcsec⁻²  and is present over most of the region. Along with the high intensity, the large linewidths  (FWHM = 40–70 km s⁻¹)  and the  H₂ v = 2 → 1 S(1)  to   v = 1 → 0 S(1)  line ratios (0.3–0.5) can be best explained by a combination of C-type shocks and fluorescence. The detection of shocked H₂ is clear evidence that Sgr A East is driving material into the surrounding adjacent cool molecular gas. The H₂ emission lines have two velocity components at ∼+50 and  ∼0 km s⁻¹  , which are also present in the NH₃(3, 3) emission mapped by McGary, Coil & Ho. This two-velocity structure can be explained if Sgr A East is driving C-type shocks into both the  GMC M−0.02 − 0.07  and the northern ridge of McGary et al.     

A systematic regional approach for climate change adaptation to protect biodiversity

Developing appropriate climate change adaptations to protect biodiversity requires taking into account the dynamics of agro-ecological and socio-economic change. A framework for approaching this problem was proposed, but not applied in detail, as part of a major biodiversity and climate change report prepared in Australia. This paper describes the first trial application of the method. It was applied across Vietnam as the Government is interested in identifying adaptation options and detailed data are readily available for its 65 provinces. The process involves identifying ecoregions and collating information for each region based on the current conditions and trends in biodiversity, population, income and agricultural production. Climate change scenarios are identified for each region, together with governance options. Educational needs and key adaptation actions are then identified for each region taking into account the agro-ecological and socio-economic input data. It is concluded that the framework could easily be applied in other countries and should assist the development of strategic adaptation options.     

The role of in situ stress in determining hydraulic connectivity in a fractured rock aquifer (Australia)

Fracture network connectivity is a spatially variable property that is difficult to quantify from standard hydrogeological datasets. This critical property is related to the distributions of fracture density, orientation, dimensions, intersections, apertures and roughness. These features that determine the inherent connectivity of a fracture network can be modified by secondary processes including weathering, uplift and unloading and other mechanisms that lead to fracture deformation in response to in situ stress. This study focussed on a fractured rock aquifer in the Clare Valley, South Australia, and found that fracture network connectivity could be discriminated from several geological, geophysical and hydrogeological field datasets at various scales including single well and local- to regional-scale data. Representative hydromechanical models of the field site were not only consistent with field observations but also highlighted the strong influence of in situ stress in determining the distribution of fracture hydraulic apertures and the formation of hydraulic chokes that impede fluid flow. The results of this multi-disciplinary investigation support the notion that the hydraulic conductivity of a fracture network is limited to the least hydraulically conductive interconnected fractures, which imposes a physical limit on the bulk hydraulic conductivity of a fractured rock aquifer.     

Geochemical heterogeneity in a small, stratigraphically complex moraine aquifer system (Ontario, Canada): interpretation of flow and recharge using multiple geochemical parameters

The Waterloo Moraine is a stratigraphically complex system and is the major water supply to the cities of Kitchener and Waterloo in Ontario, Canada. Despite over 30?years of investigation, no attempt has been made to unify existing geochemical data into a single database. A composite view of the moraine geochemistry has been created using the available geochemical information, and a framework created for geochemical data synthesis of other similar flow systems. Regionally, fluid chemistry is highly heterogeneous, with large variations in both water type and total dissolved solids content. Locally, upper aquifer units are affected by nitrate and chloride from fertilizer and road salt. Typical upper-aquifer fluid chemistry is dominated by calcium, magnesium, and bicarbonate, a result of calcite and dolomite dissolution. Evidence also suggests that ion exchange and diffusion from tills and bedrock units accounts for some elevated sodium concentrations. Locally, hydraulic “windows??cross connect upper and lower aquifer units, which are typically separated by a clay till. Lower aquifer units are also affected by dedolomitization, mixing with bedrock water, and locally, upward diffusion of solutes from the bedrock aquifers. A map of areas where aquifer units are geochemically similar was constructed to highlight areas with potential hydraulic windows.     

