Geological and geotechnical aspects of underground coal mining methods within Australia

About one quarter of the coal produced in Australia is by underground mining methods. The most commonly used underground coal mining methods in Australia are longwall, and room and pillar. This paper provides a detailed review of the two methods, including their advantages and disadvantages, the major geotechnical and operational issues, and the factors that need to be considered regarding their choice, including the varying geological and geotechnical conditions suited to a particular method. Factors and issues such as capital cost, productivity, recovery, versatility and mine safety associated with the two methods are discussed and compared. The major advantages of the longwall mining method include its suitability for mining at greater depth, higher recovery, and higher production rate compared to room and pillar. The main disadvantages of the room and pillar method are the higher risks of roof and pillar collapse, higher capital costs incurred as well as lower recovery rate.     

Intraspecific Variation in Growth of Marsh Macrophytes in Response to Salinity and Soil Type: Implications for Wetland Restoration

Genetic diversity within plant populations can influence plant community structure along environmental gradients. In wetland habitats, salinity and soil type are factors that can vary along gradients and therefore affect plant growth. To test for intraspecific growth variation in response to these factors, a greenhouse study was conducted using common plants that occur in northern Gulf of Mexico brackish and salt marshes. Individual plants of Distichlis spicata, Phragmites australis, Schoenoplectus californicus, and Schoenoplectus robustus were collected from several locations along the coast in Louisiana, USA. Plant identity, based on collection location, was used as a measure of intraspecific variability. Prepared soil mixtures were organic, silt, or clay, and salinity treatments were 0 or 18 psu. Significant intraspecific variation in stem number, total stem height, or biomass was found in all species. Within species, response to soil type varied, but increased salinity significantly decreased growth in all individuals. Findings indicate that inclusion of multiple genets within species is an important consideration for marsh restoration projects that include vegetation plantings. This strategy will facilitate establishment of plant communities that have the flexibility to adapt to changing environmental conditions and, therefore, are capable of persisting over time.     

Automatic calibration tool for river models based on the MHYSER software

Due to their complex nature, river models require extensive calibration in order to achieve reliable model predictions. Manually fitting the numerous parameters included in this procedure can be a laborious and repetitive process. This paper presents a new instrument, developed specifically for the automatic calibration of river models based on the software MHYSER. The instrument is completely autonomous and returns the model with the parameter values giving rise to the smallest difference between the model-generated observations and the measured observations. It utilises the software PEST to fit continuous calibration parameters and exceeds the program’s capabilities in order to also fit discontinuous calibration parameters. Testing of the instrument is accomplished using three models, one of which was developed during a study on the dynamics of sediments on the Romaine River, situated in the Eastern region of the Province of Quebec.     

Geochemistry of clastic sediments from Sargur supracrustals and Bababudan group,Karnataka: Implications on Archaean Proterozoic Boundary

The sediments from three stratigraphic levels in the Bababudan schist belt of Dharwar craton exhibit great diversity in major, trace and rare earth element (REE) geochemistry and thus interpreted to represent significant compositional variation in the source rocks. Detailed geological and geochemical studies have been carried out on clastic rocks constituting the Archaean Sargur supracrustals and the Bababudan belt of Dharwar craton (DC), southern India for understanding the geochemical characteristics and to define the Archaean-Proterozoic Boundary (APB/QPC) in southern India. There is significant contrast in the geochemical signatures for the sediments from these stratigraphic levles. The Sargur enclave population is characterised by slight LREE enrichment with (La/Sm)_N ranging from 1.45 to 3.58, almost flat HREE with (Gd/Yb)_N ranging from 0.65 to 1.29 with Eu/Eu* ranging from 0.49 to 0.91 suggesting mafic-ultramafic source rocks in the provenance. On the other hand, the Post QPC (PQPC) rocks are characterised by LREE enrichment with (La/Sm)_N ranging from 2.66 to 7.07, nearly flat HREE with (Gd/Yb)_N ranging from 0.58 to 0.95 and significant depletion of Eu with Eu/Eu* ranging from 0.34 to 0.85, indicating felsic province in the source area. The conglomerates and quartzites representing the QPC are showing mixed nature of these, reflecting the transitional character in depositional environment. Increase in abundance of REE, K₂O/Na₂O, Th/Sc, La/Sc, Th/U, Hf/Ta and Zr/Y ratios are characteristic of the QPC. The PQPC sediments are enriched in Th, U and HFSE like Hf, Nb, Zr and Y, and depleted in Co and Eu than their older counterparts. These geochemical signatures signify the dominance of mafic-ultramafic rocks in the source area for Sargur rocks and the existence of granite-granodiorite for PQPC clastics. Thus, the unconformity related oligomictic quartz pebble conglomerates (QPC) and quartzites at the base of Bababudan Group resembling the QPC of Witswaterand, South Africa signifies that a stable continental crust had already developed in southern India prior to ∼3.0Ga.     