Contrasting sedimentation rates in Lake Illawarra and St Georges Basin,two large barrier estuaries on the southeast coast of Australia

Sedimentation rates over the last 100 years within two lagoons on the southeast coast of Australia, Lake Illawarra and St Georges Basin, have been quantified to determine the effects of catchment land use change and native vegetation clearance on infill rates, and spatial variations in the rate at which the estuaries have filled. Both catchments have similar lake and catchment area but have experience different degrees of modification due to land clearing for agriculture practices, urbanisation and industrialisation. Results indicate that in the heavily modified catchment of Lake Illawarra sedimentation rates close to fluvial deltas can be in excess of 16 mm/year, and between 2 and 4 mm/year in the adjacent central basin. This is approximately an order of magnitude greater than the pre-European rates. In contrast, at St Georges Basin, where the catchment has experienced much less modification, sedimentation rates in the central basin appear to have remained close to those prior to European settlement. However, sedimentation rates in the urbanized margin of St Georges Basin are relatively high (up to 4.4 mm/year). This rapid modern sedimentation in the margin of the estuarine embayments has been detected in several other estuaries in the region. However the degree of sedimentation within the bay-head deltas, and more significantly in the central basin appears proportional to the degree clearance of native vegetation (forest) in the catchment, urban expansion and development of heavy industry in the respective catchment areas.     

Formation of uranium‐thorium‐rich bitumen nodules in the Lockne impact structure,Sweden: A mechanism for carbon concentration at impact sites

Abstract— The Ordovician Lockne impact structure is located in central Sweden. The target lithology consisted of limestone and black unconsolidated shale overlaying a Precambrian crystalline basement. The Precambrian basement is uranium‐rich, and the black shale is both uranium‐ and organic‐rich. This circumstance makes Lockne a good candidate for testing the occurrence of U‐Th‐rich bitumen nodules in an impact structure setting. U‐Th‐rich bitumen nodules are formed through irradiation; hence the increase in the complexity of organic matter by a radioactive (uranium‐ and thorium‐rich) mineral phase. U‐Th‐rich bitumen nodules were detected in crystalline impact breccia and resurge deposits from the impact structure, but samples of non‐impact‐affected rocks from outside the impact structure do not contain any U‐Th‐rich bitumen nodules. This implies that in the Lockne impact structure, the nodules are associated with impact‐related processes. U‐Th‐rich bitumen nodules occur throughout the geological record and are not restricted to an impact structure setting, but our studies at Lockne show that this process of irradiation can readily occur in impact structures where fracturing of rocks and a post‐impact hydrothermal system enhances fluid circulation. The irradiation of organic matter by radioactive minerals has previously been proposed as a process for concentration of carbon on the early Earth. Impact structures are suggested as sites for prebiotic chemistry and primitive evolution, and irradiation by radioactive minerals could be an important mechanism for carbon concentration at impact sites.     

Interpretation of Statistical Flare Data using Magnetic Reconnection Models

The ability of magnetic reconnection solutions to explain statistical flare data is discussed. It is assumed that flares occur at well-defined, isolated sites within an active region, determined by the null points and separators of the coronal magnetic field (Craig, 2001). Statistical flare observations then derive from a multiplicity of independent sites, flaring in parallel, that produce events of widely varying output (Wheatland, 2002). Given that the `separator length' at an individual site controls the event frequency and the mean energy release, it is shown that the observed frequency-energy spectrum N(E)can be inverted to yield a source function that relates directly to the distribution of separator lengths. It is also pointed out that, under the parallel flaring model, inferred waiting-time distributions are naturally interpreted as a superposition of individual point processes. Only a modest number of flaring separators is required to mimic a Poisson process.     

Trace metal contamination of Beaufort's Dyke, North Channel, Irish Sea: a legacy of ordnance disposal

Beaufort’s Dyke is a disused ordnance disposal ground within the North Channel of the Irish Sea. Over 1 million tonnes of ordnance were disposed of in the dyke over a 40 year period representing a substantial volume of trace metal pollutants introduced to the seabed. Utilising particle transport modelling software we simulated the potential transport of metal particles from Beaufort’s Dyke over a 3 month period. This demonstrated that Beaufort’s Dyke has the potential to act as a source for trace metal contamination to areas beyond the submarine valley. Trace metal analysis of sediments from the Dyke and surrounding National Marine Monitoring Programme areas demonstrate that the Dyke is not the most contaminated site in the region. Particle transport modelling enables the transport pathways of trace metal contaminants to be predicted. Implementation of the technique in other munitions disposal grounds will provide valuable information for the selection of monitoring stations.