Surface Water Metabolism Potential in a Tropical Estuary,Hilo Bay,Hawai’i,USA, During Storm and Non-storm Conditions

Surface water gross primary production potential (pGPP), respiration (RESP), metabolism potential (pMET), and CO₂ fluxes in Hilo Bay, Hawai’i, USA, were examined along two river plumes during storm (high-flow) and non-storm (low-flow) conditions. Significant differences in pGPP, RESP, and pMET were found between low- and high-flow conditions, with lowest rates of all processes occurring during high-flow conditions. CO₂ fluxes were influenced by metabolic processes at all but one site, with the bay’s surface waters being autotrophic and a sink for atmospheric CO₂ during low-flow conditions and less autotrophic and a source of atmospheric CO₂ during high-flow conditions. Significant differences in pMET were found between the two river plumes during low-flow conditions at spatial scales of 1.5 km; however, no differences between river plumes were found during high-flow conditions. Our study suggests that an increase in storms associated with global climate change could impact surface water metabolic dynamics of tropical estuaries.     

Seismic hazard assessment for Mymensingh,Bangladesh

Mymensingh municipality lies in one of the most earthquake-prone areas of Bangladesh. The town was completely destroyed during the Great Indian Earthquake of 12 June 1897, for which the surface-wave magnitude was 8.1. In this study the 1897 Great Indian Earthquake was used as a scenario event for developing seismic microzonation maps for Mymensingh. For microzonation purposes SPT data from 87 boreholes were collected from different relevant organizations. To verify those data ten boreholes of depth up to 30 m were drilled. Intensity values obtained for different events were calibrated against attenuation laws to check applicability to the study area. Vibration characteristics at diverse points of the study area were estimated by employing the one-dimensional wave-propagation software SHAKE. SHAKE discretizes the soil profile into several layers and uses an iterative technique to represent the non-linear behavior of the soil by adjusting the material properties at each iteration step. The required input information includes depth, shear wave velocity, damping factor, and unit weight of each soil layer. The liquefaction resistance factor and the resulting liquefaction potential were estimated to quantify the severity of liquefaction. Quantification of secondary site effects and the weighting scheme for combining the various seismic hazards were heuristic, based on judgment and expert opinion.     

Prosperity and the New Economy in Canada’s major city regions

Canada’s three large city regions—Montréal, Toronto and Vancouver—have been relatively successful in retaining their Manufacturing bases, while at the same time adding substantial numbers of New Economy job opportunities. Deindustrialization appears to have occurred primarily in the Montréal CMA (Census Metropolitan Area) and in some smaller communities where motor vehicle manufacturing was significant. Growth in New Economy jobs has occurred in the larger CMAs; the smaller urban areas have had little success in attracting these jobs. For the most part, these trends appear to be path dependent: prosperous communities with substantial proportions of New Economy jobs are likely to remain prosperous and to attract more such jobs. The lack of significant correlation between Economic Health and the presence of immigrants, same sex couples, performing and visual artists suggests that local economic development strategies based on these factors may have limited success.     

Water quality and relationship between superficial and ground water in Rome (Aniene River basin,central Italy)

Chemical, physical, and biological features of streams and ground water of the North-Eastern area of Rome are jointly analyzed in order to assess the status of water resources. Ground water was investigated with classical survey methods (pH, temperature, and electric conductivity). Microbiological pollution, faunal composition, and stream surrounding area conditions of surface waters were studied, in order to quantify the residual value of these ecosystems from both a human and an environmental point of view. Results show a general impairment of the system and the comparison between superficial waters and shallow ground waters makes it possible to detect the presence of a connection between the two levels. This relationship occurs as an exchange from superficial waters (streams and rivers) to the shallow aquifers. Where superficial waters are contaminated, as in the Tor Sapienza stream, pollutants move to the shallow aquifers too, due to the decreased pressure of the over-exploited aquifer. Moreover, uncontrolled drilling activity, diffused in urban areas, makes it possible the connection between shallow and deep ground water. Notwithstanding this, the mixing between superficial and deep ground water system in Rome is not very widespread and, apparently, limited to restricted areas.     

Analysis of the Chesapeake Bay Hypoxia Regime Shift: Insights from Two Simple Mechanistic Models

Recent studies of Chesapeake Bay hypoxia suggest higher susceptibility to hypoxia in years after the 1980s. We used two simple mechanistic models and Bayesian estimation of their parameters and prediction uncertainty to explore the nature of this regime shift. Model estimates show increasing nutrient conversion efficiency since the 1980s, with lower DO concentrations and large hypoxic volumes as a result. In earlier work, we suggested a 35% reduction from the average 1980–1990 total nitrogen load would restore the Bay to hypoxic volumes of the 1950s–1970s. With Bayesian inference, our model indicates that, if the physical and biogeochemical processes prior to the 1980s resume, the 35% reduction would result in hypoxic volume averaging 2.7 km³ in a typical year, below the average hypoxic volume of 1950s–1970s. However, if the post-1980 processes persist the 35% reduction would result in much higher hypoxic volume averaging 6.0 km³. Load reductions recommended in the 2003 agreement will likely meet dissolved oxygen attainment goals if the Bay functions as it did prior to the 1980s; however, it may not reach those goals if current processes prevail.     

Heavy metal and anionic contamination in the water and sediments in Al-Mujib reservoir,central Jordan

Sixty-five sediment samples and 25 water samples were collected from Al-Mujib reservoir, central Jordan, in order to investigate the heavy metal and ionic contamination assessment. Therefore, to achieve this aim, water and sediment samples were collected during winter and summer seasons (2007) from Al-Mujib reservoir and the areas surrounding it. The study shows that there are elevated levels of SO₄ ²⁻, Cl⁻ and Na⁺ in reservoir water, which might originate from anthropogenic activities in the reservoir catchment area. In addition, the reservoir water has higher total hardness (TH) values together with high Ca and Mg contents. This might be attributed to pH of reservoir water and the nature of the rocks exposed in the catchment area. The average levels of heavy metals in reservoir sediments are Fe = 14,888.1, Cu = 17.8, Zn = 88.6, Ni = 38.7, Cd = 4.4, Mn = 337.9 and Pb = 6.1 mg/kg, which are lower than that observed in Wadi Al-Arab reservoir, northern Jordan. The values of enrichment factor are Cd = 35.5, Ni = 3.02, Zn = 2.54, Cu = 1.26, Mn = 1.2 and Pb = 0.57; these values indicate that heavy metals in sediments of Al-Mujeb reservoir have a different anthropogenic incrimination inputs. The study showed that the sediments are polluted with Cd, relatively contaminated with Ni and Zn and uncontaminated with respect to Mn, Pb and Cu.